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The increasing use of aluminum alloys in various industries necessitates the development of improved welding techniques. This study investigates the application of ultrasonic vibration in tungsten inert gas (TIG) welding of aluminum 5083 sheets. The results indicate that ultrasonic vibration significantly improves weld penetration depth and width, refines the microstructure by increasing the proportion of equiaxed grains, and enhances the mechanical properties of the welds, including tensile strength, and hardness. These findings demonstrate the potential of ultrasonic-assisted TIG (U-TIG) welding to optimize weld quality and performance in aluminum 5083 alloys. Finite element modeling of TIG and U-TIG welding provided heat distribution and temperature history, essential for analyzing microstructural observations and mechanical test results. Notably, previous U-TIG finite element modeling was inadequate, but this research offers a more accurate approach. The temperature results from the finite element model showed excellent agreement with reference data. The welding area was divided into three zones: fusion zone (FZ), partially melted zone (PMAZ), and heat affected zone (HAZ). Experimentally, TIG welded samples had FZ width and depth, and PMAZ width of 2.2, 1.45, and 0.4 mm, respectively, while U-TIG welding samples measured 1.95, 1.85, and 0.4 mm, respectively. Finite element modeling determined these zones to be 2.1, 1.5, and 0.45 mm for TIG welding, and 1.9, 1.9, and 0.4 mm for U-TIG welding, respectively. The mechanism of grain refinement was identified as dendrite fragmentation and heterogeneous nucleation. [ABSTRACT FROM AUTHOR]

Ultra-precision lapping is widely used in the mass production of various types of high-precision bearing rollers. The lapping quality of the bearing rollers is greatly influenced by the wear behavior of the lapping tool. In this context, this study presents a computational analysis utilizing the Archard wear law and finite element modeling (FEM) to examine the wear behavior of the lapping tool. A wear simulation approach based on the Archard wear law is implemented in the ABAQUS software that works in association with the Arbitrary Lagrange Eulerian adaptive mesh technique and the Umeshmotion subroutine. Initially, the parameters of the Archard wear model are investigated experimentally using the free abrasive lapping device. A numerical 3D finite element model is established in order to obtain the contact pressure distribution, wear volume, wear depth, and wear profile of the lapping tool. The mesh within the wear region of the finite element model is allowed to move independently from the material to maintain the high-quality mesh for simulating material removal. The simulation efficiency is improved by the incorporation of an acceleration factor. Ultimately, the lapping tool is subjected to an examination regarding the contact pressure distribution, wear depth, and alterations in the wear profile. The wear simulation results of the lapping tool can provide significant insights for future run-in and machining processes. [ABSTRACT FROM AUTHOR]

The toolpath based on the support tool adjustment to the local normal of the master tool has a substantial effect on the final component quality in double-sided incremental forming (DSIF). Two novel toolpaths based on two new support tool positions to the master tool were investigated for their effects on forming quality. These toolpaths were based on adjusting and maintaining the support tool at a specific gap (ϕ = 7.75° and 15.5°) from the local normal of the master tools in the meridional orientation in the direction of the already formed part without pneumatic-assisted support tool. The adjustment of the support tool at ϕ = 7.75° deforms the sheet based on the sheet compression and reverse bending, whereas support tool adjustment at ϕ = 15.5° deforms the sheet based on reverse bending. The two new toolpaths were compared to each other and to a normal DSIF toolpath based on experimental results for geometric precision, surface finish, processing time, and component sheet thickness variation. Simulation results for these toolpaths were also evaluated to support the experimental results and understand the process mechanism. The three main challenges posed by the DSIF process, geometric precision, sheet thickness distribution, and surface roughness, were improved up to 30%, 1.07%, and 21.81%, respectively, using the new toolpaths without compromising the forming time. The combined reverse bending and compression improved the forming quality effectively compared to only reverse bending or compression. These toolpath benefits are the no additional requirements for additional equipment, reducing capital and operational cost. [ABSTRACT FROM AUTHOR]

Nomex honeycomb composite core (NHC) is characterized by thin walls and complex hexagonal cells, giving it specific characteristics. However, this particularity generates significant challenges during its shaping, requiring the use of cutting tools of the particular geometry. In this study, experimental tests were conducted on the milling of NHC structure assisted by RUM technology using the UCSB cutting tool which is a toothed milling cutter. However, the experimental procedure fails to follow the cutting process, which complicates the visualization of the chip formation process due to the rapid movement of the cutting tool and the inaccessibility of the surface between the part/tool. Therefore, in order to effectively follow chip formation, a 3D numerical approach to the milling process of the NHC structure, using RUM technology, is developed using Abaqus Explicit software. On the basis of this model, the study focused on the components of the cutting force, the quality of the machined surface, and the accumulation of chips in front of the cutting tool. The numerical simulation results corroborate the experimental test findings, demonstrating the effectiveness of RUM technology in reducing cutting force components by up to 63%. An exhaustive analysis of the impact of the feed component Fy on the quality of the surface obtained was carried out, highlighting that the quality of the generated surface improves when the values of this component are low. In addition, the effectiveness of ultrasonic vibrations in reducing the accumulation of chips in front of the cutting tool is particularly accentuated, especially when large amplitudes are involved. Thus, the simulated results complemented the experimental results by offering coherent theoretical explanations. [ABSTRACT FROM AUTHOR]

Finite element (FE) modeling of tailor welded blanks (TWBs) is a complex phenomenon compared to FE modeling of monolithic sheets due to the change of mechanical properties caused by the welding process. This complexity involves modeling different zones generated due to the heat effect. Research on the formability of steel TWBs with dissimilar thicknesses and strength produced by manual tungsten inert gas (TIG) welding technique and formed by single point incremental forming (SPIF) involving base sheets, weld nugget (WN), and heat affected zone (HAZ) is presented, numerically. The materials selected for the study included deep drawing quality (DDQ) steel (DC06) and stainless steel (SS) (AISI 201). Variable wall angle truncated pyramid was used as test geometry, and FE software Abaqus (dynamic explicit solver) was used for the analysis. Thickness profiles and state of stress and strain in both the cases of thickness and strength differential were analyzed. A decrease in thickness was observed at the corners in both cases. However, this decrease was more prominent in the case of strength differential. The symmetry of the pattern on both sides with minimum and maximum values of stress towards the thinner side was observed in the case of thickness differential. Variation in stress was more prominent towards the side of high-strength material along maximum value in the case of strength differential. Equivalent plastic strain observed was more linear and higher towards the sides of thicker sheet and material having less strength in the case of thickness differential and strength differential, respectively. Research investigations may be applied in a similar fashion for the precise study of formability characteristics of various kinds of TWBs being used in multiple industries including automotive, vessel, and medical. [ABSTRACT FROM AUTHOR]

This investigation aims to propose a novel framework for designing and manufacturing cranial prostheses through incremental sheet metal forming (ISF). First, the three-dimensional models of the defective crania and the prosthesis were constructed from the CT data. Then, to verify the formability of the prosthesis model, a method for testing the mesh sheet's incremental forming limit (IFL) was proposed with a variable angle cone model. The angle between the normal vector of the fracture point and the Z-axis calculated the IFL. The tests showed that the method could realize the testing of the IFL of the mesh sheet with the reduction of processing time and cost. In addition, finite element modeling and experimental trials were used to evaluate the ISF process of the prosthesis, including thickness distribution and geometric accuracy. The results showed that the incremental forming can form prosthesis samples with high precision, while the thickness distribution is relatively uniform without excessive thinning. Finally, the obtained prosthesis sample was practically assembled with the cranial defect model to verify the fitting effect and feasibility of the prosthesis formed by the ISF process. [ABSTRACT FROM AUTHOR]

In this research, sustainable machining of the aluminum alloy (Al 6061-T6) is considered. Aluminum is a durable and infinitely recyclable material as well as light in density, causing no environmental effects in comparison with other materials including steel or plastic. Currently, due to a lack of understanding and inefficient application of modern sustainable manufacturing tools and technologies, around 20% of the investment made in metal cutting tools was reported to have been wasted. The constitutive law describing the thermo-mechanical behavior of workpiece material significantly affects the success of any finite element modeling (FEM). Different values of Johnson–Cook (JC) material constants determined through different methods are found in the literature which consequently affects the predicted results. Current research used an inverse methodology to determine the JC material constants and compare them with published literature. The proposed JC material model was then verified through orthogonal machining of Al 6061-T6 alloy at different machining conditions. Cutting forces at high-speed machining were found to decrease remarkably due to adiabatic heating conditions and short contact time between the workpiece and tool material. The JC material constants determined through the current approach produced better predictions of the cutting forces at high-speed machining conditions suitable for sustainable manufacturing. [ABSTRACT FROM AUTHOR]

In this study, the joining of 6061-T6 aluminum alloy and DP590 steel using a M42 steel rivet via friction riveting technique is investigated. The surface morphology and microstructure characterization reveal the formation of an anchor zone that imparts mechanical interlock as well as the formation of metallurgical bonds at the interface of aluminum and steel. A combination of interlocking and bonding results in the achievement of a high load-carrying capacity of 5.7 kN during lap shear testing at room temperature. A finite element-based computational model was developed which accurately predicted the lap shear response of the joint. The model revealed that the metallurgical bond formed during fric-riveting adds 39% peak load strength to the joint. An extensive microstructural investigation, post-lap-shear fractography, and the modeling results, together provided insights on the joint failure mechanism. This study highlights that friction riveting is a promising method for aluminum-to-steel dissimilar joining, which is important for lighweighing automotive vehicles for energy efficiency. [ABSTRACT FROM AUTHOR]

Forging is a widely used manufacturing process, and its design and modeling are important to reducing production costs, increasing die lifespan, and improving the mechanical properties of the final product. In this study, the forging process of a connecting rod was modeled using 3D coupled Eulerian Lagrangian (CEL) analysis by FEM. The methodology adopted achieved to determine a preform geometry that reduces final flash and forging load, while ensuring complete filling of the stamp. Starting from the final geometry, the final die was designed. After the first result for an approximately 27% of flash, the material distribution was adjusted decreasing it at the regions where the flash was too large. After an iterative method was applied to determine better preform, a proposal was found that reduced forging force by approximately 42% and the percentage of flash volume by 64% in comparison with the first one. A final flash of about 10% is considered a good objective to reach. Lower values may cause many iterations, not a significant difference in forging loads, the risk of an unfilled die, and complex preform geometries. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the mechanical behavior of corrugated board boxes, focusing attention on the strength that the boxes are able to offer in compression under stacking conditions. A preliminary design of the corrugated cardboard structures starting from the definition of each individual layer, namely the outer liners and the innermost flute, was carried out. For this purpose, three distinct types of corrugated board structures that include flutes with different characteristics, namely the high wave (C), the medium wave (B), and even the micro-wave (E), were comparatively evaluated. More specifically, the comparison is able to show the potential of the micro-wave which would eventually allow a significant saving of cellulose in the fabrication process of the boxes, thus reducing the manufacturing costs and causing a lower environmental footprint. First, experimental tests were carried out to determine the mechanical properties of the different layers of the corrugated board structures. Tensile tests were performed on samples extracted from the paper reels used as base material for the manufacturing of the liners and flutes. Instead, the edge crush test (ECT) and box compression test (BCT) were directly performed on the corrugated cardboard structures. Secondly, a parametric finite element (FE) model to allow, on a comparative basis, the study of the mechanical response of the three different types of corrugated cardboard structures was developed. Lastly, a comparison between the available experimental results and the outputs of the FE model was carried out, with the same model being also adapted to evaluate additional structures where the E micro-wave was usefully combined with the B or C wave in a double-wave configuration. [ABSTRACT FROM AUTHOR]

In this work, the deposition of high-density polyethylene (HDPE) and polyurethane (PU) particles on polymeric substrates was studied using the finite element analysis software ABAQUS Explicit 2018 at impact velocities ranging between 100 and 500 m/s and temperatures between 20 and 100 °C. The effect of these parameter variations on the particle impact dynamics was quantified by tracking the applied stress, particle temperature, plastic deformation, strain, rebound velocity, and kinetic energy dissipation. The trends observed through variation of these parameters were compared to the experimentally observed window of deposition, which provided important insights into the deposition mechanisms in the cold spray process. The results of the simulations in the present work agreed well with experiments as the lower rebound velocity was associated with the higher deposition efficiency in the cold spray process and vice versa. The results also manifested the importance of the peening effect of the multiple particle collision in the cold spray process, where all of the simulated models showed that the single particle rebounded from the substrate without adhering to it. The peening effect was suggested to play a role in this case because it was eliminated in the single-particle impact simulation of this work. [ABSTRACT FROM AUTHOR]

In this paper, 2205 DSS sheets with equal amounts of ferrite and austenite joined by GTAW, GMAW1 (equal welding speed with hybrid welding), GMAW2 (equal input heat with hybrid welding), and hybrid GTAW-GMAW. Then, heat distribution, maximum temperature, and cooling time during welding obtained from finite element simulation and the results were validated. Finally, the effect of input heat, cooling time, and welding method condition on quality and final microstructure of the joint were investigated. In addition to having a very good appearance, hybrid welding also has the highest ratio of weld depth to weld width. Also, due to the effect of using two arcs, on a same input, it has a lower maximum temperature comparing GMAW2. The average cooling time in hybrid welding is 26.5 s, which is less than GMAW2 and more than GTAW and GMAW1, and this has caused the weld metal microstructure to have approximately equal amounts of ferrite and austenite (48% austenite). This has caused the hardness of the weld zone in hybrid welding to be higher than the hardness of GMAW2 and close to the hardness of GTAW. Microstructural studies also revealed that the main morphology of austenite in fusion zone of hybrid welding is Widmanstatten. The size of ferrite grains in HAZ for hybrid welding is 204.3 μm, which is smaller than GMAW2 and larger than GTAW and GMAW1. The reason for this is the shorter cooling time in hybrid welding compared to welding GMAW2. [ABSTRACT FROM AUTHOR]

Aluminum honeycomb structures have been frequently used in many industrial applications, especially in aerospace and aeronautics, due to their high strength and stiffness to weight ratio. The machining quality of aluminum honeycomb structures is generally related to plastic deformation of the walls forming the honeycomb structure and burrs. Consequently, the use of this type of structure requires specific machining operations and special tools. In order to carry out in-depth studies on the milling of aluminum honeycombs, a 3D finite element model was developed with the help of Abaqus/Explicit software. The model thus developed is validated with several experimental tests and for different machining conditions. Based on the developed model, the relationship between the cutting forces and the friction coefficient between the cutting tool and the honeycomb during the cutting process is studied. The main objective of this work is to highlight the effect of physical and geometrical parameters during the milling of aluminum honeycomb structures on cutting forces, surface quality generated, chip size, and material accumulation in front of the cutting tool. The comparison between the simulated results and the experimental results indicates that the developed numerical model is in good agreement with the experimental reality. [ABSTRACT FROM AUTHOR]

Wide applications of carbon fiber–reinforced polymer (CFRP) components in modern manufacturing enterprises have led to significant demand in the secondary machining processes. However, the machining surface quality characterization and its impact on the material's mechanical performance are not fully investigated. In this paper, a quantitative characterization method is proposed for assessing CFRP milling surface quality by combining SEM and image segmentation techniques, which was evaluated using three indices, namely, surface roughness, surface void fraction, and depth of affected zone. Finite element simulation and experiments about side milling of unidirectional CFRP with 90° fiber orientation were conducted to investigate the effects of milling conditions on the resulting surface quality indices. It was found that feed rate and cutting edge radius are two dominant factors that affect the surface void and the depth of affected zone, and the down-milling style is accompanied by greater machining damages due to the difference fiber cutting angle compared with up-milling. Meanwhile, the influence of the above three indices on the tensile and compressive strength of CFRP specimen was also obtained. It is concluded that the depth of the affected zone has a more significant effect on the strength degradation of machined CFRP materials. [ABSTRACT FROM AUTHOR]

Machining is one of the more widely used manufacturing processes in the industry, for this reason, several studies have focused on predicting the effect of variables related to it. In this work, the effect of the equivalent plastic displacement on the orthogonal cutting process, using coupled Lagrangian–Eulerian (CEL) analysis was studied. The workpiece was considered Eulerian solid material to simulate its interaction with the cutting tool and thus, predict material separation and chip morphology. In the present model, the chip morphology was evaluated in terms of the equivalent plastic displacement, segmented chip formation was achieved without the necessity to apply a method of mesh separation and undeleting elements during the calculation solution, which represents an important advantage over the purely Lagrangian method. Additionally, the cutting forces, contact length, angle of the cutting plane, as well as stress, strain, and temperature distribution were obtained. [ABSTRACT FROM AUTHOR]

As a kind of interference rivet with compensation at the head, the reduced countersunk head half-crown rivet can achieve long life sealing riveting for airplane types or engine rooms with special requirements for sealing and fatigue performance. In the present study, a quartered three-dimensional finite element model was created to simulate the riveting process. The FE model was validated from the perspective of driven head dimensions and interferences based on the experiment results. The effects of feed displacement of rivet dies, feed speed ratio of rivet dies, pre-feed displacement of upper rivet die and countersunk depth on the forming quality of riveted lap joints were systematically studied. The results showed that the average interference increased with the increase of the feed displacement of rivet dies, while it decreased with the increase of the feed speed ratio of rivet dies and pre-feed displacement of upper rivet die. The countersunk depth of 1.05 mm is the transition depth for the rivet studied in this paper. In addition, the results of combined effect of feed speed ratio of rivet dies and pre-feed displacement of upper rivet die on the forming quality proved that the influence laws of single parameter were no longer suited for the scenario of combined effect of multiple riveting parameters. This paper can provide scientific and normative guidance for the applications of reduced countersunk head half-crown rivet in engineering structure. [ABSTRACT FROM AUTHOR]

Residual stresses and strains, distortions, heat-affected zone (HAZ), grain size changes and hardness variation during gas metal arc welding (GMAW), are fundamental aspects to study and control during welding processes. For this reason, numerical simulations of the welding processes represent the more frequently used tool to better analyse the several aspects characterizing this joining process with the aim to reduce lead time and production costs. In the present study, an uncoupled 3D thermo-mechanical analysis was carried out by two commercial finite element method (FEM) software to model an experimental single bead GMAW of AISI 441 at different processes set-up. The experimental HAZ and measured temperatures were used to calibrate the heat source of both the used numerical codes, then a validation phase was done to test the robustness of the two developed analytical procedures. One software was used to predict the residual stresses and strains and the distortions of the welded components, while in the second software, a user routine was implemented, including a physical based model and the Hall-Petch (H-P) equation, to predict grain size change and hardness evolution, respectively. The results demonstrate that the predicted mechanical and microstructural aspects agree with those experimentally found showing the reliability of the two codes in predicting the thermal phenomena characterizing the HAZ during the analysed welding process. [ABSTRACT FROM AUTHOR]

Residual stresses affect the service life and cause the deformation of machined parts. Therefore, the study on the development of residual stresses during machining operation is very important. For this, analytical and numerical models have been developed to predict the residual stresses for single-step machining operation. However, the parts are usually machined with a serial of production processes. A numerical model for predicting residual stress in sequential side milling GH4169, considering initial stress, was proposed in this research. The initial residual stress distribution due to previous-step milling was considered in the proposed model. It was assumed that this initial residual stress value changed with the depth from the machined surface, while the residual stress on the identical horizontal plane was assumed with uniform distribution. The proposed numerical simulation model could predict the stress value of the machined surface, the stress value of the compression valley, and the residual stress distribution in the depth direction beneath the machined surface with high accuracy. Experimental investigations of sequential side milling GH4169 were conducted and the generated residual stresses were measured. The distribution trend and influence rule of residual stress between two sequential milling steps were analyzed. The residual stress distribution beneath the surface showed a spoon-shaped pattern. The thickness of the residual stress influence layer (RSIL) after the current milling step was affected by the depth of cut and the RSIL thickness of the previous milling step. The numerical model could predict the thickness of RSIL and optimize the depth of cut in sequential side milling. [ABSTRACT FROM AUTHOR]

In last decades, several numerical models of the keyhole laser welding process were developed in order to simulate the joining process. Most of them are sophisticated multiphase numerical models tempting to include all the several different physical phenomena involved. However, less computationally expensive thermo-mechanical models that are capable of satisfactorily simulating the process were developed as well. Among them, a moving volumetric equivalent heat source, whose dimensions are calibrated on experimental melt pool geometries, can estimate some aspects of the process using a finite element method (FEM) modeling with no need to consider fluid flows. In this work, a double-conical volumetric heat source is used to arrange a combination of two half hourglass-like shapes with different dimensions each other. This particular arrangement aims to properly assess the laser joining of a tailor welded blank (TWB) even in case of butt joint between sheets of different thicknesses. Experiments of TWBs made of 22MnB5 steel sheets were conducted in both equal and different thickness configurations in order to validate the proposed model. The results show that the model can estimate in a satisfactory way the shape and dimensions of the fused zone in case of TWB made of sheets with different thickness. [ABSTRACT FROM AUTHOR]

A novel and effective method to fabricate the bimetallic composite tube was proposed using a KOBO extrusion technique with an oscillating die. Compared with the traditional extrusion, KOBO extrusion enabled to induce high-frequency deformation path changes under the combined action of extrusion force and torsion torque. The numerical simulations of KOBO extrusion were conducted at extrusion velocities of 1, 2, 3, and 4 mm·s−1 and rotation frequencies of 2.5, 5, 8, and 10 Hz. The thickness uniformity coefficient and ratio of runoff were newly proposed as two indexes to evaluate the dimensional uniformity and stability of extruded bimetallic composite tubes. The results showed that KOBO extrusion had obvious advantages in reducing the extrusion load, narrowing the deformation zone, and simultaneously increasing the forming temperature. Both layers of extruded tube by the KOBO extrusion had more even thickness with lower thickness uniformity coefficients. The ratio of runoff for extruded tube was very close to its initial value of billet, which indicated that the KOBO extrusion enabled to form bimetallic composite tube with presumptive stable mechanical property. By comprehensive analysis of the impact of rotation frequency and extrusion velocity on reducing the total power consumption and increasing the power conversion parameter, it was recommended that KOBO extrusion selected a lower rotation frequency and a higher extrusion velocity under the premise of guaranteeing forming quality of the bimetal composite tube. [ABSTRACT FROM AUTHOR]

The analysis of the stress-strain state of the closed rope elements under axial tension and torsion was carried out by the finite element method using the licensed software package SIMULIA/Abaqus. The closed rope consists of an outer layer of Z-profile wires, a subsurface layer of alternating round and H-profile wires, an intermediate layer, and a core of the structure 1 + 7 + 7/7 + 14 of round wires. Modeling made it possible to determine the values of the axial force P, the torque M, the relative elongation ε, and the relative angle of torsion θ of the rope sample at the given values of the axial displacement and the rotation angle the cross-section. The results of the analytical calculation of the stress-strain state of a spiral rope using traditional approaches were compared with those obtained in the course of computer finite element modeling. The results of modeling the rope deformation under tension were verified by experimental data obtained by stretching the rope sample on a universal horizontal hydraulic test machine LabTest 6.2000N.7. The results of computer modeling of the rope pure tension correlate well with the results of the calculation by the method of M.F. Glushko, which more accurately takes into account the real construction of the ropes. Computer simulation of the stress-strain state of the closed rope elements made it possible to determine the contact stresses between shaped wires in layers and between layers at different values of the gap between shaped wires; therefore, it can be used to optimize the gaps. Computer simulation of the stress-strain state of the rope elements of a closed structure makes it possible to assess the consistency of the layers narrowing during axial tension by analyzing the contact stresses between adjacent wires in the cross-section of the rope. [ABSTRACT FROM AUTHOR]

As-built metallic parts manufactured by the laser powder bed fusion (LPBF) process are usually associated with distortions and high residual stresses due to the high thermal gradients and cycles during the process. Finite element modeling (FEM) could be helpful in simulating the build process and predicting the thermally induced residual stresses and parts' distortion during or after the process, or after the support structure removal. FEM is, however, computationally expensive without simplifying the boundary conditions and model assumptions. This paper addresses the thermomechanical modeling of the LPBF process in two aspects. Firstly, the effects of model assumptions such as the yield strength, material properties' temperature dependency, and layer thickness are investigated using 2D models. Secondly, a framework that addressed the computational expense of this modeling problem from the meshing perspective is proposed. The study employed parts from different materials to highlight the importance of model assumptions and demonstrate the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

A coupled thermomechanical finite element analysis is performed in order to simulate orthogonal cutting of normalized AISI 9310. Damage parameters are optimized to define the behavior of the material subjected to orthogonal cutting. AISI 1045, AISI 4140, and A2024-T351 are selected as precursors to validating the present finite element approach for orthogonal cutting of normalized AISI 9310. The numerical results obtained in this study include the average cutting force, residual stresses and strains, chip morphology, and tool temperature. These results are validated for each material with experimental results found in literature. The current study optimizes the Johnson–Cook damage parameters for steel materials in order to capture physical chip morphology. A correlation analysis is then performed using the validated finite element model for the AISI 9310 material to better understand the effect of specific input parameters such as the damage parameters, coefficient of friction, fracture energy, heat generation fractions and tool velocity on output results such as stresses and strains in the workpiece, chip thickness ratio and tool temperature. This analysis provides input-output relations for a physically reasonable range of input parameters and supports that the damage parameters, coefficient of friction, and fracture energy have a very strong influence on the residual stresses and strains, and the chip morphology. The coefficient of friction has a strong influence of tool temperature. Correlation analysis results can help manufacturers in understanding the nature of residual stresses and distortion, and in choosing optimized process parameters suitable for and applicable to the specific workpiece material. Tool wear that is observed in actual cutting of normalized AISI 9310 is also discussed. This study will benefit the manufacturing industry with the understanding of how specific cutting processing parameters will impact the distortions and residual stresses in the machined AISI 9310 parts. [ABSTRACT FROM AUTHOR]

High thermal gradients during selective laser melting (SLM) can generate residual stresses due to uneven volumetric expansion, which can lead to weak or cracked parts. In SLM, scan path refers to the route the laser takes during a single layer of solidification, and has a direct impact on thermal gradient, and by association residual stress. This work uses a finite element model to compare the thermal gradients generated by nine different scan paths, six of which have been tested and discussed in literature, and three of which are proposed in this document. This study found that scan paths which subdivide powder layers into smaller areas were found to produce fewer areas of high thermal gradient, as well as a lower total average gradient when compared to paths that scan the full layer without subdivision. One of the new scan path concepts, named the "subsectioned spiral method", produced the most favorable results. Of the six non-transient data categories retrieved, the subsectioned spiral scan path outperformed all eight other paths, with improvements ranging between 6 and 44% compared with the baseline path. [ABSTRACT FROM AUTHOR]

Riveting is an important interference-fit joining technology, which has been widely applied in aircraft assembly and many manufacturing fields. The rivet head flushness is an import industrial standard for the quality evaluation of a riveted joint. It would influence the aerodynamic performance of aircraft if not carefully controlled. In this paper, a finite element model (FEM) of automatic countersunk riveting is established and the formation of rivet head flushness is studied by the simulation results. Then, based on the coordinated motion of the riveting bar and the anvil tool, several compensation strategies are proposed to reduce the rivet head flushness and ensure the riveting quality, in which the riveting bar and anvil tool feed with the same speed (RASS) strategy is considered as the most efficient one. Finally, riveting experiments are conducted on a dual-machine-based automatic drilling and riveting system. The experimental results indicate that the simulation result is accurate, and the RASS compensation strategy is applicable and effective. This paper studies the formation mechanism and compensation method of the rivet head flushness for the countersunk rivet and provides scientific guidance for the riveting process optimization in engineering applications. [ABSTRACT FROM AUTHOR]

An innovative manufacturing process for thermoplastic composite structures is proposed for the production of three-dimensional cylindrical lattice structures. An out-of-autoclave compaction process has been designed by using the compression of a heat-shrink tube during its shape recovery in oven. Thermoplastic prepreg tapes are wound on a metallic cylindrical-patterned mold at room temperature, and the full assembly is inserted in the heat-shrink tube before heating in oven. In this study, anisogrid lattice structures have been prototyped in E-glass/polypropylene composite. Circular composite rings were manufactured as well to measure for technology assessment. Finite element (FE) modeling has been used to predict mechanical performances of anisogrid lattice structures. Model calibration and validation was carried out by using the results from mechanical tests on rings. Numerical models were developed with a batch-type parametric approach to quickly evaluate combined effects of geometry and material parameters. Numerical results are in good agreement with experimental data, having less than 8% of maximum difference in the case of the complex anisogrid lattice structure. [ABSTRACT FROM AUTHOR]

Many techniques have been developed to improve the machinability of aeronautical materials titanium and nickel-based alloys such as ultrasonic-assisted turning, laser-assisted turning, and cryogenic-assisted turning. This collaborative scientific investigation presents the steps taken to gain insight into the phenomena of machining Nimonic 90 (a nickel-based alloy) alloy using ultrasonically assisted turning. The cutting speed, feed rate, depth of cut, and frequency are taken as input parameters and average surface roughness (Ra), power consumption (P), and chip formation are considered as output parameters. The experiments are carried out with the full factorial design. The UAT (ultrasonically assisted turning) process gives a significant improvement in average surface roughness and power consumption because of the intermittent cutting action of the cutting tool. UAT process shows a 70–80% reduction in average surface roughness (Ra) and a 6–15% reduction in power consumption as compared with CT (conventional turning) process. Ultrasonically assisted turning also resulted in the thin and smoother chips as compared with CT process which helps to achieve a more superior machining effect. Finite element modeling shows that the quasi-static nature of the stress induced in the UAT process leads to lower force and ultimately lower power generation. Moreover, a sustainability assessment model is implemented to investigate the effect of UAT in terms of machining performance as well as sustainability effectiveness in a single integrated approach. The novelty of this work lies in providing an integrated concept that combines experimental analysis and sustainability assessment when using ultrasonic vibrational energy during turning of Nimonic 90. [ABSTRACT FROM AUTHOR]

In this study, the analysis of influence temperature-velocity parameters of radial-shear rolling (RSR) on structure and properties of A1050 (Al99.5%) aluminum alloy using the finite element modeling was carried out. During RSR process, the nonuniform change in temperature-velocity parameters occurs in the volume of workpiece. The deformation temperature is one of the main influencing parameters. The gradient of temperature change over section is almost independent of the initial heating temperature of workpiece, and it increases with growth of rotary velocity. In the surface layer, the temperature and strain rate can vary over a wide range due to the deformation temperature and friction on the contact surface. With that, the change in temperature of the rod central zone occurs monotonically and, mainly, due to the energy of plastic deformation. The increasing in strain rate leads to the intense heating of surface layers of workpiece in deformation zone and the decreasing in temperature oscillations between deformation cycles. After RSR the rods with gradient structure and ultrafine surface layer with a microhardness of up to 43 HV were obtained. Depending on the selected temperature-velocity parameters, it is possible to obtain a different combination of mechanical properties (UTS~94...120 MPa; YS~88...110 MPa; δ~1...43.5%). The strength of obtained RSR rods in all regimes is significantly higher than the strength of industrial rods in a hot-pressed condition that shows the application prospect of RSR process as efficient method of controlled plastic deformation of aluminum alloys and obtaining long rods. [ABSTRACT FROM AUTHOR]

Bulk metallic glasses (BMGs) have unique properties due to their amorphous atomic structure such as excellent mechanical and thermal performances; BMGs are considered to be promising materials for many engineering applications. However, it is important to investigate the cutting mechanisms of BMG in ultra-precision micro-cutting (UPMC). This study focuses on experimental and theoretical investigations on the chip formation in UPMC of BMG. It was firstly found that twinned-serrated chips (TSCs) are generated in UPMC of BMG. The intrinsic cause is that BMG exhibits significant adiabatic effect, which was confirmed by a proposed finite element model. A series of ultra-precision micro-cutting tests have been carried out to verify the results of simulation and reveal the effect of rake angle on the cutting process of BMG. The simulation and experiment of chip formation proved that the adiabatic effect is the key factor to generate the serrated chips in the UPMC of BMG. In addition, there existed twinned shear in one cyclic of each serrated chip. The comparison between simulation and experiment under the machining condition of different tool rake angles showed that the serrated chip and cutting force are sensitive to the rake angle of tool. [ABSTRACT FROM AUTHOR]

A 3D model was employed to study the effect of melt initial superheat on the macrosegregation formation using FE modeling and experimentation methods. The casting process of three ingots with the initial melt superheats of 75 °C, 65 °C, and 55 °C were simulated. The three cases represented three variables encountered in industry during casting of large size ingots. For the above three studied cases, all other casting conditions were kept the same. Results showed that the variation of initial melt superheat gave rise to changes in temperature pattern, liquid flow field, solidification speed, and thermomechanical contraction. Under the combined actions of all these changes, lower superheat tended to alleviate the segregation intensity in the upper part of the ingot body, in the hot-top, and in the solute-rich bands between the ingot centerline and periphery. The beneficial effect of lower superheat on alleviation of segregation severity was confirmed by experimental chemical measurement results. The results were analyzed in terms of heat and mass transfer theories and allow for a better understanding of the underlying mechanisms responsible for the occurrence of macrosegregation in ingot casting process. The findings should be helpful for the casting process design of a given ingot of high value-added steels or other alloys. [ABSTRACT FROM AUTHOR]

Burrs generated in the drilling process of carbon fiber-reinforced polymers (CFRPs) can cause delamination, therefore significantly reduce the bearing capacity of the components during service. In order to address this issue, the multiscale finite element (FE) modeling was developed in this work to analyze the burrs formation mechanism. The proposed model combined the microscopic fiber and matrix phases with the macroscopic equivalent homogeneous material (EHM). Meanwhile, 3D Hashin-type damage initiation criteria were proposed to characterize the differences between the tensile and compressive strength of the EHM and fiber and their anisotropy feature. The cutting of the fiber and matrix phases under all cutting angles were divided into two simulation processes to improve the computational efficiency. With the help of this model, the thrust force was accurately predicted where the distribution of burrs was successfully simulated compared with the experimental measurements. In addition, the evolution process from the failure of the fiber and matrix phases towards formation of the burrs was clarified. It could be seen that in the drilling of the CFRPs at the hole exit, the matrix was removed while the fibers deformed out-of-plane under the push of the drill firstly rather than got removed and then bent with the rotation of the drill. Specifically, the fibers under acute cutting angles bent outward the hole radially, which made them more difficult to be removed and hence resulted in the burrs eventually. The revealed formation mechanisms would be the crucial contribution and guidance for helping to suppress the burrs. [ABSTRACT FROM AUTHOR]

At this present work, the feasibility of producing seamless tubes through recycling of aluminum machining chips via the double-step friction stir consolidation (FSC) process was investigated. This process was done in two distinct steps. At the first step, the chips are loaded into the container and slightly compacted, and then a rotating tool with a designated diameter is plunged into the chips at a chosen rotational speed and feed rate. Due to the frictional heating, the softened materials are compressed and merged to form a consolidated cylindrical bulk material eventually. In the second step, a rotating tool that is smaller in diameter than the first tool is again plunged into the recycled round bars at a selected rotational speed and feed rate, forcing the material radially outwards and afterwards forming tubes. The results show that the process is a feasible solution for producing structurally sound, void-free tubes directly from machining chips at two simple steps. A numerical model was implemented to predict the evolution of the main field variables including temperature, density, and strain in the process. [ABSTRACT FROM AUTHOR]

Force-induced deformation of machine tools has a great influence on the workpiece dimension and surface quality. For the dual-machine-based riveting system, the great squeezing force during riveting process not only causes structural deformation of the machine tools but also leads to inaccurate positioning of the riveting bar and dimension deviation of riveted joints. Moreover, the force-induced deformation usually changes with the varying poses of the machine tools, which makes it more difficult to predict precisely. In this paper, an efficient prediction and compensation method of force-induced deformation is developed based on finite element modeling (FEM) and artificial neural network. Firstly, a series of finite element models at selected poses are established to obtain the deformation data. Then, a force-induced deformation prediction model is established through radial basis function neural network with adaptive genetic algorithm optimization (AGA-RBF). Furthermore, a basic strategy is proposed to compensate for the predicted error through the motion commands modification. Finally, a contrast experiment is carried out to verify the feasibility and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

Scaled-down electric vehicle battery cooling plates were formed from multi-layered Al brazing sheets in the O and H24 sheet tempers between room temperature and 250 °C. The formed plates were joined using an industrial furnace brazing process. All brazed assemblies were leak-free when an internal pressure of 0.28 MPa was applied, demonstrating the integrity of the components. Digital radiography of the brazed assemblies revealed only localized defects within individual samples, with no obvious patterns appearing across all samples of a given forming condition. Thus, no clear difference in brazing performance between forming conditions was noted at the component level, although slightly more consistent brazed fillets were noted for the H24-250 °C condition compared to H24-RT. Strain distributions throughout the formed plate were predicted using a finite element model, to facilitate microstructure analysis of the brazed assemblies. The post-braze microstructure in plates formed from O temper sheet depended on the local strain, but did not strongly depend on forming temperature: liquid film migration and a non-recrystallized core were observed at locations of relatively low strain, while coarse recrystallized core grains and a clad residue were found at locations of high strain. Conversely, the microstructure was homogeneous throughout H24 temper plates formed at room temperature and at 250 °C, and consisted of a recrystallized core alloy and a clad residue layer at the sheet surface. It is concluded that warm forming does not adversely affect the brazing performance of Al brazing sheet and, therefore, is a promising manufacturing technique for the production of next-generation heat exchangers. [ABSTRACT FROM AUTHOR]

Hard turning is a manufacturing process widely used in aerospace industries. The effect of hard turning on the surface integrity is mainly influenced by the choice of the process parameters. The aim of this paper is to present an exhaustive study for optimizing the hard turning process parameters using the response surface methodology (RSM) coupled with the finite element method. In particular, a case study is developed where AISI 52100 (62 HRc) is machined by PCBN tool. For this purpose, a finite element model (FEM) of orthogonal cutting is developed by the software ABAQUS. In this study, empirical models of machining forces and white layers (WL) thickness are developed. The empirical models have been determined using the RSM, in which three factors with three levels are implemented. The cutting speed, the feed rate, and the depth of cut are considered as the main input parameters. The analysis of variance (ANOVA) was also employed in order to analyze the effects and interactions of the cutting parameters on the performance of machined parts. Lastly, the optimum parametric combination is determined to allow the minimization of machining forces and WL thickness. The proposed approach can be considered as a helpful method for engineering design to optimize hard turning parameters. [ABSTRACT FROM AUTHOR]

Finite element modeling (FEM) validated by experimental work was used to simulate the influence of thermomechanical shrinkage on macrosegregation of alloying elements in a large-sized ingot of high-strength steel. The full algorithms of the filling and solidification process for thermohydraulic and thermomechanic analyses were developed and implemented in the 3D FEM code Thercast®. Material properties were determined by a combination of experimental works, thermodynamic software Thermo-Calc®, a database, and literature source. It was predicted that thermomechanical shrinkage decreased the temperature gradients, advanced the initiation of solidification, and reduced the solidification time. The above changes resulted in less severe segregation along the centerline, in the zone next to the ingot surface, in the upper section of the ingot, and in the hot-top. Thermomechanic model predictions were proved to agree better with experimental results than the thermohydraulic one. The obtained results were interpreted in the framework of the theories on diffusion and solidification of alloyed systems. These findings contribute to a better understanding of the impact of thermomechanical shrinkage in ingot cooling process. They could also be used in industry to improve the quality of large-sized ingot production and the productivity of high value-added steels or other alloys. [ABSTRACT FROM AUTHOR]

This paper proposed a numerically low-cost 3D FE modeling method for multi-shot shot peening. The low computation cost and high prediction accuracy of shot peening are realized at the same time by the incorporation of random multi-shot with defined spacing between the adjacent simultaneously impinging shots, periodicity, and coverage rate of 100%. With this modeling method, one-step and dual-step multi-shot peening of 34CrNiMo6 steel target is modeled and the produced residual stress is predicted. In order to make the predicted residual stress depth profile more comparable with the measured one by XRD method, the redistribution of residual stress due to the layer removal by electrochemical polishing is simulated using Model Change technique. And the comparison between the prediction and experiment indicates that this improved 3D periodic FE modeling of multi-shot impingement provides very accurate simulation models for one-step and dual-step shot peening. It can substitute for the costly and time-consuming optimization experiments of the shot peening process, especially the multi-step shot peening process. Finally, the evolution of residual stress depth profile in dual-step shot peening process is investigated by using the simulation model and a variation of residual stress towards a more uniform distribution on the finished surface taking place in the second step is discovered by RMS analysis. [ABSTRACT FROM AUTHOR]

In this study, a method called microwave-assisted hot compaction process was used to fabricate bulk Al sample. After the cold pressing process of Al powders, the green compact was hot-pressed in a microwave-assisted hot press apparatus at 400 °C under the pressure of 50 MPa. Moreover, numerical simulation of microwave-assisted hot compaction process was performed using 3D finite element method. Comparison between numerical and experimental results was also investigated. The microstructure, pore distribution, and surface topography of the sample were observed by scanning electron and atomic force microscopes. The density of the bulk sample was measured by Archimedes technique. Finally, nanoindentation test was carried out to measure hardness and elastic modulus. The results showed that the sample was heated uniformly using microwave heating process. Despite the uniform heating, the top corner regions of sample exhibited higher density as compared to the bottom corner regions. However, the central regions of the sample consolidate uniformly. Also, the top corners of the sample with more densification showed an improvement in the mechanical properties of the sample. [ABSTRACT FROM AUTHOR]

The thermal cycling in the coaxial laser cladding process can cause significant variations in the strength of cladded parts as well as the development of residual stresses, large distortions, and even cracking. In the current study, the hardness variations, induced residual stress distribution, and the developed distortion characteristics of cladded parts are examined for different deposition tool paths. The research is conducted by means of numerical simulations validated by experimental results for selected surface cladding deposition strategies. The specimens were made using P420 stainless steel powder clad onto an AISI 1918 substrate. In the previous studies by the authors, it was found that the transient thermal solution using a moving heat source simulation technique required several days of computational time for small cladded parts, making it impractical for industrial applications. In the present research work, a modeling approach using a steady-state thermal solution was proposed. This technique produced similar results for hardness and residual stress in a shorter time period, but the resulted distortion values were not accurate. Consequently, a thermo-mechanical modeling approach was adopted that provided virtual distortion solutions correlating well with the experimental results. These models were subsequently employed to explore various process planning scenarios. The effect of surface cladding deposition patterns, the substrate dimensions, the plate dimension’s aspect ratio, and the time gap between beads deposition were simulated and the strength and physical defects of the clad layer results are compared. Moreover, the mechanical response and properties for a full-scale gasket part is investigated as an example representing an industrial application. [ABSTRACT FROM AUTHOR]

Finite Element (FE) modeling of machining processes has received growing attention over the last two decades. Since machining processes operate at severe deformation conditions, involving very high strain, strain rate, stress, and temperature, the modeling procedure is still a challenging task even with new advanced software and computers. Therefore, most of the published research works were mainly performed for the simplest configuration of machining known as orthogonal cutting, in which a plane strain deformation state is assumed. This configuration leads to reducing the number of elements in the FE model and the computational time of the solution, compared to conventional machining processes (turning, milling, and drilling). Nevertheless, FE modeling of orthogonal turning is still considered as an open-ended subject as most of the phenomena involved in the orthogonal turning process, which also exist in other machining operations, are not fully well understood. The present review article deals with finite element modeling of orthogonal machining process. The paper consists of several related parts. First, the fundamentals of the FE simulation of orthogonal turning process are briefly described. Then, a detailed review on the FE prediction of machining characteristics including chip morphology, cutting forces, cutting temperature, tool wear, and burr formation is provided. Also, the FE prediction of surface integrity characteristics including residual stresses and microstructural changes is discussed. The influence of input model and parameters including thermal, material, and frictional models as well as size and arrangement of elements on machining and surface integrity characteristics are explained as well. Both technical and statistical aspects of the FE simulation of orthogonal turning are treated. Since there is no review paper thoroughly and specifically discussing the methods and findings of the finite element simulation of turning operations, the present article can be used as a reference for researchers who are active and/or interested in this filed. [ABSTRACT FROM AUTHOR]

During the metal cutting operation, heat generation at the cutting interface and the resulting heat distribution among tool, chip, workpiece, and cutting environment has a significant impact on the overall cutting process. Tool life, rate of tool wear, and dimensional accuracy of the machined surface are linked with the heat transfer. In order to develop a precise numerical model for machining, convective heat transfer coefficient is required to simulate the effect of a coolant. Previous literature provides a large operating range of values for the convective heat transfer coefficients, with no clear indication about the selection criterion. In this study, a coupling procedure based on finite element (FE) analysis and computational fluid dynamics (CFD) has been suggested to obtain the optimum value of the convective heat transfer coefficient. In this novel methodology, first the cutting temperature was attained from the FE-based simulation using a logical arbitrary value of convective heat transfer coefficient. The FE-based temperature result was taken as a heat source point on the solid domain of the cutting insert and computational fluid dynamics modeling was executed to examine the convective heat transfer coefficient under similar condition of air interaction. The methodology provided encouraging results by reducing error from 22 to 15% between the values of experimental and simulated cutting temperatures. The methodology revealed encouraging potential to investigate convective heat transfer coefficients under different cutting environments. The incorporation of CFD modeling technique in the area of metal cutting will also benefit other peers working in the similar areas of interest. [ABSTRACT FROM AUTHOR]

The laser cladding process is associated with having a non-uniform material strength within the clad bead and the heat-affected zone. As well, residual stresses can develop, which in turn increase the crack driving force and reduce the strength and fatigue life of the part. In the present work, a finite element model was developed to simulate the temperature history, microhardness values, and induced residual stresses for a coaxial powder injection laser cladding process for P420 stainless steel powder on low/medium carbon steel plates. Residual stress developments for 10 single-track cladded specimens fabricated using different process parameter sets were studied by a simulation model. The model was validated with microhardness measurements and residual stress values. The effect of a heat treatment on the microhardness values and reduction of residual stress were also investigated. In the next research phase, a multi-track cladded specimen model was validated by microhardness measurements and a study was carried out on microhardness variations and residual stresses. A comparison between the simulation and experimental results exhibits the accuracy of the model to capture the laser cladding process phenomena. A well-designed simulation model can be used to determine the process parameters to avoid tensile and compressive residual stresses in the component and achieve the desired strength with more uniformity in the clad. [ABSTRACT FROM AUTHOR]

Gear rolling with local induction heating process is a novel method to produce large-diameter gears with great advantages. To investigate the gear forming process, a simplified finite element (FE) model coupling electromagnetic-thermal and deformation fields is developed in the DEFORM-3D software and is validated by corresponding experiments. According to the numerical and experimental results, producing large-diameter gears using gear rolling process with local induction heating is feasible. Moreover, the blank heated by local induction heating has a temperature gradient distribution in the radial direction, which results in the defect reduction of inner hole enlarging. Thanks to the heat compensation function of induction heater, the defect of metal folding in the tooth top of the blank is reduced. In addition, the formability is improved by using local induction heating and the rolling force drops drastically compared with cold rolling process. [ABSTRACT FROM AUTHOR]

In this paper, the effect of input heat and welding environment on microstructure and mechanical properties of friction stir spot welded TRIP steel sheets were investigated. Six types of joints produced in both air and water environments and under rotational speeds of 900, 1350, and 1800 rpm. Then, the microstructure and mechanical properties of them were studied. The thermal histories, strain, and strain rate distributions of cases obtained by finite element modeling. According to the temperature and strain distribution and microstructural observations, four different zones determined in welding region: stir zone, thermomechanically affected zone, and high and low temperature heat-affected zones. It is obtained at in-air welds by increasing the rotational speed, the strength of joints increase to a maximum value because of higher strain rate and more recrystallization of prior austenite grains. The strength then decreases due to high amount of heat input and growth of recrystallized grains. Thermal history of underwater welds showed lower peak temperature and rapid cooling rate. Also, by increasing rotational speed in underwater joints, the strength and hardness increased because of microstructure refinement. The fracture surfaces of joints showed a dimple pattern ductile fracture in all cases except 1800 rpm in-air joint that the fracture was less ductile which agrees with lower tensile elongation of it. [ABSTRACT FROM AUTHOR]

To improve the accuracy of finite element (FE) models used to simulate electric arc and beam-based fusion welding processes, a combined heat source model is proposed. The combined model, termed the polynomial heat source, is based on a Gaussian heat density distribution and employs a disc source to account for surface heating effects while a polynomial equation is used to define the volumetric heat power source. This provides an improved capability for matching the heat source power distribution to fusion zones having variable curvature and also results in a simplified process for defining heat source parameters as only three numerical values need to be determined. To validate the heat source model, fusion zone cross sections, thermal cycles, angular distortion, and residual stresses obtained using SYSWELD were compared to measurements taken from gas metal arc (GMA) welds made on 10-mm-thick high-strength low-alloy (HSLA) plates. Predictions obtained from SYSWELD using double ellipsoid and conical heat source models were also compared. An analysis of the FE predictions obtained from each of the three heat source models showed that the best agreement between simulated and experimental values was achieved using the polynomial model. This is attributed to the fact that heat power distribution can be adjusted at the top and bottom of the fusion zone and results in an improved level of bead cross section matching. It is expected that the proposed heat source model will be applicable for simulating both shallow and deep penetration welding processes where the fusion zone is symmetric about its centerline. [ABSTRACT FROM AUTHOR]

The behavior of the welding arc in the pulsed DC and AC gas metal arc welding processes was studied using real-time recorded current, voltage waveforms, and synchronized high-speed video at different electrode negative (EN) ratios for a constant wire feed rate. The regression equations were developed to predict the arc root dimensions as a function of welding current, voltage, time, and the EN ratio. A methodology was proposed to estimate the available energy rate distribution to the electrode and the base plate during the positive and negative cycles in pulsed AC gas metal arc welding (pulsed AC-GMAW) process. For an approximately equal peak positive current, the increase in the pulse time enhanced the molten electrode droplet diameter, arc plasma distribution, and the arc root dimensions. The fraction of the available arc energy rate supplied to the base plate was higher in positive pulse when compared to the negative pulse. A three-dimensional finite element modeling of pulsed DC-GMAW and pulsed AC-GMAW processes was performed to estimate the weld pool profile and temperature distribution in the weldment. The computed weld width, penetration, and the thermal cycles were in reasonable agreement with the corresponding experimental results. The peak temperature of the region in the weld pool near to the Gaussian distributed heat source experience fluctuations which were in synchronization with the current waveform. Increase in the EN ratio decreased the peak temperature while increased the cooling rate in the weldment. This reduced the bainite phase and enhanced the martensite phase in the weldment. [ABSTRACT FROM AUTHOR]

A three-dimensional finite model has been proposed to simulate the temperature field in selective laser melting Al-8.5Fe-1.3V-1.7Si (wt.%) heat-resistant aluminum alloy powder. The finite element analysis was carried out using the ANSYS code, taking into account temperature-dependent material properties, the effects of the powder-to-solid transition, and the movement of laser power with a Gaussian profile. The effects of the line energy (LE) on the temperature distribution, melt pool dimensions, and cooling rates were presented in detail. The phase transformations were also discussed based on the thermal analysis. The results show that the maximum temperature in powder layer increases with the applied LE. The predicted dimensions of the melt pool are in sizes of several tens of micrometers and increase with the LE. The predicted cooling rates across the melt pool decrease with increase of the LE and decline from the center to the edge of the pool. Under the optimized LEs of 1.2 and 1.6 J/mm, sound metallurgical bonding with less building defects between adjacent tracks and layers can be obtained; the cooling rates across the melt pool exceed 10 °C/s above the solidus temperature, which lead the formation of novel α-Al and A1(Fe, VSi phases. This phase composition is predicted to keep consistent during multiple tracks and layer melting. The simulation results were compared with those acquired via experiments, and a good agreement can be found. [ABSTRACT FROM AUTHOR]

Incremental forming is a sheet metal forming process characterized by high flexibility; for this reason, it is suggested for rapid prototyping and customized products. On the other hand, this process is slower than traditional ones and requires in-depth studies to know the influence and the optimization of certain process parameters. In this paper, a complete optimization procedure starting from modeling and leading to the search of robust optimal process parameters is proposed. A numerical model of single point incremental forming of aluminum truncated cone geometries is developed by means of Finite Element simulation code ABAQUS and validated experimentally. One of the problems to be solved in the metal forming processes of thin sheets is the taking into account of the effects of technological process parameters so that the part takes the desired mechanical and geometrical characteristics. The control parameters for the study included wall inclination angle ( α), tool size ( D), material thickness (Th), and vertical step size (In). A total of 27 numerical tests were conducted based on a 4-factor, 3-level Box-Behnken Design of Experiments approach along with FEA. An analysis of variance (ANOVA) test was carried out to obtain the relative importance of each single factor in terms of their main effects on the response variable. The main and interaction effects of the process parameters on sheet thinning rate and the punch forces were studied in more detail and presented in graphical form that helps in selecting quickly the process parameters to achieve the desired results. The main objective of this work is to examine and minimize the sheet thinning rate and the punch loads generated in this forming process. A first optimization procedure is based on the use of graphical response surfaces methodology (RSM). Quadratic mathematical models of the process were formulated correlating for the important controllable process parameters with the considered responses. The adequacies of the models were checked using analysis of variance technique. These analytical formulations allow the identification of the influential parameters of an optimization problem and the reduction of the number of evaluations of the objective functions. Taking the models as objective functions further optimization has been carried out using a genetic algorithm (GA) developed in order to compute the optimum solutions defined by the minimum values of sheet thinning and the punch loads and their corresponding combinations of optimum process parameters. For validation of its accuracy and generalization, the genetic algorithm was tested by using two analytical test functions as benchmarks of which global and local minima are known. It was demonstrated that the developed method can solve high nonlinear problems successfully. Finally, it is observed that the numerical results showed the suitability of the proposed approaches, and some comparative studies of the optimum solutions obtained by these algorithms developed in this work are shown here. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the tribology aspects of machining processes is essential for increasing the dimensional accuracy and surface integrity of finished products. To this end, the present investigation simulates an orthogonal metal cutting using an explicit finite element code, LS-DYNA. In the simulations, a rigid cutting tool of variable rake angle was moved at different velocities against an aluminum workpiece. A damage material model was utilized for the workpiece to capture the chip separation behavior and the simultaneous breakage of the chip into multiple fragments. The friction factor at the cutting tool-workpiece interface was varied through a contact model to predict cutting forces and dynamic chip formation. Overall, the results showed that the explicit finite element is a powerful tool for simulating metal cutting and discontinuous chip formation. The separation of the chip from the workpiece was accurately predicted. Numerical results found that rake angle and friction factor have a significantly influence on the discontinuous chip formation process, chip morphology, chip size, and cutting forces when compared to the cutting velocity during metal cutting. The model was validated against the experimental and numerical results obtained in the literature, and a good agreement with the current numerical results was found. [ABSTRACT FROM AUTHOR]