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In this work, the kinetics of the growth of austenite grains upon heating, the features of the processes of dynamic and static recrystallization occurring at various temperature-deformation modes of plastic deformation are investigated. Phase transformations have been studied during continuous cooling of hotdeformed austenite in low-alloy “Arc”-steel with a yield point of at least 420 MPa. The studies carried out made it possible to determine the thermal deformation parameters that ensure the formation of a finely dispersed homogeneous ferrite-bainitic structure, on the basis of which technological recommendations for industrial production were developed and sheet products were manufactured. Presented are the structure and properties of sheet metal from shipbuilding “Arc”-strength category 420 MPa.

Joining similar and dissimilar materials using polymer bonds is common practice being followed in various sectors. The strength of these polymer bonded joints depends on process parameters like adherend thickness; adhesive layer thickness, overlap, geometric configuration of joints, materials used and surface roughness of the sheet metal. The main aim of present experimental work is to optimize process parameters of Aluminium 2024-T3 joints bonded using Epoxy resin modified with rubber powder. Three variability levels were considered for each factor selected for the present experimental work. Bondline thickness was the most significant parameter followed by surface roughness, adherend thickness and the overlap.

The automotive industries are trying to optimize the forming and process parameters to reduce the weight of vehicle. Also, these optimized results are helpful to the manufacturer during decision making, so that overall product development or manufacturing time is reduced. In this paper, comparison of the strain paths, necking and fracture behaviors among the steel materials is performed. In this paper, the formability parameters such as strain path, thinning and contact pressures between die sets are studied. The strain path points are predicted by using FEA simulation in Pamstamp software for AISI304 and AISI409L grade material. The major and minor points are predicted at necking points for various specimens and these points are represented on FLD curve for both the materials. It is observed that AISI304 grade material showed higher formability i.e. 17% higher formability than the AISI409L grade material. The simulated and experimental results showed a closed match with good correlations though the variation between them is nearly 7%. Also, the microstructures are investigated by following standard metallographic process and after investigation it is observed that as the microstructure changes the locations of the deformed sheet parts also get changed.

The analysis of the influence of various technological solutions used in the thermal cutting of heavy-gage sheet metals to reduce the deformations of the resulting piece parts is given. It has been suggested to use a gas-oxygen cutting technology with packing sequence without localization of heat build-up. The effect of improving the efficiency and quality of production using the developed cutting technology is shown.

Today in the rapid competition of the industries to get the best quality of the product in the minimum required time is the main aim of industries. To get the best quality and maximum production most advanced machines are used. But there are no facts that use only the advanced machines, to maintain their performance is real requirement of the industries, also to give proper facilities to the workers with good environmental condition and to reduce their efforts is one of the objects to achieve the best quality and high production. Sheet metal is simply a metal formed into thin and flat pieces. It is one of the fundamental forms used in metal working and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material. Thicknesses can vary significantly, although extremely thin thicknesses are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate. Sheet metal also has applications in car bodies, airplane wings, medical tables, roofs for buildings (Architectural) and many other things. Sheet metal of iron and other materials with high magnetic permeability, also known as laminated steel cores, has applications in transformers and electric machines. There are three primary procedures in Layout. They are Parallel, Radial, and Triangulation. The major aim to our experiment is to study about pneumatic control system, study about double acting cylinder, study about the advantage of pneumatic hand operated valve and study about high speed blade. We are using scissors for simple sheet metal cutting. It is a manual method so that sheet metals are to be wasted sometimes because of mistakes happened such as wrong dimensions etc., and also even a simple cutting may take long time. We are using a pneumatic system for sheet metal cutting in an easy way. It is operated by a pneumatic hand lever of two ways control valve. Control valve is operated by a compressor. Keywords: Pneumatic, Automation, Sheet Metal, Pneumatic, Valve, Cutting Machine

Metal forming or shaping processes, such as sheet metal forming and bulk forming, are widely used in many industries including automotive industry. Before computational simulations were widely used in the field of metal forming industry, the trial-and-error based empirical approach was conventionally applied to the optimization of the metal forming process and product. The most commonly employed numerical approach in the metal forming process for robust process optimization is the finite element analysis. Friction, one of the parameters that significantly affect the accuracy of numerical analysis, depends on several variants such as surface quality, contact pressure, lubrication, deformation, and the forming environment. Despite the complexity and difficulty of identifying friction mechanisms, accurate friction models are essential and hence have been proposed by numerous researchers. In this paper, the friction models in the previous studies are reviewed by categorizing them into the boundary lubrication condition and mixed-boundary lubrication condition according to their evaluative influences on friction. Since friction models have been proposed based on the contact theories, an overview on the contact models is also included in this paper. In addition, the contribution of several parameters on the friction such as surface roughness and material properties of the tool, adhesion, contact pressure, sliding speed, bulk deformation is also discussed. This review paper aims to provide an understanding and insight into the friction modeling and simulation along with associated friction experiments.

In this paper, the limitations of the Hill48 yield model in predicting directional yield stresses and plastic strain ratios (r-values) were investigated. According to a theoretical derivation, there are several inherent forms of the variation law of uniaxial tensile yield stress and r-value with angles calculated by Hill48. Three types of materials, DC04, DP600 and AA3104, were taken as research objects, and the anisotropic parameters and prediction errors were obtained by direct solution methods and the non-associated flow rule (non-AFR) methods based on different numbers of experimental data were analyzed. The results show that the prediction accuracy of the Hill48 yield model mainly depends on whether the anisotropic behavior of the material satisfies the above change law and is not directly related to the value of r. On this basis, under the associated flow rule, an anisotropic parameter identification method based on the conditional extremum of the cost function was proposed. It can significantly improve the prediction accuracy of low-carbon steel materials compared with the direct solution method. The research results provide detailed insight into the reasonable application of the Hill48 model in sheet metal forming and a reference for investigating the limitations of other advanced yield models.

The wrinkling-free forming method for sheet metal forming based on the low-melting alloy (LMA) is a novel sheet forming method. The LMA as a forming pressure medium to transfer loading force is utilized to prevent bulking and wrinkling occurrence in the sheet forming process due to the its controllable fluidity by adjusting the heating temperature. In the forming process, the upper and lower surface of blank were acted by continued loading force resulting from LMA flowing. In this study, the high-temperature mechanical properties of LMA were obtained by heating tensile test for preparation of simulation. The rheological behavior of LMA during the forming process was analyzed numerically. And the effect of LMA layer thickness, forming force and mold structure on the thinning of the formed parts was studied. With obtained results, the characteristic of wall thickness distribution and the effect of rheological behavior on thinning of formed part were comprehensively revealed. Moreover, the experimental results agree with those in numerical simulation by measuring the wall thickness of the formed specimen.

With the increasing demand for light weight design in industries such as aerospace and automotive, sheet metallic materials with high strength and low density have been intensively manufactured and widely applied. However, plastic deformation induced surface roughening is an undesirable and a practically unavoidable phenomenon for sheet metallic materials and becomes the subject of great attention in recent years. The evolution of surface roughening plays important roles in the strain limit of the deformation and also significantly influences the product quality and application. This paper provides a comprehensive overview of both experimental and numerical modelling contributions to understand the surface roughening behaviour of sheet metallic materials during various plastic deformation and manufacturing processes. It has been found that roughening of the free surface or necking of the interface is induced by grain scale strain heterogeneity and strongly dependent on the strain the material experienced, strain state and direction, grain size and texture, lubrication, mechanical properties of materials, rolling parameters, etc. By controlling and optimising these parameters, the surface roughening can be optimised for different materials and processing techniques to suit different applications.

The stress state of the sheet has a significant influence on the formability during the sheet metal forming process. Some research has shown that the through-thickness shear stress on the sheet can improve the formability of sheet metal. In order to provide a complete picture about the reasons and ways that the through-thickness shear stress affects the formability, this paper analyzes and summarizes the effects from three aspects: theory, numerical analyses, and experiments. Besides，the methods of generating through-thickness shear stress are discussed, and the research progresses of the M-K model considering the through-thickness shear stress are reviewed. Based on the establishment of the extended M-K model, the forming limit considering the through-thickness shear stress is predicted, and the mechanisms of through-thickness shear stress improving the formability are analyzed further. The numerical methods of analyzing through-thickness shear stress improve thickness uniformity of the sheet are also reviewed. The design of experimental setups and experimental methods for studying the influence of through-thickness shear stress based on friction and the interface tangential viscous adhesion stress on sheet formability are analyzed and compared. Finally, the future research orientation of the through-thickness shear stresses is proposed.

In the deep drawing process, the friction between sheet metal and die can be reduced by ultrasonic vibration (UV) or low frequency vibration (LFV), and the forming performance can be improved by the surface effect. In this study, a new friction test apparatus to determine the effect of both UV and LFV on the friction coefficient in the die radius region was designed and fabricated. The apparatus can realize UV and LFV conditions by switching the vibration exciters. New, simplified theoretical models with combined types of vibration were proposed, including flexible friction model and vibration superposed model. Using these models, the reduction mechanism of the macroscopic friction coefficient was investigated, and the corresponding mathematical expressions were derived. The theoretical results showed that the reduction ratio of the macroscopic friction coefficient (RMFC) is a function of only two parameters: the dimensionless relative velocity ratio and the wrap angle. Several groups of tests were conducted on three materials, stainless steel 304, brass CuZn40 and aluminium 1060, under UV and LFV conditions, and validated the theoretical results. Tests under UV conditions obtained higher RMFC values than those under LFV conditions, but caused more wear and adhesion.

Chain-die forming can be used to manufacture Advanced High Strength Steels (AHSS) channel components. Flange wrinkling is one of typical defects for chain-die formed products. The purpose of this paper is to investigate the cause of flange wrinkling in chain-die forming of AHSS and to propose a potential method to suppress it. A hat channel product with a curved axis is formed as a benchmark to illustrate the mechanism of flange wrinkling in chain-die forming. When forming such a profile, longitudinal compressive strain of the sheet metal is geometrically necessary, and the compression has to be achieved by plastic wrinkling due to the insufficient restricted boundary condition. Finite element models are established to better understand the complex interaction between the tools and plate. An initial imperfection calculated from the differential equilibrium equations for elastic plates with small deflections is implemented into the finite element model to predict occurrence of the flange wrinkling. In order to eliminate the wrinkling defect, an M-shaped die design is proposed, which intends to provide additional restriction to the sheet metal and increase longitudinal and transversal tension. A three-factor, three-level Design of Experiment (DOE) scheme for the M-shaped die design is conducted. The DOE results show that a benign wrinkling always corresponds to a larger compressive strain and the width of the ears for M-shaped dies is a decisive factor to suppress wrinkling. The verification experiments show that the plastic flange wrinkling is completely eliminated by employing the proposed method.

Hole expansion ratio (HER) is extensively used in the sheet metal forming industry to assess the sheet metal’s stretch-frangibility limit. Cold-rolled dual-phase steel (DP 590) showed planar anisotropy during the uniaxial tensile test. Hill-48 yield criterion was selected to represent the planar anisotropy of DP 590 steel sheet. Material constants i.e. anisotropic yield stress ratios of Hill-48 yield criterion were calculated from the r-values (Lankford coefficient) determined from the uniaxial tensile test. The finite element simulation result showed that the thickness reduction was maximum at 45° to rolling direction during hole expansion, and a crack was visible in the same location during hole expansion experimentation. HER of DP 590 steel and crack location were successfully predicted from the finite element model for Wire-Electrical Discharge Machine cut central hole edge in the present work.

Based on a self-design comprehensive experimental platform, the experimental investigation on electropulse-assisted incremental forming (EAIF) was carried out. By means of the response surface methodology, the interactive influence rules and significances of different processing parameters on formability of AZ31B sheet metal were investigated. The experimental results show that, compared to other processing parameters, the electropulse parameters are the most significant factor, and with the increase of electropulse parameters, the forming limit of sheet metal increases obviously. In addition, an interaction effect was found between the electropulse parameters and the feed rate/tool diameter, as well as between the feed rate and the step size. Through the comprehensive optimization and analysis, there was an optimal formability for sheet metal when the electropulse parameters, feed rate, step size, and tool diameter were set in 80 V/400 Hz, 800 mm/min, 0.2 mm, and 8 mm, respectively. The research on strain state shows that the linear loading mode of rectangular pyramid presents the plane strain state, while the circular loading mode in cone model presents a tendency of biaxial stretch, and the ultimate strain has reached 150%. Benefitting from the electro-plastic effect, the high-energy electropulse can promote the dynamic recrystallization and restrain the crack growth in materials, so compared with the conventional incremental forming, the EAIF under optimal processing condition can greatly improve the forming limit of AZ31B sheet metal.

At the Magnetic field condition, the surface quality of formed parts can be improved significantly. To investigate the technical advantages of Magnetorheological (MR) fluid as a soft media, eliminate the defects of the parts because of the complex deformation, such as wrinkling, cracking, and over thinning. A new method of sheet deep drawing forming with MR fluid through inverse bulging pre-forming was proposed, which has made the wall thickness distribution more uniform and changed the stress distribution of sheet by changing the rheological property of MR fluid. The theoretical pressure transfer model of MR fluid as media and the configuration model of inverse bulging pre-forming are established. It can be concluded that the relationship between bulge height and load time have been shown consistency compared with experimental results and agree well with the theoretical analysis. And the configuration model have shown good agreement from the experiments results and the numerical results espectively with theoretical results. The uniformity of the wall thickness and the surface quality of the deep-drawn parts are improved significantly with the increase of the inverse bulging height. When the inverse bulging height is about 9 mm, the pre-forming effect is optimal, which provides theoretical guidance and is of much potential to the forming of the and thin-walled complex parts in industry fields.

A new electro-permanent magnet combined blank holder technique has been developed by using permanent magnetic force to supply the blank holding force (BHF) for sheet metal deep drawing. In this work, the workability of the designed magnetic circuits was simulated and tested. A series of numerical simulations and experiments have also demonstrated its ability to overcome temperature rise and provide sufficient magnetic force. The advantages and availability of the combined blank holder technique were expatiated by theoretical derivation, and analyzed by FE stress analysis. The feasibility and effectiveness of the new blank holder method have been proven by a series of experiments for deep drawing a workpiece of 08Al with a diameter of 220 mm. With the segmental blank holder, the flange wrinkling is demonstrated to be suppressed well than using the single blank holder. Also, experimental results corroborated that current is only instantaneously imposed when switching magnetic force state, and not at other times.

To reduce the springback after sheet stamping, two forming processes which include electromagnetic forming (EMF) were designed. Compared with traditional electromagnetic-assisted stamping (EMAS), the new methods use the same mold structure and control springback without obvious plastic deformation. The ANSYS and ABAQUS software were used to analyze the influence of different discharge voltages on springback in the two forming processes. The simulation results accurately predict the deformation and springback of sheet metal after quasi-static stamping and subsequent EMF. After coil discharge, the sheet oscillates with high frequency and small amplitude and only exhibits insignificant deformation. With the increase of the discharge voltage, the sheet springback angle decreases. The springback inhibition effect of process 1, in which the sheet corners merely touch the coil surface, is greater than that of process 2, where the sheet was pressed close to the coil surface.

The fracture forming limit diagram (FFLD) is gaining special attention in high strength materials where the necking tendency rarely occurs during sheet metal forming processes. In the present work, the classical Marciniak and Kuczyński (MK) model has been modified by coupling it with different ductile damage models (Cockcroft and Latham, Brozzo, Oyane, Ko, Oh, Rice and Tracey, McClintock and Clift) and anisotropic yielding functions (Hill 1948 and Barlat 1989) to predict the fracture limits of Inconel 625 (IN625) alloy at different temperatures. Firstly, uniaxial tensile testing has been conducted for the determination of important mechanical properties. Consequently, stretch forming experiments have been performed to analyze the forming limits of a material. It has been found that the safe and fracture forming limits of the material increased by approximately 17.26% and 22.22%, respectively, on increasing the temperature from 300 to 673 K. From the comparative analysis of different combinations of ductile damage models and yielding functions, the Cockcroft and Latham (C-L) damage model in combination with the Barlat 1989 yielding function helped in best predicting the theoretical FFLD as it displayed the least average root mean square error (RMSE) of 0.033. The other ductile damage models used for predicting the theoretical fracture limits displayed large error; hence, they should not be considered while designing a critical component in the manufacturing industry using IN625 alloy.

Punctiform mechanical joining technologies, such as riveting, clinching, or screwing, which are widely used in sheet metal processing, are frequently applied because they have been established for many years. Depending on the process, they offer a variety of advantages such as one-sided accessibility, re-detachability, and no need for pre-punching operations or auxiliary joining elements. In addition, the processes often guarantee a high process reliability and extensive process monitoring. However, with thermoplastic composites, they lead to considerable stress concentrations at the joint due to the fibers. Undesirable fiber and inter-fiber breaks then result. With the development of the novel joining technology of joint stamp riveting, an improvement is achieved in this situation that has been described for hybrid joints on components made of thermoplastic composites and metal sheets. The joining principle is based on the formation of a form lock between the joining partners. The thermoplastic composite is thermomechanically formed by means of a joint stamp without using an auxiliary joining element. Within the scope of a research project, the joining process was characterized with regard to the structure of the joining spot, the geometry of the forming tools, and also the mechanical properties for purposes of analyzing and designing the joining process.

The forming process of high-strength sheet metal alloys is in great demand, and its applications in nuclear and defense industries are much significant. In the present investigation, the A516-Gr70 carbon steel plates are deep-drawing under warm (700 °C) and cold (27 °C) conditions using 1000 Ton hydraulic press. Numbers of deep-drawing experiments are conducted in two different states to study the microstructure and hardness at ambient temperature and also to study the impact strength at sub-zero temperature for different regions of the cup. In this study, changes in the microstructure of the deep-drawing cups with having two different samples subjected to normalizing heat treatment are observed.

Electromagnetic forming is a high-speed processing technology that uses Lorentz forces to achieve plastic forming. In existing research, electromagnetic induction coupling between the coil and the metallic workpiece is generally required to produce the Lorentz forces. This brings an inevitable challenge to the practical application, that is, the limited coil life due to both mechanical and thermal loads. In addition, in most cases, the Lorentz force acting on the workpiece is non-uniform, which limits its application to a certain extent. In this work, a coil-less electromagnetic sheet metal forming system is developed to solve these issues. A three-dimensional circuit-electromagnetic-mechanical coupling numerical model is established, and a series of simulations and experiments are carried out to reveal the dynamic forming process with uniform-pressure characteristics. Furthermore, we introduce a pulsed current transformer with a current rise coefficient of about 8 to improve the coil-less forming system, which can generate a large current in the workpiece using a small current in the primary circuit. On this basis, we compare the forming process with and without the pulsed current transformer, and discuss the corresponding mechanism. The numerical and experimental results can be useful for understanding the coil-less forming process, as well as promoting the advancement of electromagnetic forming.

Press-brake bending is one of the important sheet metal forming processes widely used to fabricate different angles and channels in automotive applications. Plastic deformation of material during bending generates elastic stress waves known as acoustic emission (AE), enabling online monitoring of the bending process. The analysis of these stress waves helps in process characterization and aids in the identification of defects. The non-homogeneous plastic deformation that occurs during bending leads to the development of residual stress (RS) in the bend regions after forming. The locked-in residual stresses that remain after bending are measured using the x-ray diffraction method. The present study aims to use the AE technique for online bend monitoring of austenitic stainless steel (SS) of type 304L and correlate the AE parameters acquired during bending with the final locked-in RS present in the bend regions. Toward this, SS 304L sheets were bent to various bend angles, viz. 45°, 60°, 90°, 108°, 120°, and 135°, along the rolling direction and perpendicular to the rolling direction. Among the many AE parameters derived from the analysis of AE signals, it is shown that normalized cumulative counts and energy increase with bend angle. The increase in AE is well correlated with the RS that develops due to plastic deformation. The observed correlations between AE parameters acquired during bending and RS measured after bending are discussed.

In order to reduce fuel consumption and thus pollutant emissions, the automotive industry is increasingly developing lightweight construction concepts that are accompanied by an increasing usage of aluminum materials. Due to poor weldability of aluminum in combination with other materials, mechanical joining methods such as clinching were developed and established in series production. In order to predict the relevant characteristics of clinched joints and to ensure the reliability of the process, it is simulated numerically during product development processes. In this regard, the predictive accuracy of the simulated process highly depends on the implemented friction model. In particular, the frictional behavior between the sheet metals as well as between the sheet metal and clinching tools has a significant impact on the geometrical formation of the clinched joint. No testing methods exist that can sufficiently investigate the frictional behavior in sheet materials, especially under high interface pressures, different relative velocities, and long friction paths, while allowing a decoupled consideration of the test parameters. This paper describes the development of further testing concepts based on a proven tribo-torsion test method for determining friction coefficients between sheet metal materials for the simulation of clinching processes. For this purpose, the correlation of interface pressure and the relative velocity between aluminum and steel sheet material in clinching processes is investigated using numerical simulation. Based on these findings, the developed concepts focus on determining friction coefficients at interface pressures of the above materials, yield stress, as well as the reproduction of the occurring friction conditions between sheet metal materials and tool surfaces in clinching processes using tool substitutes. Furthermore, wear investigations between sheet metal material and tool surface were carried out in the friction tests with subsequent EDX analyses of the frictioned tool surfaces. The developed method also allows an optical deformation measurement of the sheet metal material specimen by means of digital image correlation (DIC). Based on a methodological approach, the test setups and the test systems used are explained, and the functionality of the concepts is proven by experimental tests using different sheet metal materials.

In this work, the influence of material models used in the FEM simulation on the springback prediction is investigated. The interest of this paper is to extend the knowledge base regarding springback predictions in numerical simulation. The springback effect of a V-shaped sheet metal part made of TRIP steel, with a thickness of 0.75 mm was investigated. The bending angle was set to 90°. In the numerical simulation, Hill48 and Barlat yield criteria were used in combination with Ludwik's and Swift's hardening models. Achieved data from the numerical simulations were compared and evaluated with experimental test results. The experimental results showed the relation between springback and calibration force. The effect of specimen cut direction on the springback was smaller in comparison with the calibration force. The numerical results of the springback were not identical with the experimentally achieved springback values in most cases. Particularly, when a calibration force of 1 800 N was used in the simulation. The simulation results showed a good correlation between experimental and numerical results, when Hill48 and Barlat yield criteria were used in combination with Ludwik hardening law and calibration force F with the value 900 N was applied.

Rubber pad forming is one of advance processing technologies. With both rubber pad and die, the sheet metal is stamped into the required shapes. The shapes of the die directly affect the final shapes of the channels on the sheet. With the developments of micro-channels, a new kind of two-step channels is concerned gradually in many fields. Since there are waved structures in these channels, many beneficial functions are caused. However, the manufacturing of this new kind channels by rubber pad forming are still not meticulously researched. This article is focused on the rubber pad forming process of different two-step channels. Different two-step channels are designed and made. Based on both FEM and physical experiments, the forming processes of these new channels are researched. The forming results are discussed and compared with each other, the best design strategy is also proposed through results.

In the present work, springback behaviour of a three-ply clad sheet metal, comprising of layers of SS430 and SS304 sandwiched with a layer of AA1050 is investigated in V-bending by using analytical, experimental and simulation techniques. The developed analytical model is based on theory of bending using Hill’s anisotropic yield criterion. The tensile properties of the clad sheet and individual layers oriented at three different directions w.r.t. the rolling direction are characterized. The tensile properties of the individual layers are used in the material model of analytical and numerical predictions of the springback. It is observed that the samples of the clad sheet which are transverse to the rolling direction, exhibit highest springback values due to higher tensile strength of the sheet when compared with the results acquired for other two orientations w.r.t. the rolling direction. These results are endorsed by the springback results obtained from analytical and simulation methods. The effect of sheet setting on the die during bending is also investigated using different techniques. The resulting longitudinal stresses before and after springback are analysed on inner and outer layers of the tested samples using experimental and numerical simulation procedures. In both the cases of sheet settings, the results of residual stress after springback predicted by simulations agree with the experimental results except a few cases.

Wrinkling is generally induced because of metal instability and considered as an undesirable defect in sheet metal forming processes. Wrinkling leads to severe influence on functional requirements and aesthetic appeal of final component. Thus, the present research is mainly dedicated on the experimental and numerical analysis for wrinkling behavior prediction of Inconel 718 alloy at elevated temperature conditions. Initially, Yoshida buckling tests (YBT) have been conducted to investigate wrinkling tendencies of Inconel 718 alloy from room temperature (RT) to 600°C by an interval of 200°C. Subsequently, Finite Element (FE) analysis of YBT has been performed to analyze post buckling behavior. Critical strain values at onset of wrinkling are determined and strain based wrinkling limit curves (ε-WLCs) are plotted at different temperatures. In-plane principal strains are transferred to effective plastic strain (EPS) versus triaxiality (η) space to differentiate the transformation between safe and wrinkling instability. Finally, complete forming behavior of alloy is represented by means of fracture, forming, and wrinkling limit curves. The gap between forming and wrinkling limit curves at elevated temperature is ∼1.5 times higher than that at room temperature.

An efficient isogeometric-based framework is presented to integrate optimum design and formability analysis of sheet metal forming processes. To assess the quality of the formed parts, several objective functions such as fracture, wrinkling, thickness variation, and stretching are studied. In this framework, geometric parameters of addendum surfaces and middle tools are considered as design variables, the objective functions are calculated using the recently developed one-step and multi-step inverse isogeometric methods, and the optimum design variables are obtained using the genetic global optimization algorithm. The major advantage of employing the inverse methods is to analyze the formability of the parts with a low computation time. In this research, the effects of altering addendum surfaces and/or middle tools on the quality of the formed parts are simultaneously observed since modeling, formability analysis, and optimization stages of sheet metal forming simulation are integrated using the NURBS functions. To evaluate the performance of the inverse isogeometric models in calculation of the studied objective functions, the results obtained by these models are compared to those of experiment and forward FEM. Comparisons of the results indicate that these models predict the objective functions with acceptable accuracy at a low computation time. For instance, in sheet metal forming analysis of a rectangular box with three different addendum surfaces, the maximum error in prediction of minimum thickness using the one-step inverse model is approximately 4.65% more than forward FEM, while the solution time of forward FEM is around 40 times greater. Finally, the presented optimization procedure is applied to design addendum surfaces in forming of a rectangular box and the middle tools in a two-stage drawing of a square box. The results of these problems confirm the credibility of the present approach in rapid optimum design of addendum surfaces and intermediate tools with acceptable accuracy.

In this research work, an attempt was made to reinforce AA7168 aluminium alloy with Boron Carbide (B4C) and Silicon Carbide (SiC) through compos casting technique. Tribological test were performed ...

An accurate uniaxial constitutive model is necessary to analyse the plastic deformation behaviour of metal and for reliable finite element simulations in sheet metal forming operations. In the pres...

At present decreasing of costs and increasing of efficiency are the most priority directions in any industry. Developing in this way, JSC “Ural steel” together with FGUP “CNIIchermet after I.P. Barding” had mastered production of sheet metal product with increased resistivity against atmosphere corrosion made of steel 14ХГНДЦ for construction of bridges. Because of specific chemical composition of the steel, in the process of metal structures running in the open air, a solid strong oxide film is formed on the metal of the structures which prevents further corrosion without painting. For bridge builders elimination of costly operation of painting of span structures will enable to decrease considerably the costs of bridges construction and running. Having many advantages, steel 14ХГНДЦ has some restrictions in applications for steel structures without painting, as follows: - in sea zone according to domestic norms no close than 500 m from coastline; - in case of disorderly conditions of protective film formation and/or application of salt solutions for surface cleaning (as a rule the restrictions refer to traffic area of bridge span). In view of that for JSC “Ural Steel”, as the leading producer of bridge steel in Russia, an actual task erose: to elaborate and create a weatherproof steel, which could not only operate the whole period of a bridge running without additional protection at bridges con­struction through sea areas or close to coastline, but also withstand severe climate conditions of our country, including areas of High North with temperature lower -50°С. To solve the task together with OJSC “Institute Giprostroymost” and JSC BNIIZhT, a research work was accomplished to elaborate a system of alloying new steel 06ГН3МД with nickel content ~3.0 %, as well as production modes ensuring required corrosion resistance for operation in sea zone. Results of laboratory studies of the new weatherproof steel 06ГН3МД for application in bridge structures for coastal conditions and sea areas presented. Results of mechanical, technological, corrosion as well as fatigue tests of rolling products of the elaborated steel presented. It was established by laboratory studies that the new steel is weatherproofed and ensures lower corrosion losses, higher impact toughness at negative temperatures and plasticity comparing with steels used at present. It was shown that the strength class, technology and modes of factory welding of steel 06ГН3МД meet the requirements to steel span structures of bridges. Base on the results of the studies, the chemical composition of the steel 06ГН3МД was specified, as well as modes of heat treatment, ensuring the required characteristics with significant acceding. It was established that samples of the new steel 06ГН3МД showed considerably higher corrosion resistance - in average by 20% comparing with steel 14ХГНДЦ. At that corrosion resistance tests of welded joints of the new steel showed even higher resistance of the seam comparing with the basic metal, which speaks about quality selection of welding modes and welding materials.

For sheet metal parts with the vertical-wall partially and irregularly distributed on the sides (VWPIS) that contains both the difficult-form-surface (i.e., vertical-wall) with large forming angle and easy-to-form surface (i.e., gently tilted surface) with small forming angle, a selective multi-stage two point incremental forming (SMTPIF) on the basis of the forming angle was proposed. This SMTPIF method performs multi-stage forming only for the difficult-form-surface and gives different forming strategies and forming parameters to the different surface regions according to the forming angle. The algorithms for surface zoning, generation of the small forming angle surface for vertical-wall, generation of one-stage forming model by combining the easy-form-surface and small forming angle surface were presented. Meanwhile, the algorithm for the generation of the toolpath that is suitable to the SMTPIF was also given. The effectiveness of the proposed algorithm and the SMTPIF was verified by using the case studies, the finite element analysis, and the forming experiments. The results indicate that the SMTPIF can fabricate the VWPIS with short forming time and no sinking phenomenon.

The large ellipsoid parts are the main load-bearing components in the rocket tank, which are prone to wrinkle when using the traditional stamping. In order to solve the wrinkling problem in large parts, the EMIF method with a variable blank holder is proposed in this paper. The numerical simulation has shown that the sheet material near the blank holder is, as a consequence of stamping, subjected to circumferential compressive stress. When the drawing height was 100 mm, the sheet metal was notably wrinkled. In the electromagnetic forming (EMF) process, the sheet region facing the coil becomes thinner. However, the sheet metal thickness corresponding to the coil edge increases with the increase in forming height. If the EMF forming height is 150 mm, the sheet, which is in contact with the smooth mold, is deformed without a wrinkle. Compared to the traditional stamping, the EMF can significantly reduce the sheet metal wrinkling, improving the deformation height of the sheet metal smooth area.

Electromagnetic forming is a high-speed forming process, and it can generate high contact force between the sheet metal and die. Therefore, the effects of die counter-impact on aluminum alloy sheet during electromagnetic forming were numerically and experimentally investigated. Firstly, the numerical simulations of electromagnetic free forming and electromagnetic die forming were performed with the Gurson-Tvergaard-Needleman damage model. When the aluminum alloy sheet impacted the die, an unignorable normal stress occurred along the thickness direction. The void volume fraction was reduced due to the negative stress triaxiality, and the residual stress became smaller. Secondly, the effect of die counter-impact on the pre-deformed aluminum alloy sheet was numerically inspected for quasi-static and dynamic hybrid electromagnetic forming. Compared with the electromagnetic die forming of aluminum alloy sheet without pre-deformation, the void volume fraction and residual stress reductions were more significant for the pre-deformed aluminum alloy sheet. Finally, the aluminum alloy sheets after different electromagnetic forming experiments were compared by optical microscope and Vickers hardness. The results show that the damage suppression and hardness enhancement are attributed to the effect of die counter-impact, especially for the hybrid quasi-static and dynamic forming processes.

Chain-die forming is an emerging sheet metal technique for manufacturing advanced high strength steel (AHSS) products. Springback and longitudinal bow are two of the major shape defects in gradual forming. In this study, the springback and longitudinal bow of AHSS in chain-die forming of hat and U profiles are investigated through experiment and finite element simulation. The disparity of springback along the longitudinal direction and disparate longitudinal bow signifies complex deformation processes of chain-die forming. Finite element simulation of the chain-die forming process gives an insight into the formation of non-uniform springback and longitudinal bow. The gradual forming process by one die block after another causes bending and reverse-bending deformation in the web area and the redundant deformation of the sheet metal, which further leads to non-uniform bending moment and accumulated stresses along the longitudinal direction. At the same time, the redundant deformation will also result in the longitudinal strain on the edge, while the downhill deformation decreases the maximum longitudinal strain at the edge and introduces the longitudinal strain on the web. The different non-uniform longitudinal strain distribution along the transversal direction causes disparate longitudinal bow behaviors for chain-die formed AHSS hat and U profiles, downward bowing and upward bowing respectively. By the established model, the disparate springback and longitudinal bow behavior can be determined, which also contribute to the process design for chain-die formed AHSS products.

Sheet springback and structural deformation of the folding mechanism are key issues in the sheet metal–forming process. Elastic-plastic bending theory and numerical simulation are applied to study the forming performance of sheet metal. First, a springback prediction model under general assumptions is established, based on the constitutive relationship of the elastic-plastic linear hardening material. In addition, the influences of processing parameters, such as sheet thickness and forming angle on springback, are analysed according to the theoretical model and verified by experiments. Then, a laser tracker is used to acquire the folding trajectory, and the structural deformation of the folding mechanism is confirmed by trajectory comparison. On this basis, numerical simulations are performed to collect deformation parameters, and a formula for mechanical compensation is obtained by linear fitting to the simulation data. Finally, experimental tests are carried out to verify the accuracy of the compensation model. The results show that the forming precision of the sheet metal can be controlled in the range of $\pm 10^{\prime }$ . The proposed method is generally applicable to linear hardening materials and operation conditions where the sheet thickness ranges from 0.8 to 3 mm.

Forming limit diagrams (FLDs) are widely used in sheet metal industries to assess formability. These are graphical representations of major and minor strains on a 2-D plot separating safe and unsafe regions. Limiting strains were measured by digital image correlation (DIC) technique. In the present work, microstructure evolution and forming behavior of family of interstitial free steels: interstitial free (IF) and interstitial free-high strength (IF-HS) grades have been investigated. Both experimental and finite element (FE) simulated FLDs indicated higher formability for IF steel. Microstructural developments affect forming limits and influence forming limit diagrams. Evolving microstructure during forming was studied by texture developments using x-ray diffraction (XRD) and in grain average misorientation developments using electron backscattered diffraction (EBSD) techniques as a function of strain and strain paths. Estimated microstructural parameters revealed that the enhanced formability of IF steel was due to the presence of strong γ-fiber (ND// ) recrystallization texture and corresponding absence of θ-fiber (ND// ). On the contrary, IF-HS steel showed the abundant θ-fiber component and hence decreased formability.

Experimental and numerical study regarding the uniaxial tensile test and the forming limit diagram are addressed in this paper for AL2024 with the face-centered cube structure. First, representation of a grain structure can be obtained directly by mapping metallographic observations via scanning electron microscopy approach. Artificial grain microstructures produced by Voronoi Tessellation method are employed in the model using VGRAIN software. By resorting to the finite element software (ABAQUS) capabilities, the constitutive equations of the crystal plasticity were utilized and implemented as a user subroutine material UMAT code. The hardening parameters were calibrated by a trial and error approach in order to fit experimental tensile results with the simulation. Then the effect of the changing grain size, the heterogeneity factor, and the grain aspect ratio were studied for a uniaxial tensile test to emphasize the importance of the microstudy behavior of grains in material behavior. Furthermore, the polycrystal plasticity grain distribution was employed in the Nakazima test in order to obtain the forming limit diagram. The crystal plasticity-driven forming limit diagram reveals more accurate strains, taking into account the involving the micromechanical features of the grains. An innovative approach is pursued in this study to discover the necking angle, both in tensile test or Nakazima samples, showing a good agreement with the experiment results.

Incremental Sheet Forming (ISF) is a sheet metal forming process, which relies on minimum part-specific tooling. Extra Deep Drawn (EDD) steel has been used for making door inners, dash panels, bodyside inners, etc. due to its good weldability and relatively low yield strength. However, to date very limited work is reported on ISF of EDD steel. Besides, no work, which exhaustively discusses the practicability of EDD steel for effectual incremental forming of components, is found to be reported. The present work discusses the ISF of EDD steel sheets and examines the limitations of ISF in forming the parts out of 1.0 mm thick EDD steel sheets. Two geometries, i.e., ellipsoidal cone (with varying wall angle) and truncated cone (with constant wall angle) were used as test cases to evaluate the formability of EDD steel sheets, in terms of Critical Wall Angle (CWA). Further, the formability of EDD steel with ISF is evaluated using both strain-based and stress-based forming limit curves. The thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness are evaluated in the formed components. The work, through numerical simulations and experimental analyses, investigates the process capabilities of ISF to form the EDD steel sheets in terms of formability, thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness to ascertain the scope of the proposed process.

In this work, the plastic behavior of an interstitial-free steel sheet was first evaluated by standard uniaxial tensile and hydraulic bulge tests to reproduce the intermediate and high straining levels commonly observed in sheet metal forming processes. Next, a simple procedure was proposed to obtain an equivalent work-hardening curve, representing the high strain domain instead of the conventional uniaxial tensile data. This procedure involves an anisotropy parameter calculated based on Hill's quadratic criterion using the measured r-values in the rolling and transverse sheet directions. Under the assumption of an isotropic work-hardening, the equivalent curve is defined from the true stress and true thickness plastic-strain results of the hydraulic bulge test. The transformed data were fitted to usual power-law type equations to obtain an adequate work-hardening description for finite element numerical simulation purposes. Based on the goodness-of-fit measures, namely, R-squared, root-mean-square error, and root-mean-square of residual percentage, the combined Swift–Hockett–Sherby equation has proved to be the most suitable choice to describe the plastic behavior of the investigated interstitial-free steel under both intermediate and high strains conditions.

Improving existing technological processes is an important stage in the development of all industries. As a consequence, this article is devoted to the analysis of the process of flanging round holes in sheet steel. The existing typical technological process, with a detailed analysis, gives grounds for substantiating the idea of an innovative solution. Changing the sequence of the traditional flanging method will ensure high productivity and material savings. Of the many promising methods of metal forming by pressure, which include flanging of round holes, two are given for comparison: the traditional one and the improved one. The methodology of the traditional direction, worked out over the years, provides for a clear sequence of the technological process using tools for marking, centering, making a hole and using tools for flanging. The final, after the previous operations of marking the centers of the holes, punching, making holes, is the flanging stage. The tapered punch (usually a metal rod) prevents the small-diameter hole from deviating from the marking lines and ensures the centering of the punch-blank-matrix system. Following the above steps, the conventional workflow involves positioning the workpiece over the surface of the punch hole to guide the tool in the desired direction. For the manufacture of a flanged hole, a special sharpening of the working part of the punch is performed so that the diameter of the central part of the tool is equal to the difference between the diameters of the guide hole of the matrix and the inner diameter of the workpiece of the part. To avoid further displacement of the hole, the workpiece is centered by placing it on the die and the next operation is supposed to lower the punch to flang the hole. As a result, the article touches on the topic, taking into account the widespread use of thin sheet metal, including in the agricultural sector, the feasibility of using an innovative idea to improve the technological process associated with the processing of sheet material, namely thin metal sheets. It is advisable to note that, for example, a material is considered that is characterized by its versatility, namely steel. Despite numerous sources devoted to the study of improving the flanging technological process, there are a number of issues, in particular, the extension of this direction to numerous varieties of metal materials that have surfaces with and without coating, various thicknesses within thin-walled rolled products. The most significant result is the improved technological process of flanging will find application in the system of efficient servicing of agricultural machinery.

The 3D curved part rolling method based on the rigid arc-shaped rollers is a novel sheet metal rolling process to rapidly manufacture 3D surface parts for various parameters. The flow of material inside the sheet metal is complicated during the cold rolling forming process of the 3D curved parts, whose quality of products is sensitive to process parameters. The work analyzed the friction force for the sheet metal inside the roll gap during rolling as well as the reason for the instability of the forming process. The instability of the forming process significantly affected the forming accuracy of curved parts. Therefore, the method of using an auxiliary plate was proposed to improve the stability of the rolling process. The finite element numerical simulation models were established for two rolling processes, with and without the auxiliary plate, and the forming errors of the two processes were computed. The numerical simulation results showed that the rolling process with the auxiliary plate can obtain a more stable rolling process, and the forming error of formed curved parts was smaller. The reliability of the numerical simulation results was verified through experiments.

Single-point incremental forming (SPIF) is a flexible and affordable process suitable for small-batch customized productions. Typically, metal alloys with a high strength-to-weight ratio exhibit a low formability at room temperature. The feasibility of conducting the SPIF process on these alloys at high temperatures is in demand. In this study, the SPIF process of the AA6061 aluminum alloy sheet at the temperature range of 25–400 °C is experimentally and numerically investigated. In this regard, a fixture was designed and fabricated to perform the SPIF process using heating cartridges for warming up the sheet metal homogenously. The effect of the temperature, the vertical pitch, the feed rate, and the lubrication type on the formability of the AA6061 sheet in SPIF of a truncated cone was studied. According to the results, by increasing the forming temperature from 25 to 400 °C, the formability of the truncated cone with the wall angle of 60° is improved by 528%. Moreover, using an appropriate combination of the process parameters, a truncated cone with a wall angle of 65° can be successfully formed up to the forming depth of 44 mm with a formability enhancement of 642% compared to the cold SPIF. For further understanding of the mechanics behind this improvement, the influence of the temperature on the formability was numerically studied. It was observed that the vertical pitch and the lubrication type have a significant interaction effect on the maximum achievable forming depth and the surface finish. It was also concluded that the effect of the feed rate on the formability is negligible for the considered range of the process parameters.

To improve the thickness uniformity of sheet metal parts in incremental forming method based on a virtual auxiliary body, the effect of relevant parameters on the thickness uniformity was studied from both overall and local perspectives. Finite element (FE) method was used to carry out the single-factor and two-level factorial experiments, in which standard deviation of the thickness of section nodes was used as a response to analyzing the effect of factors on the thickness uniformity. First, the mean effects of each factor were obtained and the factor levels of factorial experiments were determined through a single-factor experiment. Then, the interaction effect between factors was analyzed and the optimal combination of parameters was determined through factorial experiments. From the FE analysis, it was found that the desired forming angle and the gap at the bottom have obvious mean effects and interactional effects on the thickness uniformity. Finally, the initial and optimal parameters were used for forming experiments. In the forming experiments, the overall and local thickness standard deviations of section nodes were reduced from 0.194 to 0.088 mm and from 0.149 to 0.081 mm, respectively, which means that the optimized parameters can effectively improve the thickness uniformity of sheet metal parts.