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This study examines the process by which the components of project management influence the sustainable development effectiveness of PetroMasila personnel in Yemen. The quantitative technique was utilized in the current investigation. The online survey was utilized to gather information from 342 workers working in departments involved in project-related activities. The Structural Equation Model (SEM) was used in Smart-PLS Software to analyze the data. This study revealed that project management and its following aspects, including planning management and cost management had a substantial and favorable impact on the oil industry's capacity for sustainable growth. The study model explained 32% of the variance in sustainable development effectiveness. In addition, this paper outlines limitations and further research.

As a non-conventional drilling process, friction drilling has been successfully used for sheet metal hole-making, increasing the effectiveness of thread length, and screw coupling. The main challenges and obstacles to the implementation of the friction drilling process for difficult-to-machine materials are excessive tool wear and inadequate product quality. This study aims to investigate the effect of the two most significant parameters namely spindle speed and feed rate on bushing formation quality and drilling tool performance, and determination of optimal process parameters experimentally and numerically, both. Firstly, by using the full factorial method the experiments are designed. Then, the collected experimental data are statistically evaluated by analysis of variance (ANOVA) using the MINITAB tool. The findings reveal that spindle speed is a more significant parameter than feed rate that intensively affects machining and drilling tool performance. Moreover, the resultant optimum parameters combination for AISI304 is spindle speed 1000 rpm and feed rate 105 mm/min, for Ti-6Al-4 V is spindle speed 1000 rpm and feed rate 145 mm/min, and for Inconel718 is spindle speed 1500 rpm and feed rate 145 mm/min. Above all else, because of the good creep-rupture resistance of Inconel718, this material presents a great reaction concerning the high quality of formed-bush and drilling tool performance. Contrariwise, the low thermal conductivity of Ti6Al-4 V causes insufficient heat transfer throughout the workpiece, poor product quality, and severe tool wear. On the other hand, the effects of feed rate and spindle speed on the distribution of thermal stress and heat generation on workpieces are studied numerically. This proves the great potential of finite element analysis for an optimization study.

This paper explains and demonstrates the capabilities of Metal Additive Manufacturing (MAM) technology in producing intricate stent structure with a customise design by using ASTM F75 Cobalt-Chromi...

This paper evaluates and demonstrates the methods for additively manufactured stent and the use of material ASTM F75 Cobalt-based superalloy (CoCrMo) by evaluating the chemical content, hot isostat...

In metallurgical view point, difficult-to-machine materials are named as materials which have high work-hardening, low thermal conductivity, and great toughness. Since recently special attention has been paid to the difficult-to-machine materials in different applications, an excellent potential for product fabrication is proposed by friction drilling. However, the main problem is encountered when friction drilling of difficult-to-machine materials are poor machining performance and short tool life. Due to the wide range of applications for difficult-to-machine materials AISI304, Ti-6Al-4 V, and Inconel718 in different industries, this paper is concerned with thermo-mechanical modelling of friction drilling process on these materials using drilling tool of WC which contributes to gain an in-depth understanding of how friction in workpiece-tool interface generates the heating. It can help to find out effects of frictional heat generation on bushing formation and drilling tool, and how to improve quality of bushing formation and prolong tool life. In order to verify the numerical simulated results and evaluation of surface quality and required thrust force, an experimental validation is also conducted. A comparison of the predicted and experimental results reveal that the main reasons of uniform bushing formation quality and low tool degradation for friction drilling of Inconel718, and non-uniform bushing formation quality and high tool degradation for friction drilling of Ti-6Al-4 V are high work hardening of Inconel718 and low thermal conductivity of Ti-6Al-4 V. Moreover, the bushing formation cycle time, where the maximum contact between drilling tool and bushing hole-wall occurs, is the most critical step time in friction drilling process that causes maximum tool wear.

Equal channel angular rolling (ECAR) is a severe plastic deformation method that coated plastic deformation of sheets. This research aims to analyse the effects of equal channel angular rolling fee...

This paper explains and demonstrates the capabilities of metal additive manufacturing (MAM) technology in producing intricate stent structure with a customise design by using ASTM F75 cobalt chromi...

Thrust force and torque applying in friction drilling contain some important information related to sufficient heat generation which can improve product quality and reduce tool wear. This concern becomes more challengeable when friction drilling is applied on difficult-to-machine materials. In the present study, temperature, thrust force, and torque for friction drilling of difficult-to-machine materials namely AISI304 and Ti-6Al-4V and Inconel718 are measured and analyzed. It contributes to provide an enhanced understanding of how friction in workpiece-tool interface increases the temperature. Subsequently, the sufficient heat generation, the effective thrust force, and torque that are needed to form a proper bushing with optimum features can be predicted. It is found that increasing in number of drilled holes reduces the quality of bushing shape. It is observed that thermal conductivity of workpiece material has significant effect on bushing formation quality. The findings indicate that better bushing formation and longer tool life are obtained from friction drilling of Inconel718. The microstructural changes of workpiece and tool wear are also analyzed and a relationship between them, temperature, thrust force, and torque, is explored. The maximum tool wear is observed on conical region where the process is in critical cycle time and temperature is on peak point.

The application of developed thermal models has demonstrated that parameters, such as power, scanning velocity and spot diameter of laser beams have considerable effects on the formation of weld pools. The properties of the weld metal are heavily dependent on the solidification microstructure, and an accurate prediction of the weld pool solidification requires consideration in both the thermodynamics and kinetics of solidification. The computations we presented for a transient three-dimensional model show the aspects of weld pool formation and solidification in a quantitative manner. Our focus was the examination of heat transfer and fluid flow analysis in laser micro-welding of thin stainless-steel sheet (SUS304) using the computational fluid dynamics (CFD) approach. In this research work, a useful linkage between the laser micro-welding parameters and the geometry of the micro-weld can be derived from the results, and informative guidance was achieved as to how the width, depth and length of the weld pool differ during laser micro-welding as a function of spot diameter, scanning velocity and laser power. The simulation results have been compared with two sets of experimental data to predict the weld bead geometry and solidification pattern made on thin stainless steel sheet using a continuous wave (CW) fibre laser. The reasonable agreement between the simulated and experimental results, demonstrates the reliability of the computed model, and the results can be used to determine the laser micro-welding conditions necessary to achieve an appropriate target microstructure. However, the results allow estimation of acceptable ranges of welding variables, to attain the required micro-weld geometry.

In practice, computer simulations cannot be perfectly controlled because of the inherent uncertainty caused by variability in the environment (e.g., demand rate in the inventory management). Ignoring this source of variability may result in sub-optimality or infeasibility of optimal solutions. This paper aims at proposing a new method for simulation–optimization when limited knowledge on the probability distribution of uncertain variables is available and also limited budget for computation is allowed. The proposed method uses the Taguchi robust terminology and the crossed array design when its statistical techniques are replaced by design and analysis of computer experiments and Kriging. This method offers a new approach for weighting uncertainty scenarios for such a case when probability distributions of uncertain variables are unknown without available historical data. We apply a particular bootstrapping technique when the number of simulation runs is much less compared to the common bootstrapping techniques. In this case, bootstrapping is undertaken by employing original (i.e., non-bootstrapped) data, and thus, it does not result in a computationally expensive task. The applicability of the proposed method is illustrated through the Economic Order Quantity (EOQ) inventory problem, according to uncertainty in the demand rate and holding cost.

Designing a production process normally is involved with some important constraints such as uncertainty, trade-off between production costs and quality, customer’s expectations and production tolerances. In this paper, a novel multi-objective robust optimization model is introduced to investigate the best levels of design variables. The primary objective is to minimize the production cost while increasing robustness and performance. The response surface methodology is utilized as a common approximation model to fit the relationship between responses and design variables in the worst-case scenario of uncertainties. The target mean ratio α is applied to ensure the quality of the process by providing the robustness for all types of quality characteristics and with a trade-off between variability and deviance from the ideal point. The Lp metric method is used to integrate all objectives in one overall function. In order to estimate target value of the quality loss by considering production tolerances, the process capability ratio (Cpm) is applied. At the end, a numerical chemical mixture problem is served to show the applicability of the proposed method.

In spite of the wide improvement in computer simulation packages, analyzing, and optimizing the simulation model, particularly under uncertainty can still be computationally expensive and time-consuming. This paper aims to tackle these features by proposing a comprehensive methodology applied to black-box stochastic simulation models under uncertainty. For this purpose, the common surrogate model as Kriging metamodel is served to fit the simulation input–output data produced by Latin hypercube sampling experimental design. Taguchi terminology of robust design enables the optimization methods to control uncertainty and uncontrollable environmental factors. So as to formulate robust counterpart optimization, three different models in the class of dual-response surface are integrated with metamodel and robust design. Leave-one-out cross-validation is applied to validate the Kriging metamodel. Finally, a numerical case study as a direct speed control of dc motor under uncertainty is served to demonstrate the applicability of the proposed method in real engineering problems. This simplified and practical mechatronics case illustrates how the proposed procedure can be expanded for analyzing and optimizing the real complex systems.

Laser forming is a flexible control process that has a wide spectrum of applications; particularly, laser tube bending. It offers the perfect solution for many industrial fields, such as aerospace, engines, heat exchangers, and air conditioners. A high power pulsed Nd-YAG laser with a maximum average power of 300 W emitting at 1064 nm and fiber-coupled is used to irradiate stainless steel 304 (SS304) tubes of 12.7 mm diameter, 0.6 mm thickness and 70 mm length. Moreover, a motorized rotation stage with a computer controller is employed to hold and rotate the tube. In this paper, an experimental investigation is carried out to improve the laser tube bending process by enhancing the absorption coefficient of the material and the mechanical formability using laser softening heat treatment. The material surface is coated with an oxidization layer; hence, the material absorption of laser light is increased and the temperature rapidly rises. The processing speed is enhanced and the output bending angle is increased to 1.9° with an increment of 70% after the laser softening heat treatment.

Additive manufacturing, also known as three-dimensional (3D) printing, is the process of developing 3D products in a layer-by-layer manner using filament as a material feedstock to create a solid structure. Owing to its unique properties and advantages, which include biodegradability and printing speed, polylactic acid is one of the most common 3D printing extrusion materials. While a considerable attention has been paid to the manipulation of process parameters in order to achieve desired finished product quality, to date less research has been performed on improving the hardware systems of low-cost 3D printers. This study focuses on fabricating the 3D printer nozzle parts, with an emphasis on die angle, nozzle diameter, liquefier design, and insulator composition. Modifying the properties of these components from the conventional nozzle, it is possible to optimize the stability and accuracy of the extrusion process, leading to better-quality printed products. To demonstrate the capability of the new nozzle, its tensile and compressive strengths were compared to those of a conventional nozzle. The obtained results proved that the proposed augmentations to the nozzle system lead to finished products with improved mechanical properties.

Nowadays, process optimization has been an interest in engineering design for improving the performance and reducing cost. In practice, in addition to uncertainty or noise parameters, a comprehensive optimization model must be able to attend other circumstances which might be imposed in problems under real operational conditions such as dynamic objectives, multi-responses, various probabilistic distribution, discrete and continuous data, physical constraints to design parameters, performance cost, computational complexity and multi-process environment. The main goal of this paper is to give a general overview on topics with brief systematic review and concise discussions about the recent development on comprehensive robust design optimization methods under hybrid aforesaid circumstances. Both optimization methods of mathematical programming based on Taguchi approach and robust optimization based on scenario sets are briefly described. Metamodels hybrid robust design is discussed as an appropriate methodology to decrease computational complexity in problems under uncertainty. In this context, the authors’ policy is to choose important topics for giving a systematic picture to those who wish to be more familiar with recent studies about robust design optimization hybrid metamodels, also by attending real circumstances in practice. In particular, production and project management are considered as two important methodologies that could be improved by applications of advanced robust design combining with metamodel methods.

Nowadays, laser tube bending process has become commonly used in laser material processing and fabrication fields because of its ability to produce such forms and shapes that cannot be achieved by normal mechanical bending tools. The process can avoid and overcome most of bending defects like wall thinning, wrinkling, spring back and ovalization. This investigation focused on the experimental, analytical modeling, and numerical simulation to give more understanding of the process. In this work a high power pulsed Nd-Yag laser of maximum average power laser 300 (W) emitting at 1064 nm and fiber coupled has been used to irradiate stainless steel 304 tubes of diameter 12.7 mm, 0.6 mm thickness and 60 mm in length. An analytical model has been used to determine the bending angle by using Matlab program software. The changes of material specification during the laser tube bending process due to the temperature rise has been studied and the analytical model has been modified and enhanced. Particle Swarm Optimization (PSO) was used to optimize the analytical and experimental results and reduce the mean absolute error.

Aluminum-silicon (Al-Si) alloys are an important class of materials, alloys which have great interested in wide industries whether in light or heavy industries, due to their superior properties like high strength to weight ratio, corrosion resistance, and excellent castability. The mechanical strength and the effect of modifying alloys have been studied. To evaluate the strength and revealed the structural of these alloys, the Instron tensile and Shimidzu Vickers hardness tester have been employed while the fracture surfaces have been observed by Scanning electron microscope (SEM). From results obtained, the microstructure of Al-Si with TiB2 has much finer microstructure compared to unfine Al-Si alloy. It showed that the eutectic silicon microstructure in Al-Si alloy changed from needles-look or acicular to fine grain size or globular when the added of TiB2. The mechanical studies showed that the ductility of Al-Si alloy was much lower in the absence of grain refiner, TiB2. The tensile strength of unrefined Al-Si and Al-Si with 6 wt.%TiB2 as grain refinement were recorded 275 and 312 MPa respectively. The hardness value for the unrefined Al-Si alloy also shows less compared with Al-Si with grain refiner, 6 wt.%TiB2, which are 74 and 78 MPa. This showed the results were significant improvements in mechanical properties have been obtained with the use of TiB2 as grain refiner to Al-Si alloy.

Friction drilling is a chipless hole-making process that utilizes a rotating conical drilling tool to penetrate and create a hole and bushing without generating chip. This process is still not widely used even though it has many significant advantages. There are unanswered questions in finite element models to analyze the stress, temperature and large deformation of the workpiece and to predict the drilled hole and formation of bushing. With modern computing technologies the numerical simulation has proven to be an effective tool for this issue. In the present study, a three-dimensional finite element model (FEM) has been developed to simulate the stress, plastic strain and temperature distribution in friction drilling of aluminum alloy. The friction drilling process was experimentally conducted using a drilling tool without flutes. The numerical results indicated that high stress occurs at the tool contact surface and adjacent region in the primary penetration. It was confirmed that the distribution of stress and temperature demonstrate the phenomenon of friction heat and softens the work-material in friction drilling. The numerical simulated results have proven that the developed finite element model is effective to predict stress evolutions and thermal histories in friction drilling of non-ferrous material.

Silicon, being a material which allows light transmission beyond visible spectrum is a good candidate for the integration of microfluidic and optical devices. The lack of rapid prototyping method in particular mechanical-based micromachining process for silicon device processing is due to the brittleness property of silicon. Silicon fails or breaks without significant deformation when subjected to tension or stress. This study presents an experimental investigation on surface of micro-machined single-crystal silicon with (111) orientation. Full immersion slot milling was conducted using solid cubic boron nitride (CBN) micro-end mills. Influences of cutting parameters including spindle speed, feed rate and axial depth of cut on surface roughness were analyzed. Surface and subsurface characterization studies show that the primary material removal mode is ductile or partial ductile using lower feed rate.

Fused Deposition Modeling (FDM) or also known as RepRap (Replicating Rapid Prototyper) is a technology that is synonym with 3D printing. This technology has entered a new era with an increasing demand among the community. It has grown commercially in the market of open-source system and it is relatively low cost. Many efforts have been put towards the development of the system in both hardware and software to increase the quality and the performance. The research highlights the development of a new nozzle to evaluate the performance on dimensional accuracy in comparison to the original nozzle. The nozzle emphasizes the die angle for the polylactic acid (PLA) material, the liquefier design which provide constant heat in the liquefier chamber, as well as insulator for the liquefier using highly insulated material. The dimensional accuracies of both nozzles were compared where the result showed that the new nozzle provided better accuracy and stability on the extruding PLA material.

Open-source 3D printer has been widely used for fabricating three dimensional products. However, this technology has some drawbacks that need to be improved such as accuracy of the finished parts. One of the factors affecting the final product is the ability of the machine to extrude the material consistently, which is related to the flow behavior of the material inside the liquefier. This paper observes the pressure drop along the liquefier by manipulating the nozzle die angle from 80° to 170° using finite element analysis (FEA) for polymethylmethacrylate (PMMA) material. When the pressure drop along the liquefier is varied, the printed product also varies, thus providing less accuracy in the finished parts. Based on the FEA, it was found that 130° was the optimum die angle (convergent angle) for extruding PMMA material using open-source 3D printing.

Commercial finite element software that uses default hardening model simulation is not able to predict the final shape of sheet metal that changes its dimensions after removing the punch due to residual stress (strain recovery or springback). We aimed to develop a constitutive hardening model to more accurately simulate this final shape. The strain recovery or balancing of residual stress can be determined using the isotropic hardening of the original elastic modulus and the hardening combined with varying degrees of elastic modulus degradation and the size of the yield surfaces. The Chord model was modified with one-yield surfaces. The model was combined with nonlinear isotropic&ndash, kinematic hardening models and implemented in Abaqus user-defined material subroutine for constitutive model (UMAT). The Numisheet 2011 benchmark for springback prediction for DP780 high-strength steel sheet was selected to verify the new model, the Chord model, the Quasi Plastic-Elastic (QPE) model, and the default hardening model using Abaqus software. The simulation of U-draw bending from the Numisheet 2011 benchmark was useful for comparing the proposed model with experimental measurements. The results from the simulation of the model showed that the new model more accurately predicts springback than the other models.

Sheet metals forming process is widely used in consumer and industrial products. However, the conventional sheet metal forming has low flexibility and product quality. It also prolongs the time-to-market in producing prototype products that required low costs. Single point incremental forming (SPIF) is one of relatively new sheet metal forming process. The increase interest in new techniques for forming processes and the usage of robotics in the industry has created more researches on the SPIF. Robot-based SPIF is a method of deforming a sheet metal to create designed workpieces by utilising a forming tool that attached to an industrial robot. In this present work, an optimization study for combination of process parameters in robot-based single point incremental forming of aluminum alloy sheet was experimentally investigated using Taguchi method to achieve an excellent surface roughness. A number of forming experiments were conducted using the L18 orthogonal array. Analysis of Variance (ANOVA) was used to identify the most significant process parameters affecting the surface roughness. The results analysis indicates that the optimum process parameters for surface roughness are obtained as 0.3 mm of step size, 150 mm/s of robot speed and 45 degree of wall angle. The most significant process parameter is step size and followed by robot speed. The study revealed the surface quality could be improved by proper selection of process parameters.

In spite of the wide improvements in computer simulation packages, many complex simulation models, particularly under uncertainty, may be inefficient to run in terms of time, computation, and resources. To address such a challenge, integrating metamodels and robust design optimization has been applied. In the current paper, a systematic comparative study is implemented to evaluate the performance of three common metamodels, namely polynomial regression, kriging, and radial basis function. The required experiments are designed by different space-filling methods including the orthogonal array design and three forms of Latin hypercube sampling such as randomized, maximin, and correlation approaches. Although, the impact of sample size on the performance of metamodels in robust optimization results are investigated. All methods are analyzed using five two-dimensional test problems and one engineering problem while all of them are considered in two forms that are expensive (with a small sample size) and semi-expensive (with a large sample size). Uncertainty is assumed in all problems as a source of variability, so all test problems are conducted in the format of robust optimization in the class of dual response surface in order to estimate robust Pareto frontier. The performances of methods are studied in two terms of accuracy and robustness. Finally, the results of comparison, an applicable guideline is provided to aid the practitioners in selecting the appropriate combination of metamodels and sampling design methods for investigating set of robust optimal points (estimated Pareto frontier) in simulation–optimization problems under uncertainty.

In the present study, a three-dimensional finite element model has been developed to simulate the temperature, stress and deformation fields in continuous wave (CW) laser micro-welding of thin stainless steel sheet. The welding deformation was experimentally evaluated using a single-mode fiber laser with a high-speed scanning system. Application of developed thermal model demonstrated that the laser parameters, such as laser power, scanning velocity and spot diameter have a significant effect on temperature field and the weld pool. In the case of welding deformation, numerical simulation was carried out by an uncoupled thermo-mechanical model. The welding stress and deformation are generated by plastic deformation during the heating and cooling periods. It was confirmed that the residual stress is higher than yield strength and has strongest effect upon the welding deformation. The numerical simulated results have proved that the developed finite element model is effective to predict thermal histories, thermally induced stresses and welding deformations in the thin material.

Laser forming of materials can help produce the desired shapes from sheets or tubes, which is not possible through conventional methods. Molds, dies, and external force are not needed for the laser forming of materials. Furthermore, the process is flexible and can be controlled by making changes to the materials, their geometry, and the laser parameters, either individually or in combination with each other. Investigations into laser tube bending are scarce in the literature pertaining to this field of study despite its potential and industrial importance. In contrast, much research has been conducted on laser sheet forming, which employs the same mechanism. In this study, laser tube bending is compared with laser sheet forming in order to develop a better understanding of the laser forming process. This review elucidates upon the mechanisms employed in laser forming (in general) and laser tube bending (in particular). A number of investigation methods are reviewed and analytical models of the process are also described. The principle of laser tube bending is explained, and the influence of various parameters (such as materials, geometry, laser, edge, and cooling effects) on the process is analyzed. Additionally, large tubes bending and preloading, or laser assistance, are examined.

Aluminium-copper (Al-Cu) alloys is the one of most Metal Matrix Composites (MMCs) have important high-strength Al alloys. The aluminium (Al) casting alloys, based on the Al-Cu system are widely used in light-weight constructions and transport applications requiring a combination of high strength and ductility. In this research, Al-Cu master alloy was reinforced with 3 and 6wt.% titanium diboride (TiB2) that obtained from salts route reactions. The salts used were were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). The salts route reaction process were done at 800 °C. The Al-Cu alloy then has characterized on the mechanical properties and microstructure characterization. Salts spray fog test and Gamry-electrode potentiometer instruments were used to determine the corrosion rate of this alloys. From results obtained, the increasement of 3wt.%TiB2 contents will decrease the value of the corrosion rate. In corrosion test that conducted both of salt spray fog and Gamry-electrode potentiometer, the addition of 3wt.%TiB2 gave the good properties in corrosion characterization compare to Al-Cu-6wt.%TiB2 and Al-Cu cast alloy itself. As a comparison, Al-Cu with 3wt.%TiB2 gave the lowest value of corrosion rate, which means alloy has good properties in corrosion characterization. The results obtained show that in-situ Al-Cu alloy composites containing the different weight of TiB2 phase were synthesized successfully by the salt-metal reaction method.

Laser assisted micro milling (LAMM) is one of the techniques used to enhance the ability to manufacture microscale products. Laser is used to preheat the workpiece materials prior the machining process. Compared with conventional machining, LAMM is a green manufacturing method due to reduction in cutting force during machining process. However, it needs to be controlled to avoid the melting and changing of materials properties. Determining the processing parameters and their effects on the processing characteristics, temperature measurement and the laser spot-to-cutting tool distance are crucially important. In this study, finite element analysis using ANSYS software was used to predict the heat distribution to characterise the melting and heat affected zone formation. The data at the centre of laser spot were recorded to obtain the appropriate distance between laser spot-to-cutting tool. From the results, the estimations of laser spot-to-cutting tool distance of Inconel 718 together with the allo...

Tensile and wear properties of aluminium (Al) based metal matrix composites (MMCs) was prepared by added titanium diboride (TiB2) with in-situ technique by salt route. The salts used in this research were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). Nanocomposite samples were prepared by casting technique associated with incorporating 3 and 6 wt.% of TiB2 into matrix of Al-6wt.%Cu. Instron and wear tests machine were used to characterize the tensile and wear Al-Cu alloys properties. Results showed that increase in TiB2 content gave the high properties of tensile and wear behavior. The study indicates that TiB2 particles have giving improvement the wear performance of the Al–6wt.%Cu alloy. For a constant load and sliding speed, the wear rate decreases as a function of amount of TiB2 in the composite. The wear rate decrease with increasing in wt.% TiB2 particles for the all loads applied. However, addition of TiB2 particle to the Al–6 wt%.Cu matrix has show the coefficient value of wear decreases regardless of applied load. Study of the wear surfaces both alloy and composites by optical microscope suggests that the improvement in wear resistance is mainly due to the formation of finer groove or debris by content of TiB2.

Addition of hydroxyapatite (HA) can enhance the bioactivity of the common metallic implant due to its similarity with natural bones and teeth. In this investigation, high velocity oxy-fuel (HVOFT) technique was used to deposit titanium-hydroxyapatite (Ti-HA) composite on stainless steel substrate plate with different percentage of HA for biomedical applications. The aim of this research is to investigate the mechanical properties of Ti-HA coating such as hardness, adhesion strength and wear behaviour. The hardness and strength was determined by using SHIMADZU-microhardness Vickers tester and PosiTest AT portable adhesion tester respectively. The wear test was performed by using pin-on-disk equipment and field emission scanning electron microscope (FESEM) used to determine the extent of surface damage. From the results obtained, mechanical properties such as hardness and adhesion strength of titanium (Ti) coating decreased with the increased of HA contents. Meanwhile, the coefficient of friction of Ti-10% HA coating shows the highest value compare to others as three-body abrasion had occurred during the test.

Difficult-to-machine materials are metals that have great toughness, high work-hardening, and low thermal conductivity. Friction drilling of difficult-to-machine materials is a technically challenging task due to the difficulty of friction drilling, leading to excessive tool wear, which adversely affects surface integrity and product performance. In the present study, the microstructural changes of workpieces and tool wear for friction drilling of AISI304, Ti-6Al-4V, and Inconel718 are characterized. It helps to have an in-depth understanding of heat generation mechanics by friction and the mechanism of the friction drilling process. The study contributes to providing an enhanced microstructural characterization of workpiece and tool conditions, which identifies the material behavior and shows how it affects the bushing formation quality and drilling tool performance. The results reveal that the abrasive wear is mostly observed in the conical region of the tool, which has maximum contact with hole-wall. Moreover, the low thermal conductivity of Ti-6Al-4V increases frictional heat generation severely, and reduces product quality and tool life subsequently.

Scaffold or porous architectured structure is essential in biomedical application for cell growth or for mass reduction if to be used in automotive and aerospace applications. The structure was once impossible to fabricate but now viable using additive manufacturing techniques. However, in order to reduce weight structure and save on materials using porous structure, strength is one key feature must be maintained to serve the function. The aims of the study are to compare the part strength with different cell repetition and porosity (ranging 56% to 70.45%), and also to determine pattern of stress concentration in different unit cell size. In this study, cubic scaffold-based structures with critical porosity range were simulated using ABAQUS. From the simulation it can be observed generally that strength will reduce with higher porosity, while 58.96% of porosity showed less stress concentration. For each porosity, stress concentration and deflection can be observed and compared. The result of the study is important to help designer to choose suitable design and porosity prior to fabrication.

Friction drilling is an unexplored manufacturing process to produce holes in thin-walled sheet metals. In this study, the effects of process parameters in friction drilling of austenite stainless steel investigated experimentally and statistically. It was confirmed, sufficient heat generation, which cause to better bushing shape and height, acceptable drilled-hole diameter and lowest roundness error result from low spindle speed and high feed rate. It was obtained, although effect of feed rate on hole-wall thickness was negligible; spindle speed has significant effect on that which is inverse from spindle speed effect on bushing height. Moreover, micro-hardness reduced gradually away from the drilled-hole edge. Observing on tool shape and wear damage using optical microscope and scanning electron microscope quantifies effects of spindle speed and feed rate on tool performance and tool wear characteristics. Results indicate that better performance of drilling tool obtained from lower spindle speed and high feed rate.

Laser microwelding has been an essential tool with a reputation of rapidity and precision for joining miniaturized metal parts. In industrial applications, an accurate prediction of weld bead geometry is required in automation systems to enhance productivity of laser microwelding. The present work was conducted to establish an intelligent algorithm to build a simplified relationship between process parameters and weld bead geometry that can be easily used to predict the weld bead geometry with a wide range of process parameters through an artificial neural network (ANN) in laser microwelding of thin steel sheet. The backpropagation with the Levenberg-Marquardt training algorithm was used to train the neural network model. The accuracy of neural network model has been tested by comparing the simulated data with actual data from the laser microwelding experiments. The predictions of the neural network model showed excellent agreement with the experimental results, indicating that the neural network model is a viable means for predicting weld bead geometry. Furthermore, a comparison was made between the neural network and mathematical model. It was found that the developed neural network model has better prediction capability compared to the regression analysis model.

The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in term of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm.

The development of advanced materials with superior high thermal properties and high specific strength has led to new metal matrix composites (MMCs) as a great attractive material in electrical and electronic industries. In order to manufacture more practical component from MMCs, a tech-nique for joining MMCs to other similar composites or monolithic materials is strongly required. Therefore, the reliable and economic joining technique is investigated to increase the applications of MMCs. In this study, the overlap welding of pure aluminum and super thermal conductive (STC) aluminum-graphite composite was experimentally and numerically investigated by using a pulsed Nd:YAG laser. In order to discuss the welding of dissimilar materials with different thermophysical properties, the temporal change of heat input was controlled by arranging the laser pulse waveform. The porosities and bumps were observed as the remarkable weld defects in the welding process without a pulse control. On the other hand, the weld bead was largely free of defects, and a size of bump was relatively small with the appropriate controlled pulse waveform. It was clarified that the laser welded joint of an aluminum and a STC aluminum-graphite composite could be successfully achieved with the better weld penetration stability by the appropriate controlled pulse waveform.

Fused deposition modeling (FDM) is one of the Rapid Prototyping (RP) technologies. The 3D Printer has been widely used in the fabrication of 3D products. One of the main issues has been to obtain a high quality for the finished parts. The present study focuses on the effect of nozzle diameter in terms of pressure drop, geometrical error as well as extrusion time. While using polylactic acid (PLA) as a material, the research was conducted using Finite Element Analysis (FEA) by manipulating the nozzle diameter, and the pressure drop along the liquefier was observed. The geometrical error and printing time were also calculated by using different nozzle diameters. Analysis shows that the diameter of the nozzle significantly affects the pressure drop along the liquefier which influences the consistency of the road width thus affecting the quality of the product’s finish. The vital aspect is minimizing the pressure drop to be as low as possible, which will lead to a good quality final product. The results from the analysis demonstrate that a 0.2 mm nozzle diameter contributes the highest pressure drop, which is not within the optimum range. In this study, by considering several factors including pressure drop, geometrical error and printing time, a 0.3 mm nozzle diameter has been suggested as being in the optimum range for extruding PLA material using open-source 3D printing. The implication of this result is valuable for a better understanding of the melt flow behavior of the PLA material and for choosing the optimum nozzle diameter for 3D printing.

Laser micro-welding has proven to be a very successful tool for micro-joining in the electrical and electronic industries, where the miniaturization, the high strength and the high heat resistance are constantly requested. Recently, a flexible printed circuit (FPC) is expected as a new connection technology between electrical conductors according to the improvements of reliability and controllability with the diversification of the design concept. In this technology, it is required to weld a several tens μm thickness of FPC and a several hundreds μm thickness of metal electrode. This material combination accompanies the difficulty to control the welding phenomenon due to the differences of thermal property and heat capacity. As a good alternative, laser micro-welding has advantages of non-contact tool, low heat distortion and consistent weld integrity. In this study, the overlap welding of thin copper circuit on a polyimide film and a thick brass electrode was experimentally and numerically investigated by using a pulsed Nd:YAG laser. In addition, the shearing stress of overlap welding was evaluated with and without the control of pulse waveform, which can provide a well-directed controlling of the heat input with high energy density. The results showed that a porosity was observed as the major weld defect in the welding process without a pulse control. However, the appropriate controlled laser pulse configuration of micro-welding could remove the weld defects in the molten zone, improve the weld penetration stability and increase the weld strength. The potential benefits of controlled pulse waveform were discussed for the direct laser micro-welding process. It is clarified that the direct laser micro-welding of a thin copper circuit on a polyimide film and a thick brass electrode could be successfully achieved by appropriate controlled pulse waveform and heat input.

Problem statement: The miniaturization of components plays an important role for manufacturing in electrical and electronic industries. The joining technology of thin metal sheets has been strongly required. Laser welding with micro-beam and high-speed scanning is a promising solution in micro-welding, because it has high-potential advantages in welding heat sensitive components with precise control of heat input and minimal thermal distortion. Approach: In this study, the characteristics of laser micro-welding of thin stainless steel sheets by using a single-mode CW fiber laser with high-speed scanning system were experimentally investigated. Results: It was clarified that the welding bead width and depth increased with increasing the scanning velocity under a constant energy density condition and high efficient welding was expected by using high-speed laser scanning with Galvano scanner. The utilization of shielding gas was very effective to obtain smooth fusion bead and the combination of micro beam spot and high-speed laser scanning made it possible to obtain good overlap welding of ultra-thin stainless steel sheets. Conclusion: A faster and high quality welding could be achieved by using a single-mode fiber laser with micro-beam and high-speed scanning.

Laser tube bending is a new technique of laser material forming to produce a complex and accurate shape due to its flexibility and high controllability. Moreover, the defects during conventional tube forming such as thinning, wrinkling, spring back and ovalization can be avoided in laser tube bending process, because there is no external force used. In this paper an analytical investigation has been conducted to analyses the effects of average laser power and laser scanning speed on laser tube bending process, the analytical results have been verified experimentally. The model used in this study is in the same trend of the experiment. The results show that the bending angle increased with the increasing of average laser power and decreased with the increasing of angular scanning speed.