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In recent years, new materials such as titanium, nickel alloys, and high-strength steels have been widely used in medical, nuclear, and other industries. Since the manufacturing of different components from these materials has always been associated with the machining process, the use of hard machining in their production is unavoidable. The short life of the cutting tool, the poor quality of the machined surfaces, and the long machining time are some of the challenging issues involved in the traditional machining of these materials. Therefore, researchers have investigated new machining techniques to increase the efficiency and quality of produced parts. Thermal-assisted machining, especially laser-assisted machining is one of the promising methods of machining difficult-to-machine materials. However, this process faces some challenges in terms of the achievable surface integrity of the machined surfaces. This research studies the effect of cutting and thermal parameters on the surface roughness in the laser-assisted turning (LAT) process of AISI 4340 hard steel with a hardness of 560 HV. The results illustrated that by selecting a proper combination of process parameters, the damage caused by the heat penetration into the workpiece can be minimized and the advantages of LAT can be benefited from.

The use of laser-assisted turning (LAT) can improve different aspects of the machinability of high hardness/strength materials. The heat applied in this process reduces the strength of the material and upon a proper selection of laser heat source and machining process parameters, a significant improvement in the machining process can be achieved. This research studies the effect of machining and laser heat source parameters on the surface integrity of the LAT process of AISI 4340 hardened steel with a hardness of 560 HV using Response Surface Methodology (RSM). The effect of machining process parameters (feed rate, depth of cut and cutting speed) and laser power on the surface integrity characteristics of the machined surfaces (white layer thickness, microhardness, surface roughness, and surface chemical composition) are investigated. A detailed finite element simulation of the process has been performed to better understand the physics of the process and to interpret the experimental results. Laser power and feed rate are shown to be the most significant parameters affecting the surface integrity of the machined surfaces. It has been shown that a proper selection of machining and laser heat source parameters makes it possible to minimize the adverse effect of laser heating in the LAT process. This can pave the way for the widespread application of the LAT process by eliminating one of the most important obstacles of this process by controlling the laser heat diffusion into the workpiece.

The aim of the present paper is to fabricate metallic bipolar plates (BPPs) with active area of 100 cm 2 modeled on an industrial gas flow field scheme. In order to produce these plates, a stamping process has been employed to reduce cost and increase production speed. 316L stainless steel sheets with the thickness of 0.1 mm have been used. The effect of forming forces on channel filling depth, channel width, rib width, the uniformity in the depth of formed channels and the thickness distribution of channels have also been studied. The stress and strain distributions of formed bipolar plate are investigated using finite element simulation. The results reveal that the stamping process does have the ability to produce a perfect bipolar plate by one-step forming die for desired dimensions. Moreover, increasing the stamping force to an optimum level has insignificant effect on the depth of the channels. However, stamping force increment results in an increase in width of the channels and ribs.

This study investigates the laser-assisted turning (LAT) of AISI 4340 hardened steel (∼52 HRC). Despite the various advantages of this process for machining hard materials, the issues related to the machined surface integrity remain the most important challenge. The laser heating used in this process substantially affects the surface integrity characteristics of the workpiece and its mechanical properties. Therefore, it is important to understand, predict, and optimize the workpiece's heat effects at various regions. Due to the complexity of the process, experimental investigations alone cannot reveal thorough information of various phenomena involved. Therefore, a reliable finite element model has been developed to predict the effect of various process input parameters on the metallurgical changes of the machined workpieces. Since general-purpose finite element codes cannot predict the phenomena of interest, three user-defined subroutines have been developed to capture surface integrity parameters such as heat-affected zone, hardness variations of the machined surface, and white layer formation. The developed FE model consists of three parts: mechanical model, thermal model, and coupled thermo-mechanical model. The results of the FE models are verified with experimental data, and a good agreement has been observed. The effect of various process parameters on the surface integrity characteristics of the workpiece has been studied in detail. It has been observed that the laser scanning speed, laser power, and undeformed chip thickness have the most significant influence on the metallurgical effects on the workpiece, respectively.

Bipolar plates are some of the most important parts of a fuel cell that constitute a high percentage of weight and cost in a fuel cells collection. Furthermore, metals due to lesser weight and cost are suitable replacements for thick graphite plates which need high cost of machining. In recent years, among of sheet forming productions the applications of stamping process have become increased due to reduction of cost and increase production speed. The present study investigates the manufacturing process of metallic bipolar plates made of SS316L with a thickness of 0.1 mm using stamping process. In this respect, the effect of lubricant on improvement of fabricated plates has been examined. Also, two cases of forming process with and without lubricant on depth of filling flow channels, thickness distribution, thickness reduction and uniformity of channels have been evaluated. The results obtained from the experiments showed that effect of lubricant is so important. Moreover, by using of lubricant the thickness reduction, uniformity of channels, depth of filling flow channels and thickness distribution could be improved.

Bipolar plates are considered one of the most important parts of fuel cells, made of different materials. Graphite bipolar cells are generally expensive, hence high machining cost. Metals are known to be suitable replacements due to their lower weight and cost. Bipolar plates can be designed and produced using either a concave or convex pattern. This study made an effort to fabricate metallic bipolar plates through two-die rubber pad forming method with both convex and concave patterns. Stainless steel sheets of 316 with the thickness of 0.1 mm were used for the fabrication. Polyurethane with the hardness of shore A 85 and the thickness of 25 mm was selected. The effect of forming forces on micro-channel filling depth, thickness distribution of channels in each of the patterns, and their appropriate states (maximum filling depth and minimum thickness reduction) were also studied. The results indicated that in similar geometry and process, the convex die would create a deeper channel compared with the concave one. Increases in forming forces would cause the filling depth of micro-channels to rise, but the thickness of critical regions to decrease due to an increase in the aspect ratio (the ratio of channel depth to channel width). Finally, the best possible version of bipolar plates in both convex and concave models was formed.