Experimental analysis of formability of stainless steel ۳۱۶L metallic bipolar plates

سال انتشار: 1401
نوع سند: مقاله کنفرانسی
زبان: انگلیسی
مشاهده: 144

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شناسه ملی سند علمی:

PEEL11_028

تاریخ نمایه سازی: 18 تیر 1401

چکیده مقاله:

In this study, stamping and hydroforming process was used to form a ۰.۱ mm-thick SS۳۱۶L sheet to produce bipolar plates. The ABAQUS software was used to simulate the processes. A ۶۰-ton hydraulic press was used in the stamping process and ۱۴۰۰ bar hydrostatic pressure unit was used in the hydroforming process. According to the results, a good agreement was observed between the experimental and simulation results. Simulation result of the stamping process showed that sheet metal would achieve the critical thickness at the corners before complete filling of the die in the stamping process and the maximum forming height was about ۰.۶ mm. Hydroforming process could not form the final height of micro-channel because the thickness of sheet at the die corner achieved the critical values. In addition complete filling of the die by hydroforming process was less than stamping process at the same channel height and also needs high pressure.Fuel cells are considered to be a promising energy conversion technology of the future mainly due to their high efficiency, low noise and minimal emissions particularly for transportation and portable applications. Among the various components of the fuel cell, the bipolar plates constitutes about ۶۰–۸۰% of the stack weight [۱]. Nowadays, there are mainly three kinds of materials to make a bipolar plate: graphite, polymer-carbon composite and metal material. Graphite and polymer-carbon composite bipolar plates are selected as the basic material in the traditional fuel cell research due to its good conductivity, small contact resistance and good corrosion resistance. However, the difficulties in manufacturing the graphite bipolar plate and composite bipolar plate lead to high cost. As a result, many researchers have turned their attention to metal materials with better formability [۲]. Metal forming processes, such as stamping and hydroforming are well-known for their high productivity rates [۱]. In this study, forming a metallic bipolar plates with stamping and hydroforming processes are investigated by using finite element simulation and experiments.The ABAQUS software was used to simulate the process. Punch and die in the stamping process and die in hydroforming process were rigidly modeled. Since the length of the channels of flow field are significantly larger than the dimensions of cross section of channel, the process was assumed as plane strain and ۲D simulation of cross section of the channel was done. The plasticity behavior of the stainless steel ۳۱۶L sheet was identified using uniaxial tensile tests. The swift law was adopted to obtain a reliable stress-strain relationship. In the stamping process, to apply force on the sheet metal, the displacement boundary condition was applied to the punch while the die was fixed in all directions. In the hydroforming process, die fixed in all direction and uniform pressure was applied on one side of blank sheet. Surface-to-surface contact conditions between the punch and the sheet, and between the die and the sheet in the stamping procees were defined with a friction coefficient of ۰.۲. The same contact condition was defined between the die and the sheet in the hydroforming process.In this study, stamping and hydroforming process was used to form a ۰.۱ mm-thick SS۳۱۶L sheet to produce bipolar plates. The stamping die consisted of the punch and the matrix on which metallic bipolar micro-channels were machined. Rib and channel widths of Micro-channels were ۱.۱ and ۰.۵ mm, respectively. The corner radius of die and punch in stamping and the corner radius of die in hydroforming process were equal to ۰.۲ mm and the draft angles were equal to ۱۰°. A ۶۰-ton hydraulic press was used in The height of channels and thickness distribution curves obtained from experimental tests and numericalinvestigations were evaluated to validate the simulation results. According to the results, a goodagreement was observed between the experimental and simulation results. According to simulation results(Fig. ۲) die and punch radius areas in the stamping process and die radius area in the hydroformingprocess are the critical areas limiting the maximum forming height of micro-channels. Concerning thelimit strain, the critical thickness limiting the maximum forming height of micro-channels is ۰.۰۵۸ mm.Simulation result of the stamping process showed that sheet metal would achieve the critical thickness atthe corners before complete filling of the die in the stamping process and the maximum forming heightwas about ۰.۶ mm. the experimental results (Fig. ۲) verified simulation results and the bipolar platesformed with stamping process included micro-channel with maximum height of ۰.۶ mm. Hydroformingprocess could not form the final height of micro-channel because the thickness of sheet at the die cornerachieved the critical values. In addition complete filling of the die by hydroforming process was less thanstamping process at the same channel height and also needs high pressure.Fig. ۲. Simulation result, (a) hydroforming, (b) stamping Fig. ۳. Experimental result, (a) hydroforming, (b) stampingStamping and hydroforming process investigated to form a bipolar plate with ۰.۱ mm SS۳۱۶L sheet metaland concluded that complete forming the proposed geometry of bipolar was impossible and needs othermethods such as two stage forming methods

نویسندگان

Mohammad Momenifar

Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran