Byun Jong Bok, Razali Mohd Kaswandee, Lee Chang Ju, Seo Il Dong, Chung Wan Jin, Joun Man Soo
Engineering Research Institute, School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju 52828, Korea.
Graduate School of Mechanical and Aerospace Engineering, Gyeongsang National University, Jinju 52828, Korea.
Materials (Basel). 2020 Nov 23;13(22):5300. doi: 10.3390/ma13225300.
SUS304 stainless steel is characterized by combined tensile and compression testing, with an emphasis on flow stress at higher strain and temperature. The plastic deformation behavior of SUS304 from room temperature to 400 °C is examined and a general approach is used to express flow stress as a closed-form function of strain, strain rate, and temperature; this is optimal when the strain is high, especially during automatic multi-stage cold forging. The fitted flow stress is subjected to elastothermoviscoplastic finite element analysis (FEA) of an automatic multi-stage cold forging process for an SUS304 ball-stud. The importance of the thermal effect during cold forging, in terms of high material strength and good strain-hardening, is revealed by comparing the forming load, die wear and die stress predictions of non-isothermal and isothermal FEAs. The experiments have shown that the predictions of isothermal FEA are not feasible because of the high predicted effective stress on the weakest part of the die.
SUS304不锈钢的特点是进行拉伸和压缩联合测试，重点关注较高应变和温度下的流动应力。研究了SUS304在室温至400°C范围内的塑性变形行为，并采用一种通用方法将流动应力表示为应变、应变速率和温度的封闭形式函数；当应变较高时，尤其是在自动多阶段冷锻过程中，这种方法是最优的。将拟合得到的流动应力应用于SUS304球形螺柱自动多阶段冷锻过程的弹热粘塑性有限元分析（FEA）。通过比较非等温有限元分析和等温有限元分析的成形载荷、模具磨损和模具应力预测结果，揭示了冷锻过程中热效应在高材料强度和良好应变硬化方面的重要性。实验表明，由于预测的模具最薄弱部位的有效应力较高，等温有限元分析的预测结果不可行。
