应变速率控制对金属材料静载拉伸性能的影响

Effects of Strain Rate Control on Static Tensile Properties of Metallic Materials

探讨了不同速率控制模式对金属材料拉伸性能的影响,指出了名义速率与实时反馈速率会存在差异。对于连续屈服材料,引伸计反馈的速率eLe与根据横梁位移速率和试样平行长度估算的应变速率eLc差异不大;对于不连续屈服材料,弹性段反馈的应变速率eLe远低于根据试样平行长度估算的应变速率eLc,出现屈服平台后eLe高于eLc,屈服后均匀变形阶段eLe与eLc基本相等。不同试验速率及控制模式下,应变速率增大,载荷增加率增大,滑移线贯穿整个晶粒的难度增加,从而使测得的Rp0.2和ReL增加,Rm基本上处于稳定状态,试样断口的韧窝尺寸减小,试样的位错密度增加,断后伸长率降低,塑性应变比无明显变化,应变硬化指数降低。

The effects of different rate control modes on the tensile properties of metal materials were discussed. It is pointed out that there are differences between nominal rate and real-time feedback rate. For continuous yielding materials, the rate of extensometer feedback e L e is not significantly different from the strain rate eLc estimated from the beam displacement rate and the parallel length of the sample. For discontinuous yielding materials, the strain rate of elastic section feedback eLe is much lower than the strain rate eLc estimated by the parallel length of the sample, then eLe is higher than eLc after yielding platform, and the two are substantially equal during the uniform deformation phase after yielding. Under the different test rates and control modes, with the increase of strain rate, the load increase rate increases, the difficulty of slip lines extending through the entire grain increases, so that the measured Rp0.2 and ReL increase, Rm is basically in a stable state, the dimple size of the sample fracture decreases, the dislocation density of the sample increases, the elongation after fracture decreases, the plastic strain ratio does not change significantly, and the strain hardening index decreases.