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利用热/力模拟试验机,对Cr15Mn9Cu2Ni1N不锈钢进行了950℃~1200℃高温范围内的拉伸试验;采用有限元方法对试样的均匀变形过程进行了分析。高温拉伸过程中,试样在达到最大应力后并不立即颈缩,而是还要经历一段宏观均匀变形后才颈缩。分析结果表明:最大应力之后,试样端部区域等效应力降低,横截面积收缩量减小,而中心区域横截面积收缩量增大,形成了潜在颈缩区;在应变速率敏感性的作用下,潜在颈缩区的变形抗力随应变速率的增大而增加,使变形不能在该区域集中,而转向其它位置,保持了试样的宏观均匀变形,且颈缩未在最大应力后立即发生;在高温拉伸条件下,材料应变速率敏感性的增大是颈缩延迟发生的主要原因,随着变形温度升高,应变速率敏感性增大,也使得试样颈缩前的均匀变形量增大。
The tensile test of Cr15Mn9Cu2Ni1N stainless steel was carried out in the high temperature range of 950 ℃ ~ 1200 ℃ by using the heat / force simulation testing machine. The uniform deformation process of the sample was analyzed by finite element method. During the high-temperature stretching process, the sample does not neck immediately after it reaches the maximum stress, but undergoes a macro-uniform deformation before it is necked. The results show that after the maximum stress, the equivalent stress decreases, the cross-sectional area shrinks and the shrinkage of the cross-sectional area increases, forming a potential necking region. In the strain rate-sensitive , The deformation resistance of potential necking region increases with the increase of strain rate so that deformation can not be concentrated in this area and turns to other positions to maintain the macroscopic uniform deformation of the specimen and the necking does not occur immediately after the maximum stress Occurs; under high temperature tensile conditions, the increase of material strain rate sensitivity is the main reason for the occurrence of necking delay. As the deformation temperature increases, the strain rate sensitivity increases, which also makes the sample uniform deformation before neck shrinkage Increase in volume.