采用有限元方法对奥氏体钢四点弯曲疲劳试验的加载过程进行了数值模拟,分析了疲劳试样的应力分布与疲劳寿命,确定了受力分布相对均匀的试样的合理尺寸范围,并对一种Cr-Mn奥氏体钢进行了四点弯曲疲劳试验研究,对比分析了有限元模拟与试验结果间的差别与原因.结果表明,试样尺寸不同,两加载辊之间的应力分布规律不同;当t/h(材料厚度/加载辊距)>1.4时,最大应力出现在靠近加载辊的内侧,距加载辊0.4~0.5 mm;当t/h=1.2~1.4时,两加载辊之间的应力分布比较均匀,最大模拟应力与加载应力(理论值)的误差小于5%;当t/h<1.2时,最大应力出现在两加载辊中间,其中t/h=0.7~0.8时,模拟值最大应力与加载应力比较接近,但应力分布均匀性较低;采用t/h≈1.3的试样进行疲劳试验研究,试验后的疲劳裂纹均产生在两加载辊中间,在加载辊外侧未发现疲劳裂纹,这与模拟结果相一致;模拟疲劳极限为498 MPa,循环4.0×106周次,试验测定疲劳极限为505 MPa,循环3.6×106周次,模拟值略小于试验值,可见有限元方法可以较准确地预测材料的疲劳寿命.
Using finite element method(FEM),the loading process of four-point bending fatigue test of austenite steel was simulated,the stress distribution and fatigue life of the specimens were analyzed,and the reasonable size range of the samples with uniform stress distribution was determined. Four-point bending fatigue test of a Cr-Mn austenitic steel was carried out,and the differences between the finite element simulation and the experimental results were compared and analyzed. The stress distributions between the two loading rollers are different with different sample sizes. The maxi-mum stress appears near the inner side of the loading rollers(0.4-0.5 mm from it)with t/h>1.4;With t/h=1.2-1.4,the stress distribution between the two loading rollers is uniform,and the error between the maximum simulated stress and the load stress(theoretical value)is within 5%;with t/h<1.2,the maximum stress occurs in the middle of two loading rollers,and it is close to the load stress as t/h=0.7-0.8. The fatigue cracks occur in the middle of the two roller after fa-tigue tests and no fatigue crack appears at the outside of loading rollers,which is consistent with the simulation results. The simulated fatigue limit is 498 MPa with about 4.0×106 cycles,and the fatigue test limit is 505 MPa with about 3.6×106 cycles. The calculated value is slightly less than the experimental value which shows that the fatigue life can be predicted using the finite element method.