平面弯曲载荷作用下试件断面形状对疲劳寿命预测的影响

PEDICTION OVER THE INFLUENCE OF THE SPECIMEN CROSS SECTION’S SHAPE TO THE FATIGUE LIFE UNDER PLANE BENDING

试图用应力—应变幅值关系式预测材料在平面弯曲负载条件下，不同断面形状试件的疲劳寿命。该关系式σ＝１．７３σｂεｐ０．１６为循环轴向拉压碳素结构钢的经验关系式［１］。由于平面弯曲负载下试件断面存在应力梯度，而拉压负载时试件断面无应力梯度变化，两负载下相同试件断面有相同的表面真应力σＲ，用力学方法可以推导平面弯曲负载条件下不同断面形状试件表面真应力σＲ和名义应力σ的关系，并换算出该名义应力同试件表面应变的关系，最后用这一关系预测了不同试件断面形状的疲劳寿命。

It has been tried to predict the fatigue life of the specimen with different cross section acted under plane bending by the stress strain formular.The formular σ=1.73σ b ε p 0.16 represents the law of carbon structure steel under axile push pull stress.Because there is stress gradient under plane bending and there is no stress gradient under push pull stress over the cross section.Given there is the same surface stress for the specimen under two types of loading.the relationship between the nominal stress σ and the surface stress σ R for the specimen with different cross section size acted under plane bending can be deduced by mechanics theory,and the relationship between nominal stress and specimen surface stress.It is reported at the end of this paper that this relationship can be used to predict the fatigue life of the specimen with different cross section.