对在三种状态下(退火、20%预变形、形变时效)普碳钢SAE1008进行低周弯曲疲劳的X射线分析。在最大、最小应变下的表面应力降低,拉伸周期卸载后表面残余应力的减小和最初20～30周期内半高宽度的降低表明在应变循环的开始阶段迅速的周期软化。在这个初始阶段以后,发现所有的试样其显微结构与材料的初始状态无关,同样地,疲劳寿命作为应变幅的 X-ray analysis of low-cycle bending fatigue of carbon steel SAE1008 in three states (annealed, 20% pre-deformation, strain-aged) The reduction of the surface stress at maximum and minimum strain, the reduction of residual stress at the surface after the unwinding of the stretching cycle, and the reduction of the FWHM in the first 20 to 30 cycles indicate a rapid period softening at the beginning of the strain cycle. After this initial stage, all samples were found to be microstructural independent of the initial state of the material, and similarly, the fatigue life as the strain amplitude