【摘要】 利用凯尔测控EUM-25K20型拉扭疲劳试验机,在110 K下对S30408母材试件、含焊缝试件、无预应变、预应变8%、12%的试件进行了单轴棘轮效应试验研究。实验发现,母材试件与焊材试件的棘轮行为与平均应力、幅值应力及其加载历史密切相关。由于焊缝金属中少量铁素体的软化作用,焊缝试件的初始棘轮应变及小循环应力下的棘轮应变大于母材。但随着塑性变形的增加,焊缝金属中更高含量合金元素存在更为明显的强化作用,使得焊缝试件在较大循环应力下一定循环圈数后的棘轮应变小于母材。无论母材试件还是焊缝试件,棘轮应变随预应变的增加而降低,在较小的循环应力水平下,预应变可以完全抑制棘轮应变的累积。S30408在110 K下为率相关材料,棘轮应变随加载率的升高而降低。更多还原

【Abstract】 Taking advantage of the EUM-25 K20 tension-torsion fatigue testing machine by CARE,the cryogenic uniaxial ratcheting tests were carried out for the S30408 specimens with and without weld,and with 0%,8%,and 12% pre-strains at110 K. It is shown that ratcheting behavior of specimens with and without weld is closely related to mean stress,amplitude stress and loading history. Because of the softening effect of a small amount of ferrite in weld metal,the initial ratcheting strain of weld specimen and ratcheting strain of weld specimen under small cyclic stress is larger than that of base metal. However,with the increase of plastic deformation,the higher content of alloying elements in weld metal has a more obvious strengthening effect,which makes the subsequent ratcheting strain of weld specimens with a certain number of cycles smaller than that of base metal under larger cyclic stress. The ratcheting strain of specimens with and without weld decreases with the increase of the pre-strain at cryogenic temperature. The accumulation of ratcheting strain can be completely restrained by pre-strain at a small cyclic stress level. S30408 is rate-dependent material at 110 K,and ratcheting strain decreases with the increase of loading rate.更多还原