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本文把常温时低周疲劳中塑性应变范围Δε_p与疲劳寿命N_f间的Coffin-Manson公式Δε_p=αN_f~β推广到含有蠕变应变范围Δε_c的非弹性应变范围Δε_(pc)(Δε_(pc)=Δε_p+Δε_c)与和时间因素有关的蠕变疲劳寿命之间的关系式Δε_p=α(t)N_β~(f(t))。式中:α(t)=mt~n,β(t)=ht~k,其中m、n、h、k为常数,并通过一种铁基合金在轴向拉压对称、拉峰值保时控制应变条件下的疲劳试验拟合出这些常数。把其它人对其余几种材料的试验结果按同样方法处理后,发现都符合上面的关系式,且n=2k。对实验结果的分析得出,保时影响疲劳寿命的原因是增加了蠕变应变。借助显微组织的观察初步认为,上述关系式中的α(t)、β(t)和Δε_c都是与晶界显微空穴的生成和发展有关的物理量,这种沿晶空穴的生成和发展提供了蠕变应变并影响着疲劳寿命和断口形貌。实验还表明,进入稳定循环后对应着稳定的胞状组织的形成。
In this paper, the Coffin-Manson formula Δε_p = αN_f ~ β between the plastic strain range Δε_p and the fatigue life N_f is extended to the inelastic strain range Δε pc (pcε) with creep strain range Δε_c Δε_p + Δε_c) and the creep fatigue life related to the time factor Δε_p = α (t) N_β ~ (f (t)). Wherein, α (t) = mt ~ n, β (t) = ht ~ k, where m, n, h and k are constants and are symmetrical in the axial direction through an iron- Fatigue tests under controlled strain conditions fit these constants. When other people test the results of the remaining materials in the same way, they all found the above relation and n = 2k. The analysis of the experimental results show that the reason that the fatigue life is affected by the timing is that the creep strain is increased. With the help of the observation of the microstructure, it is preliminarily believed that α (t), β (t), and Δε_c in the above relation are both physical quantities related to the formation and development of the microcracks in the grain boundary. And development provide creep strain and affect fatigue life and fracture morphology. Experiments also show that stable cell cycle progression corresponds to stable cellular formation.