停歇对疲劳裂纹扩展超载迟滞效应影响的研究

本文用 16 Mn和 A 537 两种普通低合金钢试件,较系统地研究了停歇对疲劳超载迟滞效应的影响。研究表明,疲劳载荷中的停歇对超载迟滞效应有明显影响,其影响的程度大小与停歇时的载荷 P_H,停歇时间 t_H 等因素密切相关;不但可能使试件的疲劳寿命减少,也可能使试件的疲劳寿命增加。在工程结构疲劳设计、分析及应用超载迟滞效应时应予以注意。

INFLUENCES OF LOAD DWELLS ON CRACK GROWTH RETARDATION OF STEELS

Effects of load dwells on crack growth might be significant in correlating laboratory data from accelerated life tests ro real life fatigue perfomance of engineering structures. In this study, the dwells following an averload effects on fatigue crack retardation behaviors in two structureal steels-ASTM A537 and 16Mn are primarily investigated. Influences of different dwell times (holding times) and dwell loads are examined. It is shown that as the holding time at zero load increased, the number of delay cycles decreased and as dwell load magnitude increased, the number of detay cycles increased in general. It is found that dwelt only affects the rate (da/dN)dmin. at the tnaxium retardation point and no significant changesoccur in delay affected zone size. The mechanisms of these observations are then explained.Effects of load dwells on crack growth might be significant in correlating laboratory data from accelerated life tests ro real life fatigue perfomance of engineering structures. In this study, the dwells following an averload effects on fatigue crack retardation behaviors in two structureal steels-ASTM A537 and 16Mn are primarily investigated. Influences of different dwell times (holding times) and dwell loads are examined. It is shown that as the holding time at zero load increased, the number of delay cycles decreased and as dwell load magnitude increased, the number of detay cycles increased in general. It is found that dwelt only affects the rate (da/dN)dmin. at the tnaxium retardation point and no significant changesoccur in delay affected zone size. The mechanisms of these observations are then explained.