【摘要】 按照较严格的弹塑性断裂力学分析得出的在应变疲劳条件下的裂纹扩展理论,本文从实验上证明了采用形变功密度(?)σdε代替塑性应变范围△εp作为在宽阔的低周疲劳寿命范围(10~1—10~5周)内描述应变疲劳损伤参数的合理性。同时,还对线弹性断裂力学和传统的低周疲劳Manson-Coffin关系的局限性进行了讨论。更多还原

【Abstract】 Correct prediction of fatigue life and the evaluation of materials should consider the whole process including crack formation and propagation. Recently, the traditional analysis approach of LCF is based on Mansom-Coffin relation determined from LCF date of smooth specimen and does not consider the whole process involving crack propagation. In many cases, however, engineering structures often differ from ideal smooth specimen. Owing to the metallurgical defects and damages done in fabrication, the stage of crack formation almost does not exist, and at the begining of LCF the crack is in the stage of crack propagation. So the actual life should be lower than the estimated one.LEFM can be used to analyse fatigue crack propagation life of aeroplane components only in the late stage where the crack has become relative long. This stage occupies only a minor fraction of the whole life, while the majority of the life is spent during micro- or small crack propagation stage. With regard to the analysis of small crack growth within the cyclic plastic strain region LEFM can not be used and an EPFM analysis must be developed.In according to a theory of crack grouth under strain fatigue condition based on a relativily strict analysis of EPFM, the present paper has proved experimentally thatit is reasonable to use the deformation work density (?) σdε in stead of the plasticstrain range △εp as a parameter to describe strain fatigue damage for a wide range of LCF life (101-105 cycles).更多还原