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本文对表面疲劳裂纹形状的试验数据作了一个统计分析,这些数据是在重复轴向拉伸和非平面弯曲之下,进行恒幅疲劳裂纹扩展试验所得到的。已利用现在的数据检验了以前所提出的穿透裂纹经验表达式的应用范围,若用现在分析中所确定的参数,证明这些表达式仍然适用。兹提出一个更简单的表达式,它具有充分的适用性并比以前提出的表达式具有更好的估算值。 符号名称 A:R_b的函数,A=C_1+C_2R_b B:R_b的函数,B=C_3+C_4R_b 式中的C_1、C_2、C_3和C_4是常数。 a:表面裂纹长度之半。 a_0:一个切口或一个集合疲劳裂纹表面长度之半的初始值。 b:裂纹深度。 b_0:一个表面切口或一个集合疲劳裂纹深度的初始值。 e、f和g:由裂纹形状的初始条件所确定的常数。 n:常数 t:板厚 R_b:弯曲应力组合参数,R_b=Δσ_b/(Δσ_m+Δσ_b) Δσ_m:轴向应力范围(双幅) Δσ_b:弯曲应力范围(双幅)
In this paper, a statistical analysis of the experimental data of the surface fatigue crack shape is made. These data are obtained under the constant amplitude fatigue crack growth test under repeated axial and non-planar bending. The current data have been used to test the application of the previously proposed empirical formula for crack penetration, which is validated by the parameters determined in the present analysis. A simpler expression is proposed that is sufficiently applicable and has better estimates than the expressions previously proposed. Symbol name A: R_b function, A = C_1 + C_2R_b B: R_b function, B = C_3 + C_4R_b Where C_1, C_2, C_3 and C_4 are constants. a: half the length of the surface crack. a_0: initial value of half of the length of a notch or a set of fatigue crack surfaces. b: crack depth. b_0: The initial value of the depth of a surface cut or a set of fatigue cracks. e, f and g: constants determined by the initial conditions of the crack shape. n: constant t: plate thickness R_b: bending stress combination parameter, R_b = ?? b / (?? a + ?? b) ??? m: axial stress range (double width) ?? b: bending stress range