对Willenborg以及Maarse迟滞模型的改进及其在Ti-6Al-4V合金中的应用

 疲劳裂纹扩展中超载迟滞效应的计算精度与迟滞模型本身所选用的塑性区公式密切相关,为此,本文提出了塑性区修正公式,用它来代替Willenborg模型和Maarse模型中的原塑性区公式。并将原Maarse模型中按△K_(eff)处理得出的材料常数C~*和n~*,改用恒幅下的材料常数C和n来计算。通过对Ti-6Al-4V钛板超载迟滞效应的计算,表明经本文改进后的模型,不仅比原模型的计算精度有了显著的提高,而且使用更为简便。

MODIFICATION OF THE WILLENBORG AND MAARSE MODELS AND APPLICATION TO THE LIFE PREDICTION FOR Ti-6Al-4V ALLOY

The prediction accuracy of the overload retardation effect on fatigue crack growth （FCG） is closely related to the formula for tie plastic zone adopted by each retardation model. Hence, in order to express more rationally the behavior of fatigue crack growth process and the continuity of the stress state transformation （from plane strain to plane stress mode）, the coefficient α in the formula for the plastic zone used in the Willenborg and Maarse models can be expressed as the following:a=6/1+2S whereS is the fraction of the stress part in a fracture surface. Meanwhile, it was found that the material constants C* and n* in the formula of the Maarse model can be substituted by C and n obtained from the constant amplitude loading tests.From the above mentioned modification of the Willenborg and Maarse models, it is recognized that the modified models can be applied more successfully and conveniently to the life prediction for Ti- 6A1-4V alloy under a single tensile or a series of single tensile overloads. The results calculated with the modified models were found to be fairly consistent with the experimental data.