对不同厚度2A12-T4铝合金单边缺口试样进行了疲劳裂纹扩展试验,观察了裂纹稳定扩展前沿形貌并用椭圆方程进行了拟合,得到了椭圆方程拟合参数；建立了裂纹前沿相对隧道深度与试样厚度之间的数学表达式,并对裂纹扩展前沿形貌转变的临界厚度进行了预测,最后进行了试验验证.结果表明：随着试样厚度的增加,试样表层与中心层裂纹长度的差值逐渐变小,疲劳裂纹稳定扩展前沿形貌由“隧道”形状逐渐变成与表面垂直的直线形；裂纹前沿相对隧道深度随试样厚度的增加而减小,并在厚度为31．5 mm时趋向0,试验结果证明了预测结果的准确性.
The fatigue crack growth tests were carried out on the single-edge notched specimens of 2A12-T4 aluminum alloy with different thicknesses.The crack front morphology during stable crack growth was observed and fitted by the elliptic equation,and the fitting parameters of elliptic equation were obtained.The mathematical expression between the relative tunnel depth of crack front and the specimen thickness was established.The critical thickness of the crack front morphology transition during growth was predicted and verified by experiments.The results show that with the increase of the specimen thickness,the difference of crack length between the surface layer and the inner layer gradually decreased.The fatigue crack front morphology during stable crack growth changed gradually from"tunnel"shape to a straight line perpendicular to the surface.The relative tunnel depth of crack front decreased with the increase of the specimen thickness,and tended to 0 with the thickness of 3 1 .5 mm. The test results verified the accuracy of the predicted results.
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