7050-T7451铝合金板材疲劳性能的厚度效应

目的 研究不同厚度的7050-T7451铝合金板材疲劳性能表现出的厚度效应。方法 试验件从3种厚度规格(75、150、203mm)板材的不同厚度位置取样,采用成组试验法进行3级应力–疲劳试验。分析试验数据,发现并总结材料疲劳性能随板材厚度及取样厚度位置变化的演化规律。结果 所有厚度规格板材的表面层材料的疲劳性能均为最优,且不同厚度规格板材表面层材料的疲劳性能差异较小。当板材的厚度较薄(75 mm)时,随着取样厚度位置变化,材料的疲劳性能差异较小;当板材的厚度较厚(150、203 mm)时,从表面层到中心层的材料疲劳性能呈非线性变化趋势,先变弱、后增强,疲劳寿命105循环对应的最大应力降低幅度最大为21%左右。随着板材厚度的增加,疲劳性能最差的厚度层材料,疲劳寿命105循环对应的最大应力降低了20%左右。结论 随着板材的厚度增加,7050-T7451铝合金板材疲劳性能的厚度效应变得越来越强,即疲劳性能在厚度方向的不均匀性越来越明显。工程师应在工程设计中考虑7050-T7451铝合金疲劳性能厚度效应对结构疲劳强度的影响。

Thickness Effect on Fatigue Property of 7050-T7451 Aluminum Alloy Plate

The work aims to study the thickness effect on fatigue property of 7050-T7451 aluminum alloy plates with different thickness. The samples were taken from different locations along the thickness direction of three plates with different thickness (75 mm, 150 mm, and 203 mm). The grouping tests were performed for the three levels of stress-fatigue tests. By analyzing the fatigue test data, the variation law of fatigue property along the plate thickness and sampling thickness location was discovered and summarized. Among the three plates with different thickness, the fatigue strength of the surface layer was the best and varied slightly. For the plate with thickness of 75 mm, the fatigue property changed a little with the varying sampling thickness location. For the plates with thickness of 150 mm and 203 mm, the fatigue property showed nonlinear variation tendency from surface to the center and decreased firstly, and then increased and the maximum stress reduction corresponding to fatigue life of 105 cycleswas about 21%. As the plate became thicker, the maximum stress (fatigue life was 105 cycles) of the surface layer with the worst fatigue decreased by about 20%. As the plate thickness increased, the fatigue property of 7050-T7451 aluminum alloy plate shows much more significant thickness effect, that is to say, the inhomogeneity of fatigue property along the thickness direction becomes more and more obvious. The engineers should consider the impact of thickness effect of 7050-T7451 aluminum alloy plate on the fatigue strength of structure in the design process.