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研究含长裂纹薄壁结构弹塑性状态下的裂纹扩展规律对于保证机体结构安全具有重要意义.设计了民机用铝合金大宽板裂纹扩展速率测试用试验件和夹具,进行了2024-T3和7075-T6两种铝合金大宽板弹塑性状态下裂纹扩展速率测试.讨论了应力强度因子变程(ΔK)和裂纹中心线处的张开位移变程(Δδ)作为弹塑性状态下裂纹扩展速率表征参量的适用性.研究结果表明:中、高级应力水平作用下,含长裂纹铝合金大宽板裂纹进入快速扩展阶段,裂纹扩展ΔK~da/dN曲线发生明显转折,不能用Paris公式拟合.在裂纹扩展后期,Δδ~da/dN曲线在双对数坐标下呈线性关系,可用Δδ~da/dN关系曲线来表征弹塑性状态下铝合金的裂纹扩展速率.
It is important to study the crack propagation law of long-cracked thin-walled structures in elastic-plastic state to ensure the structural safety of the machine.The test pieces and fixtures for testing the crack growth rate of the wide- 7075-T6 Two kinds of wide-breadth slabs of aluminum alloy were tested under the condition of elastic-plastic crack growth rate.The stress-strain factor variation (ΔK) and the open displacement range (Δδ) at crack centerline were discussed as the crack propagation in the elasto-plastic state The results show that under the action of intermediate and advanced stress levels, the crack of the large-width plate with long-cracked aluminum alloy enters a rapid expansion phase, and the curve of crack propagation ΔK ~ da / dN turns significantly, and can not be calculated by Paris formula In the late stage of crack propagation, the Δδ ~ da / dN curve shows a linear relationship in double logarithmic coordinates, and the Δδ ~ da / dN relationship curve can be used to characterize the crack growth rate of the aluminum alloy in the elasto-plastic state.