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7075铝合金自冲铆成形过程裂纹仿真分析

Simulation analysis of crack formation in the self-piercing riveting process of 7075 aluminum alloy

  • 摘要: 为了研究高强度铝合金在自冲铆接工艺中裂纹的形成与扩展,基于7075铝合金材料力学性能试验结果,拟合了Johnson-Cook本构模型和断裂准则,建立了自冲铆接工艺成形仿真模型,分析高强度铝合金自冲铆接头成形过程裂纹的形成与扩展,并进行了自冲铆接工艺试验验证.研究发现,裂纹源产生于机械内锁区和下板底部,并且下板材料是裂纹产生的主要区域,大部分裂纹沿接头径向扩展,随着铆接进行,接头底部开始出现少量沿周向扩展的裂纹.对比仿真与试验过程的载荷-行程曲线以及接头机械内锁结构几何特征尺寸,最终成形力和机械内锁结构尺寸的误差均在16%以内,验证了所建立的自冲铆接成形仿真模型的可靠性,为后续进行自冲铆接工艺质量调控提供了理论基础.

     

    Abstract: To investigate the formation and propagation of cracks in the self-piercing riveting (SPR) process of high-strength aluminum alloy, the Johnson-Cook constitutive model and fracture criterion were calibrated based on mechanical property test results of 7075 aluminum alloy. A simulation model for the SPR forming process was established to analyze crack initiation and growth during the formation of high-strength aluminum alloy SPR joints. Experimental validation of the self-piercing riveting process was also conducted. The study revealed that crack initiation primarily occurs in the mechanical interlock zone and the bottom of the lower sheet, with the lower sheet material being the main region for crack formation. Most cracks propagate radially along the joint, while a small number of circumferentially extending cracks begin to appear at the bottom of the joint as the riveting process progresses. By comparing the load-travel curves from both simulation and experimental processes, as well as the geometric characteristics of the mechanical interlock structure, the errors in the final forming force and the dimensions of the mechanical interlock structure were found to be within 16%. This validates the reliability of the established SPR forming simulation model and provides a theoretical foundation for subsequent quality control in the self-piercing riveting process.

     

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