| 摘要: |
| 以AZ31B镁合金板材为研究对象,采用基于断裂力学理论分析电阻点焊接头拉剪力试验后的两种断裂模式,即纽扣断裂和结合面断裂.结果表明,AZ31B镁合金焊点断裂形式受熔核边界的最大拉应力影响,当熔核边界的最大拉应力小于母材抗拉强度时,焊点发生纽扣断裂,反之则发生结合面断裂;同时,AZ31B镁合金的焊点从纽扣断裂过渡到结合面断裂,存在一个临界熔核直径,即当熔核直径小于6.5 mm时,会发生纽扣断裂;大于6.5 mm时容易发生结合面断裂.通过计算AZ31B镁合金焊点的应力强度因子,发现因子数越大,焊点越不容易发生结合面断裂.同时,焊点的承载能力不受断裂形式的影响. |
| 关键词: AZ31B镁合金 电阻点焊 应力强度因子 断裂形式 |
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| 基金项目:国家863高技术研究发展计划资助项目(2008AA04Z136);国家自然科学基金资助项目(50975197);天津市应用基础研究计划面上项目(06YFJMJC03400);广东省教育部产学研结合项目(2007A090302105);天津市应用基础研究计划基金资助项目(09JCZDJC24000);天津高校双五科技计划项目(2009E6-0020) |
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| Analysis on failure modes of AZ31B magnesium alloy joint of resistance spot welding |
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AO Sansan1,2, LUO Zhen1,2, BU Xianzheng1,2, WAND Rui1,2
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1.School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China;2.Tianjin Key Laboratory of Advanced Joining Technology, Tianjin University, Tianjin 300072, China
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| Abstract: |
| The fracture mechanics theory was used to analyze the two fracture modes in shear tension tests for AZ31B magnesium alloy joint of resistance spot welding.The shear tension test results showed that the fracture mode of the AZ31B magnesium was influenced by the maximum tensile stress at the nugget boundary.The button-pullout fracture will happen if the maximum tensile stress at the nugget boundary is lower than the tensile strength of the base metal;otherwise the interfacial fracture happens.And there is a critical nugget diameter when the failure mode is transferred from button-pullout fracture to interfacial fracture.If the nugget diameter is less than 6.5 mm,the button-pullout fracture will occur,and the interfacial fracture will happen if the nugget diameter is larger than 6.5 mm.The calculation on the equivalent stress intensity factor at the spot weld indicates that the interfacial fracture is harder to occur with the stress intensity factor being increased,and the fracture mode has little influence on the load-capacity of the joint. |
| Key words: AZ31B magnesium alloy resistance spot welding stress intensity factor fracture mode |
