民用飞机延性金属结构局部高应力静强度研究

Study on local high stress strength of ductile metal structures for civil aircraft

针对民用飞机大量使用的延性材料2024-T42和7050-T6的标准试样和开孔试样在拉伸载荷下的失效模式及失效载荷进行了试验研究,基于材料应力应变曲线建立了有限元模型并对其结果进行验证,提出了开孔金属结构局部高应力下的静强度判别准则。试验结果表明:孔折减系数起决定性影响的是材料的屈服应力与极限应力之间的差值,差值越大,孔折减系数越小;在此基础上研究孔边单元的网格质量(粗网格和细网格)及孔边埋头窝对有限元分析结果的影响,分析结果表明:孔边的网格质量(粗网格和细网格)和埋头窝对孔折减系数影响较小,所建立的延性金属结构局部高应力静强度判别准则合理且具有工程价值,对于2024-T42和7050-T6两种延性材料利用该局部高应力静强度判别准则进行计算的保守裕度分别为0.1和0.04。

An experimental study of fail model and failure load was carried out on open-hole samples and standard samples under tension load for ductile material 2024-T42 and 7050-T6,which are widely used in civil aircraft.A finite-element modeling with material stress-strain curve was established and its results were verified,and the static strength criterion for the open-hole under local high stress was proposed.The experimental results show that the decisive factor affecting the pore reduction coefficient is the difference between the yield stress and ultimate stress of the material.The larger the difference is,the smaller the pore reduction coefficient is.On this basis,the influence of the mesh quality(coarse mesh and fine mesh)and countersunk hole on the strength results were studied.The analysis results show that the mesh quality of the hole edge(coarse mesh and fine mesh)and the countersunk have a small impact on the hole reduction coefficient.The established static strength criterion based on tests for the ductile aluminum alloys is reasonable and useful in the engineering application.The safety margins calculated using the local high stress static strength criterion for 2024-T42 and 7050-T6 ductile materials are 0.1 and 0.04,respectively.