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为在飞机结构设计阶段进行钛合金焊接件的疲劳强度评估,采用军机DFR方法进行了TC4-DT钛合金电子束横焊缝试件的疲劳分析,并对其进行了试验验证。首先,进行了TC4-DT钛合金电子束横焊缝试件的DFR基准值测试,得到DFR基准值为470MPa;其次,为了验证军机DFR方法分析结果的可靠性,进行了TC4-DT钛合金电子束横焊缝试件在随机谱下的成组疲劳试验,采用断口判读技术确定裂纹萌生寿命,得到了随机谱下的试验中值寿命;最后,利用测得的DFR基准值,采用军机DFR方法评估得到随机谱下成组试验的试验件中值寿命以及对应试验中值寿命的应力水平。对比分析结果表明:分析寿命比试验寿命低10%,分析的应力水平比试验应力水平低3%。此结果表明军机DFR方法略偏保守,与DFR方法计算结果偏保守的特征一致,也验证了军机DFR方法在TC4-DT钛合金电子束焊接件上应用的可行性。
In order to evaluate the fatigue strength of titanium alloy welded parts during the aircraft structure design stage, the fatigue analysis of TC4-DT titanium alloy transverse cross-welded specimens by DFR method was conducted and verified by experiments. First of all, the DFR reference value of TC4-DT titanium alloy cross-beam weld was tested, and the DFR reference value was 470MPa. Second, in order to verify the reliability of the military DFR method analysis results, TC4-DT titanium alloy electronic In the group fatigue test of beam cross-weld specimens, the crack initiation life was determined by fracture interpretation technique, and the median lifetime of the test was obtained under random spectrum. Finally, the DFR method was used The median lifetime and the stress level corresponding to the median lifetime of the test were obtained from randomized spectra. The results of comparative analysis show that the analysis life is 10% lower than the test life and the analyzed stress level is 3% lower than the test stress level. The results show that the DFR method of military aircraft is a little conservative, which is consistent with the conservative characteristic of the DFR method. It also verifies the feasibility of DFR method applied to TC4-DT titanium alloy electron beam welded parts.