针对飞机关键薄壁件焊接过程中产生的"簸箕"变形问题, 采用有限元结合实验验证的方法进行了焊接变形及焊后热处理校形的研究. 通过实验获得了材料的基础物性及高温蠕变行为, 验证了焊接及焊后热处理有限元模型. 利用可靠的热处理有限元模型进行了热处理工艺优化. 结果表明, 筋条焊后开槽导致沿筋条方向的应力释放及筋条-长衍焊点是导致"簸箕"变形的主要原因; 升高温度,增加载荷及延长保温时间能够改善热处理校形的效果, 并据此制定了面向工程应用的TA15钛合金薄壁构件的热处理工艺图.
Weld deformation of the thin-wall weldment used in fighter aircraft not only hinders its subsequent procedure of fabrication and assembling, but also reduces its fatigue strength. As a result, weld deformation shortens its service life essentially. Dustpan deformation is always produced in the thin-wall weldment after multiple-pass weld. In this work, combining with the experiment, the finite element method was adopted to analysis the deformation of the thin-wall weldment by multiple-pass weld and its shape correction by post weld heat treatment. For obtaining the fundamental properties such as thermal parameters and mechanical parameters of TA15 titanium alloy, a series of experiments were conducted at room temperature and high temperatures. Additionally, creep behaviors of TA15 titanium alloy were studied at the temperatures of 500, 550, 600, 650, 700 and 750 ℃, and the parameters of creep constitutive equations of the alloy were obtained with considering the analysis of post weld heat treatment. A thermal coupled temperature-displacement analysis for welding and post weld heat treatment was performed on a three dimensional shell model of protective grille. Experiments of multiple-pass weld and post weld heat treatment were used to testify the reliability of the finite element model of welding and post weld heat treatment. With using the reliable finite element model, the parameters of heat treatment were studied. The study indicates that, the fabrication on the crossing of structure section and fillet after fillet-wallboard weld leads the compression deformation release along the fillet, after that, the shrinkage distortion produced during spot welding of fillet-structural section mainly contributes the large dustpan deformation of the thin-wall weldment; increasing temperatures, enlarging loads and prolonging the hold time can improve the shape correction of the thin-wall weldment during post weld heat treatment, hence the guide maps of the post weld heat treatment for shape correction of the thin-wall weldment under 700 and 750 ℃ are worked out.
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