等离子无模成形叶轮的应力场分析与校核

Plasma deposition dieless manufacturing of turbine parts: thermal stress control and process optimization

等离子熔积无模成形是急速加热快速凝固的短流程制造技术,如何避免制件的热裂纹是该技术的关键,而热裂纹的产生取决于成形过程温度场与应力场的分布特征。用有限元法对预热和水冷两种温控方案进行了模拟仿真,对比分析可知,较预热成形,水冷成形零件表面质量良好、热裂倾向低。随后依水冷条件按跳跃路径计算了叶轮成形过程的热应力场。结果表明,该方案所得零件的温度场较均匀,热应力和热裂倾向显著降低,工艺合理,有利提高成形性。

Plasma deposition dieless manufacturing(PDM) is a rapid heating and solidification process,in which how to avoid cracks and distortions is a key problem.Therefore,a full understanding on the evolution of temperature field variables is essential to achieve a steady state and robust PDM process.To explore the thermal behaviors of this process,the preheated and water-cooled programs for the fabrication of superalloy turbine parts have been designed respectively.Their temperature fields are then evaluated numerically by finite element method.Analysis results show that the water-cooled scheme exhibits lower hot crackability and better formability,which coincides well with experimental results.The stress distributions are further analyzed with the optimized scanning path based on the water-cooled scheme above.Computational results indicate that reasonable process-cooled conditions can reduce peak stresses and the temperature and stress gradients,and also demonstrate the feasibility and validity of this approach.More importantly,the water-cooled scheme can be easily implemented and remarkably improves the possibly-intended formability of the PDM.