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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

  • 摘要: 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。

     

    Abstract: 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, thewatercooled scheme can be easily implemented and remarkably improves the possibly-intended formability of the PDM.

     

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