空心叶片激光快速成形过程的温度/应力场数值模拟

针对航空发动机空心涡轮叶片激光快速成形(LRF),建立了温度场/应力场瞬态模型,采用有限单元生死技术模拟了熔覆层的沉积生长过程.采用随动强化及米塞斯屈服准则进行了热弹塑性分析,通过间接耦合模拟了TC4钛合金空心叶片激光快速成形的温度场/应力场演变过程.结果分析表明,在TC4钛合金空心叶片激光快速成形过程中,随着熔池的移动和成形高度的增加,温度场和应力场动态演化,其中由于基座的冷却及约束作用和熔池加热及应力释放作用,激光快速成形空心叶片温度和应力/应变场沿高度(z轴)方向呈梯度分布.温度场上高下低,散热方向从上至下,从熔池到基座;应力场下高上低,叶根等效应力最大.空心叶片激光快速成形结束冷却到室温,残余应力与熔覆过程应力分布规律基本相同,只是叶片顶部等效应力有所提高.

Temperature/Stress Field Numerical Simulation of Hollow Blade Produced by Laser Rapid Forming

A transient temperature/stress field finite-element model for the laser rapid forming(LRF) process of a hollow blade of aeroengine is developed.The deposition process is simulated with the finite element birth and death technology,the thermo-plastics is analyzed by bilinear isotropic hardening and Von Mises yield criteria,and the indirectly coupled temperature/stress field evolution during the LRF process of a TC4 alloy hollow blade is simulated.The results show that during the LRF process of a TC4 alloy hollow blade,the temperature/stress field in the TC4 alloy hollow blade is dynamically developed with the movement of melting pool and increase of forming height.For the reason of cooling/constrain effect of the substrate and heating/stress-release effect of the melting pool,the temperature/stress field gradient distributes along the altitude direction.The temperature declines from the top to the bottom,and the heat dispersing direction was from the top to the bottom i.e.,from the melting pool to the substrate.The stress field increases from the top to the bottom,and reaches a maximum at the bottom of the blade.When the blade was cooled to room temperature,the residual stress distribution is similar to that in the cladding process,expect for a larger stress at the top of the blade.