基于材料微观特性的涡轮盘疲劳裂纹萌生寿命数值仿真

 为了研究材料微观特性对结构疲劳寿命的影响,根据Tanaka-Mura疲劳裂纹萌生寿命计算理论,模拟某镍基粉末合金涡轮盘喉道表面疲劳裂纹萌生寿命。利用泰森多边形生成法,模拟微观多晶结构,建立宏-细观模型相结合的三维仿真模型。实现3项关键技术:1)在三维模型中模拟了面心立方晶体中{111}面族的12条主滑移系;2)应用缺口根部裂纹萌生的Tanaka-Mura理论模型模拟一条微裂纹在另一条裂纹尖端萌生;3)模拟了微裂纹的起裂、扩展与联合过程,最终形成一条宏观裂纹。对某表面带刀痕涡轮盘疲劳裂纹萌生寿命数值仿真结果与真盘试验结果相差20%。研究表明,减小晶粒尺寸、降低表面粗糙度、形成表面压缩残余应变以及析出沉淀颗粒都有利于提高涡轮盘的疲劳裂纹萌生寿命。

Numerical Simulation of Fatigue-crack-initiation Life for Turbine Disk Based on Material Microcosmic Characteristics

To study the influence of material microcosmic characteristics on structural fatigue life,the fatigue-crack-initiation life in the throat surface of a Ni-based sintered alloy turbine disk is simulated based on Tanaka-Mura numerical theory models. A 3D simulation model is established with combined macro-micro models, where the polycrystalline material is simulated using the Voronoi tessellation. Three key techniques are achieved: 1) crack initiation is realized along 12 principal slip systems on {111} octahedral slip planes of face centered cubic (FCC) crystals in 3D models; 2) the Tanaka-Mura theory of fatigue crack initiation from notches is applied to simulate crack initiation from another crack tip; 3) the process of micro-crack nucleation, propagation and coalescence is simulated, and a macro-crack is finally formed. The simulated fatigue-crack-initiation life of a turbine disk with a nick has a discrepancy of 20%, compared with the turbine disk fatigue testing result. The study indicates that, finer grains, smoother surfaces, compressed surface residual strain, and precipitates are beneficial to the increase of turbine disk fatigue-crack-initiation life.