关键词: 疲劳, 裂纹萌生, 粉末合金, 涡轮, 数值模型, 数值仿真

Abstract:

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.

Key words: fatigue, crack initiation, powder metallurgy, turbine, numerical model, numercal simulation