内含硬α夹杂钛合金轮盘裂纹扩展研究

为研究钛合金轮盘内部硬α夹杂疲劳裂纹扩展特性，对含预置硬α夹杂钛合金轮盘开展低循环疲劳裂纹扩展试验。结果表明:5229次循环后轮盘破裂；疲劳断口宏观、微观特征显示，预置硬α夹杂为本次疲劳破坏的疲劳源；在裂纹扩展前期，轮盘断口裂纹扩展速率较材料试验数据快；在裂纹扩展中期，断口裂纹扩展速率曲线呈对数线性关系；为了解决疲劳裂纹扩展后期疲劳条带不易识别的问题，使用等效裂纹扩展模型拟合断口裂纹扩展速率曲线，从而可以利用疲劳条带宽度来计算总寿命。同时，利用断口数据，提出和总结了预置硬α夹杂钛合金轮盘裂纹扩展特性仿真研究的方法。仿真研究显示:基于Paris公式建立裂纹扩展模型能较好地预测轮盘裂纹扩展特性；轮盘由于疲劳发生最终断裂破坏时，裂纹前沿的应力强度因子远大于断裂韧性，因此，不宜使用应力强度因子直接作为破裂准则。

Study on Crack Propagation of Titanium Alloy Disk With Preset Hard Alpha Inclusion

In order to study the fatigue crack growth characteristics of hard alpha inclusions in a titanium alloy disk, low cycle fatigue crack growth test was carried out on a titanium alloy disk with pre-set hard alpha inclusions. The results revealed that the disk ruptured after 5229 cycles. Macroscopic and microscopic characteristics of fatigue fracture showed that the preset hard-alpha inclusion was the fatigue source of the fatigue failure. In the early stage of crack growth, the crack growth rate of the disk is faster than that of material test data. In the middle stage of crack growth, the crack growth rate curve of fracture is logarithmic linear. In order to solve the fatigue problem in the later stage of fatigue crack growth, the crack growth rate curve of fracture surface was fitted using equivalent crack growth model. The total life can be calculated according to the width of fatigue striations. Meanwhile, based on fracture data, a simulation method for crack propagation characteristics of pre-set hard-alpha-inclusion titanium alloy disk was proposed and summarized. The simulation results showed that the crack growth model based on Paris formula could well predict the crack growth characteristics of the disk. When the disk is fractured finally under fatigue loading, the stress intensity factor at the front of the crack was much larger than the fracture toughness. Therefore, it is not suitable to use the stress intensity factor directly as the fracture criterion.