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.