Abstract
In this paper, the author studied the effects of different stress ratios（R） and stress concentration factors(Kt) on the fatigue properties of WSTi6211 titanium alloy.Through S-N curve, the author obtained the fatigue ultimate strength of the material under different conditions and analyzed characteristics of fatigue fractures, including the crack source sourse, the crack growth region and the final rupture region. The results show that when Kt=1, R=0.5, the fatigue ultimate strength σD is 626MPa; when Kt = 1, R=0.06, the fatigue ultimate strength σD is 527.5MPa; when Kt=3, R=0.06, the ultimate fatigue strength σD is 267MPa. Fatigue performance is very sensitive to R and Kt. The larger R is, the larger the fatigue ultimate strength is. The larger Kt is, the smaller the fatigue limit strength is. The fracture morphology shows typical fatigue fracture morphology. Most of the cracks originate on the surface of specimens and have typical fatigue bands. With the decrease of stress, the area of crack growth zone increases.
Highlights
1.Intrpduction "A generation of materials, a generation of equipment".[1]
In this paper, the author studied the effects of different stress ratios(R) and stress concentration factors(Kt) on the fatigue properties of WSTi6211 titanium alloy.Through S-N curve, the author obtained the fatigue ultimate strength of the material under different conditions and analyzed characteristics of fatigue fractures, including the crack source, the crack growth region and the final rupture region
The results show that when Kt=1, R=0.5, the fatigue ultimate strength σD is 626MPa; when Kt=1, R=0.06, the fatigue ultimate strength σD is 527.5MPa; when Kt=3, R=0.06, the ultimate fatigue strength σD is 267MPa
Summary
The experimental material is WSTi6211 titanium alloy bar with 300mm diameter. The phase transformation temperature is 995 ± 5 °C. 6.89 1.77 2.33 2.32 0.024 0.12 Bal. The microstructure of WSTi6211 titanium alloy bar is typical equiaxed structures processed in two-phase zone. The content of α phase is about 70% and the size is about 10-20 m. The high cycle fatigue properties of the alloy were tested by group method and lifting method, and the S-N curve was drawn. The conditional fatigue ultimate strength of the alloy was determined by lifting method formula. The sample size is shown in Fig.. The characteristics of fatigue crack source, propagation zone and instantaneous fracture zone from high stress zone to low stress zone were observed. The sensitivity of the alloy to stress ratio and stress concentration factor was analyzed
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