喷丸强度和表面覆盖率对TC4钛合金室温疲劳性能的影响

Effect of shot peening intensity and surface coverage on room-temperature fatigue property of TC4 titanium alloy

采用多种喷丸强度和表面覆盖率对TC4钛合金进行喷丸。对比了表面粗糙度、残余应力场和表面形貌,并分析了室温旋弯疲劳性能。结果表明,表面粗糙度、残余压应力深度和最大残余应力位置随强度增大而增大,表面残余应力数值随喷丸强度增大而减小。覆盖率较大时,表面出现金属折叠形貌。喷丸强化提高了旋弯疲劳性能。相比于磨削状态的中值疲劳估计量5.06×10^4周次,0.12 mmA强度喷丸后提高到5.12×10^6~5.28×10^6周次,而0.25 mmA强度喷丸后为3.28×10^6~4.23×10^6周次,疲劳寿命随强度增大而下降。覆盖率增大对于低强度(0.12 mmA)喷丸疲劳寿命无明显影响,而强度较高(0.25 mmA)时,当表面覆盖率由125%提高到600%时,疲劳寿命由4.23×10^6周次下降到3.28×10^6周次。在考虑外载表面应力集中和喷丸残余应力的前提下,计算了喷丸后实际应力较大的危险截面位置,并采用断口分析进行验证。

TC4 titanium alloy was shot-peened by multiple kinds of intensity and surface coverage.Surface roughness and topography,residual stress profile were compared.Moreover room-temperature rotating-bending fatigue property was tested.The results show when the intensity is raised,the surface roughness,the depth of residual compressive stress depth and the location of the maximum residual stress are increased and the surface residual stress is decreased.The enfoldment appears on the surface with the increase of surface coverage.Rotating-bending fatigue property is enhanced by shot-peening.Compared with median fatigue life estimated value of 5.06×10^4 cycles at grinding state,the fatigue cycles ranges are raised to 5.12×10^6-5.28×10^6 cycles after shot-peened at the intensity 0.12 mmA and 3.28×10^6-4.23×10^6 cycles at 0.25 mmA,indicating that the fatigue property is decreased with the increase of the intensity.By comparison,when the intensity is low(0.12 mmA),the coverage has no impact on the fatigue property.However,fatigue cycles decline from 4.23×10^6 cycles to 3.28×10^6 cycles when the coverage is inclined from 125%to 600%and the intensity is relatively high(0.25 mmA).Furthermore,on the premise of considering the surface stress concentration of the external load and the residual stress of shot peening,the position of the dangerous section with large actual stress after shot peening is calculated and verified by the fracture analysis.