加工残余应力对Ti-6Al-4V试样高周疲劳性能的影响

Effect of machining residual stress on high cycle fatigue property of Ti-6Al-4V specimens

为探究加工残余应力对高周疲劳性能的影响,以Ti-6Al-4V材料为研究对象,测试获得了相同表面粗糙度、不同表面残余应力试样的高周疲劳性能。结果表明,该材料的疲劳试样在加工时会产生较高的残余压应力,不同加工工艺下的试样表面残余应力变化较大;在残余应力-寿命双对数坐标下,试样表面残余压应力和疲劳寿命近似成线性关系。随着应力幅的降低,残余压应力对疲劳寿命的提升越来越明显,加工表面残余压应力最高可使疲劳寿命增大约350倍;表面残余压应力从-100 MPa增大到-230 MPa和-430 MPa时,疲劳极限强度分别增大约13.6%和18.2%。为此,在进行Ti-6Al-4V合金高周疲劳性能测试时,必须控制试样表面残余应力水平,以确保数据的可靠性、降低数据的分散性,推荐对加工后试样进行严格的消除残余应力处理。

To explore the influence of machining residual stress on fatigue property,the high-cycle fatigue property testing was carried out using numerous specimens of Ti-6Al-4V alloy with the same surface roughness and different surface residual stresses as the research objects.The results show that relative high compressive residual stresses will be produced on the specimen surface during machining,which vary greatly under different machining conditions.In a double logarithmic coordinate system,the curve of surface residual stress versus the fatigue life shows a nearly linear relation.As the stress amplitude decreases,the effect of residual compressive stress on the fatigue life becomes more and more obvious.The compressive residual stress of the machined surface can increase the fatigue life by about 350 times at maximum.When the surface compressive residual stress increases from-100 MPa to-230 MPa and-430 MPa,the fatigue ultimate strength increases by about 13.6%and 18.2%,respectively.Therefore,when testing the high-cycle fatigue performance of Ti-6Al-4V alloy,it is necessary to control the level of residual stress on specimen surface in order to ensure the measuring reliability and reduce the dispersion of test data.It is recommended that strict residual stress relief treatment should be applied on the specimens before testing.