TC4 alloy components with complicated geometries can be directly fabricated using selec-tive laser melting(SLM)at a low cost.These components are often used under complex service condi-tions.Thus,it is important to investigate the effects of the stress ratio(R)on the fatigue crack growth(FCG)rate(da/dN)in SLM TC4 alloys with defects at the steady state to develop guidelines for damage-tolerance design and fatigue life assessment.In this work,SLM TC4 alloys containing two different micro-defects were used to qualitatively examine the effect of the defect size on the da/dN at the steady state.In addition,comparative studies using an alloy with smaller defect sizes were performed at the steady state and at R = 0.1,0.3,and 0.5.The relationship between the da/dN and stress intensity factor range(ΔK)was plotted and analyzed by fitting the Paris formula.The results show that the Paris formula param-eter,m,is constant and the parameter,C,increases,which means that the increase in the defect size in-creases the da/dN.The da/dN increases with an increase in R,and the da/dN curves converge at low ΔK,which are reflected in the increase in the parameter,m,and the decrease in the parameter C.Addi-tionally,there is a linear relationship between m and lgC(the common logarithm of C),which is not affect-ed by R.Finally,the change patterns in the da/dN caused by the microdefects and R were analyzed along with the fatigue damage mechanisms.
关键词
选区激光熔化/TC4合金/缺陷/应力比/疲劳裂纹扩展速率/Paris公式
Key words
selective laser melting/TC4 alloy/defect/stress ratio/fatigue crack growth rate/Paris formula
维普
万方数据