残余应力对定向能量沉积不锈钢件疲劳裂纹扩展速率的影响机制研究  

Effects of Residual Stress on Fatigue Crack Propagation Rate of Directed Energy Deposited Stainless Steel Parts

作　　者：段成红[1] 尚大智 罗翔鹏[1] 池瀚林 曹先堃 郝晓杰 Duan Chenghong;Shang Dazhi;Luo Xiangpeng;Chi Hanlin;Cao Xiankun;Hao Xiaojie(College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology,Beijing 100029,China)

机构地区：[1]北京化工大学机电工程学院,北京100029

出　　处：《中国激光》2023年第20期122-130,共9页Chinese Journal of Lasers

基　　金：国家自然科学基金重点项目(52235006);国家重点研发计划(2016YFB1100202-1)。

摘　　要：为明晰残余应力对定向能量沉积(DED)成形316L奥氏体不锈钢疲劳裂纹扩展行为的影响机制,笔者通过与传统316L不锈钢热轧板材疲劳裂纹扩展速率的对比,研究了热处理工艺对DED 316L奥氏体不锈钢件疲劳裂纹扩展速率的影响,并采用有限元方法探究了残余应力对应力强度因子和有效应力比的定量化影响规律。结果表明:有限元法得到的疲劳寿命与试验结果吻合得较好,疲劳寿命预测误差约为4.71%。基于Walker公式的残余应力强度因子Kres通过增加有效应力比影响DED不锈钢件的疲劳裂纹扩展速率。当循环载荷应力比为R=0.1时,DED不锈钢件的有效应力比Reff为0.122,而经去应力热处理的DED不锈钢件的有效应力比Reff降为0.117,从而降低了DED不锈钢件的疲劳裂纹扩展速率。Objective 316L stainless steel is widely used in large-pressure equipment parts in the petroleum and chemical industries.Improving the fatigue performance of parts is critical for maximizing the remaining material value.Directed energy deposition(DED)technology has the advantages of high forming flexibility and a short processing cycle,and is considered one of the best choices for pressure equipment remanufacturing.However,defects such as poor surface finish and the generation of tensile residual stresses occur during the DED process.The heat treatment process is typically used to reduce the internal stress of a material to improve its fatigue performance,which is explained in terms of microscopic grain modulation.However,few quantitative studies have been conducted on the residual stress-induced fatigue performance of parts.Therefore,in this study,the finite element method was used to investigate the quantitative influence of residual stress on fatigue crack propagation(FCP)behavior under different heat treatment processes.Methods 316L stainless steel was employed in this study.Initially,3D finite element models of DED and compact tensile(CT)specimens were developed.Subsequently,the effect of different heat treatment processes on the FCP rate of the DED 316L stainless steel parts was investigated by comparing it with conventional 316L stainless steel hot-rolled plates using a combination of experiments and numerical simulations.Based on the virtual crack closure technique,the quantified influence rules of the residual stress on the stress intensity factor(SIF)and effective stress ratio were examined.Finally,the specimen fracture morphology was analyzed using scanning electron microscopy.Results and Discussions The residual stress distribution of DED stainless steel parts was accurately calculated using finite element simulation with an error of approximately 5.05%(Fig.4).The simulated specimen fatigue life matched the experimental results well with an error of approximately 4.71%(Fig.5).The effect of the SIF(Kre

关 键 词：激光技术 裂纹扩展速率 残余应力 应力强度因子 定向能量沉积 

分 类 号：TG142.71[一般工业技术—材料科学与工程]