珠光体重轨钢疲劳裂纹尖端的应力应变场  

Stress-Strain Field at the Fatigue Crack Tip of Pearlite Heavy Rail Steel

作　　者：岑耀东 计春娇 包喜荣[1] 王晓东 陈林[1] 董瑞 CEN Yaodong;JI Chunjiao;BAO Xirong;WANG Xiaodong;CHEN Lin;DONG Rui(School of Materials Science and Engineering,Inner Mongolia University of Science and Technology,Baotou 014010,China)

机构地区：[1]内蒙古科技大学材料科学与工程学院,包头014010

出　　处：《材料研究学报》2024年第9期711-720,共10页Chinese Journal of Materials Research

基　　金：内蒙古自治区重点研发和成果转化计划(2023YFHH0036);内蒙古自治区直属高校基本科研业务费项目(2023QNJS002,2023YXXS007,2024YXXS039);内蒙古自然科学基金(2024LHMS05033);国家自然科学基金(52161008)。

摘　　要：用扫描电镜(SEM)观察不同冷速的在线轧态、在线热处理态、实验室热处理态(冷速递增)珠光体重轨钢的珠光体片层,用疲劳试验机和应变仪测定重轨钢的拉-拉疲劳实验中长度不同的裂纹尖端应变场云图并基于Abaqus建立应力和应变模型,研究重轨钢的疲劳裂纹尖端的力学行为。结果表明:随着冷速的递增珠光体片层的间距递减,随着疲劳裂纹的扩展裂纹周围的应力场强和裂纹尖端的应力强度因子K增大,应力场呈显著的“蝴蝶状”,其中实验室热处理态重轨钢长度为1、2、3 mm处裂纹的应力强度因子K分别为13.53、14.58和15.54 MPa·m^(1/2),远比相同裂纹长度的在线轧态和在线热处理态重轨钢的大。随着疲劳裂纹长度的增大,裂纹尖端附近等效应变区域增大。三种冷速的重轨钢的裂纹长度相同时,随着珠光体片层间距的递减裂纹尖端等效应变值随之递减,裂纹长度为较长的3 mm时等效应变值模拟结果分别为0.074、0.067、0.055,而应变实验分别为0.082、0.064、0.058。模拟仿真结果与应变场实验结果最大误差为9.7%,验证了模型的可靠性。模拟和实验结果均表明,重轨钢珠光体片层间距越小则扩展过程中的疲劳裂纹其尖端的应力强度因子K越大,产生的等效应变越小,其抵抗断裂能力越强和疲劳性能越高。The fatigue crack propagation of heavy rail steel has a very complex relationship with the stress and strain at the crack tip,but there is currently little research on this mechanism.This article takes pearlite heavy rail steel as the research object under three conditions(increasing cooling rate):online rolling state,online heat treatment state,and laboratory heat treatment state.The pearlite layers at different cooling rates were observed using scanning electron microscopy,and the tensile fatigue crack and stress field cloud map at the crack tip of the heavy rail steel were measured using fatigue testing machines and strain gauges.Then,a stress and strain model was established based on Abaqus,the results indicate that as the cooling rate increases,the interlayer spacing of pearlite decreases;With the fatigue crack propagation,the stress field strength around the crack and the Stress intensity factor k at the crack tip increase,and the stress field is more significant in the"butterfly"shape.The Stress intensity factor of the laboratory heat treated heavy rail steel at the crack length of 1,2,3 mm is 13.53,14.58,and 15.54 MPa·m^(1/2),respectively,which is far greater than that of the rolled and heat treated heavy rail steel at the same crack length;As the fatigue crack length increases,the equivalent strain area near the crack tip increases.At the same crack length,the equivalent strain at the crack tip of three kinds of heavy rail steels with cooling rate decreases with the decrease of pearlite lamellae.The simulation results of equivalent strain at a longer crack length of 3 mm are 0.074,0.067 and 0.055 respectively,while the strain experimental results are 0.082,0.064 and 0.058 respectively.The maximum error between the simulation results and the strain field experimental results is 5.1%,which verifies the model.Both simulation and experimental results show that the smaller the pearlite lamella is,the larger the Stress intensity factor at the crack tip is during the fatigue crack growth process of heavy rail

关 键 词：金属材料 重轨钢 组织 疲劳断裂 裂纹扩展 应力应变 

分 类 号：TG111[金属学及工艺—物理冶金]