往复式压缩机活塞杆断裂失效分析及疲劳寿命估算

发布时间：2018-02-27 07:32

本文关键词： 活塞杆疲劳断裂失效分析寿命估算　出处：《山东大学》2012年硕士论文　论文类型：学位论文

【摘要】：大型往复式压缩机作为过程工业生产中不可缺少的关键设备,其运行可靠性直接影响着过程工业生产,而活塞杆的早期疲劳断裂是活塞式压缩机运行事故的主要原因之一。如何通过对活塞杆疲劳断裂主要原因的分析,提出活塞杆的疲劳寿命估算方法,是本文作者的主要研究目标。本课题以山东华鲁恒升集团有限公司、中化平原化工有限公司、阳煤集团淄博齐鲁第一化肥有限公司、兖矿集团峄山化工有限公司与山东大学所达成协议为依托,以华鲁恒升提供的6M32型压缩机断裂的3根活塞杆为主要研究材料,进行了活塞杆断口宏观观测、微观断口扫描电镜观测、拉伸试验、冲击试验、硬度测试、化学成分测试、断裂位置尺寸测量、表面粗糙度测量等实验工作,分析了活塞杆疲劳断裂失效的主要原因。根据压缩机结构及实际运行参数,进行了活塞杆受力计算及断裂部位应力计算。考虑活塞杆工况、材质等的影响,筛选了基于活塞杆无损或微损检测的寿命预测模型,对其寿命进行了估算,对比了各种方法的估算寿命与实际运行寿命的差值。分析发现活塞杆疲劳裂纹主要在第二相组织或夹杂物位置萌生,名义应力法较适用于活塞杆疲劳寿命估算,载荷类型、平均应力、材料性能、金相组织、材料内部缺陷、缺口、尺寸效应、热处理及表面状态等对活塞杆疲劳寿命均有较大影响,Miner线性疲劳损伤理论及修正的Miner法则适用于活塞杆疲劳寿命估算。试验结果表明活塞杆疲劳断裂失效的主要原因为：材料的力学性能低于标准规定值；活塞杆断裂部位位于轴肩应力集中处,应力集中程度较大,降低了其疲劳寿命；在断裂处的应力集中与循环载荷的共同作用下材料发生疲劳损伤,逐渐产生疲劳裂纹导致疲劳破坏。活塞杆表面硬度和表面粗糙度对其疲劳寿命均有影响,表面硬化一定程度上可提高疲劳寿命,而表面粗糙度越小,疲劳性能越好。活塞杆常用材料42CrMo与38CrMoAl的抗拉强度与其布氏硬度的比值在3.4左右,工程中可根据表面硬度值估算活塞杆抗拉强度甚至其疲劳寿命。分析发现在不同的疲劳寿命估算方法中,控制疲劳寿命估算精度的主要因素是各方法对平均应力Re、应力幅ΔR/2、应力集中系数Kt、尺寸系数ε及表面系数β等的处理方式。在所选寿命的估算模型估算所得的寿命与实际运行寿命比较后得出,当使用基于Basquin公式的疲劳强度指数修正方法,其中系数采用四点法确定时,所估算结果与实际寿命最相近。
[Abstract]:As the indispensable key equipment in the process industry production, the operation reliability of the large reciprocating compressor directly affects the process industry production. The early fatigue fracture of piston rod is one of the main causes of the operation accident of piston compressor. By analyzing the main cause of fatigue fracture of piston rod, the method of estimating fatigue life of piston rod is put forward. It is the main research goal of the author. This subject is based on the agreement reached between Shandong Hualu Hengsheng Group Co., Ltd, Sinochem Plain Chemical Co., Ltd, Zibo Qilu first Fertilizer Co., Ltd., Yanzhou Mining Group Yishan Chemical Co., Ltd., and Shandong University. The fracture surface of piston rod was observed macroscopically, microscopic fracture electron microscope, tensile test, impact test, hardness test and chemical composition test were carried out with three piston rods of 6M32 compressor provided by Hua Luhengsheng as main research materials. The main causes of fatigue fracture failure of piston rod are analyzed in this paper. According to the structure of compressor and actual operation parameters, the main reasons of fatigue fracture failure of piston rod are analyzed. The stress calculation and fracture stress calculation of piston rod are carried out. Considering the influence of piston rod working condition and material, the life prediction model based on nondestructive or micro-loss detection of piston rod is selected, and its life is estimated. The difference between the estimated life of various methods and the actual operation life is compared. It is found that the fatigue crack of piston rod is mainly initiated in the second phase structure or inclusion position. The nominal stress method is more suitable for estimating the fatigue life of piston rod, load type, average stress, material properties, metallographic structure and internal defects of the material. The notch size effect heat treatment and surface state have great influence on the fatigue life of piston rod. The Miner linear fatigue damage theory and the modified Miner rule are suitable for estimating the fatigue life of piston rod. The test results show that the main causes of fatigue fracture failure of piston rod are: the mechanical properties of the material are lower than the standard value, the fracture position of piston rod is located at the stress concentration of the shaft shoulder, the stress concentration degree is large, and the fatigue life of the piston rod is reduced. Under the combined action of stress concentration at fracture and cyclic load, fatigue damage occurs and fatigue crack is gradually produced. The surface hardness and surface roughness of piston rod have influence on fatigue life. Surface hardening can improve fatigue life to some extent, but the smaller the surface roughness, the better the fatigue performance. The ratio of tensile strength to Brinell hardness of 42CrMo and 38CrMoAl is about 3.4. In engineering, the tensile strength and fatigue life of piston rod can be estimated according to the surface hardness. The main factors controlling the precision of fatigue life estimation are the treatment methods of average stress Ree, stress amplitude 螖 R / 2, stress concentration factor Kt, dimension coefficient 蔚 and surface coefficient 尾. The comparison between life and actual service life shows that, When the fatigue strength index correction method based on Basquin formula is used, and the coefficient is determined by the four-point method, the estimated results are most close to the actual life.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH45

【引证文献】