航空发动机典型螺纹连接副高温蠕变和疲劳寿命研究

发布时间：2018-04-28 07:18

本文选题：螺纹连接 + 扭矩系数　；参考：《西北工业大学》2016年硕士论文

【摘要】：螺栓的低周疲劳是高温螺纹连接中最主要的失效形式,同时在高温下螺纹连接中的蠕变效应也不容忽视,故研究螺栓的高温蠕变和低周疲劳寿命具有非常重要的工程意义。本文对航空发动机典型螺纹连接副的高温蠕变和低周疲劳寿命进行了研究,主要研究内容包括拧紧力矩与预紧力之间的关系及影响因素研究、法兰螺纹连接的密封性能研究、螺纹连接的蠕变损伤研究和预紧螺纹连接的疲劳寿命预测方法研究。具体研究工作总结如下:1.针对采用扭矩法进行预紧的螺纹连接,考虑螺旋升角、螺距等细节,建立精确螺栓、螺母的螺纹模型,应用ABAQUS对螺纹连接结构的预紧过程进行了有限元仿真,分析研究了拧紧力矩和螺栓预紧力的关系,并与理论结果做了比较分析,确定了所研究螺纹连接副的拧紧力矩系数范围,分析了摩擦系数、螺距、弹性模量、装配间隙和应变硬化指数对扭矩系数的影响。2.采用有限元方法对法兰螺纹连接结构的密封性能进行了研究,分析了在螺栓预紧力单独作用和预紧力与工作压力双重作用两种情况下,螺纹连接法兰接触面沿径向与周向两个方向上的接触应力分布,分析结果为法兰螺纹连接结构的密封性能评估提供了基础。3.基于K-R蠕变损伤模型推导得出了应力松弛损伤本构方程,应用有限元方法对高温螺纹连接结构的蠕变损伤、应力松弛和寿命预测进行了研究。分析了轴向拉力对螺纹连接结构的蠕变损伤及寿命和应力松弛对螺栓预紧力变化的影响。结果表明:应力松弛对螺栓预紧力的变化有很大的影响,螺栓初始预紧力随着蠕变时间的增加而降低直至趋于一个稳定的值,之后螺栓的预紧力几乎不变。当螺栓的残余预紧力小于螺栓正常工作所需的预紧力值时,螺栓将会因应力松弛引起的预紧力不足而导致螺纹连接结构失效。4.针对预紧螺栓连接在受轴向循环拉力载荷作用下的高温低周疲劳问题进行了有限元分析与试验研究,提出了预紧螺纹连接的低周疲劳寿命预测模型,并将应用所提出模型计算得出的螺栓疲劳寿命预测结果与螺栓低周疲劳寿命试验结果进行了比较。结果表明,应用所提出的疲劳寿命模型计算得出的结果能够与试验结果很好的吻合。
[Abstract]:The low cycle fatigue of bolts is the main failure form in high temperature thread connection, and the creep effect in high temperature thread connection can not be ignored, so it is very important to study the high temperature creep and low cycle fatigue life of bolt. In this paper, the high temperature creep and low cycle fatigue life of typical threaded joint of aero-engine are studied. The main research contents include the relationship between tightening torque and pretightening force and the influencing factors, and the sealing performance of flange thread connection. Research on creep damage of thread connection and prediction method of fatigue life of pretension thread connection. The concrete research work is summarized as follows: 1: 1. Considering the details of helical angle and pitch, the thread model of precise bolt and nut is established, and the pretightening process of thread connection structure is simulated by using ABAQUS, which is based on the method of torque, and considering the details of helical angle and pitch, the pretightening process of thread connection structure is simulated by finite element method (ABAQUS). The relationship between tightening torque and bolt pretightening force is analyzed and compared with the theoretical results. The range of tightening torque coefficient is determined, and the friction coefficient, pitch, elastic modulus are analyzed. The influence of assembly clearance and strain hardening index on torque coefficient. The sealing performance of flange thread connection structure is studied by finite element method. The distribution of contact stress along the radial and circumferential direction of the contact surface of the threaded joint flange provides a basis for evaluating the sealing performance of the flanged threaded connection structure. Based on the K-R creep damage model, the constitutive equation of stress relaxation damage is derived. The creep damage, stress relaxation and life prediction of high temperature threaded connection structures are studied by finite element method. The effects of axial tensile force on creep damage of threaded connection structure and the influence of life and stress relaxation on the change of bolt pretightening force are analyzed. The results show that the stress relaxation has a great influence on the change of bolt pretightening force. The initial pretightening force of bolt decreases with the increase of creep time until it tends to a stable value, and then the pretightening force of bolt is almost unchanged. When the residual preloading force of the bolt is less than the pre-tightening force required for the normal operation of the bolt, the bolt will lead to the failure of the threaded connection structure due to the insufficient pretightening force caused by the stress relaxation. In this paper, finite element analysis and experimental study on high temperature and low cycle fatigue of preloaded bolt connections under axial cyclic tensile load are carried out, and a prediction model of low cycle fatigue life of preloaded thread connections is proposed. The prediction results of bolt fatigue life calculated by the proposed model are compared with the results of bolt low cycle fatigue life test. The results show that the calculated results from the proposed fatigue life model are in good agreement with the experimental results.
【学位授予单位】：西北工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V231

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