發(fā)布時(shí)間：2018-04-28 07:18

  本文選題：螺紋連接 + 扭矩系數(shù)��； 參考：《西北工業(yè)大學(xué)》2016年碩士論文

【摘要】：螺栓的低周疲勞是高溫螺紋連接中最主要的失效形式,同時(shí)在高溫下螺紋連接中的蠕變效應(yīng)也不容忽視,故研究螺栓的高溫蠕變和低周疲勞壽命具有非常重要的工程意義。本文對(duì)航空發(fā)動(dòng)機(jī)典型螺紋連接副的高溫蠕變和低周疲勞壽命進(jìn)行了研究,主要研究?jī)?nèi)容包括擰緊力矩與預(yù)緊力之間的關(guān)系及影響因素研究、法蘭螺紋連接的密封性能研究、螺紋連接的蠕變損傷研究和預(yù)緊螺紋連接的疲勞壽命預(yù)測(cè)方法研究。具體研究工作總結(jié)如下:1.針對(duì)采用扭矩法進(jìn)行預(yù)緊的螺紋連接,考慮螺旋升角、螺距等細(xì)節(jié),建立精確螺栓、螺母的螺紋模型,應(yīng)用ABAQUS對(duì)螺紋連接結(jié)構(gòu)的預(yù)緊過程進(jìn)行了有限元仿真,分析研究了擰緊力矩和螺栓預(yù)緊力的關(guān)系,并與理論結(jié)果做了比較分析,確定了所研究螺紋連接副的擰緊力矩系數(shù)范圍,分析了摩擦系數(shù)、螺距、彈性模量、裝配間隙和應(yīng)變硬化指數(shù)對(duì)扭矩系數(shù)的影響。2.采用有限元方法對(duì)法蘭螺紋連接結(jié)構(gòu)的密封性能進(jìn)行了研究,分析了在螺栓預(yù)緊力單獨(dú)作用和預(yù)緊力與工作壓力雙重作用兩種情況下,螺紋連接法蘭接觸面沿徑向與周向兩個(gè)方向上的接觸應(yīng)力分布,分析結(jié)果為法蘭螺紋連接結(jié)構(gòu)的密封性能評(píng)估提供了基礎(chǔ)。3.基于K-R蠕變損傷模型推導(dǎo)得出了應(yīng)力松弛損傷本構(gòu)方程,應(yīng)用有限元方法對(duì)高溫螺紋連接結(jié)構(gòu)的蠕變損傷、應(yīng)力松弛和壽命預(yù)測(cè)進(jìn)行了研究。分析了軸向拉力對(duì)螺紋連接結(jié)構(gòu)的蠕變損傷及壽命和應(yīng)力松弛對(duì)螺栓預(yù)緊力變化的影響。結(jié)果表明:應(yīng)力松弛對(duì)螺栓預(yù)緊力的變化有很大的影響,螺栓初始預(yù)緊力隨著蠕變時(shí)間的增加而降低直至趨于一個(gè)穩(wěn)定的值,之后螺栓的預(yù)緊力幾乎不變。當(dāng)螺栓的殘余預(yù)緊力小于螺栓正常工作所需的預(yù)緊力值時(shí),螺栓將會(huì)因應(yīng)力松弛引起的預(yù)緊力不足而導(dǎo)致螺紋連接結(jié)構(gòu)失效。4.針對(duì)預(yù)緊螺栓連接在受軸向循環(huán)拉力載荷作用下的高溫低周疲勞問題進(jìn)行了有限元分析與試驗(yàn)研究,提出了預(yù)緊螺紋連接的低周疲勞壽命預(yù)測(cè)模型,并將應(yīng)用所提出模型計(jì)算得出的螺栓疲勞壽命預(yù)測(cè)結(jié)果與螺栓低周疲勞壽命試驗(yàn)結(jié)果進(jìn)行了比較。結(jié)果表明,應(yīng)用所提出的疲勞壽命模型計(jì)算得出的結(jié)果能夠與試驗(yàn)結(jié)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.
【學(xué)位授予單位】：西北工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：V231

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相關(guān)期刊論文 前1條

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本文編號(hào)：1814317