【作者】 杜洪奎；

【导师】 周昌玉；

【作者基本信息】 南京工业大学 ， 化工过程机械， 2004， 硕士

【摘要】 氢气压缩机机组曲轴箱体与中体联接螺栓的频繁断裂，给企业生产、安全造成极大危害。寻找故障发生的原因，制定可行的解决办法，不仅对用户的正常生产、安全有积极意义，而且对制定合适的检修周期具有指导意义。 本文的研究主要涉及压缩机热力、动力计算；螺纹联接结构力学分析；接触有限元计算：螺栓试样疲劳参数测试及验证性试验；螺栓疲劳寿命预测及可靠性研究：螺栓结构优化及延寿对策研究。其主要内容与结论如下： (1)通过压缩机热力、动力计算，对螺纹联接结构受力状况进行了详尽的分析，计算了压缩机气缸气体力、综合活塞力、滑道支反力，最后求出了联接螺栓所受的摩擦力及弯矩谱。从理论上说明了摩擦力及弯矩对螺栓应力状态的影响较小，并认为气体力及压缩机振动等引起的载荷是导致螺栓断裂失效的主要因素。 (2)螺纹联接结构三维接触有限元计算证明了摩擦力对螺栓结构的应力状态没有影响；通过螺纹联接结构轴对称接触有限元计算，精确计算了接触螺栓第一牙根处最大应力应变值，计算结果与实际断裂位置相符合。 (3)利用温度法模拟螺栓的预紧载荷，使接触有限元计算结果更符合实际。 (4)在轴对称模型有限元计算中，探讨了网格划分精度对计算结果的影响；并把轴对称模型下的粗网格有限元计算与三维模型有限元计算作了对比分析。 (5)由螺栓材料的疲劳试验，得到了材料的应变寿命曲线，并在此基础上，应用局部应力应变法计算了螺栓疲劳寿命，结果表明气体力不是导致螺栓失效的唯一因素。由现场测试数据进行螺栓疲劳寿命计算，表明寿命预测值与螺栓实际运行寿命相符合。螺栓试样疲劳验证性试验，结果表明本文采用的有限元计算方法及疲劳寿命计算公式是有效的，具有一定的计算精度。 (6)详尽分析了螺栓预紧力σ_p及材料疲劳强度指数b的分散性对螺栓疲劳寿命的影响。应用有限元计算结果得到的预紧力—寿命曲线 摘要 (o-，一N)可以通过螺栓变形图从理论得到很好的说明，二者结论是 一致的;由o-，一N曲线可知，适当增大预紧力可延长螺栓疲劳寿命。(7)根据中值S一N曲线及实验数据，推导出的P一S一N曲线，获得了在 不同失效概率下的螺栓疲劳寿命。(8)螺栓结构优化及加装碟形弹簧均可延长螺栓的疲劳寿命。更多还原

【Abstract】 The frequent fracture accidents of bolts, which connected hydrogen compressor crankshaft box with middle body, have caused enormous danger to normal production and safety. Looking for the reason of the faults, finding effective method to avoid failure is not only positive to production and safety, but also meaningful to decision of inspection period.In this paper, the problems were concerned with thermal and dynamical calculation of compressor, mechanics analysis of bolt joint structure, contact finite element calculation, fatigue life prediction and reliability study of bolt, bolt structure optimization and investigation of extending life technology and so on. The main contents and results were as follows:(1) By means of compressor thermal and dynamical calculation, bolt structure joint load condition was analyzed in detail. Gas force, general piston force and slider vertical force were calculated, and also friction and moment spectrum on bolt structure were given. Analysis results indicated that friction and moment have hardly an effect on stress of bolts, and load led by gas force and vibration of the compressor were the main reasons of fatigue fracture.(2) 3-dimension contact finite element calculation of bolt joint structure demonstrated that the effect of friction on bolt stress can be neglected. By means of axi-symmetrical contact FEA method, the exactly maximal stress and strain of the first root in bolt screw could be acquired.(3) Temperature method was used to simulate pre-tension load of the bolt, and the result were more applicable to practical condition.(4) In axi-symmetrical FEA method, the influence of mesh density on stress and strain and the results by axi-symmetrical FEA method were compared with that by 3-dimension FEA were also discussed.(5) The strain-life curve of bolt material based on the fatigue test was gained. The local stress-strain method was applied to calculate the fatigue life of the bolt. Theprediction results showed that gas force was not alone reason to lead the fatigue fracture of bolt. By the data in practice, the calculation results demonstrated that the life prediction was coincident with the practical life. The fatigue life of tested bolts also indicated that the prediction method was effective and more precise.(6) The influence of the scatter of pre-tension stress and fatigue intensity exponent on the bolt fatigue life was analyzed in detail. The results by the finite element method and local stress-strain method were well explained by bolt deformation plot in theory. The results also pointed that bolt fatigue life could be extended by increasing pre-tension stress .(7) According to S - N curve of bolt material and experiment results, P -S -N curves were plotted and bolt fatigue life under different failure probability was also acquired.(8) The fatigue life of bolt could be extended by optimization of bolt structure or appending of dish spring.更多还原