高强螺栓受力及疲劳性能研究

发布时间：2018-05-11 19:42

本文选题：高强螺栓 + 应力集中　；参考：《湖南大学》2013年硕士论文

【摘要】：高强螺栓连接以其强度高、可拆卸等优点而成为了一种重要的钢结构连接形式。由于该连接受力机理复杂,目前仍有较多问题值得探讨。我国现行规范一方面低估了某些情况下的承载力,例如,高强螺栓承压型连接的抗剪承载能力规定；另一方面,现行规范缺乏对某些情况下承载力的规定,例如,规范缺少高强螺栓在受拉情况下疲劳计算的规定。本文采用理论推导及数值试验的方法,对这两个问题进行了深入的研究,获得了如下成果： (1)采用虚功原理推导了预拉力模拟方法,该方法可以较为准确的模拟预应力的工作。 (2)采用了数值试验的方法研究了承压型高强螺栓的受力过程。研究表明当连接的承载力由螺栓强度控制时,若不考虑构件间的摩擦力,则高强螺栓承压型连接的承载力会被低估。本文对这种连接方式的抗剪承载力提出了为合理的计算方法。 (3)通过理论推导及数值试验的方法研究了螺栓杆的应力集中系数。在忽略螺纹升角的情况下,根据变形协调条件研究了螺栓杆的轴力梯度变化。采用数值计算确定常用螺栓球的螺纹位移系数及螺纹力计算公式。采用局部建模,通过迭代计算的方法确定螺栓杆应力集中系数。与完整模型的计算结果比较表明该方法的计算结果具有较高的精度,且计算效率高。 (4)针对应用最普遍的40Cr钢制高强螺栓,在计算出的螺栓螺纹应力集中系数的情况下,采用2种S-N曲线法对高强螺栓的疲劳寿命进行了估算。并结合等寿命曲线综合考虑了应力幅和应力比的影响,推导出了螺栓疲劳的设计公式。将估算结果与国内已有的实验数据进行对比,估算结果偏于安全,且在高周期疲劳中精度较好。 (5)采用断裂力学分析了螺栓螺纹根部表面Ⅰ型裂纹的应力强度因子,对带有不同长度初始裂纹的螺栓进行了寿命估算,研究了不同长度裂纹对高强螺栓疲劳寿命的影响。并按照工程中假设初始裂纹为0.5mm时的疲劳寿命为螺栓的疲劳寿命,与实验数据对比表明假设初始裂纹为0.5mm的估算寿命偏于安全且精度较好。并且证明了初始裂纹长度对螺栓疲劳寿命有着不可忽视的影响。
[Abstract]:High-strength bolt connection has become an important form of steel structure because of its high strength and detachability. Due to the complex mechanical mechanism of the connection, there are still many problems to be discussed. On the one hand, the current code of our country underestimates the bearing capacity in some cases, for example, the shear bearing capacity of high-strength bolt bearing connections; on the other hand, the current code lacks the provisions on the bearing capacity in some cases, such as, The specification lacks provisions for fatigue calculation of high-strength bolts under tension. In this paper, the theoretical derivation and numerical test are used to study these two problems, and the results are as follows: 1) the simulation method of pretension force is deduced by using the principle of virtual work, which can simulate the work of prestress accurately. (2) the stress process of high-strength bolt with bearing pressure is studied by numerical test. The results show that when the bearing capacity of the connection is controlled by the bolt strength, the bearing capacity of the high-strength bolt bearing joint will be underestimated if the friction between the members is not taken into account. This paper presents a reasonable calculation method for the shear capacity of this connection. The stress concentration factor of bolt rod is studied by theoretical derivation and numerical test. In this paper, the axial force gradient of bolt rod is studied according to the deformation coordination condition, while the screw lift angle is ignored. The displacement coefficient of thread and the calculation formula of thread force are determined by numerical calculation. The stress concentration factor of bolt rod is determined by means of local modeling and iterative calculation. The comparison of the results with the complete model shows that the proposed method has high accuracy and high efficiency. The fatigue life of high strength bolts made of 40Cr steel is estimated by using two S-N curve methods under the calculated stress concentration factor of bolt thread. Considering the influence of stress amplitude and stress ratio, the design formula of bolt fatigue is deduced. The estimated results are compared with the experimental data available in China. The estimated results are relatively safe and have good accuracy in high cycle fatigue. In this paper, the stress intensity factor of mode I crack at the root of bolt thread is analyzed by fracture mechanics. The life of bolt with initial crack of different length is estimated, and the influence of crack of different length on fatigue life of high strength bolt is studied. The fatigue life of bolts is assumed to be the fatigue life of bolts when the initial crack is assumed to be 0.5mm. The comparison with the experimental data shows that the estimated life of the initial crack assuming that the initial crack is 0.5mm is more safe and accurate. The effect of initial crack length on the fatigue life of bolts is proved.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU391

【参考文献】