循环热—机械载荷下压力管道的棘轮极限研究

发布时间：2018-03-30 19:49

  本文选题：棘轮边界　切入点：安定性　出处：《武汉工程大学》2016年硕士论文

【摘要】：压力管道和压力容器广泛应用于化工,石油,军事和核电站等领域。这些构件通常承受稳定载荷和循环载荷的一个组合载荷,由于过量的塑性变形累积,而发生棘轮失效,严重影响安全性。由于理论推导的复杂性,世界各国标准中仅包含循环热-内压载荷下薄壁圆筒棘轮极限解析解(Bree图),尚缺乏复杂载荷下压力管道棘轮极限解析解。为保障复杂载荷工况下压力管道的安全性,本文采用非循环法系统地推导了工程领域中常见复杂循环组合载荷下压力管道棘轮极限的解析解,并提出了相应的设计方法,主要工作及结论如下:(1)由重力等因素引起的轴向压缩应力会显著降低结构的棘轮极限。压力管道的棘轮极限会随着径比的增大而显著增加。(2)本文所提出的设计方法的特征是采用Von-Mises屈服准则,将承压外壳的组合载荷条件分为稳定载荷和循环载荷两部分。推导出的这些复杂载荷条件下压力管道棘轮极限包括:循环温度梯度和恒定内压组合载荷下压力管道的棘轮极限,循环温度梯度和恒定内压组合载荷下压缩端压力管道的棘轮极限,循环温度梯度和恒定弯矩组合载荷下压力管道的棘轮极限,循环温度梯度和恒定扭矩组合载荷下压力管道的棘轮极限,循环温度梯度和恒定弯扭组合载荷下压力管道的棘轮极限,循环扭矩和恒定内压组合载荷下压力管道的棘轮边界,循环扭矩和恒定弯矩组合载荷下压力管道的棘轮边界,循环弯矩和恒定扭矩组合载荷下压力管道的棘轮边界,以及循环弯矩载荷下内压直管的棘轮极限的解析解。(3)实验测试了500℃温度下20CrMo钢的单轴拉伸试验和单轴棘轮试验。结合实验数据分析了20CrMo钢的棘轮效应演变规律,最终确定了其棘轮极限的范围为200MPa~300 MPa。(4)本文所得到的解拓展了经典Bree评定图的适用范围,而且压力管道在循环热-机械载荷及类似工况下的棘轮极限能够采用所提出的相应设计方法进行评估,这种方法在工程上的适用性也很广泛,为复杂载荷条件下压力管道的棘轮极限工程设计奠定理论基础。
[Abstract]:Pressure pipes and pressure vessels are widely used in chemical, petroleum, military and nuclear power plants.These components usually bear a combined load of stable load and cyclic load. Due to the accumulation of excessive plastic deformation ratchet failure occurs which seriously affects the safety.In order to ensure the safety of pressure pipeline under complex load condition, the analytical solution of ratchet limit of pressure pipeline under common complex cyclic combined loads in engineering field is deduced systematically by using the non-cyclic method, and the corresponding design method is put forward.The main work and conclusions are as follows: (1) the axial compression stress caused by gravity and other factors can significantly reduce the ratchet limit of the structure.The ratchet limit of pressure pipeline will increase significantly with the increase of diameter ratio. The characteristic of the design method proposed in this paper is that the combined load condition of the confined shell can be divided into two parts: stable load and cyclic load using Von-Mises yield criterion.The ratchet limit of pressure pipeline under these complex load conditions is derived, which includes the ratchet limit of pressure pipeline under cyclic temperature gradient and constant internal pressure combined load.Ratchet limit of compression end pressure pipeline under cyclic temperature gradient and constant internal pressure combined load, ratchet limit of pressure pipe under cyclic temperature gradient and constant bending moment,Ratchet limit of pressure pipeline under combined load of cyclic temperature gradient and constant torque, ratchet limit of pressure pipe under combined load of cyclic temperature gradient and constant bending and torsion, ratchet boundary of pressure pipeline under combined load of cyclic torque and constant internal pressure,Ratchet boundary of pressure pipeline under combined load of cyclic torque and constant bending moment, ratchet boundary of pressure pipe under combined load of cyclic moment and constant torque,The uniaxial tensile test and uniaxial ratchet test of 20CrMo steel at 500 鈩，

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