【摘要】 为研究膨胀节壁厚不均匀减薄对承载能力的影响，针对单层单波U形波纹管膨胀节的液压成形过程进行有限元数值模拟，分析了壁厚不均匀减薄和管坯壁厚（t）、膨胀节波峰/波谷内壁曲率半径相对大小（r/D_b），以及膨胀节波高相对大小（h/D_b）对液压成形膨胀节波峰壁厚减薄率大小的影响。结果表明，t,r/D_b对壁厚减薄率的影响可以忽略，而壁厚减薄率随着h/D_b的增大而增大，基本呈线性关系。在数值模拟基础上进一步拟合得到壁厚减薄率与h/D_b的关联式，关联式计算结果相对误差在10%左右，满足工程设计要求。建立基于名义厚度、等效壁厚、液压成形后三种膨胀节模型，采用极限载荷法分析三种膨胀节模型的承压能力。定义了承压能力变化的强度减弱系数，发现液压成形后膨胀节承压能力均有所降低，且强度减弱系数主要受壁厚减薄率影响，最后拟合得到了强度减弱系数与波峰处壁厚减薄率的关联式。研究结果为U形膨胀节的设计和强度安全评定提供重要参考。更多还原

【Abstract】 In order to investigate the influence of uneven wall-thinning on the load-bearing capacity of expansion joints,this paper conducts a finite element simulation of the hydroforming process for single-layer,single-wave U-shaped bellows expansion joints.It analyzes the effects of non-uniform wall thinning,the tube blank wall thickness(t),the relative size of the inner wall curvature radius at the expansion joint peak/trough(r/D_b),and the relative wave height( h/D_b) on the wall thinning rate at the peak of the hydroformed expansion joint.The results indicate that the influences of t and r/Db on the wall thinning rate are negligible,whereas the wall thinning rate increases with h/Db,showing an approximately linear relationship.Based on the numerical simulations,a correlation between the wall thinning rate and h/Db is further fitted.The relative error of the calculated results from this correlation is around 10%,which meets engineering design requirements.Three expansion joint models are established based on the nominal thickness,equivalent wall thickness,and post-hydroforming thickness,and their pressure-bearing capacities are analyzed using the limit load method.A strength weakening coefficient is defined to quantify the change in pressure-bearing capacity.It is found that the pressure-bearing capacity of the hydroformed expansion joint decreases,with the strength weakening coefficient primarily influenced by the wall thinning rate at the peak.Finally,a correlation between the strength weakening coefficient and the wall thinning rate at the peak is fitted. The research findings provide an important reference for the design and strength safety assessment of U-shaped expansion joints.更多还原