机械自紧厚壁圆筒塑性半径的计算

Calculation of Plastic Radius for Thick-Walled Cylinders of Mechanical Autofrettage

机械自紧是依靠冲头同身管内径的过盈量使身管内壁产生塑性变形,提高承载能力,达到自紧的目的.准确建立冲头过盈量与塑性半径之间的关系,才能准确地预测自紧度.为此,利用合理的简化假设,通过对冲头进行弹性分析和对厚壁圆筒进行塑性分析,利用机械自紧在加载过程中冲头圆柱段和厚壁圆筒接触处径向应力相等这一边界条件,推导出了过盈量与塑性半径之间的计算公式,从该公式可直接由过盈量求出塑性半径,由塑性半径便可预测出机械自紧厚壁圆筒的自紧度.为了验证公式的正确性,对10种不同过盈量的机械自紧过程进行了数值模拟,理论计算与数值模拟的结果进行比较,发现理论计算结果与数值模拟的结果比较吻合.

The swage autofrettage barrel is formed depending on the depth of plastic deformation since the diameter of the tool is slightly larger than the barrel inner diameter. The barrel forged in this way can withstand large internal pressures. In order to calculate the degree of autofrettage, the relation between the interference and the plastic radius must be accurately investigated. In loading process, the radial stress of cylindrical section of swage and thick-walled cylinder contact section is equal. By using this boundary condition, an elastic analysis for swage and a plastic analysis for thick-walled cylinder were conducted, and formulas were obtained for calculating excess and plastic radius. Knowing interference, the plastic radius could be calculated directly and the tight tolerance could be pre-estimated by using the plastic radius. To verify the accuracy of the formula, the process of mechanical autofrettage with ten kind different interferences were simulated. Calculated plastic radius agreed well with the results of numerical simulation.