热预应力自增强厚壁圆筒研究

Study on Autofrettaged Thick-walled Cylinders with Thermal Pre-stresses

厚壁圆筒自增强处理技术的关键在于预应力。传统的自增强处理技术采用的是机械预应力方法,即在圆筒投入使用前,对其施加超过操作压力的自增强压力,使之获得残余预应力。考虑到厚壁圆筒内、外壁存在温差时,筒壁中有热应力产生,因此针对厚壁圆筒自增强问题,提出了以热应力作为预应力的自增强技术。具体研究了圆筒壁厚、温差等对热应力与总应力(热应力与操作应力的叠加)的影响、热应力与总应力的变化趋势、各种参数间的约束条件;在分析热应力与总应力特性的基础上,得出最佳设计条件,提出了基于第四强度理论的热预应力自增强厚壁圆筒的设计方法。结果表明,热预应力能有效地降低和均化厚壁圆筒的操作应力;按照所提出的设计方法,在确保圆筒安全的前提下,可使圆筒获得最大的承载能力和最小的壁厚。

The key to autofrettage technology of thick-walled cylinders lies in pre-stresses. In traditional autofrettage technology, pre-stresses in cylinders are produced by mechanical actions, that is, the cylinders are subjected to pressures higher than operation pressures for pre-stresses to be produced before they are put into use. In consideration of that there are thermal stresses in the wall of a cylinder when there is temperature difference between the inside and outside surfaces, for autofrettage of thick-walled cylinder, the technology of autofrettage with thermal pre-stresses is thus proposed. The effects of thickness and temperature difference on thermal stresses and total stresses （thermal stresses plus operation stresses） are studied. The varying trends of thermal stresses and total stresses are analyzed. The conditions of constraints on a variety parameters are investigated. On the basis of analyzing the characteristics of thermal stresses and the total stresses, the optimum design conditions are obtained, and a methodology for design of autofrettaged thick-walled cylinders with thermal pre-stresses based on the fourth strength theory is presented. It is shown that the thermal pre-stresses can effectively reduce and even the operation stresses of a thick-walled cylinder, and according to the presented methodology for design, the maximum load-bearing capacities and the minimum thicknesses of cylinders can be obtained under the prerequisite for ensuring safety of cylinders.