工程常用开孔补强方法的原理探讨及对比分析

Theoretical Discussion and Comparative Analysis on Opening Reinforcement Methods of Engineering

压力容器壳体开孔区应力性质和加载方式的不同对壳体强度破坏的形式不同,因此对强度校核需对应采用不同的开孔补强方法。本文基于工程实际,从理论原理和设计准则方面分别探讨了各种开孔补强方法的适用性、合理性及局限性,以期为工程设计人员提供一定的理论指导:等面积法和压力面积法均只考虑薄膜应力的一次静力强度问题,对小开孔补强计算具有一定的可靠性,对大开孔补强计算则均不适用或不可靠;有限元法在大开孔补强中对薄膜应力和薄膜+弯曲应力的评定均比分析法严格;ASME弯矩法对小开孔补强计算具有较高的可靠性,对大开孔补强计算因未考虑绕接管母线方向弯矩的作用而不可靠;有限元法则因无法区分一次和二次弯曲应力,导致对一次应力评定较为保守,而对二次应力评定则偏冒进。

Stress characteristics which produced on opening area and its loading methods lead to different damage to the strength of pressure vessel, therefore the analysis of strength should be corresponding to the different methods of opening reinforcement. This article respectively discussed the applicability, rationality and limitations of the opening reinforcement methods from the viewpoint of theoretical principle and design criterion, in order to provide certain theoretical guidance for engineering design. The equal-area and pressure-area method only considered the influence of membrane stress on primary static strength and with certain reliability on opening reinforcement for small opening, but inapplicable or unreliable for large opening. Both the reinforcement assessing criterion on membrane stress and membrane stress plus bending stress by finite element method for large opening are more strictly than analytical method. The ASME moment method has a high reliability on opening reinforcement for small opening, also unreliable for large opening without considering the surrounding moment of nozzle generatrix direction. However, the finite element method causes conservative assessment to primary stress and aggressively assessment to secondary stress, which cannot distinguish the primary and secondary bending stress.