Abstract: The hoop stress field in a thick-walled cylinder of chemical vessels with internal surface single or multiple cracks have been determined by means of 3-D photo elasticity analysis.The "Load Relief" mechanism of internal surface multiple cracks are studied.As a result,the concept of "Non-Dimensional Additional Bending Moment"(m)and expressions have been found.The regular variation of the m with cracks position(θ),depth ration(T)and shape ratio (S) are given.The relationship between the m and "Load Relief Factor" (LRF) is explained.based on author's former works,the LRF of semi-elliptical multiple cracks which are radial symmmetric array in an internal pressurized thick-walled cylinder is established,then an expression and regular variation of Stress Intensity Factor (SIF) from the LRF are obtained.

Key words: thick-walled cylinder, crack, load relief, stress intensity factor

摘要： 通过三维光弹性实验测量了具有内表面单裂缝与受内压厚壁圆简型化工容器内的环向应力场,研究了内表面多裂缝的“载荷松弛”机理,建立了“无因次附加弯矩”(M)的概念及其计算式,给出了M随裂缝位置、裂缝深度比以及裂缝形状比的变化规律,说明了M与“载荷松弛因子”(LRF)的关系.建立了受内压厚壁圆筒内表面环向对称分布纵向半椭圆形多裂缝的LRF,以及由LRF得到的应力强度因子的近似计算式.

关键词: 厚壁圆筒, 裂缝, 载荷松弛, 应力强度因子