厚壁圆筒半椭圆表面浅裂纹的应力强度因子

STRESS-INTENSITY FACTORS FOR SHALLOW SURFACE CRACKS INSIDE A THICK-WALLED CYLINDER

本文用边界元法计算了受内压厚壁圆筒(R_0/R_i=125/60)内壁轴向表面浅裂纹的应力强度因子K_l。裂纹形状为半椭圆,其短长半径比分别为a/c=0.35及0.15,每种裂纹分别考虑了深厚比(a/t)为0.05、0.15、0.25及0.35等四种情况。为反映位移场和应力场的特性,在裂纹前缘内外分别配置了相应的奇性单元,并利用裂纹面上奇性元的节点位移计算前缘各点处的应力强度因子K_l(θ),文中对形状相同但深度不同及同一深度的不同形状裂纹的解以及表面裂纹与贯穿裂纹的解作了比较,还考察了奇性元的数目及计算模型的长度对K_l的影响。最后,用类似的方案计算了“基准问题”,结果令人满意。

This paper presents the stress-intensity factors K_1 for axial shallow cracks on the inside of a pressurized thick-walled (R0/R_i=125/60) cylinder. The cracks are of semi-elliptical shape, having depth to crack length (a/c) ratios 0.35 and 0.15 respectively. The ratio of crack depth to wall thickness (a/t) ranges from 0.05 to 0.35. stress-intensity factors are calculated by the boundary-element method. The boundary-element models employ 8-node quarter point singular elements along the crack front and 8-node isoparameter elements elsewhere. The stress-intensity factors are evaluated from nodal point displacements at the crack surface. Effects of the shape and depth of cracks and that of the cylinder length on the stress-intensity factors are investigated. To estimate the accuracy of the solutions, benchmark problem involving similar mesh schemes are calculated, with fairly satisfactory results.