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首页> 外文会议>ASME(American Society of Mechanical Engineers) Pressure Vessels and Piping Conference: High-Pressure Technology 2003: Shaping High Pressure Technology for the Future; 20030720-20030724; Cleveland,OH; US >THE FAVORABLE EFFECT OF AUTOFRETTAGE ON UNIFORM ARRAYS OF 3-D UNEQUAL-DEPTH CRACKS IN A THICK-WALLED CYLINDRICAL PRESSURE VESSEL
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THE FAVORABLE EFFECT OF AUTOFRETTAGE ON UNIFORM ARRAYS OF 3-D UNEQUAL-DEPTH CRACKS IN A THICK-WALLED CYLINDRICAL PRESSURE VESSEL

机译：自动敲击对厚壁圆柱压力容器中3D不等深度裂纹均匀阵列的有利影响

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摘要

The favorable effect of autofrettage on the mode I stress intensity factor (SIF) distributions along the fronts of radial, semi-elliptical surface cracks pertaining to large uniform arrays of unequal-depth cracks emanating at the bore of a pressurized thick-walled cylinder is studied. The analysis is based on the, previously proposed, "two-crack-depth level model". SIF values are evaluated by the finite element method (FE) using the ANSYS 6.1 code. In the FE model singular elements are employed along the crack front and an equivalent temperature load simulates the autofrettage residual stress field. The distribution of K_(IN)=K_(IP) +K_(IA), the combined stress intensity factor due to pressurization and full autofrettage, for numerous uneven array configurations bearing n=n_1+n_2= 8 to 128 cracks, a wide range of crack depth to wall thickness ratios, a_1/t=0.01 to 0.4, and various crack ellipticities, a_1/C_1=0.3 to 1.5, are evaluated for a cylinder of radii ratio R_o/R_i=2. The accuracy of the evaluated SIFs is increased using an improved displacement extrapolation. The results clearly indicate the favorable effect of the residual stress field on the fracture endurance and the fatigue life of autofrettaged cylindrical pressure vessel bearing uniform arrays of 3-D unequal-depth cracks emanating from its inner bore. This favorable effect is governed by ψ=σ _o/P - the ratio of the vessel's material yield stress to its internal pressure. The higher ψ is the more effective autofrettage becomes. The "interaction range" for the various configurations of uneven crack arrays is evaluated. The range of influence between adjacent cracks on the maximal combined SIF, K_(Nmax), is found to be dependent on the density of the array, as reflected in the inter-crack aspect-ratio, as well as on the cracks' ellipticity.
机译：研究了自增强对沿径向，半椭圆形表面裂纹前沿的模式I应力强度因子（SIF）分布的有利影响，该径向裂纹涉及在加压厚壁圆柱孔处产生的均匀大的不等深度裂纹的均匀排列。该分析基于先前提出的“两裂纹深度级别模型”。使用ANSYS 6.1代码通过有限元方法（FE）评估SIF值。在有限元模型中，沿裂纹前沿采用了奇异元素，等效温度载荷模拟了自增强残余应力场。 K_（IN）= K_（IP）+ K_（IA）的分布，是由于加压和完全自动强化导致的组合应力强度因子，适用于许多n = n_1 + n_2 = 8至128个裂纹的不均匀阵列结构，范围很广对于半径比R_o / R_i = 2的圆柱体，评估了裂纹深度与壁厚之比a_1 / t = 0.01至0.4，以及各种裂纹椭圆率a_1 / C_1 = 0.3至1.5。使用改进的位移外推法可以提高评估的SIF的准确性。结果清楚地表明，残余应力场对承受自内孔3D不等深裂纹的均匀排列的圆筒形压力容器的抗疲劳能力和疲劳寿命具有有利的影响。这种有利的影响取决于ψ=σ_o / P-容器的材料屈服应力与其内部压力的比值。 ψ越高，自增强效果越有效。评估了不均匀裂纹阵列的各种构造的“相互作用范围”。发现相邻裂纹之间对最大组合SIF K_（Nmax）的影响范围取决于裂纹间纵横比所反映的阵列密度以及裂纹的椭圆率。

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