Flaw In Cylinder Research Articles

Study on Sufficiency of Reference Stress Solutions for Crack-Like Flaws for Fitness-for-Service Evaluation

High Pressure Institute of Japan (HPI) has instituted the industrial standard HPIS Z101-2, “Assessment Procedure for Crack-Like Flaws in Pressure Equipment ‒ Level 2,” which addresses the methodology for the evaluation of fitness-for-service for detected flaws in industrial structural components such as pressure vessels, pipes, storage tanks, etc. during in-service inspection. In the standard, reference stress solutions for fundamental structures with surface flaws are prepared for the assessment of the acceptability of the detected flaws. From the viewpoint of the comprehensiveness of available solutions for excessive conditions, additional reference stress solutions for long surface flaw in plate, axially through-wall flaw in cylinder, circumferentially through-wall flaw in cylinder, and through-wall flaw in sphere were required. In this paper, the appropriate reference stress solutions to be adopted for the above structures were investigated by comparing the existing solutions in referable codes/standards.

Analysis of Elastic Surface Cracks in Cylinders Using the Line-Spring Model and Shell Finite Element Method

This paper presents elastic analysis of axial and circumferential semielliptical surface flaws in cylinders using the line-spring model of Rice and Levy [1-3] and a shell finite element method. Results for the stress intensity factor are obtained at various points along the crack front, and are compared in some cases against published literature solutions. A broad range of values for the cylinder radius-to-wall thickness ratio, flaw depth and aspect ratio are considered including surface flaws with very large aspect ratios. The critical values of aspect ratio at which the surface flaws can be treated as 2-dimensional cracks are determined. Effect flaw location (internal or external) and flaw shape (semielliptical, circular or rectangular) are also investigated. Finally, the significance of these results in the elastic-plastic fracture analysis procedures is discussed.

Stress Intensity Factor Solutions for Internal Longitudinal Semi-Circular Surface Flaws in a Cylinder Under Arbitrary Loading

The behavior of semi-circular surface flaws in cylinders is of interest in the technology of pressure vessels. The object of this study is to determine the stress intensity factor distribution around the crack front under arbitrary loading conditions for a longitudinal semi-circular flaw with Ri/t = 10; where Ri is the inside radius of the cylinder, and t is the cylinder thickness. Six crack depths are studied under various loading conditions: a/t = 0.10, 0.25, 0.50, 0.65, 0.80, and 0.90, where a is the circular flaw radius. In general, the finite element method is used to determine the displacement solution. Parks’ stiffness derivative method is used to find the stress intensity factor distribution around the semi-circle. The immediate crack tip geometry is modeled by use of a “macro-element” containing over 1600 degrees of freedom. Four separate loadings are considered: 1) constant, 2) linear, 3) quadratic, and 4) cubic crack surface pressure. From these loadings, nondimensional magnification factors are derived to represent the resulting stress intensity factors. Comparisons are made with other investigators and results agree within 5 percent of published results.

Analysis of surface cracks in plates and shells using the line-spring model and ADINA

The line-spring model of Rice and Levy is used in conjunction with thin shell finite elements to analyze surface cracks in plates and cylindrical shells. Implementation of the approach in the finite element code ADINA is discussed in detail. Both linear and nonlinear cases are considered. The stress intensity factor and the J-integral results are obtained for several example problems concerning surface cracked plates and axial and circumferential flaws in cylinders. Comparisons are made with the available literature solutions. Sensitivity of the results relative to the mesh size, integration scheme and other relevant parameters is also investigated.