Stress Intensity Factor of Semielliptical Surface Crack in Internally Pressurized Hollow Cylinder-A Comparison between BS 7910 and API 579/ASME FFS-1 Solutions.

Gabriel Coêlho,Marco Santos,Neilor Santos,Antonio Silva,Antonio Lima

doi:10.3390/ma12071042

Abstract

The purpose of this research is to compare both British standard BS 7910 (2013) and American standard API 579/ASME FFS-1 (2016) stress intensity factor (SIF) solutions by considering a series of semielliptical surface cracks located in the external surface of a pressurized hollow cylinder in the axial direction. Finite element analysis was used as a comparison basis for both standards’ SIF results. The solution from the British standard provided consistent results compared to Finite Element (FE) results for crack depth not much higher than half the thickness in the deepest and surface-breaking points. Above those limits, the British standard’s solutions diverged quite a lot from the American standard, whose results followed FE values for every crack depth/thickness ratio tested with a maximum percentage difference of 1.83%.

Highlights

Stress intensity factor (SIF), first introduced by Irwin [1], is a physical quantity used as a control parameter to evaluate the critical state of a crack [2]
The comparison between mode I SIF solutions provided by worldwide standards, BS
I SIFconsidering solutions provided by worldwide standards, 7910 [4]

Summary

Introduction

Stress intensity factor (SIF), first introduced by Irwin [1], is a physical quantity used as a control parameter to evaluate the critical state of a crack [2]. Assuming an isotropic material with linear elastic behavior, the stress field on any linear elastic body that holds a crack can be determined, according to. (m) σij = k/ r fij (θ) + ∑ Am rm/2 gij (θ), (1). M=0 where σij is the stress tensor; r and θ are the polar coordinates defined by the origin at the crack front, according to Figure 1; k is a constant; fij (θ) are dimensionless functions; Am and gij (θ) are higher-order terms for the amplitude and a dimensional function of θ for the m-th term, respectively. Replacing k by the SIF K such that K = k√2π and Materials 2019, 12, 1042 omitting the higher-order terms, it is possible to obtain the elastic stress field around the crack front.

Objectives

Methods

Results

Discussion

Conclusion