Stress Intensity Factors of Pipe-In-Pipes With Circumferential Through-Wall Cracks Based on Elastic Finite Element Analyses

2017 ◽  
Author(s):  
Se-Chang Kim ◽  
Jae-Boong Choi ◽  
Nam-Su Huh
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Bending Moment ◽  
Economic Damage ◽  
Intensity Factors ◽  
Cross Sectional ◽  
3 Dimensional ◽  
Crack Location ◽  
Axial Tension

Any defects and cracks in pipe-in-pipes (PIPs) applied to deep-water and harsh environment are potential threats that can cause terrible economic damage or environmental pollution as triggering failures. In the present study, stress intensity factors (SIFs) of PIPs with circumferential through-wall cracks (TWCs) were investigated via detailed 3-dimensional (3-D) elastic finite element (FE) analyses. In terms of the crack location, the cracks are postulated in the inner pipe which is considered as mainly important part to assess the integrity of PIPs. In the present FE analyses, the effects of cross-sectional shapes of both inner and outer pipes on the SIFs of PIPs were systematically evaluated. As for loading conditions, internal pressure, axial tension and bending moment were considered. The FE results of the SIFs of PIPs were also compared with the existing solution of single-walled pipes with circumferential TWCs to evaluate the restraint effect by the outer pipe on the SIFs of PIPs, where the dimensions of single-walled pipes are assumed to be identical to those of the inner pipe of PIPs.

Finite Element Model Development for Structural Integrity of Shafts with Circumferential and Arbitrary Oriented Cracks

2015 ◽  
Vol 813-814 ◽  
pp. 905-909 ◽  
Author(s):  
R. Pramod ◽  
M.E. Shashi Kumar ◽  
S. Mohan Kumar
Keyword(s):  
Finite Element ◽  
Cylindrical Shell ◽  
Stress Intensity ◽  
Finite Element Model ◽  
Stress Intensity Factors ◽  
Structural Integrity ◽  
Accurate Determination ◽  
Bending Moment ◽  
Element Model ◽  
Intensity Factors

Tubular drive shafts are subjected to combined axial tension, torsional moment and bending moment. The structural integrity of the driveshaft is investigated by evaluating the change in strength, stiffness and the life of the driveshaft with the change in the crack length. A review of driveshaft failure analysis case histories identifies circumferential crack and arbitrarily oriented cracks to be critical. The singular stress field around a crack tip in a general shell structure is characterized by mixed mode membrane and bending stress intensity factors. Accurate determination of these stress intensity factors (less than 1%) are carried out by a subprogram named as 3MBSIF. The validation of Finite element model using ABAQUS and post processing subprogram 3MBSIF together is carried out using benchmarks, a set of standard test problems with known target solutions. Further SIFs are derived for cylindrical shell and the driveshaft under the action of bending moment. To quantify the change in the compliance of cylindrical shell and the driveshaft with change in crack lengths is studied by performing Modal Analysis. It was observed that the variation in frequency is higher for smaller crack angles.

A Coupled SBFEM-FEM Approach for Evaluating Stress Intensity Factors

2013 ◽  
Vol 353-356 ◽  
pp. 3369-3377 ◽  
Author(s):  
Ming Guang Shi ◽  
Chong Ming Song ◽  
Hong Zhong ◽  
Yan Jie Xu ◽  
Chu Han Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Complex Geometry ◽  
Stress Singularity ◽  
Intensity Factors ◽  
Finite Element Software ◽  
Scaled Boundary Finite Element ◽  
Element Method

A coupled method between the Scaled Boundary Finite Element Method (SBFEM) and Finite Element Method (FEM) for evaluating the Stress Intensity Factors (SIFs) is presented and achieved on the platform of the commercial finite element software ABAQUS by using Python as the programming language. Automatic transformation of the finite elements around a singular point to a scaled boundary finite element subdomain is realized. This method combines the high accuracy of the SBFEM in computing the SIFs with the ability to handle material nonlinearity as well as powerful mesh generation and post processing ability of commercial FEM software. The validity and accuracy of the method is verified by analysis of several benchmark problems. The coupled algorithm shows a good converging performance, and with minimum additional treatment can be able to handle more problems that cannot be solved by either SBFEM or FEM itself. For fracture problems, it proposes an efficient way to represent stress singularity for problems with complex geometry, loading condition or certain nonlinearity.

A Method for Assessing the “Local” Accuracy of Weight Functions for Plates With Embedded Cracks

1995 ◽  
Author(s):  
S. W. Ng ◽  
K. J. Lau
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Weight Functions ◽  
Finite Element Analyses ◽  
Intensity Factors ◽  
Local Accuracy ◽  
New Algorithms

Abstract In this paper a procedure is developed to assess the “local” accuracy of weight functions for finding stress intensity factors of centrally cracked finite plates given by Tsai and Ma (1989). It is found that the weight functions can be used to calculate stress intensity factors for practical cases, with “local” accuracy being within 6 %. In addition, weight functions generated from two finite element analyses are found to be accurate and may be used to assess new algorithms for finding weight functions.

Analysis of Surface Flaw in Pressure Vessels by a New 3-Dimensional Alternating Method

1982 ◽  
Vol 104 (4) ◽  
pp. 299-307 ◽  
Author(s):  
T. Nishioka ◽  
S. N. Atluri
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Crack Surface ◽  
Pressure Vessels ◽  
Pressure Loading ◽  
Intensity Factors ◽  
Alternating Method ◽  
Magnification Factors

An alternating method, in conjunction with the finite element method and a newly developed analytical solution for an elliptical crack in an infinite solid, is used to determine stress intensity factors for semi-elliptical surface flaws in cylindrical pressure vessels. The present finite element alternating method leads to a very inexpensive procedure for routine evaluation of accurate stress intensity factors for flawed pressure vessels. The problems considered in the present paper are: (i) an outer semi-elliptical surface crack in a thick cylinder, and (ii) inner semi-elliptical surface cracks in a thin cylinder which were recommended for analysis by the ASME Boiler and Pressure Vessel Code (Section III, App. G, 1977). For each crack geometry of an inner surface crack, seven independent loadings, such as internal pressure loading on the cylinder surface and polynomial pressure loadings from constant to fifth order on the crack surface, are considered. From the analyses of these loadings, the magnification factors for the internal pressure loading and the polynomial influence functions for the polynomial crack surface loadings are determined. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived by using the polynomial influence functions to check the internal consistency of the present analysis. These values agree excellently with the magnification factors obtained directly. The present results are also compared with the results available in literature.

scholarly journals CRACK RESISTANCE OF BABBIT B83

2017 ◽  
Vol 2017 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Михаил Зернин ◽  
Mikhail Zernin
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Resistance ◽  
Stress Intensity Factors ◽  
Cyclic Crack Resistance ◽  
Intensity Factors ◽  
Finite Element Procedure ◽  
Crack Resistance Test ◽  
Definition Of ◽  
Fracture Viscosity

Babbit 83 crack resistance test in accordance with SSR 25-506-85 was carried out. By finite element method there were defined values of stress intensity factors in flat samples with a grown crack. The fracture viscosity characteristics of babbit are obtained. On the basis of a macro-fractographic analysis of wear fractures of a babbit sample and a finite element procedure for the definition of values of stress intensity factors the cha-racteristics of cyclic crack resistance are obtained. It is shown that a final fracture is realized at 3 МПа , and a transition from an elastic stage to the stage elastoplastic development of a crack is realized at 2,0…2,8 МПа .

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