Elastic-Plastic J and COD Estimates for Circumferential Through-Wall Cracks Between Elbows and Straight Pipes Under Bending

2007 ◽  
Author(s):  
Tae-Kwang Song ◽  
Yun-Jae Kim
Keyword(s):  
Crack Opening ◽  
Small Strain ◽  
Opening Displacement ◽  
Limit Loads ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Plastic Materials ◽  
Elastic Perfectly Plastic ◽  
Reference Stress Approach

A method for elastic-plastic fracture mechanics analyses is presented for the circumferential through-wall crack in weldment joining elbows and attached straight pipes, subject to in-plane bending, based on the reference stress approach. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, closed-form limit loads for circumferential through-wall cracks in between elbows and straight pipes under bending are given. Then applicability of the reference stress based method to approximately estimate J and crack opening displacement (COD) is proposed.

Net-Section Limit Pressure and Engineering J Estimates for Axial Part-Through Surface Cracked Pipes

2007 ◽  
Author(s):  
Yun-Jae Kim ◽  
Chang-Sik Oh ◽  
Tae-Kwang Song
Keyword(s):  
Estimation Method ◽  
Small Strain ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Plastic Materials ◽  
Axial Part ◽  
Elastic Perfectly Plastic ◽  
Axial Surface ◽  
Good Agreement ◽  
J Estimation

This paper provides net-section limit pressures and a reference stress based J estimation method for pipes with internal axial surface cracks under internal pressure. Based on systematic small strain FE limit analyses using elastic-perfectly plastic materials, closed-form approximations of net-section limit pressures are presented. Then, based on proposed net-section limit moments, a method to estimate elastic-plastic J is proposed based on the reference stress approach. Comparison with extensive FE results shows overall good agreement.

Effects of the Bend Angle and the Length of the Attached Straight Pipe on Plastic Loads for Pipe Bends

2007 ◽  
Author(s):  
Chang-Sik Oh ◽  
Yun-Jae Kim
Keyword(s):  
Limit Load ◽  
Small Strain ◽  
Bend Angle ◽  
Plastic Limit ◽  
Straight Pipe ◽  
Pipe Bend ◽  
Limit Loads ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Elastic Perfectly Plastic

This paper quantifies effects of the bend angle and the length of the attached straight pipe on plastic limit loads of the 90° pipe bend, based on small strain FE limit analyses using elastic-perfectly plastic materials with the small geometry change option. It is found that the effect of the length of the attached straight pipe on plastic limit loads can be significant, and the limit loads tend to decrease with decrease of the length of the attached straight pipe. Regarding the effect of the bend angle, it is found the plastic load smoothly changes from the limit load of the straight pipe when the bend angle approaches zero to the plastic load of the 90° pipe bend when the bend angle approaches 90 degree.

Effects of Torsion on Equivalent Bending Moment for Limit Load and EPFM Circumferential Pipe Flaw Evaluations

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Weighted Factor ◽  
Elastic Perfectly Plastic

The circumferential flaw evaluation procedures in ASME Boiler and Pressure Vessel Code Section XI nonmandatory Appendix C are currently limited to straight pipes under pressure and bending loads without consideration of torsion loading. The Working Group on Pipe Flaw Evaluation of the ASME Boiler and Pressure Vessel Code is developing guidance for considering the effects of torsion by a mean of an equivalent bending moment, which is a square root of sum square combination of bending moment and torsion load with a weighted factor for torsion moment. A torsion weighted factor, Ce, is established in this paper using large strain finite element limit load analysis with elastic perfectly plastic materials. Planar flaws and nonplanar flaws in a 10.75 in. (273 mm) OD pipe are investigated. Additionally, a finite element J-integral calculation is performed for a planar through wall circumferential flaw with elastic plastic materials subjected to bending and torsion load combinations. The proposed Ce factor for planar flaws is intended for use with the ASME B&PV Code Section XI, Appendix C for limit load and Elastic Plastic Fracture Mechanics (EPFM) circumferential planar flaw evaluations.

Plastic Limit Loads for Slanted Through-Wall Cracks in Cylinder and Plate Based on Finite Element Limit Analyses

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Doo-Ho Cho ◽  
Young-Hwan Choi ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Jae-Boong Choi
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Limit Load ◽  
Correction Factors ◽  
Plastic Limit ◽  
Opening Displacement ◽  
Limit Loads ◽  
Axial Tension ◽  
Reference Stress ◽  
Plastic Limit Load

The plastic limit load solutions for cylinder and plate with slanted through-wall cracks (TWCs) are developed based on the systematic three-dimensional (3D) finite element (FE) limit analyses. As for loading conditions, axial tension, global bending, and internal pressure are considered for a cylinder with slanted circumferential TWC, whereas, axial tension and internal pressure are considered for a plate and a cylinder with slanted axial TWC. Then, the verification of FE model and analysis procedure employed in the present numerical work was confirmed by employing the existing solutions for both cylinder and plate with idealized TWC. Also, the geometric variables of slanted TWC which can affect plastic limit loads were considered. Based on the systematic FE limit analysis results, the slant correction factors which represent the effect of slanted TWC on plastic limit load were provided as tabulated solutions. By adopting these slant correction factors, the plastic limit loads of slanted TWC can be directly estimated from existing solutions for idealized TWC. Furthermore, the modified engineering estimations of plastic limit loads for slanted TWC are proposed based on equilibrium equation and von Mises yield criterion. The present results can be applied either to diverse structural integrity assessments or for accurate estimation of fracture mechanics parameters such as J-integral, plastic crack opening displacement (COD) and C*-integral for slanted TWC based on the reference stress concept (Kim, et al., 2002, “Plastic Limit Pressure for Cracked Pipes Using Finite Element Limit Analyse,” Int. J. Pressure Vessels Piping, 79, pp. 321–330; Kim, et al., 2001, “Enhanced Reference Stress-Based J and Crack Opening Displacement Estimation Method for Leak-Before-Break Analysis and Comparison With GE/EPRI Method,” Fatigue Fract. Eng. Mater. Struct., 24, pp. 243–254; Kim, et al., 2002, “Non-Linear Fracture Mechanics Analyses of Part Circumferential Surface Cracked Pipes,” Int. J. Fract., 116, pp. 347–375.)

Reference Stress Solutions for Idealized Branch Junctions

2007 ◽  
Author(s):  
Yun-Jae Kim ◽  
Kuk-Hee Lee
Keyword(s):  
Three Dimensional ◽  
Limit Load ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Plastic Materials ◽  
Pipe Radius ◽  
Plastic Limit Load ◽  
The Mean ◽  
Elastic Perfectly Plastic ◽  
Good Agreement

The present work presents plastic limit load solutions for thin-walled branch junctions under internal pressure and in-plane bending, based on detailed three-dimensional (3-D) FE limit analyses using elastic-perfectly plastic materials. The proposed solutions are valid to ratios of the branch-to-run pipe radius and thickness from 0.0 to 1.0, and the mean radius-to-thickness ratio of the run pipe from 5.0 to 20.0. Comparison with FE results shows good agreement.

Limit loads for thin‐walled piping branch junctions under combined pressure and in‐plane bending

2008 ◽  
Vol 43 (2) ◽  
pp. 87-108 ◽  
Author(s):  
Y‐J Kim ◽  
K‐H Lee ◽  
C‐Y Park
Keyword(s):  
Branch Pipe ◽  
Three Dimensional ◽  
Limit Load ◽  
Small Strain ◽  
Limit Loads ◽  
Perfectly Plastic ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

Closed‐form yield loci are proposed for branch junctions under combined pressure and in‐plane bending, via small‐strain three‐dimensional finite element (FE) limit load analyses using elastic—perfectly plastic materials. Two types of bending loading are considered: bending on the branch pipe and that on the run pipe. For bending on the run pipe, the effect of the bending direction is further considered. Comparison with extensive FE results shows that predicted limit loads using the proposed solutions are overall conservative and close to FE results. The proposed solutions are believed to be valid for the branch‐to‐run pipe ratios of radius and of thickness from 0.0 to 1.0, and the mean radius‐to‐thickness ratio of the run pipe from 5.0 to 20.0.

Limit Loads for Circumferential Cracked Pipe Bends under In-Plane Bending

2006 ◽  
Vol 321-323 ◽  
pp. 38-42
Author(s):  
Yun Jae Kim ◽  
Chang Sik Oh ◽  
Bo Kyu Park ◽  
Young Il Kim
Keyword(s):  
Three Dimensional ◽  
Surface Cracks ◽  
Plastic Limit ◽  
Limit Loads ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

This paper presents limit loads for circumferential cracked pipe bends under in-plane bending, based on detailed three-dimensional finite element limit analyses. FE analyses are performed based on elastic-perfectly-plastic materials and the geometrically linear assumption. Both through-wall cracks and part-through surface cracks (having constant depths) are considered, together with different crack locations (extrados and intrados). Based on the FE results, closed-form approximations are proposed for plastic limit loads of pipe bends. It is found that limit loads of pipe bends are smaller than those of straight pipes, but are close for deep and long cracks.

Mismatch Limit Loads of Circumferential Cracked Pipes With V-Groove Welds

2013 ◽  
Author(s):  
Sang-Hyun Kim ◽  
Jae-Jun Han ◽  
Yun-Jae Kim
Keyword(s):  
Crack Depth ◽  
Butt Weld ◽  
Limit Loads ◽  
Closed Form Solutions ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Angle Crack ◽  
Elastic Perfectly Plastic ◽  
Welded Pipe ◽  
Deformation Patterns

The present work reports mis-match limit loads for V-groove welded pipe for a circumferential crack using finite element (FE) analyses. In our previous paper [14], closed-form solutions of mis-match limit loads were proposed for idealized butt weld configuration as a function of the strength mis-match ratio with only one geometry-related slenderness parameter. To integrate the effect of groove angles on mis-match limit loads, the geometry-related slenderness parameter has to be modified by relevant geometric parameters including groove angle, crack depth and root opening based on plastic deformation patterns in theory of plasticity. Circumferential through-wall cracks are located at the centre of the weld considering two different groove angles (45°, 90°). With regards to loading conditions, axial (longitudinal) tension is applied for all cases. For the parent and weld metal, elastic-perfectly plastic materials are used to simulate under-matching and over-matching conditions in plasticity. The overall results from the proposed solutions agree well with FE results.

Effect of Local Wall Thinning on Maximum Load Carrying Capacities of Elbows under Bending

2007 ◽  
Vol 345-346 ◽  
pp. 517-520
Author(s):  
Jong Hyun Kim ◽  
Joong Hyuk Ahn ◽  
Seok Pyo Hong ◽  
Yun Jae Kim ◽  
Chi Yong Park
Keyword(s):  
Three Dimensional ◽  
Limit Load ◽  
Maximum Load ◽  
Small Strain ◽  
Perfectly Plastic ◽  
Wall Thinning ◽  
Plastic Materials ◽  
Load Carrying ◽  
Elastic Perfectly Plastic ◽  
Local Wall Thinning

This paper provides closed-form plastic limit load solutions for elbows with local wall thinning under in-plane bending, via three-dimensional (3-D), small strain FE limit analyses using elastic-perfectly plastic materials. Wide ranges of elbow and thinning geometries are considered.

Elastic-Plastic State of Inhomogeneous Soil Array with a Spherical Cavity

2013 ◽  
Vol 842 ◽  
pp. 462-465 ◽  
Author(s):  
Vladimir I. Andreev ◽  
Anatoliy S. Avershyev ◽  
Stanislaw Jemiolo
Keyword(s):  
Plastic Deformation ◽  
Outer Surface ◽  
Spherical Cavity ◽  
Plastic Material ◽  
Plastic State ◽  
Cavity Model ◽  
Limit Loads ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The article deals with the elastic-plastic state of inhomogeneous array with a spherical cavity. Model is used thick-walled ball of an elastic-perfectly plastic material (Prandtl diagram). It is shown that in the inhomogeneous material, depending on the inhomogeneity functions describing the change of the modulus of elasticity and yield stress of soil plastic deformation may appear on both the inner and outer surface of the ball and inside it. Are found values of the limit loads, displacement diagrams are constructed in an array.

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