A Study on Effect of Shape Irregularities on Collapse Loads of Pipe Bends with Critical Circumferential Throughwall Crack under In-Plane Closing Bending

2014 ◽  
Vol 592-594 ◽  
pp. 980-984
Author(s):  
Sumesh Sasidharan ◽  
Arunachalam R. Veerappan ◽  
Subramaniam Shanmugam
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Detrimental Effect ◽  
Bending Moment ◽  
Collapse Load ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Circumferential Crack ◽  
Plane Bending

The presence of thorough wall circumferential cracks has a detrimental effect on collapse load of elbows. The existing theoretical solutions do not correctly quantify the weakening effect due to the presence of the circumferential through wall crack in shape imperfect pipe bends. The present study has been done to investigate the effect of ovality and thinning on the collapse moment of 90° elbow with critical throughwall circumferential crack under in-plane bending moment using elastic-plastic finite element analysis considering large geometry change.

An Improved Joint Model and Equations for Flexibility of Tubular Joints

1990 ◽  
Vol 112 (2) ◽  
pp. 157-168 ◽  
Author(s):  
Y. Ueda ◽  
S. M. H. Rashed ◽  
K. Nakacho
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bending Moment ◽  
Joint Model ◽  
Initial Stiffness ◽  
Element Analysis ◽  
Joint Flexibility ◽  
Elastic Plastic ◽  
Tubular Joints ◽  
Different Types

In tubular frames with simple joints, joints may show considerable flexibility in the elastic as well as the elastic-plastic ranges. Such flexibility may have large effects on the behavior of the structure as a whole. In a previous paper, an effective simple model of tubular joints is developed. The model takes account of joint flexibility in the elastic as well as the elastic-plastic ranges based on elastic-fully plastic load-displacement relatioships. In this paper an improved joint model is presented to provide better accuracy while maintaining simplicity. The accuracy of the model is confirmed through comparisons with results of finite element analysis. Equations to evaluate the initial stiffness of tubular T and Y-joints when braces are subjected to axial compression or in-plane bending moment are also presented. Such equations for different types of joints in different loading conditions are needed in order to avoid expensive calculations to evaluate the initial stiffness of joints.

Analytical Determination of Stress Indices and Stress Intensification Factor for an Extruded Nozzle of Super Pipe

2018 ◽  
Author(s):  
Lv Feng ◽  
Zhou Gengyu ◽  
Qian Haiyang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Branch Pipe ◽  
Bending Moment ◽  
Analytical Determination ◽  
Element Analysis ◽  
Stress Indices ◽  
Asme Code ◽  
Stress Intensification Factor ◽  
Plane Bending

The super pipe nozzles in nuclear power plants are usually designed to be in compliance with the requirements of Class 2 piping of Section III of the ASME Boiler and Pressure Vessel Code. The stress indices B2 and stress intensification factor i are required for the stress evaluation. In the past two decades, the hot extrusion forming technology has been widely used to manufacture those nozzles, instead of traditional insert weldolets. However, previous extruded nozzle stress analyses have shown B2 that the calculated stresses may exceed the limits in some working conditions. The objective of present study is to determine the stress indices and stress intensification factor for an extruded nozzle of the supper pipe by the finite element method and to evaluate the conservatism of those factors from the ASME Code formulae. In this paper, a three-dimensional finite element model of an extruded nozzle is developed. Four load cases are considered, which are corresponding to an in-plane bending moment and an out-plane bending moment applied at the run pipe side and at the branch pipe side, respectively. The magnitude of bending moment is assumed to be 1000Nm. The stress indices B2r, B2b, C2r, C2b, K2r and K2b, where the subscript r and b refer to the run pipe and B2r the branch pipe, are calculated based on the finite element analysis results. The stress intensification factor ir and ib are determined by the empirical formula: ir = C2r*K2r/2 and ib = C2b*K2b/2. Further, the developed factors are compared with those calculated from the ASME code formulae. It is found that the stress indices B2r and B2b obtained from the linear elastic finite element analysis are conservative. Currently, the values of B2r and B2b gained from the ASME code formulae are more appropriate for the stress evolution. The stress intensification factors ir and ib obtained from the analytical determination are lower than those calculated from the ASME code formula. For the extrude nozzle studied, the factor ir decreases 30% and the factor ib decreases about 3.3%.

Finite Element Analysis Based Stress Intensification Factor Calculation and Comparison With Various Approaches for Stress Intensification Factor Calculation

2017 ◽  
Author(s):  
Mahesh Kulkarni ◽  
Vivek Dewangan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Branch Pipe ◽  
Bending Moment ◽  
Piping System ◽  
Element Analysis ◽  
Process Industries ◽  
Average Value ◽  
Stress Intensification Factor ◽  
Plane Bending

Piping caters a major role in the process industries wherein stress intensification factor (SIF) express the Piping flexibility of the system. A typical Piping system consists of combination of pipes and various fittings with intersection geometries namely bend, tee, reducer, etc. A SIF is a multiplier on nominal bending stress so that the effect of geometry and welding can be considered in a flexibility analysis. An attempt has been made to compare the SIF values among ASME Piping B31.3, Welded Research Council (WRC) Bulletin 329, Paulin Research Group (PRG) empirical data and shell-based finite element analysis (FEA) for various tee sections based on in-plane and out-plane bending moments through this paper. The bending moment which causes tee to open/close in the plane formed by two limbs of tee is called in-plane bending moment. The bending moment which causes branch of tee to displace out of the plane retaining run pipe steady is called Out-plane bending moment. ASME B31.3 provide guidelines to evaluate SIF values through empirical formulation as per Appendix-D with few limitations listed below. 1. Valid for d/D < 0.5 only 2. Non-conservative for 0.5 < d/D < 1.0 3. Valid for D/T ≤ 100 4. SIF values calculated with respect to header pipe. There is no difference in SIF values for header and branch pipe and it is the average value. WRC 329 was published in 1987 and has not been updated taking ASME B31.3 latest edition into account. PRG carried out SIF for the various sizes and types of tee fittings and prepared correlation equations through detailed FEA using nonlinear regression and test data.

Nonlinear Analysis of Pressurized Piping Elbows Subjected to Out-of-Plane Bending

2006 ◽  
Vol 306-308 ◽  
pp. 351-356 ◽  
Author(s):  
Asnawi Lubis ◽  
Jamiatul Akmal
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Cross Section ◽  
Bending Moment ◽  
Pressure Reduction ◽  
Element Analysis ◽  
Out Of Plane ◽  
Plane Bending ◽  
Reduction Effect

The behavior of piping elbows under bending and internal pressure is more complicated than expected. The main problem is that the coupling of bending and internal pressure is nonlinear; the resulting stress and displacement cannot be added according to the principle of superposition. In addition, internal pressure tends to act against the effect caused by the bending moment. If bending moment ovalise the elbow cross-section, with internal pressure acting against this deformation, then the ovalised cross section deform back to the original circular shape. It is then introduced the term “pressure reduction effect”, or in some literature, “pressure stiffening effect”. Current design piping code treats the pressure reduction effect equally for in-plane (closing and opening) moment and outof- plane moment. The aim of this paper is to present results of a detailed finite element analysis on the non-linear behavior of piping elbows of various geometric configurations subject to out-of-plane bending and internal pressure. Specifically the standard Rodabaugh & George nonlinear pressure reduction equations for in-plane closing moment are checked in a systematic study for out-of-plane moment against nonlinear finite element analysis. The results show that the pressure stiffening effects are markedly different for in-plane and out-of-plane bending.

Development of J-Integral Solutions for Semi-Elliptical Circumferential Cracked Pipes Subjected to Internal Pressure and Bending Moment

2015 ◽  
Author(s):  
Makoto Udagawa ◽  
Jinya Katsuyama ◽  
Yoshihito Yamaguchi ◽  
Yinsheng Li ◽  
Kunio Onizawa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Loading Condition ◽  
Bending Moment ◽  
J Integral ◽  
Surface Cracks ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Piping Systems ◽  
Integral Solutions

The J-integral solutions for cracked pipes are important in crack growth calculation and failure evaluation based on the elastic-plastic fracture mechanics. One of the most important crack types in structural integrity assessment for nuclear piping systems is circumferential semi-elliptical surface crack on the inside of the pipes. Although several J-integral solutions have been provided, no solutions were developed at both the deepest and the surface points of circumferential semi-elliptical surface cracks in pipes. In this study, with backgrounds described above, the J-integral solutions of circumferential semi-elliptical surface cracks on the inside of the pipe were developed by numerical finite element analyses. Three dimensional elastic-plastic analyses were performed considering different material properties, pipe sizes, crack dimensions and, especially, combined loading condition of internal pressure and bending moment which is a typical loading condition for nuclear piping systems. The J values at both the deepest and the surface points were extracted from finite element analysis results. Moreover, in order to benefit users in practical applications, a pair of convenient J-integral estimation equations were developed based on the calculated J values at the deepest and the surface points. Finally, the accuracy and applicability of the convenient equations were confirmed by comparing with the provided stress intensity factor solutions in elastic region and with finite element analysis results in elastic-plastic region.

Elastic-Plastic Analysis of an Elbow With Axial Part-Through Internal Crack at Crown Under In-Plane Bending

2008 ◽  
Author(s):  
K. M. Prabhakaran ◽  
S. R. Bhate ◽  
V. Bhasin ◽  
A. K. Ghosh
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Bending Moment ◽  
Internal Crack ◽  
J Integral ◽  
Finite Element Analyses ◽  
Integrity Assessment ◽  
Elastic Plastic ◽  
Axial Part ◽  
Plane Bending

Piping elbows under bending moment are vulnerable to cracking at crown. The structural integrity assessment requires evaluation of J-integral. The J-integral values for elbows with axial part-through internal crack at crown under in-plane bending moment are limited in open literature. This paper presents the J-integral results of a thick and thin, 90-degree, long radius elbow subjected to in-plane opening bending moment based on number of finite element analyses covering different crack configurations. The non-linear elastic-plastic finite element analyses were performed using WARP3D software. Both geometrical and material nonlinearity were considered in the study. The geometry considered were for Rm/t = 5, and 12 with ratio of crack depth to wall thickness, a/t = 0.15, 0.25, 0.5 and 0.75 and ratio of crack length to crack depth, 2c/a = 6, 8, 10 and 12.

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