Ratcheting Behavior of Pressurized Elbow Pipe under Different Loading Modes

2016 ◽  
Vol 853 ◽  
pp. 322-327 ◽  
Author(s):  
Wei Qiang Qu ◽  
Xu Chen
Keyword(s):  
Internal Pressure ◽  
Kinematic Hardening ◽  
Peak Load ◽  
Circumferential Direction ◽  
Hardening Model ◽  
Loading Paths ◽  
Plane Bending ◽  
Loading Modes ◽  
Dangerous Point

Ratcheting deformation is studied on elbow pipe made of Z2CND18.12N by FEM software. The simulation is conducted by ANSYS. Chen-Jiao-Kim (CJK) kinematic hardening model is added in ANSYS for the study. The elbow pipe is subjected to internal pressure and reversed in-plane bending. Internal pressure can be constant or cyclic. Many different loading paths are used in the study. Ratcheting deformations of under different ways are studied. The result shows that ratcheting deformation occurs mainly in the circumferential direction. Ratcheting deformation at the crown and intrados of elbow pipe is more notable because of higher stress. Tensile or compressed load can influence the position of dangerous point. It is found that ratcheting deformations under different paths with same peak load are different.

Ratcheting Behavior of Pressurized Elbow Pipe After Thermal Aging

2018 ◽  
Author(s):  
Caiming Liu ◽  
Dunji Yu ◽  
Xu Chen
Keyword(s):  
Internal Pressure ◽  
Thermal Aging ◽  
Aging Temperature ◽  
Kinematic Hardening ◽  
Hardening Model ◽  
Aging Period ◽  
Plane Bending

In the present work, the effect of thermal aging on ratcheting behaviors of three pressurized elbow pipes after different thermal aging periods was experimentally studied under constant internal pressure and reversed in-plane bending. The elbow pipes were thermal aged for 1000 h and 2000 h at the same aging temperature of 500 centigrade degrees. It is indicated that thermal aging period has a significant effect on elbow pipe’s ratcheting deformation. Chen-Jiao-Kim (CJK) kinematic hardening model was employed to evaluate the ratcheting behaviors of pressured elbow pipes affected by thermal aging.

Multilayer Kinematic Hardening Model for Carbon Steel and its Application to Inelastic Analyses of an Elbow Subjected to Cyclic In-Plane Bending

2015 ◽  
Author(s):  
Koji Iwata ◽  
Yasuhisa Karakida ◽  
Chuanrong Jin ◽  
Hitoshi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Carbon Steel ◽  
Kinematic Hardening ◽  
Isothermal Condition ◽  
Cyclic Hardening ◽  
Bending Test ◽  
Cyclic Plasticity ◽  
Repeated Loading ◽  
Stress Strain ◽  
Hardening Model ◽  
Plane Bending

Carbon steel STS410 (JIS Standard), which is widely used for high pressure piping components, exhibits cyclic hardening under repeated loading. Extreme seismic loading can cause repetitive large strains, eventually leading to the failure of components. For failure assessment of such components, inelastic analyses using cyclic plasticity constitutive models are needed. In this paper, a multilayer kinematic hardening model for cyclic plasticity, equipped with a set of standard stress-strain characteristics, is developed for STS410 under isothermal condition of various temperatures. This model can express not only the nonlinearity of stress-strain relations, but cyclic hardening of a material by introducing a generic stress-strain relation composed of a combination of monotonic and steady state cyclic stress-strain curves. Finite element large deformation elastic-plastic analyses with this model are conducted for a cyclic in-plane bending test of an elbow. The proposed constitutive model predicted well characteristic features of global deformation and local strain behaviors of the elbow.

Correlation of Test and FEA Studies on Effect of Bend Radius and Thickness on Ratcheting in Pipe Bends Subjected to Internal Pressure and In-Plane Bending Moment

2005 ◽  
Author(s):  
K. Shanmuga Sundaran ◽  
G. Thanigaiyarasu
Keyword(s):  
Internal Pressure ◽  
Analytical Study ◽  
Kinematic Hardening ◽  
Bending Moment ◽  
Material Model ◽  
Analysis Procedure ◽  
Strain Accumulation ◽  
Bend Radius ◽  
Plane Bending ◽  
Selection Of

The paper deals with the results from the analytical study on ratcheting in pipe bends. There has been no well-defined material model and analysis procedure to predict this phenomenon accurately. A recent development in parameter selection of Chaboche’s Kinematic hardening model has resulted in close predictions in ratcheting analysis [15]. A problem has been selected from existing experimental results [16, 17] published in literature, and an analysis incorporating these parameters has been carried out and presented. The amount of stresses induced and strain accumulated in pipe bends with long and short radius and subjected to internal pressure and in-plane bending moment is studied. The results and their inferences are included. The analysis was carried out on 2-inch NPS SS304 pipe bends with different bend radius and two thickness (Schedule 40 and Schedule 80) using ABAQUS, non-linear FEA software to predict the strain accumulation and their influences on ratcheting failure is presented.

Effect of Plastic Hardening Models on Fatigue Life Simulation of Pipeline Elbows Under Operating Pressure and Cyclic Bending

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fatigue Life ◽  
Numerical Study ◽  
Kinematic Hardening ◽  
Combined Loading ◽  
Operating Pressure ◽  
Element Analysis ◽  
Hardening Model ◽  
Hardening Models ◽  
Plastic Hardening ◽  
Plane Bending

Abstract This paper presents a numerical study of plastic hardening models used in the stress, strain, and fatigue life simulations of a pipeline elbow under operating pressure and cyclic in-plane bending. To determine more accurate stresses, strains, and fatigue life of the elbow in cyclic loading, the material plastic hardening response and the Bauschinger effect need to be considered properly in the numerical simulation. The isotropic, kinematic, and combined isotropic/kinematic hardening models are, thus, evaluated in the elastic-plastic finite element analysis (FEA) of a benchmark beam. On this basis, those plastic hardening models are applied to simulate the elbow under combined loading of constant internal pressure and cyclic in-plane bending. With the FEA results and selected fatigue models that are commonly used in the pipeline industry, fatigue life of the elbow is predicted for each hardening model. As such, the appropriate plastic hardening model and fatigue life model to predict fatigue life of the elbow are determined.

Effect of bend angle on plastic loads of pipe bends under internal pressure and in-plane bending

2007 ◽  
Vol 49 (12) ◽  
pp. 1413-1424 ◽  
Author(s):  
Yun-Jae Kim ◽  
Kuk-Hee Lee ◽  
Chang-Sik Oh ◽  
Bong Yoo ◽  
Chi-Yong Park
Keyword(s):  
Internal Pressure ◽  
Bend Angle ◽  
Plane Bending

Shakedown Limit Load Determination for a Kinematically Hardening 90-Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic Bending

2007 ◽  
Author(s):  
Hany F. Abdalla ◽  
Mohammad M. Megahed ◽  
Maher Y. A. Younan
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Plastic Material ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Material Behavior ◽  
Pipe Bend ◽  
Cyclic Bending ◽  
Perfectly Plastic ◽  
Shakedown Limit

A simplified technique for determining the shakedown limit load of a structure employing an elastic-perfectly-plastic material behavior was previously developed and successfully applied to a long radius 90-degree pipe bend. The pipe bend is subjected to constant internal pressure and cyclic bending. The cyclic bending includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending moment loadings. The simplified technique utilizes the finite element method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full cyclic loading finite element simulations or conventional iterative elastic techniques. In the present paper, the simplified technique is further modified to handle structures employing elastic-plastic material behavior following the kinematic hardening rule. The shakedown limit load is determined through the calculation of residual stresses developed within the pipe bend structure accounting for the back stresses, determined from the kinematic hardening shift tensor, responsible for the translation of the yield surface. The outcomes of the simplified technique showed very good correlation with the results of full elastic-plastic cyclic loading finite element simulations. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes. The generated shakedown diagrams are compared with the ones previously generated employing an elastic-perfectly-plastic material behavior. These indicated conservative shakedown limit moments compared to the ones employing the kinematic hardening rule.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

scholarly journals Effect of Ovality in Inlet Pigtail Pipe Bends Under Combined Internal Pressure and In-Plane Bending for Ni-Fe-Cr B407 Material

2017 ◽  
Vol 62 (3) ◽  
pp. 1881-1887
Author(s):  
P. Ramaswami ◽  
P. Senthil Velmurugan ◽  
R. Rajasekar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Limit Load ◽  
Outer Radius ◽  
Factor H ◽  
Geometrical Shape ◽  
Element Analysis ◽  
Pipe Bend ◽  
Plane Bending

Abstract The present paper makes an attempt to depict the effect of ovality in the inlet pigtail pipe bend of a reformer under combined internal pressure and in-plane bending. Finite element analysis (FEA) and experiments have been used. An incoloy Ni-Fe-Cr B407 alloy material was considered for study and assumed to be elastic-perfectly plastic in behavior. The design of pipe bend is based on ASME B31.3 standard and during manufacturing process, it is challenging to avoid thickening on the inner radius and thinning on the outer radius of pipe bend. This geometrical shape imperfection is known as ovality and its effect needs investigation which is considered for the study. The finite element analysis (ANSYS-workbench) results showed that ovality affects the load carrying capacity of the pipe bend and it was varying with bend factor (h). By data fitting of finite element results, an empirical formula for the limit load of inlet pigtail pipe bend with ovality has been proposed, which is validated by experiments.

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