Study of Influence Factors on the CTOA Toughness Values by Experiment/Simulation Method

2010 ◽  
Author(s):  
Junqiang Wang ◽  
Shuai Jian ◽  
Xuerui Xu
Keyword(s):  
Finite Element ◽  
Crack Extension ◽  
Pipeline Steel ◽  
Influence Factors ◽  
Opening Angle ◽  
Specimen Thickness ◽  
Test Machine ◽  
X80 Pipeline Steel ◽  
Element Analysis ◽  
Uniaxial Test

Although the crack-tip-opening angle (CTOA) has been widely recognized as an efficient fracture criterion for modeling stable crack growth and instability during the fracture process, the variation of its toughness value with many different kinds of factors changing for specific material during steady crack extension has been the focus of attention, such as specimen thickness, crack tunneling, notch shape, displacement rate, etc. At first, the present paper reviewed a variety of fracture parameters assessing the stable crack extension for ductile fracture toughness of pipelines steels or aluminum alloys. It was summarized that a few of test techniques and calculation methods available for determination of CTOA toughness, and the development of relative testing standards. Furthermore, the focus for this paper was to discuss a variety of influence factors of the CTOA toughness values in accordance with the results from the CTOA testing and finite element simulation of X70 and X80 steel specimens with different ligament thickness and the relative published articles. To compare the different CTOA values obtained by using direct surface methods and indirect methods from finite element analyses (FEA), CTOA toughness values of X70 and X80 pipeline steel were measured with a modified double-cantilever beam (MDCB) specimen in the servo-hydraulic uniaxial test machine. The gauge thicknesses included 4, 8 and 10 mm. The result of this study showed that critical CTOA values decreased with gauge thickness increasing. It was found that the computed surface CTOA in 3-D finite element analysis was generally lower than direct surface CTOA in the experimental measurement.

Application of Constraint Corrected J-R Curves to Fracture Analysis of Pipelines

2005 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Crack Tip ◽  
Mathematical Expression ◽  
Width Ratio ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Element Analysis

Fracture properties of API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimental J-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for X80. It is shown that the predicted J-R curves developed in this paper match well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.

Application of Constraint Corrected J-R Curves to Fracture Analysis of Pipelines

2005 ◽  
Vol 128 (4) ◽  
pp. 581-589 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Crack Tip ◽  
Mathematical Expression ◽  
Width Ratio ◽  
Single Edge ◽  
X80 Pipeline Steel ◽  
Element Analysis

Fracture properties of an API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for the X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimentalJ-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for the X80. It is shown that the predicted J-R curves developed in this paper agree well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.

scholarly journals Influence Factors Analysis of RC Beams under Falling Weight Impact Based on HJC Model

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Xiaohong Long ◽  
Ahmed Turgun ◽  
Rong Yue ◽  
Yongtao Ma ◽  
Hui Luo
Keyword(s):  
Finite Element ◽  
Impact Load ◽  
Influence Factors ◽  
Response Analysis ◽  
Impact Loads ◽  
Rc Beams ◽  
Element Analysis ◽  
Structure Component ◽  
Weight Impact ◽  
Falling Weight

Impact loads may cause serious or even fatal damage to the structure (component), in most existing specifications in China, and there are no special terms that take impact load into consideration. So, the response analysis of the structure (component) under impact loads is very important. In this paper, the sensitivity analysis was conducted for the 22 parameters of the Holmquist–Johnson concrete (HJC) constitutive model of concrete, and the sensitive parameters of the HJC model are identified with A, B, G, Pl, μl, and fc respectively. LS-DYNA nonlinear transient finite element analysis code was used for this paper. Based on the validation of finite element modeling and choosing midspan deflection of RC beams and impact loads as response indices, some influencing factors on RC beams under falling weight impact were investigated, such as the mass and speed of falling weight, impact position, the strength of concrete and rebar, longitudinal reinforcement ratio, and the span of the beam.

Creep Crack Initiation in a Weld Steel: Effects of Residual Stress

2005 ◽  
Author(s):  
Noel P. O’Dowd ◽  
Kamran M. Nikbin ◽  
Farid R. Biglari
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Crack Initiation ◽  
Equivalent Stress ◽  
Stress Triaxiality ◽  
Compact Tension ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Creep Ductility ◽  
Uniaxial Test

In this paper, the effect of residual stress on the initiation of a crack at high temperature in a Type 347 austenitic steel weld is examined using the finite element method. Both two and three dimensional analyses have been carried out. Residual stresses have been introduced by prior mechanical deformation, using a previously developed notched compact tension specimen. It has been found that for the 347 weld material, peak stresses in the vicinity of the notch are approximately three times the yield strength at room temperature and the level of stress triaxiality (ratio between hydrostatic and equivalent stress) is approximately 1 (considerably higher than that for a uniaxial test). The finite element analysis includes the effects of stress redistribution and damage accumulation under creep conditions. For the case examined the analysis predicts that crack initiation will occur under conditions of stress relaxation if the uniaxial creep ductility of the material is less than 2.5%. Furthermore, the predicted life of the component under constant load (creep conditions) is significantly reduced due to the presence of the residual stress field.

Application of Finite Element Analysis for the Prediction of the Fatigue Lifetime of Spot Welds with Triple SPCC plates

2007 ◽  
Vol 345-346 ◽  
pp. 1453-1456
Author(s):  
Byoung Ho Choi ◽  
Dong Ho Joo ◽  
Sam Hong Song
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shell Model ◽  
Crack Opening ◽  
Equivalent Stress ◽  
Shear Loading ◽  
Opening Angle ◽  
Element Analysis ◽  
Fatigue Lifetime ◽  
Empirical Prediction

The fatigue characteristic of triple spot welded SPCC plates with the variation of the thickness and the geometry under tensile-shear loading is studied by finite element analysis (FEA) and the obtained data is compared with experimental data. Using 3-D solid element model and 3-D beam-shell model, the maximum equivalent stress and the beam deformation angle (BDA) for various thickness and geometry is studied. The linear relation between crack opening angle (COA) from experiment and the BDA from FEA for beam-shell model is represented, and the empirical prediction of fatigue lifetime is proposed using the relation between COA and BDA.

Three-Dimensional Finite Element Analysis of Elastic-Plastic Crack Problems

1981 ◽  
Vol 103 (3) ◽  
pp. 214-218 ◽  
Author(s):  
B. V. Kiefer ◽  
P. D. Hilton
Keyword(s):  
Finite Element ◽  
Normal Stress ◽  
Crack Front ◽  
Stress Component ◽  
Three Dimensional ◽  
Specimen Thickness ◽  
Element Analysis ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Crack Problems

A three-dimensional, elastic-plastic finite element program is developed and applied to analyze the stress field in a plate containing a through crack. The center cracked plate is subjected to uniform tensile loading which results in mode I opening of the crack surfaces. Transverse variations of the opening tensile stress component and of the effective stress (von Mises) in the vicinity of the crack front are presented. They clearly demonstrate the three-dimensional nature of this problem with distributions that depend on specimen thickness. For thinner plates, the plastic deformation concentrates near the plate surfaces while the normal stress is largest in the plate interior. In thicker plates the deformation and normal stress fields are more uniform in the plate interior near the crack front, but they develop a rapid boundary layer-type variation in the vicinity of the plate surfaces.

Fast Ductile Fracture: Dependence of Propagation Resistance on Crack Velocity

2018 ◽  
Author(s):  
Chris Bassindale ◽  
Xin Wang ◽  
William R. Tyson ◽  
Su Xu
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Crack Velocity ◽  
Cohesive Zone Model ◽  
Pipeline Steel ◽  
Mass Density ◽  
Opening Angle ◽  
Zone Model ◽  
Plate Model ◽  
Line Pipe

In this paper, the effect of inertia on the steady-state velocity of a propagating crack in a modern high toughness pipeline steel was investigated. The line pipe steel examined in this work was an American Petroleum Institute (API) Standard X70 steel. A tensile plate model, simplified from the geometry of a pipe, was studied using the finite element code ABAQUS 6.14-2. The cohesive zone model (CZM) was used to simulate crack propagation. The CZM parameters were calibrated based on matching the crack tip opening angle (CTOA) measured from a drop-weight tear test (DWTT) finite element model to the experimental CTOA of the material. The CZM parameters were then applied to the tensile plate model. The effect of inertia on the steady-state crack velocity was systematically assessed by altering the density of the material used with the plate model. To isolate the influence of inertia, the effect of strain rate on the fracture process and material plasticity was neglected. The results of this study demonstrate that the steady-state crack velocity was affected by the density of the material. The steady-state crack velocity was reduced with increasing mass density, as demonstrated by the effect of backfill. Furthermore, it was shown that the CTOA extracted from the CZ model was not affected by the density of the model.

Study on the Influence Factors of Honing Efficiency

2013 ◽  
Vol 655-657 ◽  
pp. 1204-1209
Author(s):  
Yong Gui Zhang ◽  
Jun Kai Niu ◽  
Yun Jiang Yang ◽  
Jun Gong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Theoretical Basis ◽  
High Efficiency ◽  
Influence Factors ◽  
Matlab Simulation ◽  
Technological Parameters ◽  
Element Analysis ◽  
Selection Of

According to the requirements of optimization for honing efficiency ,Through Matlab simulation and finite element analysis, this paper studied the influence factors of reticulate pattern quality and honing efficiency. These factors contain honing speed, reversing acceleration, oil-stone. This paper provides certain theoretical basis for reasonable selection of key technological parameters in high efficiency honing process .

Numerical Study of the Crack-Front Constraint for SENT Specimens of X80 Pipeline Steel

2017 ◽  
Vol 898 ◽  
pp. 735-740
Author(s):  
Ting Zhong ◽  
Lin Zhu ◽  
Yan Zhou ◽  
Jian Shuai ◽  
Lan He
Keyword(s):  
Crack Front ◽  
Numerical Study ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Stress Triaxiality ◽  
Width Ratio ◽  
Specimen Thickness ◽  
X80 Pipeline Steel ◽  
Specimen Width ◽  
Average Measure

This work presents a numerical study of crack-front constraint for SENT specimens of X80 pipeline steel, to examine geometry effect on the correlation of crack-front stress field and constraint. An average measure of constraint over crack-front Am was employed to characterize the crack-front constraint. SENT specimens with varying geometries (different crack depth to specimen width ratio, a/W, and different specimen width and thickness, W/B) were analyzed by Gurson-Tvergaard-Needleman model (GTN model). Results showed that the stress triaxiality Am can characterize the crack-front constraint of X80 pipeline steel very well. The level of the Am-△a curve rises with the decrease of crack depth, and increases first and then decreases with the increase of SENT specimen thickness.

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