Fatigue Life Estimation of Welded Joints Including the Effects of Crack Closure Phenomena

2011 ◽  
Author(s):  
Diego Felipe Sarzosa Burgos ◽  
Claudio Ruggieri ◽  
Leonardo Barbosa Godefroid ◽  
Gustavo H. B. Donato
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Weld Strength ◽  
Operating Life ◽  
Mechanical Heterogeneity

The integrity of mechanical components, particularly when they experience considerable fatigue damage during its operating life, can be strongly influenced by the presence of residual stress fields and mechanical heterogeneity. Premature closure of crack flanks greatly influences fatigue crack growth rate. Extensive elastic-plastic finite element analyses have been carried out to investigate detailed crack closure behavior in center cracked welded compact tension (CT) specimens with one level of weld strength mismatch. The finite element results show that homogeneous, soft material has higher crack opening loads than heterogeneous material with 50% overmatch conditions. Fracture testing conducted on C(T) specimens to measure fatigue crack growth rates for an ASTM A516 Gr. 70 steel weldment provide the experimental data to support such behavior. The fatigue life can be reduced by more than 100% for a condition of 50% overmatch when compared with the evenmatch condition. It was verified that most of time spent in fatigue propagation life is consumed at the beginning of the propagation life.

Characterizing Fatigue Crack Closure by Numerical Analysis

2008 ◽  
Vol 33-37 ◽  
pp. 273-278 ◽  
Author(s):  
Ya Zhi Li ◽  
Jing He ◽  
Zi Peng Zhang ◽  
Liang Wang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Numerical Analysis ◽  
Fatigue Crack Growth ◽  
Crack Length ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Crack Tip ◽  
Fatigue Crack Closure

The crack closure phenomenon has attracted great attention in the prediction of fatigue crack growth. The finite element analysis of fatigue crack growth has been conducted by many researchers mainly emphasized on the technique implementation of the simulation. In this paper the behavior of plasticity induced fatigue crack closure was analyzed by the elastic-plastic finite element method for middle crack tension (MT) specimen. The material was assumed as linear-kinematic hardening. The crack growth was simulated by releasing the “bonded” node pairs ahead of crack tip in stepwise. The calculations focused on the effects of load cases and crack length on crack opening/closure levels. For constant amplitude cyclic loadings with different load ratios, the crack opening/closure levels increases for a while and then decreases continuously, with the increase of crack length. For the loadings with invariable maximum stress intensity factors (briefly the constant-K loading), however, the crack tip plastic zone sizes at different crack lengths remain unchanged and the crack opening and closing load levels normalized by the maximum load levels keep constants as well. The results indicate that the crack length does not affect the relative opening and closure levels and numerical analysis for the constant-K loading case should play a key role in characterizing the fatigue crack growth behavior.

Fatigue Crack Growth Prediction of Elliptical Corner Crack Using 3D FEM

2012 ◽  
Vol 248 ◽  
pp. 469-474
Author(s):  
M.H. Gozin ◽  
M. Aghaie-Khafri
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Front ◽  
Crack Opening ◽  
3D Fem ◽  
Corner Crack ◽  
Closure Method

Plasticity induced crack closure (PICC) simulation using finite element analyses has been concerned by many researchers. In the present investigation elliptical corner fatigue crack growth from a hole was predicted using PICC method. An elastic-plastic finite element model is built with a suitably refined mesh and time-dependent remote tractions are applied to simulate cyclic loading. In a 3D geometry the crack opening value will vary along the crack front. For simplicity this shape evolution is neglected and the crack front is extended uniformly. Predicted fatigue life using crack closure method for elliptical corner crack is in good agreement with the experimental data. The results obtained highlighted the sensitivity of crack closure method to the opening stress intensity values.

Experimental and Numerical Investigation of Plasticity-Induced Fatigue Crack Closure in Overmatched Welds

2013 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Claudio Ruggieri
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Compact Tension ◽  
Cyclic Stress ◽  
Growth Behavior ◽  
Weld Strength ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior

This work provides a numerical and experimental investigation of fatigue crack growth behavior in steel weldments including crack closure effects and their coupled interaction with weld strength mismatch. A central objective of this study is to extend previously developed frameworks for evaluation of crack closure effects on fatigue crack growth rates (FCGR) to steel weldments while, at the same time, gaining additional understanding of commonly adopted criteria for crack closure loads. Very detailed non-linear finite element analyses using 3-D models of compact tension C(T) fracture specimens with square groove, weld centerline cracked welds provide the evolution of crack growth with cyclic stress intensity factor which is required for the estimation of the closure loads. Fatigue crack growth tests conducted on plane-sided, shallow-cracked C(T) specimens provide the necessary data against which crack closure effects on fatigue crack growth behavior can be assessed. Overall, the present investigation provides additional support for estimation procedures of plasticity-induced crack closure loads in fatigue analyses of structural steels and their weldments.

Constraint Effects on the Prediction of Fatigue Life of Surface Flaws

1983 ◽  
Vol 105 (3) ◽  
pp. 215-218 ◽  
Author(s):  
M. Jolles
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Stress Field ◽  
Crack Growth ◽  
Crack Closure ◽  
Growth Analysis ◽  
Crack Shape ◽  
Surface Flaws ◽  
Constraint Effects

The effects of the variation of stress field triaxiality on the prediction of the fatigue growth of semielliptic surface flaws are investigated. The concepts of crack closure are used in a fatigue growth analysis to account for constraint variation. The analysis, together with a traditional fatigue crack growth analysis which does not account for constraint variation, is used to predict flaw growth observed in experiments. Significant improvements in predicted fatigue life, as well as predicted crack shape, are obtained by accounting for the variation in constraint.

scholarly journals A Novel Methodology for Calculating Crack Opening Stress under Tension-Compression Cyclic Load

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Lin Zhang ◽  
Xiaohui Wei
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Compressive Load ◽  
Load Effect ◽  
Compression Load ◽  
Fatigue Crack Growth Life ◽  
Crack Opening Stress

Crack closure model has been used in several applications on the prediction of fatigue crack growth life, with expression of crack opening stress often serving as milestones. A typical difficulty in calculating the crack opening stress is the phenomenon of crack closure caused by the compressive load effect. Compressive load effect, resulting in the change of residual stress status at the unloading stage and the decrease of crack opening stress, is a long-term challenge for predicting fatigue crack growth life. We propose the expression of crack opening stress to predict fatigue crack growth life based on the analysis of compact tensile specimen with elastoplastic element method. It combines the characteristics of material and load to deal with the phenomenon of crack closure and uses stress ratio and normalized maximum applied load variable to construct the expression of crack opening stress. In the study of tensile-compression fatigue crack growth experiments, the proposed expression is proved to improve, by comparative analysis, the predictive ability on the whole range of experiment data. The novel expression is accurate and simple. Consequently, it is conducive to calculate the crack opening stress under tension-compression load.

Accounting for Negative R-Ratio (Crack Closure) in Fatigue Crack Growth Calculations on Stainless Steel Components

2015 ◽  
Author(s):  
Chris Watson ◽  
Chris Currie ◽  
Julian Emslie
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Stress Range ◽  
Stress Cycle ◽  
R Ratio ◽  
Cylindrical Test

Negative R-ratio crack closure effects on Fatigue Crack Growth (FCG) are defined as the contribution of the compressive portion of the stress cycle to the crack extension, in addition to that contributed from the tensile portion of the cycle. Any potential decrease in FCG may be attributed to the mechanical effects of crack closure during the compressive part of the cycle. The overall effect is to decrease the crack opening portion of the stress range and to therefore reduce the crack growth rate compared to that obtained using the full stress range. This paper provides a brief overview of the treatment of negative R-ratio crack closure in FCG calculations on stainless steel components by reference to existing codes and standards. Then, using the results from crack closure tests on small cylindrical test specimens, a set of guidelines for the treatment of crack closure in the FCG assessment of stainless steel components are provided.

The Fatigue Life Estimation Method From the Stress Concentration Region With Zero Defect: An Application to the Fatigue Crack Growth Simulation Code “FLARP” for the In-Plane Gusset Welded Joint

2004 ◽  
Author(s):  
Masahiro Toyosada ◽  
Koji Gotoh ◽  
Keitaro Konuma ◽  
Akira Sueda
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Opening ◽  
Simulation Code ◽  
Growth Simulation ◽  
Life Estimation ◽  
Crack Growth Simulation ◽  
Fatigue Life Estimation

In-plane gusset welded joints are very popular and used in many steel constructed structures. Fatigue life estimations for this type of joint have been performed by applying the fatigue crack growth simulation code “FLARP” developed by the authors. The fatigue crack shows the typical opening/closing behavior during fatigue crack growth. The plastic deformed layer in the crack wake, which represents the loading history indirectly, contributes to the behavior. The consideration of crack closure is essential in the estimation of the fatigue life. FLARP enables the quantitative simulation of the fatigue crack opening/closing. By considering the cyclic plastic behavior ahead of a fatigue crack tip, the improved effective stress intensity factor range (ΔKRPG) to denote the fatigue crack propagation law, which is formulated by replacing the crack opening load with the Retensile Plastic zone Generating load (RPG load), was defined. ΔKRPG is adopted as the parameter for the fatigue life estimation by FLARP. The validity of the fatigue life estimation by FLARP is confirmed by comparing the estimated S-N curves with the experimental results for the in-plane gusset welded joints.

Plane Strain Crack Growth Models for Fatigue Crack Growth Life Predictions

1996 ◽  
Vol 118 (1) ◽  
pp. 78-85 ◽  
Author(s):  
J. M. Bloom ◽  
S. R. Daniewicz ◽  
J. L Hechmer
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Opening ◽  
Constraint Factor ◽  
R Ratio ◽  
Point Bend

Experimental data and analytical models have shown that a growing fatigue crack produces a plastic wake. This, in turn, leads to residual compressive stresses acting over the crack faces during the unloading portion of the fatigue cycle. This crack closure effect results in an applied stress intensity factor during unloading which is greater than that associated with the Kmin, thus producing a crack-driving force which is less than ΔK = Kmax − Kmin. Life predictions which do not account for this crack closure effect give inaccurate life estimates, especially for fully reversed loadings. This paper discusses the development of a crack closure expression for the 4- point bend specimen using numerical results obtained from a modified strip-yield model. Data from tests of eight 4-point bend specimens were used to estimate the specimen constraint factor (stress triaxiality effect). The constraint factor was then used in the estimation of the crack opening stresses for each of the bend tests. The numerically estimated crack opening stresses were used to develop an effective stress intensity factor range, ΔKeff The resulting crack growth rate data when plotted versus ΔKeff resulted in a material fatigue crack growth rate property curve independent of test specimen type, stress level, and R-ratio. Fatigue crack growth rate data from center-cracked panels using Newman's crack closure model, from compact specimens using Eason 's R-ratio expression, and from bend specimens using the model discussed in this paper are all shown to fall along the same straight line (on log-log paper) when plotted versus ΔKeff, even though crack closure differs for each specimen type.

A Finite Element Procedure to Model the Effect of Hydrostatic Testing on Subsequent Fatigue Crack Growth

2016 ◽  
Author(s):  
Ted L. Anderson ◽  
Greg V. Thorwald
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Relative Effect ◽  
Operating Pressure ◽  
Metallic Structures ◽  
Test Pressure ◽  
Finite Element Procedure

Hydrostatic testing of pipelines that are subject to pressure cycling and fatigue damage can alter the intrinsic characteristics of flaws that survive the test. The effect is generally favorable, as test pressures well above the maximum operating pressure (MOP) can significantly reduce the subsequent rate of fatigue crack growth. The phenomenon is known as fatigue retardation, which is caused by crack closure due to compressive residual stresses created by plastic deformation during the hydrotest. Fatigue retardation following an overload event is a well-known phenomenon in metallic structures, but there has been little or no effort to take advantage of this beneficial effect in pipelines. This paper presents a modeling procedure aimed at quantifying fatigue retardation following a hydrostatic test. A series of 3D elastic-plastic finite element simulations have been performed to model fatigue crack growth following a pressure test. The effect of test pressure and MOP on plasticity-induced crack closure was studied. The relative effect of fatigue retardation on remaining life was demonstrated with several examples. In some cases, the results were counter intuitive.

Modeling of Fatigue Crack Closure by Finite Element Method

2012 ◽  
Vol 544 ◽  
pp. 145-150
Author(s):  
Zhen Yu Ding ◽  
Xiao Gui Wang ◽  
Zeng Liang Gao
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Closure ◽  
Fe Simulation ◽  
Crack Tip ◽  
Cyclic Plasticity ◽  
Stress And Strain

Crack closure concept is often used to explain the crack propagation behavior in cracked components. The effective stress intensity factor range is considered as a driving force of fatigue crack growth based on the traditional crack closure concept. The crack closure process and the plastic deformation near the crack tip were discussed in this paper. The standard compact tension specimen with the plane-stress condition was used to study the crack closure. A dynamic crack propagation method was proposed to simulate the effect of previous fatigue crack growth on the successive crack growth behavior. To obtain the accurately numerical results of stress and strain components, the Jiang and Sehitoglu cyclic plasticity model was implemented into ABAQUS as UMAT. With the detailed stress and strain response taken from the finite element (FE) simulation, the whole process of crack closure was described by the load curve. The load corresponding to maximum crack closure length is firstly proposed to describe the effect of fatigue damage. According to the results of FE simulation, the cyclic plasticity of the material near the crack tip persists during the crack closure period and should not be ignored.

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