Displacement Controlled Stress Intensity Factor Solutions for Structural Integrity Assessments of Welding Residual Stress Distributions

2008 ◽  
Author(s):  
Adam Toft ◽  
David Beardsmore ◽  
Colin Madew ◽  
Huego Teng ◽  
Mark Jackson
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Weight Function ◽  
Driving Force ◽  
Welding Residual Stress ◽  
Crack Plane ◽  
Crack Driving Force

Within the UK nuclear industry the assessment of fracture in pressurised components is often carried out using procedures to calculate the margin of safety between a lower-bound fracture toughness and the crack driving force. Determination of the crack driving force usually requires the calculation of elastic stress intensity factor solutions for primary loads and secondary loads arising from weld residual stresses and/or thermal stresses. Within established UK assessment procedures weight function solutions are available which allow the stress intensity factors to be calculated from the through-wall opening-mode stress distribution in an uncracked component. These weight-function solutions are generally based on models where either no boundary condition is applied, or where one is applied at a distance either side of the crack plane that is very long compared with the crack size and wall thickness. Such solutions do not take into account any reduction in the stress field that might occur as the distance from the crack faces increases. Weld residual stress fields may often be expected to reduce in this manner. A separate, earlier study has shown that the stress intensity factor for a cracked plate loaded in displacement control decreases substantially as the loading plane is moved closer to the crack plane. It would therefore be expected that a similar reduction in stress intensity factor would be obtained for a residual stress analysis when displacement boundary conditions are imposed at a distance relatively close to the crack plane. This paper describes an investigation of the differences, particularly in terms of a reduction in calculated stress intensity factor, which may arise from application of displacement controlled stress intensity factor solutions, as compared with load controlled solutions, when considering weld residual stresses. Consideration is also given as to how new displacement controlled stress intensity factor solutions could be developed by modification of existing load controlled solutions.

Modelling shattered rim cracking in railroad wheels

2011 ◽  
Vol 225 (6) ◽  
pp. 593-604
Author(s):  
V Sura ◽  
S Mahadevan
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress State ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Equivalent Stress ◽  
Crack Tip ◽  
Residual Stress State

Shattered rim cracking, propagation of a subsurface crack parallel to the tread surface, is one of the dominant railroad wheel failure types observed in North America. This crack initiation and propagation life depends on several factors, such as wheel rim thickness, wheel load, residual stresses in the rim, and the size and location of material defects in the rim. This article investigates the effect of the above-mentioned parameters on shattered rim cracking, using finite element analysis and fracture mechanics. This cracking is modelled using a three-dimensional, multiresolution, elastic–plastic finite element model of a railroad wheel. Material defects are modelled as mathematically sharp cracks. Rolling contact loading is simulated by applying the wheel load on the tread surface over a Hertzian contact area. The equivalent stress intensity factor ranges at the subsurface crack tips are estimated using uni-modal stress intensity factors obtained from the finite element analysis and a mixed-mode crack growth model. The residual stress and wheel wear effects are also included in modelling shattered rim cracking. The analysis results show that the sensitive depth below the tread surface for shattered rim cracking ranges from 19.05 to 22.23 mm, which is in good agreement with field observations. The relationship of the equivalent stress intensity factor (Δ K eq) at the crack tip to the load magnitude is observed to be approximately linear. The analysis results show that the equivalent stress intensity factor (Δ K eq) at the crack tip depends significantly on the residual stress state in the wheel. Consideration of as-manufactured residual stresses decreases the Δ K eq at the crack tip by about 40 per cent compared to that of no residual stress state, whereas consideration of service-induced residual stresses increases the Δ K eq at the crack tip by about 50 per cent compared to that of as-manufactured residual stress state. In summary, the methodology developed in this article can help to predict whether a shattered rim crack will propagate for a given set of parameters, such as load magnitude, rim thickness, crack size, crack location, and residual stress state.

Study on Evaluation Procedure for Calculating the Stress Intensity Factor of Flaws Beneath RPV Cladding During Pressurised Thermal Shock Events by FE Analysis

2016 ◽  
Author(s):  
Hiroyuki Sakamoto ◽  
Takatoshi Hirota ◽  
Naoki Ogawa
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Thermal Shock ◽  
Alloy Steel ◽  
Fe Analysis ◽  
Welding Residual Stress ◽  
Low Alloy Steel ◽  
Elastic Plastic

Elastic-plastic finite element (FE) analysis is performed to determine the plastic behavior of the reactor pressure vessel (RPV) inner surface caused by rapid cooling during pressurized thermal shock (PTS) events. However, as the J-integral is not path-independent for elastic-plastic material in the unloading process, it is necessary to apply a suitable correction method using elastic material. In addition, it is also necessary to consider the effect of the welding residual stress appropriately. Therefore, we investigated the stress intensity factor derived from FE analysis based on a model consisting of elastic-plastic cladding and linear elastic low-alloy steel with subsequent plastic zone correction, since the stress level of low-alloy steel remains within the elastic region except the crack front during a PTS event. Furthermore, we examined whether the stress mapping method is applicable for reflecting the effect of welding residual stress in FE analysis, even though the plastic strain generated during welding is ignored.

R-curve measurements in PSZ ceramics

1990 ◽  
Vol 5 (7) ◽  
pp. 1490-1495 ◽  
Author(s):  
S. Srinivasan ◽  
R. O. Scattergood
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Applied Stress ◽  
Power Law ◽  
Driving Force ◽  
Stress Constraints ◽  
Failure Stress ◽  
Transformation Stress

An indentation-bend failure-stress method was used for measurement of R-curves in a series of PSZ ceramics with varying peak toughness. Dilatational transformation-stress constraints are included in the residual-stress driving force contribution to the applied stress intensity factor. A power-law fit to the form of the R-curve simplifies the analysis. While the resulting curves show the expected form, measured toughness values are high relative to the expected peak toughness. Limitations and the range of applicability of the indentation-bend technique are discussed.

Construction of a Dynamic Weight Function From a Finite-Element Solution for a Cracked Beam

1980 ◽  
Vol 47 (1) ◽  
pp. 51-56 ◽  
Author(s):  
H. J. Petroski ◽  
J. L. Glazik ◽  
J. D. Achenbach
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Weight Function ◽  
Crack Plane ◽  
Cracked Beam ◽  
Crack Face ◽  
Dynamic Weight ◽  
Dynamic Loadings

An elastodynamic weight function for a cracked beam is shown to be determined by the elastodynamic stress intensity factor corresponding to a single crack-face loading of the beam. This weight function suffices to determine the time-dependent stress intensity factor corresponding to other dynamic loadings of the same cracked beam. The example of a center-cracked pinned-pinned beam serves to illustrate and verify the technique. The weight function is constructed from finite element results for the case of a step pressure distributed uniformly along the beam, and the case of a step load concentrated at the crack plane serves as an illustration of the efficacy of the weight function so constructed.

Fatigue Life Prediction of Ship Welded Materials

2005 ◽  
Vol 297-300 ◽  
pp. 743-749
Author(s):  
Min Koo Han ◽  
Mamidala Ramulu
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Crack Closure ◽  
Fatigue Cracks ◽  
Welding Process ◽  
Weld Toe

Fatigue crack propagation life of weld toe crack through residual stress field was estimated using Elber's crack closure concept. Propagation of weld toe crack is heavily influenced by residual stresses caused by the welding process, so it is essential to take into account the effect of residual stresses on the propagation life of a weld toe crack. Fatigue cracks at transverse and longitudinal weld toe was studied, these two cases represent the typical weld joints in ship structures. Numerical and experimental studies are performed for both cases. Residual stresses near the welding area were estimated through a nonlinear thermo-elasto-plastic finite element method and the residual stress intensity factor with Glinka's weight function method. Effective stress intensity factor was calculated using the Newman-Forman-de Koning-Henriksen equation, which is based on the Dugdale strip yield model in estimating the crack closure level, U, at different stress ratios. Calculated crack propagation life coincided well with experimental results.

Investigation of Hydrogen Assisted Cracking in High and Low Strength Steels

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Samerjit Homrossukon ◽  
Sheldon Mostovoy ◽  
Judith A. Todd
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Driving Force ◽  
High Strength ◽  
Crack Driving Force ◽  
Hydrogen Assisted Cracking ◽  
Threshold Stress Intensity Factor ◽  
Low Strength ◽  
Point Bend

Hydrogen assisted cracking (HAC) has been investigated in a high strength 4140 steel and a low strength AISI-SAE grade 1022 steel (supplied by Amoco, Naperville, IL—now BP), charged at −50 mA/cm2 in 1N H2SO4+25 mg/lAs2O3 and tested under three-point-bend decreasing load. The HAC growth rate for the 1022 steel (1.4×10−7 cm/s) was found to be approximately two orders of magnitude slower than that of the 4140 steel (3.3×10−5 cm/s), while the threshold stress intensity factor for the 1022 steel (37.0±1.0 MPa m1/2) was significantly higher than that of the 4140 steel (7.0±0.5 MPa m1/2). This research develops an analytical model, based on the hypothesis that hydrogen both reduces crack resistance (R) and increases crack driving force (G), to explain HAC in 4140 and 1022 steels. The model predicts the hydrogen concentration required to initiate HAC as a function of the applied stress intensity factor and yield strength of the steel. Hydrogen-induced reduction in R was found to dominate HAC in the 4140 steel, while hydrogen-induced reduction in R was combined with an increase in G for HAC cracking of the 1022 steel.

Influence of Welding Residual Stress on Stress Intensity Factor of Two-Dimensional Cracks

2011 ◽  
Vol 299-300 ◽  
pp. 966-969
Author(s):  
Jin Song Yang ◽  
Wei Jiang
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Crack Propagation ◽  
Crack Front ◽  
Welding Residual Stress ◽  
Two Dimensional ◽  
Residual Stress Field

In this paper, a butt-welded plate with cracks of different sizes and locations was used to analyze the crack propagation in the residual stress field. A two-dimensional finite element model was established to study the distributions of stress intensity factor along crack front in the residual stress field. Several cases with different crack lengths and angles were investigated. It was found that the distributions of stress intensity factor along crack front were very sensitive to residual stress. The methods and results presented in this paper are capable of providing a reference for the efficient assessment of the effect of residual stress field on the crack propagation behavior. It also implies that proper welding procedures are required for acceptable residual stress distributions to ensure prolonged service life of weldments.

Fatigue Crack Driving Force for Axial Surface Cracks in Pipes

2006 ◽  
Author(s):  
G. Shen ◽  
S. M. Adeeb ◽  
R. I. Coote ◽  
D. J. Horsley ◽  
W. R. Tyson ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Driving Force ◽  
Stress Intensity Factor Range ◽  
Crack Driving Force ◽  
Rectangular Crack ◽  
Thin Walled

Fatigue life assessment procedures require knowledge of the fatigue crack driving force, such as stress intensity factor range (ΔK) and cyclic J-integral (ΔJ), for the flaw geometry detected during inspection. Because three-dimensional closed-form crack driving force solutions are not available for typical flaws in pipelines, it is common practice to obtain these solutions from finite element analysis (FEA) or to adopt a closed-form crack driving force solution for the equivalent flawed plate and include a correction factor to take account of the pipe bulging effect. In the present study, pipes and plates with an axial rectangular crack with filleted corners under fatigue loading are simulated by FEA. The initial results show that the stress intensity factor range (ΔK) for a thin-walled pipe with a shallow crack (a/t < 0.5) is given reasonably well by the bulging factors given in BS 7910 combined with the stress intensity factor equation given by Newman and Raju for a plate with a semi-elliptical crack. However, the stress intensity factor is significantly over-estimated for a long and deep crack using this procedure. Different parameters for elastic-plastic fatigue are calculated and are proposed to be correlated with the rate of crack growth for thin-walled pipes with an axial rectangular crack with filleted corners. It is intended to use the results presented here in combination with full scale experimental fatigue data to obtain pipeline fatigue crack growth formulations, to accurately predict the rate of crack growth within a pipeline due to fluctuating internal pressure.

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