scholarly journals Effect of Mechanical Heterogeneity on Strain and Stress Fields at Crack Tips of SCC in Dissimilar Metal Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4450
Author(s):  
Shun Zhang ◽  
He Xue ◽  
Shuai Wang ◽  
Yuman Sun ◽  
Fuqiang Yang ◽  
...  
Keyword(s):  
Stress State ◽  
Plastic Zone ◽  
Weld Metal ◽  
Base Metal ◽  
Work Hardening ◽  
Crack Tip ◽  
Stress Fields ◽  
J Integral ◽  
Dissimilar Metal ◽  
Crack Tips

The crack tip strain and stress condition are one of the main factors affecting stress corrosion cracking (SCC) behaviors in the dissimilar metal welded joint of the primary circuit in the pressurized water reactor. The mechanical property mismatch of base metal and weld metal can significantly affect the stress and strain condition around the crack tip. To understand the effect of different weld metals on strain and stress fields at SCC crack tips, the effects of strength mismatch, work hardening mismatch, and their synergy on the strain and stress field of SCC in the bi-material interface, including plastic zone, stress state, and corresponding J-integral, are investigated in small-scale yielding using the finite element method. The results show a significant effect of the strength mismatch and work hardening mismatch on the plastic zone and stress state in the weld metal and a negligible effect in the base metal. J-integral decreases with the single increase in either strength mismatch or work hardening mismatch. Either the increase in strength mismatch or work hardening mismatch will inhibit the other’s effect on the J-integral, and a synthetic mismatch factor can express this synergistic effect.

Characterization of the Microstructure and Toughness of DSAW and ERW Seam Welds of Older Linepipe Steels

2002 ◽  
Author(s):  
J. A. Gianetto ◽  
D. K. Mak ◽  
R. Bouchard ◽  
S. Xu ◽  
W. R. Tyson
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Electrical Resistance ◽  
Crack Tip ◽  
Charpy Impact ◽  
Initiation Toughness ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Linepipe Steel

The aim of the present work is to quantify the seam weld properties, including both weld metal and heat affected zone regions, for a series of double-submerged-arc welded pipe, and the base metal and bondline regions for an electrical resistance welded linepipe steel. The chemical composition, microstructure, microhardness, tensile properties, Charpy impact toughness and J-integral/crack-tip opening displacement fracture resistance were characterized for linepipe produced between 1953 and 1981. The toughness results of the base metal, heat affected zone and weld metal regions of the older (higher carbon) linepipes were significantly poorer than those obtained for a more modern low-C microalloyed linepipe steel. In the latter case the base metal, HAZ and weld metal regions failed by ductile fracture at room temperature in both fracture toughness (quasi-static) and Charpy impact tests. It was possible to show that there is a linear correlation between the J-integral at 0.2 mm crack growth and the upper shelf Charpy energy. It is, however, important to note that the Charpy transition temperatures of the older pipes are considerably higher than for the modern pipe. In the case of the electrical resistance weld, very poor toughness was observed for the bondline. Fracture occurred along the bondline in a brittle mode (cleavage) that was attributed to the formation of a coarse, relatively hard microstructure and the presence of inclusions along the bondline region. In addition, it was shown using base-metal BxB and Bx2B samples that initiation toughness is a function of the remaining uncracked ligament. This emphasizes the necessity of ensuring that the crack-tip constraint in the test specimens is similar to the constraint in the crack geometry being assessed.

Bilby–Cottrell–Swinden model for a growing crack with residual stresses

1970 ◽  
Vol 317 (1529) ◽  
pp. 199-209 ◽  
Keyword(s):  
Plastic Zone ◽  
Residual Stresses ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Relative Displacement ◽  
Planar Arrays ◽  
Plastic Dissipation ◽  
Growing Crack ◽  
Slip Planes ◽  
Crack Tips

For a growing crack the residual stresses caused by plastic flow at previous positions of the crack-tip affect the current plastic zone. This effect is calculated by an extension of the BCS model which replaces the plastic zone by two planar arrays of dislocations emanating from the crack-tips. For a growing crack a succession of such arrays is formed. We consider a crack growing in anti-plane strain with the slip-planes making an almost zero angle with the plane of the crack. The plastic zone size in front of the crack turns out to be the same as for a stationary crack, while the relative displacement of the crack faces is less concentrated in the vicinity of the crack-tip. The rate of plastic dissipation of energy is calculated, and turns out to be identical with the elastic energy release rate.

The interaction problem of two Zener–Stroh cracks with a nearby inhomogeneity

2017 ◽  
Vol 24 (3) ◽  
pp. 542-558
Author(s):  
M Fan ◽  
ZM Xiao ◽  
YM Zhang
Keyword(s):  
Plastic Zone ◽  
Influence Factors ◽  
Crack Tip ◽  
Singular Integral Equations ◽  
Plastic Zone Size ◽  
Circular Inclusion ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Tips ◽  
Crack Tip Opening

In this paper, the interaction among two Zener–Stroh cracks (with plastic zone correction) and a nearby circular inclusion are investigated. To evaluate the plastic zone sizes at crack tips in the current physical problem is a great challenge. As the first attempt to explore the multiple defects’ interaction effect on the yielding behavior of a crack, we focused on the analysis of one target crack, while the other crack and the circular inhomogeneity are treated as influence factors. With the help of coordinate transformation and superposition procedure, the formulated singular integral equations can be solved numerically. The influence of material properties, crack–crack positions and other parameters, such as crack length and Burgers vector of the Zener–Stroh crack, on the target crack tip stress intensity factor, plastic zone size and crack tip opening displacement are examined. It is found that the effects of the aforesaid parameters on the cracks are all inter-related and dependent on each other. This observation reveals the complexity of fracture analysis and the necessity to have a deep research on interacting defects in composite materials.

Influence of Surface Tension on Mixed-Mode Cracks

2015 ◽  
Vol 07 (05) ◽  
pp. 1550070 ◽  
Author(s):  
Yuan Li ◽  
Gang-Feng Wang
Keyword(s):  
Surface Tension ◽  
Mixed Mode ◽  
Crack Tip ◽  
Critical Stress Intensity Factor ◽  
Stress Fields ◽  
Strengthening Effect ◽  
J Integral ◽  
Mode Ii Crack ◽  
Sharp Crack ◽  
Good Agreement

Surface tension inherently exists on free surface, and its effect becomes quite important at sharp crack tip. In the present paper, we investigate the influence of surface tension on mixed-mode cracks by finite element method. It is found that surface tension significantly alters the stress fields and J-integral around crack tip, depending on the profile of crack tip. Generally, surface tension decreases the J-integral and thus enhances material toughness, especially for sharp crack. Based on the criteria of energy release rate, the critical stress intensity factor (SIF) for brittle materials is also determined. Surface tension yields an enhanced critical SIF for mixed-mode cracks, and more significant strengthening effect is obtained for Mode-I crack than for Mode-II crack. Moreover, an analytical expression is advanced to characterize the influence of surface tension on fracture, which shows a good agreement with numerical calculations.

On improved crack tip plastic zone estimates based on T-stress and on complete stress fields

2012 ◽  
Vol 36 (1) ◽  
pp. 25-38 ◽  
Author(s):  
R. A. SOUSA ◽  
J. T. P. CASTRO ◽  
A. A. O. LOPES ◽  
L. F. MARTHA
Keyword(s):  
Plastic Zone ◽  
Crack Tip ◽  
Stress Fields ◽  
T Stress

On the Path-Dependence of the J-Integral Near a Stationary Crack in an Elastic-Plastic Material

2010 ◽  
Vol 78 (1) ◽  
Author(s):  
Dorinamaria Carka ◽  
Chad M. Landis
Keyword(s):  
Finite Element ◽  
Plastic Zone ◽  
Boundary Conditions ◽  
Path Dependence ◽  
Crack Tip ◽  
Mode I ◽  
Far Field ◽  
J Integral ◽  
Mode I Loading ◽  
Poisson's Ratios

The path-dependence of the J-integral is investigated numerically via the finite-element method, for a range of loadings, Poisson’s ratios, and hardening exponents within the context of J2-flow plasticity. Small-scale yielding assumptions are employed using Dirichlet-to-Neumann map boundary conditions on a circular boundary that encloses the plastic zone. This construct allows for a dense finite-element mesh within the plastic zone and accurate far-field boundary conditions. Details of the crack tip field that have been computed previously by others, including the existence of an elastic sector in mode I loading, are confirmed. The somewhat unexpected result is that J for a contour approaching zero radius around the crack tip is approximately 18% lower than the far-field value for mode I loading for Poisson’s ratios characteristic of metals. In contrast, practically no path-dependence is found for mode II. The applications of T- or S-stress, whether applied proportionally with the K-field or prior to K, have only a modest effect on the path-dependence.

scholarly journals Cracking Driving Force at the Tip of SCC under Heterogeneous Material Mechanics Model of Safe-End Dissimilar Metal-Welded Joints in PWR

2022 ◽  
Vol 2022 ◽  
pp. 1-10
Author(s):  
Yuman Sun ◽  
He Xue ◽  
Kuan Zhao ◽  
Yubiao Zhang ◽  
Youjun Zhao ◽  
...  
Keyword(s):  
Welded Joints ◽  
Material Properties ◽  
Driving Force ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Heterogeneous Material ◽  
J Integral ◽  
Promoting Effect ◽  
Pressurized Water ◽  
Dissimilar Metal

The complicated driving force at the stress corrosion cracking (SCC) tip of the safe-end dissimilar metal-welded joints (DMWJs) in the pressurized water reactor (PWR) is mainly caused by the heterogeneous material mechanical properties. In this research, to accurately evaluate the crack driving force at the SCC in DMWJs, the stress-strain condition, stress triaxiality, and J-integral of the crack tip at different positions are analyzed based on the heterogeneous material properties model. The results indicate that the larger driving force will be provided for the I-type crack when the crack is in the SA508 zone and the interface between the 316L region and base metal. In addition, the heterogeneous material properties inhibit the J-integral of the crack in the 316L region, which has a promoting effect when the crack is in the SA508 zone and weld metal. It provides a new idea for analyzing driving force at the crack tip and safety evaluation of DMWJs in PWRs.

scholarly journals Application of J2 Integral Method in Calculating Complicated Stress Intensity Factors on Three-dimensional Components

2021 ◽  
Vol 293 ◽  
pp. 02012
Author(s):  
Long. Li ◽  
Yousheng. Deng ◽  
Liqing Meng ◽  
Lingtao Li ◽  
Yunfang Zheng
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Integral Method ◽  
Three Dimensional ◽  
Crack Tip ◽  
Stress Fields ◽  
Experimental Result ◽  
Intensity Factors ◽  
Corner Crack ◽  
Crack Tips

In this paper, a technique to determine complicated stress intensity factors on three-dimensional components, which based on the conservation law and the elementary mechanics is proposed, it only needs the geometric relationship between multiple singular stress fields from the crack section, and obtaind the relationship between the stress at different crack tips. In the expression of the stress intensity factor K, K is proportional to the stress σ at the crack tip, and we can get the supplementary equation of between different stress fields K according to the ratio of the stress at the crack tip, then use the J-integral method to calculate the stress intensity factors of different stress fields. In order to verify the feasibility of this method, a cracked R-fluted shells model was constructed. Under the action of the bending moment, the corner crack propagation is simulated through the reserved corner crack, and two crack tips with different stress fields are generated during the simulation. The experimental result indicates that the proposed method is effective for cracked R-fluted shells. It is also shown that the method has universal applicability for solving complex stress intensity factors on three-dimensional components.

Simple Calculations of J-Integral for Through-Wall Crack in Welded Pipes Based on Failure Assessment Diagram

2019 ◽  
Author(s):  
Jun-Geun Park ◽  
Da-Som Jeon ◽  
Nam-Su Huh ◽  
Sang-Min Lee ◽  
Ye-Ji Kim
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Weld Zone ◽  
Limit Load ◽  
J Integral ◽  
Plastic Limit ◽  
Scaling Factors ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Plastic Limit Load

Abstract In the present study, simple J-integral estimations of welded pipes with a circumferential through-wall crack (TWC) in weld zone were proposed based on the failure assessment diagram (FAD) concept using scaling factor that is defined as a ratio of plastic limit load of welded pipe to that of base metal pipe. For this purpose, the detailed 3-dimensional (3-D) finite element (FE) limit analyses for welded pipes with a circumferential TWC have been systematically carried out considering various thickness of pipe, circumferential crack lengths, strength mismatches between base and weld metal, widths of weldment and locations of TWC (weld center and interface between the weld metal and the base metal). As for loading conditions, axial tension and global bending were considered in the FE analyses. Based on the present FE results, numerical expressions on scaling factors representing the ratio of plastic limit loads of welded pipes to those of base metal pipes were derived. Finally, the new FAD-based J-estimations based on option 1 concept was proposed to predict J-integrals of welded pipes incorporating the present scaling factors, i.e. ratio of plastic limit load. Moreover, the proposed J estimations were validated by comparing with FE results using actual properties.

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