scholarly journals A Numerical Approach to Analyze Detail Mechanical Characteristic at the Crack Tip of SCC in Dissimilar Metal Welded Joints

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
He Xue ◽  
Yuman Sun ◽  
Shun Zhang ◽  
Rehmat Bashir ◽  
Youjun Zhao ◽  
...  
Keyword(s):  
Mechanical Characteristic ◽  
Welded Joints ◽  
Material Properties ◽  
Crack Tip ◽  
Heterogeneous Material ◽  
Material Model ◽  
Numerical Approach ◽  
Interface Zone ◽  
Factors Affecting ◽  
Dissimilar Metal

The mechanical characteristic at the crack tip is one of the main factors affecting the stress corrosion cracking (SCC) in dissimilar metal welded joints (DMWJs). In this research, to evaluate the effect of heterogeneous material properties on the mechanical characteristic at the crack tip of DMWJs accurately, a heterogeneous material model of the SA508 Cl.3-Alloy 52M DMWJ was established based on USDFLD subroutine in ABAQUS. The comparison of the traditional “Sandwich” material model with the heterogeneous material properties, stress-strain conditions, and the plastic zone around the crack tip at the interference zone has been analyzed by the finite element method (FEM). The results indicated that the heterogeneous material model could characterize the mechanical properties of the SA508 Cl.3-Alloy 52M DMWJs accurately. In addition, the crack at the interface zone between materials will deflect along with the weld metal in two material models.

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 Compilation and Application of UMAT for Mechanical Properties of Heterogeneous Metal Welded Joints in Nuclear Power Materials

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
He Xue ◽  
Yueqi Bi ◽  
Shuai Wang ◽  
Jianlong Zhang ◽  
Siyu Gou
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Welded Joints ◽  
Constitutive Equations ◽  
Crack Tip ◽  
Material Model ◽  
Material Interface ◽  
Continuous Transition ◽  
Dissimilar Metal ◽  
Crack Tip Stress

For the problem of mechanical properties of heterogeneous dissimilar metal welded joints, when analyzed by the finite element method, it is usually simplified into a “sandwich” material structure model. However, the mechanical properties of materials in different regions of the “sandwich” material mechanics model are different, and there will be mutations at the material interface. In order to accurately describe the mechanical properties of welded joints, the constitutive equations of dissimilar metal welded joint materials were compiled, and the constitutive equations of inhomogeneous materials whose material mechanical properties were continuously changed with space coordinates were established. The ABAQUS software was used to establish the “sandwich” model and the continuous transition model. The model is used to compare and analyze the crack tip stress distribution of different yield strength mismatch coefficients. The results show that the continuous transition material model eliminates the mutation of the “sandwich” model at the material interface and achieves the continuous change of the mechanical properties of the material. For the longitudinal crack, under the influence of different mismatch coefficients, the crack tip stress field of the transitional material model is deflected toward the low yield strength side. The compilation of constitutive equations for continuous transition materials of dissimilar metal welded joints provides a basis for the safety evaluation of dissimilar metal welded joints.

scholarly journals Multivariate Analysis to Relate CTOD Values with Material Properties in Steel Welded Joints for the Offshore Wind Power Industry

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 4001 ◽  
Author(s):  
Presno Vélez ◽  
Sánchez ◽  
Menéndez Fernández ◽  
Fernández Muñiz
Keyword(s):  
Multivariate Analysis ◽  
Welded Joints ◽  
Material Properties ◽  
Crack Tip ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Multivariate Techniques ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Wide Range

The increasingly mechanical requirements of offshore structures have established the relevance of fracture mechanics-based quality control in welded joints. For this purpose, crack tip opening displacement (CTOD) at a given distance from the crack tip has been considered one of the most suited parameters for modeling and control of crack growth, and it is broadly used at the industrial level. We have modeled, through multivariate analysis techniques, the relationships among CTOD values and other material properties (such as hardness, chemical composition, toughness, and microstructural morphology) in high-thickness offshore steel welded joints. In order to create this model, hundreds of tests were done on 72 real samples, which were welded with a wide range of real industrial parameters. The obtained results were processed and evaluated with different multivariate techniques, and we established the significance of all the chosen explanatory variables and the good predictive capability of the CTOD tests within the limits of the experimental variation. By establishing the use of this model, significant savings can be achieved in the manufacturing of wind generators, as CTOD tests are more expensive and complex than the proposed alternatives. Additionally, this model allows for some technical conclusions.

scholarly journals A numerical approach for the modelling of forming limits in hot incremental forming of AZ31 magnesium alloy

2021 ◽  
Author(s):  
Davide Campanella ◽  
Gianluca Buffa ◽  
Ernesto Lo Valvo ◽  
Livan Fratini
Keyword(s):  
Room Temperature ◽  
Incremental Forming ◽  
Material Model ◽  
Numerical Approach ◽  
Forming Limit ◽  
Material Strength ◽  
Wall Angle ◽  
Analytical Expression ◽  
The Poor ◽  
Specific Material

AbstractMagnesium alloys, because of their good specific material strength, can be considered attractive by different industry fields, as the aerospace and the automotive one. However, their use is limited by the poor formability at room temperature. In this research, a numerical approach is proposed in order to determine an analytical expression of material formability in hot incremental forming processes. The numerical model was developed using the commercial software ABAQUS/Explicit. The Johnson-Cook material model was used, and the model was validated through experimental measurements carried out using the ARAMIS system. Different geometries were considered with temperature varying in a range of 25–400 °C and wall angle in a range of 35–60°. An analytical expression of the fracture forming limit, as a function of temperature, was established and finally tested with a different geometry in order to assess the validity.

scholarly journals Characterization of Mechanical Heterogeneity in Dissimilar Metal Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4145
Author(s):  
He Xue ◽  
Zheng Wang ◽  
Shuai Wang ◽  
Jinxuan He ◽  
Hongliang Yang
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Welded Joints ◽  
Structural Integrity ◽  
Material Interfaces ◽  
Mechanical Heterogeneity ◽  
Finite Element Software ◽  
Dissimilar Metal ◽  
Stress Changes

Dissimilar metal welded joints (DMWJs) possess significant localized mechanical heterogeneity. Using finite element software ABAQUS with the User-defined Material (UMAT) subroutine, this study proposed a constitutive equation that may be used to express the heterogeneous mechanical properties of the heat-affected and fusion zones at the interfaces in DMWJs. By eliminating sudden stress changes at the material interfaces, the proposed approach provides a more realistic and accurate characterization of the mechanical heterogeneity in the local regions of DMWJs than existing methods. As such, the proposed approach enables the structural integrity of DMWJs to be analyzed in greater detail.

Finite Element Analyses of Residual Stresses in Typical Welded Joints Used in Nuclear Power Plants and Comparisons With Experiments

2010 ◽  
Author(s):  
Dean Deng ◽  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Dissimilar Metal ◽  
Water Reactors

Recent discoveries of stress corrosion cracking (SCC) at nickel-based metals in pressurized water reactors (PWRs) and boiling water reactors (BWRs) have raised concerns about safety and integrity of plant components. It has been recognized that welding residual stress is an important factor causing the issue of SCC in a weldment. In this study, both numerical simulation technology and experimental method were employed to investigate the characteristics of welding residual stress distribution in several typical welded joints, which are used in nuclear power plants. These joints include a thick plate butt-welded Alloy 600 joint, a dissimilar metal J-groove set-in joint and a dissimilar metal girth-butt joint. First of all, numerical simulation technology was used to predict welding residual stresses in these three joints, and the influence of heat source model on welding residual stress was examined. Meanwhile, the influence of other thermal processes such as cladding, buttering and heat treatment on the final residual stresses in the dissimilar metal girth-butt joint was also clarified. Secondly, we also measured the residual stresses in three corresponding mock-ups. Finally, the comparisons of the simulation results and the measured data have shed light on how to effectively simulate welding residual stress in these typical joints.

scholarly journals Abstract Nonconforming Error Estimates and Application to Boundary Penalty Methods for Diffusion Equations and Time-Harmonic Maxwell’s Equations

2018 ◽  
Vol 18 (3) ◽  
pp. 451-475 ◽  
Author(s):  
Alexandre Ern ◽  
Jean-Luc Guermond
Keyword(s):  
Error Analysis ◽  
Error Estimates ◽  
Material Properties ◽  
Maxwell’S Equations ◽  
Vector Fields ◽  
Maxwell's Equations ◽  
Heterogeneous Material ◽  
Test Functions ◽  
Time Harmonic ◽  
New Formulation

AbstractWe devise a novel framework for the error analysis of finite element approximations to low-regularity solutions in nonconforming settings where the discrete trial and test spaces are not subspaces of their exact counterparts. The key is to use face-to-cell extension operators so as to give a weak meaning to the normal or tangential trace on each mesh face individually for vector fields with minimal regularity and then to prove the consistency of this new formulation by means of some recently-derived mollification operators that commute with the usual derivative operators. We illustrate the technique on Nitsche’s boundary penalty method applied to a scalar diffusion equation and to the time-harmonic Maxwell’s equations. In both cases, the error estimates are robust in the case of heterogeneous material properties. We also revisit the error analysis framework proposed by Gudi where a trimming operator is introduced to map discrete test functions into conforming test functions. This technique also gives error estimates for minimal regularity solutions, but the constants depend on the material properties through contrast factors.

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