Issues in Welding Residual Stress Model in Fitness for Service Assessment of Crack-Like Defect in Weld Area

2015 ◽  
Author(s):  
Jeong K. (J. K.) Hong ◽  
Richard P. Brodzinski ◽  
Pedro M. Vargas ◽  
H. Chong Rhee ◽  
K-John Young ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Driving Force ◽  
Welding Residual Stress ◽  
Element Analysis ◽  
Crack Driving Force ◽  
Defect Assessment ◽  
Technical Issues ◽  
Weld Area ◽  
Force Calculation

Current Industry Code and Standard (ICS) Fitness for Service Assessment (FFSA) procedures for crack-like defect in weld area tend to impose high level of conservatism. In addition to the necessity for using conservative Welding Residual Stress (WRS) model due to the uncertainty inherent in the WRS estimation, using the original WRS regardless of crack depth in the crack driving force calculation, like the applied operating load, is the primary reason for this solution conservatism. In addition, current ICS weld area defect assessment procedures involve ambiguities in boundary condition effects on WRS models, as well as in the fracture mode of weld area crack being treated in the context of opening mode only, even though there is no weld area geometric symmetry essential for precluding fracture modes other than mode I. To clarify these technical issues in the ICS FFSA practices rigorous numerical simulation analyses of welding process and crack growth following joint fabrication have been performed, using the finite element analysis procedure. A crack driving force calculation procedure for weld area cracks, which was developed to quantify the crack extension effects on WRS for growing crack, was used for the finite element crack growth simulation analyses. The rigorous finite element analysis results for boundary condition effects on WRS, the fracture mode of weld toe crack, and crack growth effects on crack driving force parameters caused by WRS are compared with those of current ICS solutions. These comparisons demonstrate the need for an improvement of the current ICS FFSA procedures for weld area crack-like defects. The primary objective of the present paper is to motivate the industry to improve ICS FFSA procedures by clarifying these ambiguous technical issues in weld area crack-like defect assessment parameters, as well as considering crack extension effects on WRS properly in calculating the crack driving force of growing crack to reduce undue conservatism in FFSA.

Crack Extension Effects on Welding Residual Stress in Fitness for Service Assessment

2013 ◽  
Author(s):  
H. Chong Rhee
Keyword(s):  
Residual Stress ◽  
Driving Force ◽  
Crack Extension ◽  
Welding Residual Stress ◽  
Stress Release ◽  
Crack Driving Force ◽  
Defect Assessment ◽  
Standard Procedures ◽  
Growing Crack ◽  
Force Calculation

In the fitness for service assessment of a welded component with crack like defect, the current industry practices treat the welding residual stress in the same way as the applied operating stress in calculating the crack driving force. Although a growing crack should release the welding residual stress, the same initial residual stress is used in calculating the stress intensity factor solution regardless of the crack depth. Such procedures should result in too conservative solutions, since the crack extension effect on welding residual stress release is ignored in the crack driving force calculation. The present paper discusses the current state of the industry code and standard procedures for welded component defect assessment with a practical example problem solution, along with detailed discussions on the effects of crack growth on the welding residual stress. The objective of the paper is to motivate the industry to improve the code and standard procedures for the weld defect assessment. Also it presents a comparison of crack-like defect assessment results between the current industry procedure and one of newly proposed crack driving force calculation procedures for a crack growing in welding residual stress field, considering the welding residual stress release effects of growing crack. Recommendations for improving the industry code and standard procedures for the weld area defect assessment are provided based the investigation.

Crack Extension Effects on Welding Residual Stress in Fitness for Service Assessment of Crack-Like Defect in Weld

2016 ◽  
Author(s):  
Jeong K. Hong
Keyword(s):  
Residual Stress ◽  
3D Models ◽  
Crack Size ◽  
Welding Residual Stress ◽  
Welding Parameters ◽  
Element Analysis ◽  
Defect Assessment ◽  
Technical Issues ◽  
Model Geometry ◽  
2D And 3D

The current industry code and standard fitness-for-service assessment (ICS FFSA) procedures ignore the release of the welding residual stress (WRS) in defect assessment of a crack growing in a WRS field. Doing so can result in overly restrictive results in the ICS FFSA of an engineering component. The current ICS FFSA procedures have produced compendiums of WRS distributions and stress intensity factor (SIF) solutions that are characterized by the joint geometry and welding parameters. It is also known that these distributions are based on extensive numerical analyses and provide upper bound estimates; therefore, these types of solutions do not necessarily satisfy the self-equilibrating state. In this investigation, through-wall WRS distributions from the literature data, including measurements and finite element analysis (FEA) results for girth welded pipes, are compared to the representative ICS FFSA WRS procedures. Also, the WRS and SIF solutions using the proposed procedure are compared to those using the ICS FFSA procedures employing 2D and 3D models. From the investigation, it is observed that the ICS FFSA procedures show discrepancies for certain conditions and the levels of conservatism are dependent on the model geometry, boundary constraint condition, crack size, and crack shape. For some cases, the estimations provided from the ICS FFSA procedures are not conservative compared to the reference solutions from literatures and FEA simulations. As a continuous study of the previous investigation [OMAE 2015-41319], the objective of the present paper is to motivate the industry to improve ICS FFSA procedures by clarifying the ambiguous technical issues of crack-like defect assessment in weld regions.

scholarly journals A Finite Element Analysis of a Crack Penetrating or Deflecting into an Interface in a Thin Laminate

2006 ◽  
Vol 312 ◽  
pp. 173-178 ◽  
Author(s):  
Sharon Kao-Walter ◽  
Per Ståhle ◽  
Shao Hua Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Driving Force ◽  
Crack Tip ◽  
Element Analysis ◽  
Linear Fracture ◽  
Finite Element Calculations ◽  
Straight Ahead

The crack tip driving force of a crack growing from a pre-crack that is perpendicular to and terminating at an interface between two materials is investigated using a linear fracture mechanics theory. The analysis is performed both for a crack penetrating the interface, growing straight ahead, and for a crack deflecting into the interface. The results from finite element calculations are compared with asymptotic solutions for infinitesimally small crack extensions. The solution is found to be accurate even for fairly large amounts of crack growth. Further, by comparing the crack tip driving force of the deflected crack with that of the penetrating crack, it is shown how to control the path of the crack by choosing the adhesion of the interface relative to the material toughness.

Assessment of Fully Plastic J and C*-Integral Solutions for Application to Elastic-Plastic Fracture and Creep Crack Growth

1993 ◽  
Vol 115 (3) ◽  
pp. 228-234 ◽  
Author(s):  
D. R. Lee ◽  
J. M. Bloom
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Driving Force ◽  
Creep Crack Growth ◽  
J Integral ◽  
Finite Element Program ◽  
Hardening Material ◽  
Crack Driving Force ◽  
Elastic Plastic ◽  
Creep Crack

A critical part of the assessment of defects in power plant components, both fossil and nuclear, is the knowledge of the crack driving force (K1, J, or C*). While the determination of the crack driving force is possible using finite element analyses, crack growth analyses using finite element methods can be expensive. Based on work by Il’yushin, it has been shown that for a power law hardening material, the fully plastic portion of the J-integral (or the C*-integral) is directly related to an h1 calibration function. The value of h1 is a function of the geometry and hardening exponent. The finite element program ABAQUS was used to evaluate the fully plastic J-integral and determine the h1 functions for various geometries. The Ramberg-Osgood deformation theory plasticity model, which may be used with the J-integral evaluation capability, allows the evaluation of fully plastic J solutions. Once it was established that the grid used to generate the h1 functions was adequate (based on the more recent work of Shih and Goan), additional runs were made of other configurations given in the EPRI Elastic-Plastic Fracture Handbook. Differences as great as 55 percent were found when compared to results given in the Handbook (single-edge crack plate under tension and plane stress with a/b = 0.5). Effects of errors in h1 on predicted failure load and creep crack growth are discussed.

A Finite Element Study of the Effect of Crystal Orientation and Misalignment on the Crack Driving Force in a Single-Crystal Superalloy

2016 ◽  
Author(s):  
Christian Busse ◽  
Jordi Loureiro Homs ◽  
David Gustafsson ◽  
Frans Palmert ◽  
Björn Sjödin ◽  
...  
Keyword(s):  
Finite Element ◽  
Single Crystal ◽  
Crack Growth ◽  
Driving Force ◽  
Crystal Orientation ◽  
Plastic Anisotropy ◽  
Casting Process ◽  
Material Model ◽  
Crack Growth Behavior ◽  
Crack Driving Force

The elastic and plastic anisotropy of the single-crystalmaterials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10° misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

scholarly journals Crystallographic crack propagation rate in single-crystal nickelbase superalloys

2018 ◽  
Vol 165 ◽  
pp. 13012
Author(s):  
Christian Busse ◽  
Frans Palmert ◽  
Paul Wawrzynek ◽  
Björn Sjödin ◽  
David Gustafsson ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Driving Force ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Mode I ◽  
Force Parameter ◽  
Intensity Factors ◽  
Crack Driving Force

Single-crystal nickel-base superalloys are often used in the hot sections of gas turbines due to their good mechanical properties at high temperatures such as enhanced creep resistance. However, the anisotropic material properties of these materials bring many difficulties in terms of modelling and crack growth prediction. Cracks tend to switch cracking mode from Mode I cracking to crystallographic cracking. Crystallographic crack growth is often associated with a decrease in crack propagation life compared to Mode I cracking and this must be taken into account for reliable component lifing. In this paper a method to evaluate the crystallographic crack propagation rate related to a crystallographic crack driving force parameter is presented. The crystallographic crack growth rate is determined by an evaluation of heat tints on the fracture surface of a specimen subjected to fatigue loading. The complicated crack geometry including two crystallographic crack fronts is modelled in a three dimensional finite element context. The crack driving force parameter is determined by calculating anisotropic stress intensity factors along the two crystallographic crack fronts by finite-element simulations and post-processing the data in a fracture mechanics tool that resolves the stress intensity factors on the crystallographic slip planes in the slip directions. The evaluated crack propagation rate shows a good correlation for both considered crystallographic cracks fronts.

Analysis of magnetic force and dynamic characteristic for non-contact permanent magnet linear drive device

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1337-1345
Author(s):  
Chuan Zhao ◽  
Feng Sun ◽  
Junjie Jin ◽  
Mingwei Bo ◽  
Fangchao Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Permanent Magnet ◽  
Dynamic Characteristic ◽  
Driving Force ◽  
Magnetic Circuit ◽  
Response Speed ◽  
Computation Method ◽  
Element Analysis ◽  
Element Simulation ◽  
The Relationship

This paper proposes a computation method using the equivalent magnetic circuit to analyze the driving force for the non-contact permanent magnet linear drive system. In this device, the magnetic driving force is related to the rotation angle of driving wheels. The relationship is verified by finite element analysis and measuring experiments. The result of finite element simulation is in good agreement with the model established by the equivalent magnetic circuit. Then experiments of displacement control are carried out to test the dynamic characteristic of this system. The controller of the system adopts the combination control of displacement and angle. The results indicate that the system has good performance in steady-state error and response speed, while the maximum overshoot needs to be reduced.

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