Crack Propagation Simulation: A Local Deformation-Based Mesh Mapping Method for Crack Modeling and a Direct Method for Residual Stress Representation in Welds

2011 ◽  
Author(s):  
Heqin Xu ◽  
Samer Mahmoud ◽  
Ashok Nana ◽  
Doug Killian
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Crack Front ◽  
Direct Method ◽  
Local Deformation ◽  
Front Shape ◽  
A Direct Method ◽  
Mesh Mapping

Cracks found in a nuclear power plant reactor coolant system (RCS), such as primary water stress corrosion cracking (PWSCC) and intergranular stress corrosion cracking (IGSCC), usually have natural crack front shapes that can be very different from the idealized semi-elliptical or rectangular shapes considered in engineering handbooks and other analytical solutions based on limited shapes. Simplifications towards semi-elliptical shape or rectangular shape may potentially introduce unnecessary conservatism when the simplified shape has to contain the actual crack shape. On the other hand, it is very time-consuming to create a three-dimensional (3D) finite element (FE) model to simulate crack propagation in a natural shape using existing public-domain software like ABAQUS or ANSYS. In this study, a local deformation-based mesh-mapping (LDMM) method is proposed to model cracks with a natural front shape in any 3D structures. This methodology is first applied to model circumferential surface cracks with a natural crack front shape in the cross-sectional plane of a cylinder. The proposed new method can be applied to simulate both shallow and deep cracks. Also discussed in this paper is a direct method to reproduce welding residual stresses in the crack model using temperature fields combined with other sustained loads to predict crack propagations. With this novel LDMM method, natural crack fronts and non-planar crack faces can be easily modeled. The proposed new method can be used to generate a high-quality finite element model that can be used for both linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) analyses. The study case illustrates that the proposed LDMM method is easy to implement and more efficient than the existing commercial software.

Strategies for Treating Weld Residual Stresses in Probabilistic Fracture Mechanics Codes

2011 ◽  
Author(s):  
Frederick W. Brust ◽  
R. E. Kurth ◽  
D. J. Shim ◽  
David Rudland
Keyword(s):  
Fracture Mechanics ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Degradation Mechanism ◽  
Welding Process ◽  
Corrosion Cracking ◽  
Uncertainty Sources

Risk based treatment of degradation and fracture in nuclear power plants has emerged as an important topic in recent years. One degradation mechanism of concern is stress corrosion cracking. Stress corrosion cracking is strongly driven by the weld residual stresses (WRS) which develop in nozzles and piping from the welding process. The weld residual stresses can have a large uncertainty associated with them. This uncertainty is caused by many sources including material property variations of base and welds metal, weld sequencing, weld repairs, weld process method, and heat inputs. Moreover, often mitigation procedures are used to correct a problem in an existing plant, which also leads to uncertainty in the WRS fields. The WRS fields are often input to probabilistic codes from weld modeling analyses. Thus another source of uncertainty is represented by the accuracy of the predictions compared with a limited set of measurements. Within the framework of a probabilistic degradation and fracture mechanics code these uncertainties must all be accounted for properly. Here we summarize several possibilities for properly accounting for the uncertainty inherent in the WRS fields. Several examples are shown which illustrate ranges where these treatments work well and ranges where improvement is needed. In addition, we propose a new method for consideration. This method consists of including the uncertainty sources within the WRS fields and tabulating them within tables which are then sampled during the probabilistic realization. Several variations of this process are also discussed. Several examples illustrating the procedures are presented.

Stress Corrosion Cracking Behavior of Uranium Alloys

CORROSION ◽  
1974 ◽  
Vol 30 (5) ◽  
pp. 181-189 ◽  
Author(s):  
W. F. CZYRKLIS ◽  
M. LEVY
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Threshold Stress ◽  
Crack Extension ◽  
Corrosion Cracking ◽  
Nacl Solution ◽  
Cracking Behavior ◽  
Linear Elastic ◽  
Elastic Fracture

Abstract The stress corrosion cracking (SCC) behavior of U-3/4% Ti, and uranium alloys 3/4% Quad, 1% Quad, and 1% Quint have been studied utilizing a linear elastic fracture mechanics approach. The threshold stress intensities for stress corrosion crack propagation for these alloys have been determined in distilled H2O and NaCl solutions containing 50 ppm Cl− and 21,000 ppm Cl−. All of the alloys studied may be classified as very susceptible to SCC in aqueous solutions since they exhibit SCC in distilled H2O (<1 ppm Cl−) and have low KIscc values in NaCl solutions. Crack extension in all of the alloys in all environments was transgranular and failure occurred by brittle quasicleavage fracture in NaCl solution.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2008 ◽  
Author(s):  
Gang Ma ◽  
Xiang Ling
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress up to 325.9MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 hours. In contrast, treated specimens with different coverage were tested for 1000 hours without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

Probabilistic Fracture Mechanics Benchmarking Study Involving the xLPR and PASCAL-SP Codes: Analysis by PASCAL-SP

2020 ◽  
Author(s):  
Akihiro Mano ◽  
Jinya Katsuyama ◽  
Yinsheng Li
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Corrosion Cracking ◽  
Energy Agency ◽  
Pressurized Water ◽  
Water Reactor ◽  
Probabilistic Fracture Mechanics

Abstract A probabilistic fracture mechanics (PFM) analysis code, PASCAL-SP, has been developed by Japan Atomic Energy Agency (JAEA) to evaluate the failure probability of piping within nuclear power plants considering aged-related degradations such as stress corrosion cracking and fatigue for both pressurized water reactor and boiling water reactor environments. To strengthen the applicability of PASCAL-SP, a benchmarking study is being performed with a PFM analysis code, xLPR, which has been developed by U.S.NRC in collaboration with EPRI. In this benchmarking study, deterministic and probabilistic analyses are undertaken on primary water stress corrosion cracking using the common analysis conditions. A deterministic analysis on the weld residual stress distributions is also considered. These analyses are carried out by U.S.NRC and JAEA independently using their own codes. Currently, the deterministic analyses by both xLPR and PASCAL-SP codes have been finished and probabilistic analyses are underway. This paper presents the details of conditions and comparisons of the results between the two aforementioned codes for the deterministic analyses. Both codes were found to provide almost the same results including the values of stress intensity factor. The conditions and results of the probabilistic analysis obtained from PASCAL-SP are also discussed.

Characterization of microstructure and local deformation in 316NG weld heat-affected zone and stress corrosion cracking in high temperature water

2011 ◽  
Vol 53 (5) ◽  
pp. 1916-1932 ◽  
Author(s):  
Zhanpeng Lu ◽  
Tetsuo Shoji ◽  
Fanjiang Meng ◽  
He Xue ◽  
Yubing Qiu ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Heat Affected Zone ◽  
Local Deformation ◽  
Corrosion Cracking ◽  
High Temperature Water ◽  
Temperature Water ◽  
Weld Heat

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Xiang Ling ◽  
Gang Ma
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress in access of 300 MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using the finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 h. In contrast, treated specimens with different impact duration were tested for 1000 h without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

‘Fracture Mechanics and Stress Corrosion Cracking’

1972 ◽  
Vol 7 (4) ◽  
pp. 189-191 ◽  
Author(s):  
J. M. West ◽  
I. M. Austen ◽  
C. Tyzack
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking
Sign in / Sign up

Export Citation Format

Share Document