Finite element simulation of stress intensity factors in elastic-plastic crack growth

2006 ◽  
Vol 7 (8) ◽  
pp. 1336-1342 ◽  
Author(s):  
Abdulnaser M. Alshoaibi ◽  
Ahmad Kamal Ariffin
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Finite Element Simulation ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Elastic Plastic ◽  
Element Simulation

Stress Intensity Factors and Weight Functions for Longitudinal Semi-Elliptical Surface Cracks Inside Thick-Walled Cylinders Using Highly-Refined Finite-Element Models

2010 ◽  
Author(s):  
Adam R. Hinkle ◽  
James E. Holliday ◽  
David P. Jones
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Weight Functions ◽  
Finite Element Models ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Surface Flaws ◽  
Field Singularity

Fracture mechanics and fatigue crack-growth analysis rely heavily upon accurate values of stress intensity factors. They provide a convenient, single-parameter description to characterize the amplitude of the stress-field singularity at the crack tip, and are used to correlate brittle fracture and crack growth in pressure vessel and piping applications. Mode-I stress intensity factors that have been obtained for longitudinal semi-elliptical surface flaws on the inside of thick-walled cylinders using highly-refined finite element models are investigated. Using these results, weight function solutions are constructed and selected geometries are validated.

scholarly journals Three- Dimensional Simulation of Crack Propagation using Finite Element Method

2019 ◽  
Vol 9 (2) ◽  
pp. 892-897 ◽  
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Crack Path ◽  
Three Dimensional ◽  
Life Time ◽  
Intensity Factors ◽  
Growth Step ◽  
Finite Element Software

The 3D finite element software ANSYS Workbench software has been employed for simulation of engineering geometries which are containing a pre-cracks and holes. The new feature in this software is using the smart crack growth procedure and the mesh smoothing technique which provides an adaptive and smooth mesh around the crack path as well as the higher stresses area. Under the assumption of LEFM, the stress intensity factors was used as a crack growth criterion which provided as indicators of failure compared to the fracture toughness or threshold stress intensity factors (SIFs) in both static and dynamic loading respectively. The stress intensity factors were calculated for every crack growth step and the fatigue life time was predicted according to the number of cycles. The effect of the nominal notch position of the crack was illustrated. Simulations performed with Ansys show an identical crack path on structures that is in line with that of the experimental and numerical results performed by other researchers.

Modeling Crack Growth in Weld Residual Stress Fields Using the Finite Element Alternating Method

2011 ◽  
Author(s):  
F. W. Brust ◽  
T. Zhang ◽  
D.-J. Shim ◽  
G. Wilkowski ◽  
D. Rudland
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Corrosion Cracking ◽  
Multiple Cracks ◽  
Intensity Factors ◽  
Pressurized Water ◽  
Alternating Method

Flaw indications have been found in some nozzle to stainless steel piping dissimilar metal (DM) welds and reactor pressure vessel heads (RPVH) in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe) using Alloy 182/82 weld metal. The welds may become susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. The weld residual stresses (WRS) induced by the welds are a main driver of PWSCC. Modeling the growth of these cracks in these WRS fields until leakage occurs is important for safety assessments. Currently, the prediction of PWSCC crack growth is based on the stress intensity factors at the crack tips. Several methods for modeling the crack growth through these WRS fields are possible, including using analytical, natural crack growth using finite element methods, and using the finite element alternating method. In this paper, finite element alternating method (FEAM) is used for calculating stress intensity factors and modeling the growth. First the FEAM method for growing cracks is presented. Next, several examples of modeling growth through control rod drive mechanism (CRDM) heads are presented. Finally, a short example examining multiple cracks in CRDM heads is presented. For many problems the FEAM approach for rapidly modeling crack growth is quite convenient, especially for difficult to mesh crack geometries.

scholarly journals Fracture resistance parameters for the compressor disk imitation model

2020 ◽  
pp. 98-107
Author(s):  
M. M Yakovlev ◽  
R. R Yarullin ◽  
V. N Shlyannikov
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Fracture Resistance ◽  
Fatigue Cracks ◽  
Testing Machine ◽  
Intensity Factors ◽  
Imitation Model ◽  
Compressor Disk

This paper presents a calculation and experimental technique for determining stress intensity factors in an imitation model of a titanium alloy disk. We studied a low-pressure compressor disk of a gas turbine engine (GTE) D-36. During operations, there occur fatigue cracks initiated and developed in the slot fillet under the blade at the place of transition of the bottom to the lateral surface of the inter-groove projection, which lead to a separation of the disk’s part within its rim. The mixed-mode crack growth occured in the compressor disks. Based on the principles of imitation modeling, the geometry and loading condition of the imitation model of the compressor disk was developed. The fatigue test of the imitation model was carried out with a frequency of 5 Hz, at room temperature and with stress ratio Rc = 0.1, by means of a biaxial testing machine. The crack growth was monitored using an optical microscope. The criterion for failure was the condition for reaching a growing crack of the compensation hole. During the test, the positions and sizes of the crack fronts were fixed, which are the basis for the numerical calculation of the fracture resistance parameters. In the order of the numerical studies, six three-dimensional finite element models with different positions and sizes of the crack fronts are considered. The results of the numerical calculations based on the finite element method were used to determine the distributions of elastic and plastic stress intensity factors along each crack front. We demonstrated the advantages of the calculation and experimental methods for solving the problems of interpretation and prediction of the crack growth in the rotating disks of turbomachines using the methods of fracture mechanics.

A Coupled SBFEM-FEM Approach for Evaluating Stress Intensity Factors

2013 ◽  
Vol 353-356 ◽  
pp. 3369-3377 ◽  
Author(s):  
Ming Guang Shi ◽  
Chong Ming Song ◽  
Hong Zhong ◽  
Yan Jie Xu ◽  
Chu Han Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Complex Geometry ◽  
Stress Singularity ◽  
Intensity Factors ◽  
Finite Element Software ◽  
Scaled Boundary Finite Element ◽  
Element Method

A coupled method between the Scaled Boundary Finite Element Method (SBFEM) and Finite Element Method (FEM) for evaluating the Stress Intensity Factors (SIFs) is presented and achieved on the platform of the commercial finite element software ABAQUS by using Python as the programming language. Automatic transformation of the finite elements around a singular point to a scaled boundary finite element subdomain is realized. This method combines the high accuracy of the SBFEM in computing the SIFs with the ability to handle material nonlinearity as well as powerful mesh generation and post processing ability of commercial FEM software. The validity and accuracy of the method is verified by analysis of several benchmark problems. The coupled algorithm shows a good converging performance, and with minimum additional treatment can be able to handle more problems that cannot be solved by either SBFEM or FEM itself. For fracture problems, it proposes an efficient way to represent stress singularity for problems with complex geometry, loading condition or certain nonlinearity.

Finite Element Simulation of Stable Fatigue Crack Growth Using Critical CTOD Determined by Preliminary Finite Element Analysis

2014 ◽  
Vol 891-892 ◽  
pp. 1675-1680
Author(s):  
Seok Jae Chu ◽  
Cong Hao Liu
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Finite Element Simulation ◽  
Crack Growth ◽  
Crack Tip ◽  
Stress Intensity Factor Range ◽  
Crack Tip Opening Displacement ◽  
Element Analysis ◽  
Element Simulation

Finite element simulation of stable fatigue crack growth using critical crack tip opening displacement (CTOD) was done. In the preliminary finite element simulation without crack growth, the critical CTOD was determined by monitoring the ratio between the displacement increments at the nodes above the crack tip and behind the crack tip in the neighborhood of the crack tip. The critical CTOD was determined as the vertical displacement at the node on the crack surface just behind the crack tip at the maximum ratio. In the main finite element simulation with crack growth, the crack growth rate with respect to the effective stress intensity factor range considering crack closure yielded more consistent result. The exponents m in the Paris law were determined.

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