Automatic 3-D Crack Propagation Calculations in Industrial Components: A Pure Hexahedral versus a Combined Hexahedral-Tetrahedral Approach

2007 ◽  
Vol 348-349 ◽  
pp. 45-48
Author(s):  
Guido Dhondt
Keyword(s):  
Crack Propagation ◽  
Computing Time ◽  
Propagation Direction ◽  
Hexahedral Elements ◽  
Crack Propagation Direction ◽  
Low Weight ◽  
Out Of Plane ◽  
Hexahedral Meshes ◽  
Crack Faces

In recent years, increased loading and low weight requirements have led to the need for automatic crack tracing software. At MTU a purely hexahedral code has been developed in the nineties for Mode-I applications. It has been used extensively for all kinds of components and has proven to be very flexible and reliable. Nevertheless, in transition regions between complex components curved cracks have been observed, necessitating the development of mixed-mode software. Due to the curvature of the crack faces, purely hexahedral meshes are not feasible, and therefore a mixture of hexahedral elements at the crack tip, combined with tetrahedral in the remaining structure has been selected. The intention of the present paper is to compare both methods and to point out the strength and weaknesses of each regarding accuracy, complexity, flexibility and computing time. Furthermore, difficulties arising from the out-of-plane growth of the crack such as the determination of the crack propagation direction are discussed.

scholarly journals Determination of the Crack Propagation Direction in Mixed-Mode Missions due to Cyclic Loading

2021 ◽  
Vol 11 (4) ◽  
pp. 1673
Author(s):  
Jury Rodella ◽  
Guido Dhondt ◽  
Paul Köster ◽  
Manuela Sander ◽  
Steven Piorun
Keyword(s):  
Experimental Data ◽  
Phase Shift ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Industrial Applications ◽  
Propagation Direction ◽  
Crack Propagation Direction ◽  
Angle Criterion ◽  
Large Phase

The evaluation of cyclic crack propagation due to missions with varying mixed-mode conditions is an important topic in industrial applications. This paper focuses on the determination of the resulting propagation direction. Two criteria are analyzed, the dominant step criterion and the averaged angle criterion, and compared with experimental data from tension-torsion tests with and without phase shift. The comparison shows that the dominant step criterion yields better results for small to moderate values of the phase shift. For a large phase shift of 90°, the experimental results are not very consistent, and therefore, no decisive conclusions can be drawn.

Experimental Study and Finite Element Simulation of Heat Build-Up in Rubber Compounds with Application to Fracture

2003 ◽  
Vol 76 (2) ◽  
pp. 386-405 ◽  
Author(s):  
Vladamir Kerchman ◽  
Cheng Shaw
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Numerical Models ◽  
Propagation Direction ◽  
Transient Temperature ◽  
Ir Thermography ◽  
Crack Propagation Direction ◽  
Measure Surface Temperature ◽  
Rubber Compounds ◽  
Heat Build Up

Abstract IR thermography was used to measure surface temperature profiles of cylindrical rubber specimens during cyclic compression. A linearized constitutive approach and finite element analysis were used to evaluate heat generation and associated transient temperature fields. Modeled temperatures compared well with the IR measurements. This led to extended simulation efforts on lab fracture samples. IR thermography was used to measure temperature of filled NR and filled SBR specimens during tensile fatigue cut growth tests. Temperature gradients are expected to relate to kinetics of rubber fracture and identify regions within the sample that are undergoing accelerated damage. The following cut growth issues were addressed: 1) crack propagation direction in a non-uniform stress field; 2) crack propagation direction as a function of the angle of initial cuts; 3) initiation of crack branching; and 4) catastrophic failure. The nonlinear coupled mechanical and thermal FEA was used to evaluate the energy dissipation in the non-homogeneous cyclic deformation of cracked samples. Modeled and measured surface temperatures are in good agreement. Accounting for heat build-up ahead of an advancing crack can improve numerical models that quantify fatigue cut growth behavior in rubber compounds.

Crack Propagation Analysis Procedure Using FEM Applied to the Three-Dimensional Stress Field

2005 ◽  
Author(s):  
Yukihiko Okuda ◽  
Yuuji Saito ◽  
Masayuki Asano ◽  
Masakazu Jimbo ◽  
Hiroshi Hirayama ◽  
...  
Keyword(s):  
Stress Field ◽  
Crack Propagation ◽  
Three Dimensional ◽  
Tensile Load ◽  
Analysis Procedure ◽  
Propagation Direction ◽  
Crack Shape ◽  
Weld Joints ◽  
Crack Propagation Direction ◽  
Propagation Analysis

Recently, several cracks have been found on the weld joints of Boiling Water Reactor (BWR) core shrouds during inspection. In order to ensure the continuous operation of nuclear power plants, it is necessary to assess the structural integrity of core shrouds with cracks on the weld joints. In general, a crack propagates in a complicated manner according to three-dimensional stress field and it is difficult to predict crack propagation direction and crack shape change. Usually, half ellipsoid crack shape is assumed and the propagation of the crack is calculated in the constant direction for assessment. In this study, crack propagation analysis procedure using the Finite Element Method (FEM) is developed for general shaped crack, and the procedure is verified by experiments. In this procedure, it is assumed that the crack propagates according to the maximum J-integral under three-dimensional stress fields and the re-mesh technique is used in the FEM analysis in order to calculate crack shape variation during propagation. The fatigue crack propagation tests under cyclic tensile load were performed to verify the analysis procedure. The specimens are made of a plate from 316SS and designed to generate non-uniform stress distribution on the crack front in order to observe continuous crack propagation direction change.

Study of Mode I-II Mixed Crack Propagation in Electrofusion Joint of Polyethylene Pipe

2018 ◽  
Author(s):  
Yue Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Distribution ◽  
Axial Stress ◽  
Propagation Direction ◽  
Image Correlation ◽  
J Integral ◽  
Full Field ◽  
Crack Propagation Direction ◽  
Finite Element Numerical Simulation

Electrofusion joint plays an important role in connecting polyethylene (PE) pipe. In our previous study, penetrating crack failure through the fitting with an angle of about 70° was observed, and axial stress was found to be an important factor in the crack propagation. In this paper, experiments were carried out to study the crack propagation phenomena of the electrofusion joint of PE pipe. Digital Image Correlation (DIC) method was used to measure the displacement on specimen’s surface, as well as full-field strain distribution, based on which the J-integral of the crack tip was calculated. Besides, a finite element numerical simulation was conducted, and its accuracy was verified by experimental J-integral value. Through combination of experimental observations and finite element method, the phenomenon that the angle between crack propagation direction and tube axial is about 70° is detailed analysed. By comparison and analysis of the testing results, critical J-integral value during crack propagation is determined. Furthermore, critical J-integral value of crack propagation in electrofusion joint is predicted.

Surface Cracking in Elastic-Plastic Multi-Layered Media Due to Repeated Sliding Contact

2004 ◽  
Vol 126 (4) ◽  
pp. 655-663 ◽  
Author(s):  
Z.-Q. Gong ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Layered Media ◽  
Growth Increment ◽  
Propagation Direction ◽  
Sliding Contact ◽  
Propagation Path ◽  
Surface Cracking ◽  
Crack Propagation Direction

Surface cracking in a multi-layered medium due to sliding of a rigid asperity was analyzed using linear elastic fracture mechanics and the finite element method. Overlapping of the crack faces and assumptions about the distributions of surface tractions were avoided by using special contact elements. The main objectives of this study were to obtain solutions for the tensile and shear stress intensity factor (SIF) and to determine the crack propagation path in the first layer due to repetitive sliding. The crack propagation direction was predicted based on the maximum (tensile or shear) SIF range. The effects of the crack length, sliding friction, and crack-face friction on the SIF and crack propagation direction are discussed in the context of finite element solutions. Simulation results demonstrate the effects of crack growth in the elastic surface layer on the accumulation of plastic strain in the elastic-plastic underlying layer and the significance of the crack growth increment on the propagation path. It is shown that the surface crack propagates toward the layer interface at an angle of ∼57° from the original crack plane, independent of the crack growth increment, in fair agreement with experimental observations. Based on the obtained results, a general fatigue approach for surface cracking is derived for multi-layered media subjected to repetitive sliding contact.

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