Determination of the crack propagation energy in impact bending of coated materials

1978 ◽  
Vol 10 (7) ◽  
pp. 796-798
Author(s):  
B. M. Fishtein ◽  
A. Yu. Kem
Keyword(s):  
Crack Propagation ◽  
Coated Materials ◽  
Impact Bending

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 Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

2020 ◽  
Author(s):  
Frank Liebold ◽  
Ali A. Heravi ◽  
Oliver Mosig ◽  
Manfred Curbach ◽  
Viktor Mechtcherine ◽  
...  
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Vector Fields ◽  
Displacement Vector ◽  
Image Sequence ◽  
High Speed Camera ◽  
Sequence Processing ◽  
Image Sequence Processing ◽  
Propagation Velocities

The determination of crack propagation velocities can provide valuable information for a better understanding of damage processes of concrete. The spatio-temporal analysis of crack patterns developing at a speed of several hundred meters per second is a rather challenging task. In the paper, a photogrammetric procedure for the determination of crack propagation velocities in concrete specimens using high-speed camera image sequences is presented. A cascaded image sequence processing which starts with the computation of displacement vector fields for a dense pattern of points on the specimen’s surface between consecutive time steps of the image sequence chain has been developed. These surface points are triangulated into a mesh, and as representations of cracks, discontinuities in the displacement vector fields are found by a deformation analysis applied to all triangles of the mesh. Connected components of the deformed triangles are computed using region-growing techniques. Then, the crack tips are determined using principal component analysis. The tips are tracked in the image sequence and the velocities between the time stamps of the images are derived. A major advantage of this method as compared to established techniques is in the fact of its allowing for spatio-temporally resolved, full-field measurements rather than point-wise measurements and that information on crack width can be obtained simultaneously. To validate the experimentation, the authors processed image sequences of tests on four compact-tension specimens performed on a split-Hopkinson tension bar. The images were taken by a high-speed camera at a frame rate of 160,000 images per second. By applying to these datasets the image sequence processing procedure as developed, crack propagation velocities of about 800 m/s were determined with a precision in the order of 50 m/s.

Study of Influence of Residual Stresses on Crack Propagation in Particulate Ceramic Composites

2016 ◽  
Vol 258 ◽  
pp. 178-181 ◽  
Author(s):  
Zdeněk Majer ◽  
Luboš Náhlík ◽  
Kateřina Štegnerová ◽  
Pavel Hutař ◽  
Raúl Bermejo
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Element Model ◽  
Ceramic Composites ◽  
Particulate Composites ◽  
Micro Cracks ◽  
Dimensional Finite Element ◽  
Density Factor ◽  
Energy Density Factor

The aim of the present work is to analyze the influence of residual stresses in the particulate ceramic composite on the crack propagation. The crack propagation direction was estimated using Sih’s criterion based on the strain energy density factor. A two-dimensional finite element model was developed for determination of crack path. The residual stresses resulting from the mismatch of coefficients of thermal expansion during the fabrication process of the composite were implemented to the computational model. The effect of the particles shape on the crack propagation was investigated. Conclusions of this paper can contribute to a better understanding of the propagation of micro-cracks in particulate composites in the field of residual stresses.

Experimental and theoretical fatigue-crack propagation lives of variously notched plates

1974 ◽  
Vol 9 (2) ◽  
pp. 61-66 ◽  
Author(s):  
R A Smith ◽  
K Jerram ◽  
K J Miller
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Finite Element Analyses ◽  
Intensity Factors ◽  
Complex Profile ◽  
Propagation Law ◽  
Theoretical Predictions ◽  
Life Predictions ◽  
Theoretical Results

The fatigue lives of variously notched plates have been determined theoretically and experimentally. Theoretical predictions of fatigue lives involved the determination of stress-intensity factors from finite-element analyses. By invoking a crack propagation law, fatigue-life predictions were made for four specimens. Fatigue experiments were conducted on four notched plates subjected to end load plus bending. Comparison with theoretical results shows that the experimental lives were greater by factors of 1.30 to 1.54. These results are most satisfactory since (1) a safe prediction of fatigue life has been made for a complex profile subjected to non-simple loading conditions, and (2) a theoretical elastic analysis has sufficed for a situation involving plastic strains.

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