Specimen Geometry and Extended Crack Growth Effects on J

Author(s):  
DA Davis ◽  
MG Vassilaros ◽  
JP Gudas
2021 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Doré

Abstract Most engineering components are subjected to cyclic loading in service and design against fatigue failure is often a key consideration in design. For fracture mechanics fatigue analysis, fatigue crack growth (FCG) tests are often required to determine the relevant Paris power law parameters for the material under the environment concerned. Standards allow use of different specimen geometries for FCG tests such as compact tension (CT), centre crack tension (CCT), single edge notch bend (SENB) and single edge notch tension (SENT). However, when selecting specimen geometry for fatigue crack growth rate (FCGR) testing, there is often doubt about which specimen geometry is more appropriate and whether they give similar FCGR. There is limited work to compare the FCGR between different specimen geometries. This paper first briefly introduces the guidance on FCG test specimen geometries in standards and compares the advantages and disadvantages of these specimen geometries. A comprehensive literature review is carried out to compare the FCGR data between different specimen geometries. FCGR tests are conducted on SENB, SENT and CCT specimens of C-Mn steel to investigate any effects of specimen symmetry/asymmetry and crack constraint on FCGR. Based on the literature review and test data, it is concluded that FCGR is independent of the specimen geometries examined.


1984 ◽  
Vol 55 (7) ◽  
pp. 339-343 ◽  
Author(s):  
Hans-Jürgen Kaiser ◽  
Karl Edgar Hagedorn ◽  
Oskar Pawelski

Author(s):  
L. M. S. Santos ◽  
C. Capela ◽  
F. V. Antunes ◽  
J. A. M. Ferreira ◽  
J. D. Costa ◽  
...  

Author(s):  
J. M. Treinen ◽  
Ph. P. Darcis ◽  
J. D. McColskey ◽  
R. Smith ◽  
J. Merritt

The effects of specimen geometry on the fatigue crack growth rates (FCGR) in API X65 and X100 pipeline steels were explored by use of the middle tension and compact tension specimen geometries. It was found that the specimen type has little influence on the stage II linear fatigue crack growth region for these steels. Furthermore, the FCGR behavior in the longitudinal and transverse directions was found to be nearly identical for both steels. Also of interest was a comparison of the FCGR results to the BS 7910 design curves, which showed a discrepancy between the results and the standard only at low delta K levels. A finite element analysis of the compliance relationships used to predict the crack lengths during testing of both specimen types revealed that the expression for both the middle tension specimen and the compact tension specimen were found to be valid. Although the curved geometry of the middle tension specimen caused slightly different compliance results, these differences did not appear to affect the FCGR results.


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