An extended compact tension specimen for fatigue crack growth and fracture testing

1996 ◽  
Vol 76 (3) ◽  
pp. R43-R48 ◽  
Author(s):  
R. S. Piascik ◽  
J. C. Newman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen ◽  
Fracture Testing

Effects of Specimen Geometry on Fatigue-Crack Growth Rates in Pipeline Steels

2008 ◽  
Author(s):  
J. M. Treinen ◽  
Ph. P. Darcis ◽  
J. D. McColskey ◽  
R. Smith ◽  
J. Merritt
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Specimen Geometry ◽  
Tension Specimen ◽  
Pipeline Steels ◽  
Crack Growth Rates

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.

scholarly journals A peridynamic damage-cumulative hybrid model for fatigue cracking

2021 ◽  
Author(s):  
Lanwen WANG ◽  
Xuanyu Sheng ◽  
Jianbin Luo
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Hybrid Model ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen

A new peridynamic fatigue damage-cumulative hybrid model is developed in this study, which is modeled by Kinetic Theory of Fracture(KTF) and Paris formula. The compact tension specimen and modified compact tension specimen are used to study the convergence of the fatigue crack growth path and fatigue life. Then constant amplitude cyclic loading and variable amplitude cyclic loading of the specimens are simulated. By comparing with the experimental results, the accuracy of the model is verified. Compared with the fatigue model that only uses KTF, the hybrid model predicts the fatigue crack growth rate more accurately. The model is based on the stress damage criterion in the fatigue crack initiation stage, which can be a basis for fatigue prediction and safety design of components in complex stress state in actual engineering.

Analysis of a main fatigue crack interaction with multiple micro-cracks/voids in a compact tension specimen repaired by stop-hole technique

2018 ◽  
Vol 53 (8) ◽  
pp. 648-662 ◽  
Author(s):  
Mohammad Malekan ◽  
Hermes Carvalho
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Growth Period ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen ◽  
Extended Finite Element ◽  
Forming Process ◽  
Micro Cracks

Fatigue is a process in engineering materials in which damage accumulates due to the fluctuating loading. One solution for a component under the fatigue process is to arrest the crack propagation before the final failure using different available retardation methods, such as drilling/stop-hole technique. In addition, structural components may also suffer from the existence of micro-cracks or voids due to their forming process or service lives. These micro-cracks/voids are very critical to study, since they can effectively play an important role in the behavior of the existing main crack in a component. This article aims to investigate the effect of the stop-hole retardation technique and multiple micro-cracks/voids with different characteristic lengths and geometries on the fatigue crack propagation in a compact tension specimen. A modified Forman equation, the so-called NASGRO equation is used to define the transition between crack initiation and crack growth period. Also, the extended finite element method is adapted in the crack propagation phase in order to model crack path in the geometry eliminating the need for remeshing procedure. The whole analyses are conducted in a commercial package through a user-written code that handles all fatigue crack growth analysis. The reference solutions from the literature are used to compare and to validate results obtained from current work.

Residual Strain Distribution around a Fatigue-Crack Tip Determined by Neutron Diffraction

2012 ◽  
Vol 706-709 ◽  
pp. 1685-1689
Author(s):  
E Wen Huang ◽  
Kuan Wei Li ◽  
Soo Yeol Lee ◽  
Wan Chuck Woo ◽  
Yi Shiun Ding ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Neutron Diffraction ◽  
Crack Growth ◽  
Residual Strain ◽  
Crack Tip ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
304L Stainless Steel ◽  
Crack Growth Mechanism

An analysis of residual stress, one of the contributory factors to the crack tip driving force, is extremely important to probe the fatigue crack growth mechanism and to further develop the life prediction methodology. Since fatigue crack growth is governed by crack-tip plasticity and crack closure in the wake of the crack tip, the investigation of residual stain/stress field in both behind and in front of the crack tip is crucial. In the current work, a 304L stainless steel compact-tension specimen is pre-cracked under constant-amplitude cyclic loading. Neutron diffraction is employed to directly measure the three orthogonal residual strain fields with 1-mm spatial resolution as a function of distance from the crack tip. The mapping results show that the three orthogonal residual-strain distributions around the crack tip depend on the stress multiaxiality, not following a single Poisson relationship to each axis.

Effect of Buffer Layer Thickness on Fatigue and Residual Stress of Welded High-Strength Low-Alloy

2013 ◽  
Vol 820 ◽  
pp. 110-113
Author(s):  
Chun Guo Zhang ◽  
Peng Min Lu ◽  
Jun Hong Li
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Buffer Layer ◽  
Hsla Steel ◽  
High Strength ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Before And After

The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.

Corrosion-Fatigue Crack Growth in Age-Hardened Al Alloys: Examples of Failures and Explanations for Fractographic Observations

2014 ◽  
Vol 891-892 ◽  
pp. 248-253 ◽  
Author(s):  
Rohan Byrnes ◽  
Noel Goldsmith ◽  
Mark Knop ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Al Alloys ◽  
Corrosion Fatigue Crack ◽  
Crack Tips ◽  
Corrosion Fatigue Crack Growth ◽  
Additional Support

The characteristics of corrosion-fatigue in age-hardened Al alloys, e.g. brittle striations on cleavage-like facets, are described, with reference to two examples of component failure. Mechanisms of corrosion fatigue (and explanations for fracture-surface features) are then reviewed. New observations of corrosion-fatigue crack growth for 7050-T7451 alloy compact-tension specimens tested in aqueous environments using a constant (intermediate) ΔK value but different cycle frequencies are then described and discussed. These observations provide additional support for a hydrogen-embrittlement process involving adsorption-induced dislocation-emission from crack tips.

Comparison of Fatigue Crack Growth Rates Between Different Specimen Geometries

2021 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Doré
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Literature Review ◽  
Crack Growth ◽  
Compact Tension ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Advantages And Disadvantages ◽  
Edge Notch

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.

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