Effect of Load Excursions and Specimen Thickness on Crack Closure Measurements

2009 ◽  
pp. 246-246-19 ◽  
Author(s):  
FJ McMaster ◽  
DJ Smith
Keyword(s):  
Crack Closure ◽  
Specimen Thickness

Numerical Study of the Influence of the Crack Front Curvature in the Evolution of the Plastic Zone along the CT Specimen Thickness

2011 ◽  
Vol 465 ◽  
pp. 119-122 ◽  
Author(s):  
Daniel Camas ◽  
Pablo Lopez-Crespo ◽  
Antonio González-Herrera
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Plastic Zone ◽  
Crack Closure ◽  
Crack Front ◽  
Numerical Study ◽  
Load Level ◽  
Specimen Thickness ◽  
Aluminum Specimen ◽  
Front Curvature

This paper presents a numerical study of the influence of the load level and the crack front curvature on the plastic zone in the area close to the crack front. The aim of the work is to determine the influence of these parameters on fatigue crack closure. For this, a CT aluminum specimen has been modelled tri-dimensionally and several finite elements calculations have been made considering a large combination of the variables under consideration.

The Effect of Sheet Thickness on Near-Threshold Fatigue Crack Propagation and Oxide and Roughness-Induced Crack Closure

1987 ◽  
Vol 109 (1) ◽  
pp. 86-91 ◽  
Author(s):  
K. Tokaji ◽  
Z. Ando ◽  
K. Nagae
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Closure ◽  
Growth Rates ◽  
Sheet Thickness ◽  
Specimen Thickness ◽  
Low Carbon ◽  
Wide Range ◽  
Near Threshold

Characteristics of fatigue crack propagation have been investigated in a low carbon steel and a high tensile strength steel to evaluate the effect of sheet thickness. Crack propagation data are generated over a wide range of growth rates, from 10−8 to 10−3 mm/cycle, for load ratios of 0.05 and 0.70 at room temperature in laboratory air. Particular emphasis is placed on behavior at near-threshold growth rates. Near-threshold fatigue crack propagation behavior is found to show a marked sensitivity to sheet thickness, and near-threshold growth rates decrease and threshold values increase with increasing sheet thickness. Oxide and roughness-induced crack closure models are proposed as a mechanism for the effect of sheet thickness on near-threshold fatigue crack propagation. It is also shown that the requirement for specimen thickness recommended by ASTM, W/20≤B≤W/4, is not always valid for near-threshold fatigue crack propagation.

An Efficient Way to Characterize the Fatigue Crack Growth Based on Numerical Analysis

2009 ◽  
Vol 417-418 ◽  
pp. 653-656
Author(s):  
Ya Zhi Li ◽  
Jing He ◽  
Zi Peng Zhang
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Length ◽  
Crack Growth ◽  
Crack Closure ◽  
Load Ratio ◽  
Specimen Thickness

The behavior of plasticity induced fatigue crack closure (PICC) in middle tension specimen was analyzed by the elastic-plastic finite element method. For the constant-K (CK) loading cases, the opening stress intensity factor are independent of crack length. The level of increases with the maximal applied stress intensity factor for given load ratio and increases with for fixed . The in plane strain state is much smaller than that in plane stress state. The results under CK loadings can be deduced to constant amplitude cyclic loading case during which the load ratio, maximal load level, crack length and specimen thickness are all the factors affecting the crack closure effect. The phenomena revealed in the analysis are beneficial in understanding the driving force mechanism of the fatigue crack growth.

OS1302 Effect of specimen thickness on the crack closure level in aluminum alloy

2011 ◽  
Vol 2011 (0) ◽  
pp. _OS1302-1_-_OS1302-2_
Author(s):  
Yuya SUGAI ◽  
Sotomi ISHIHARA ◽  
Shota KOIKEDA ◽  
Takahito GOSHIMA
Keyword(s):  
Aluminum Alloy ◽  
Crack Closure ◽  
Specimen Thickness ◽  
Closure Level

A Method to Identify the Crack Closure and Opening in Cyclic Tearing Tests on Fracture Mechanics Specimens

2014 ◽  
Author(s):  
B. Tranchand ◽  
V. Aubin ◽  
S. Marie
Keyword(s):  
Crack Closure ◽  
Kinematic Hardening ◽  
Crack Opening ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Image Correlation ◽  
Electric Signal ◽  
Specimen Thickness ◽  
Secondary Circuit ◽  
Potential Measurement

To measure crack propagation in compact tension specimen, many methods can be used. The electric drop potential measurement is one of them and allows the detection of crack initiation. In our case, CT specimens, which have been taken from a carbon steel pipe (Tu42C) used in the secondary circuit of French PWR, are employed for cyclic tearing test. The detection of crack closure and crack opening should provide information for energetic analysis. However, the electric signal is unusable due to the cyclic loading. Indeed, because of the clearance between the pin and the specimen, each direction loading change causes a discontinuity in the signal. The roughness of the lips surface or the crack closure during compression loading returns also an unusual signal. Moreover, local measurement is required and there is high strain level around the crack tips, so strain gages are not suitable. Thus, displacement field are measured with digital image correlation and a specific image acquisition is employed. These methods allow a direct measurement of strain fields on the surface of the specimen. Thereby an interpretation of the previous electric signal and the crack opening and closure detection is realizable. Then, F.E. simulation, with non-linear kinematic hardening and node release method, are performed. These simulations allow the check of crack opening and closure detection through the specimen thickness.

The Effect of Specimen Thickness and Probe Size on Aem Analysis of Cr-Depletion Profiles in Sensitized Stainless Steel

1982 ◽  
Vol 40 ◽  
pp. 518-519
Author(s):  
E. L. Hall
Keyword(s):  
Grain Boundaries ◽  
Boundary Region ◽  
Chromium Concentration ◽  
Foil Thickness ◽  
Specimen Thickness ◽  
Probe Size ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Sensitization Process ◽  
Compositional Gradients

Sensitization in stainless steels is caused by the formation of chromium-rich M23C6 carbides at grain boundaries, which depletes the adjacent matrix and boundary region of chromium, and hence leads to rapid intergranular attack. To fully understand the sensitization process, and to test the accuracy of theories proposed to model this process, it is necessary to obtain very accurate measurements of the chromium concentration at grain boundaries in sensitized specimens. Quantitative X-ray spectroscopy in the analytical electron microscope (AEM) enables the chromium concentration profile across these boundaries to be studied directly; however, it has been shown that a strong effect of foil thickness and electron probe size may be present in the analysis of rapidly-changing compositional gradients. The goal of this work is to examine these effects.

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