Experimental Study in Determining the Stress Intensity Factor by Using the Grid Method

2013 ◽  
Vol 740 ◽  
pp. 612-617
Author(s):  
Perng Fei Luo ◽  
Yung I Tsai

Grid method was used to measure the stress intensity factor KI of a mode I fracture specimen. The fracture specimen used in this study was a compact tension (CT) specimen made of 6061-T6 aluminum. A grid of dots was bonded along a radial line on the surface of the CT specimen. A 2D computer vision was used to acquire the images around the crack tip before and after the deformation of the CT specimen. Then the method of single dot was used to measure the magnitude and direction of the in-plane principle strains at the dot centers. Experimental results indicate that the measured strains can be used to accurately determine KI.

Holzforschung ◽  
2011 ◽  
Vol 65 (5) ◽  
Author(s):  
Hiroshi Yoshihara ◽  
Ami Usuki

Abstract The critical stress intensity factor of mode I (K Ic) obtained by compact tension (CT) tests of wood and medium-density fiberboard (MDF) was experimentally and numerically analyzed. A double cantilever beam (DCB) test was also conducted and the results were compared with those of the CT tests. Similar to the results of single-edge-notched bending (SENB) and single-edge-notched tension (SENT) tests previously conducted, the value of K Ic was obtained properly from the CT test when an additional crack length was taken into account.


In the present paper, experimental investigation on the fracture of aluminum alloy AA3003 are conducted on the Compact Tension Shear CTS specimen non-welded and CTS specimen welded by FSW process under mixed mode loading by using Arcan loading device based on Richard’s principle suitable for mixed mode. All loading in mixed mode starting from pure tension (mode I) up to pure shear (mode II) can be obtained and tested by varying the loading angles from 0° to 90°. The stress intensity factor for the Compact Tension Shear (CTS) specimen are determined three normalized lengths cracks 0.3, 0.5 and 0.7.The length of notches influence on the variation of stress intensity factor KI, KII. For CTS specimen with notches with a short length, the values of KII are greater than those obtained for notches with a long length.


2013 ◽  
Vol 05 (04) ◽  
pp. 1350044
Author(s):  
XIANHONG MENG ◽  
ZHAOYU BAI ◽  
MING LI

In this paper, the three-dimensional dynamic problem for an infinite elastic medium weakened by a crack of infinite length and finite width is analyzed, while the crack surfaces are subjected to mode I transient linear tractions. The integral transform approach is applied to reduce the governing differential equations to a pair of coupled singular integral equations, whose solutions can be obtained with the typical iteration method. The analytical solution of the stress intensity factor when the first wave and the first scattered wave reach the investigated crack tip is obtained. Numerical results are presented for different values of the width-to-longitudinal distance ratio z/l. It is found that the stress intensity factor decreases with the arrival of the first scattered longitudinal wave and increases with the arrival of the first scattered Rayleigh wave and tends to be stable. The static value considering both the first scattered wave and the first wave is about 50% greater than that considering only the first wave, and then the effect of the reflected wave is remarkable and deserves further study.


2011 ◽  
Vol 83 ◽  
pp. 54-59 ◽  
Author(s):  
Rui Zhang ◽  
Ling Feng He ◽  
Chang Rong Li

Applications of the digital image correlation method (DIC) for the determination of the opening mode stress intensity factor (SIF) is investigated using an edge cracked aluminum plate in this paper. Standard compact tension test specimen was tested under tensile loading and the full-field displacement fields of the test sample were recorded using DIC. The SIF associated with unavoidable rigid-body displacement translation were calculated simultaneously from the experimental data by fitting the theoretical displacement field using the method of least-squares. Selection of displacement and convergence values is discussed. For validation, the SIF thus determined is compared with theoretical results, confirming the effectiveness and accuracy of the proposed technique. Therefore it reveals that the DIC is a practical and effective tool for full-field deformation and SIF measurement.


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