Determination of mode I stress intensity factors of complex configurations using strain gages

Abstract

Among techniques for the determination of the mode I stress intensity factors (SIFs), strain gage procedures are the simplest and most straightforward. We report here on an experimental investigation of the determination of opening mode stress intensity factors using the single strain gage method. Our approach overcomes certain drawbacks and greatly widens the applicability of strain gage methods in the determination of static SIFs of complex configurations. The approach was tested through experiments on specimens of finite width and finite height edge-cracked plates (fully finite plates) subjected to tensile stress. We compared the experimentally determined mode I stress intensity factors of fully finite plates with the computed values using finite element analysis, obtaining good agreement between the present approach and computed values.

A New FEM Approach for the Determination of Fracture Parameters in Polymethyl-metacrylate PMMA

“…The radial position of the strain gage r = 3 mm was chosen in all tests based on the stress gradient analysis presented in [12]. Figure 4 and 5 show a comparison between the results of SIF as a function of the applied load measured experimentally [9] and obtained by the proposed model for a/w = 0.3 and 0.5 with h/w = 0.3, 0.5, 0.7, 1.0. The figures show that the measured SIF are linearly proportional with the applied load.…”

“…Where A 0 , A 1 and B 0 are unknown coefficients which can be determined by using the specimen geometry and boundary conditions. Using the definition of K I , one can easily show that it is related to A 0 by [2][3][4][5][6][7][8][9][10][11]:…”

“…It has long been acknowledged that in plates of finite thickness the stress field near the crack tip is three-dimensional in nature. From the finite element results of Levy et al [7], Nakamura and Parks [8] and the experimental results of Rosaki s and Ravi-Chandar [9], it has been shown that the local yielding effect is only significant within a radial distance about one-half thickness from the crack tip. For the rest of the area, the plane stress condition is expected to dominate.…”

“…In contrast with Dally and Sanford [2]; Wei and Zhao [13]; Kuang and Chen [14] and jogdand [16], our work attempts to measure accurately the SIF using relative large strain points method under monotonic increasing loads in fully finite edge-cracked plates subject. To validate the proposed method for the determination of SIF's, we compare our computer-calculated values obtained using Abaqus finite-element software with experimental results of Swamy et al [9].…”

Averaging effects of a strain gage

“…The user can select the smallest practicable gage length, but needs to be aware of the greatly increased error and uncertainty in the indicated strains due to the nature of the gage and instrumentations. It is worth noting that using relatively large strain gages enhance the accuracy of measuring strain at a high strain gradient [19]. Case 3: In this case, both the gage length (l g =0.5) and width (w=0.5) are held constant while the horizontal distance from the hole's edge to the first filament is varied.…”