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There are currently one or two kinds of strain gages to measure the stress intensity factor. It might not be sometimes easy to analyze the stress intensity factor with those gages. In this paper, it is reported that our development of the new stain gage enables us to measure the stress intensity factor more easily and practically. The following features of this strain gage to evaluate the stress intensity factor are presented in this paper. (1) Strain component ε r measured around the crack tip is used to calculate the stress intensity factor. (2) To be more specifically, we employed the first and second terms of the series at the strain component ε r around the crack tip for an evaluation of the stress intensity factor. The calculation method with using our developed strain gage does not require the crack length. The newly developed strain gage was bonded to around the crack tip of the specimens, where cracks were of the opening mode or the mixed mode. We carried out tensile tests on the test pieces bonded with the gage. In conclusion, the results indicate that the developed strain gage enables us to measure stress intensity factor with an error margin within ±10% of the analytical values.

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Soft cellular solids hke sponge and muscle have the nonlinear viscoelasticity due to the internal gas or liquid in cells and the behavi r of the matrix of the solids ． Their stress − time curves are d至 fferent by the variation of their interna 星 structures ， and it causes difnculties in the evaluation of the mechanical characteristics of the solids ． In this study ， we adopted the multiplication form of power and exponent functions that is able to approximate the nonlinear and fluctuated behavior of soft cellular solids ， Then ， we examine the adequacy of this method by its application to the experimental results of tensile testings of SBR sponge and bio且ogical soft tissue ． The results of the examination show that the adQpted form Qf the functions have good ability to 丘t the complex results of the stress − time curves and it can realize gQod evaluation ef viscoel ． asticity of soft cellular solid by using three − element solid rnode1 ．