The caustic method has proven to be a useful optical method to determine stress intensity factors. This paper evaluates the stress intensity factors of a sharp V-notch under pure shear loading by the caustic method for isotropic materials. The elastic stress fields and caustics formation near the V-notch tip under pure shear loading are first introduced. The theoretical relationship between the stress intensity factor of the sharp V-notch and the characteristic length is derived. Then, the experiment on the V-notched polymethyl methacrylate specimens under pure shear loading is carried out to obtain the stress intensity factor with the derived caustic formulation. Finally, the present results obtained from caustics are compared to the results available in the literature. The good accuracy of the results obtained demonstrates the ability of the caustics method in the determination of the stress intensity factor of a sharp V-notch.
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