A strain gage technique for mode I notch stress intensity factor of sharp V-notched configurations

Abstract

A simple and robust single strain gage technique for accurate measurement of mode I notch stress intensity factor (NSIF) for sharp V-notched configurations has been proposed. The technique is supported by strong theoretical foundation, and it allows the strain gage to be placed reasonably away from the notch tip thus avoiding various problems associated with singularities. Importantly, in contrast to the available techniques, the present strain gage technique also prescribes proper radial locations (optimal locations) for the strain gage which are extremely useful in accurate measurement of NSIFs. A general theory and procedure has been developed for the estimation of these gage locations a priori for any given sharp V-notched configuration. These locations are shown to be dependent on the notch angle and notch length to width ratio. Experiments have been conducted using linear strain gages of 1 mm gage length and the results show that accurate NSIFs can be measured using the proposed single strain gage technique. The numerical results of the present investigation clearly show that very accurate (of the order of less than 1% error) mode I NSIF can be measured using the proposed single strain gage technique if the gages are placed at the optimal locations. The present results also demonstrate that highly inaccurate (of the order of 45% error) and unacceptable NSIFs would result if the gages are placed at non-optimal gage locations.