Experimental studies on the extent of 3D and 2D stress-strain states at sharp V-notches

A sharp V-notched plate under plane stress loading conditions is always accompanied by a strong three-dimensional (3D) stress-strain region close to the notch tip, followed by a 3D-2D transition state and a region dominated by the 2D stress-strain field. Experimental studies on planar V-notched bodies constitute an important part of notch fracture mechanics and therefore it is important to know the extents of the above fields for accurate measurement of field variables. In the present work, experimental verification of the extent of the 3D stress-strain field, 3D-2D transition zone and plane stress zone ahead of the tip of a sharp V-notch has been carried out in order to suggest a minimum radius required for identification of the plane stress dominant zone. Knowing this value apriori is vital for accurate sampling of the 2D field variables in any experimental study on the sharp V-notched configurations. In order to achieve this, strain gage experiments on the single-edge notched tensile (SENT) specimens have been conducted. The above zones have been identified by studying the error in the measured mode I NSIF of the SENT specimen. The experimental results of the current study agree well with the results of published numerical works. The results clearly show that the minimum radius of the plane stress dominant zone has been found to be 1.25 times the thickness of the plate. Results also show that 1.5 times the thickness is the most conservative and dependable value for this radius. The results of the present investigation also indicate that not only the identification of the plane stress region, but also the locations of the sampling points within the plane stress region are important for achieving the required accuracy.