Volume 35, Issue 1 (January 2007)
V-Notched Shear Specimens for the Inclined Double Notch Shear Test
A numerical study of a modified specimen geometry for the inclined double notch shear (IDNS) test was performed. The test uses the standard double notch compression (DNC) specimen whose geometry was modified by replacing the straight grooves with tilted V notches. Arising stress fields were calculated by use of a BEM scheme. Four different geometry parameters were investigated; relative notch distance, specimen loading, and notch tilt and notch opening angles. Different evaluation criteria to determine optimal specimen and test geometries were studied with respect to effects on stress uniformity and stress concentrations/singularities. No single criterion was found to be obviously superior. Judicious specimen loading enabled cancellation of the significant mode I singularity, whereas a careful specimen design enabled the simultaneous cancellation of both modes I and mode II singularities in most specimens. Singular fields (for mathematically sharp notches) were predominant over distances comparable to the root radii used in practice, and thus not very relevant. Further, the shear stress level arising in the specimen center (and in its major part) was controlled by the specimen inclination, whereas stress concentrations in the notch root vicinity were governed mainly by notch tilt and notch opening angles. Appropriately titled, but sharper notches seemed to result in the generally most uniform stress fields. For the issues studied, several accurate closed form expressions were presented.