Limit Load Equations for Miniature Single Edge Notched Tensile Specimens

Abstract

While carrying out fatigue tests on miniature Single Edge Notched Tensile (SENT) specimens, one needs to know the limit load of the specimen to determine the maximum and minimum loads of fatigue cycle. In the literature, several limit load equations, for example, EPRI, Graba, Miller were available. There were large differences in the predicted values of these equations. Moreover, these equations were developed for conventional size of the SENT specimens. Although, limit load equations should be ideally size independent, it was not clear whether boundary effect of the miniature specimens is there or not. Therefore, it was important to investigate the accuracy of these equations and check whether they are applicable for miniature specimens or not. Consequently, detailed non-linear finite element analyses were carried out on a number of miniature SENT specimens to determine the limit load by twice elastic slope method. Elastic-perfectly plastic material behavior was assumed as is the convention. Based on these results, new limit load equations have been proposed for miniature SENT specimens. It was found that the present results match very closely with the prediction of Miller equation. However, they widely differ with respect to EPRI and Graba equations. Consequently, it is concluded that Miller equation is the most accurate to predict the limit load of SENT specimens and is applicable for miniature specimens as well without any boundary effect.