The Influence of End Frictions on Stresses in Compressed Specimens

Abstract

The present paper concerns the influences of end frictions on stresses in compressed rectangular and cylindrical specimens. In numerical calculations, the finite element method was employed. The following conclusions are made on the influences of the end frictions on stresses in the compressed specimens. (i) The more the end friction between the end of the specimen and the platten is reduced the more uniform stresses are developed in the specimen. (ii) When Poissoin's ratio is 1/6 and the coefficients of the end friction are approximately larger than 0.25, no lubrication can be practically expected, in other terms stresses in specimens with such coefficients of end friction are practically the same as stresses in specimens completely restrained at the ends. (iii) Stresses in both rectangular and cylindrical specimens are similar. The only difference is that the deviations of the axial stresses for various coefficients of frictions from the average are larger in cylindrical specimens than those in rectangular ones. (iv) Stresses in the mid-height region of the specimens are not so sensitive to the end friction as the compressed ends. Uniformity of stresses depends on the width-height or radius-height ratios as well as the end frictions. (v) For sufficiently small coefficients of the end friction, some portions of the end of the specimen slide and the shear stresses on the end become terrace-like and axial stressses become more or less uniform.