The effect of cyclic twist angle on mechanical properties for AISI 1038 medium carbon steel

Abstract

A group of 11 specimens AISI 1038 Medium carbon steel alloy fabricated according to ASTM standard D790-02 torsion test were twisted cyclically one in positive another to negative angle in range of angles (0^o-50^o), step 5 degrees for each specimen. The data from torsion test device help to get actual torques and shear stresses, later the specimens tested the tensile test to figure out the effects of cyclic angle of twist on mechanical properties for AISI 1038 Medium carbon steel. The results showed a good agreement between the theoretical and actual data (torque, shear stress) for specimens with positive angle of twist by the percentage: 98%, 91%, 96%, 93%, 91%, 89%, 88%, 85%, 82%, 81%, 80%. In other side the results for experimental tests showed a dangerous decrements in mechanical properties for cyclic or negative twist angles, the yield stress for reference specimen without twist angle is 490 Mpa, yield stress increased for angels (5^o,10^o,15^o) by 1%, 3%, 6%, then decreased for angels (20^o,25^o,30^o,35^o,40^o,45^o) by 3%, 5%, 13%, 18%, 24% and 35% Respectively and the final specimen with 50^o angle of twist had been broken torsional before tensile test as a result specimens groups consequent of the extrusion – intrusion defects concomitant from twisting load.