Experimental Observation on the Pure Torsional Ratchetting of Polycarbonate Polymer at Room Temperature

Abstract

The stress-controlled pure torsional cyclic tests are carried out to investigate the torsional ratchetting of polycarbonate (PC) polymer at room temperature. The effects of applied shear mean stress, stress amplitude, stress rate, peak stress hold, and stress history on the torsional ratchetting are discussed. The shear strain of tubular specimen is measured by a noncontact digital image correlation (DIC) apparatus. The results show that the torsional ratchetting of the polymer obviously depends on the applied shear stress level, stress rate, and peak stress hold; the shear ratchetting strain and its rate increase with the increasing mean stress, stress amplitude, and peak stress hold time and with the decreasing stress rate. Moreover, the torsional ratchetting depends on the stress history. A higher stress level cyclic loading history restrains the evolution of torsional ratchetting in the subsequent lower stress level cyclic loading, while the lower stress level cyclic loading history promotes the torsional ratchetting of the subsequent higher level cyclic loading.