Accelerated ratcheting testing of polycarbonate using the time-temperature-stress equivalence method

The long-term performance of polymers under cyclic loading is important for safety assessments in engineering applications. The deformation process under the cyclic loading can be accelerated through use of temperature and stress. As for asymmetric cyclic loading, so called ratcheting, a time-temperature-stress (TTS) equivalence method in which all the parameters have clear physical meanings and can be determined experimentally, was proposed to predict the long-term cyclic loading behavior for polycarbonate using short-term data. Taking into consideration the effects of both the mean stress and the stress amplitude, the ratcheting compliance was defined and its evolution function was also provided. Next, the TTS equivalence method was validated using the long-term ratcheting test results for the polycarbonate. Time, temperature, and stress do show equivalent effects on long-term ratcheting of polycarbonate. Using the proposed method, time and cost can be dramatically saved for the assessment of the long-term cyclic loading performance of polycarbonate.