Accelerated life test for reliability evaluation of pneumatic cylinders

Pneumatic cylinders are intended to be designed for high reliability and long lifetimes. Evaluating such designs through conventional life tests is difficult as the affordable test time is too short to generate a meaningful amount of failure data. In this paper, we design and implement an accelerated life test (ALT) for evaluating the reliability of pneumatic cylinders. From a detailed analysis of failed samples from field operation, the major failure mechanisms that affect the reliability of pneumatic cylinders are identified, e.g., wear and tear of sealing rings. For these failure mechanisms, temperature and frequency are found out to be the significant stresses of the pneumatic cylinders. A two-factor-four-level full-factor design of ALT is, then, performed to set up an ALT plan for the pneumatic cylinders. A total number of 95 samples are tested according to the ALT plan, and a mixed Arrhenius-inverse-power-law model is used to fit the test data and predict the reliability under normal operation conditions. In addition, a normal stress test of eight samples is performed to validate the reliability predicted by the ALT. The results show that using the proposed ALT, the reliability of the pneumatic cylinder can be predicted with satisfactory accuracy. It is also shown that the designed ALT plan requires only 38.77% of the testing effort of other conventional life tests.