Fault mechanism analysis and accelerate life testing for pneumatic cylinders
This paper focuses on accelerated life test on cylinders for pneumatic industry which sharply shortens the test time to get the reliability evaluation specification and decreases the cost during products development stage. Accelerated tests are valuable tools to get information quickly on life distribution which is achieved by subjecting the test units to conditions that are more severe than the normal ones. After the accelerated life test results are efficiently feedback to the designer, the design defects are exposed and proper material is selected. Long lifetime pneumatic cylinders are selected as the test object. Section I covers the fault mechanism analysis By the failure mode and effect analysis and fault mechanism analysis, the piston and piston pole parking are the weak units as they are movable parts as well as leakage sources which easily result in the cylinders failure. Liquid temperature and operating frequency are chosen as stresses since their accelerating potentials are available for the specific cylinders, then constant double stress life testing spectrum and tests matrix are scheduled and implemented. The extended Arrhenius model is combined based on a theoretical relationship between chemical and physical reaction rates and stresses. Lastly, the complete ALT data is presented by using Weibull distribution and Bartlett verifying method. Estimation for the parameters of Arrhenius model and other characteristics of cylinders population life distribution are done successfully. From the 3-axis graph plotted, the effects of each stress to cylinders can be seen clearly which provide satisfactory results for cylinders researcher and developer.