Simple tech instruments manufactures a numerically controlled machine capable of pressurising the bellows with air and doing a life test by application of cyclic compression and tension with the help of a hydraulic servo actuator. The cyclic load application is continued till the failure is detected. Failure criterion is the loss of capability to maintain the air pressure. During the cyclic force application, each cycle is counted to give the life in the number of cycles of stress reversals. The system is designed to do automatic testing without much of a manual adjustment. The actuator is given with 0-500 mm stroke, and is programmable with a resolution of 0.1 mm. The system consists of the basic machine, the servo actuator, air pressure control devices and the instrumentation unit. The machine is a rigid two column type structure with the servo actuator mounted on the top. The servo actuator comprises a hydraulic cylinder, power pack, control valves, length measurement transducer, and the control system. The air pressure control device includes a non-retum valve, a solenoid operated direction control valve and a pressure transducer. The microprocessor based instrumentation system consists of two 8-digit displays to show the actuator displacement, pressure and the number of cycles of load applied. A keyboard is given for programming the test parameters.
