In the manufacturing operation of pressure sensors, autofrettage denotes the process of active ?overload? by subjecting the pressure sensor selectively once or many times to a pressure above the nominal pressure range. This technique is applied, to experience maximum stability, specifically of the zero point, in later operation. Assuming the right design of the sensor, autofrettage enables many years of trouble-free operation of the sensors even at high load cycles achieving the specified overload range, without leading to zero-point shift or similar effects.
In autofrettage, certain local areas of the sensor, where during the selective overload the yield point of the sensor material is locally exceeded, become plasticised, resulting in a permanent change of the instrumentation characteristics. This selective influence on the structural conditions by means of autofrettage is an integral area of the development of the sensor and of the associated manufacturing process. Which pressure the sensor is subjected to and how often, should be determined individually for every sensor design through an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your own! However, it should not be concluded that every sensor will automatically benefit from subjecting it to autofrettage. Autofrettage can only just be used for ductile materials, but for no reason for brittle ones. Lonely must be scheduled and carried out very selectively and with great care during the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting will not only damage the sensor permanently, but also bring about dangerous preliminary damage and subsequently possibly in accidents caused by fatigue and bursting of the sensor. In this manner, an improvement in instrumentation will only be achieved, if, by hit or miss.