In the manufacturing operation of pressure sensors, autofrettage denotes the procedure of active ?overload? by subjecting the pressure sensor selectively once or many times to a pressure above the nominal pressure range. This process is applied, in order to achieve maximum stability, specifically of the zero point, in later operation. Assuming a suitable 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 resulting in zero-point shift or similar effects.
In autofrettage, certain local regions of the sensor, where during the selective overload the yield point of the sensor material is locally exceeded, become plasticised, producing a permanent change of the instrumentation characteristics. This selective influence on the structural conditions by means of autofrettage is an integral part of the development of the sensor and of the associated manufacturing process. Which pressure the sensor is subjected to and how often, must be determined individually for every sensor design by means of an elaborate FEM simulation and extensive test series.
digital pressure gauge ? no experiments of your own! However, it must not be concluded that every sensor will automatically benefit from subjecting it to autofrettage. Autofrettage can only be utilized for ductile materials, but for no reason for brittle ones. Conditioning should be scheduled and completed very selectively and with great care through 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 due to fatigue and bursting of the sensor. In this manner, an improvement in instrumentation is only going to be achieved, if at all, by hit or miss.