In the manufacturing operation of pressure sensors, autofrettage denotes the procedure of active ?overload? by subjecting the pressure sensor selectively once or several 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 a long time of trouble-free operation of the sensors even at high load cycles reaching the specified overload range, without leading to zero-point shift or similar effects.
In autofrettage, certain local areas of the sensor, where through the selective overload the yield point of the sensor material is locally exceeded, become plasticised, producing a permanent change of the instrumentation characteristics. Fortune on the structural conditions by means of autofrettage can be an integral section of the development of the sensor and of the associated manufacturing process. Which pressure the sensor is put through 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 must not be figured every sensor will automatically benefit from subjecting it to autofrettage. Autofrettage can only be used for ductile materials, but for no reason for brittle ones. Conditioning must be scheduled and carried out very selectively and with great care through the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting can 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.