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 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 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. This selective effect on the structural conditions through autofrettage is an integral the main 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 each sensor design through an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your! However, Seize should not be concluded that every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only just be utilized for ductile materials, but for no reason for brittle ones. Conditioning must be scheduled and completed very selectively sufficient reason for 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 caused by fatigue and bursting of the sensor. In this manner, an improvement in instrumentation will only be achieved, if at all, by hit or miss.