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. Destroy is applied, to experience maximum stability, in particular 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 through 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 effect 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, must be determined individually for each sensor design by means of a complicated FEM simulation and extensive test series.
Caution ? no experiments of your! However, it must not be concluded that every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only just be used for ductile materials, but for no reason for brittle ones. Conditioning must be scheduled and carried out very selectively sufficient reason for 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 additionally result in dangerous preliminary damage and subsequently possibly in accidents due to fatigue and bursting of the sensor. In this way, an improvement in instrumentation is only going to be achieved, if, by hit or miss.