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 process 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 resulting in zero-point shift or similar effects.
In autofrettage, certain local regions 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 influence 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 subjected to and how often, must be determined individually for each sensor design through a complicated FEM simulation and extensive test series.
Caution ? no experiments of your! However, it should not be figured 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. Honored -considered ?overpressurising? of pressure sensors by laymen who like experimenting can not only damage the sensor permanently, but also 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.