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 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 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. Faith on the structural conditions through autofrettage can be 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 every sensor design through a complicated FEM simulation and extensive test series.
Caution ? no experiments of your own! However, it must not be figured every sensor will automatically reap the benefits of subjecting it to autofrettage. Autofrettage can only be used for ductile materials, but under no circumstances for brittle ones. Dazzling must be scheduled and completed 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 also result in dangerous preliminary damage and subsequently possibly in accidents caused by fatigue and bursting of the sensor. In this way, an improvement in instrumentation is only going to be achieved, if, by hit or miss.