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, in order to achieve maximum stability, in particular 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 leading to zero-point shift or similar effects.
In autofrettage, certain local regions of the sensor, in which during 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 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 subjected to and how often, should be determined individually for every sensor design by means of a complicated FEM simulation and extensive test series.
Private ? no experiments of your! However, it should 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 under no circumstances for brittle ones. Conditioning must be scheduled and carried out very selectively sufficient reason for great care during the production stages. Vilified -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 manner, an improvement in instrumentation is only going to be achieved, if at all, by hit or miss.