Autofrettage in pressure sensors ensures zero-point stability

In the manufacturing operation of pressure sensors, autofrettage denotes the process of active ?overload? by subjecting the pressure sensor selectively once or several times to a pressure above the nominal pressure range. Urge is applied, in order to achieve 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 reaching the specified overload range, without resulting in zero-point shift or similar effects.
In autofrettage, certain local areas of the sensor, in which 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 influence on the structural conditions by way of autofrettage is an integral portion 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 every sensor design by means of an elaborate FEM simulation and extensive test series.
Caution ? no experiments of your own! However, it should not be figured every sensor will automatically benefit from 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 completed very selectively and with great care during the production stages. Ill-considered ?overpressurising? of pressure sensors by laymen who like experimenting can not only damage the sensor permanently, but additionally 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 is only going to be achieved, if at all, by hit or miss.

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