Postulated by strength theory, the reference stress σv must be derived from the three stresses σt (tangential stress), σr (radial stress), and σn (normal stress) to allow an assessment of the service life. The reference stress is then correlated with the material’s characteristic values.
Transducers used in the ultra-high-pressure range (>10,000 bar) are designed such that the material’s yield point is exceeded at the internal fiber, which is subjected to the highest loading. This does not mean that the transducer will be torn apart, since the outer layers of the measuring body still “bear” the pressure very well. If the pressure is increased still further, the place at which the yield point is exceeded moves slowly outward inside the wall. The transducer would only break when the yield point has moved to the outermost layer.
The ratio of internal diameter to external diameter (Da/Di), and thus the thickness of the wall, must be chosen so that the dynamic properties of the spring steel can be fully utilized, and the maximum capacity for load changes is reached.
If cleverly implemented, this design offers the advantage of optimally utilizing the material in terms of its endurance strength values.