A corrugated metal diaphragm is one of the most important elements for sensing pressure or differential pressure. Despite of a great deal of researches about the characteristics of pressureforce-displacement of diaphragms, any remarkable one has never yet been found to clarify the principle of forming a diaphragm in the manufacturing process.
The cause of cracks or wrinkles occured in the process of diaphragm forming will be made clear and also the optimum conditions of treatment will be shown in this paper. It is generally difficult to calculate the elongation on each part of the diaphragm except triangular wave diaphragm. A triangular wave diaphragm, as shown in Fig. 1, is formed with a piece of cone in bending process without any others. The cold working reduction of bending process is so little that the treatment is mainly done while the flat blank is being put into a cone.
Circular elongation ε
c(γ) and radial elongation ε
r(γ) are concerned with the inclination angle θ of the wave, the inside-to-outside radiuses ratio ρ (See Table 1) and the forming conditions. ε
c(γ) comes to maximum on the inside edge if the cone is formed in the situation of its outside edge fixed and its inside free. If the maximum elongation ε
cm exceeds the allowable elongation limit of the material, the diaphragm is radially broken. Table 1 shows the maximum elongation ε
cm.
In the situation of its inside edge fixed and outside free, ε
c(γ) comes to negative value and some creases radially come on the outside part of the diaphragm. In the state of the both inside and outside edges, freee, as shown in Table 2, ε
c(γ) is reduced to zero when γ=ρ
0R. In the situation of the both fixed, as shown in Table 3, the material is mainly elongated into the direction of radius.
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