6. Conclusion

Substituting Eq. (76) into Eq. (73), we find the total gap density for elastic-plastic contact.

Figure 10. The gap density with/without taking into account the mutual influence of asperities (a) and for different values

Figure 10 presents the dependencies of the gap density on the relative force parameter qσ.

Ensuring specified tightness or leakage rate is related to the determination of the force parameters f <sup>q</sup> or qσ. The sealing capacity of the SJ is evaluated by the permeability functional by Eq. (1). The contact characteristics—the relative contact area η and the gap density Λ, included in Eq. (1), are defined in the previous section. Included in Eq. (1), the probability vk of the medium flowing through the SJ is determined by the fusion of contact spots and is given in

Ref. [3]. Two adjacent asperities will merge if η<sup>i</sup> > 0:5for each asperity.

The required permeability functional is determined by [3]

The force parameters <sup>f</sup> <sup>q</sup> or <sup>q</sup>σ, that providing a given level <sup>C</sup><sup>∗</sup>

Figure 11 shows the dependences for the elastic and elastic-plastic contacts.

C∗

<sup>u</sup> <sup>¼</sup> <sup>2</sup>lμG�

R3 maxrΔp

and outlet pressures; μ is the dynamic viscosity; Δp ¼ p<sup>1</sup> � p2; and l is the compacting band

l

<sup>l</sup> is the specified tightness; r is the density of the sealed medium; p<sup>1</sup> and p<sup>2</sup> are the inlet

, (77)

<sup>u</sup> are determined from the Cu f <sup>q</sup>

5. Ensuring specified tightness

where G�

of p and q (b).

22 Contact and Fracture Mechanics

width.

or Cu q<sup>σ</sup>

(Figure 11).

Using the proposed model of roughness as a result of the studies, methods for determining the contact characteristics and the conditions for ensuring a specified tightness of the joints were developed and established:

