Installation Stress Analisys
Installation Stress Analisys
The equations provided are used to check that the elastic stress limit of the ring material is not exceeded by stress due to installation. Standard parts that are assembled manually in the recommended shaft/bore and groove diameters do not require analysis.
Special rings or rings being assembled with special tooling require analysis.
After forming, the ring's natural tendency is to return to its original state. This places the inner edge of the radial wall in residual tension and the outer edge in residual compression. To account for the residual stress in the ring when expansion is taking place, only 80% of the minimum tensile strength should be used to compare to the installation stress; see table 4.
To select a safe stress value, it is necessary to estimate the elastic limit of the raw material. The minimum tensile strength, as shown in Materials Selection Guide section, can be used as a suitable estimate. As with any theoretical calculation, a cioser analysis of the actual application may reveal that these stress values can be exceeded. However, particularconsideration must be made to functional characteristics such as installation method, the number of times the ring will be installed and removed, thrust load and/or centrifugal capacity.
In special designs, where the installation stress exceeds the materiai's elastic limit, rings can be produced to diameters which wilI yield a predetermined amount during assembly. Once installed, the ring will have the proper cling (grip) on the groove.
Installation Stress
Formula for external rings
Formula for internal rings
SE = Stress due to expansion (psi)
SC = Stress due to compression (psi)
E = Modulus of elasticity (psi)
b = Radial wall (in)
DS = Shaft diameter (in)
DH = Housing diameter (in)
DI = Free inside diameter, minimum (in)
D0 = Free outside diameter, maximum (in)
Table 4
Example: WS-100-S02
Minimum tensile strength of the ring material, from Materials Selection Guide section.
210,000 psi. Using 80% of 210,000 psi = 168,000 psi.
129,845 psi < 168,000 psi
Since the installation stress is less than 80% of the minimum tensile strength, permanent set is not expected.