Abstract
The tightening pressure in gland packings decreases over time after tightening due to stress relaxation .This paper deals with the change over time in normal and axial pressure distribution in piled gland packings of asbestos and graphite. An analytical method for the pressure change is presented with consideration given to stress relaxation by use of the viscoelastic model previously introduced by the authers. Stress relaxation tests of some gland packings are performed on some gland packings. Both for asbestoid and graphitic packings, the normal-to-axial pressure ratio and the friction coefficient are not changed by stress relaxation. The effect of cyclic tightening in preventing stress relaxation is discussed.
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