Material Creep
Elastomeric components exhibit a gradual decrease in sealing force over time when held at a constant deformation. Seal stress relaxation describes the loss of sealing force in a compressed gasket under a constant mechanical strain. This process leads to a reduction in the pressure-holding capability of the joint.
It is bounded by the material’s chemical structure and the ambient temperature.
Thermal Impact
Elevated temperatures accelerate the chemical and physical processes that cause the polymer chains to realign. In high-temperature environments, seal stress relaxation occurs much more rapidly, reducing the effective life of the gasket. This degradation causes the seal to lose its springback capability, which is necessary to maintain a tight joint.
Material selection must account for this temperature-dependent behavior.
Sealing Consequence
When the contact pressure of the seal drops below the pressure of the fluid, a leak path is created. This effect of seal stress relaxation is a common cause of failure in bolted joint assemblies over long operating periods. Regular inspections and torque audits help detect this loss of sealing force before leakage occurs.
The behavior is analyzed using specialized stress relaxation testing machines.
Design Consideration
Using high-grade elastomers with low relaxation rates minimizes the risk of joint failure over the product’s lifespan. This improves reliability.
