Meaning
Rheological behavior where the resistance to lateral deformation in a material decreases over time while held at a constant strain. Observation of this decline in stress is necessary for understanding the long-term performance of elastomers and viscoelastic plastics. Shear modulus relaxation occurs as the internal molecular network rearranges to relieve the applied force.
This process is particularly relevant for seals and gaskets that must maintain a specific pressure over years of service.
Joint Stability
Mechanical fasteners that rely on the elastic response of a washer can lose their clamping force due to this phenomenon. If the shear modulus relaxation is too rapid, the joint will loosen, potentially leading to leaks or structural failure. Engineering contracts for aerospace or automotive components often include strict limits on this decay rate.
Service Life
Prediction of the effective life of a component involves modeling how the modulus will change under different environmental conditions. Exposure to heat typically accelerates the relaxation process. Manufacturers provide data sheets that help buyers select materials that will remain functional for the duration of the product warranty.
Creep Correlation
Relationship between stress relaxation and material creep helps in designing for static loads. These two behaviors are linked.
