Meaning
Gradual reduction in tension occurs within a material held at a constant strain over time. This internal stress relaxation happens because the molecular structure of the substance rearranges to accommodate the physical deformation. It differs from creep because the overall dimensions of the object stay the same while the force it exerts decreases.
Engineers must account for this behavior in fasteners or prestressed concrete structures. The rate of this change usually decreases as the material approaches a new state of equilibrium.
Structural Decay
Bolts and springs lose their clamping force as the material softens under sustained load. In many industrial applications, internal stress relaxation leads to loose connections that can cause mechanical failure. Regular inspections verify that the tension remains within the safety limits required for operation.
Component Longevity
Manufacturers select materials that resist this loss of tension to ensure a long service life. High performance alloys often undergo heat treatment to stabilize the crystalline structure against internal stress relaxation during use. Predictable performance over decades is mandatory for infrastructure projects like bridges or power plants.
Material Selection
Polymers and metals respond differently to constant strain depending on the ambient temperature and the initial load. Calculations for internal stress relaxation help designers determine the initial over-tensioning required to maintain a functional load over time. Accurate modeling prevents the need for frequent retightening of critical joints.
Choosing the correct material properties reduces the risk of unexpected loosening in high vibration environments.
