Glossary

Linear Viscoelastic Region (LVER)

It is important when measuring the visco-elastic charac­teristics that measurements are made in the material’s linear visco-elastic region, where StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress and StrainStrain describes a deformation of a material, which is loaded mechanically by an external force or stress. Rubber compounds show creep properties, if a static load is applied.strain are proportional.  

In the LVER, applied stresses are insufficient to cause structural breakdown (yielding) of the structure and hence important micro-structural properties are being measured. When applied stresses exceed the yield StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress, non-linearities appear and measurements can no longer be easily correlated with micro-structural properties.

The linear visco-elastic region is typically determined from an experiment by performing a stress or strain sweep test and observing the point at which the structure begins to break down (see below). This, the limit of the linear visco-elastic region corresponds to the point at which Shear Modulus G*G or shear modulus is defined as the ratio of shear stress and shear strain.Gbecomes stress or strain dependent.