Constant Rate of Stress Loading

If the stress is increased linearly starting from zero, on the other hand, the resulting strain will reflect the superposition of a series of retarded compliances. Then, if (T is the rate of stress increase, 

When the strain-stress curve obtained under these conditions is differentiated, the result is the creep compliance  

The restriction of linear viscoelastic behavior—small deformations—is more serious for equations 56 to 63 than for most of the preceding treatments, because with constantly increasing strain or stress the nonlinear regime may soon be reached. Then formulation in terms of a more complicated constitutive equation is necessary. 

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In deformation with a constant rate of strain, y is increased linearly with time (at constant 7) if the (otal deformation is small, a t) can be rather simply related to G t). In deformation with a constant rate of stress loading, a is increased linearly with time then y t) can be rather simply related to J t). These relations will be... 

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