Creep Retardation spectrum related

The retardation spectrum L X), where X is the retardation time, characterizes the contribution to the creep compliance J i), the dynamic storage compliance and the dynamic loss compliance J co) according to the following relations (for a viscoelastic liquid for a viscoelastic solid r is operationally infinite in the following equations),... 

In linear viscoelasticity, the creep function and the relaxation function are interrelated and each would permit the derivation of the viscoelastic constitutive relation under the condition that the principle of time invariance can be applied, meaning that the material is influenced only by a t) and s(f) and no other influencing variables are being effective. In summary, in the idealized case of the isothermal linear viscoelasticity under the conditions of static stress or strain, the linear viscoelastic behavior of a material may adequately be described by the creep function F t), the relaxation function R t), the retardation spectrum or the relaxation spectrum. 

The proposed method of data treatment has two advantages (1) It allows assessment of the status of blend miscibility In the melt, and (11) It permits computation of any linear viscoelastic function from a single frequency scan. Once the numerical values of Equation 20 or Equation 21 parameters are established Che relaxation spectrum as well as all linear viscoelastic functions of the material are known. Since there Is a direct relation between the relaxation and Che retardation time spectra, one can compute from Hq(o)) the stress growth function, creep compliance, complex dynamic compliances, etc. 

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