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Resumen:
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Stress relaxation curves of many solids can be normalized and presented in the linear form of F(0)t/[F(0)–F(t)]=k1 + k2t, where F(t) is the decaying force and k1,k2 are constants. The reciprocal of k2 denotes the asymptotic value of the relaxed portion of the initial stress. Since in active biological materials equilibrium conditions in the conventional sense are difficult to determine, the asymptotic values can be used to calculate residual moduli that are representative of the material short-term rheological characteristics. Similarly, creep curves of solids in which the strain (t) stabilizes or practically stabilizes with time (e.g., under small loads or in compression) can be presented by t/(t)=k1 + k2t, where 1/k2 is the asymptotic strain. It is shown that the relationships between asymptotic moduli, so calculated, and the strain in relaxation or the stress in creep can carry information that is relevant to structural changes that occur during deformation of the material such as development of hydrostatic pressure, internal fracture, and failure.
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