After-effect, elastic

The quick release phenomenon is characteristic of the contracted state. The tension produced by stretching an uncontracted muscle or model falls after release only a little below the new equilibrium value, which is finally reached by a small elastic after-effect (see curves 1, 2, 3, and la and 2a of Fig. 4). 

Fig. 4. Redevelopment of tension in presence of ATP, and elastic after-effect in the absence of ATP, following release. Curve 1 stretched fiber without ATP Curve 2 unstretched fiber with ATP Curve 3 fiber after washing out ATP (from A. Weber, 1951). Curve la stretched actomyosin thread without ATP curve 2a the same, unstretched, with ATP (from Portzehl, 1950b).

Further, after the stretch is stopped, the tension decreases much less in an inactive model than it does in the active one or in muscle. Thus the pronounced rigidity of the inactive fiber is shown also by its lack of elastic after-effects (see Fig. 6 Section II, 3ff). 

The data obtained were used to estimate the moduli of fast and slow elastic deformations, the equilibrium modulus of elasticity and viscosity of elastic after-effect. 

Elastic After>effect. When glass and certain ceramic materials are subjected to stress for a long period they remain partly deformed when the stress is removed the elastic after-effect is the ratio of the deformation remaining after a given time to the deformation immediately after removal of the stress. 

Shchukin, E. D. and P. A. Rehbinder. 1971. The mechanism of elastic after effect in structured bentonite suspensions of low concentration. Kolloidnyi Zh. 33 450-458. 

To further illustrate the point of a liquid with both elastic and viscous behavior, the flow of a rheological liquid is shown in Fig. 1.2. Here a polymer liquid is in a clear horizontal (to avoid gravity effects) tube and a dark reference mark has been inserted that moves with the fluid. The liquid is unpressurized in frame 1 but a constant pressure has been applied in frames 2 through 5 where motion can be seen to have taken place as time progresses. In frame 6 the pressure has been removed and in frames 7 and 8 the liquid can be seen to partially recover. No recovery would take place if this were an ordinary viscous liquid. This is known as an elastic after effect and a similar effect or creep recovery is observed in viscoelastic solids and/or all polymers provided the correct temperature is chosen. 

Wc see that the system of Fig 13 exhibits features both of the Maxwell liquid (Fig. 14) and of the Kelvin body (Fig. 17). The permanent deformation als occurs in Fig 14, the elastic after-effect only in Fig. 17 ... 

Hardness of plastics is difficult to establish and compare because there is an enormous range of values. Hardness measured by indentors is also difficult because there is an elastic recovery effect. Among the most important methods for testing this property are Ball hardness, Rockwell hardness, and Shore hardness. Olher methods are also commonly used. The Rockwell hardness test determines the hardness after allowing for elastic recovery in the test specimen. Both Ball and Shore hardness tests exclude any elastic recovery effects. 

Rabotnov, Y.N. (1948) Equilibrium of elastic medium with after-effect. Prikl. Mat. Mekh. 12, 53-62 Rabotnov, Y.N. (1969) Creep Problems in Structural Members (North Holland, Amsterdam) Rabotnov, Y.N. (1980) Elements of Hereditary Solid Mechanics (Mir Publishers, Moscow)... 

Higher temperatures result in permanent degradation. The amount of this irreversible loss in mechanical properties depends upon moisture content, heating medium, temperature, exposure period, and, to some extent, species. The effects of these factors on modulus of mpture, modulus of elasticity, and work to maximum load are illustrated in Figures 6—9 (6). The effects may be less severe for commercial lumber than for clear wood heated in air (Fig. 10). The permanent property losses shown are based on tests conducted after specimens were cooled to - 24° C and conditioned to a moisture content of... 

Figure 8.10. Effect of melt temperature on onset of elastic turbulence in polyethylene. (After Howells...

Figure 8.11. Effect of molecular weight on critical shear stress at onset of elastic turbulence in poly(methyl methacrylate). (After Howells and Benbow )...

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