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Transient creep

This result is plotted as a function of m in Fig. 9.2. If a< ac, the composite will creep until the strain is consistent with Eqn. (60) and thereafter no further creep strain will occur. Of course, the noncreeping state will be approached asymptotically. (It should be noted that due to possible fiber failure during the creep transient, the true value for crc may lie below the result given in Eqn. (62).) For an applied composite stress equal to, or exceeding, cre, creep will not disappear with time because all of the fibers will eventually fail and the strain will continue to accumulate. [Pg.320]

Thompson, E., 1986. Use of pseudo-concentration to follow creeping flows during transient analysis. Ini. J. Numer. Methods Fluids 6, 749 -761. [Pg.110]

The relaxation and creep experiments that were described in the preceding sections are known as transient experiments. They begin, run their course, and end. A different experimental approach, called a dynamic experiment, involves stresses and strains that vary periodically. Our concern will be with sinusoidal oscillations of frequency v in cycles per second (Hz) or co in radians per second. Remember that there are 2ir radians in a full cycle, so co = 2nv. The reciprocal of CO gives the period of the oscillation and defines the time scale of the experiment. In connection with the relaxation and creep experiments, we observed that the maximum viscoelastic effect was observed when the time scale of the experiment is close to r. At a fixed temperature and for a specific sample, r or the spectrum of r values is fixed. If it does not correspond to the time scale of a transient experiment, we will lose a considerable amount of information about the viscoelastic response of the system. In a dynamic experiment it may... [Pg.173]

The Imass Dynastat (283) is a mechanical spectrometer noted for its rapid response, stable electronics, and exact control over long periods of time. It is capable of making both transient experiments (creep and stress relaxation) and dynamic frequency sweeps with specimen geometries that include tension-compression, three-point flexure, and sandwich shear. The frequency range is 0.01—100 H2 (0.1—200 H2 optional), the temperature range is —150 to 250°C (extendable to 380°C), and the modulus range is 10" —10 Pa. [Pg.199]

Creep deformation can be split into three separate parts. The first, transient creep, is a short lived phenomenon which gives a high initial rate of deformation but decays according to the expression ... [Pg.1358]

The behavior of materials under dynamic load is of considerable importance and interest in most mechanical analyses of design problems where these loads exist. The complex workings of the dynamic behavior problem can best be appreciated by summarizing the range of interactions of dynamic loads that exist for all the different types of materials. Dynamic loads involve the interactions of creep and relaxation loads, vibratory and transient fatigue loads, low-velocity impacts measurable sometimes in milliseconds, high-velocity impacts measurable in microseconds, and hypervelocity impacts as summarized in Fig. 2-4. [Pg.44]

Many other techniques of measuring viscoelastic parameters, such as transient shear, creep and sinusoidally-varying shear, are available. A good description, together with the merits and demerits of each of these techniques, is available in Whorlow(19. ... [Pg.118]

Rheological Measurements Three types of rheological measurements have been carried out. In the first type, transient (creep) measurements were performed on a 20% w/w dispersion of latex A, as a function of coverage by PVA. These experiments were carried out using a "Deer" rheometer (PDR 81, Integrated Petronic Systems, London) fitted with a stainless steel concentric cylinder. The procedures used have been described in detail before (21,22). [Pg.414]

Polymer liquid crystal solutions respond in an interesting way to a transient flow field. For example, a damped oscillatory response was observed upon a flow inception or flow reversal [150,156,157], and the strain was recovered to some extent after a creeping flow [158], These phenomena suggest that liquid crystal solutions have some textured structure, i.e., the spatial variation in the... [Pg.147]

Transient Acceleration of Creep Rates of Polymers During High Intensity Irradiation... [Pg.89]

Creep curves of Si3N4 at high temperatures generally consist of three regimes transient, steady-state, and accelerated creep, similar to metals. The creep rate under tensile stresses is some orders of magnitude higher than under compression [412, 416]. [Pg.113]

E. Thompson, Use of Pseudo-concentrations to Follow Creeping Viscous Flows during Transient Analysis, Int. J. Numer. Meth. Fluids, 6, 749-761 (1986). [Pg.818]

The reaction mixture is able to react, ignition occurs at the reactor exit and a reaction front moves toward reactor inlet. The resulting steady state is at the reactor inlet and a strong preheating of the inlet gas occurs. The transient operation is referred to as "creeping profiles" and was extensively studied by Amundson [4-6]. Experimentally observed in [1, 15]. [Pg.91]

Kr Crack growth resistance eT Transient creep strain... [Pg.10]

From Eqn. (5) we see that the important intrinsic variables controlling creep are the boundary thickness, w, the grain size, d, and the viscosity of the boundary fluid, tj. If these parameters change in the course of the deformation process, a corresponding change in the creep rate will occur, leading to transient creep behavior. [Pg.135]

The flow model readily explains creep asymmetry and transient creep of... [Pg.136]

Modeling of Creep Behavior and Transient Redistribution in Stress between Constituents... [Pg.161]

Fig. 5.1 Idealized representation of the transient change in fiber and matrix stress that occurs during the isothermal tensile creep and creep recovery of a fiber-reinforced ceramic (the loading and unloading transients have been exaggerated for clarity). It is assumed that the fibers have a much higher creep resistance than the matrix. The matrix stress reaches a maximum at the end of the initial loading transient. After full application of the creep load, the matrix stress relaxes and the fiber stress increases. Upon specimen unloading, elastic contraction of the composite occurs, followed by a time-dependent decrease in fiber stress and increase in matrix stress. Overall, creep tends to increase the difference in stress between constituents and recovery tends to minimize the difference in stress. After Wu and Holmes.15... Fig. 5.1 Idealized representation of the transient change in fiber and matrix stress that occurs during the isothermal tensile creep and creep recovery of a fiber-reinforced ceramic (the loading and unloading transients have been exaggerated for clarity). It is assumed that the fibers have a much higher creep resistance than the matrix. The matrix stress reaches a maximum at the end of the initial loading transient. After full application of the creep load, the matrix stress relaxes and the fiber stress increases. Upon specimen unloading, elastic contraction of the composite occurs, followed by a time-dependent decrease in fiber stress and increase in matrix stress. Overall, creep tends to increase the difference in stress between constituents and recovery tends to minimize the difference in stress. After Wu and Holmes.15...

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See also in sourсe #XX -- [ Pg.433 ]

See also in sourсe #XX -- [ Pg.383 , Pg.388 ]




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Transient creep compliance function

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