describe the phenomenon of viscoelasticity.

 

1. In your own words, briefly describe the phenomenon of viscoelasticity.

2. For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with time according to

 

where (t) and (0) represent the time- dependent and initial (i.e., time = 0) stresses, respectively, and and τ denote elapsed time and the relaxation time, respectively; τ is a time- independent constant characteristic of the material. A specimen of some viscoelastic polymer the stress relaxation of which obeys Equation 15.10 was suddenly pulled in tension

to a measured strain of 0.6; the stress necessary to maintain this constant strain was measured as a function of time. Determine Er(10) for this material if the initial stress level was 2.76 MPa (400 psi), which dropped to 1.72 MPa (250 psi) after 60 s.

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erive the differential equations in terms of the liquid heights h1 and h2.

  Figure 7.18 shows a liquid-level system in which two tanks have cross-sectional areas A1 and A2, respectively. The volume flow rate into tank 1 is qi. A pump is connected to the bottom….

Derive the differential equation relating the liquid height h and the volume flow rate qi at the inlet.

  Consider the single-tank liquid-level system shown in Figure 7.19, where the volume flow rate into the tank through a pipe is qi. The liquid leaves the tank through an orifice….

Derive the differential equations in terms of the liquid heights h1 and h2.

Figure 7.20 shows a hydraulic system of two interconnected tanks that have the same cross-sectional area of A. A pump is connected to tank 1. Assume that the relationship between the….