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Next, given that the strain as a function of time during the creep test using a unit step stress function for the model shown in Figure 1 is described as: Oo e(t) = E = ):(1-67 Bet) E2 .e E1 + E2 where creep time constant (T ) is expressed as: n n T= + E1 E2 and the stress as a function of time during the stress relaxation test using a unit step strain function described as: o(t) = £o (E1 + Eze +Eze ) where relaxation time constant (T) is expressed as: n T = E2
Given E1 35 GPa, Ez 28 GPa, n = 140 GPa.s c) Sketch the strain vs time response for a creep test. The stress o = 30 MPa is applied at t = O and held constant for t1 = 140 seconds (as shown in the below figure). [Excel can be used for plotting) 0. to ti 1. Calculate the value of creep time constant. 2. What is the strain response at t = 0 3. What is the strain response at t1 4. What is the strain response at t = 0