Viscoelasticity or creep is a typical time-dependent deformation of materials. To describe this material phenomenon, spring-dashpot model is widely employed. Figure shows four simple rheological models describing the viscoelastic behavior of materials. (Don't confuse dashpots here with sliders at plasticity.) 1) Write down the stress-strain-time relationships (constitutive equations) for the steady-state creep (a), and for the transient creep (b), respectively. 2) For the transient creep model (b), find the total strains at t=5sec and t=15sec, under the constant stress a=100MPA, respectively. (Material properties are given in Table 1.) 3) For the transient creep model (b), the constant stress o=100 MPa, is removed at the time t-5sec. Find the strain at the time t-10sec. a- constant ja) HW- (b) Table 1 Material properties for a viscous material E:=300GPA E2=200GPA n=1500GPA-sec n2=1000GPA-sec