Question

plastic

7. For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with time according to o(t)-σ(0) exp(-- where o(t) and o(0) represents the time-dependent and initial (i.e., time -0) stresses, respectively, and t and τ denote elapsed time and the relaxation time, τ is a time-independent constant characteristic of the material. A specimen of some viscoelastic polymer with the stress relaxation that obeys the above equation was suddenly pulled in a tension to a measured strain of 0.6; the stress necessary to maintain this constant strain was measured as a function of time. Determine E(8) for this material if the initial stress level was 2.69 MPa, which dropped to 1.78 MPa after 59 s 1-72 276 MP 60

Answer 1

iven stess level sMe afl 59 s at Rane S1 S polen the stus de Cau AcCadg t6 t て 1-18 = 2.61 exp ( 兴. er(끝) 1.78 2 .b9 2-69 で (o E o

The Value(an be ev th equa hen e- (42.83 2.61 (0.quss 21S435 c(8) S43s 6.(o