A plastic was stretched initially from 30 mm to 35 mm and then released at room temperature. The length changes with time were obtained as the following. Assume the Voigt model can be applied for this mechanical behavior.
Time (hr) - 0, 1, 3, 7.5, 12
Length (mm) - 35.000, 32.509, 30.632, 30.113, 30.028
A) What is the retardation time (hours)?
B) What is the strain (%) after 75 minutes?
C) What percent of the initial strain is recovered after 75 minutes?
D) How long does it take for 50% of the strain to be recovered?
E) If the test was made at body temperature, would you expect the recovery to be faster, slower, or the same compared to the room temperature test?