Question 3 (20 points): A 40% tin, 60% lead alloy solder wire of 3.15mm diameter is subjected to creep by hanging weights from lengths of the wire. Length changes were measured over a 254mm gauge length after various elapsed times (see table below) for three different weights.
(a) Plot the family of strain vs time curves.
(b) Characterize the behavior. Is it dominated by either transient or steady-state creep, or do significant amounts of both occur?
(c) Determine steady-state creep rates (sc) for each value of weight and plot these in log-log coordinates vs the corresponding stresses. Does a straight line provide a reasonable fit to the data? If so, find values of constants B and m for the relationship c = Bo.
Table P15.2:
Length change (mm)
Time (min) 4.54 kg 6.80 kg 9.07 kg
0 0 0 0
0.25 0.28 0.46 0.69
0.5 0.36 0.66 0.94
1 0.48 0.91 1.45
2 0.71 1.40 2.36
4 1.09 2.24 4.09
6 1.47 3.00 5.72
8 1.83 3.38 7.26
12 2.54 4.90 10.41
16 3.23 6.38 13.64
20 3.91 7.82 16.74