Civil Engineering Reference
In-Depth Information
Table 9.6
Stationary
electrical test temperatures
(6.35-mm-diameter surface
ground specimens) [
6
]
Force
(N)
Time
(s)
Temperature
(°C)
Δ
T (% of baseline
Temp at 2,376 N)
5
418.7
100.0
2,376
10
507.7
100.0
541.8
100.0
15
5
393.0
93.9
3,564
472.5
93.1
10
505.2
93.2
15
4,753
5
386.6
92.3
10
464.2
91.4
496.7
91.7
15
5
350.6
83.7
5,941
427.7
84.3
10
463.1
85.5
15
7,129
5
331.9
79.3
405.1
79.8
10
15
438.3
80.9
Fig. 9.16
Stationary
electrical temperatures
(6.35-mm-diameter surface
ground specimens) [
6
].
The linear-inverse relation
between temperature and
static load is also apparent
for the larger specimens due
to all of the static loads only
being in the elastic region
100
All loads in the
elastic region
.
95
90
85
After 5s
After 10s
After 15s
80
75
0
2000
4000
6000
8000
Static Load (N)
9.1.6 Voltage-Resistance Contact Area Model
The voltage (in mV) was recorded for each of the stationary electrical tests using
a digital multi-meter, as shown in Sect.
9.1.4
. Since the voltage is related to the
actual contact area, the voltage measurements can provide a dynamic confirma-
tion of the asperity crushing due to an increase in the static load. Figure
9.17
below depicts the voltage measurements obtained during stationary electrical tests
under various static loads for 4.76-mm-diameter surface ground specimens and
for 4.76-mm-diameter “Large CA” specimens. The “Large CA” specimens show
a notable decrease in the measured voltage at the first two static loads, and then
show the same level effect as the surface ground specimens (although the “Large
CA” specimens still have a higher voltage value). The higher voltage value is to
