E1C11 09/14/2010
13:14:2 Page 474
percentage error due to transverse sensitivity for a strain gauge mounted on any material at any
orientation in the strain field is
e L ¼
K t e L =e a þ y p0
À
Á
1 À y p0 K t
 100
ð11:12Þ
where
e a ; e L ¼ axial and lateral strains, respectively (with respect the axis of the gauge)
y p0 ¼ Poisson’s ratio of the material on which the manufacturer measured GF
(usually 0.285 for steel)
e L ¼ error as a percentage of axial strain (with respect to the axis of the gauge)
K t ¼ lateral (transverse) sensitivity of the strain gauge
The uncorrected estimate can be used as the uncertainty.
Typical values of the transverse sensitivity for commercial strain gauges range from À0.19 to
0.05. Figure 11.7 shows a plot of the percentage error for a strain gauge as a function of the ratio of
lateral loading to axial loading and the lateral sensitivity. It is possible to correct for the lateral
sensitivity effects (6).
10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10
Lateral sensitivity, K t (%)
Error % of axial strain
60
50
40
30
20
10
0
10
+
–
20
30
40
50
60
4
3
2
1
5
0
–3
–2
–1
0
1
2
3
4
5
–4
–5
–2
–3
–4
–1
–5= L / a
L / a =
L
a
Figure 11.7 Strain measurement
error due to strain gauge
transverse sensitivity.
(Courtesy of Measurements
Group, Inc., Raleigh, NC.)
474 Chapter 11 Strain Measurement