How To Calculate Strains; Method Of Calculation Applicable To Strain Gage - KYOWA DPM-900 Series Instruction Manual

9-3 HOW TO CALCULATE STRAINS

This section describes how to measure strains and stress.

9-3-1 Method of Calculation Applicable to Strain Gage

Suppose that a strain waveform as shown at right was
obtained. The diagram shows a positive (+) calibration
signal value recorded at the top of the waveform.
Suppose that the direction of this calibration signal
waveform shows the direction of "elongation."
The time factor of the strain waveform can be obtained
referring to Tc (i.e. an interval between one time-maker
and another).
Various values can be obtained as follows from the right
figure.
1)
Calculating the maximum strain
Measure the respective heights of the calibration signal and the maximum strain from the base line of
zero by using a scale.
Suppose that a measurement of
calculated using the equation below.
is in the same direction as +
m
When once the strain
stress system) can be found using the equation below.
However, E is Young's modulus of the measuring point and the gage axis is considered as attached
according to stress axis direction.
Therefore, the maximum stress
2) Calculating strain ´
Strain ´ is in the direction opposite to +
m
Suppose that the height of ´
Stress ´ (provided that it is of the monoaxial stress system) is calculated using the equation below.
m
3) Time from the start point of the strain waveform to the maximum strain
To calculate T (i.e. time from the start point to the maximum strain), use the time maker. Measure 10 or
1
so intervals between time makers, and obtain their average, then t
measurement of T
and the maximum stress
m
is h [mm], and that of
c c
. Therefore it is "elongation."
c
has been obtained, stress
is obtained by the following equation.
m
and stress ´
m m
is h´ [mm], the amount of ´
m m
is t [mm]. T can be calculated using the equation below.
1 1 1
Calibration Wavaform
(CAL)
.
m
is h
m
at that point (provided that it is of the monoaxial
. Therefore it is "construction."
c
can be obtained using the equation below.
m
46
Zero Baseline
Time Maker
[mm]. The maximum strain
m
[mm] against time T
c
Waveform of Measuring Variable
can be
m
. Suppose that a
C