User`s guide
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Similarly, in the axial direction, the pressure acts to push the two halves apart, while axial stress balances
the effects, as shown in figure 3. The axial stress yields,
The Hooke’s Law states that stress in the can is proportional to the strain. The relationship in this case can
be expressed as:
where E is Elastic Modulus of the material, and is Poisson’s ratio of the material.
With Eq.2, Eq.4, and Eq.5, the relationship between pressure and strains can be derived as:
2.3 Basics of Strain Gages
2.3.1 Operating Principle and Application of Strain Gages
Strain-gauge sensor is one of the most commonly used means of load, weight, and force detection. Strain
gauges are frequently used in mechanical engineering research and development to measure the stresses
generated by machinery, and in Aircraft component testing to structural measure stress of members,
linkages, and any other critical component of an airframe.
A strain gauge operates on the principle that the electrical resistance of a wire changes when the length of
the wire varies. It is used for measuring deformations in solid bodies. The strain experienced by the
sensor is directly proportional to the change in resistance of the gauge used, as shown in Eq 7.When
unstressed, usual strain gauge resistances range from 30 Ohms to 3 kOhms.
An ideal strain gage is small in size and mass, low in cost, easily attached, and highly sensitive to strain
but insensitive to ambient or process temperature variations. The ideal strain gauge would undergo
change in resistance only because of the deformations of the surface to which the sensor is coupled.
However, in real applications, there are many factors which influence detected resistance such as
Eq.5
Eq.6
Eq.7
Eq.3
Eq.4