- This strain rosette calculator is purely intended for education purpose only.
- Any commercial use should be checked by qualified engineer and should be used on the users risk.
- Find Mohr’s circle and principle stress calculator here.
What is a strain gauge
Strain gauge is a device which measures strains induced in an object by measuring the electrical resistance across a thin conductive foil.
A typical strain gauge consists of gauge backing on which the resistive foil is placed.
The gauge backing is placed on the material whose strain under a loading has to be tested.
When load is applied the cross section of the conducting wire changes and thus the resistance changes.
This change in resistance is correlated to strain using the gauge factor of the strain gauge.
The resistance in a strain gauge is measured using a Wheatstone bridge.
A Wheatstone bridge is used to for measurement of unknown resistance.
The Wheatstone bridge setup is very simple with Rx being the unknown resistance, two known resistance values (R1 and R2) and a variable resistance (R3).
The output voltage is given by the following equation:
For a balanced Wheatstone bridge the output voltage is 0. This is achieved by varying the variable resistance R3, till the output voltage is achieved as 0.
Further the unknown resistance is given by the ratio:
R1/R2 = Rx/R3
Types of strain rosettes
Delta rosette is a configuration of 3 strain gauges where each strain gauge is at 60 degrees apart from each other.
The configuration can be either in equilateral triangle format or in open configuration.
First strain gauge is at an angle of 60 degree, second strain gauge at 120 degree and third strain gauge at angle 180 degree.
Rectangular rosette is a configuration of strain gauge in which each stain gauge is separated by an angle of 45 degree.
Hence the angle of first strain gauge is 0 degree, 2nd strain gauge is at angle of 45 degree and third strain gauge is at an angle of 90 degree.
How to use calculator
- Choose the type of strain gauge from dropdown. This step is not compulsory however if type of strain gauge is selected it automatically defined the angles for the strain gauges.
- Input the strains measured by strain gauges. The calculator only allows 3 strain gauge rosette configuration and hence only 3 strain measurements can be input.
- If type of strain gauge is not defined in first step, then the angles have to be input manually by the user.
- In result section the strain in X direction, Y direction and shear strain is calculated.