Strain Gauge Placement on Cylinder

[tmcalexander]

1. Problem Statement: I am trying to measure the radial (#s 3-6) and hoop (#s 1, 2, 7, 8) strain (and from that, stress) present in an aluminum cylinder. I am trying to use a standard full wheatstone bridge setup, but am having trouble settling on a setup that would give me an accurate measurement. I haven't tried my current setup yet as I want to be reasonably sure that it will work before using my given materials since they are relatively limited. Can anyone offer any constructive criticism or help?



2. Homework Equations : N/A



3. The Attempt at a Solution : see attached picture

 

[tmcalexander]

Also, I forgot to mention that the cylindrical system is a shrink-fit system, with dimensions as shown in the picture. One of my main problems is trying to compensate for the gradient imposed by the boundary between the surfaces.

 

[Mene]

I would suggest the following approach to accurately measure the radial and hoop strain on the aluminum cylinder:

1. Consider the material properties of the aluminum cylinder: Before designing the strain gauge placement, it is important to understand the material properties of the cylinder such as its Young's modulus, Poisson's ratio, and yield strength. This will help in selecting the appropriate strain gauge and determining the expected strain values.

2. Determine the type of strain gauge: There are different types of strain gauges available, such as foil, semiconductor, and piezoelectric. Based on the material properties of the aluminum cylinder, select the most suitable strain gauge that can accurately measure the expected strain values.

3. Consider the geometry of the cylinder: The placement of the strain gauges should take into account the geometry of the cylinder. For accurate measurement, it is recommended to place the strain gauges at equal distances from each other along the circumference of the cylinder.

4. Use a full Wheatstone bridge setup: As mentioned in the problem statement, using a full Wheatstone bridge setup is a good approach. However, make sure to carefully select the resistors and strain gauges to achieve the desired sensitivity and accuracy.

5. Consider the location of the strain gauges: For measuring radial strain, the strain gauges should be placed at right angles to the cylinder's axis. For measuring hoop strain, the strain gauges should be placed parallel to the cylinder's axis.

6. Perform a calibration test: Before using the setup for actual measurements, it is important to perform a calibration test to ensure the accuracy of the readings. This can be done by applying known loads or stresses and comparing the measured strain values with the expected values.

Overall, it is important to carefully consider the material properties, geometry, and placement of the strain gauges to accurately measure the radial and hoop strain on the aluminum cylinder. Additionally, performing a calibration test and using a suitable strain gauge will also help in achieving accurate results. I hope this helps and wish you success in your experiment.