Photoelasticity and stress

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In summary, the conversation is about using the photoelasticity technique to determine stress components on a window glass. The minimum amount of stress that can be detected using this technique is zero, usually at free boundaries. However, the exact amount of stress can be determined by counting the number of fringes and adjusting for the material thickness. Whether a force of 1 Newton will be detected or a bigger force is needed depends on the known stress difference and the material thickness.
  • #1
roy_lennon
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Hi,

I need to get the stress components on a window glass using photoelasticity technique.

How can I now the minimum amount of stress that can be detected using this technique?

Thanks!
 
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  • #2
You presumably know how to use the technique?

The minimum amount is zero, usually free boundaries.
 
  • #3
Hello

Let me modify the question..

If I apply a force of 1 Newton to the glass, will the stress be detected using photoelasticity?
Or do I need to apply a bigger force so it can be detected?
 
  • #4
This is a 'how long is a piece of string?' question.

The basic method gives the difference between the max and min principle stresses at any point by counting the number (n) of fringes (dark/ light transitions) from a point of known stress difference - hence my comment about free edges. there is, of course a material fiddle factor (f) you can juggle witht he thichness (t) to get any value you require.

[tex]{\sigma _{\max }} - {\sigma _{\min }} = \frac{{nf}}{t}[/tex]
 
  • #5


Photoelasticity is a powerful technique for determining stress distribution in materials, including in window glass. It involves the use of polarized light to visualize the stress patterns in a material. By analyzing the interference patterns in the polarized light, the stress components in the material can be determined.

To determine the minimum amount of stress that can be detected using photoelasticity, several factors must be considered. These include the sensitivity of the equipment being used, the thickness and material properties of the window glass, and the type and magnitude of the applied stress.

The sensitivity of the equipment is typically expressed in terms of the fringe order, which is the number of light and dark bands observed in the interference pattern. The higher the fringe order, the more sensitive the equipment is to changes in stress. Therefore, a higher fringe order will allow for the detection of smaller amounts of stress.

The thickness and material properties of the window glass also play a role in the minimum detectable stress. Thinner materials and materials with higher refractive indices will produce more distinct and sensitive interference patterns, making it easier to detect smaller amounts of stress.

Lastly, the type and magnitude of the applied stress will also impact the minimum detectable stress. Different types of stress, such as tensile or compressive, will produce different interference patterns, and larger magnitudes of stress will result in more pronounced patterns that are easier to detect.

In conclusion, to determine the minimum amount of stress that can be detected using photoelasticity, it is important to consider the sensitivity of the equipment, the properties of the material being studied, and the type and magnitude of the applied stress. By optimizing these factors, the minimum detectable stress can be determined for a specific application.
 

1. What is photoelasticity?

Photoelasticity is a method used to study the distribution of stress and strain in a material. It involves shining polarized light through a transparent material and observing how the light is affected by the material's internal stresses.

2. How does photoelasticity work?

Photoelasticity works by using a polariscope, which is a device that produces polarized light, and a polarimeter, which measures the changes in polarization of the light as it passes through the material. The changes in polarization can indicate areas of high stress concentration in the material.

3. What are the applications of photoelasticity?

Photoelasticity has many applications in the field of engineering, including stress analysis of structural components, evaluation of material properties, and design optimization. It can also be used in geology to study the stress distribution in rocks and other geological formations.

4. How is stress calculated using photoelasticity?

Stress is calculated using the principle of photoelasticity, which states that the difference in refractive index of stressed and unstressed materials is proportional to the applied stress. By measuring the amount of light that is polarized and the angle of polarization, the stress in the material can be calculated.

5. What are the advantages of using photoelasticity for stress analysis?

One of the main advantages of using photoelasticity for stress analysis is its high sensitivity to even small stress concentrations. It also provides a visual representation of stress distribution, making it easier to identify areas of high stress. Additionally, photoelasticity is a non-destructive testing method, meaning it does not damage the material being tested.

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