Designing with Thermal expansion in mind

In summary, the conversation discusses the thermal expansion coefficients of stainless steel and epoxy, and the potential for stress and breakage when combining the two materials. The speaker also asks for advice on how the expansion will occur and suggests using a buffer material to absorb the difference. Additionally, they inquire about alternative epoxies with a closer coefficient to stainless steel.
  • #1
_Bd_
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Hi, I am trying to design a tubular probe that's made of stainless steel (304), from what I've read it has a Thermal expansion coefficient of around 9.6 x10^-6 in/in/F give or take on the quality.

I want to fill this tube halfway with an Epoxy, however from what I've read this epoxy has a thermal expansion coefficient of 21 x10^-6 in/in/F

This is more than twice as much expansion, and I'm worried that it will create stress in the part and might even break it.

However, what I want to know is if the expansion would happen side-ways given that it will be inside the tube and taking the shape of the container, I would hope that it would expand upwards mostly, since it would be limited on all other sides. I am not too sure about how things expand when restrictions are applied.

Please advice and thank you!

(Also if you know of some other epoxy that's RoHS and closer to the coefficient of SS that would help as well)
 
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  • #2
_Bd_ said:
Hi, I am trying to design a tubular probe that's made of stainless steel (304), from what I've read it has a Thermal expansion coefficient of around 9.6 x10^-6 in/in/F give or take on the quality.

I want to fill this tube halfway with an Epoxy, however from what I've read this epoxy has a thermal expansion coefficient of 21 x10^-6 in/in/F

This is more than twice as much expansion, and I'm worried that it will create stress in the part and might even break it.

However, what I want to know is if the expansion would happen side-ways given that it will be inside the tube and taking the shape of the container, I would hope that it would expand upwards mostly, since it would be limited on all other sides. I am not too sure about how things expand when restrictions are applied.

Please advice and thank you!

(Also if you know of some other epoxy that's RoHS and closer to the coefficient of SS that would help as well)

Depending on the application, you can use a buffer material between the epoxy and the SS to absorb the difference in thermal expansion. We have used Sylgard for this application in the past with good results (it's a softer polymer that is used for mechanical buffering in electronic applications):

http://www.dowcorning.com/applications/search/products/details.aspx?prod=01064291
 
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1. What is thermal expansion in design?

Thermal expansion in design refers to the changes in size or dimensions of a material due to changes in temperature. When a material is heated, its molecules vibrate and take up more space, causing the material to expand. Similarly, when a material is cooled, its molecules contract and the material shrinks. This phenomenon can have significant impacts on the design and functionality of structures and components.

2. Why is it important to consider thermal expansion in design?

It is important to consider thermal expansion in design because it can cause structural and functional issues if not properly accounted for. If a material expands or contracts too much due to temperature changes, it can lead to warping, cracking, or even failure of the structure or component. By considering thermal expansion in the design phase, engineers and designers can ensure that the materials and components used are able to withstand the expected temperature changes without compromising the integrity of the design.

3. How do you account for thermal expansion in design?

There are a few ways to account for thermal expansion in design. One approach is to use materials with low coefficients of thermal expansion (CTE), meaning they expand and contract less with temperature changes. Another method is to incorporate joints or gaps in the design to allow for expansion and contraction without causing damage. Additionally, simulations and calculations can be used to predict the expected amount of thermal expansion and design accordingly.

4. What types of materials are most affected by thermal expansion?

Materials with a high coefficient of thermal expansion, such as metals and ceramics, are most affected by thermal expansion. These materials tend to expand and contract significantly with changes in temperature, which can pose challenges in design. However, it is important to consider thermal expansion for all materials, as even materials with low CTE can still experience changes in size with temperature fluctuations.

5. How do you test for thermal expansion in design?

There are several methods for testing thermal expansion in design, depending on the specific material and application. Some common methods include thermal expansion coefficient measurements, thermal cycling tests, and finite element analysis simulations. These tests can help determine the expected amount of expansion and contraction for a given material and design, allowing engineers to make any necessary adjustments to ensure the design is suitable for the expected temperature changes.

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