AnsweredAssumed Answered

Explanation for predefined Contact Resistance

Question asked by Doug Rawlings on Mar 4, 2015
Latest reply on Mar 18, 2015 by Doug Rawlings

Like • Show 0 Likes0
Comment • 8

Hi,

I'm using SolidWorks Flow to do some thermal modelling and I'm a little wary of the predefined contact resistances. Basically I'm looking for a clear explanation of what the descriptions mean.

For example:

"Aluminum, ground, air (Roughness 0,25 micrometer)"

Does this mean aluminium in contact with aluminium, both surfaces having a ground finish to 0.25 micrometres, assembled in air and therefore has air trapped in the cavities formed between the two surfaces?

Or is it aluminium in contact with the ground? (OK, unlikely)

Or is it aluminium in contact with air?

Or is it...

I've looked through the Help and can't find anything that tries to explain these. I'm reasonably happy that my first explanation is the relevant one but I don't like uncertainty.

Thanks for your help,

Doug.

No one else has this question

Outcomes

Bill McEachern Mar 4, 2015 9:25 AM

I would say its the first one. These things don't tend to make a huge difference as they tend to be quite thin. However, for some problems it does matter. In system level analysis I run without them as a first approximation. If things are close to being an issue I put them in and use something conservative.

Actions

Doug Rawlings @ Bill McEachern on Mar 4, 2015 9:51 AM

Bill,

Thanks for that. I also agree with your overall strategy but I'm working on something that is looking too close for that sort of simplification. And my customer seems to expect such things to be accounted for in any situation.

Thanks for the help,

Doug.

Actions

Jared Conway @ Doug Rawlings on Mar 5, 2015 2:11 AM

aluminum in contact with ground, 0,25 micrometer roughness, air filling the gaps

if your customer wants this level of fidelity, i'd ask them for the contact resistance that they want you to apply

Actions

Doug Rawlings @ Jared Conway on Mar 16, 2015 2:30 PM

Jared,

Thanks for the reply and I apologise for being so late in looking at it, I don't have ready access to the Internet at the moment.

I'm afraid your answer has thrown me a bit. When you say "aluminum in contact with ground", what do you mean by ground? I would normally interpret that to be either a) ground, earth, dirt b) the floor or c) electrical ground. And that's kind of one of the interpretations I'd started with but didn't make sense to me.

Unfortunately in this case the client doesn't have much more of a clue than me! Or at least I've not found that person yet. I work as a contractor and have been cornered into doing this (since I admitted to knowing a bit about SolidWorks Flow). The one person who does this sort of thing regularly said to use the pre-defined contact resistance for aluminium (without specifying which one) but I'm trying to understand things a bit better than that.

If you can give a bit more detail on what you mean by ground then it would be appreciated,

Regards,

Doug.

Actions

Jared Conway @ Doug Rawlings on Mar 17, 2015 2:43 AM

now that I read it again, I think ground means ground surface finish

Actions

Doug Rawlings @ Jared Conway on Mar 17, 2015 8:27 AM

Hi Jared,

Ah, that's good that we all seem to have come to the same conclusion. Although the confusion shows how badly worded the original description is, especially when it's caused someone with your experience to have to look at it twice.

Thanks Bill and Jared for your help, and to anyone else who looked at this question.

Doug.

Actions

Jared Conway @ Doug Rawlings on Mar 18, 2015 1:20 AM

what will probably really boggle your mind is what should you choose if you have 2 different materials?

Actions

Doug Rawlings @ Jared Conway on Mar 18, 2015 11:43 AM

I'm trying not to think about that...

Actions

8 Replies

Bill McEachern Mar 4, 2015 9:25 AM
Mark Correct
Correct Answer
I would say its the first one. These things don't tend to make a huge difference as they tend to be quite thin. However, for some problems it does matter. In system level analysis I run without them as a first approximation. If things are close to being an issue I put them in and use something conservative.
Like • Show 2 Likes2
Actions
- Doug Rawlings @ Bill McEachern on Mar 4, 2015 9:51 AM
  Mark Correct
  Correct Answer
  Bill,
  
  Thanks for that. I also agree with your overall strategy but I'm working on something that is looking too close for that sort of simplification. And my customer seems to expect such things to be accounted for in any situation.
  
  Thanks for the help,
  
  Doug.
  Like • Show 0 Likes0
  Actions
  - Jared Conway @ Doug Rawlings on Mar 5, 2015 2:11 AM
    Mark Correct
    Correct Answer
    aluminum in contact with ground, 0,25 micrometer roughness, air filling the gaps
    
    if your customer wants this level of fidelity, i'd ask them for the contact resistance that they want you to apply
    Like • Show 0 Likes0
    Actions
    - Doug Rawlings @ Jared Conway on Mar 16, 2015 2:30 PM
      Mark Correct
      Correct Answer
      Jared,
      
      Thanks for the reply and I apologise for being so late in looking at it, I don't have ready access to the Internet at the moment.
      
      I'm afraid your answer has thrown me a bit. When you say "aluminum in contact with ground", what do you mean by ground? I would normally interpret that to be either a) ground, earth, dirt b) the floor or c) electrical ground. And that's kind of one of the interpretations I'd started with but didn't make sense to me.
      
      Unfortunately in this case the client doesn't have much more of a clue than me! Or at least I've not found that person yet. I work as a contractor and have been cornered into doing this (since I admitted to knowing a bit about SolidWorks Flow). The one person who does this sort of thing regularly said to use the pre-defined contact resistance for aluminium (without specifying which one) but I'm trying to understand things a bit better than that.
      
      If you can give a bit more detail on what you mean by ground then it would be appreciated,
      
      Regards,
      
      Doug.
      Like • Show 0 Likes0
      Actions
      - Jared Conway @ Doug Rawlings on Mar 17, 2015 2:43 AM
        Mark Correct
        Correct Answer
        now that I read it again, I think ground means ground surface finish
        Like • Show 1 Like1
        Actions
        Doug Rawlings @ Jared Conway on Mar 17, 2015 8:27 AM
        Mark Correct
        Correct Answer
        Hi Jared,
        
        Ah, that's good that we all seem to have come to the same conclusion. Although the confusion shows how badly worded the original description is, especially when it's caused someone with your experience to have to look at it twice.
        
        Thanks Bill and Jared for your help, and to anyone else who looked at this question.
        
        Doug.
        Like • Show 0 Likes0
        Actions
        Jared Conway @ Doug Rawlings on Mar 18, 2015 1:20 AM
        Mark Correct
        Correct Answer
        what will probably really boggle your mind is what should you choose if you have 2 different materials?
        Like • Show 0 Likes0
        Actions
        Doug Rawlings @ Jared Conway on Mar 18, 2015 11:43 AM
        Mark Correct
        Correct Answer
        I'm trying not to think about that...
        Like • Show 1 Like1
        Actions

Explanation for predefined Contact Resistance

Outcomes

Related Content

Recommended Content