We are measuring the surfaces pre and post braze, and there isn’t much different, and the flatness is pretty good; basically about the same as the machined components. As soon as we apply vacuum, some critical surfaces are displaying deflection.
We are using a copper-gold alloy and although the...
@FennLane
The assy is a rectangular cavity with specific features (openings) at given wall thicknesses so we can measure deflections with typical QA instruments. As I mentioned, we also confirm the deformation with frequency measurements as the cavity volume is sensitive to frequency shifts...
@Ed
These are box-like assys and not completely symmetric, so although the entire assy is copper, I totally agree the thermal expansion along a particular direction will not be exactly the same as another and could cause some residual stress. The braze is implemented in a batch furnace and...
@MagBen
See if this helps. I am interested in E at elevated temperatures and here is why. It is common to first run a static linear FEA model to confirm linear elastic region. I think we all agree that E (and PR) are the only material properties used (mathematically) for elastic models. The...
Good discussion; thank you all for the comments.
One more response to hopefully wrap this up. I should have mentioned this not a wire or some small piece with clear deformation, but a machined cavity assy which is operated under vacuum; like a copper waveguide. We braze this stuff all the time...
Thanks Compositepro; I really appreciate all the comments.
So I understand a linear FEA model requires only elastic modulus and poisson’s ratio for stress distributions, displacements, etc. And if the stress ends up exceeding the YS of the material then the model is non-linear and additional...
And I should add I understand this whole E thing is based on Hooke's Law,small delflections and whatnot; the problem is running an FEA model with higher values of E indicate very little deflection, whereas empircal measurements indicate different. So considering if the E value realistically is...
Thanks EdStainless.
If I recall, aren’t deflection calculations dependent of E?? Changing the YS will not affect the deflection results, at least not in my simple model. Just looking at simple beam deflection formulas, no strength values, just E….
I am using ~4500 psi for YS which is...
Thanks for response.
My belief is some analysts (for brazing) are using an incorrect E. I agree the value of E for typically annealed copper (like CF gaskets or home wire) are basically the same at 15E6. But running Cu just below the melting temp, which is common in H2 brazing, the copper...
Hello-
I am running a simulation of a simple brazed copper assembly; brazed at 1050°C. I believe the Young's Modulus will drastically change after brazing at this temperature since the annealed state is "dead soft". My analyst colleague is using an annealed value for E of 15E-6 psi, which...
