Increasing a coefficient of friction between 2 surfaces 3

[elinah34]

Hello,

A colleague told me about a problem they had and how they decided to solve it, and I would like to find out what you think about it.
His crew designed a chamber (see a simplified picture below) that is expected to be flown and subjected to varied loads and vibration.

After getting all the parts and starting assembling they found out that the Safety Of Factor for side slippage (relative movement in x and/or z directions between both clamped parts of the chamber) is very small and marginal.
Since adding bolts (for increasing clamping force) was problematic, they decided they are going to increase the coefficient of friction between both clamped parts. They decided (without any experiment)to grit blast the mating surfaces like presented in the picture below.

I have several problems with their decision:
1. they damage the Hard Anodize surface treatment that should protect from corrosion, and abrasive grit blast would expose the aluminum.
2. they didn't really explored how much the coefficient of friction is increased and if it's worth it.
3. maybe there are more elegant solutions? maybe there is a specific surface treatment or coating that on one hand might increase the friction coefficient and on the other hand protect the metal from corrosion?

what is your opinion?

thanks!

 

[elinah34]

JStephen, did you hear about such solution before?
What about ruining the surface treatment and leaving the metal exposed to environmental effects?

 

[elinah34]

Scuka
You are right, but in this case they will have to make sure that 2 pins and hole and slot might bear the loads without failing.

 

[elinah34]

MintJulep and LittleInch
Thanks for replying, you raised good points and questions. I don't have a lot of information since I am not familiar with all the details of this project. I just heard about their solution and wanted to know if anyone has heard of such a solution before.

 

[Scuka]

You are right, but in this case they will have to make sure that 2 pins and hole and slot might bear the loads without failing.

The way I understood the problem, there's friction holding the two parts in place, but you're worried that the friction is not quite enough.

If you use pins, the friction will still be there doing its job. The load the pins are going to bear will be equal to the total load on the part minus friction. And since friction is ALMOST enough to do the job, the remaining load shouldn't be that high.

Or am I misunderstanding something?

 

[hydtools]

Use a band clamp on the flange OD.

Ted

 

[Artisi]

Change the design, have one flange a smaller OD and a spigot register on the other flange.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[elinah34]

Scuka
You understood well and it seems to be you are right.