slip fit with bonding on 3AL2.5V titanium to 7075 aluminum non andized

[dwx]

I have a cylindrical assembly that I need to bond together. One side is a thin walled 3AL 2.5V tube, the other side wil be 7075 alloy. I would prefer to anodize the 7075 throughout, but I can have the outer edges masked. My diameter between my slip fit parts is roughly 32mm. My depth is about 23mm. I can hold close tolerances. I was planning on a light press fit with a bonding agant.

The assembly will see mainly radial loads, but I do have an overhanging load that will be no more than 1400 lbs. My stresses are cyclic and could be reversed also.

I talked with a Loctite tech supprt engineer, and they suggested loctite 609. I have had a lot of luck with this type of bonding agent, but I would prefer to use 638 for its higher strength. Loctite admittedly hadnt tested this, so their suggestion was a guess.

Anyone out there with a similar situtaion or another adhesive that can give me over 3000 psi shear on aluminum?

Also, I was planning on calling out a 64 RMS finish on my parts. Anyone have a suggestion as to whether this can work for me r not?

Thanks

Dave

http://www.dw-link.com

 

[israelkk]

We had 7075 corrode wile waiting between the different steps of machining at the factory, we had to oil it while it was waiting for the next machining step. It is much cheaper to anodize the complete part and then machine the the surfaces than use masking.

From my understanding when using a glue a minimum gap between the parts is needed therefore, press fit will remove the glue in the process.

 

[dwx]

See, the problem with anodizing the entire part is that when I anodize the bonding surface, I reduce the cure strength and increase the bond time with the Loctite urethane retaining compound. The glue doesn't stick to the anodization very well. In reality, it only gets to about 75% of the compressive sher strength on aluminum that it does on steel, so I am already hurting.

This is why I am looking for other bonding options. Ideally I would like a bonding agent that will stick to anodized surfaces and provide above 3000psi compressive shear strength with a light press fit.

My application is extremely weight critical, so I would prefer not to replace the 7075 part with stainless. My only other option is to substitute 2024 for 7075, which could help in the corrosion area.

Any help is really appreciated.

Thanks!

Dave

http://www.dw-link.com

 

[israelkk]

Why would 2024 better? Did you considered anodize without the sealing (in water of dichromate) as it is an excelent base for painting. However, you have to glue the parts immediately after anodize otherwise the anodized surfaces will accumulate moisture from the air (kind of natural sealing).