Cracked alloy

[johnsco]

In the work that I do, we're crack-testing fome Formula 1 wheels this week.
Beautifully-engineered, unbelievably-thin sections and incredibly-light.
We're X-raying them, as they are coated with a laquer which would need removing to dye-penetrant test them.

This led to a discussion, arising from this thread about weld repairs to alloy wheels.
Unknown to me (I don't work on the X-ray side of the business), we recently X-rayed a weld-repair in an alloy wheel.
Guess what we found ........ It was cracked.
Wheel went back to the repairer, where the words "We repair hundreds of these" were spoken.
Repair was re-welded and came back to us for a further X-ray.
It was still cracked.
You can make yourself very unpopular in our job !!

Cheers.
Johnsco

 

[hotrodder]

Hey John,
Any chance of some details regarding the cracks? Liquation cracks in the HAZ or subsurface centreline cracks possibly from incomplete penetration/lack of fusion etc. Much porosity? Pic of the x-ray would be even better if it's possible

Just curious
Cheers

 

[merc man]

WOW. i have also just had the same issue on my w203. i had put a new set of alloys on the car after i got it and have driven it with car and attention, but when i came to clean the wheel i took it off and when i finished cleaning i could see this crack going down the side just like yours bit mine also went in to the inner part of the wheel and that was on a friday by monday there was a new alloy on the car and the old one is at the welders getting welded and then im going to use it as a spare!

 

[Les]

I had the same problem on a set of aftermarket alloys on a mitsubishi GTO I used to own. My local alloy wheel centre did a weld repair and checked wheel for ovality. They said it was something they did quite often. When a second crack appeared then a third 3 months later on the opposite side of the rim it was definately time for a new set of alloys.

Les

 

[johnsco]

Hi Hotrodder
Unfortunately I don't work on the X-Ray side of the business.
Most of my work is ultrasonics.

I didn't see the graphs.
They are usually given to the customer when we have done the job.

I understand that the crack was lack of fusion between the weld metal and the parent material.
I understand that it was a simple L.O.F. with no evidence of porosity

Sorry can't be more specific.

I am not saying - Don't do this in any circumstances.
With an older design of wheel, you may not have much option but to repair.
The important thing is that the repair should be done by a specialised welder who knows the techniques to use and their limitations.

I would then strongly suggest dye-penetrant testing AND X-Ray testing of the repair.
The two tests actually find different types of defects.

If you really need to be sure, I would then recommend re-examination periodically to ensure that cyclic stress caused by use has not cracked the wheel again.
Some aluminium alloys "age" and this can cause failure, even without the added complications of weld repairs.

Because of the very thin metal section thicknesses on racing vehicles, periodic nondestructive testing of critical components is the norm.

Cheers.
Johnsco