Today's treat: Frame rail crack at crossmember

[AriK]

The dreaded scraping years worth of grease looking for cracks took place today. Although it was relieving to find no cracks in the crossmember, i did uncover a crack in the frame rail at the crossmember. The crack is pretty accessible on the passengers side. Can a spot weld do the trick by a good welder and prevent the crack from spreading? If the crossmember has to be unbolted or dropped can the area be built up and still have enough clearance for the crossmember to fit against the frame rail? Somebody please advise on the best solution or most feasible solution.
Photo is viewed from timing belt cover toward inner fender looking down.

[azruss]

in needs to be welded and peened. I would also do a reinforcing plate on the top.

[AriK]

Thanks for responding azruss. Sorry for my ignorance, but what exactly is peening? Somebody will be looking at it tomorrow. He says no big deal if he has to drop the crossmember if it's to be done right. I seem to think otherwise, i was anticipating removal of the exhaust for better access would suffice...
It goes to show, no-rust cars are vulnerable as well, metal fatigue can lurk anywhere on our middle aged 30-48 year old cars.
Gotta get that and certain things sorted out before my 9.5 hour trek to FFO and safe return as well.

[RoyBatty]

I believe he is referring to a stress relief process.
I have only ever heard of shot peening in this manner.
This is where spheres or rounded rods of fine steel shot are shot using air pressure at a part that needs to be strengthened and relieved of stresses.
When you weld a part, you build up localized stresses in the parts you are welding

[wizard124]

Stop drill it. You drill a small hole at the leading edge of a crack. This spreads the stress in the material over a larger surface area which keeps the crack from growing.

[azruss]

when you weld a crack, you are heating the metal and the weld in a very localized area. When this cools, it cools in a crystaline matrix (ie: hot rolled). This means all the molecules align in nice neat rows making it more prone to cracking along these rows. To cure this problem, take a ball peen hammer (one with the rounded end) and start hammering away over the entire surface of the weld. Each stroke starts to deform all those nice little rows until they are no longer in nice rows but all the molecules have no orientation (cold rolled). Now you have eliminated the path for a fatigue crack to start and follow. The molecules will also move in a direction of less stress moving internal tensions out of the metal.

[AriK]

Thank you Roy, wiz and azruss, all three of you explained it in a way to make it easy to understand and it's all very logical.
I dropped in on a surprise visit to the welder today as i did not get a phone call as to indicate his intentions. He did what had to be done without the drama. However, he stopped welding upon my presence and quickly started working on another car. I guess i wouldn't want to be watched had it been me welding on a customer's car, i don't condemn him.
In any case i took a snapshot of what he had accomplished so far and i believe he beefed up the area pretty well. He welded a 90deg plate on two faces. It spans the surface area of the crossmember bracket. In fact he did such a good job he even welded the crossmember to the rail just so that i never have to deal with it again!!!
Just kidding about the last part
Let's hope that its rigidity doesn't overstress the driver's side rail. That side is not quite so accessible.