Rear Upper Toe Control Arm Cracks
#19
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alpinaturbo (Jan 3, 2019)
#22
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Grinding produces a damage layer in the remaining material that is more prone to crack initiation, so while the local stress riser is removed by grinding, a new weakness is produced. Its a "damned if you do, damned if you don't" situation.
#23
I said sanded with a flap wheel on a die grinder. Not grinding. Don't go into the main forging, just remove the riser. Properly done, it will certainly reduce the stress riser from what's shown in the pictures. This procedure is done on factory forged steel connecting rods all the time.
#24
It's a flash line crack. Basically a forging defect. Removing the bit of flashing won't change anything.
And grinding or sanding is the same thing. You're removing material with abrasion. Whether its a sanding disk, grinding wheel, or carbide burr. The only difference is the size of the chips coming off the part.
And grinding or sanding is the same thing. You're removing material with abrasion. Whether its a sanding disk, grinding wheel, or carbide burr. The only difference is the size of the chips coming off the part.
#25
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From: Tri-Cities, WA // Portland, OR
I said sanded with a flap wheel on a die grinder. Not grinding. Don't go into the main forging, just remove the riser. Properly done, it will certainly reduce the stress riser from what's shown in the pictures. This procedure is done on factory forged steel connecting rods all the time.
LGTD, I wouldn't call that a flash line crack in the sense of forging. However its possible that the microstructure in that region is less optimal due to it perhaps being a last-to-solidify region that would contain more insoluble or lower melting point elements.
Last edited by mrfred; Jan 15, 2019 at 05:34 PM.
#26
i dont think its a forging defect...
i think the end starts out as a U and is forged into a O.... with a very small gap where the tips of the U touch...
then they are welded.
stress fracture on the weld.
i think the end starts out as a U and is forged into a O.... with a very small gap where the tips of the U touch...
then they are welded.
stress fracture on the weld.
#27
It's not a forged piece, there is no weld. The entire piece is cast as it looks and both bores are machined to properly fit the bushing and ball joint. The line that is the cause of this issue is a parting line, it's essentially excess material that was squeezed out between the mold halves. You can tell it's a cast piece the same way you would a crankshaft, by looking at how thin the parting line is. Forged pieces usually have a parting line that's about 0.5-1" in width, while cast parts are thinner like this (usually 1/16-1/8").
#28
Was also a bit confused by these alum suspension arms & beams & how they are made
Are they forged or just a simple sand casting? Heres a snip from Mitsubishi's EvO announcement from Cypress CA
Heres the article for verification:
http://media.mitsubishicars.com/rele...6fbed?page=142
Are they forged or just a simple sand casting? Heres a snip from Mitsubishi's EvO announcement from Cypress CA
Heres the article for verification:
http://media.mitsubishicars.com/rele...6fbed?page=142
#29
Forging is a very vague term and is often misused in marketing material. It is probably cast and ran though a forging press while still hot and finally annealed in an oven. That's pretty typical for lots of mass produced aluminum parts.
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mrfred (Jan 16, 2019)
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