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Discussion Starter #1 (Edited)
My wheeling buddy broke his tie-rod this past weekend, which seemed odd because the material was 7077, per the owner of the shop that made it. It just looks like the molecules stopped wanting to be attached. This unit was never overly bent or tweaked and the rig it is on does not wheel real stupid trails.

Any idea/input on the break? Any more info needed?

Pic One (copy and past needed for some reason...)
http://image60.webshots.com/660/0/20/64/2011020640057160246qjtzcy_fs.jpg

Pic Two
 

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Looks like a 7 series fracture to me. The yeild and sheer are really close in the 7 series alloys. Possibly a past impact stress riser that has been in the micro fracture process for a while. what was the Diameter of that rod.

wayne
 

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I dont have any useful input on the tierod but when you zoom in on the first pic you can see that his panhard bar mount is starting to crack down on the axle side.
 

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Can you get an infocus shot of the failure? Both sides if possible.

ZachV, if you are really really curious, PM me, I'm a mechanical engineer and work at a metalurgy lab, I might be able to do some actual testing after hours.
 

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Looks like a 7 series fracture to me. The yeild and sheer are really close in the 7 series alloys. Possibly a past impact stress riser that has been in the micro fracture process for a while. what was the Diameter of that rod.

wayne
Agreed here...if it was gouged or something at that spot previously, even just flexing back and forth a tiny amount can propogate the cracks through in a hurry. Although I think you probably meant 7075?

I've seen those Al tie rods do some pretty amazing things and spring back, but I was never quite sold on 'em. Then again, I can't keep my 1.5" x .25 DOM ones straight worth crap... :laughing:

I was at that NAXJA event last weekend BTW, I saw your truck and trailer there and stuck around pretty late but I guess you were having too much fun. I had to guide the Clayton buggy around the park the whole day which was a great time. :D
 

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Discussion Starter #7
Dave at Full Circle said it was 7077, per the owner of the rig so it could be correct...or not.

I believe they are made from 1.5" OD material and threaded on both ends. I will see if I can get the actual piece and maybe send them to you, SirMrManGuy. If I can procure it I will PM you. Thanks for the offer.

Crewchief, nice eye! I will let him know.

Vettedude, I wound up getting there late and meeting a group of buddies from BMJA on Otter's trail. Then we ran Tombstone and the new trail at the Quarry. I was able to get through the new trail unassisted so that was fun and then wound up getting back to my trailer around 6PM. At that point I still had to come back to the shop and do some tube work for a customer so it was a pretty long day. Sorry to have missed you, but let me know when you are coming back. BTW, I talked to Clayton today and he said he had a nice time down there, but that the trail guide was a pole smoker with a butch rig, was it you he was speaking of??:flipoff2: :D
 

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I'm not sure if 7077 is an actual aluminum, I didnt recognize it so I looked it up and couldn't find any information, so unless its a new product and not listed I'm willing to bet that its 7075. Not terribly important, most 7000 series fails in a similar fashion.
 

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Isn't 7000 series aluminum hard and brittle? I guess it depends on the heat treat too. Ive seem alot of 7075 T-9 used in aerospace components. Is it non-weldable also?
 

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In both pics you can see that there is a nice rub on the bar that has left some material on the bar itself. I'd say that your friend dropped the front end down or just bumped into the rock to hard and the metal was a little too brittle to take it. Time to go high steer.
 

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Thanks for looking into this Zach. I am a little unclear on exactly what the movement was when the tie rod broke, but I think that I had dropped off a rock placing a lot of weight onto the tie rod via a pointy rock. In the past, I have pushed the tied rod all the way against the diff cover without failure and have even held the entire front end of the jeep up by the tie rod. I am overall satisfied with this tie rod and I think that this was one of those fluke situations. Now when my next one breaks, I'll be pissed. :D

I must be wrong on the series and it is probably 7075.:shaking:

SirMrManGuy, thanks for the offer but I think that I may tig this one back together and carry if for a trail spare.

crewchief, great catch on the mount. I am still running stock mounts but I had not noticed the crack. I will have to take a closer look at that when I get home this evening.
 

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Thanks for looking into this Zach. I am a little unclear on exactly what the movement was when the tie rod broke, but I think that I had dropped off a rock placing a lot of weight onto the tie rod via a pointy rock. In the past, I have pushed the tied rod all the way against the diff cover without failure and have even held the entire front end of the jeep up by the tie rod. I am overall satisfied with this tie rod and I think that this was one of those fluke situations. Now when my next one breaks, I'll be pissed. :D

I must be wrong on the series and it is probably 7075.:shaking:

SirMrManGuy, thanks for the offer but I think that I may tig this one back together and carry if for a trail spare.

crewchief, great catch on the mount. I am still running stock mounts but I had not noticed the crack. I will have to take a closer look at that when I get home this evening.
If it is 7075, don't bother welding it.
 

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I am overall satisfied with this tie rod and I think that this was one of those fluke situations. Now when my next one breaks, I'll be pissed. :D
It's not a fluke that how aluminum works and the next one will fail in the same manner. 7 series doesn't handle cracks very well and every time you run it into a rock you create a small crack in the surface, then every time it flexes after that the crack gets bigger and then you get two tie rods.

2 series handles cracks better but I'm not sure how available it is.
 

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I was under the impression that all 7 series alloys are not weldable? Just because yield and ulitmate are close doesn't mean the material is brittle. Hard yes, brittle no. I was under the impression that toughness was actually quite good on 7075 by aluminum standards.
 

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I was under the impression that all 7 series alloys are not weldable? Just because yield and ulitmate are close doesn't mean the material is brittle. Hard yes, brittle no. I was under the impression that toughness was actually quite good on 7075 by aluminum standards.
They aren't. Well you can weld it but it's not going to hold.

And if the yield and ultimate are close then no the toughness is going to suck, toughness is total area under the curve. Yield is pretty high for aluminum though. And hard does typically mean brittle. Ceramics, glass, high RC steel are all hard and brittle when they fail.
 

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7075-T6 is very susceptible to Stress Corrosion Cracking (SCC, google it). Using a temper such as T73 or T7351 would be a much better choice, but I am willing to bet that no one looks into this when building links, they just want 7075. The continuous loading of the links, combined with a corrosive media (humid air or salt water) could cause failure of 7075 at VERY low loads. The threshold stresses associated with 7075-T6 for causing SCC are in the range of 25 ksi, but that is going by memory, so dont quote me.

There does not seem to be a high number of failures, so perhaps this is a non issue, but it has always been in the back of my mind. Also there is the possibility of galvanic coupling between the link and the steel rod end which could cause failure to watch out for.... again, not real prevalent, but something that should be considered.

Also, weldability of 7075 SUCKS.
 

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Discussion Starter #17
Good info. So, if I found a place or person that could heat or cryo treat links would that help dramatically and which would be better? For instance, if I sent links to Dean, and told him to temper them to T73 or T7351, would that be advisable?
 

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While it's not impossible tempering aluminum isn't super easy and probably easier just to buy it already tempered. Again the 7 sereies does not handle cracks well, the 2 series, like 2024 would be a better choice IMO. And you can get it in round stock.
 

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What about the 7075 that everyone is using for links? The lowers take a beating and i havent seen any breakage. Just curious because I was thinking of going alum. links.
:confused:
 

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Discussion Starter #20
the 2 series, like 2024 would be a better choice IMO. And you can get it in round stock.
So you would prefer more Copper in the alloy than Zinc? I have never heard that before so it is interesting to hear. I Google'd 2024 and it looks like it is used primarily in sheets as I did not see any info on round solids, but Online Metals did have 2" solid listed with a T351 temper.
 
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