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Discussion Starter · #1 ·
I was graciously supplied with a few connecting rods from a Ducati 750SS from a fellow member. I am doing a finite element analysis on the connecting rods for an engineering course I'm enrolled in, but I'm not exactly sure what material they are made of. Anyone have an idea? I'm looking for something a bit more detailed than "steel", as I'd like fairly accurate material properties (i.e. Young's Modulus, failure criteria, etc.). I've searched to no avail.

Thanks for your help!

-Danimal
 

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To do the analysis you don't need to know anything other than the fact that they are steel. I am also taking an FEA course and all you need to perform the basic structural analysis is Youngs modulus and poissons ratio. If you didn't already know all steels have the same Young's modulus (30x10^6 psi) and the poissons ratio is 0.3.

The problem with connecting rods is that they're usually case hardened so the material yield strength isn't uniform throughout.
 

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I have never seen a case hardened rod in my life.
They may be shot peened to improve fatigue crack resistance and heat treated to improve yield strength.
Cryotreating is also done to relieve residual stress.
A mod of 29E6 and poisson's of .3 is about right for all iron based materials tho....
 

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Discussion Starter · #4 ·
Ehh, Youngs Modulus for steel can vary up to 20% depending on many different factors (heat treating, shot peening, forging, etc.). I also am using the failure criteara which varies greatly depending on material.

If you aren't yet familiar, check out www.matweb.com . It is my freakin bible when it comes to material properties. They have a few thousand types of steel, its pretty impressive.

While my analysis is fairly basic, I still need to include accurate material properties in my report.

Thanks again all!

-Danimal
 

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Discussion Starter · #5 ·
dakinebusa said:
A mod of 29E6 and poisson's of .3 is about right for all iron based materials tho....
Yeah, from everything I've seen, 29e6 psi seems common among the treated steels.
 

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dakinebusa said:
I have never seen a case hardened rod in my life.
They may be shot peened to improve fatigue crack resistance and heat treated to improve yield strength.
Cryotreating is also done to relieve residual stress.
A mod of 29E6 and poisson's of .3 is about right for all iron based materials tho....

Coupla years ago I was up at BCM on a Sunday (to meet up for a group ride) and Bruce was in the shop taking apart a Corse engine he'd bought (both to put into a customer bike and to study). He pointed out to me that, counter to conventional shot peening practice, the con rods were polished!
 

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Isn't that normal on a race motor?

My pops always had the crank and rods polished on his sprint car motors

said it moved through the oil bath easier and you could identify potential failures quicker on visual inspection

as to the above discussion, does it somehow make the parts stronger?
 

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Polishing removes surface imperfections that could grow into cracks under stress.
Too labor intensive to be standard practice and not really necessary using good steel.
Carrillo rods come with a satin finish that looks like bead blast.

Here is a great article from Carrillo's web site on eliminating rod failure.
http://www.carrilloind.com/pdfs/10777_eprint.pdf
 

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Discussion Starter · #10 ·
Norm said:
I knew we had smart people on this list somewhere. [clap]
Honestly, you were the one I was hoping would chime in on this thread. You are the smart people on this list, Norm!

Now...tell me what these friggin rods are made of! [laugh]

-Danimal
 

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Thanks,

That's a very good article. I have never experienced a rod failure using torque only, but I think I'll do as suggested, and use both torque and stretch in the future.

LA
 

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Danimal said:
Honestly, you were the one I was hoping would chime in on this thread. You are the smart people on this list, Norm!

Now...tell me what these friggin rods are made of! [laugh]

-Danimal
I'm sure it's a euro spec steel.
Maybe EN19?????
I don't know the type but you wouldn't be far wrong using the numbers from AISI 4340 VAR.
 

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Mother said:
Isn't that normal on a race motor?

My pops always had the crank and rods polished on his sprint car motors

said it moved through the oil bath easier and you could identify potential failures quicker on visual inspection

as to the above discussion, does it somehow make the parts stronger?
Actually, it's my understanding that polishing was old school and that more recently, bead blasting had been preferred as it stress relieves the surface layer where polishing doesn't. That's why Bruce thought it remarkable (in the literal sense) to see the rods polished.
 

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Carillo rods are shot peened (I've been to their facility and seen the equipment).

Shot peening is done with steel shot.
The size and velocity of the shot is controlled, depending on the parts and desired level of peening desired.
The primary benefit is that it leaves a residual compressive stress in the surface, which strongly inhibits crack formation.

Bead blasting is done with glass beads, which really only cleans the surface, there's no alteration of the material properties.

Usual procedure if you have rough 'as-forged' rods is to grind/smooth out the grooves/nasty areas, then get 'em shot peened.

Polishing alone will indeed remove the stress risers (grooves and nasty finish), which does help the durability.
But if you're polishing a shot peened rod, you're removing the surface layer that's got the residual compressive stress, and likely end up worse off from a durability standpoint.
 

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Oops. I was misusing the term "bead blasting." Shot peening is indeed what I meant.

Unless they use "media blasting;" walnut shells should go a long way to ensuring longevity [laugh]
 

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CRASH! said:
Oops. I was misusing the term "bead blasting." Shot peening is indeed what I meant.

Unless they use "media blasting;" walnut shells should go a long way to ensuring longevity [laugh]
As long as you don't accidental shot peen your fuel tank all should be cool ;D
 
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