Best Bolt Material
Best Bolt Material
(OP)
What is the absolute best readily obtainable bolt material for making special bolts of 20mm diameter, from both an ultimate strength and fatigue life standpoint ?
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RE: Best Bolt Material
http://www.arp-bolts.com/pages/tech/matspec.html
http://www.cartech.com
http://www.spstech.com/aero/prod_lit/superalloy_brochure.pdf
http://www.allvac.com/allvac/pages/PDF/tech/VascoMaxC.pdf
RE: Best Bolt Material
[/b]TVP's[/b] recommendations are very good sources but several of the materials mentioned have some limiting factors that need to be considered.
RE: Best Bolt Material
I have been told that maraging steel offers little advantage over medium carbon steel for this application because of the poor notch sensitivity. Any comments ?
Unclesyd: I will get back to you on the detailed operating conditions.
RE: Best Bolt Material
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Best Bolt Material
The operating conditions are:
Low corrosion environment
Studs are 325mm long x 20mm dia and see 250000 lb/in^2 with a very small superimposed additional cyclic stress.
Other info:
Cannot afford to buy more than 150 feet per order.
We would like to see a material with relatively high ductility to improve the fatigue life if possible.
RE: Best Bolt Material
nick
RE: Best Bolt Material
I hope this is a total load for multiple studs as I don't think we can get there on one 20 mm fastener.
RE: Best Bolt Material
RE: Best Bolt Material
unclesyd: Perhaps I should mention that this is a rather unusual situation, where the bolts (actually studs) are being called upon to act as highly preloaded axial tension springs with very short travels. To provide maximum insurance against overstressing, it appears that it will be necessary to employ the very best material available.
RE: Best Bolt Material
Cleared up the 250,000 psi and added a bear. The only thing going for you is the large L/D.
As posted by TVP there are several materials available at the company websites as posted.
From your latest posting I would contact SPS with the problem as this rather a unique application where the stud will act as working spring. As you know this imposes several additional parameters on the fastener material and will probably require a specially designed fastener, somewhat like a tensile test bar with threaded ends. At these strength levels thread fatigue, beam bending, and strip out of the nuts worries me.
I think that you will have a nut that allows internal flexing of it's threads but again this a tough design problem and SPS should be familiar with a nut of this type. The are a couple of different nuts that may be required to overcome the inherent flexing of the first threads. Anything you do will have a finite life.
We have a similar situation where we have a fastener that has to allow slight axial movement of one of the clamped components. We accomplished this with Belville Washers and Inconel 718 Studs. The studs are nowhere near the strength levels you talking about.
Is it possible to provide the following information.
What is the actual load on the stud?
How much "spring" is required?
Is the stud set in or free?
Will the clamped material be able to carry the load imposed by the stud without a hardened washer.
RE: Best Bolt Material
Your last comments regarding fatigue represent only the most basic concept of fatigue (infinite life of steels assuming high cycle fatigue). Ductility is of huge importance to low cycle fatigue, as the fatigue life is determined by the amount of strain a component can provide during a cycle. Actually, the best way to think about fatigue is with fracture mechanics: a tough material (with high ductility) will have high resistance to crack propagation, and therefore, will have a high fatigue life. You may notice that materials like AerMet and MP35N have enormous strength AND fracture toughness AND fatigue strength.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Best Bolt Material