Need Material with HIGH Shear 2

[CajunNGnear]

I'm looking for an alloy with an extremely high shear. I have an application where the piece is in pure shear. I tried 4340 Q&T that had a Tensile yield of 240ksi and a shear of about 180ksi but it couldn't handle the load. I'm looking at 300ksi (tensile) MP35N but I cannot find any data on the shear strength.

Does anyone have a suggestion for a material with 200+ ksi shear strength?

 

[TVP]

I don't think you are going to find anything with guaranteed/published shear strength > 180 ksi. The maximum guaranteed shear strength that SPS shows for any of their ultra-high strength fasteners 160 ksi for Aermet 100 (hardened to UTS of 280 ksi). If I were you, I would try MP35N at UTS 300 ksi and see what shear strength you get. That will likely be the best that you can obtain. Keep in mind that any low-friction coatings will reduce considerably the shear strength, so this is an advantage for inherently corrosion resistant materials like MP35N.

 

[EdStainless]

What is the strength of the parts holding the fastener? If they aren't close to these strengths then you will get tearing of the holes.
If this pin is loaded only in shear then you have some options.
Look at Elgiloy, in the cold worked+aged condition. It will be stronger than MP35N.
Many age hardening alloy can be hardened directly from the cold worked condition to reach higher strengths. This heat treat condition is usually not recommended since the ductility is very low, but high strengths, even in alloys like 17-7PH can be achieved.

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[CajunNGnear]

The materials holding the parts (ring) are much thicker. This parts has a groove that is less than 1/2" thick for the lock ring to fit in. The material I used was a 4340 with an HRC of 37-39.

 

[unclesyd]

I would look at some of the tool steels like H11 and H13. We use both materials in very high shear locations. Sorry I don't have any numbers but both are quite high and subject to some impact loading. Another material we used was D2.
A lot of the required shear strength resolves around how is the load applied, speed.
Other points to look at is both contact faces, edge of and fit of pins in hole. In a project that I worked on many years ago involving a small hardened shear pin, .078" dia. showed that 0.001" gap between the faces had a large affect on the shearing strength. In the same tests I tried different radius on the holes also had a large effect on the shearing point.

 

[BrianE22]

I had wondered how the edge of the hole in the shaft (chamfered, radius or sharp) affected the shear strength of the joint. Sounds like sharp edges on the holes with a high local stength on those parts is the optimum situation for the joint?

 

[unclesyd]

Adding a little to my previous post.
Distance between shear plates and the shape of the hole in reality brought in a tensile component to the shearing action.
Another point is that the pin holder has to be as hard or harder than the pin in shear. In other words you can't insert a very hard pin on !020 CS and expect to get consistent results. This can be mitigate somewhat by using a larger dia. pin.

 

[EdStainless]

and don't forget toughness. You need enough ductility to prevent a brittle fracture mode.
Your ring is 4340 at Rc38? If so then your pins should not be harder than that. If that is not enough strength then you need larger pins and/or more pins.

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