Obtaining material stress-strain curve 6

[yaston4]

Hello all,

I would like to get some input from experienced engineers and materials scientists. I am after the stress-strain curve to use the data for my FE analysis material model. The material is a particular ASTM material. I have not been able to find the material data available and so it looks like I will need obtain the data myself through an experiment, but have no experience obtaining this kind of data.

I would really appreciate some input as the equipment and tests pieces required to obtain such data. Indeed if there are any shortcuts or tricks of the trade I would really like to hear them.

Thanks-you.

 

[rb1957]

what material ? Steel ? Aluminuium, Unobtainium ??
maybe we can help.

if you need to develop it for yourself, you need a tension loading machine, standard tension specimens, and a notebook

 

[TonyDeRamo]

I believe the ASTM standards have all the properties you may be interested in. If you know the ASTM number, you can find it on their website. However you will probably have to purchase the standard. I would think it is alot cheaper than performing your own tests.

"Research is what I'm doing when I don't know what I'm doing."

 

[rb1957]

pretty much anything is cheaper than doing your own tests !

 

[JStephen]

How you obtain this kind of experimental data is call up a lab and tell 'em what you need. Similar testing is commonly done for weld procedures, etc. It may be hard to come up with a sample of the material without buying 10 tons of it, though.

 

[yaston4]

Thanks everyone, I really appreciate so much input from the engineering community. The material is ASTM75 Cobalt Chrome. Here is the link to the ASTM standard

http://www.astm.org/Standards/F75.htm

I have contacted them but apparently the standard does not contain a stress-strain curve (there only so much you can fit into 4 pages). If some has access to the standard perhaps they wouldn't mind kindly confirming if the standard does have a stress-strain curve or not.

Because it is quite a specialist material in a specific form, most materials companies and materials testing companies (at least the ones I have contact with) can not help with this.

I look forward to any further input from the community, thanks.

 

[TVP]

yaston4,

If you have an actual sample of the material, then you should just have a certified lab test it for you. Machining a specimen and having it tensile tested costs ~ $100 in the USA. I imagine that it would be similar cost in the UK.

 

[jpankask]

I can't see the current version of the standard (without paying), but pulled up a couple oder versions(2007 and 2001). There is no stress-strain curve in the standard.

 

[dhengr]

That type of material is not made by just any steel mill is it? It’s usually a proprietary material. I would expect that supplier to have this type of data on their own material, and that’s where I would go first. The warehouse you bought it from should know who made it and be able to supply a mill cert. on it, and they should help you in gathering the other info., or at least direct you to the source. I don’t know exactly what you are trying to do, you’re keeping that a secret. But, I would assume you want the shape and plot of the curve; and you really want to know whether the material has a yield point or not, has a plastic plateau, and how they define their yield strength, and at what offset. These are often hidden in the scale of the whole curve, if you don’t bring that subject up.

 

[yaston4]

TVP, thanks for the suggestions and reassurance. Finding a materials testing company seems easier than finding someone who can supply the material.

jpankask, thanks for confirming that the previous versions do not have a stress strain curve.

dhergr, thanks for your input, your right it is not a run of the mill steel. The company who use the material for there products say they do not have any stress-strain curve of the material. Being that it is proprietary like you say, gives me less of a chance of receiving it from them even if they did have it. There's no secrecy here, as I mentioned I need the stress-strain data for my material model in FEA to run stress and contact analysis, I am not sure what more I can say? What else would you like the know?

Thanks again so far everyone, any further inputs would be much appreciated.

 

[jpankask]

Perhaps you already know but for that material, the minimum ultimate tensile strength is 95,000 psi and the minimum yield strength is 65,000 psi. If you are doing this project for a company that has the material or has access to the material, they should be able to get whatever information you require for your analysis. They may not have it now, but should be able to get it, or get you in touch with someone who can get the information.