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Re: Calculating Young's Modulus
Re: Calculating Young's Modulus -- mpw-ash	Post Reply	Top of thread	Forum

Posted by: rconner ® 09/19/2006, 13:47:18 Author Profile eMail author Edit

No (I believe Young's Modulus is generally considered to be the slope of the stress strain curve e.g. in a tensile test of a sample of the material -- and you have not provided this information per se in your inquiry.) However, I suspect you could well be dealing e.g. with a rather high-strength steel, with said modulus maybe some less than the 29-30 million psi normally talked about in ordinary structural carbon steels. It would thus be best for you to better identify your material, for some more knowledgeable responses.

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Re: Calculating Young's Modulus
Re: Calculating Young's Modulus -- mpw-ash	Post Reply	Top of thread	Forum

Posted by: Guttdogg ® 09/19/2006, 09:27:13 Author Profile eMail author Edit

Y=Stress/Strain or Y= (delta F/A)/(delta L/L) ~Sorry, I couldn't find the alt code for the delta symbol

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Re: Re: Calculating Young's Modulus
Re: Re: Calculating Young's Modulus -- Guttdogg	Post Reply	Top of thread	Forum

Posted by: mpw-ash ® 09/19/2006, 17:54:20 Author Profile eMail author Edit

Thanks for your speedy response Guys. The material type is titanium grade 5 (6Al-4V) & we have the theoretical Young's modulus from the manufacturer, but when we put this Young's modulus into our FEA software (Ansys Designspace) it gives us a result that is not even close to what we are getting in real life when we actually machine the parts. If it helps, the titanium parts are 16, Ø29.2mm probes that get screwed down to a block of 7075-T7 aluminium. Together they are a composite Ultrasonic horn for welding plastic. It operates at 20,000 Hz so there is considerable amount of stresses involved & if it is not designed just right the aluminium will crack which is why it needs to be of an aircraft grade. I know the formula for calculating Young's modulus is : Y=Stress/Strain but the material certificate only gives the values stated above. I thought there is a way of calculating Young's modulus from this data by finding the stress & strain from these values. Any help is greatly appreciated. Thanks again.

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Re: Re: Re: Calculating Young's Modulus
Re: Re: Re: Calculating Young's Modulus -- mpw-ash	Post Reply	Top of thread	Forum

Posted by: rconner ® 09/20/2006, 09:17:12 Author Profile eMail author Edit

If you believe your problems are due to an inaccuracy in the modulus value you've been provided by the manufacturer, you might ask them for an actual stress strain curve to determine the slope of same yourself (or ask them, you, or a third-party laboratory to machine a tensile specimen from the material, strap an "extensometer" on same, and using this and a testing machine plot a similar curve -- I don't think this is an elaborate test, but obviously requires the equipment to perform it). I guess it might however be adviseable to consider temperature (and maybe even any specific alloying) in this process, as per the site at engineeringtoolbox, Young's modulus of unalloyed titanium apparently varies in the range of ~11-16 million psi depending on extremes of temperature. Modified by Administrator at Wed, Sep 20, 2006, 10:24:37

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Calculating Young's Modulus
Re: Re: Re: Re: Calculating Young's Modulus -- rconner	Post Reply	Top of thread	Forum

Posted by: mpw-ash ® 09/20/2006, 17:55:35 Author Profile eMail author Edit

Thanks everyone. So it seems I don't have enough data to determine what the Young's Modulus is of my titanium. Oh well, guess I'll just have to live with it. Thanks again!

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