
#1
Apr207, 05:27 AM

P: 26

Hi,
Please explain me Allowable stress Calculation? How to calculate allowable stress calculation for different material? 



#2
Apr207, 11:09 AM

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P: 2,878

Hi araan.
Allowable stress is a term used to indicate the maximum amount of stress a material may be subjected to given a predetermined factor of safety. In mechanical engineering, we use allowable stress in piping and pressure vessel analysis. I believe civil engineering uses this concept for other purposes as well, including reinforced concrete structures. Regardless of its use, the calculation of stress can be done using any method suitable, such as conventional hand calculations, using Roark, ASME code calculations, FEA, etc... The stress obtained from those calculations must then be compared to the maximum stress the material is allowed to be exposed to (ie: the allowable stress). For piping codes for example, the stress determined by calculation may not exceed 2/3 of yield strength or about 1/4 of ultimate tensile strength, depending on the code. 



#3
Apr207, 11:40 PM

P: 26

We are in to analysis of a pressure vessel by hand calculation. 



#4
Apr207, 11:49 PM

P: 26

Allowable Stress Calculation
Thank you very much




#5
Apr307, 07:02 AM

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P: 2,878

Hi araan,
Sorry, but the short answer is no, I can't provide you the calculations, and you won't find a link on the web. The specifications are copyrighted, and cost hundreds of $. Which code you're looking for can't even be known from what you're asking. What country you're in determines which code you need to apply. Assuming you're in the US, the next question would be are you going to actually build something or is this just an excersize? If something needs to actually be built, you won't be able to do that since building pressure vessels is governed by state law. If this is just a college excersize, I'd suggest checking out your library for ASME Boiler and Pressure Vessle Code, Section VIII, Division 1 or 2. If you're not in the US, perhaps someone else more familiar with the codes used in your country can help. Sorry I can't help you a bit more, but if you'd be a little more specific about where you are, what this is for, size, pressure, etc… it would be easier to pin down what help you can use. 



#6
Apr607, 06:15 AM

P: 66

Hmm.. I'm not sure he was asking about computer codes, so in case I'm right:
http://en.wikipedia.org/wiki/Von_Mises_stress http://en.wikipedia.org/wiki/Henri_Tresca (http://en.wikipedia.org/wiki/Tcriterion) Basicly, take Von Mises for most cases and devide by the safety factor you want (in general that's 1.2 for aerospace to 20+ for standard machines and structures). 


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