ASME B31.3 Tensile Strength 1

[Engineer_M]

Hi,

Does anyone know if there is a safety factor involved in the tensile strengths in ASME B31.3?

Thank you!

 

[EdStainless]

Aren't the strengths listed the specification minimums?
So it would be possible for you to get material that actually had that strength.
The SF is built into the allowed design stresses.

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P.E. Metallurgy

 

[LittleInch]

B 31.3 is a large code. Please be ab it more specific about the section or table or an example.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Engineer_M]

Thank you for your responses!

I was referring to Basic Allowable Stresses in Table A-1. I know the basic allowable stresses are lesser of the 1/3* tensile strength or 2/3 * yield strength. I was just wondering if the listed tensile strength itself had any safety factor involved?

 

[david339933]

No. Tensile strength is the minimum required by the material specification.

 

[XL83NL]

Then I guess what it all boils down to, and what the OP’s next question could be; how do the specs come up with a minimum yield? Is it based on historical data? Probably something g that’s been asked here before, not sure anymore what the answer was though...

 

[DriveMeNuts]

For many materials, the Minimum UTS and Yield are what the mill could comfortably guarantee with milling technology available when the material was developed, often in the 1980's or earlier.

Milling techniques and QA have come along way over the years, reducing the variation in material properties at the mill, meaning that the UTS or yield on old material grades now have a lot of strength to spare. For some people this spare strength allows them to sleep better. For others, it is a waste of resources. Some older material specs could have additional grades added such as perhaps SA-516 Grade 80.

For ASME materials, the yield and UTS often reflect the guaranteed properties of a 200mm thick plate, which is then applied to all thicknesses. In reality, 10mm plate has strength properties which are 30-40% higher than 200mm thick plate. I can only assume politics is involved to produce such waste.

The EU material codes specify properties for different thicknesses. Does anyone know why ASTM doesn't do the same?