Specific Yield Strength Question for A572 material

In summary: The A871 specification, which is relatively new, does use the 0.2% offset method and this can be seen in the stress-strain curve of a test sample. Full scale testing results have also shown that the test structure does not return to zero after taking all loading off, further supporting the use of the 0.2% offset method in this specification. It is important for those in the industry to be aware of these differences in specifications and the potential effects on structure behavior.
  • #1
daichinger
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My industry (tubular steel poles) standardly uses A572, Gr65 and A871, Gr65 for shaft design with the designs taken to the minimum ASTM defined Yield and using loading factors in the design. The A572 specification has for years listed all grades as "Yield Point". The A871 specificaion (which is relatively new) lists "Yield Strength" with a note indicating the use of the 0.2% offset method. I recently have recently seen the stress-strain curve of a test sample for A871 and it does reflect the graphical representation of the 0.2% offset versus the "yield point" style. This also reflects full scale testing results I have recently seen where the test structure DID NOT return to zero after taking all loading off. My question (finally): is the A572, Gr 65 REALLY "Yield Point" and not 0.2% offset? My industry has the expectation that structures will behave elastically through the Yield Point specified. I am suspicious that this is true. Can anyone clarify this for me? Thank you.
 
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  • #2
Yes, the A572, Gr 65 is indeed a yield point specification and not a 0.2% offset specification. This can be verified by consulting the ASTM standard for A572 which states that the yield strength requirement is based on a 0.2% offset method. It is important to note that even though this is a yield point specification, structures still may not behave elastically through the yield point due to strain hardening effects.
 

1. What is specific yield strength?

Specific yield strength is a measure of the amount of stress a material can withstand before it begins to deform permanently. It is calculated by dividing the yield strength of the material by its density.

2. How is specific yield strength different from yield strength?

Yield strength is a measure of the amount of stress a material can withstand before it begins to deform permanently, while specific yield strength takes into account the density of the material to provide a more accurate measure of its strength.

3. What is the specific yield strength of A572 material?

The specific yield strength of A572 material varies depending on the grade, with A572 grade 50 having a specific yield strength of 345 MPa and A572 grade 65 having a specific yield strength of 450 MPa.

4. How does specific yield strength affect the design of structures?

Specific yield strength is an important factor in the design of structures as it determines the maximum amount of stress a material can withstand before it begins to deform permanently. This information is crucial in determining the appropriate materials to use and the dimensions needed for a structure to withstand expected loads.

5. Can specific yield strength be improved?

Yes, specific yield strength can be improved through various methods such as heat treatment, alloying, and cold working. These methods can increase the yield strength of a material without significantly affecting its density, resulting in a higher specific yield strength.

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