Are yield and tensile material properties equivalent in ductile materials?

[ezzieyguywuf]

In example problem 52.5 on page 52-7 of the 13th edition of the MERM, material properties are given for aluminum. In the solution, these same material properties are listed as the 'tensile', ostensibly for the purposes of constructing a Goodman Line.

My question: should it be assumed that the material properties given are specifically for the tensile strength? Or, since its aluminum, is it safe to assume that the material properties are the same in both directions?

Reading through chapter 48, there's an interesting line in section 14 on page 48-8: "...the compressive strengths of ductile materials, such as steel, are the same as their tensile yield strengths."

I took this sentence to mean that . Somehow that doesn't seem right though. Any help? Is this a typo in the MERM (I've found others...)?

 

[P-E]

No they are not the same.   Yield strength is the end of elasticity before deformation for elastic materials.  Tensile is where it fails.  

 

[ezzieyguywuf]

I asked my question incorrectly. I meant to ask about tensile and compressive. Ie yield strength for a tensile vs compressive load in a ductile material. 

 

[J_MEC]

I do not think you can say that in general ductile materials have the same compression and tensile yield strengths. Some magnesium alloys are generally considered ductile materials but do not have the same yield strength in tension and compression.

I would say that in the case of this problem that the aluminum can be considered a ductile material with the same yield strength in tension and compression.

Hopefully that answers your question.

 

[ezzieyguywuf]

I suppose on the exam itself, if I am provided with a Yield and/or Ultimate strength of a material, but the solution itself requires specifically the Tensile or Compressive Strengths, I will assume that the Strength given is in the direction (i.e. Tension or Compression) that I need. Does that seem reasonable?