Initial,post limit,secant stiffness

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In summary, the conversation discusses the differences between initial stiffness, post limit stiffness, and secant stiffness. Initial stiffness is the tangential stiffness at the beginning, secant stiffness is the slope of the secant line passing through 0,0 and the yield point, and post limit stiffness is the stiffness of a component after yielding. The significance of the slope of the stress strain curve is also mentioned, with a book mentioning that the post-limit stiffness is reduced in the case of a higher bolt grade. The person asking the question is still confused about post stiffness and is seeking clarification on it.
  • #1
Sadeq
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Hello,

My question is simple, but it does confuse me.

I need to know the exact difference between
Initial stiffness,post limit stiffness, and secant stiffness in details please

Please clarify this on graph if possible

Thank you
 
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  • #2
What have you looked up about these topics so far?
 
  • #3
I know that initial stiffness is the tangential stiffness at the beginning and the secant stiffness represent, the secant line passing through 0,0 and the final point( yield point).But still confuse about the post limit stiffness, that way i asked for drawing to clarify them all at the same graph

Thank you
 
  • #4
What limit is it that you think it refers to?
 
  • #5
I don't know exactly that's why i am asking if anyone know about post stiffness concept.
Thank you
 
  • #6
http://postimg.org/image/3n5smqb35/

in this picture a book mention that the post-limit stiffness of the component (upon yielding) is notably reduced in the case of the higher bolt grade(red line).

And i don't understand post stiffness.

Help me please
 
  • #7
What is the significance of the slope of the stress strain curve before and after yield?
 

FAQ: Initial,post limit,secant stiffness

What is initial stiffness and why is it important?

Initial stiffness refers to the stiffness of a material or structure when it is first loaded. It is important because it helps determine the overall strength and stability of the material or structure, as well as its ability to resist deformation.

What is post limit and how does it relate to initial stiffness?

Post limit refers to the point at which a material or structure can no longer resist deformation and begins to fail. It is related to initial stiffness because the initial stiffness helps determine how much load a material or structure can withstand before reaching its post limit.

What is secant stiffness and how is it different from initial stiffness?

Secant stiffness is a measure of the slope of the stress-strain curve at a specific point. It is different from initial stiffness because it takes into account the non-linear behavior of materials under load, whereas initial stiffness only considers the linear portion of the stress-strain curve.

How is initial stiffness calculated?

Initial stiffness is typically calculated by dividing the change in load by the change in displacement within the linear portion of the stress-strain curve. This gives the slope of the curve, which represents the initial stiffness.

Why is it important to consider initial stiffness, post limit, and secant stiffness in material testing?

These factors are important to consider in material testing because they provide valuable information about a material's behavior under load. Initial stiffness can help determine the strength and stability of a material, post limit can indicate when a material may fail, and secant stiffness can provide insight into the non-linear behavior of a material. Understanding these properties can help scientists and engineers make informed decisions about materials for various applications.

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