Von Mises Stress: Yield Stress & Elasticity

In summary, if the von mises stress well is below the yield stress, the material may behave elastically for a single or low number of cycles. However, for cyclic or repeatedly-applied loads, the material's fatigue strength must be taken into account. Additionally, the accuracy of the von-mises yield criterion depends on the material, with other yield criteria being more suitable for different materials such as concrete, ceramics, and soil.
  • #1
mattyboson12
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If the von mises stress well is below the yield stress, am I right to assure the material is behaving elastically?
 
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  • #2
Yes, if you express it correctly mathematically.
 
  • #3
mattyboson12 said:
If the von mises stress well is below the yield stress, am I right to assure the material is behaving elastically?

Possibly, but only for a single or low number of cycles. If you're dealing with cyclic or repeatedly-applied loads, you'll need to account for the material's fatigue strength.

https://en.wikipedia.org/wiki/Fatigue_(material)
 
  • #4
Thank you
 
  • #5
It depends on material. Von-mises yield criterion is good for steel and similar ductile and homogenous materials. For concrete, ceramics etc it is not accurate because of the different behaviour under tension and compression, where other yield criteria can be used like the Drucker–Prager one. For soil the Mohr-Coulomb criterion is often used.
 
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1. What is Von Mises stress and how is it calculated?

Von Mises stress is a measure of the amount of stress a material can withstand before it undergoes plastic deformation. It is calculated by taking a combination of the normal and shear stresses on a material and converting them into an equivalent stress value using the Von Mises yield criterion formula.

2. How is yield stress related to Von Mises stress?

Yield stress is the amount of stress at which a material begins to undergo plastic deformation. Von Mises stress is used to determine the yield stress of a material, as it takes into account both normal and shear stresses, which can contribute to plastic deformation.

3. What factors can affect the Von Mises stress of a material?

The Von Mises stress of a material can be affected by various factors such as the material's Young's modulus (a measure of the material's stiffness), the magnitude and direction of the applied stress, and the material's yield strength.

4. Can the Von Mises stress ever exceed the yield stress of a material?

Yes, the Von Mises stress can exceed the yield stress of a material. However, this does not necessarily mean that the material will undergo plastic deformation. The yield stress is simply a threshold at which the material may begin to deform plastically, but it is possible for the material to withstand higher levels of stress without undergoing plastic deformation.

5. Is Von Mises stress a reliable indicator of a material's failure?

No, Von Mises stress is not a reliable indicator of a material's failure. It only takes into account the onset of plastic deformation, but there are other failure modes that can occur in a material, such as fracture or fatigue, which are not captured by Von Mises stress. Therefore, it is important to consider other factors in addition to Von Mises stress when analyzing a material's failure potential.

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