What stress to use for fatigue analysis

In summary, when choosing stress values for fatigue analysis in a finite element program, it is important to consider the material and loading conditions. Ductile materials with combined loading may use the Von Mises stress, while brittle materials or composites may require different analysis methods.
  • #1
scootypuffsnr
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Hi,

I was wondering which stress values from a finite element program to use for fatigue analysis, (von mises, principal, tresca). I was leaning towards principal stresses but then would my stress range be σ11 from load case 1 (LC1) to σ11 of LC2, or would i need to do σ11-σ33 first and then would my stress range be (σ11-σ33) LC1 to (σ11-σ33) for LC2. Sorry I am a bit confused. Thank you
 
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  • #2
It will largely depend on your material for analysis and loading conditions. Ductile materials with combined loading conditions (e.g. shear + tension) will tend to use Von Mises compared to the material's S-N curve. Brittle materials or composites will have very different analysis methods though...
 

1. What is stress?

Stress is a measure of the internal forces acting within a material, typically caused by an external load or force. It is a physical quantity that can be calculated using concepts from mechanics and physics.

2. Why is stress important in fatigue analysis?

In fatigue analysis, stress is crucial because it determines the amount of strain and deformation a material undergoes under repeated loading. If the stress exceeds the material's endurance limit, it can lead to failure and structural damage.

3. How do I determine the appropriate stress to use for fatigue analysis?

The appropriate stress to use for fatigue analysis depends on the type of loading, the material properties, and the design specifications. Generally, engineers use a combination of theoretical calculations, experimental data, and industry standards to determine the appropriate stress.

4. Can I use any stress value for fatigue analysis?

No, not all stress values are suitable for fatigue analysis. It is essential to use a stress value that accurately reflects the type of loading and the material's behavior under repeated stress. Using incorrect stress values can lead to inaccurate results and potential structural failures.

5. How does stress affect the fatigue life of a material?

The stress level significantly influences the fatigue life of a material. Higher stress levels can lead to a shorter fatigue life, while lower stress levels can increase the material's endurance. It is crucial to balance the stress level to ensure the material can withstand the intended number of loading cycles without failure.

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