How to calculate if a part will fail at a specific spot

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In summary, the conversation discusses evaluating failure spots in a rigid body. The suggestion is to use Finite Element Analysis to calculate von Mises stress at specific locations and compare it with yield stress of the material to determine if failure may occur. Additionally, it is mentioned that hand calculations may not account for stress concentrations around sharp corners and a picture of the structure would be helpful for further analysis.
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Hey everybody so I am a student and I am learning about failure analysis. So let's say I have a rigid body that is being kept in this position...there is a moment at A generated by a motor to keep the body in this position, working against the weight of the body itself and small wind force. There are bearing reactions at A. I know about making shear and bending diagrams but when it is angled like this how do I calculate if it will fail at these spots?
moment.png
 
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Assumption that the part is rigid can't be made in this case when you want to evaluate failure spots. You could solve this as an inclined beam in bending but it won't account for stress concentrations and these will definitely occur in the spots marked with red dots. You would have to perform Finite Element Analysis to calculate von Mises stress at these locations and then compare it with yield stress of the material to find out if failure may occur due to applied load.
 
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FEAnalyst said:
Assumption that the part is rigid can't be made in this case when you want to evaluate failure spots. You could solve this as an inclined beam in bending but it won't account for stress concentrations and these will definitely occur in the spots marked with red dots. You would have to perform Finite Element Analysis to calculate von Mises stress at these locations and then compare it with yield stress of the material to find out if failure may occur due to applied load.
I think I understand. So if it was instead in this position would it then be possible to calculate if it would fail at those points and how?

moment2.png
 
  • #4
The fact that it's at an angle is not a problem. It can be solved as a beam either way. What I meant is that these hand calculations (for both inclined and horizontal beams) can be used to determine overall stress level due to bending in specific cross-section but they can't account for effects occurring around sharp corners. In these locations there are so called stress concetrations (notch effect). Pretty much only FEA with high quality mesh can predict stress state in such cases. I could perform such analysis for you but I need more details about this structure - its size, material, wind force value and so on. And if you have a picture showing how it looks like in real life then it would be very helpful too.
 
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1. How do I calculate the stress at a specific spot on a part?

The stress at a specific spot on a part can be calculated by dividing the force applied to the part by the cross-sectional area at that spot. This will give you the stress in units of force per area, such as pounds per square inch or newtons per square meter.

2. What factors should I consider when determining if a part will fail at a specific spot?

Several factors should be considered when determining if a part will fail at a specific spot, including the material properties of the part, the applied load, the geometry of the part, and any potential defects or imperfections in the part.

3. How can I determine the strength of a material at a specific spot?

The strength of a material at a specific spot can be determined by conducting tensile or compression tests on samples of the material. These tests will provide data on the material's yield strength, ultimate strength, and other important properties.

4. Is there a formula for calculating the probability of failure at a specific spot?

There are several formulas and methods for calculating the probability of failure at a specific spot, including the Weibull distribution, the Monte Carlo simulation method, and the First-Order Reliability Method (FORM). The appropriate method will depend on the specific application and data available.

5. Can computer simulations be used to predict if a part will fail at a specific spot?

Yes, computer simulations can be used to predict if a part will fail at a specific spot. Finite Element Analysis (FEA) is a common method used to simulate the behavior of a part under different loading conditions and can provide valuable insights into potential failure points and modes.

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