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FEA

This topic is beyond piping design, and the reason that I bring this topic is to shown how values from theoretical calculation can be verified in real life. Algor FEA software is environment for stress analysis. Verifying principal stress is not possible, since they are only theoretical values, but displacements can be measured and compared with calculated values. Back in 90’s customer wanted FEA analysis of the ladle that holds molten steel. Soon after FEA is done, customer wanted to measure the deflections making sure that the FEA results are correct. Please see the figure below. Note that the maximum Von Mises stress is 8273.8 psi which is far below allowable stress.
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Since it was not possible to load ladle with molten steel, we decided to take a sand as a load and underneath of ladle we placed the measurement device. Measured displacement was in agreement with the FEA analysis and accuracy was in forth decimal places. Please see the figure below.
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Below are a few examples of FEA analysis. Note that Von Mises stress is relatively low and reason for that is a fatigue. In many cases, customer wanted to have Von Mises bellow 12000 psi due to the fatigue. In my opinion that might be too conservative, since FEA stress analysis will always shows greater stresses than manual calculation. Note that having Von Mises stress larger than yield stress does not mean always failure. If you model elements as a brick, local stress at some point might be greater than the yield stress, but element will not experience failure due to fact that yielding occur locally; not in the whole section. On the other hand, in plate element model; Von Mises stress must be limited to yield stress, otherwise failure will occur. Figures bellow shows different approaches to the modeling.
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Lifting beam 20 tons capacity modeled as plate elements

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Hook block 180 ton capacity modeled as brick elements.

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Tundish 25 ton capacity modeled as combination of plate and brick elements