problema FEM

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Tocmai am dat de un exemplu tare interesant si nu puteam sa nu-l postez.

Deci, mai jos este un exercitiu dintr-o carte de Metodata elementelor finite:

 

EXERCISE 7.8 You (a finite element guru) pass away and come back to the next life as an intelligent but hungry bird. Looking around, you notice a succulent big worm taking a peek at the weather. You grab one end and pull for dinner; see Figure E7.6.

After a long struggle, however, the worm wins. While hungrily looking for a smaller one your thoughts wonder to FEM and how the worm extraction process might be modeled so you can pull it out more efficiently. Then you wake up to face this homework question. Try your hand at the following “worm modeling” points.

(a) The worm is simply modeled as a string of one-dimensional (bar) elements. The “worm axial force” is of course constant from the beak B to ground level G, then decreases rapidly because of soil friction (which varies roughly as plotted in the figure above) and drops to nearly zero over DE. Sketch how a good “worm-element mesh” should look like to capture the axial force well.

(b) On the above model, how would you represent boundary conditions, applied forces and friction forces?

(c) Next you want a more refined anaysis of the worm that distinguishes skin and insides. What type of finite element model would be appropriate?

(d) (Advanced) Finally, point out what need to be added to the model of (c) to include the soil as an elastic medium.

 

Briefly explain your decisions. Dont write equations

 

 

 

Sursa.

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