MAE541 -- HOMEWORK 3

 


1.   Distinguish between geometric and material non-linearities. Give an example of each. Using your favorite FEM code solve the following problem:
a) assumiong linear elastic small deformation model.
b) accounting for the material and geometric non-linearities.
c) Comment on the choice of material model and effect of incorporating the geomtric non-linearity.
d) If the code permits, try different non-linear solution schemes Newton-Rhapson etc. Comment on convergence.






2. (Exercise 4 pg 474 in T. J. Hughes )

Consider  M du/dt + K d = 0

For the following variant of the Generalized trapezoidal algorithm
 

dn+1  =  dn + rvn + r2/2 an
 M vn+1 + K dn+1  = 0
M an+1  + K  vn+1 = 0
r is the time step (delta t)
a) What is the amplification factor ?
b) What is the stability condition ?
c) Assuming M is diagonal is the algorithm explicit ?
d) What is the local truncation error and the hence the order of accuracy ?