Dear Yevs I got it. Thanks a lot.
Best Tetsuo 2020年12月13日(日) 4:00 Yves Renard <[email protected]>: > > Dear Tetsuo, > > The bilaplacian is a fourth order derivative term and the weak > formulation contains second order derivative terms of the unknown and > the test function. So this is normal that you obtain zero for a P1 > Lagrange finite element. In fact, you have to use a C1-conformal finite > element to use the bilapalcian brick. For instance Argyris or HCT elements. > > Best regards, > > Yves > > > > On 12/12/2020 06:52, Tetsuo Koyama wrote: > > Hello, GetFEM project. > > > > I have a problem using the add_bilaplacian_brick method of the Model > > object. My wish is to get the following stiffness matrix in the > > attached script file, but I got an empty stiffness matrix. > > > > Trace 2 in getfem_fourth_order.cc, line 88: Stiffness matrix assembly > > of a bilaplacian term > > Computed matrix is... > > matrix(2, 2) > > ( ) > > ( ) > > > > Expected matrix is... > > matrix(2, 2) > > ( (r0, 100) (r1, -100) ) > > ( (r0, -100) (r1, 100) ) > > > > I'm sorry, but could you please review my script to see if there is > > any problem? > > I used the developing version in the git repository. > > > -- > > Yves Renard ([email protected]) tel : (33) 04.72.43.87.08 > INSA-Lyon > 20, rue Albert Einstein > 69621 Villeurbanne Cedex, FRANCE > http://math.univ-lyon1.fr/~renard > > --------- > >
