Hi @Preben Alsholm 

Thanks a lot again

1) I realized it's look more compact, but maybe you have some other reason.

2) Stupid question. My fault. It's a constants yes... sorry.

3) The same that first one. It's about compactation and size. thanks

4) Thanks to Carl.

5) Ok... I understand. This constant could be whatever. Well... we could express more compact using the phi (phase angle), but it's not really necesary, and it doesn't give you a value of A, it's still a constant. So it's ok.

Thanks very much Preben.

ger89

P.D.- I can considerer my question answered. Thanks a lot to everyone!

Hi @Carl Love 

Thanks very much for the answer! 

Hi @Preben Alsholm 

It's means Inertia * Elastic Modulus... so, I dont mind IE o EI, but I will change E*I by EI.

Thanks very much!

Hi @Preben Alsholm 

I'm impressed with your code. Thanks a lot, I see more clear the problem and what to do. But I have just a few little questions:

1- Why you change _C[1] by (c/L)^4 ?... I mean, why you introduce L? How did you know?

2- In the line of the boundary conditions definitions, you dont forget to write E*I in the last two derivattes ??
eqs:=[seq(eval(diff(rhs(sol2),[x$k]),x=0)=0,k=0..1),seq(eval(diff(rhs(sol2),[x$k]),x=L)=0,k=2..3)];

3- Another change: ode1a:=subs(IE=K*m,%); ... how did you know we have to make this change?

4- What the <0,0,0,0> means? C:=LinearAlgebra:-LinearSolve(A10,<0,0,0,0>,free=p); help of Maple is not very clear on it. 

5- And last one: Why do you subs the the next coefficients by -2 and 3 ?? 
param1:={_C1=3,_C2=-2,L=1,K=1,c=r[1]};


Really, thanks very very much for your help and time. 

ger89

Hi again @Carl Love 

I'm sorry, because this is a stupid mistake. I'm really sorry, i should realise of that. 

I though it's works... but after 810 seconds of computations, Maple shows me this error:

"

Error, (in PDEtools:-casesplit) improper op or subscript selector

"

Thanks again!

Hi @Carl Love 

I eliminate the first brakets, changing this line:

conds := w(0, t) = 0, (D[1](w))(0, t) = 0, eval(I*E*(D[1, 1](w))(x, t), x = L) = 0, eval(I*E*(D[1, 1, 1](w))(x, t), x = L) = 0;

and I get this

Error, (in pdsolve/sys/info) not a system with respect to the unknowns [w(u, t)]