Question: highly nonlinear set of ivp - updated

Dear everyone,

I would be vey glad if you could help me in this.

I have a set of 12 odes. I solve for the 12 dependent variables using dsolve, numeric and then plot their solutions using odeplot. When I omit my highly nonlinear elastic force terms, everything is ok. However, when I include the elastic force terms, dsolve seems to work fine and yield a result, but I cannot substitute the solution coming from dsolve,numeric back into the dependent variables. I get the message "global 'x' must be assigned to a numeric value before obtaining a solution". Well, the only thing I have changed is the elastic force term, and now I don't know what to do! Please help me out in this! Can't maple deal with highly nonlinear problems?

Here's what my code looks like (if I omit the nonlinear elastic force terms in my equations, everything seems to work fine. Is it due to nonlinearity that maple is lost?)

Thank you very much in advance for your help and interestView 14275_shear beam.mw on MapleNet or Download 14275_shear beam.mw
View file details.