See this publication in RG.

Article A NONLINEAR FINITE ELEMENT TOOLBOX FOR STRUCTURAL CONTROL

Get Crisfield's book first!

Hello Ho

Will Suggest book by Prof Bathe

Rgds

R

Thank you.I saw those books.

I can make nonlinear stiffness matrix ,but I can't assemble it.

The matrix have a syms variable and I can't assemble it in matlab software.

Thanks.its helpful....

If your problem is moderately nonlinear, you could use simpler approach by computing:

K(un) un+1 = f,

where un is the previous while un+1 is current iteration.

Hi dear Hossein

Please check

Introduction to Finite Element Analysis using Matlab and Abaqus

Regards

Vahid