1. The problem statement, all variables and given/known data I am analyzing the deflection of clamped circle polysilicon membrane with radius=1500 um and thickness=1 um. The load is constant pressure ranging from 20 uPa to 20kPa. The problem is that my analytical solution doesn't agree with the ANSYS solution. 2. Relevant equations 2.1. Timoshenko gave me formulas for linear, non-linear and membrane regions of displacement. See the 1st attachment "pic1.png" for formulas and figures depicting them. 2.2. 1st ANSYS model is axisymmetric, consists of plane42 elements 2.3. 2nd model is made of shell181 elements both input files are in attachment "input.txt" 3. The attempt at a solution The solution data that I get from ANSYS is on 2nd attachment "pic2.png". The ANSYS and analytical graphs differ and that's the problem. I suspect that the problem is in my ANSYS model. Any comments will be appreciated.