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ME_3255_Final_Project/SE_diff.m
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function [pw_se,w] = SE_diff(T,P,n) | |
% function that calculates the difference between | |
% strain energy and work done by pressure on the membrane. | |
% Input: | |
% T = tension per unit length (uN/um) | |
% P = pressure (MPa) | |
% n = # of interior node rows/columns | |
% Output: | |
% pw_se = Absolute value of difference between strain energy and work done by pressure | |
% w = displacement vector for interior nodes | |
E = 1e6; % 1 TPa ~= 10^6 MPa | |
t = 3*10^-4; % thickness [um] | |
h = 10/(n+1); % height [um] | |
v = 0.31; % Poisson's Ratio | |
% Displacement vector w found using Part C | |
w = membrane_solution(T,P,n); | |
z = zeros(n + 2); | |
z(2:end-1,2:end-1) = reshape(w,[n n]); | |
% Calculate average displacement, wavg, for each element by taking the displacement at each | |
% corner and then average the found values. | |
num = n + 1; | |
wavg = zeros(num); | |
for i = 1:num | |
for j = 1:num | |
wavg(i,j) = mean([z(i,j),z(i+1,j),z(i,j+1),z(i+1,j+1)]); | |
end | |
end | |
% final work done by pressure | |
pw = sum(sum(wavg.*h^2.*P)) | |
% to find= change in displacement, find the change in displacement on | |
% the x-axis, dwdx, and the change in displacement on the y-axis, dwdy, and | |
% average the found values. | |
dwdx = zeros(num); | |
dwdy = zeros(num); | |
for i = 1:num | |
for j = 1:num | |
dwdx(i,j) = mean([z(i+1,j)-z(i,j),z(i+1,j+1)-z(i,j+1)]); | |
dwdy(i,j) = mean([z(i,j+1)-z(i,j),z(i+1,j+1)-z(i+1,j)]); | |
end | |
end | |
% Using dwdx and dwdy, calculate the strain energy, se. | |
se = (E*t*h^2)/(2*(1-v^2)) * sum(sum((1/4).*dwdx.^4+(1/4).*dwdy.^4+(1/4).*(dwdx.*dwdy).^2)); | |
% Final value of difference between strain energy and work done by pressure | |
pw_se = pw - se; |