How can I write a multifunctions to test exhaustive search method

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Farah Buarki
Farah Buarki 2021-1-8
回答： Zuber Khan 2024-9-20
for example I have 5000*b*d<=36000 and (1.65*10^4)*b*d^2 <=84*10^6 and I want to calculate the new b and d which helps get min cross sectional area but it only works once for one equation .
A=1000;
for b=0:0.01:25
for d=0:0.01:50
%bending stress
if (1.65*10^4)*b*d^2 <=84*10^6
X=(1.65*10^4)*b*d^2;
if A<X
A=X;
bo=b;
do=d;
%check on the constraint
b>=0 ;
d>=0 ;
d-2*b<=0;
% shear stress
if 5000*b*d<=36000
Y=(5000)*b*d;
if A<Y
A=Y;
bo=b;
do=d;
end
end
end
end
end
end
bo
do
A=bo*do
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Mathieu NOE
Mathieu NOE 2021-1-12
hello
I may be wrong, but can we do something more straigthforward using meshgrid ?
like :
A=1000;
b=0:0.01:25;
d=0:0.01:50;
[bb,dd] = meshgrid(b,d);
% criteria 1 , find b,d pairs that fullfill 5000*b*d<=36000 (or b*d<36/5)
prod1 = bb.*dd;
threshold1 = 36/5;
% criteria 2 , find b,d pairs that fullfill (1.65*10^4)*b*d^2 <=84*10^6 (or b*d^2<= 84*10^6 / (1.65*10^4) )
prod2 = bb.*(dd.^2);
threshold2 = 84*10^6 / (1.65*10^4);
ind = find(prod1<threshold1 & prod2<threshold2);
bb_sol = bb(ind);
dd_sol = dd(ind);
plot(bb_sol,dd_sol,'+');grid
xlabel('b');
ylabel('d');

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回答（1 个）

Zuber Khan
Zuber Khan 2024-9-20
Hi,
Based on my understanding of the question, it seems you are looking for a function based design of your exhaustive search problem. I have implemented the same and you can check it as follows.
function [bo, do, A] = evaluateCrossSection()
% Initialize variables
A = 1000; % Area
% Iterate over possible values of b and d
for b = 0:0.01:25
for d = 0:0.01:50
% Bending stress constraint
if bendingstress(b,d)
% Area check
if AreaCheck(A,b,d)
A= (1.65*10^4)*b*d^2;
bo = b;
do = d;
% Check for valid values
if isValid(b, d)
currentArea = b * d;
% Update area if less than a certain value
if A < 5000*currentArea
A = 5000*currentArea;
bo = b;
do = d;
end
end
end
end
end
end
% Display the results
fprintf('Optimal b: %.2f\n', bo);
fprintf('Optimal d: %.2f\n', do);
fprintf('Minimum Cross-Sectional Area: %.2f\n', bo*do);
end
function valid = isValid(b, d)
% Check all constraints
valid = (1.65 * 10^4) * b * d^2 <= 84 * 10^6 && ...
5000 * b * d <= 36000 && ...
b >= 0 && ...
d >= 0 && ...
d - 2 * b <= 0;
end
function valid = AreaCheck(A,b,d)
% Check all constraints
valid = A<(1.65*10^4)*b*d^2;
end
function valid = bendingstress(b,d)
% Check all constraints
valid = (1.65*10^4)*b*d^2 <=84*10^6;
end
Based on the constraints provided, it generates the following output:
Optimal b: 3.52
Optimal d: 38.03
Minimum Cross-Sectional Area: 133.87
I have checked for each iteration and the magnitude of cross sectional area is changing before it attains the final value. You can modify the above code and pass the equations as arguement to make it more generic.
In case you are not getting the desired result, I would suggest you to carefully examine the constraints involved as well as the area update loop to check for any missing information.
I hope it will address your concerns.
Regards,
Zuber

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