Try to make a function for deflection and is just dosen`t want to work.

Hello here is the task what I need to do. I been only able to do some part of it and not really knw why is my code not want to work. Tried use the help, but still cant figure it out what is the problem.

The maximum deflexion of a wind turbine blade should be no more than 10% of its span. The formula used to calculate deflexion being: Delta = (W*L.^3)/(8*E*I)

Where D is the deflexion in mm and L is the length of the blade, mm. Given that the maximum load (W) to be applied to the blade is 8500N, E the elastic modulus of the blade material is 42000 N/mm2, I is 10 million mm4. Create a MATLAB function to determine whether the deflexion of the blade will exceed design parameters or not. Your function should require Length as an input and return the resulting deflection as an output

As a secondary output, the function should also display one of two lines ’Maximum deflexion is tolerable ’ or ’Maximum deflexion will be exceeded’ depending on the value of delta. Demonstrate your code working for the following lengths;

1. 4.2m

2. 10m

3. 25m

Calculate the MAXIMUM tolerable blade length (hint: calculate L when ∆/L = 0.1)

My Code:

function deflection = Wind_turbinDef()
    L= input('Lenght of the wind turbine blade in meter: ')*u.m; %Use this input to we can measure the blead deflexion in any lenght.
    L=unitConvert(L,u.mm); %The lenght mast be in mm to be able to use in the formular so needed to comvert it.
    W=8500*u.N; %The walue is the maximu constant 
    E=42000 *u.N/u.mm^2; %Elastic modulus of the blade
    I=10*(10^6)*u.mm^4; 
    Delta=vpa((W*L^3)/(8*E*I));% Used vpa() to simplify the last division on the deflexion formular

    %max deflexion is 10% from it span
    Lim=L*0.1;
    
   deflection = Delta-Lim;
   
        if deflection < 0
            Deflection= "Maximum deflexion is tolerable!";
        elseif deflection == 0
            Deflection = "Maximum deflexion is tolerable!";
        else deflection > 0
            Deflection = "Maximum deflexion will be exceeded!";
        end
   
end

Thank you for any help!

[John D'Errico]

Edit to make code more readable.

[Milan Sumegi]

Edit what?

[Walter Roberson]

Your code does not display the required messages .

Your function should take the length as a parameter instead of using input()

Your code does not define u for u.mm

why are you expecting the length in metres when all of the sample inputs are mm ?

[Milan Sumegi]

Walter sorry wrote it wrong, changed it now. Cos some of the date in meter so I need to changed them to mm to get it work. Am I right?

Ok I try to change thanks

Answer 1

[Stephen23]

Simpler:

>> W = 8500;  % max load (N)
>> E = 42000; % elastic modulus (N/mm^2)
>> I = 10e6;  % ??? (mm^4)
>> Dfun = @(L) (W*L.^3)/(8*E*I); % blade length (mm)
>> D = Dfun([4.2,2.10,3.25]*1000)
D =
   187.425    23.428    86.842
>> Lmax = fzero(@(L)Dfun(L)/L-0.1,[1,1e6])
Lmax =  6287.2

And this is easy to check by plotting:

>> Lv = 1:1e4;
>> Rv = Dfun(Lv)./Lv;
>> plot(Lv,Rv)
>> hold on
>> plot(Lmax,0.1,'*r')
>> xlabel('blade length (mm)')
>> ylabel('ratio D/L')

[Milan Sumegi]

Hi Stephen

This is the answare to work out the MAXIMUM tolerable blade length. Right?

That is ok but I need to be able to get those messages out from the if statement to for the first part of the excersize.

Thank you! your answare is really helpfull anyway

Can you please explain me the line with fzero? not really understand. :(

Thanks

[Milan Sumegi]

Ok i got the work outs now just cant figure it out how to make it right for this bit. as asking me a secondary output.

"As a secondary output, the function should also display one of two lines ’Maximum deflexion is tolerable ’ or ’Maximum deflexion will be exceeded’ depending on the value of delta. Demonstrate your code working for the following lengths; "

[Stephen23]

@Milan Sumegi: use if or indexing:

>> Lw = [4.2,2.10,3.25,7]*1000
Lw =
   4200   2100   3250   7000
>> Dw = Dfun(Lw)
Dw =
   187.425    23.428    86.842   867.708
>> Rw = Dw./Lw
Rw =
   0.044625   0.011156   0.026721   0.123958
>> C = {'is tolerable','will be exceeded'};
>> D = [num2cell(Lw);C(1+(Rw>0.1))];
>> fprintf('Length %d maximum deflection %s\n',D{:})
Length 4200 maximum deflection is tolerable
Length 2100 maximum deflection is tolerable
Length 3250 maximum deflection is tolerable
Length 7000 maximum deflection will be exceeded

[Milan Sumegi]

Many thanks Stephen

Answer 2

[Milan Sumegi]

Tried make it differently but had not a clue how to change it to work.

u=symunit; 
format short g
L= input('Lenght of the wind turbine blade in meter: ')*u.m; 
L=unitConvert(L,u.mm); 
W=8500*u.N; 
E=42000 *u.N/u.mm^2; 
I=10*(10^6)*u.mm^4; 
format long g
Delta=vpa((W*L1^3)/(8*E*I))
Tol=0.1;


function [MaxDefl] = mycal()

 MaxDefl=vpa(L*Tol);
  
    if MaxDefl>Delta
        disp("Maximum deflexion is tolerable!")
    elseif MaxDefl==Delta
        disp("Maximum deflexion is tolerable!")
    else MaxDefl<Delta
        disp("Maximum deflexion will be exceeded!")
    end
end

Here is another script,