how can i solve this error

i writed this code and i want to integral the sum of Egb and Egs but i get this error

Error using integral (line 82)
First input argument must be a function handle.

and this error

Error in figure (line 28)
Eg=integral(Egs+Egb,0,TETAmax,TETA);

this is the code

clc 
clear all
syms TETA 
S0=613e9;
Sp=3.7e9;
Rin=27.5e-3;
Rout=31.5e-3;
h=15e-3;
for t=0.001:0.0001:0.0014;
TETAmax=-3.661*((h/t)^-1.14)+2.589;
DELTAmax=h-t-(h/(2*TETAmax));
R=Rin+(t/2);
Egb=pi*S0*(t^2)*((TETA*4*R)+h-(h*cos(TETA)))/((3^(0.5))*(TETA))
Egs=pi*S0*(h^2)*t*(TETA*sin(TETA)+cos(TETA)-1)/(2*(TETA)^2)
Eg=integral(Egs+Egb,0,TETAmax,TETA);
end

what is wrong?thank you for your help.

Answer 1

[Walter Roberson]

integral() is reserved for numeric integration. You are doing integration of symbolic expression. You need to use int() or vpaintegral() for that.

[sajjad barzigar]

i changed the code and now i am getting this error .what is the problem now?

Attempt to reference field of non-structure array.

Error in isAllVars (line 9)

res = strcmp(mupadmex('symobj::isAllVars',expr.s,0),'TRUE');

Error in sym/int (line 150)

if ~isscalar(x) || ~isAllVars(x)

Error in figure (line 32)

Eg=int(Es,0,TETAmax,TETA)

this is the code:

clc

clear all

syms TETA

S0=613e9;

Sp=3.7e9;

Rin=27.5e-3;

Rout=31.5e-3;

h=15e-3;

for t=0.001:0.0001:0.0014;

TETAmax=-3.661*((h/t)^-1.14)+2.589;

DELTAmax=h-t-(h/(2*TETAmax));

R=Rin+(t/2);

Egb=pi*S0*(t^2)*((TETA*4*R)+h-(h*cos(TETA)))/((3^(0.5))*(TETA));

Egbs=simplify(Egb);

Egs=pi*S0*(h^2)*t*(TETA*sin(TETA)+cos(TETA)-1)/(2*(TETA)^2);

Egss=simplify(Egs);

E=Egbs+Egss;

Es=simplify(E)

Eg=int(Es,0,TETAmax,TETA)

end

please help me .ty

[Walter Roberson]

Eg=int(Es, TETA, 0, TETAmax)

[sajjad barzigar]

thanks

[sajjad barzigar]

i want to plot the change in Eg base on the change in t and i used a for loop but it only shows me the Eg fot t=0.0014 but i need a vector so i can plot it.how can i solve this?

clc 
clear all
syms TETA 
S0=613e9;
Sp=3.7e9;
Rin=27.5e-3;
Rout=31.5e-3;
h=15e-3;
for t=0.001:0.0001:0.0014;
TETAmax=-3.661*((h/t)^-1.14)+2.589;
DELTAmax=h-t-(h/(2*TETAmax));
R=Rin+(t/2);
eg=pi*S0*t*(((3^0.5)*h^2)+2*h*t+4*pi*R*t)/(2*(3^0.5));
pg=eg/(h-2*t);
et=eg+pi*((Rin)^2)*Sp*(h-2*t);
pt=pg+pi*((Rin)^2)*Sp;
Egb=pi*S0*(t^2)*((TETA*4*R)+h-(h*cos(TETA)))/((3^(0.5))*(TETA));
Egbs=simplify(Egb);
Egs=pi*S0*(h^2)*t*(TETA*sin(TETA)+cos(TETA)-1)/(2*(TETA)^2);
Egss=simplify(Egs);
E=Egbs+Egss;
Es=simplify(E);
Eg=int(Es,TETA,0,TETAmax);
end
plot(t,Eg,'g')
grid on

thank you so much for your help

[Walter Roberson]

syms TETA 
S0=613e9;
Sp=3.7e9;
Rin=27.5e-3;
Rout=31.5e-3;
h=15e-3;
tvals=0.001:0.0001:0.0014;  %note this is only 5 values
num_t = length(tvals);
Eg = zeros(1, num_t, 'sym');

for tidx = 1 : num_t
    t = tvals(tidx);
    TETAmax=-3.661*((h/t)^-1.14)+2.589;
    DELTAmax=h-t-(h/(2*TETAmax));
    R=Rin+(t/2);
    eg=pi*S0*t*(((3^0.5)*h^2)+2*h*t+4*pi*R*t)/(2*(3^0.5));
    pg=eg/(h-2*t);
    et=eg+pi*((Rin)^2)*Sp*(h-2*t);
    pt=pg+pi*((Rin)^2)*Sp;
    Egb=pi*S0*(t^2)*((TETA*4*R)+h-(h*cos(TETA)))/((3^(0.5))*(TETA));
    Egbs=simplify(Egb);
    Egs=pi*S0*(h^2)*t*(TETA*sin(TETA)+cos(TETA)-1)/(2*(TETA)^2);
    Egss=simplify(Egs);
    E=Egbs+Egss;
    Es=simplify(E);
    Eg(tidx) = int(Es,TETA,0,TETAmax);
end

Egn = double(Eg);
plot(tvals, Egn, 'g')
grid on

I would recommend that you consider using vpaintegral() instead of int(), and that you consider using more time points

[sajjad barzigar]

THANK YOU SO MUCH.

[sajjad barzigar]

i want to solve this equation and find teta as a function of t and h.how should i do this?

this is the equation:

(h/t)-(2*teta/(2*sin(teta)-1))=0

i should get this answer from matlab(TETA=-3.661*((h/t)^-1.14)+2.589).how can i get this answer from matlab?

[Walter Roberson]

Let h/t = 2 . Then your expression would give -3.661*(2)^-1.14)+2.589 which is about 0.927786186 .

However, 2-(2*teta/(2*sin(teta)-1)) does not have any root near 0.92: the only real root for it is -2.380061273 approximately.

Therefore you should not get that expression, whatever you do get.

[sajjad barzigar]

i got this equation and the answer from this article(experimental and theoretical investigations on axial crushing of aluminum foam-filled grooved tube(Yao2019))which you can easily find in google scholar.

in this article in equation 5 and 6 you can see that the authur mentions that the answer to the equation is the answer that i mentioned before.i dont know i am wrong or they are because thats an approved and published article.they said by using matlab you can solve the equation and find the answer below.

(TETA=-3.661*((h/t)^-1.14)+2.589).

are they wrong or i am ?

[Walter Roberson]

What is the valid range of values for h/t ? Sometimes equations are approximately valid within a particular range of interest while being too wrong outside of the area of interest.

[sajjad barzigar]

normaly between 12 to 20 i think.but they didnt mention any kind of valid range for the answer.

[sajjad barzigar]

any way thank you for every thing :)