0 个投票

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.

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 采纳的回答

Walter Roberson
Walter Roberson 2020-8-2

0 个投票

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

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sajjad barzigar
sajjad barzigar 2020-8-2
编辑：sajjad barzigar 2020-8-2
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
sajjad barzigar
sajjad barzigar 2020-8-3
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
Walter Roberson 2020-8-4
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
sajjad barzigar 2020-8-4
THANK YOU SO MUCH.
sajjad barzigar
sajjad barzigar 2020-8-4
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
Walter Roberson 2020-8-4
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
sajjad barzigar 2020-8-4
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
Walter Roberson 2020-8-4
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
sajjad barzigar 2020-8-4
normaly between 12 to 20 i think.but they didnt mention any kind of valid range for the answer.
sajjad barzigar
sajjad barzigar 2020-8-4
any way thank you for every thing :)

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