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Computer Science Physics

Calculation of an integral with a variable lower limit using the trapezoidal method

Yaroslav B

Posted 9 hours ago

Please tell me what is my mistake in implementing the calculation of the integral with a variable lower limit using the trapezoid method? b[t_]:=t;(a=1;) SigmaRhoBegin[rho_,phi_]=0; (Print["SigmaRhoBegin = ",SigmaRhoBegin[rho,phi]];) SigmaRhoPhiBegin[rho_,phi_]=0; (Print["SigmaRhoPhiBegin = ",SigmaRhoPhiBegin[rho,phi]];) (delta=0;(deltamin)) (delta=0.1a;(deltasr)) (delta=0.7a;(deltamax)) delta=0.1; (bend=2a;) (L=bend+delta+0.1a;(Lmin)) (L=bend+delta+0.3a;(Lsr)) (L=(bend+delta+0.1a)5;(Lmax)) L=2.2; varepsnom[rho_]=0.001; F[rho_,phi_]=(lambdaCos[phi]+rho/L)Cos[phi]-Sqrt[1-(lambdaCos[phi]+rho/L)^2]Sin[phi]; lambda=delta/L; varepsilon[rho_,phi_]=(varepsnom[rho]+1)Sqrt[1+(lambda^2-2lambdaF[rho,phi])/(1-(rho/L)^2)]-1; nu=0.23; EE=2G(1+nu); SigmaPhiBegin[rho_,phi_]=EEvarepsilon[rho,phi]/G; Print["SigmaPhiBegin = ",SigmaPhiBegin[rho,phi]]; (Print["Min[oldp[rho,phi]] = ",NMinimize[SigmaPhiBegin[2(rho),phi],-Pi<=phi<=Pi,phi]];) Show[ Plot[({SigmaPhiBegin[1,phi],SigmaPhiBegin[1.2,phi],SigmaPhiBegin[1.4,phi],SigmaPhiBegin[1.6,phi],SigmaPhiBegin[1.8,phi],SigmaPhiBegin[2,phi]},)SigmaPhiBegin[1.0,phi],{phi,-Pi,Pi}, AxesLabel->{"phi","Subscript[\[Sigma], \[Phi]\[Phi]]^[rho,phi]"}, PlotRange->{{-Pi,Pi},{-0.8,0.7}}, GridLines->{Range[-3.4,3.4,0.2],Range[-0.8,0.7,0.05]}, PlotLegends->{"Subscript[\[Sigma], \[Phi]\[Phi]]^[1.0,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^[1.2,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^[1.4,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^[1.6,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^[1.8,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^[2.0,phi]"} ], Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.8},{0,0.7}}]}] ] {MAX,{max}}=Maximize[SigmaPhiBegin[1.0,phi],-Pi<=phi<=Pi,phi]; Print["Maximize[SigmaPhiPhiBegin[1.0,",max,"]] = ",MAX]; {MIN,{min}}=Minimize[SigmaPhiBegin[1.0,phi],-Pi<=phi<=Pi,phi]; Print["Minimize[SigmaPhiPhiBegin[1.0,",min,"]] = ",MIN]; (--------------------------------------------------------------------------------------------------------------------------------) qbegin[rho_,phi_]=D[SigmaRhoPhiBegin[rho,phi],rho]+(D[SigmaPhiBegin[rho,phi],phi]+2SigmaRhoPhiBegin[rho,phi])/rho; q[t_,phi_]=qbegin[b[t],phi]D[b[t],t]; (Print["q[t,phi] = ",q[t,phi]];) pbegin[rho_,phi_]=D[SigmaRhoBegin[rho,phi],rho]+(D[SigmaRhoPhiBegin[rho,phi],phi]+SigmaRhoBegin[rho,phi]-SigmaPhiBegin[rho,phi])/rho; p[t_,phi_]=-pbegin[b[t],phi]D[b[t],t]; (Print["p[t,phi] = ",p[t,phi]];) (--------------------------------------------------------------------------------------------------------------------------------) (--------------------------------------------------------------------------------------------------------------------------------) dotsigmarhophi[t_,phi_]=q[t,phi]; (Print["dotsigmarhophi[t,phi] = ",dotsigmarhophi[t,phi]];) dotsigmarhorho[t_,phi_]=-p[t,phi]; (Print["dotsigmarhorho[t,phi] = ",dotsigmarhorho[t,phi]];)dotsigmaphiphi[t_,phi_]=D[dotsigmarhophi[t,phi],phi]+(tD[dotsigmarhorho[t,phi],t]+dotsigmarhorho[t,phi]); (Print["dotsigmaphiphi[t,phi] = ",dotsigmaphiphi[t,phi]];) (--------------------------------------------------------------------------------------------------------------------------------) (------------------------------------------------------------------------------------------------------------------------------) Show[ Plot[{dotsigmarhophi[1,phi],dotsigmarhophi[1.2,phi],dotsigmarhophi[1.4,phi],dotsigmarhophi[1.6,phi],dotsigmarhophi[1.8,phi],dotsigmarhophi[2,phi]},{phi,-Pi,Pi}, AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][t,phi]"}, PlotRange->{{-Pi,Pi},{-0.4,0.5}}, GridLines->{Range[-3.4,3.4,0.2],Range[-0.4,0.5,0.05]}, PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][2.0,phi]"}], Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.4},{0,0.5}}]}] ] Show[ Plot[{dotsigmarhorho[1,phi],dotsigmarhorho[1.2,phi],dotsigmarhorho[1.4,phi],dotsigmarhorho[1.6,phi],dotsigmarhorho[1.8,phi],dotsigmarhorho[2,phi]},{phi,-Pi,Pi}, AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][t,phi]"}, PlotRange->{{-Pi,Pi},{-0.4,0.5}}, GridLines->{Range[-3.4,3.4,0.2],Range[-0.4,0.5,0.05]}, PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][2.0,phi]"}], Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.4},{0,0.5}}]}] ] Show[ Plot[{dotsigmaphiphi[1,phi],dotsigmaphiphi[1.2,phi],dotsigmaphiphi[1.4,phi],dotsigmaphiphi[1.6,phi],dotsigmaphiphi[1.8,phi],dotsigmaphiphi[2,phi]},{phi,-Pi,Pi}, AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][t,phi]"}, PlotRange->{{-Pi,Pi},{-3,5}}, GridLines->{Range[-3.4,3.4,0.2],Range[-3,5,0.5]}, PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][2.0,phi]"}], Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-3},{0,5}}]}] ] (------------------------------------------------------------------------------------------------------------------------------) (------------------------------------------------------------------------------------------------------------------------------) fitWithAdaptiveOrder[T_,f_]:= Module[{func,m,data,model,vars,fit,approx,epsilon,cleanFit}, epsilon=0.01; func[t_,phi_]:=f[t,phi]; m=3; While[True, data=Table[{phi,func[T,phi]},{phi,-Pi,Pi,Pi/m}]; model=a0+Sum[ak[k]Cos[kphi]+bk[k]Sin[kphi],{k,1,Ceiling[m/2]-1}]; vars=Join[{a0},Flatten[Table[{ak[k],bk[k]},{k,1,Ceiling[m/2]-1}]]]; fit=FindFit[data,model,vars,phi]; (cleanFit=fit/.Rule[coeff_,val_]:>Rule[coeff,If[Abs[val]<10^(-10),0,val]]; approx=model/.cleanFit;) approx=model/.fit; (If[func[T,phi]!=0,) If[Max[Abs[Table[Abs[(approx-func[T,phi])/func[T,phi]]/. phi->x,{x,-Pi,Pi,Pi/m}]]]<epsilon,Break[]];(, If[Max[Abs[Table[Abs[approx-func[T,phi]/.{ phi->x}],{x,-Pi,Pi,Pi/m}]]]<epsilon,Break[]];(Если Delta=0) ];) m=m+1; ]; approx]; (------------------------------------------------------------------------------------------------------------------------------) (------------------------------------------------------------------------------------------------------------------------------) approxFunction1[t_,theta_]:=fitWithAdaptiveOrder[t,q]/.{phi->theta}; Time=2.0;Phi=Pi/2; Print["approxFunction1[",Time,",pHi] = ",approxFunction1[Time,pHi]]; Print["approxFunction1[",Time,",",Phi,"] = ",approxFunction1[Time,Phi]]; Print["q[",Time,",",Phi,"] = ",approxFunction1[Time,Phi]]; (------------------------------------------------------------------------------------------------------------------------------) (------------------------------------------------------------------------------------------------------------------------------) timebeginRP=AbsoluteTime[]; uRP=0.4; flagI1nRP=True; epsilonRP=0.0002; delta2nRP=100.; NNRP=100; I1nRP=Table[-100.,{i,1,NNRP}];I2nRP=Table[-100.,{i,1,NNRP}]; X1nRP=Table[-100.,{i,1,NNRP}];X2nRP=Table[-100.,{i,1,NNRP}]; Y1nRP=Table[-100.,{i,1,NNRP}];Y2nRP=Table[-100.,{i,1,NNRP}]; rho0RP=1; rhofRP=2; t0RP=1; tfRP=2; While[delta2nRP>epsilonRP, delta2nRP=-1.; uRP=uRP/2; I1nRP=I2nRP; I2nRP=Table[-100.,{i,1,NNRP}]; X1nRP=X2nRP; Y1nRP=Y2nRP; Do[(For[v=1,v<=2,v=v+1,) If[v==2\|\|(v==1&&flagI1nRP==True), flagI1nRP=False; flagRP=v==1; dtRP=uRP/v;(integration step) (number of time segments. (+1) to take into account the tfRP time point, which we will add artificially) iendRP=Round[(tfRP-t0RP)/dtRP]+1; fouriendRP=4iendRP+1;(number of grid division angles. (+1) to include Pi) spisoksigmaPSKRP=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRP}],{s,1,iendRP}],{i,1,iendRP}]; Do[(For[i=1,i<=iendRP,i=i+1,)(RHO radius cycle) tempRP=t0RP+(i-1)dtRP;(current time layer) RhoRP=rho0RP+(i-1)dtRP;(current radius) (at each new time layer-radius we initialize the initial value of the function) sigmanewValRP=SigmaRhoPhiBegin[tempRP,phi]; Do[(For[t=tempRP,t<=tfRP-dtRP,t=t+dtRP,)(Time cycle T) sigmanewValRP=sigmanewValRP+dtRP(fitWithAdaptiveOrder[t,dotsigmarhophi]+fitWithAdaptiveOrder[t+dtRP,dotsigmarhophi])/2/.{phi->theta}; (Print["sigmanewValRP = ",sigmanewValRP];) timeRP=Round[(t-t0RP)/dtRP]+1; Do[(For[j=1,j<=fouriendRP,j=j+1,)(Cycle by angle PHI) thetaRP=-(Pi+(2Pi)/(4iendRP))+(2Pij)/(4iendRP);(-Pi<=phi<=Pi) resRP=Evaluate[sigmanewValRP/.{theta->thetaRP}]; If[v==1, spisoksigmaPSKRP[[i]][[timeRP]][[j]]={RhoRP,thetaRP,resRP};,(filled only on the first iteration, then blocked) spisoksigmaPSKRP[[i]][[timeRP+1]][[j]]={RhoRP,thetaRP,resRP};(filled in at each iteration) ]; If[t==tfRP-dtRP&&resRP>I1nRP[[i]]&&flagRP==True,(we are looking for the maximum value of the integral on the penultimate time layer) I1nRP[[i]]=resRP; X1nRP[[i]]=RhoRP; Y1nRP[[i]]=thetaRP; ]; If[t==tfRP-dtRP&&resRP>I2nRP[[i]]&&flagRP==False, I2nRP[[i]]=resRP; X2nRP[[i]]=RhoRP; Y2nRP[[i]]=thetaRP; ]; (Angle (theta(phi)) from -Pi to Pi) ,{j,1,fouriendRP,1}];(];) (Cycle to the penultimate time layer, since the trapezoid method uses the current and next steps) ,{t,tempRP,tfRP-dtRP,dtRP}];(];) (Rho radii from 1.0 to 1.9, since we don’t add anything to the first one, since (i-1)dt) ,{i,1,iendRP,1}];(];) ]; (we calculate the integral with step h, then with step h/2 and compare the results using the Runge method, we calculate both integrals only at the 1st iteration, and then flag=False) ,{v,1,2,1}];(];) Do[(For[z=1,z<=NNRP/2,z=z+1,) errorRP=Abs[I2nRP[[2z-1]]-I1nRP[[z]]]/3; If[delta2nRP<errorRP, delta2nRP=errorRP; iiRP=z; ]; ,{z,1,NNRP/2,1}];(];) Print["------------------------------------------------------------------------------------------------------------------------"]; Print["ii = ",iiRP,", u = ",uRP]; Print["I1n[",X1nRP[[iiRP]],",",Y1nRP[[iiRP]],"] = ",I1nRP[[iiRP]],", I2n[",X2nRP[[2iiRP-1]],",",Y2nRP[[2iiRP-1]],"] = ",I2nRP[[2iiRP-1]],", delta2n = ",delta2nRP]; ]; timeendRP=AbsoluteTime[]; Print["Time: ",(timeendRP-timebeginRP)/60]; Do[(For[i=1,i<=iendRP,i=i+1,) RhoRP=rho0RP+(i-1)dtRP; Do[(For[Time=t0RP,Time<=tfRP,Time=Time+dtRP,) newtimeRP=Round[(Time-t0RP)/dtRP]+1; If[i==newtimeRP(&&RhoRP>1.), Do[ thetaRP=-(Pi+(2Pi)/(4iendRP))+(2Pij)/(4iendRP); resRP=SigmaRhoPhiBegin[RhoRP,thetaRP]; spisoksigmaPSKRP[[i]][[newtimeRP]][[j]]={RhoRP,thetaRP,resRP}; (If[RhoRP>1.0, XRP=RhoRPCos[thetaRP]; YRP=RhoRPSin[thetaRP]; spisoksigmaDSKRP[[i]][[newtimeRP]][[j]]={XRP,YRP,resRP}; ];) ,{j,1,fouriendRP,1}]; ]; ,{Time,t0RP,tfRP,dtRP}];(];) ,{i,1,iendRP,1}];(];) (------------------------------------------------------------------------------------------------------------------------------) (------------------------------------------------------------------------------------------------------------------------------) timebeginRR=AbsoluteTime[]; uRR=0.4; flagI1nRR=True; epsilonRR=0.0001; delta2nRR=100.; NNRR=100; I1nRR=Table[-100.,{i,1,NNRR}];I2nRR=Table[-100.,{i,1,NNRR}]; X1nRR=Table[-100.,{i,1,NNRR}];X2nRR=Table[-100.,{i,1,NNRR}]; Y1nRR=Table[-100.,{i,1,NNRR}];Y2nRR=Table[-100.,{i,1,NNRR}]; rho0RR=1; rhofRR=2; t0RR=1; tfRR=2; While[delta2nRR>epsilonRR, delta2nRR=-1.; uRR=uRR/2; I1nRR=I2nRR; I2nRR=Table[-100.,{i,1,NNRR}]; X1nRR=X2nRR; Y1nRR=Y2nRR; Do[(For[v=1,v<=2,v=v+1,) If[v==2\|\|(v==1&&flagI1nRR==True), flagI1nRR=False; flagRR=v==1; dtRR=uRR/v; iendRR=Round[(tfRR-t0RR)/dtRR]+1; fouriendRR=4iendRR+1; (spisoksigmaDSKRR=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRR}],{s,1,iendRR}],{i,1,iendRR}];) spisoksigmaPSKRR=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRR}],{s,1,iendRR}],{i,1,iendRR}]; Do[(For[i=1,i<=iendRR,i=i+1,) tempRR=t0RR+(i-1)dtRR; RhoRR=rho0RR+(i-1)dtRR; sigmanewValRR=SigmaRhoBegin[tempRR,phi]; Do[(For[t=tempRR,t<=tfRR-dtRR,t=t+dtRR,) sigmanewValRR=sigmanewValRR+dtRR(fitWithAdaptiveOrder[t,dotsigmarhorho]+fitWithAdaptiveOrder[t+dtRR,dotsigmarhorho])/2/.{phi->theta}; timeRR=Round[(t-t0RR)/dtRR]; Do[(For[j=1,j<=fouriendRR,j=j+1,) thetaRR=Evaluate[-(Pi+(2Pi)/(4iendRR))+(2Pij)/(4iendRR)];(-Pi<=Phi<=Pi) resRR=Evaluate[sigmanewValRR/.{theta->thetaRR}]; If[v==1, spisoksigmaPSKRR[[i]][[timeRR+1]][[j]]={RhoRR,thetaRR,resRR};, spisoksigmaPSKRR[[i]][[timeRR+2]][[j]]={RhoRR,thetaRR,resRR}; ]; If[t==tfRR-dtRR&&resRR>I1nRR[[i]]&&flagRR==True, I1nRR[[i]]=resRR; X1nRR[[i]]=RhoRR; Y1nRR[[i]]=thetaRR; ]; If[t==tfRR-dtRR&&resRR>I2nRR[[i]]&&flagRR==False, I2nRR[[i]]=resRR; X2nRR[[i]]=RhoRR; Y2nRR[[i]]=thetaRR; ]; ,{j,1,fouriendRR,1}];(];) ,{t,tempRR,tfRR-dtRR,dtRR}];(];) ,{i,1,iendRR,1}];(];) ]; ,{v,1,2,1}];(];) Do[(For[z=1,z<=NNRR/2,z=z+1,) errorRR=Abs[I2nRR[[2z-1]]-I1nRR[[z]]]/3; If[delta2nRR<errorRR, delta2nRR=errorRR; iiRR=z; ]; ,{z,1,NNRR/2,1}];(];) Print["------------------------------------------------------------------------------------------------------------------------"]; Print["ii = ",iiRR,", u = ",uRR]; Print["I1n[",X1nRR[[iiRR]],",",Y1nRR[[iiRR]],"] = ",I1nRR[[iiRR]],", I2n[",X2nRR[[2iiRR-1]],",",Y2nRR[[2iiRR-1]],"] = ",I2nRR[[2iiRR-1]],", delta2n = ",delta2nRR]; ]; timeendRR=AbsoluteTime[]; Print["Time: ",(timeendRR-timebeginRR)/60]; Do[(For[i=1,i<=iendRR,i=i+1,) RhoRR=rho0RR+(i-1)dtRR; Do[(For[Time=t0RR,Time<=tfRR,Time=Time+dtRR,) newtimeRR=Round[(Time-t0RR)/dtRR]+1; If[i==newtimeRR(&&RhoRR>1.), Do[ thetaRR=Evaluate[-(Pi+(2Pi)/(4iendRR))+(2Pij)/(4iendRR)]; resRR=SigmaRhoBegin[RhoRR,thetaRR]; spisoksigmaPSKRR[[i]][[newtimeRR]][[j]]={RhoRR,thetaRR,resRR}; (If[RhoRR>1., XRR=RhoRRCos[thetaRR]; YRR=RhoRRSin[thetaRR]; spisoksigmaDSKRR[[i]][[newtimeRR]][[j]]={XRR,YRR,resRR}; ];) ,{j,1,fouriendRR,1}]; ]; ,{Time,t0RR,tfRR,dtRR}];(];) ,{i,1,iendRR,1}];(];) (------------------------------------------------------------------------------------------------------------------------------) (--------------------------------------------------------------------------------------------------------------------------------) tableRP={}; For[j=1,j<=fouriendRP,j=j+1, If[spisoksigmaPSKRP[[1]][[iendRP]][[j]]!={0.,0.,0.}, tableRP=Append[tableRP,spisoksigmaPSKRP[[1]][[iendRP]][[j]]]; ]; ]; (--------------------------------------------------------------------------------------------------------------------------------) (--------------------------------------------------------------------------------------------------------------------------------) tableRR={}; For[j=1,j<=fouriendRR,j=j+1, If[spisoksigmaPSKRR[[1]][[iendRR]][[j]]!={0.,0.,0.}, tableRR=Append[tableRR,spisoksigmaPSKRR[[1]][[iendRR]][[j]]]; ]; ]; (--------------------------------------------------------------------------------------------------------------------------------) (--------------------------------------------------------------------------------------------------------------------------------) ListLinePlot[ {tableRR,tableRP(,tablePP[iendPP])}/. {a_,b_,c_}:>{b,c}, PlotStyle->Automatic, PlotRange->{{-Pi,Pi},{-0.2,0.2}},({{-Pi,Pi},All},) AxesLabel->{"\[Phi]","\[Sigma]"}, ImageSize->Large, GridLines->{Range[-3.2,3.2,0.2],Range[-0.2,0.2,0.02]} ] (--------------------------------------------------------------------------------------------------------------------------------*) Below I attach 2 graphs. The first one is what should be obtained, the second one is what I get. Note: The problem is that the graphs look the same, but the resulting vertical stress values are different. This is my first time asking a question on this forum. When I click "Reply" for some reason nothing happens, so I'm answering you by editing the original post. Eric, I wrote a program for a general case. Now I am considering a specific model. For which the input data is as follows. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I am considering the problem of body growth. b[t]=t is the growth function. It is the outer radius, t is time. The radius and time are sort of synchronized. The first part of the code is simply formulas rewritten into code. The integration itself begins with: uRP=0.4; flagI1nRP=True; epsilonRP=0.0001; delta2nRP=100.; NNRP=100; ... For the shear stress RR the integration function is similar. The lower integration limit is "t", the upper one is "b(t)", for the model under consideration 1<=t<=2.

Please tell me what is my mistake in implementing the calculation of the integral with a variable lower limit using the trapezoid method?

b[t_]:=t;(*a=1;*)
SigmaRhoBegin[rho_,phi_]=0;
(*Print["SigmaRhoBegin = ",SigmaRhoBegin[rho,phi]];*)
SigmaRhoPhiBegin[rho_,phi_]=0;
(*Print["SigmaRhoPhiBegin = ",SigmaRhoPhiBegin[rho,phi]];*)
(*delta=0;(*deltamin*)*)
(*delta=0.1*a;(*deltasr*)*)
(*delta=0.7*a;(*deltamax*)*)
delta=0.1;
(*bend=2*a;*)
(*L=bend+delta+0.1*a;(*Lmin*)*)
(*L=bend+delta+0.3*a;(*Lsr*)*)
(*L=(bend+delta+0.1*a)*5;(*Lmax*)*)
L=2.2;
varepsnom[rho_]=0.001;
F[rho_,phi_]=(lambda*Cos[phi]+rho/L)*Cos[phi]-Sqrt[1-(lambda*Cos[phi]+rho/L)^2]*Sin[phi];
lambda=delta/L;
varepsilon[rho_,phi_]=(varepsnom[rho]+1)*Sqrt[1+(lambda^2-2*lambda*F[rho,phi])/(1-(rho/L)^2)]-1;
nu=0.23;
EE=2*G*(1+nu);
SigmaPhiBegin[rho_,phi_]=EE*varepsilon[rho,phi]/G;
Print["SigmaPhiBegin = ",SigmaPhiBegin[rho,phi]];
(*Print["Min[oldp[rho,phi]] = ",NMinimize[SigmaPhiBegin[2(*rho*),phi],-Pi<=phi<=Pi,phi]];*)
Show[
Plot[(*{SigmaPhiBegin[1,phi],SigmaPhiBegin[1.2,phi],SigmaPhiBegin[1.4,phi],SigmaPhiBegin[1.6,phi],SigmaPhiBegin[1.8,phi],SigmaPhiBegin[2,phi]},*)SigmaPhiBegin[1.0,phi],{phi,-Pi,Pi},
AxesLabel->{"phi","Subscript[\[Sigma], \[Phi]\[Phi]]^*[rho,phi]"},
PlotRange->{{-Pi,Pi},{-0.8,0.7}},
GridLines->{Range[-3.4,3.4,0.2],Range[-0.8,0.7,0.05]},
PlotLegends->{"Subscript[\[Sigma], \[Phi]\[Phi]]^*[1.0,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^*[1.2,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^*[1.4,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^*[1.6,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^*[1.8,phi]","Subscript[\[Sigma], \[Phi]\[Phi]]^*[2.0,phi]"}
],
Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.8},{0,0.7}}]}]
]
{MAX,{max}}=Maximize[SigmaPhiBegin[1.0,phi],-Pi<=phi<=Pi,phi];
Print["Maximize[SigmaPhiPhiBegin[1.0,",max,"]] = ",MAX];
{MIN,{min}}=Minimize[SigmaPhiBegin[1.0,phi],-Pi<=phi<=Pi,phi];
Print["Minimize[SigmaPhiPhiBegin[1.0,",min,"]] = ",MIN];
(*--------------------------------------------------------------------------------------------------------------------------------*)
qbegin[rho_,phi_]=D[SigmaRhoPhiBegin[rho,phi],rho]+(D[SigmaPhiBegin[rho,phi],phi]+2*SigmaRhoPhiBegin[rho,phi])/rho;
q[t_,phi_]=qbegin[b[t],phi]*D[b[t],t];
(*Print["q[t,phi] = ",q[t,phi]];*)
pbegin[rho_,phi_]=D[SigmaRhoBegin[rho,phi],rho]+(D[SigmaRhoPhiBegin[rho,phi],phi]+SigmaRhoBegin[rho,phi]-SigmaPhiBegin[rho,phi])/rho;
p[t_,phi_]=-pbegin[b[t],phi]*D[b[t],t];
(*Print["p[t,phi] = ",p[t,phi]];*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
dotsigmarhophi[t_,phi_]=q[t,phi];
(*Print["dotsigmarhophi[t,phi] = ",dotsigmarhophi[t,phi]];*)
dotsigmarhorho[t_,phi_]=-p[t,phi];
(*Print["dotsigmarhorho[t,phi] = ",dotsigmarhorho[t,phi]];*)dotsigmaphiphi[t_,phi_]=D[dotsigmarhophi[t,phi],phi]+(t*D[dotsigmarhorho[t,phi],t]+dotsigmarhorho[t,phi]);
(*Print["dotsigmaphiphi[t,phi] = ",dotsigmaphiphi[t,phi]];*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
(*------------------------------------------------------------------------------------------------------------------------------*)
Show[
Plot[{dotsigmarhophi[1,phi],dotsigmarhophi[1.2,phi],dotsigmarhophi[1.4,phi],dotsigmarhophi[1.6,phi],dotsigmarhophi[1.8,phi],dotsigmarhophi[2,phi]},{phi,-Pi,Pi},
AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][t,phi]"},
PlotRange->{{-Pi,Pi},{-0.4,0.5}},
GridLines->{Range[-3.4,3.4,0.2],Range[-0.4,0.5,0.05]},
PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Phi]][2.0,phi]"}],
Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.4},{0,0.5}}]}]
]
Show[
Plot[{dotsigmarhorho[1,phi],dotsigmarhorho[1.2,phi],dotsigmarhorho[1.4,phi],dotsigmarhorho[1.6,phi],dotsigmarhorho[1.8,phi],dotsigmarhorho[2,phi]},{phi,-Pi,Pi},
AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][t,phi]"},
PlotRange->{{-Pi,Pi},{-0.4,0.5}},
GridLines->{Range[-3.4,3.4,0.2],Range[-0.4,0.5,0.05]},
PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Rho]\[Rho]][2.0,phi]"}],
Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-0.4},{0,0.5}}]}]
]
Show[
Plot[{dotsigmaphiphi[1,phi],dotsigmaphiphi[1.2,phi],dotsigmaphiphi[1.4,phi],dotsigmaphiphi[1.6,phi],dotsigmaphiphi[1.8,phi],dotsigmaphiphi[2,phi]},{phi,-Pi,Pi},
AxesLabel->{"phi","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][t,phi]"},
PlotRange->{{-Pi,Pi},{-3,5}},
GridLines->{Range[-3.4,3.4,0.2],Range[-3,5,0.5]},
PlotLegends->{"Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.0,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.2,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.4,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.6,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][1.8,phi]","Subscript[Overscript[\[Sigma], .], \[Phi]\[Phi]][2.0,phi]"}],
Graphics[{Arrow[{{-Pi,0},{Pi,0}}],Arrow[{{0,-3},{0,5}}]}]
]
(*------------------------------------------------------------------------------------------------------------------------------*)
(*------------------------------------------------------------------------------------------------------------------------------*)
fitWithAdaptiveOrder[T_,f_]:=
Module[{func,m,data,model,vars,fit,approx,epsilon,cleanFit},
epsilon=0.01;
func[t_,phi_]:=f[t,phi];
m=3;
While[True,
data=Table[{phi,func[T,phi]},{phi,-Pi,Pi,Pi/m}];
model=a0+Sum[ak[k]*Cos[k*phi]+bk[k]*Sin[k*phi],{k,1,Ceiling[m/2]-1}];
vars=Join[{a0},Flatten[Table[{ak[k],bk[k]},{k,1,Ceiling[m/2]-1}]]];
fit=FindFit[data,model,vars,phi];
(*cleanFit=fit/.Rule[coeff_,val_]:>Rule[coeff,If[Abs[val]<10^(-10),0,val]];
approx=model/.cleanFit;*)
approx=model/.fit;
(*If[func[T,phi]!=0,*)
If[Max[Abs[Table[Abs[(approx-func[T,phi])/func[T,phi]]/. phi->x,{x,-Pi,Pi,Pi/m}]]]<epsilon,Break[]];(*,
If[Max[Abs[Table[Abs[approx-func[T,phi]/.{ phi->x}],{x,-Pi,Pi,Pi/m}]]]<epsilon,Break[]];(*Если Delta=0*)
];*)
m=m+1;
];
approx];
(*------------------------------------------------------------------------------------------------------------------------------*)
(*------------------------------------------------------------------------------------------------------------------------------*)
approxFunction1[t_,theta_]:=fitWithAdaptiveOrder[t,q]/.{phi->theta};
Time=2.0;Phi=Pi/2;
Print["approxFunction1[",Time,",pHi] = ",approxFunction1[Time,pHi]];
Print["approxFunction1[",Time,",",Phi,"] = ",approxFunction1[Time,Phi]];
Print["q[",Time,",",Phi,"] = ",approxFunction1[Time,Phi]];
(*------------------------------------------------------------------------------------------------------------------------------*)
(*------------------------------------------------------------------------------------------------------------------------------*)
timebeginRP=AbsoluteTime[];
uRP=0.4;
flagI1nRP=True;
epsilonRP=0.0002;
delta2nRP=100.;
NNRP=100;
I1nRP=Table[-100.,{i,1,NNRP}];I2nRP=Table[-100.,{i,1,NNRP}];
X1nRP=Table[-100.,{i,1,NNRP}];X2nRP=Table[-100.,{i,1,NNRP}];
Y1nRP=Table[-100.,{i,1,NNRP}];Y2nRP=Table[-100.,{i,1,NNRP}];
rho0RP=1;
rhofRP=2;
t0RP=1;
tfRP=2;
While[delta2nRP>epsilonRP,
delta2nRP=-1.;
uRP=uRP/2;
I1nRP=I2nRP;
I2nRP=Table[-100.,{i,1,NNRP}];
X1nRP=X2nRP;
Y1nRP=Y2nRP;
Do[(*For[v=1,v<=2,v=v+1,*)
If[v==2||(v==1&&flagI1nRP==True),
flagI1nRP=False;
flagRP=v==1;
dtRP=uRP/v;(*integration step*)
(*number of time segments. (+1) to take into account the tfRP time point, which we will add artificially*)
iendRP=Round[(tfRP-t0RP)/dtRP]+1;
fouriendRP=4*iendRP+1;(*number of grid division angles. (+1) to include Pi*)
spisoksigmaPSKRP=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRP}],{s,1,iendRP}],{i,1,iendRP}];
Do[(*For[i=1,i<=iendRP,i=i+1,*)(*RHO radius cycle*)
tempRP=t0RP+(i-1)*dtRP;(*current time layer*)
RhoRP=rho0RP+(i-1)*dtRP;(*current radius*)
(*at each new time layer-radius we initialize the initial value of the function*)
sigmanewValRP=SigmaRhoPhiBegin[tempRP,phi];
Do[(*For[t=tempRP,t<=tfRP-dtRP,t=t+dtRP,*)(*Time cycle T*)
sigmanewValRP=sigmanewValRP+dtRP*(fitWithAdaptiveOrder[t,dotsigmarhophi]+fitWithAdaptiveOrder[t+dtRP,dotsigmarhophi])/2/.{phi->theta};
(*Print["sigmanewValRP = ",sigmanewValRP];*)
timeRP=Round[(t-t0RP)/dtRP]+1;
Do[(*For[j=1,j<=fouriendRP,j=j+1,*)(*Cycle by angle PHI*)
thetaRP=-(Pi+(2*Pi)/(4*iendRP))+(2*Pi*j)/(4*iendRP);(*-Pi<=phi<=Pi*)
resRP=Evaluate[sigmanewValRP/.{theta->thetaRP}];
If[v==1,
spisoksigmaPSKRP[[i]][[timeRP]][[j]]={RhoRP,thetaRP,resRP};,(*filled only on the first iteration, then blocked*)
spisoksigmaPSKRP[[i]][[timeRP+1]][[j]]={RhoRP,thetaRP,resRP};(*filled in at each iteration*)
];
If[t==tfRP-dtRP&&resRP>I1nRP[[i]]&&flagRP==True,(*we are looking for the maximum value of the integral on the penultimate time layer*)
I1nRP[[i]]=resRP;
X1nRP[[i]]=RhoRP;
Y1nRP[[i]]=thetaRP;
];
If[t==tfRP-dtRP&&resRP>I2nRP[[i]]&&flagRP==False,
I2nRP[[i]]=resRP;
X2nRP[[i]]=RhoRP;
Y2nRP[[i]]=thetaRP;
];
(*Angle (theta(phi)) from -Pi to Pi*)
,{j,1,fouriendRP,1}];(*];*)
(*Cycle to the penultimate time layer, since the trapezoid method uses the current and next steps*)
,{t,tempRP,tfRP-dtRP,dtRP}];(*];*)
(*Rho radii from 1.0 to 1.9, since we don’t add anything to the first one, since (i-1)*dt*)
,{i,1,iendRP,1}];(*];*)
];
(*we calculate the integral with step h, then with step h/2 and compare the results using the Runge method, we calculate both integrals only at the 1st iteration, and then flag=False*)
,{v,1,2,1}];(*];*)
Do[(*For[z=1,z<=NNRP/2,z=z+1,*)
errorRP=Abs[I2nRP[[2*z-1]]-I1nRP[[z]]]/3;
If[delta2nRP<errorRP,
delta2nRP=errorRP;
iiRP=z;
];
,{z,1,NNRP/2,1}];(*];*)
Print["------------------------------------------------------------------------------------------------------------------------"];
Print["ii = ",iiRP,", u = ",uRP];
Print["I1n[",X1nRP[[iiRP]],",",Y1nRP[[iiRP]],"] = ",I1nRP[[iiRP]],", I2n[",X2nRP[[2*iiRP-1]],",",Y2nRP[[2*iiRP-1]],"] = ",I2nRP[[2*iiRP-1]],", delta2n = ",delta2nRP];
];
timeendRP=AbsoluteTime[];
Print["Time: ",(timeendRP-timebeginRP)/60];
Do[(*For[i=1,i<=iendRP,i=i+1,*)
RhoRP=rho0RP+(i-1)*dtRP;
Do[(*For[Time=t0RP,Time<=tfRP,Time=Time+dtRP,*)
newtimeRP=Round[(Time-t0RP)/dtRP]+1;
If[i==newtimeRP(*&&RhoRP>1.*),
Do[
thetaRP=-(Pi+(2*Pi)/(4*iendRP))+(2*Pi*j)/(4*iendRP);
resRP=SigmaRhoPhiBegin[RhoRP,thetaRP];
spisoksigmaPSKRP[[i]][[newtimeRP]][[j]]={RhoRP,thetaRP,resRP};
(*If[RhoRP>1.0,
XRP=RhoRP*Cos[thetaRP];
YRP=RhoRP*Sin[thetaRP];
spisoksigmaDSKRP[[i]][[newtimeRP]][[j]]={XRP,YRP,resRP};
];*)
,{j,1,fouriendRP,1}];
];
,{Time,t0RP,tfRP,dtRP}];(*];*)
,{i,1,iendRP,1}];(*];*)
(*------------------------------------------------------------------------------------------------------------------------------*)
(*------------------------------------------------------------------------------------------------------------------------------*)
timebeginRR=AbsoluteTime[];
uRR=0.4;
flagI1nRR=True;
epsilonRR=0.0001;
delta2nRR=100.;
NNRR=100;
I1nRR=Table[-100.,{i,1,NNRR}];I2nRR=Table[-100.,{i,1,NNRR}];
X1nRR=Table[-100.,{i,1,NNRR}];X2nRR=Table[-100.,{i,1,NNRR}];
Y1nRR=Table[-100.,{i,1,NNRR}];Y2nRR=Table[-100.,{i,1,NNRR}];
rho0RR=1;
rhofRR=2;
t0RR=1;
tfRR=2;
While[delta2nRR>epsilonRR,
delta2nRR=-1.;
uRR=uRR/2;
I1nRR=I2nRR;
I2nRR=Table[-100.,{i,1,NNRR}];
X1nRR=X2nRR;
Y1nRR=Y2nRR;
Do[(*For[v=1,v<=2,v=v+1,*)
If[v==2||(v==1&&flagI1nRR==True),
flagI1nRR=False;
flagRR=v==1;
dtRR=uRR/v;
iendRR=Round[(tfRR-t0RR)/dtRR]+1;
fouriendRR=4*iendRR+1;
(*spisoksigmaDSKRR=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRR}],{s,1,iendRR}],{i,1,iendRR}];*)
spisoksigmaPSKRR=Table[Table[Table[{0.,0.,0.},{j,1,fouriendRR}],{s,1,iendRR}],{i,1,iendRR}];
Do[(*For[i=1,i<=iendRR,i=i+1,*)
tempRR=t0RR+(i-1)*dtRR;
RhoRR=rho0RR+(i-1)*dtRR;
sigmanewValRR=SigmaRhoBegin[tempRR,phi];
Do[(*For[t=tempRR,t<=tfRR-dtRR,t=t+dtRR,*)
sigmanewValRR=sigmanewValRR+dtRR*(fitWithAdaptiveOrder[t,dotsigmarhorho]+fitWithAdaptiveOrder[t+dtRR,dotsigmarhorho])/2/.{phi->theta};
timeRR=Round[(t-t0RR)/dtRR];
Do[(*For[j=1,j<=fouriendRR,j=j+1,*)
thetaRR=Evaluate[-(Pi+(2*Pi)/(4*iendRR))+(2*Pi*j)/(4*iendRR)];(*-Pi<=Phi<=Pi*)
resRR=Evaluate[sigmanewValRR/.{theta->thetaRR}];
If[v==1,
spisoksigmaPSKRR[[i]][[timeRR+1]][[j]]={RhoRR,thetaRR,resRR};,
spisoksigmaPSKRR[[i]][[timeRR+2]][[j]]={RhoRR,thetaRR,resRR};
];
If[t==tfRR-dtRR&&resRR>I1nRR[[i]]&&flagRR==True,
I1nRR[[i]]=resRR;
X1nRR[[i]]=RhoRR;
Y1nRR[[i]]=thetaRR;
];
If[t==tfRR-dtRR&&resRR>I2nRR[[i]]&&flagRR==False,
I2nRR[[i]]=resRR;
X2nRR[[i]]=RhoRR;
Y2nRR[[i]]=thetaRR;
];
,{j,1,fouriendRR,1}];(*];*)
,{t,tempRR,tfRR-dtRR,dtRR}];(*];*)
,{i,1,iendRR,1}];(*];*)
];
,{v,1,2,1}];(*];*)
Do[(*For[z=1,z<=NNRR/2,z=z+1,*)
errorRR=Abs[I2nRR[[2*z-1]]-I1nRR[[z]]]/3;
If[delta2nRR<errorRR,
delta2nRR=errorRR;
iiRR=z;
];
,{z,1,NNRR/2,1}];(*];*)
Print["------------------------------------------------------------------------------------------------------------------------"];
Print["ii = ",iiRR,", u = ",uRR];
Print["I1n[",X1nRR[[iiRR]],",",Y1nRR[[iiRR]],"] = ",I1nRR[[iiRR]],", I2n[",X2nRR[[2*iiRR-1]],",",Y2nRR[[2*iiRR-1]],"] = ",I2nRR[[2*iiRR-1]],", delta2n = ",delta2nRR];
];
timeendRR=AbsoluteTime[];
Print["Time: ",(timeendRR-timebeginRR)/60];
Do[(*For[i=1,i<=iendRR,i=i+1,*)
RhoRR=rho0RR+(i-1)*dtRR;
Do[(*For[Time=t0RR,Time<=tfRR,Time=Time+dtRR,*)
newtimeRR=Round[(Time-t0RR)/dtRR]+1;
If[i==newtimeRR(*&&RhoRR>1.*),
Do[
thetaRR=Evaluate[-(Pi+(2*Pi)/(4*iendRR))+(2*Pi*j)/(4*iendRR)];
resRR=SigmaRhoBegin[RhoRR,thetaRR];
spisoksigmaPSKRR[[i]][[newtimeRR]][[j]]={RhoRR,thetaRR,resRR};
(*If[RhoRR>1.,
XRR=RhoRR*Cos[thetaRR];
YRR=RhoRR*Sin[thetaRR];
spisoksigmaDSKRR[[i]][[newtimeRR]][[j]]={XRR,YRR,resRR};
];*)
,{j,1,fouriendRR,1}];
];
,{Time,t0RR,tfRR,dtRR}];(*];*)
,{i,1,iendRR,1}];(*];*)
(*------------------------------------------------------------------------------------------------------------------------------*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
tableRP={};
For[j=1,j<=fouriendRP,j=j+1,
If[spisoksigmaPSKRP[[1]][[iendRP]][[j]]!={0.,0.,0.},
tableRP=Append[tableRP,spisoksigmaPSKRP[[1]][[iendRP]][[j]]];
];
];
(*--------------------------------------------------------------------------------------------------------------------------------*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
tableRR={};
For[j=1,j<=fouriendRR,j=j+1,
If[spisoksigmaPSKRR[[1]][[iendRR]][[j]]!={0.,0.,0.},
tableRR=Append[tableRR,spisoksigmaPSKRR[[1]][[iendRR]][[j]]];
];
];
(*--------------------------------------------------------------------------------------------------------------------------------*)
(*--------------------------------------------------------------------------------------------------------------------------------*)
ListLinePlot[
{tableRR,tableRP(*,tablePP[iendPP]*)}/. {a_,b_,c_}:>{b,c},
PlotStyle->Automatic,
PlotRange->{{-Pi,Pi},{-0.2,0.2}},(*{{-Pi,Pi},All},*)
AxesLabel->{"\[Phi]","\[Sigma]"},
ImageSize->Large,
GridLines->{Range[-3.2,3.2,0.2],Range[-0.2,0.2,0.02]}
]
(*--------------------------------------------------------------------------------------------------------------------------------*)

Below I attach 2 graphs. The first one is what should be obtained, the second one is what I get. enter image description here

Note: The problem is that the graphs look the same, but the resulting vertical stress values are different.

This is my first time asking a question on this forum. When I click "Reply" for some reason nothing happens, so I'm answering you by editing the original post.

Eric, I wrote a program for a general case. Now I am considering a specific model. For which the input data is as follows. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I am considering the problem of body growth. b[t]=t is the growth function. It is the outer radius, t is time. The radius and time are sort of synchronized. The first part of the code is simply formulas rewritten into code. The integration itself begins with:

uRP=0.4;
flagI1nRP=True;
epsilonRP=0.0001;
delta2nRP=100.;
NNRP=100;
...

For the shear stress RR the integration function is similar.

The lower integration limit is "t", the upper one is "b(t)", for the model under consideration 1<=t<=2.

POSTED BY: Yaroslav B

3 Replies

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Eric Rimbey

Posted 7 hours ago

I'm sorry, but I've been poking through this for like an hour and I have no idea what your code is doing. Can you minimize this example? Or can you at least pinpoint where you're actually applying the "trapezoidal method" for an integral and what variable is your "lower limit"? Are the other plots correct? If not, is it the same problem? Your final plot is based on `spisoksigmaPSKRR[[1]][[iendRR]]` and `spisoksigmaPSKRP[[1]][[iendRP]]` where `iendRR` and `iendRR` are both `41`. I'd recommend you pull out that slice of data, figure out by what factor it deviates from the expected, and then see where in your code that factor might have been changed/misapplied/whatever. Alternatively, maybe just explain what these functions are and let us help you start from the beginning. That's probably easier than reverse-engineering this wall of code. FWIW, this site isn't intended as a place for free debugging services. I probably won't spend any more time on this if you can't isolate the problem to a specific programming question. Maybe someone else has the time to spend on this.

POSTED BY: Eric Rimbey

Eric Rimbey

Posted 9 hours ago

Question: At the top you define b[t_] := t SigmaRhoBegin[rho_, phi_] = 0 SigmaRhoPhiBegin[rho_, phi_] = 0 None of these definitions for these symbols is ever updated. Elsewhere in your code you have expressions like D[b[t], t] D[SigmaRhoBegin[rho, phi], rho] D[SigmaRhoPhiBegin[rho, phi], rho] So, `D[b[t], t]` will always be `1`, `D[SigmaRhoBegin[rho, phi], rho]` will always be `0`, and `D[SigmaRhoPhiBegin[rho, phi], rho]` will always be 0. Can you explain what your intention is behind this?

POSTED BY: Eric Rimbey

Eric Rimbey

Posted 9 hours ago

Those two graphs look basically the same to me. Can you point out where the problem is? Oh, the heights are different.

POSTED BY: Eric Rimbey

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Calculation of an integral with a variable lower limit using the trapezoidal method

Note: The problem is that the graphs look the same, but the resulting vertical stress values ​​are different.

Note: The problem is that the graphs look the same, but the resulting vertical stress values are different.