# ContourPlot3D a (non-straight) line

I have a function axialforce[a,b,c] and a function momentY[a,b,c].

I want to see the line in 3d (a,b,c) space where axialforce[a,b,c]==-0.5 AND momentY[a,b,c]==0.

I tried both

ContourPlot3D[Ms[a, b, c] == 0 && Ns[a, b, c] == -0.5, {a, -200, 200}, {b, -200, 200}, {c, -50, 50}]

ContourPlot3D[Ms[a, b, c]^2+(Ns[a, b, c] + 0.5)^2 == 0, {a, -200, 200}, {b, -200, 200}, {c, -50, 50}]


without any output on screen (A silent NOTHING). Am I do something wrong?

The complete code is following:

ClearAll["Global*"]
ε[y_,z_,a_,b_,c_]:=-a y+b z+c
σ[ε_]:=\[Piecewise] 0   ε<-εu\[Or]εu<ε
-fy -εu<=ε<-εy
fy/εy ε -εy<=ε<=εy
fy  εy<ε<=εu

MRd[a_,b_,c_]:=-\!$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]y\ σ[ε[y, z, a, b, c]] \[DifferentialD]y \[DifferentialD]z\)\)
Ms[a_,b_,c_]:=-\!$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]z\ σ[ε[y, z, a, b, c]] \[DifferentialD]y \[DifferentialD]z\)\)
Ns[a_,b_,c_]:=-\!$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]$$\*SubsuperscriptBox[\(\[Integral]$$, $$\(-1$$/4\), $$1/4$$]σ[ε[y, z, a, b, c]] \[DifferentialD]y \[DifferentialD]z\)\)
εy=2;fy=235;εu=20;
ContourPlot3D[Ms[a,b,c]==0\[And]Ns[a,b,c]==-0.5,{a,-200,200},{b,-200,200},{c,-50,50}]
$$$$

• Have you seen this already? Jul 26 at 21:21