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evaluatePrincipalStress

Evaluate principal stress at nodal locations

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Syntax

pStress = evaluatePrincipalStress(structuralresults)

Description

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pStress = evaluatePrincipalStress(structuralresults) evaluates principal stress at nodal locations using stress values from structuralresults. For transient and frequency response structural models, evaluatePrincipalStress evaluates principal stress for all time- and frequency-steps, respectively.

Examples

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Open Live Script

Solve a static structural model representing a bimetallic cable under tension, and compute octahedral shear stress.

Create a structural model.

structuralmodel = createpde("structural","static-solid");

Create a geometry and include it in the model. Plot the geometry.

gm = multicylinder([0.01,0.015],0.05);
structuralmodel.Geometry = gm;
pdegplot(structuralmodel,"FaceLabels","on", ...
                         "CellLabels","on", ...
                         "FaceAlpha",0.5)

Figure contains an axes object. The axes object contains 3 objects of type quiver, patch, line.

Specify Young's modulus and Poisson's ratio for each metal.

structuralProperties(structuralmodel,"Cell",1,"YoungsModulus",110E9, ...
                                              "PoissonsRatio",0.28);
structuralProperties(structuralmodel,"Cell",2,"YoungsModulus",210E9, ...
                                              "PoissonsRatio",0.3);

Specify that faces 1 and 4 are fixed boundaries.

structuralBC(structuralmodel,"Face",[1,4],"Constraint","fixed");

Specify the surface traction for faces 2 and 5.

structuralBoundaryLoad(structuralmodel,"Face",[2,5], ...
                                       "SurfaceTraction",[0;0;100]);

Generate a mesh and solve the problem.

generateMesh(structuralmodel);
structuralresults = solve(structuralmodel)
structuralresults = 
  StaticStructuralResults with properties:

      Displacement: [1x1 FEStruct]
            Strain: [1x1 FEStruct]
            Stress: [1x1 FEStruct]
    VonMisesStress: [22402x1 double]
              Mesh: [1x1 FEMesh]

Evaluate the principal stress at nodal locations.

pStress = evaluatePrincipalStress(structuralresults);

Use the principal stress to evaluate the first and second invariant of stress.

I1 = pStress.s1 + pStress.s2 + pStress.s3;
I2 = pStress.s1.*pStress.s2 + ...
     pStress.s2.*pStress.s3 + ...
     pStress.s3.*pStress.s1;
tauOct = sqrt(2*(I1.^2 -3*I2))/3;
pdeplot3D(structuralmodel,"ColorMapData",tauOct)

Open Live Script

Evaluate the principal stress and octahedral shear stress in a beam under a harmonic excitation.

Create a transient dynamic model for a 3-D problem.

structuralmodel = createpde("structural","transient-solid");

Create the geometry and include it in the model. Plot the geometry.

gm = multicuboid(0.06,0.005,0.01);
structuralmodel.Geometry = gm;
pdegplot(structuralmodel,"FaceLabels","on","FaceAlpha",0.5)
view(50,20)

Figure contains an axes object. The axes object contains 3 objects of type quiver, patch, line.

Specify Young's modulus, Poisson's ratio, and the mass density of the material.

structuralProperties(structuralmodel,"YoungsModulus",210E9, ...
                                     "PoissonsRatio",0.3, ...
                                     "MassDensity",7800);

Fix one end of the beam.

structuralBC(structuralmodel,"Face",5,"Constraint","fixed");

Apply a sinusoidal displacement along the y-direction on the end opposite the fixed end of the beam.

structuralBC(structuralmodel,"Face",3,...
                             "YDisplacement",1E-4,...
                             "Frequency",50);

Generate a mesh.

generateMesh(structuralmodel,"Hmax",0.01);

Specify the zero initial displacement and velocity.

structuralIC(structuralmodel,"Displacement",[0;0;0],"Velocity",[0;0;0]);

Solve the model.

tlist = 0:0.002:0.2;
structuralresults = solve(structuralmodel,tlist);

Evaluate the principal stress in the beam.

pStress = evaluatePrincipalStress(structuralresults);

Use the principal stress to evaluate the first and second invariants.

I1 = pStress.s1 + pStress.s2 + pStress.s3;
I2 = pStress.s1.*pStress.s2 + ...
     pStress.s2.*pStress.s3 + ...
     pStress.s3.*pStress.s1;

Use the stress invariants to compute the octahedral shear stress.

tauOct = sqrt(2*(I1.^2 -3*I2))/3;

Plot the results.

figure
pdeplot3D(structuralmodel,"ColorMapData",tauOct(:,end))

Input Arguments

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Solution of the structural analysis problem, specified as a StaticStructuralResults, TransientStructuralResults, or FrequencyStructuralResults object. Create structuralresults by using the solve function.

Example: structuralresults = solve(structuralmodel)

Output Arguments

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Principal stress at the nodal locations, returned as a structure array.

Version History

Introduced in R2017b

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See Also

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