evaluateReaction

Evaluate reaction forces on boundary

Syntax

F = evaluateReaction(structuralresults,RegionType,RegionID)

Description

F = evaluateReaction(structuralresults,RegionType,RegionID) evaluates reaction forces on the boundary specified by RegionType and RegionID. The function uses the global Cartesian coordinate system. For transient and frequency response structural models, evaluateReaction evaluates reaction forces for all time- and frequency-steps, respectively.

Examples

Reaction Forces on Restrained End of Prismatic Bar

Create a static structural model.

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

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

structuralmodel.Geometry = multicuboid(0.01,0.01,0.05);
pdegplot(structuralmodel,"FaceLabels","on","FaceAlpha",0.5);

Specify Young's modulus and Poisson's ratio.

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

Fix one end of the bar and apply pressure to the opposite end.

structuralBC(structuralmodel,"Face",1,"Constraint","fixed")

ans = 
  StructuralBC with properties:

                RegionType: 'Face'
                  RegionID: 1
                Vectorized: 'off'

   Boundary Constraints and Enforced Displacements
              Displacement: []
             XDisplacement: []
             YDisplacement: []
             ZDisplacement: []
                Constraint: "fixed"
                    Radius: []
                 Reference: []
                     Label: []

   Boundary Loads
                     Force: []
           SurfaceTraction: []
                  Pressure: []
    TranslationalStiffness: []
                     Label: []

structuralBoundaryLoad(structuralmodel,"Face",2,"Pressure",100)

ans = 
  StructuralBC with properties:

                RegionType: 'Face'
                  RegionID: 2
                Vectorized: 'off'

   Boundary Constraints and Enforced Displacements
              Displacement: []
             XDisplacement: []
             YDisplacement: []
             ZDisplacement: []
                Constraint: []
                    Radius: []
                 Reference: []
                     Label: []

   Boundary Loads
                     Force: []
           SurfaceTraction: []
                  Pressure: 100
    TranslationalStiffness: []
                     Label: []

Generate a mesh and solve the problem.

generateMesh(structuralmodel,"Hmax",0.003);
structuralresults = solve(structuralmodel);

Compute the reaction forces on the fixed end.

reaction = evaluateReaction(structuralresults,"Face",1)

reaction = struct with fields:
    Fx: 1.2830e-05
    Fy: 1.9739e-05
    Fz: 0.0104

Reaction Forces for 3-D Structural Dynamic Problem

Evaluate the reaction forces at the fixed end of a beam subject to harmonic excitation.

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

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

Create a 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)

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);

Compute the reaction forces on the fixed end.

reaction = evaluateReaction(structuralresults,"Face",5)

reaction = struct with fields:
    Fx: [101x1 double]
    Fy: [101x1 double]
    Fz: [101x1 double]

Input Arguments

structuralresults — Solution of structural analysis problem

StaticStructuralResults object | TransientStructuralResults object | FrequencyStructuralResults object

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)

RegionType — Geometric region type

"Edge" for a 2-D model | "Face" for a 3-D model

Geometric region type, specified as "Edge" for a 2-D model or "Face" for a 3-D model.

Example: evaluateReaction(structuralresults,"Face",2)

Data Types: char | string

RegionID — Geometric region ID

vector of positive integers

Geometric region ID, specified as a vector of positive integers. Find the region IDs by using pdegplot.

Example: evaluateReaction(structuralresults,"Face",2)

Data Types: double

Output Arguments

F — Reaction forces

structure array

Reaction forces, returned as a structure array. The array fields represent the integrated reaction forces and surface traction vector, which are computed by using the state of stress on the boundary and the outward normal.

Version History

Introduced in R2017b

R2019b: Support for frequency response structural problems

For frequency response structural models, evaluateReaction evaluates reaction forces for all frequency-steps.

R2018a: Support for transient structural problems

For transient structural models, evaluateReaction evaluates reaction forces for all time-steps.