Beam modal analysis using ANSYS APDL

 

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In this blog, we will learn to detect the natural frequency of cantilever beam using Ansys as well as Matlab code.

Example: Obtain a natural frequency of a steel bar with a length of 0.45 m. The width and height of the beam are 0.02 m and 0.003 m. The modulus of elasticity of a steel beam is 2.1 * 10 ^ 11 N / m ^ 2. Verify this with Ansys software and Matlab code with analytical solutions.

Initial setting beam

Step1: Preferences> Structural

Step2: Preprocessor> Element Type> Add> Beam> 2 noded 188> OK

Step 3: Preprocessor> Physical Properties> Physical Model> Structural> Elastic> Isotropic> 2.1e11> Fine> Density> 7850> Fine> Close

Step4: Preprocessor> modeling> create> keypoint> active cs> key point number-1, location-0> apply >> keypoint number-2, location-0.45> ok

Step5: Preprocessor> modeling> create> line> active coordinate system> OK

Step6: Preprocessor> section> beam> common section> b = 0.02, h = 0.003> OK

Step7: Preprocessor> Meshing> Mesh Tool> Mesh 5> Element Element> OK

Step 8: Preprocessor> Load> Defined load> Structural> Select active point 1> Select all dof> OK

Finding solutions

Step9: Solutions> Analysis Type> New Analysis> Modal

Step10: Solution> Analysis Options> Number of nodes to be removed = 3> OK

Step 11: Solution> Solution> Current LS> OK

Step12: General Postprocessing> Result Summary

.Step 13: General Postprocessor> Plot Results> Distorted Shape

Step 14: General Postprocessor> Plot Results> Contour Plotting> Nodal Solution

Matlab code for cantilever beam

CLC;
den = input (‘Enter density’); % Density value
E = input (‘enter e’); % modulus of elasticity
B = input (‘enter b’); % Width
D = input (‘Enter d’); % Depth
l = input (‘Enter L’); % Length
I = BD ^ 3/12; % Inertia A = bd; % Area
f1 = sqrt ((ei) / (denAl ^ 4)); w1 = ((1.87 ^ 2) f1);
W 2 = ((4,694 ^ 2) f 1); w1 = w1 / (23.142);
W2 = w2 / (2 * 3.142);
fprintf (‘First frequency of cantilever beam =% f’, w1);
fprintf (‘Second frequency of cantilever beam =% f’, w2);
enter% b0.02
Enter% d0.003
Enter% L0.45
%
% First frequency of cantilever beam = 12.309133
% Second frequency of cantilever beam = 77.558681 >>

Result (Hz) Analytical Results (Hz) Mean result (Hz)
12.398 12.37 12.309133
77.136 77.53 77.558681

Conclusion:

The error was 0.001%.

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