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Dynamic Frequency Response Analysis Problem
This chapter contains dynamic frequency response analysie problem and Structure's results. In a dynamic frequency response analysis, Structure calculates the amplitude and phase of displacements, velocities, accelerations, and stresses in your model in response to a load oscillating at different frequencies. Structure also automatically calculates all predefined measures. This list of measures differs based on the analysis type.
mvsf001: Harmonic Response of a Two-Mass Spring System
mvsf002: Deep Simply Supported Beam Harmonic Force Vibration Response
mvsf003:Deep Simply Supported Thin Square Harmonic Force Vibration Response
mvsf001: Harmonic Response of a Two-Mass Spring System
Analysis Type:
Dynamic Frequency
Model Type:
3D
Comparison:
ANSYS No. 90
Reference:
Thomson, W. T. Vibration Theory and Applications. Prentice-Hall, Inc., Englewood Cliffs, N. J., 2nd Printing, 1965.
Description:
Determine the response of the two-mass-spring system when excited by a harmonic force acting on mass at point B.
Specifications
Element Type:
mass (2), spring (3)
Units:
IPS
Dimensions:
spring length: 1 (arbitrary)
Mass Properties:
M: 0.5
Mxx: 0
Mxy: 0
Mxz: 0
Myy: 0
Myz: 0
Mzz: 0
Spring Properties: (extensional stiffness)
Kxx: 200
Kxy: 0
Kxz: 0
Kyy: 0
Kyz: 0
Kzz: 0
Constraints:
Location:
Degrees of Freedom:
constraint1
placed on points A and D
placed on points B and C
fixed in all DOF
fixed in all DOF except TransX
Loads:
Location/Magnitude:
Distribution:
Spatial Variation:
load1
placed on point B: FX = 200
N/A
N/A
Comparison of Results Data
Loc
Theory
ANSYS
Structure1
% Diff
Frequency = 1.5 Hz Disp/phase at B, C (m=dispx_2, 3/ phase_2, 3)
point B
0.8227/0
0.8227/0
0.8227/0
0%
point C
0.4627/0
0.4627/0
0.4627/0
0%
Frequency = 4.0 Hz Disp/phase at A, B (m=dispx_2, 3/ phase_2, 3)
point B
0.5115/ 180
0.5115/ 180
0.5115/180
0%
point C
1.2153/ 180
1.2153/ 180
1.215/180
0%
Frequency = 6.5Hz Disp/phase at A, B (m=dispx_2, 3/ phase_2, 3)
point B
0.5851/ 180
0.5851/ 180
0.5851/180
0%
point C
0.2697/0
0.2697/0
0.2697/0
0%
Convergence %: 0% on Frequency & Local Disp
Max P: 1
No. Equations: 2
1 You cannot view the results information in the summary file. To view the results, you must define a measure result window and view the graph.
mvsf002: Deep Simply Supported Beam Harmonic Force Vibration Response
Analysis Type:
Dynamic Frequency
Model Type:
Beam
Comparison:
NAFEMS Benchmark
Reference:
Selected Benchmarks for Forced Vibration, Report No. E1261/R002 Issue 03.2/9 February 1989 , pp. 17. Test 5H
Description:
Determine response of simple supported square section beam when excited by Harmonic force uniformly distributed over beam.
Specifications
Element Type:
Square Beam
Units:
MKS
Dimensions:
L: 10.0, a =2
Material Properties:
Mass Density: 8000
Young's Modulus: 2e11
Poisson's Ratio: 0.3
Constraints:
Location:
Degrees of Freedom:
Placed on point A
Placed on point B :
Fixed in TransX, TransY, TransZ and Rotation Rx
Fixed in TransY and TransZ
Loads
Details
Force Fy = 1e6 N/m, damping = 2 % in all 16 modes used, frequency range 0 to 60 Hz
Comparison of Results Data
NAFEMS
Structure
% Diff
Peak Displacement at mid-span (mm))
13.45
13.5129
0.467
Frequency (Hz)
42.65
42.6002
0.116
mvsf003:Deep Simply Supported Thin Square Harmonic Force Vibration Response
Analysis Type:
Dynamic Frequency
Model Type:
3D
Comparison:
NAFEMS Benchmark
Reference:
Selected Benchmarks for Forced Vibration, Report No. E1261/R002 Issue 03./ 9 th February 1989, pp 23. Test 13H
Description:
Determine response of simple supported thin square plate when excited by Harmonic force uniformly distributed over plate.
Specifications
Element Type:
Shell
Units:
MKS
Dimensions:
L: 10.0, thickness: 0.05
Material Properties:
Mass Density: 8000
Young's Modulus: 2e11
Poisson's Ratio: 0.3
Constraints:
Location:
Degrees of Freedom:
Placed on edges AD and BC :
Placed on edges AB and DC :
fixed in TransY, TransZ , RotX, and RotZ
fixed in TransX, TransZ , RotY, and RotZ
Loads
Details
Force Fy = 100 Pa , damping = 2 % in all 16 modes used, frequency range 0 to 4.16 Hz
Comparison of Results Data
NAFEMS
Structure
% Diff
Peak Displacement at centre of plate (mm)
45.42
45.4466
0.0585
Frequency (Hz)
2.377
2.37603
0.0408