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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 Dplaced on points B and C fixed in all DOFfixed 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: 8000Young's Modulus: 2e11 Poisson's Ratio: 0.3
 Constraints: Location: Degrees of Freedom: Placed on point APlaced on point B : Fixed in TransX, TransY, TransZ and Rotation RxFixed 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: 8000Young'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 RotZfixed 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