Pin-ended Double Cross

NAFEMS Benchmark, Test No. FV2:

$image\fv2.gif$

Summary

Test No. FV2 is a pin-ended double cross, in-plane vibration problem. OptiStruct is used to investigate the coupling between flexural and extensional behavior, as well as the repeated and closed eigenvalues of the double cross in normal modes analysis.

Benchmark Model

2-node simple beam elements are used to model the double cross. Each arm of the cross consists of 4 elements. The x- and y-translation displacements are fixed at the end of all arms. The material properties for the cross beams are: $image\e=200p=800.gif$ .

Modal Analysis Results

The frequency of each targeted mode is normalized with the closed form solution.

f* = closed form solution

Mode 1		Modes 2 & 3		Modes 4, 5, 6, 7 & 8
$image\fv2a.gif$		$image\fv2b.gif$		$image\fv2c.gif$
f* CBAR	11.336 Hz 0.9984	f* CBAR	17.709 Hz 0.9958	f* CBAR	17.709 Hz 0.9974

Mode 9		Modes 10 & 11		Modes 12, 13, 14, 15 & 16
$image\fv2d.gif$		$image\fv2e.gif$		$image\fv2f.gif$
f* CBAR	45.345 Hz 1.0000	f* CBAR	57.390 Hz 0.9944	f* CBAR	57.390 Hz 0.9999

Reference

NAFEMS Ltd, The Standard NAFEMS BENCHMARKS TNSB Rev. 3, NAFEMS Ltd, Scottish Enterprise Technology Park, Whitworth Building, East Kilbride, Glasgow, United Kingdom, 1990.

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