A simply supported cross frame consists of eight beams that have a square section (0.125 x 0.125 meter).
A simply supported cross frame consists of eight beams that have a square section (0.125 x 0.125 meter). The frame is 10 m x 10 m. Consider modes in the XY plane only (constrain the back face against translation in the Z direction). To simulate a pinned constraint at the end of a beam element, the solid model includes a cylindrical groove at the end of each spoke (at the centerline of the cross section). A radial pin constraint is applied to the face of each groove.
Calculate 20 modes. The benchmark comparison is performed on the first 16 modes only. Calculating 20 modes improves the accuracy of the highest few modes for comparison.
The first 16 frequencies correspond to the benchmark as follows:
Natural frequencies | F1 | F2 | F3 | F4 | F5 | F6 | F7 | F8 |
NAFEMS (Beam Elements) |
11.336 Hz | 17.709 Hz | 17.709 Hz | 17.709 Hz | 17.709 Hz | 17.709 Hz | 17.709 Hz | 17.709 Hz |
Fusion (Solid Elements) |
11.33 Hz | 18.38 Hz | 18.41Hz | 18.41 Hz | 18.48 Hz | 18.48 Hz | 18.51 Hz | 18.51 Hz |
% Difference | 0.053 % | 3.79 % | 3.96 % | 3.96 % | 4.35 % | 4.35 % | 4.52 % | 4.52 % |
Natural frequencies | F9 | F10 | F11 | F12 | F13 | F14 | F15 | F16 |
NAFEMS (Beam Elements) |
45.345 Hz | 57.390 Hz | 57.390 Hz | 57.390 Hz | 57.390 Hz | 57.390 Hz | 57.390 Hz | 57.390 Hz |
Fusion (Solid Elements) |
45.91 Hz | 59.39 Hz | 59.44 Hz | 59.44 Hz | 59.46Hz | 59.46 Hz | 59.66 Hz | 59.66 Hz |
% Difference | 1.25 % | 3.48 % | 3.57 % | 3.57 % | 3.61 % | 3.61 % | 3.96 % | 3.96 % |
NAFEMS Publication Test No. FV2, The International Association for the Engineering Analysis Community, "NAFEMS Background To Benchmarks", G.A.O Davies, R.T. Fenner, R.W. Lewis, June, 1992.