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TEST CASE 2.1 NATURAL FREQUENCIES OF FREE SQUARE PLATE

Reference:

M.V. Barton, “Vibration of rectangular and skew cantilever plates”, Journal of Applied Mechanics, vol. 18, 1951, p. 129 – 134.

 

Problem description:

Determine the natural frequencies of a restraint-free square plate.

 

Problem sketch:

Type of created problem:

Flat plate or grillage (Z, UX, UY).

 

Geometric characteristics:

a = 1 m; t = 0.01 m.

 

Material properties:

Elastic modulus: E = 2.1·1011 Pa;

Poisson’s ratio: μ = 0.3;

Density: γ = 7800 kg/m3.

 

Boundary conditions:

Elastic links of low stiffness in all nodes of the calculation scheme: RZ = 0.001 N/m.

 

Loads:

Dead load.

 

Model description:

The system is modeled using 400 finite elements of thin plate (FE type is 19). To solve the problem, a modal analysis was performed.

 

Calculation results:

Form №

Frequency, Hz

Deviation, %

Analytical solution

LIRA 10

4

33.7119

33.6624

0.15

5

49.4558

48.9696

0.98

6

61.0513

60.6587

0.64

7

87.5160

86.9481

0.65

8

87.5160

86.9481

0.65