The effect of the loading conditions on the stability of rotating cylindrical shells is examined experimentally. It is established that the critical loads of axially compressed rotating shells substantially decrease with increasing speed of rotation
The paper outlines a method and results of experimental determination of vibratory stresses in a shell structure contacting with a medium. The stresses peak at the junction between the shell and the branch pipe. It is established that when the shell is in contact with the medium, the vibratory stresses are much higher, while the vibratory accelerations are much lower Introduction. Papers that overview the state of the art in experimental research of the dynamics of shells of revolution were reviewed in [1-3, 7, 8, 10-16]. Plates and shells under nonstationary loads were theoretically and experimentally studied in [2,3,8,[11][12][13][14]. It follows from these reviews that the experimental determination of the stress-strain state of a shell structure in contact with a medium still claims attention. Theoretical methods are expedient to combine with experimental methods to ascertain the reliability or applicability of the former.The present paper studies the effect of an impulsive load on the natural frequencies, vibration modes, and stress-strain state of a structure consisting of a closed cylindrical shell and a branch pipe. It is also of interest to examine the influence of the ambient medium on the minimum natural frequency and stress-strain state of this structure subject to a shock load.
Resonant Frequencies and Modes.The test shell was made by winding a binder-impregnated continuous alkali-free glass filament onto a circular cylindrical mandrel (Fig. 1). The thickness of the shell and branch pipe h =0.3 cm. During winding, the tension of glass filaments was kept constant and equal to 3 N per filament. The binder was a compound consisting of ÉD-6 epoxy resin, grade A bakelite lacquer, and BF-4 adhesive. The shell hardened at a temperature of 420 K for 30 h. The set-up is schematized in Fig. 2. Shell 6 attached to massive support arms 5 with rings 7 was placed in a 60´45´45 cm box (not shown in Fig. 2) filled with sand so that the branch pipe did not contact with the sand. Arms 5 were fixed on massive plate 4. The vibrations of the shell were excited kinematically, using a VÉDS-10À electrodynamic shaker 15. The pin connecting the vibrator and the shell was attached at point 1.The frequency of forced vibrations was measured, with high accuracy, with Ch3-32 digital frequency meter 16. The amplitude of vibration was measured with contactless vibration transducer 8 and VVV-302 electronic unit 9. For transducer 8 to operate, an aluminum 1´1´0.01 cm plate was bonded to the outside surface of shell 6. The vibration transducer was mounted on a bar (not shown in Fig. 2) fixed to a massive bedplate (not shown in Fig. 2) that is vibration-isolated from shell 6 and plate 4. Figure 3 shows the frequency response of the shell in the absence (Fig. 3a) and presence (Fig. 3b) of sand. Figure 4 shows the vibration modes in the midsection 1/2L (Fig. 4a) and in the section spaced by 1/4L from the edge (Fig. 4b). An analysis of the results reveals that the amplitude of vibrations is maximum at point 2 (Fig. 2) in the section 1/2L a...
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