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The paper reports on the results from an experimental study of the nonlinear deformation of the elastic bottom of and the free liquid surface in a rigid shell. The shell and liquid interact with each other and with a cluster of gas bubbles produced by vibrational excitation Keywords: gas-liquid medium, cylindrical shell, elastic bottom, cluster of bubbles, vibrations Introduction. The deformation modes of elastic shells with rigid bottom filled with a liquid were experimentally and theoretically investigated in [4, 5, 10-12, etc.]. These are conjugate flexural modes excited by a vibrational load and involved in nonlinear interaction. The same publications studied the dynamic interaction between a liquid-filled elastic cylinder and an oscillating sphere. It is indicated in [2,8] that the nonlinear interaction of vibration modes of the shell and liquid is especially complicated when the amplitude of vibration of the shell wall is of the order (and more) of its thickness. When one of several cylindrical shells filled with a liquid and placed on a common elastic foundation is subjected to a vibrational load, vibrations of the other shells are parametrically excited because of their interaction [15]. The nonlinear deformation of elastic shells and free liquid surface and the chaotic motion of the gas-liquid medium, which are because of the interaction between gas bubble clusters (i.e., a liquid-gas nonlinear vibrating system) and the excited vibration modes and the source of excitation, were experimentally investigated in [5,6,8,13,14]. It is established that these processes occur at resonance.The present paper reports on results from an experimental investigation into specific nonlinear deformation of the elastic bottom of and the free liquid surface in a rigid shell that interact with each other and with clusters of gas bubbles in the vibrating liquid. We will discuss the main mechanisms of formation and the dynamic behavior of gas bubbles and their clusters and the chaotic motion of the gas-liquid medium due to the intensive vibrations of the elastic bottom.1. Model, Experimental Equipment, and Technique. The shell was modeled by an organic-glass cylindrical vessel with height H sh = 500 mm, diameter D sh = 150 mm, and wall thickness d sh = 5 mm. Precisely this thickness was chosen to prevent the parametric vibrations of the lateral surface in the frequency range involved. According to [3,5,8], such high-frequency vibrations may cause various kinds of low-frequency large-amplitude motions of the free liquid surface and motions of the gas-liquid medium. The bottom of the shell is an elastic circular plate of thickness d bt = 0.5 mm made of steel. It is rigidly fastened to the shell along the boundary with fit rings and bolts. A VÉDS-100 electrodynamic shaker was used as a source of mechanical vibrations. The vibration accelerations of the shaker table and the end and elastic bottom of the shell were measured with an IS-318 accelerometer and a D-14 vibration transducer (which are coupled with the measuring unit of th...

We discuss test data on the nonlinear dynamic deformation of the elastic wall of a cylindrical glassfiber-reinforced shell (empty or filled) subject to radial two-frequency excitation. It is revealed that such processes can be accompanied (especially at the lowest resonant frequencies) by the cyclic variation in the amplitude and deformation mode between traveling and standing circumferential wave Introduction. An important task of solid mechanics is to study the nonlinear vibrations (with large (of the order of the thickness) deflections) of thin-walled shells made of laminated composites among which glass-reinforced plastics are most popular [16]. Many publications [1-3, 5-9, 11-16, etc.] address the deformation of shell structures and nonlinear and resonant phenomena caused by the superimposed and nonlinearly interacting flexural vibration modes, which create preconditions for the occurrence of complex deformation modes (such as traveling circumferential waves, chaotic processes, etc. under single-frequency excitation). When in service, however, real shell structures used in aircraft and rocket technology, space transportation systems, chemical engineering etc., are subjected to combined vibratory loading. In this connection, some tests were performed to study the dynamic behavior of shells filled with a fluid and subjected to longitudinal-and-transverse and compound two-frequency vibrational excitation [4,10,17,18].Here we will discuss test data on the nonlinear dynamic deformation of the elastic wall of a glassfiber-reinforced plastic shell (empty or filled) subjected to two-frequency vibrational excitation. Our primary task is to find the combination of the two excitation frequencies and the natural frequencies of the "dry" and filled shells and the amplitude of the vibrational load that cause the most intensive deformation of the shell wall and to analyze the associated processes and the effect of the filler on them.1. Test Specimen, Equipment, and Procedure. The test specimen was an elastic glassfiber-reinforced plastic cylindrical sandwich shell with length N sh = 900 mm, inside diameter D sh = 320 mm, and wall thickness d sh = 0.68 mm. The shell was fixed vertically, with its lower end inserted into the ring groove filled with epoxy resin in a disk and the upper end free. The disk was fixed to a foundation. A VEDS-100 electrodynamic shaker was used to excite transverse vibrations of the shell. The shaker table was in elastic contact with the lateral surface of the shell at a point located at 0.3N sh from the lower end. To produce two-frequency vibrational excitation, we used a generator built in the frame of the shaker and an external Robotron generator (one of them was used for single-frequency excitation). The vibroaccelerations of the shaker table and the shell wall were measured with IS-318 and D-14 transducers operating with the measuring unit of the shaker and an AD-1 microtransducer (with a mass of about 1 g) with a VShV-3 device. The signals (amplitudes, frequencies) from the transducers were a...