Abstract
Molding processes are among the most important in the manufacture of reinforced concrete structures. Vibration and shock-vibration technologies for concrete mixtures compaction and concrete products molding have the greatest distribution in the construction industry. Therefore, the issues of optimizing vibration modes, correct choice of vibration equipment do not lose their relevance. The article discusses the dynamical behavior of a shock-vibrational low-frequency resonant machine. Its mathematical model corresponds to a two-body 2-DOF vibro-impact system with a soft impact, which is simulated by a nonlinear interactive contact force in accordance with Hertz’s quasi-static contact theory. Changing the control parameters can, on the one hand, improve the compaction process, but, on the other hand, lead to unwanted vibrational modes. The article discusses such control parameters as the exciting frequency, the technological mass of the mold with concrete, and the stiffness parameters of elastic elements. Decreasing the exciting frequency, the mold mass, the vibro-isolating spring stiffness and increasing the Young’s modulus of elasticity of the rubber gasket provide an increase in impact acceleration, which improves the compaction process. However, with such changes in the parameters, coexisting regimes arise, many of which are undesirable. These are modes with a large periodicity and several impacts per cycle, chaotic modes, and transient chaos. The regime diagnostics is performed by traditional numerical means, namely, by constructing time series, phase trajectories, Poincaré maps, Fourier spectra, and the largest Lyapunov exponent. We hope that this analysis can help avoid unwanted platform-vibrator behaviour during design and operation. The presentation is accompanied by many graphs and a table.
Highlights
Molding processes are among the most important in the manufacture of reinforced concrete structures
The model exhibits coexisting regimes with different initial conditions when the control parameter is varied. This phenomenon is observed with different control parameters, namely, exciting frequency, technological mass, and stiffness parameters of vibro-isolating spring and rubber gasket
The parameters y1 and y2 represent the coordinates of these centers for the lower body and the upper body respectively in the selected coordinate system
Summary
Molding processes are among the most important in the manufacture of reinforced concrete structures. The mold with concrete is the upper body, the platform table with an attached rubber gasket is the lower body. The model exhibits coexisting regimes with different initial conditions when the control parameter is varied This phenomenon is observed with different control parameters, namely, exciting frequency, technological mass, and stiffness parameters of vibro-isolating spring and rubber gasket. The platform table is equipped with limiters that prevent the mold from sliding and rotating; the movement is only vertical For volumetric compaction, this machine uses vertically directed mold vibrations. The parameters y1 and y2 represent the coordinates of these centers for the lower body (a platform table) and the upper body (a mold with concrete) respectively in the selected coordinate system. Damping ratio of dashpot in spring 1 Damping ratio of dashpot in gasket 0 Damping ratio in concrete mixture 2 Elastic modulus of mold 2 , N m 2 Elastic modulus of gasket 1 , N m 2
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