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Correlation between shape errors in flat grinding
Get PDFCorrelation between shape errors of the tool and ceramic work-pieces are presented in the paper. A new tool, on which different shape errors of convexity or concavity can be set, was used during experiments. Results from flat grinding, such as the shape errors, are presented and analyzed. Computational calculations concerning the local shape errors of the tool and the technological effects such as surface roughness and waviness parameters as well as the workpiece plane-parallelism are also presented
Active synthesis of machine drive systems using a comparative method
Get PDFIn this work the method of active synthesis of mechanical systems in accordance with the desired frequency spectrum has been formulated and formalised. Active synthesis of a proportional regulation system has been performed in accordance with the method formulated and a verification of the correctness of the results has been carried out
Bond graph-based analysis of energy conversion in vibration-piezoelectricity coupling and its application to a cantilever vibra tion energy harvester
Get PDFThe energy flow in a piezoelectric vibration energy harvester (VEH) involves both the mechanical domain and the electrical domain. To better understand the vibration-piezoelectricity coupling of this device, a unified description approach based on the bond graph is proposed to analyze the influence of the piezoelectric VEH parameters on the electricity harvesting performance in the energy conversion. Both the mechanical structure and the electric circuit are modeled using the bond graph. The present method is applied to analyze the parametric configuration of a piezoelectric VEH, which is further tested on an experimental platform. The results show that the unified model using the bond-graph is well-suited for analyzing the vibration-piezoelectricity coupling. The proposed method can advance the design optimization of piezoelectric VEHs
Influence of concave groove on transmission of blasting vibration wave
Get PDFWith the extensive application of blasting techniques, the prediction and hazard control of explosion-induced vibration is an important issue which cannot be ignored in blasting engineering. A numerical approach is presented to study the explosion-induced pressure load on the surface of C-4 explosives in a semi-infinite space, in order to explore the effectiveness of concave grooves in ground vibration wave barrier. Numerical simulations are carried out by using a widely applied explicit dynamic nonlinear finite element software LS-DYNA and adopted the Arbitrary Lagrangian-Eulerian method for numerical analysis to simulate the propagation of blast waves. The analysis shows that the concave grooves have a significant effect on attenuating the propagation of detonation waves. The vibration control is related to the width and depth of the groove, and the impact of the depth is greater than that of the width. This study can be used as a reference in hazard control of explosion-induced vibration
Nonlinear vibration of rectangular plate under the parametric excitation
Get PDFIn this paper, the dynamic behavior of rectangular plate under the in-plane load is studied. The partial differential equation based on the mechanical model is established, which will be deduced into two ordinary differential equations by use of Galerkin method. The existence of 1/2 harmonic solutions of the dynamical system applying the harmonic balance method is analyzed. The amplitude-frequency relationship is found, and the stability of solutions is investigated. The stable zone of dynamical system is determined
Bridge scour evaluation based on ambient vibration
Get PDFThe vulnerability of bridges to hazards such as earthquakes, wind and floods necessitates special structural characteristics. To guarantee the stability of bridge structures, the precise evaluation of the scour depth of bridge foundation has recently become an important issue, as most of the unexpected damage to or collapse of bridges has been attributed to hydraulic issues. In this paper, a vibration-based bridge health monitoring system that utilizes only the response of superstructure to rapidly evaluate the embedded depth of a bridge column is proposed. To clarify the complex fluid-solid coupling phenomenon, the effects of embedded depth and water level were first verified through a series of static experiments. A confined finite element model simulated by soil spring effects was then established to illustrate the relationship between the fundamental frequency and the embedded depth. Using the proposed algorithm, the health of the bridge is able to be inferred by processing the ambient vibration response of the superstructure. To implement the proposed algorithm, a SHM prototype system monitoring environmental factors such as temperature, water level, and inclination was developed to support on-line processing. The performance of the proposed system was verified by a series of dynamic bridge scour experiments conducted in a laboratory flume and compared with readings from a water-proof camera. The results showed that using the proposed vibration-based bridge health monitoring system, the embedded depth of bridge column during complex scour processes is able to be reliably calculated
Investigation of vibro-acoustic properties of modern lathe collet chuck
Get PDFManufacturing industry has been attempting to attain the required cutting performance in order to achieve high precision, fast productivity and lower maintenance costs. Vibrations generated during machining can be a serious problem degrading component quality, precision, tool service life, lathe performance and cutting rates. This paper is concerned with analysis of cutting process by using modal testing. Static and dynamic deformations of lathe collet chuck have a significant impact on cutting process stability, which affects workpiece quality and production output. Modal analysis was applied to develop a mathematical model of chucks dynamics, which consist of a number of mode shapes each with natural frequency and modal damping. Modal analysis and experimental measurements were performed on a collet chuck of CNC lathe installed in metal working company UAB “Stevila”
Investigation of straw layer movement over the walker surface
Get PDFStraw layer movement over the walker surface has been examined by measuring characteristics of elasticity and viscosity of the straw layer. For this purpose a visco-elastic model has been introduced. The examined process is represented by two stages: the first one is associated with the elastic deformation of the straw while the walker section moves upwards, and the straw layer laying on its surface is subjected to compression. Whereas the second stage involves a free throw of straw after the takeoff from the walker surface, and after the free throw, their contact onto the walker surface. The method of successive steps was used for the analysis of the movement process. The proposed model can be applied for modeling complex nonlinear characteristics of the straw layer movement by employing linear elastic and viscous elements through selection of their equivalent coefficients. Measurement of the elastic and viscous characteristics of the straw layer by their equivalent coefficients enabled to calculate rational rotation angles of the walker crankshaft at the takeoff ωt1 of the layer from the walker surface and contact ωt3 to the surface provided that during each period of crankshaft rotation a straw layer undergoes an impact. It was determined that straw movement is mainly dependent on the thickness, moisture content and viscosity of the straw layer. The takeoff of the thicker straw layer from the walker surface is delayed, since after the impact duration of its deformation is longer, resulting in a shorter time of free throw. Wet straw layer is less elastic, resulting in its longer movement jointly with the walker section, and the height of the free throw is smaller resulting in less favorable conditions for grain penetration when compared to the dry straw
Bearings coefficients effects on chaotic and bifurcation behavior of flexible rotor systems subjected to rub-impact
Get PDFThis study investigates the influence of end-support conditions on the chaotic and bifurcation behavior of a rotating flexible shaft-disk system. The system is modeled as a continuous shaft with a rigid disk in its mid span whilst supported by multi-coefficients bearings. Both Coriolis and centrifugal effects due to shaft flexibility are included. The partial differential equations of motion are extracted using the Rayleigh beam theory and the assumed mode method is used to discretize them in order to be solved numerically. The analytical tools used in this work include time series, phase plane portrait, power spectrum, Poincaré map, bifurcation diagrams, and Lyapunov exponents. The main objective of the present study is to investigate the effects of end-supports stiffness and damping coefficients on the chaotic vibration behavior of a rotating system. Periodic, sub-harmonic, quasi-periodic, and chaotic states have been observed for each case. As demonstrated, inclusion of the bearing effects can primarily change the speed ratios at which rub-impact occurs. The principal and cross-coupling stiffness and damping coefficients have quite different effects in the chaotic behavior of the system
Numerical simulation research of vortex-induced vibrations of the long circular cylinders with high mass-ratio
Get PDFThe two-degrees-of-freedom vortex-induced vibrations (VIV) of the long circular cylinders with high mass-ratio are numerically simulated with the software ANSYS/CFX. The VIV characteristic of the cylinder is analyzed in the different conditions (Ur = 3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion is different from the vortex-induced vibrations of the cylinder with low mass-ratio. When Ur is 3, the frequency of the drag force on the cylinder is twice of that of the lift force and the in-line VIV frequency of the cylinder is twice of that of the cross-flow VIV. The in-line VIV amplitude of the cylinder is much smaller than the cross-flow VIV amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main in-line VIV frequency of the cylinder is mainly the same as that of the cross-flow VIV and the secondary in-line VIV frequency is equal to the frequency of the drag force. The in-line VIV amplitude is still very small compared with the cross-flow VIV amplitude. When Ur is up to 8 and 10, the in-line VIV frequency of the cylinder is the same as the main frequency of the cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of the drag force or lift force. But the secondary cross-flow VIV frequency of the cylinder is equal to the frequency of the lift force. The amplitude ratio between in-line VIV and cross-flow VIV is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval