Dynamics Modeling of Cavitation Bubble in the Grinding Area of Power Ultrasonic Honing

2013 ◽  
Vol 797 ◽  
pp. 108-111 ◽  
Author(s):  
Xi Jing Zhu ◽  
Ce Guo ◽  
Jian Qing Wang ◽  
Guo Dong Liu
Keyword(s):  
Dynamic Characteristics ◽  
Cavitation Bubble ◽  
Velocity Potential ◽  
Superposition Principle ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Cavitation Bubbles ◽  
Power Ultrasonic ◽  
Cutting Chatter ◽  
Order Of Magnitude

t can particularly generate abundant cavitation bubbles in the processing of the power ultrasonic honing. The dynamics of cavitation bubbles in the grinding area are very vital to study the machining mechanism and the cutting chatter of power ultrasonic honing. Based on the Rayleigh-Plesset equation, a new dynamics model of cavitation bubble is established, considering the velocity of ultrasonic honing and honing pressure. With the superposition principle of velocity potential, the dynamics of double cavitation bubble is also established. Moreover, the dynamic characteristics of cavitation bubble also can be simulated numerically. The results show that cavitation bubble in the grinding zone begins to grow extensively and then undergoes collapse, and even subsequent rebound and then. The variation trend of radius change of double cavitation bubble in the grinding area is more than that of single cavitation bubble by an order of magnitude.

The Pressure Field Radiated by Cavitation Bubble in the Grinding Area of Power Ultrasonic Honing

2014 ◽  
Vol 1027 ◽  
pp. 44-47 ◽  
Author(s):  
Xi Jing Zhu ◽  
Ce Guo ◽  
Jian Qing Wang
Keyword(s):  
Radiation Pressure ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Pressure Field ◽  
Bubble Radius ◽  
Ultrasonic Frequency ◽  
Power Ultrasonic ◽  
Cutting Chatter ◽  
Grinding Mechanism ◽  
Order Of Magnitude

The pressure field induced by cavitaion bubble is responsible for the grinding mechanism and the cutting chatter of power ultrasonic honing. Based on the cavitation bubble dynamics model in the grinding area of power ultrasonic honing, the radiation pressure field of cavitation bubble was established. Experimental results show that the bubble is distributed in the grinding area like honeycomb and the size is about 10μm. Numerical simulation of dynamics and pressure field of cavitation bubble was performed. Numerical results show the dynamic behavior of cavitation bubble presents grow, expend and collapse under an acoustic cycle. However the expansion amplitude of bubble can be decreased and the collapse time can be extended and even collapse after several acoustic cycles with increasing ambient bubble radius. The bubble radiation pressure during collapsing bubble increases with increasing ultrasonic amplitude and ultrasonic frequency. And the pressure value of collapsing bubble is about 10Mpa which is more an order of magnitude than atmospheric pressure.

scholarly journals Multi-Field Coupling Dynamics Modeling of Aerostatic Spindle

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 251
Author(s):  
Guoda Chen ◽  
Yijie Chen
Keyword(s):  
Dynamic Characteristics ◽  
Low Cost ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Restoring Force ◽  
Field Coupling ◽  
Spindle Shaft ◽  
Coupling Dynamics ◽  
Air Film ◽  
Aerostatic Spindle

The aerostatic spindle in the ultra-precision machine tool shows the complex multi-field coupling dynamics behavior under working condition. The numerical investigation helps to better understand the dynamic characteristics of the aerostatic spindle and improve its structure and performance with low cost. A multi-field coupling 5-DOF dynamics model for the aerostatic spindle is proposed in this paper, which considers the interaction between the air film, spindle shaft and the motor. The restoring force method is employed to deal with the times varying air film force, the transient Reynolds equation of the aerostatic journal bearing and the aerostatic thrust bearing is solved using ADI method and Thomas method. The transient air film pressure of aerostatic bearings is obtained which clearly presents the influence induced by the tilt motion of the spindle shaft. The motion trajectory of the spindle shaft is obtained which shows different stability of the shaft under different external forces. The dynamics model shows good performance on simulating the multi-field coupling behavior of the aerostatic spindle under external force. which is quite meaningful and useful for the further research on the dynamic characteristics of the aerostatic spindle.

Kinetics of Cavitation Bubble in Ultrasonic Degassing of Casting Aluminium Alloy

2017 ◽  
Vol 896 ◽  
pp. 175-181
Author(s):  
Miao Liu ◽  
Peng Zhai ◽  
Qiang Long ◽  
Chun Yang Wang ◽  
Bo Han Xiao
Keyword(s):  
Aluminium Alloy ◽  
Cavitation Bubble ◽  
Previous Experiment ◽  
Low Frequency ◽  
Silicon Alloy ◽  
Cavitation Bubbles ◽  
Low Frequency Vibration ◽  
Calculation Results ◽  
Coefficient Of Viscosity ◽  
Kinetics Of

Severe regassing was detected by previous experiment on degassing method for aluminium-silicon alloy by injecting argon with rotation. In order to further degas, ultrasonic degassing was adopted. To describe the cavitation bubbles’ movement, traditional Rayleigh-Plesset equation was modified. Classic Rayleigh-Plesset equation is strongly restricted by the applicable condition that the centre of the bubble is fixed. In this paper, a position-related Rayleigh-Plesset equation is proposed to describe the cavitation bubble's floating movement in aluminium-silicon alloy of 750°C with the coefficient of viscosity of 0.0012. As the calculation results, a bubble stimulated by high-low-frequency vibration can float up faster with violent vibration.

Molecular Dynamics Modeling the Nano-Identation of Titanium

2021 ◽  
Author(s):  
Peiqiang Yang ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Rajiv Shivpuri
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Titanium Alloys ◽  
Large Scale ◽  
Mechanical Response ◽  
Pure Titanium ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Nano Indentation ◽  
Molecular Dynamics Modeling

Abstract Titanium alloys’ excellent mechanical and physical properties make it the most popular material widely used in aerospace, medical, nuclear and other significant industries. The study of titanium alloys mainly focused on the macroscopic mechanical mechanism. However, very few researches addressed the nanostructure of titanium alloys and its mechanical response in Nano-machining due to the difficulty to perform and characterize nano-machining experiment. Compared with nano-machining, nano-indentation is easier to characterize the microscopic plasticity of titanium alloys. This research presents a nano-indentation molecular dynamics model in titanium to address its microstructure alteration, plastic deformation and other mechanical response at the atomistic scale. Based on the molecular dynamics model, a complete nano-indentation cycle, including the loading and unloading stages, is performed by applying Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The plastic deformation mechanism of nano-indentation of titanium with a rigid diamond ball tip was studied under different indentation velocities. At the same time, the influence of different environment temperatures on the nano-plastic deformation of titanium is analyzed under the condition of constant indentation velocity. The simulation results show that the Young’s modulus of pure titanium calculated based on nano-indentation is about 110GPa, which is very close to the experimental results. The results also show that the mechanical behavior of titanium can be divided into three stages: elastic stage, yield stage and plastic stage during the nano-indentation process. In addition, indentation speed has influence on phase transitions and nucleation of dislocations in the range of 0.1–1.0 Å/ps.

scholarly journals The behavior of a gas–vapor system inside a cavitation bubble during axial valve operation

Vestnik IGEU ◽  
2020 ◽  
pp. 58-64 ◽  
Author(s):  
A.B. Kapranova ◽  
A.E. Lebedev ◽  
A.M. Melzer ◽  
S.V. Neklyudov
Keyword(s):  
Angular Momentum ◽  
Cavitation Bubble ◽  
Fluid Flows ◽  
Design Solution ◽  
Vapor Concentration ◽  
Random Component ◽  
Negative Consequences ◽  
Control Valves ◽  
Cavitation Bubbles ◽  
Working Volume

The energy industry needs reliable, environmentally friendly control valves, which include the category of control valves. The creation of conditions for reducing the intensity of cavitation effects at the initial stages of its development determines the main purpose of the study which aims to prevent possible negative consequences of developed cavitation, which in their turn include erosion of the flowing surfaces of the elements of the specified equipment and vibrations that go beyond operating standards. One of the possible ways to solve the problem is to use the process of throttling fluid flows in the working volume of the control device. The particular interest is paid to the mathematical description of the mechanism of formation of cavitation bubbles in terms of gas–vapor system. To obtain analytical results for describing the behavior of the gas–vapor system of the macro-system of cavitation bubbles, we used the authoring stochastic model of the cavitation bubbles formation process in the flow part of the axial valve. The model was constructed on the basis of the energy method in the framework of the equilibrium representation of states of an energetically closed macro-system. The dependence of the random component of the angular momentum of the cavitation bubble on the flow coefficient of the valve and the conditional diameter of its flow cross section for various ratios of gas and vapor concentration inside the bubbles has been analysed. The implementation of the process of throttling fluid flows in the control valve using the proposed design solution to the separator–external locking shell allows reducing the random component of the angular momentum of the cavitation bubble and increasing the valve throughput coefficient at various stages of the separator opening.

Analyses of Full-Scale Tank Car Shell Impact Tests

2007 ◽  
Author(s):  
Y. H. Tang ◽  
H. Yu ◽  
J. E. Gordon ◽  
M. Priante ◽  
D. Y. Jeong ◽  
...  
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Three Dimensional ◽  
Full Scale ◽  
Collision Dynamics ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Rigid Plastic ◽  
Element Analysis ◽  
Closed Form Solutions

This paper describes analyses of a railroad tank car impacted at its side by a ram car with a rigid punch. This generalized collision, referred to as a shell impact, is examined using nonlinear (i.e., elastic-plastic) finite element analysis (FEA) and three-dimensional (3-D) collision dynamics modeling. Moreover, the analysis results are compared to full-scale test data to validate the models. Commercial software packages are used to carry out the nonlinear FEA (ABAQUS and LS-DYNA) and the 3-D collision dynamics analysis (ADAMS). Model results from the two finite element codes are compared to verify the analysis methodology. Results from static, nonlinear FEA are compared to closed-form solutions based on rigid-plastic collapse for additional verification of the analysis. Results from dynamic, nonlinear FEA are compared to data obtained from full-scale tests to validate the analysis. The collision dynamics model is calibrated using test data. While the nonlinear FEA requires high computational times, the collision dynamics model calculates gross behavior of the colliding cars in times that are several orders of magnitude less than the FEA models.

Effect of Self-Interstitial Diffusion Anisotropy in Electron-Irradiated Zirconium. A Cluster Dynamics Modeling

2005 ◽  
Vol 237-240 ◽  
pp. 659-664
Author(s):  
Frédéric Christien ◽  
Alain Barbu
Keyword(s):  
Point Defects ◽  
Thin Foil ◽  
Elastic Interaction ◽  
Dislocation Loops ◽  
Considerable Influence ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Diffusion Anisotropy ◽  
Vacancy Loops ◽  
Transmission Electron

Irradiation of metals leads to the formation of point-defects (vacancies and selfinterstitials) that usually agglomerate in the form of dislocation loops. Due to the elastic interaction between SIA (self-interstitial atoms) and dislocations, the loops absorb in most cases more SIA than vacancies. That is why the loops observed by transmission electron microscopy are almost always interstitial in nature. Nevertheless, vacancy loops have been observed in zirconium following electron or neutron irradiation (see for example [1]). Some authors proposed that this unexpected behavior could be accounted for by SIA diffusion anisotropy [2]. Following the approach proposed by Woo [2], the cluster dynamics model presented in [3] that describes point defect agglomeration was extended to the case where SIA diffusion is anisotropic. The model was then applied to the loop microstructure evolution of a zirconium thin foil irradiated with electrons in a high-voltage microscope. The main result is that, due to anisotropic SIA diffusion, the crystallographic orientation of the foil has considerable influence on the nature (vacancy or interstitial) of the loops that form during irradiation.

scholarly journals Study on the Collapse Process of Cavitation Bubbles Near the Concave Wall by Lattice Boltzmann Method Pseudo-Potential Model

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4398
Author(s):  
Yang Liu ◽  
Yong Peng
Keyword(s):  
Lattice Boltzmann ◽  
Cavitation Bubble ◽  
Potential Model ◽  
Relative Distance ◽  
Wall Region ◽  
Additional Pressure ◽  
Cavitation Bubbles ◽  
Concave Wall ◽  
Pseudo Potential ◽  
Collapse Process

In this paper, the lattice Boltzmann pseudo-potential model coupled the Carnahan–Starling (C-S) equation of state and Li’s force scheme are used to study the collapse process of cavitation bubbles near the concave wall. It mainly includes the collapse process of the single and double cavitation bubbles in the near-wall region. Studies have shown that the collapse velocity of a single cavitation bubble becomes slower as the additional pressure reduces, and the velocity of the micro-jet also decreases accordingly. Moreover, the second collapse of the cavitation bubble cannot be found if the additional pressure reduces further. When the cavitation bubble is located in different angles with vertical direction, its collapse direction is always perpendicular to the wall. If the double cavitation bubbles are arranged vertically, the collapse process of the upper bubble will be quicker, as the relative distance increases. When the relative distance between the bubbles is large enough, no second collapse can be found for the upper bubble. On the other hand, when two cavitation bubbles are in the horizontal arrangement, the suppression effect between cavitation bubbles decreases as the relative distance between the bubbles increases and the collapse position of cavitation bubbles moves from the lower part to the upper part.

scholarly journals Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES

2020 ◽  
Vol 10 (17) ◽  
pp. 5998 ◽  
Author(s):  
Jianping Yuan ◽  
Yang Chen ◽  
Longyan Wang ◽  
Yanxia Fu ◽  
Yunkai Zhou ◽  
...  
Keyword(s):  
Flow Field ◽  
Energy Loss ◽  
Dynamic Characteristics ◽  
Vortex Core ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
High Rotational Speed ◽  
Propulsion Efficiency ◽  
Cavitation Bubbles

When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers.

Systems dynamics model of a transition firm

2005 ◽  
Vol 31 (3) ◽  
pp. 67-80
Author(s):  
David L. Olson ◽  
Paraskeva Dimitrova‐Davidova ◽  
Ivan Stoykov
Keyword(s):  
System Dynamics ◽  
Multiple Criteria ◽  
Dynamics Simulation ◽  
Economic Systems ◽  
Eastern European ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Pedagogical Tool ◽  
Modeling Process ◽  
Eastern European Countries

Eastern European countries are undergoing a transition from centralized economic planning to more open economic systems. A team of Bulgarian and U.S. researchers have collaborated to study this problem, using a real Bulgarian winery as the focus of their research. System dynamics modeling was selected as a tool to provide better understanding of management issues. A framework for future objective research, and as a pedagogical tool. This system dynamics model generates output on a number of measures. This paper presents initial output from the model, reporting profit ability, risk, and market share measures. These multiple measures create the need for multiple criteria analysis. Three multiple criteria techniques are demonstrated, and their value in the system dynamics simulation modeling process is discussed.

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