On the impact of ultrasonic cavitation bubbles

2011 ◽  
Vol 226 (3) ◽  
pp. 681-694 ◽  
Author(s):  
A Abdullah ◽  
M Malaki ◽  
E Baghizadeh
Keyword(s):  
Solid Surface ◽  
Acoustic Pressure ◽  
Deformation Energy ◽  
Ultrasonic Cavitation ◽  
Experimental Results ◽  
Pressure Amplitude ◽  
Aluminium Foil ◽  
Numerical Studies ◽  
The Impact ◽  
Good Agreement

The main purpose of this study was to determine the impulse of a bubble on a solid surface or the amount of energy transmitted to the surface by the bubble. To do this, the results of previous numerical studies were used to derive a relationship between the speed of microjet and acoustic pressure amplitude. It was found that the speed of microjet is proportional to the logarithm of the acoustic pressure amplitude. Aluminium foil specimens were exposed to cavitation for 3 s and the dimensions of pits generated on specimens were measured. Then, the deformation energy of each pit and the corresponding impulse were calculated. The trend of experimental results was in a good agreement with the theoretical ones but their exact values were not.

Numerical Studies on Dynamic Behavior of Tubular Pipes Under Repeated Impacts

2020 ◽  
Author(s):  
Ling Zhu ◽  
Xiangui Wang ◽  
Kailing Guo ◽  
Bin Ma
Keyword(s):  
Numerical Simulation ◽  
Plastic Deformation ◽  
Dynamic Behavior ◽  
Deformation Energy ◽  
Repeated Impact ◽  
Numerical Studies ◽  
Repeated Impacts ◽  
The Impact ◽  
Local Dent ◽  
Good Agreement

Abstract The tubular pipes of Jacket platform may be frequently subjected to repeated impact loadings from vessels and dropped objects during the operation life, which may lead to serious damages to the platform. In this paper, the numerical studies on dynamic behavior of tubular pipe subjected to repeated impact loadings was performed. The deformation profile and permanent deflection in numerical simulation were compared with those in experiment, and good agreement was achieved. Besides, the mechanism of deformation accumulation and energy absorption were analyzed. Results showed that, the tubular pipe mainly produced transverse expanding and local dent, the global bending was very small. The permanent deflection at the middle of the pipe increased as the impact numbers increased, while the increment decreased. In addition, with the increase of impact number, the elastic deformation energy stored by the tubular pipe increased, and the plastic deformation energy decreased.

An Experimental Study on Rigid-Object Water-Entry Impact and Contact Dynamics

2010 ◽  
Author(s):  
Ravi Challa ◽  
V. G. Idichandy ◽  
C. P. Vendhan ◽  
Solomon Yim
Keyword(s):  
Contact Dynamics ◽  
Experimental Results ◽  
Scale Model ◽  
Water Impact ◽  
Major Purpose ◽  
Closed Form Solutions ◽  
Numerical Studies ◽  
Wave Basin ◽  
Drop Tests ◽  
The Impact

The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in this paper. Tests from a range of drop heights were performed in a wave basin using a 1/6th-Froude scale model of a practical prototype using different drop mechanisms to determine the water impact and contact effects. The first experimental case involved dropping the WLO by using a rope and pulley arrangement, while the second case employed an electromagnetic release to drop the object. Hydrodynamic parameters including peak acceleration, touchdown pressure and maximum impact/contact force were measured using the two different drop mechanisms. The WLO was assumed as rigid, so the experimental results could be correlated with von Karman and Wagner closed form solutions and the maximum accelerations predicted are bounded by these classical analytical solutions. The major purpose of this study are to use the experiments to determine trends that occur when the object is dropped from successive heights using different drop mechanisms by varying the entry speed, angle of impact and the weight of the object. The predictions from the experimental results were used for subsequent numerical studies. Results from the drop tests show that the impact acceleration and touchdown pressure increases practically linearly with the increase in the height of the drop and the data provides conditions of drop mechanism that keep impact accelerations under specified limits for the WLO prototype.

Effect of Shear in Transverse Impact on Beams

1951 ◽  
Vol 165 (1) ◽  
pp. 176-188 ◽  
Author(s):  
D. G. Christopherson
Keyword(s):  
Elastic Wave ◽  
Shear Stiffness ◽  
Bending Stiffness ◽  
Experimental Results ◽  
Maximum Force ◽  
Transverse Impact ◽  
Wide Range ◽  
The Impact ◽  
Dominant Part ◽  
Good Agreement

In this paper the problem of transverse impact on a uniform beam is considered theoretically. Two examples which can be taken as representing a wide range of impacts which occur in practice are referred to particularly: (1) the beam struck transversely by a uniform square-ended rod travelling perpendicularly to it; (2) the same problem for the striker having a spherical end. In these examples it is shown that the ability of the beam to deflect in shear as well as in bending plays a dominant part in what takes place, and that, as far as the force between striker and beam is concerned, the length of the beam is usually without importance, as there is not time during the impact for an elastic wave to travel to the ends of the beam and return. It is shown that in regard to example (2) the theory presented is in good agreement with Arnold's experimental results obtained some years previously, and curves are given from which the maximum force between beam and striker can be obtained in terms of three parameters, representing respectively the velocity, the mass, and the radius of the striker, each dependent on the ratio of shear stiffness to bending stiffness for the beam.

Study on Ultrasonic Cavitation Mechanism of Honing

2011 ◽  
Vol 189-193 ◽  
pp. 4149-4153 ◽  
Author(s):  
Guo Dong Liu ◽  
Xi Jing Zhu
Keyword(s):  
Nonlinear Dynamics ◽  
Theoretical Basis ◽  
Acoustic Pressure ◽  
Physical Phenomenon ◽  
Ultrasonic Cavitation ◽  
Precision Machining ◽  
Workpiece Surface ◽  
Cavitation Effect ◽  
Ultra Precision ◽  
The Impact

Ultrasonic cavitation is an extremely complex physical phenomenon. It displays a series of nonlinear dynamics as the bubbles oscillating, growth, shrinkage and even collapse. For ultrasonic honing, it causes the device to generate chatter and noise because of the cavitation effect, and even generates denudation on the workpiece surface. In this paper, it describes the cavitation mechanism in ultrasonic honing, and analysises the acoustic pressure of the formation of cavitation from the numerical, furthermore it experimentally demonstrated. It also analyzes the nonlinear oscillation of cavitation bubbles for the impact on the ultrasonic honing chatter. Through studying on ultrasonic cavitation mechanism of honing, it provided a theoretical basis to solution the problem of the ultrasonic honing chatter and improves the level of precision and ultra precision machining.

scholarly journals Analysis of a Tubular Torsionally Resonating Viscosity–Density Sensor

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3036
Author(s):  
Daniel Brunner ◽  
Joe Goodbread ◽  
Klaus Häusler ◽  
Sunil Kumar ◽  
Gernot Boiger ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Experimental Results ◽  
Static Case ◽  
Flow Loop ◽  
Actual Measurement ◽  
Wide Range ◽  
Laminar And Turbulent Flow ◽  
The Impact ◽  
Good Agreement

This paper discusses a state-of-the-art inline tubular sensor that can measure the viscosity–density ( ρ η ) of a passing fluid. In this study, experiments and numerical modelling were performed to develop a deeper understanding of the tubular sensor. Experimental results were compared with an analytical model of the torsional resonator. Good agreement was found at low viscosities, although the numerical model deviated slightly at higher viscosities. The sensor was used to measure viscosities in the range of 0.3–1000 mPa·s at a density of 1000 kg/m3. Above 50 mPa·s, numerical models predicted viscosity within ±5% of actual measurement. However, for lower viscosities, there was a higher deviation between model and experimental results up to a maximum of ±21% deviation at 0.3 mPa·s. The sensor was tested in a flow loop to determine the impact of both laminar and turbulent flow conditions. No significant deviations from the static case were found in either of the flow regimes. The numerical model developed for the tubular torsional sensor was shown to predict the sensor behavior over a wide range, enabling model-based design scaling.

A TWO-DIMENSIONAL DYNAMIC SIMULATION OF SOLID FRACTURE PART II: EXAMPLES

1995 ◽  
Vol 06 (03) ◽  
pp. 399-425 ◽  
Author(s):  
ALEXANDER V. POTAPOV ◽  
CHARLES S. CAMPBELL ◽  
MARK A. HOPKINS
Keyword(s):  
Ball Milling ◽  
Dynamic Simulation ◽  
Shear Failure ◽  
Experimental Results ◽  
Two Dimensional ◽  
Compressive Failure ◽  
Simple Systems ◽  
The Impact ◽  
Good Agreement ◽  
Many Particles

This paper uses the model described in Ref. 1 to simulate fracture in many simple systems with the goal of evaluating the advantages and deficiencies of the model. The examples include compressive failure of a rectangular sample, four-point shear failure of a beam and the impact of particles with a plate and binary impacts of particles. Where possible, the simulated results seem to be in good agreement with typical experimental results. Finally, a simulation of ball-milling, which involves the flow and fracture of many particles is shown to demonstrate the overall utility of the model.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

The Impact of Cash Mobs in the Vote with the Wallet Game: Experimental Results

2016 ◽  
Author(s):  
Leonardo Becchetti ◽  
Maurizio Fiaschetti ◽  
Francesco Salustri
Keyword(s):  
Experimental Results ◽  
The Impact

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

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