Oblique Impact of Thick Walled Pressurized Spheres as Used in Tennis

2005 ◽  
Vol 219 (11) ◽  
pp. 1179-1189 ◽  
Author(s):  
S J Haake ◽  
M J Carré ◽  
R Kirk ◽  
S R Goodwill
Keyword(s):  
Coefficient Of Friction ◽  
Momentum Flux ◽  
High Speed ◽  
Reaction Force ◽  
Oblique Impact ◽  
Tennis Ball ◽  
The Coefficient Of Friction ◽  
Impact Phase ◽  
Rotation Set ◽  
The Impact

A model is presented in which the normal impact of a thick walled pressurized sphere, such as a tennis ball, is modelled as a non-linear viscoelastic spring and damper, coupled with momentum-flux forces where the shell wall deforms with high stiffness and damping. These momentum-flux forces are only present in the impact phase and do not appear during restitution. Rotation set up during an oblique impact causes the momentum-flux forces at the front and rear of the sphere to be different such that the total vertical reaction force acts in front of the centre of mass when topspin is present. The sphere was allowed to deform and this caused both the torque and the effective moment of inertia of the sphere to decrease. The result of this is that the deformed sphere gains sufficient spin during impact for reverse slip to occur when the ball reforms towards the end of impact. Tennis balls were projected at two similarly constructed surfaces with a coefficient of friction of 0.51 and 0.62. It was found that displacements and rotations from the model compared well with experimental results recorded using a high-speed video running at 7100 frames per second. The model was able to predict these results with only the coefficient of friction as the varying parameter.

Reduction of ground-borne vibrations from rail lines on viaducts by means of elastic anti-vibration mats

2018 ◽  
Vol 233 (5) ◽  
pp. 550-565
Author(s):  
Caiyou Zhao ◽  
Wang Ping ◽  
Mengting Xing ◽  
Qiang Yi ◽  
Liuchong Wang
Keyword(s):  
High Speed ◽  
Reaction Force ◽  
Field Tests ◽  
Ground Vibration ◽  
Coupling System ◽  
Step Procedure ◽  
Measurement Results ◽  
Track Bridge ◽  
Bridge Bearing ◽  
The Impact

In this paper, the effectiveness of elastic anti-vibration mats in reducing ground-borne vibrations from rail viaducts is investigated by means of theoretical analysis and is validated by the results of field tests. A two-step procedure is adopted for analyzing the vehicle-track-bridge-soil coupling system. In the first step, the train-track-bridge-pier subsystem is considered, and the bridge-bearing reaction force is solved. In the second step, the pier-pile-soil subsystem is considered, and the ground vibration solution is obtained by applying the negative bridge-bearing reaction force to the pier top on a pier-pile-soil model. The accuracy of the presented model is then verified in comparison with in-situ measurement results. On the basis of this comparison, a parametric study on the impact of anti-vibration mats on ground-borne vibrations was investigated theoretically, and the effectiveness of elastic anti-vibration mats with the suggested optimal parameters was further validated by field tests. The results show that when the stiffness of the elastic anti-vibration mats is 1.5 MPa/m, ground vibration decreases significantly and the vertical rail displacement agrees with high-speed railway regulations.

Effect of Cross-Flow Swirl on the Trajectory of Spray in an Annular Passage

2020 ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari
Keyword(s):  
Momentum Flux ◽  
High Speed ◽  
Air Flow ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Swirl Number ◽  
Flow Swirl ◽  
Air Stream ◽  
The Impact

Abstract This paper presents the experimental analysis of the impact of swirl number of cross-flowing air stream on liquid jet spray trajectory at a fixed air flow velocity of 42 m/s with the corresponding Mach number of 0.12. The experiments were conducted for 4 different swirl numbers (0, 0.2, 0.42 and 0.73) using swirl vanes at air inlet having angles of 0°, 15°, 30° and 45° respectively. Liquid to air momentum flux ratio (q) was varied from 5 to 25. High speed (@ 500 fps) images of the spray were captured and those images were processed using MATLAB to obtain the path of the spray at various momentum flux ratios. The results show interesting trends for the spray trajectory and the jet spread in swirling air flow. High swirling flows not only lead to spray with lower radial penetration due to sharp bending and disintegration of liquid jet, but also result in spray with high jet spread and spray area. Based on the results, correlations for the spray path have been proposed which incorporates the effects of the swirl number of the air flow.

scholarly journals Effect of Iron Oxide Nanoparticles on the Properties of Water-Based Drilling Fluids

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6718
Author(s):  
Muhammad Awais Ashfaq Alvi ◽  
Mesfin Belayneh ◽  
Sulalit Bandyopadhyay ◽  
Mona Wetrhus Minde
Keyword(s):  
Iron Oxide ◽  
Coefficient Of Friction ◽  
Drilling Fluid ◽  
Precipitation Method ◽  
Fluid Loss ◽  
Drilling Fluids ◽  
The Coefficient Of Friction ◽  
Filtrate Loss ◽  
Co Precipitation ◽  
The Impact

In recent years, several studies have indicated the impact of nanoparticles (NPs) on various properties (such as viscosity and fluid loss) of conventional drilling fluids. Our previous study with commercial iron oxide NPs indicated the potential of using NPs to improve the properties of a laboratory bentonite-based drilling fluid without barite. In the present work, iron oxide NPs have been synthesized using the co-precipitation method. The effect of these hydrophilic NPs has been evaluated in bentonite and KCl-based drilling fluids. Rheological properties at different temperatures, viscoelastic properties, lubricity, and filtrate loss were measured to study the effect of NPs on the base fluid. Also, elemental analysis of the filtrate and microscale analysis of the filter cake was performed. Results for bentonite-based fluid showed that 0.019 wt% (0.1 g) of NPs reduced the coefficient of friction by 47%, and 0.0095 wt% (0.05 g) of NPs reduced the fluid loss by 20%. Moreover, for KCl-based fluids, 0.019 wt% (0.1 g) of additive reduced the coefficient of friction by 45%, while higher concentration of 0.038 wt% (0.2 g) of NPs shows 14% reduction in the filtrate loss. Microscale analysis shows that presence of NPs in the cake structure produces a more compact and less porous structure. This study indicates that very small concentration of NPs can provide better performance for the drilling fluids. Additionally, results from this work indicate the ability of NPs to fine-tune the properties of drilling fluids.

High-speed non-invasive measurement of tibial rotation during the impact phase of running

Ergonomics ◽  
2005 ◽  
Vol 48 (11-14) ◽  
pp. 1623-1637 ◽  
Author(s):  
C. J. Digby ◽  
M. J. Lake ◽  
A. Lees
Keyword(s):  
High Speed ◽  
Tibial Rotation ◽  
Non Invasive ◽  
Impact Phase ◽  
The Impact ◽  
Invasive Measurement

scholarly journals Oblique impact of a smooth body on a thin layer of inviscid liquid

2013 ◽  
Vol 469 (2151) ◽  
pp. 20120615 ◽  
Author(s):  
T. I. Khabakhpasheva ◽  
A. A. Korobkin
Keyword(s):  
Body Surface ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Hydrodynamic Pressure ◽  
Oblique Impact ◽  
The Body ◽  
Second Stage ◽  
Smooth Body ◽  
Vertical Displacements ◽  
The Impact

The two-dimensional motion of a rigid body with a smooth surface is studied during its oblique impact on a liquid layer. The problem is coupled: the three degrees of freedom of the moving body are determined together with the liquid flow and the hydrodynamic pressure along the wetted part of the body surface. The impact process is divided into two temporal stages. During the first stage, the wetted region expands at a high speed with jetting flows at both ends of the wetted region. In the second stage, the free surface of the liquid is allowed to separate from the body surface. The position of the separation point is determined with the help of the Brillouin–Villat condition. Calculations are performed for elliptic cylinders of different masses and with different orientations and speeds before the impact. The horizontal and vertical displacements of the body, as well as its angle of rotation and corresponding speeds are investigated. The model developed remains valid until the body either touches the bottom of the liquid or rebounds from the liquid.

Behavior of Soft Spheres During Impact by High-Speed Photography

1983 ◽  
Vol 105 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Yoichi Tatara
Keyword(s):  
Deformation Process ◽  
High Speed ◽  
High Impact ◽  
High Speed Photography ◽  
Tennis Ball ◽  
Hertz Model ◽  
Hertz Theory ◽  
Soft Spheres ◽  
Almost All ◽  
The Impact

Previously, it has been verified experimentally for durations of impact that the Hertz theory (the quasi-statical theory) holds during impact of spheres without any exception. However, no measurement of duration of impact has been presented for spheres of materials other than metal. This study presents exceptional cases of impacts of spheres during which the Hertz model does not directly hold. By the use of a high-speed camera running at a speed of 5000 frames/s, durations of impact are measured directly for impacts of two solid rubber spheres of the same size and content and impacts of a soft ball (Japanese type-soft tennis ball) on a rigid foundation. As a result, the measured durations of impact in the two impacting cases are found to be decreased as the impact velocity is increased, similar in tendency to durations of impact of elastic metal spheres during which the Hertz theory holds. However, the measured durations of impact are found to be clearly shorter than results calculated according to the Hertz theory, approximately half in the former impacts at high impact velocities, and about 70 percent of the Hertzian results in the latter impacts at almost all impact velocities. Deformation process of the ball impacting on the foundation is also presented to indicate both durations in the compressive process and the restitution one to be shorter than those expected by the Hertz theory. The other results observed on the films are noted to investigate the origin of the great discrepancies between the measured and Hertzian durations (that is, the impacting mechanism of the rubber spheres or the rubber ball packed with air treated here).

Modelling and Simulation of the Hand-Arm-System During Impact Influences

2012 ◽  
Author(s):  
Sven Matthiesen ◽  
Tobias Schäfer ◽  
Sebastian Mangold
Keyword(s):  
High Speed ◽  
Mechanical Response ◽  
Reaction Force ◽  
Human Hand ◽  
Movement Velocity ◽  
Time Period ◽  
Acceleration Sensors ◽  
Impact Phase ◽  
Short Time ◽  
Two Degree Of Freedom

Most common models of hand-arm systems describe the mechanical response by low accelerations and short movements. The focus of this paper is on impacts (over 4.000 m/s2) to the human hand-arm system, in this case caused by a bolt setting device. To develop an accurate model of the hand-arm system, the force needed to be measured without to influence the interaction. Because of the very short time period it is not possible to measure the reaction force directly. To investigate the effects of different operators on the behavior of the power tool, a two-degree-of-freedom model of hand-arm-systems is developed, to predict mechanical interactions of the hand-arm-system with the power tool. Inputs for this simulation model are movement, velocity and acceleration. The motion of the device in the heavy impact phase is tracked by a high-speed camera and time-synchronized acceleration sensors. Based on this data, a robust and easy model of a hand-arm system is presented.

Formation of a High-speed Mode of Vibration Displacement of Grain During Heat Treatment

2020 ◽  
pp. 88-96
Author(s):  
Roman Kalinichenko ◽  
◽  
Serhii Stepanenko ◽  
Boris Kotov ◽  
◽  
...  
Keyword(s):  
Heat Treatment ◽  
Differential Equations ◽  
Coefficient Of Friction ◽  
High Speed ◽  
Air Flow ◽  
Support Surface ◽  
System Of Differential Equations ◽  
Vibration Displacement ◽  
The Coefficient Of Friction ◽  
Speed Mode

The article compiled and solved a system of differential equations of motion of a material point along a porous (air-permeable) surface, which is inclined at an angle to the horizon. Based on the analysis of solutions to this system of differential equations, it is proposed to change the speed of grain movement by the frequency of oscillations of the support surface, the angle of inclination of the support surface to the horizon and the coefficient of friction. Also, the graphical dependences of the speed of grain movement on the angle of inclination of the support surface to the horizon, the coefficient of friction and the frequency of oscillations were obtained. The possibility of decelerating the vibration movement of grain by an air flow, which is fed from the bottom of the porous support surface against (at an angle) the direction of grain movement, as well as using an asymmetrically corrugated support surface with vertical perforations, is theoretically substantiated. A linear regression dependence of the change in the vibration displacement speed has been experimentally determined, which makes it possible to form the required speed mode of vibration displacement of grain by changing the parameters: the inclination of the vibrating plane is 50 ÷ 90, the vibration frequency is 45 ÷ 55 s-1, the air flow speed is 0.1 ÷ 2 m/s in optimal operating modes. installations for high-intensity heat treatment of grain with a vibratory conveyor.

Coefficient of Friction for Aluminum Alloy Sheet in Contact with Polyurethane Rubber

2010 ◽  
Vol 26-28 ◽  
pp. 320-325 ◽  
Author(s):  
Li Li Wang ◽  
Dong Sheng Li ◽  
Xiao Qiang Li ◽  
Liang Wang ◽  
Wei Jun Yang
Keyword(s):  
Aluminum Alloy ◽  
Coefficient Of Friction ◽  
Normal Load ◽  
Orthogonal Experimental Design ◽  
Sliding Velocity ◽  
Stretch Forming ◽  
Forming Process ◽  
Alloy Material ◽  
The Coefficient Of Friction ◽  
The Impact

Stretch forming process of aircraft skin over reconfigurable compliant tooling is a new technology in skin manufacturing. During this process, the coefficient of friction is important for modeling accurately the process of stretch forming. The objective of this research is to measure the coefficient of friction for aluminum alloy in contact with polyurethane rubber in reciprocal sliding. An orthogonal experimental design was used to reveal the impact of four factors on the coefficient of friction, including lubrication, normal load, aluminum alloy material and sliding velocity. It is shown that lubrication is a major factor, sliding velocity is a minor factor. The influence of normal pressure is less than sliding velocity and the influence of aluminum alloy material is not very obvious. Finally, based on the experiment results, the selections of lubricant and stretching velocity are discussed in order to improve the process of stretch forming.

Spin generation during an oblique impact of a compliant ball on a non-compliant surface

2011 ◽  
Vol 226 (2) ◽  
pp. 86-95 ◽  
Author(s):  
Tom Allen ◽  
James Ibbitson ◽  
Steve Haake
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Oblique Impact ◽  
Tennis Ball ◽  
Compliant Surface ◽  
Oblique Impacts ◽  
Impact Characteristics ◽  
The Impact ◽  
The Finite Element Model

Oblique impacts between a ball and surface are a key part of many sports. Previous work has shown that a ball can slide, over-spin or roll at the end of an impact, depending on impact conditions. Inbound spin ratio was analysed to determine if it could be used to identify what is likely to happen at the end of impact for all sports regardless of surface, ball type, impact velocity, angle and spin. A predictive model, in the form of a finite element model, of a tennis ball was validated against experimental data for oblique impacts with inbound spin ratios in the range of –1 to 1. Spin ratio is defined as the product of the ball’s angular velocity and radius divided by the centre of mass velocity tangential to the surface. The finite element model was then used to determine the effect of impact conditions and ball parameters on outbound spin ratio. The study showed that for constant inbound spin ratio, outbound spin ratio was dependent on inbound velocity and angle. For constant inbound velocity and angle, decreasing the mass and increasing the stiffness of the ball through a change in material properties resulted in an increase in the maximum outbound spin ratio. Inbound spin ratio can be used to predict how a ball will rebound from a surface; however, inbound velocity and angle must be constant. Spin ratio can therefore be used to compare the impact characteristics for different ball and surface scenarios.

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