Investigation for Synchronization of a Rotor-Pendulum System considering the Multi-DOF Vibration

Directory of Open Access Journals (Sweden)

Yongjun Hou

2016-01-01

Full Text Available This work is a continuation for our published literature for vibration synchronization. A new mechanism, two rotors coupled with a pendulum rod in a multi-DOF vibration system, is proposed to implement coupling synchronization, and the dynamics equation of mechanism is derived by Lagrange equation. In addition, the coupling relationship between the vibrobody and the pendulum rod is ascertained with the Laplace transformation method, based on the dimensionless equation of the dynamics system. The Poincare method is employed to study the synchronization state between the two unbalanced rotors, which is converted into that of existence and the stability of solutions for synchronization-balance equations. The obtained results are supported by computer simulations. It is demonstrated that the values of the spring stiffness coefficient, the length of the pendulum, and the angular installation of the pendulum are important parameters with respect to the synchronous behavior in the rotor-pendulum system.

Singularities in Structural Optimization of the Ziegler Pendulum

Directory of Open Access Journals (Sweden)

O. N. Kirillov

2011-01-01

Full Text Available Structural optimization of non-conservative systems with respect to stability criteria is a research area with important applications in fluid-structure interactions, friction-induced instabilities, and civil engineering. In contrast to optimization of conservative systems where rigorously proven optimal solutions in buckling problems have been found, for nonconservative optimization problems only numerically optimized designs have been reported. The proof of optimality in non-conservative optimization problems is a mathematical challenge related to multiple eigenvalues, singularities in the stability domain, and non-convexity of the merit functional. We present here a study of optimal mass distribution in a classical Ziegler pendulum where local and global extrema can be found explicitly. In particular, for the undamped case, the two maxima of the critical flutter load correspond to a vanishing mass either in a joint or at the free end of the pendulum; in the minimum, the ratio of the masses is equal to the ratio of the stiffness coefficients. The role of the singularities on the stability boundary in the optimization is highlighted, and an extension to the damped case as well as to the case of higher degrees of freedom is discussed.

Evaluation of the Autoparametric Pendulum Vibration Absorber for a Duffing System

Directory of Open Access Journals (Sweden)

Benjamın Vazquez-Gonzalez

2008-01-01

Full Text Available In this work we study the frequency and dynamic response of a damped Duffing system attached to a parametrically excited pendulum vibration absorber. The multiple scales method is applied to get the autoparametric resonance conditions and the results are compared with a similar application of a pendulum absorber for a linear primary system. The approximate frequency analysis reveals that the nonlinear dynamics of the externally excited system are suppressed by the pendulum absorber and, under this condition, the primary Duffing system yields a time response almost equivalent to that obtained for a linear primary system, although the absorber frequency response is drastically modified and affected by the cubic stiffness, thus modifying the jumps defined by the fixed points. In the absorber frequency response can be appreciated a good absorption capability for certain ranges of nonlinear stiffness and the internal coupling is maintained by the existing damping between the pendulum and the primary system. Moreover, the stability of the coupled system is also affected by some extra fixed points introduced by the cubic stiffness, which is illustrated with several amplitude-force responses. Some numerical simulations of the approximate frequency responses and dynamic behavior are performed to show the steady-state and transient responses.

Advanced Control of Wheeled Inverted Pendulum Systems

CERN Document Server

Li, Zhijun; Fan, Liping

2013-01-01

Advanced Control of Wheeled Inverted Pendulum Systems is an orderly presentation of recent ideas for overcoming the complications inherent in the control of wheeled inverted pendulum (WIP) systems, in the presence of uncertain dynamics, nonholonomic kinematic constraints as well as underactuated configurations. The text leads the reader in a theoretical exploration of problems in kinematics，dynamics modeling, advanced control design techniques,and trajectory generation for WIPs. An important concern is how to deal with various uncertainties associated with the nominal model, WIPs being characterized by unstable balance and unmodelled dynamics and being subject to time-varying external disturbances for which accurate models are hard to come by.   The book is self-contained, supplying the reader with everything from mathematical preliminaries and the basic Lagrange-Euler-based derivation of dynamics equations to various advanced motion control and force control approaches as well as trajectory generation met...

Optimal control of inverted pendulum system using PID controller, LQR and MPC

Science.gov (United States)

Varghese, Elisa Sara; Vincent, Anju K.; Bagyaveereswaran, V.

2017-11-01

Inverted pendulum is a highly nonlinear system. Here we propose an optimal control technique for the control of an inverted Pendulum - cart system. The system is modeled, linearized and controlled. Here, the control objective is to control the system such that when the cart reaches a desired position the inverted pendulum stabilizes in the upright position. Initially PID controller is used to control the system. Later, Linear Quadratic Regulator (LQR) a well-known optimal control technique which makes use of the states of the dynamical system and control input to frame the optimal control decision is used. Various combinations of both PID and LQR controllers are implemented. To validate the robustness of the controller, the system is simulated with and without disturbance. Finally the system is also controlled using Model Predictive controller (MPC). MPC has well predictive ability to calculate future events and implement necessary control actions. The performance of the system is compared and analyzed.

The Pendulum A Case Study in Physics

CERN Document Server

Baker, Gregory L

2005-01-01

The pendulum: a case study in physics is a unique book in several ways. Firstly, it is a comprehensive quantitative study of one physical system, the pendulum, from the viewpoint of elementary and more advanced classical physics, modern chaotic dynamics, and quantum mechanics. In addition, coupled pendulums and pendulum analogs of superconducting devices are also discussed. Secondly, this book treats the physics of the pendulum within a historical and cultural context,showing, for example, that the pendulum has been intimately connected with studies of the earth's density, the earth's motion,

Oscillatory variation of anomalous diffusion in pendulum systems

Indian Academy of Sciences (India)

driven and parametrically-driven pendulum systems are presented. When the frequency of the periodic driving force is varied, the exponent μ, which is the rate of divergence of the mean square displacement with time, is found to vary in an ...

Coupled oscillators in identification of nonlinear damping of a real parametric pendulum

Science.gov (United States)

Olejnik, Paweł; Awrejcewicz, Jan

2018-01-01

A damped parametric pendulum with friction is identified twice by means of its precise and imprecise mathematical model. A laboratory test stand designed for experimental investigations of nonlinear effects determined by a viscous resistance and the stick-slip phenomenon serves as the model mechanical system. An influence of accurateness of mathematical modeling on the time variability of the nonlinear damping coefficient of the oscillator is proved. A free decay response of a precisely and imprecisely modeled physical pendulum is dependent on two different time-varying coefficients of damping. The coefficients of the analyzed parametric oscillator are identified with the use of a new semi-empirical method based on a coupled oscillators approach, utilizing the fractional order derivative of the discrete measurement series treated as an input to the numerical model. Results of application of the proposed method of identification of the nonlinear coefficients of the damped parametric oscillator have been illustrated and extensively discussed.

Swinging control of two-pendulum system under energy constraints

NARCIS (Netherlands)

Ananyevskiy, M.S.; Fradkov, A.L.; Nijmeijer, H.; Leonov, G.; Nijmeijer, H.; Pogromsky, A.; Fradkov, A.

2009-01-01

A method for control of mechanical systems under phase constraints, applicable to energy control of Hamiltonian systems is proposed. The constrained energy control problem for two pendulums by a single control action is studied both analytically and numerically. It is shown that for a proper choice

A New Inverted Torsion Pendulum-Based Mechanical Spectrometer to Study Soft Matter

Directory of Open Access Journals (Sweden)

Lei M.L.

2016-03-01

Full Text Available A new multifunctional mechanical spectrometer is developed based on an inverted torsion pendulum showing high precision in a wide frequency range to study soft matter. Apart from measuring the internal friction of solids it can also be used to study viscoelasticity. In this report we describe basic principles of the novel instrument.

Early results of micro-deformation measurements in Magdalena Jama (Slovenia) by a vertical static pendulum

Czech Academy of Sciences Publication Activity Database

Kalenda, Pavel; Neumann, L.; Šebela, S.

2013-01-01

Roč. 42, č. 1 (2013), s. 143-154 ISSN 0583-6050 Institutional support: RVO:67985891 Keywords : tilt * pendulum * deformations * earthquakes Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.710, year: 2013 http://ojs.zrc-sazu.si/carsologica/article/view/635

Experiments with a magnetically controlled pendulum

International Nuclear Information System (INIS)

Kraftmakher, Yaakov

2007-01-01

A magnetically controlled pendulum is used for observing free and forced oscillations, including nonlinear oscillations and chaotic motion. A data-acquisition system stores the data and displays time series of the oscillations and related phase plane plots, Poincare maps, Fourier spectra and histograms. The decay constant of the pendulum can be modified by positive or negative feedback. The apparatus, except for the data-acquisition system, is extremely simple and low cost, and can be assembled in a short time. The wide possibilities of varying the parameters of the pendulum make the experiments suitable for student projects

Control of mechnical systems with constraints: two pendulums case study

NARCIS (Netherlands)

Anayevskiy, M.S.; Fradkov, A.L.; Nijmeijer, H.; Cho, Hyungsuck

2008-01-01

A method for control of mechanical systems under phase constraints, applicable to energy control of Hamiltonian systems is proposed. The constrained energy control problem for two pendulums by a single control action is studied both analytically and numerically. It is shown that for a proper choice

Study of Inverted Pendulum Robot Using Fuzzy Servo Control Method

Directory of Open Access Journals (Sweden)

Dazhong Wang

2012-09-01

Full Text Available The inverted pendulum robot is a classical problem in controls. The inherit instabilities in the setup make it a natural target for a control system. Inverted pendulum robot is suitable to use for investigation and verification of various control methods for dynamic systems. Maintaining an equilibrium position of the pendulum pointing up is a challenge as this equilibrium position is unstable. As the inverted pendulum robot system is nonlinear it is well-suited to be controlled by fuzzy logic. In this paper, Lagrange method has been applied to develop the mathematical model of the system. The objective of the simulation to be shown using the fuzzy control method can stabilize the nonlinear system of inverted pendulum robot.

The Reaction Wheel Pendulum

CERN Document Server

Block, Daniel J; Spong, Mark W

2007-01-01

This monograph describes the Reaction Wheel Pendulum, the newest inverted-pendulum-like device for control education and research. We discuss the history and background of the reaction wheel pendulum and other similar experimental devices. We develop mathematical models of the reaction wheel pendulum in depth, including linear and nonlinear models, and models of the sensors and actuators that are used for feedback control. We treat various aspects of the control problem, from linear control of themotor, to stabilization of the pendulum about an equilibrium configuration using linear control, t

Multiple degree of freedom inverted pendulum dynamics: Modeling, computation, and experimentation

Science.gov (United States)

Chen, Cheng-Yuan Jerry

A pendulum is statically unstable in its upright inverted state due to the Earth's gravitational attraction which points downward. However, with proper forcing, the pendulum can be stabilized in its upright inverted state. Special interest is on periodic vertical forcing applied to the pendulum's base to stabilize it around the upright inverted equilibrium. Many researchers have studied how to stabilize the system by varying various parameters, in particular its amplitude and frequency. Most have focused on the single degree of freedom inverted pendulum case, which with linear assumption can be described via Mathieu's equation. The system stability can then be characterized by Floquet theory. Our focus is on searching for the periodic solutions inside the linearly stable region of the pendulum's inverted state when the pendulum is under proper periodic forcing. Our research shows that under appropriate excitation by controlling the forcing amplitude and frequency, the pendulum can maintain certain periodic orbits around its inverted state which we characterize in a systematic way. In this thesis, we applied four different kinds of geometric realizations of the system response: system time traces, system phase portraits, three dimensional views of the system phase portrait as a function of input forcing, and the system's power spectral density diagram. By analyzing these four diagrams simultaneously, we characterize different kinds of multi-frequency periodic behavior around the pendulum's inverted state. To further discuss the effect of the nonlinearity, we applied perturbation techniques using the normalized forcing amplitude as a perturbation parameter to carry out the approximate periodic solutions on a single degree of freedom inverted pendulum nonlinear model. We also discuss the multiple degree of freedom inverted pendulum system. Both numerical simulation and experiments were performed and detailed comparisons are discussed. Our numerical simulations show

Analogy between dynamics of thermo-rheological and piezo-rheological pendulums

International Nuclear Information System (INIS)

Hedrih, K

2008-01-01

The constitutive stress-strain relations of the standard thermo-rheological and piezo-rheological hereditary element in differential form as well as in two different integro-differential forms are defined. The considered problem of a thermo-rheological hereditary discrete system nonlinear dynamics in the form of thermo-rheological double pendulum system with coupled pendulums gets the significance of two constrained bodies in plane motion problem, as a problem important for studying a sensor dynamics or actuator dynamics in active structure dynamics. System of the averaged equations in the first approximation for amplitudes and phases are derived and qualitatively analyzed. Analogy between nonlinear dynamics of the double pendulum systems with thermo-rheological and piezo-rheological properties between pendulums is pointed out

A Laboratory Experiment on Coupled Non-Identical Pendulums

Science.gov (United States)

Li, Ang; Zeng, Jingyi; Yang, Hujiang; Xiao, Jinghua

2011-01-01

In this paper, coupled pendulums with different lengths are studied. Through steel magnets, each pendulum is coupled with others, and a stepping motor is used to drive the whole system. To record the data automatically, we designed a data acquisition system with a CCD camera connected to a computer. The coupled system shows in-phase, locked-phase…

Influence of radiation damage on internal friction background

International Nuclear Information System (INIS)

Burbelo, R.M.; Grinik, Eh.U.; Paliokha, M.I.; Orlinskij, A.B.

1984-01-01

Influence of radiation damage on internal friction background in samples of polycrystalline nickel and iron irradiated by a fast neutron flux approximately 10 14 neutr/(cm 2 xs) at 350 deg C has been studied using the low-frequency unit of the reverse torsion pendulum type. It has been established experimentally that a high-temperature background of internal friction of iron and nickel samples decreases as accumulating radiation defects occurring under neutron irradiation. Assumptions on a possible mechanism of the effect have been proposed. Simple expression for the background magnitude evaluation has been suggested

On the Dynamics of the Furuta Pendulum

Directory of Open Access Journals (Sweden)

Benjamin Seth Cazzolato

2011-01-01

Full Text Available The Furuta pendulum, or rotational inverted pendulum, is a system found in many control labs. It provides a compact yet impressive platform for control demonstrations and draws the attention of the control community as a platform for the development of nonlinear control laws. Despite the popularity of the platform, there are very few papers which employ the correct dynamics and only one that derives the full system dynamics. In this paper, the full dynamics of the Furuta pendulum are derived using two methods: a Lagrangian formulation and an iterative Newton-Euler formulation. Approximations are made to the full dynamics which converge to the more commonly presented expressions. The system dynamics are then linearised using a Jacobian. To illustrate the influence the commonly neglected inertia terms have on the system dynamics, a brief example is offered.

The Multiple Pendulum Problem via Maple[R

Science.gov (United States)

Salisbury, K. L.; Knight, D. G.

2002-01-01

The way in which computer algebra systems, such as Maple, have made the study of physical problems of some considerable complexity accessible to mathematicians and scientists with modest computational skills is illustrated by solving the multiple pendulum problem. A solution is obtained for four pendulums with no restriction on the size of the…

Static frictional resistance with the slide low-friction elastomeric ligature system.

Science.gov (United States)

Jones, Steven P; Ben Bihi, Saida

2009-11-01

This ex-vivo study compared the static frictional resistance of a low-friction ligation system against a conventional elastomeric module, and studied the effect of storage in a simulated oral environment on the static frictional resistance of both ligation systems. Eighty stainless steel brackets were tested by sliding along straight lengths of 0.018 inch round and 0.019 x 0.025 inch rectangular stainless steel wires ligated with either conventional elastomerics or the Slide system (Leone, Florence, Italy). During the tests the brackets and wires were lubricated with artificial saliva. A specially constructed jig assembly was used to hold the bracket and archwire securely. The jig was clamped in an Instron universal load testing machine. Crosshead speed was controlled via a microcomputer connected to the Instron machine. The static frictional forces at 0 degree bracket/wire angulation were measured for both systems, fresh from the pack and after storage in artificial saliva at 37 degrees C for 24 hours. The results of this investigation demonstrated that the Slide ligatures produced significantly lower static frictional resistance than conventional elastomeric modules in the fresh condition and after 24 hours of storage in a simulated oral environment (p static frictional resistance of conventional elastomeric modules and the Slide system (p = 0.525). The claim by the manufacturer that the Slide system produces lower frictional resistance than conventional elastomeric modules is upheld.

Instrumentation, computer software and experimental techniques used in low-frequency internal friction studies at WNRE

International Nuclear Information System (INIS)

Sprugmann, K.W.; Ritchie, I.G.

1980-04-01

A detailed and comprehensive account of the equipment, computer programs and experimental methods developed at the Whiteshell Nuclear Research Estalbishment for the study of low-frequency internal friction is presented. Part 1 describes the mechanical apparatus, electronic instrumentation and computer software, while Part II describes in detail the laboratory techniques and various types of experiments performed together with data reduction and analysis. Experimental procedures for the study of internal friction as a function of temperature, strain amplitude or time are described. Computer control of these experiments using the free-decay technique is outlined. In addition, a pendulum constant-amplitude drive system is described. (auth)

Versatile Friction Stir Welding/Friction Plug Welding System

Science.gov (United States)

Carter, Robert

2006-01-01

A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

Internal friction and microplasticity of ice Isub(h)

International Nuclear Information System (INIS)

Perez, J.; Mai, C.; Tatibouet, J.; Vassoille, R.

1976-01-01

This study is concerned with internal-friction measurements made at low frequency (torsion pendulum) on specimens of ice Isub(h). In the case of a single crystal, the spectrum of internal friction vs. temperature exhibits the classical relaxation peak. This peak is followed by an increase of damping above 260 K. Furthermore, in this temperature range, the internal friction delta is shown to be amplitude dependent: delta increases with shear strain γ as long as the temperature T is high. These features are strongly modified by plastic deformation of ice in particular i) high-temperature internal friction is increased as long as the plastic defomation ratio is important, ii) high-temperature internal friction becomes more amplitude dependent. In the high-temperature range the mobility of dislocations in ice increase quickly. During the internal-friction measurements the cyclic stress causes movement of linear defects and, hence, damping phenomena. Then, the theoretical analysis of the dynamic behaviour of dislocations in ice has been used to interpret the preceding results. This interpretation allows us to connect our damping data with the microplastic behaviour of ice

One pendulum to run them all

Science.gov (United States)

Barenboim, G.; Oteo, J. A.

2013-07-01

The analytical solution for the three-dimensional linear pendulum in a rotating frame of reference is obtained, including Coriolis and centrifugal accelerations, and expressed in terms of initial conditions. This result offers the possibility of treating Foucault and Bravais pendula as trajectories of the same system of equations, each of them with particular initial conditions. We compare them with the common two-dimensional approximations in textbooks. A previously unnoticed pattern in the three-dimensional Foucault pendulum attractor is presented.

Internal friction in martensitic carbon steels

International Nuclear Information System (INIS)

Hoyos, J.J.; Ghilarducci, A.A.; Salva, H.R.; Chaves, C.A.; Velez, J.M.

2009-01-01

This paper proposes relationships between the internal friction and the microstructure of two steels containing 0.626 and 0.71 wt.% carbon. The steels were annealed at 1093 K for 5 min, quenched into water and tempered for 10 min at 423, 573 and 723 K. Internal friction was measured by using a forced vibration pendulum, in a temperature range from 100 to 450 K. The internal friction spectrum is decomposed into four peaks: P1 at 215 K, P2 at 235 K, P3 at 260 K and P4 at 380 K for 3 Hz. Peak P1 is attributed to the interactions between dislocations and carbon atoms. Peak P2 is related to the interaction between dislocations and carbide. Peak P3 is related to the generations of kink - pairs along edge dislocations. Peak P4 is attributed to epsilon carbide precipitation.

Friction-induced Vibrations in an Experimental Drill-string System for Various Friction Situations

NARCIS (Netherlands)

Mihajlovic, N.; Wouw, van de N.; Hendriks, M.P.M.; Nijmeijer, H.

2005-01-01

Friction-induced limit cycling deteriorates system performance in a wide variety of mechanical systems. In this paper, we study the way in which essential friction characteristics affect the occurrence and nature of friction-induced limit cycling in flexible rotor systems. This study is performed on

Explicit analytical solution of a pendulum with periodically varying length

International Nuclear Information System (INIS)

Yang Tianzhi; Fang Bo; Li Song; Huang Wenhu

2010-01-01

A pendulum with periodically varying length is an interesting physical system. It has been studied by some researchers using traditional perturbation methods (for example, the averaging method). But due to the limitation of the conventional perturbation methods, the solutions are not valid for long-term prediction of the pendulum. In this paper, we use the homotopy analysis method to explore the approximate solution to this system. The method can easily self-adjust and control the convergence region. By applying the method to the governing equation of the pendulum, we obtain the approximation solution in a closed form. It is shown by the numerical method that the homotopy analysis method supplies a more accurate analytical solution for predicting the long-term behaviour of the pendulum. We believe that this system may be a good example for undergraduate and graduate students for better understanding of nonlinear oscillations.

One pendulum to run them all

International Nuclear Information System (INIS)

Barenboim, G; Oteo, J A

2013-01-01

The analytical solution for the three-dimensional linear pendulum in a rotating frame of reference is obtained, including Coriolis and centrifugal accelerations, and expressed in terms of initial conditions. This result offers the possibility of treating Foucault and Bravais pendula as trajectories of the same system of equations, each of them with particular initial conditions. We compare them with the common two-dimensional approximations in textbooks. A previously unnoticed pattern in the three-dimensional Foucault pendulum attractor is presented. (paper)

Foot trajectory approximation using the pendulum model of walking.

Science.gov (United States)

Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A; Hunt, Kenneth J

2014-01-01

Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.

A double pendulum plasma thrust balance and thrust measurement at a tandem mirror exhaust

International Nuclear Information System (INIS)

Yang, T.F.; Liu, P.; Chang-Diaz, F.R.; Lander, H.; Childs, R.A.; Becker, H.D.; Fairfax, S.A.

1995-01-01

For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement. copyright 1995 American Institute of Physics

Pendulum and modified pendulum appliances for maxillary molar distalization in Class II malocclusion - a systematic review.

Science.gov (United States)

Al-Thomali, Yousef; Basha, Sakeenabi; Mohamed, Roshan Noor

2017-08-01

The main purpose of the present systematic review was to evaluate the quantitative effects of the pendulum appliance and modified pendulum appliances for maxillary molar distalization in Class II malocclusion. Our systematic search included MEDLINE, EMBASE, CINAHL, PsychINFO, Scopus and key journals and review articles; the date of the last search was 30 January 2017. We graded the methodological quality of the studies by means of the Quality Assessment Tool for Quantitative Studies, developed for the Effective Public Health Practice Project (EPHPP). In total, 203 studies were identified for screening, and 25 studies were eligible. The quality assessment rated four (16%) of the study as being of strong quality and 21 (84%) of these studies as being of moderate quality. The pendulum appliances showed mean molar distalization of 2-6.4 mm, distal tipping of molars from 6.67° to 14.50° and anchorage loss with mean premolar and incisor mesial movement of 1.63-3.6 mm and 0.9-6.5 mm, respectively. The bone anchored pendulum appliances (BAPAs) showed mean molar distalization of 4.8-6.4 mm, distal tipping of molars from 9° to 11.3° and mean premolar distalization of 2.7-5.4 mm. Pendulum and modified pendulum appliances are effective in molar distalization. Pendulum appliance with K-loop modification, implant supported pendulum appliance and BAPA significantly reduced anchorage loss of the anterior teeth and distal tipping of the molar teeth.

The analitical modeling of the motion process of the inverted pendulum system

Directory of Open Access Journals (Sweden)

Obukhov Pavel

2017-01-01

Full Text Available In the article the conceptual description of the nonlinear mathematical model of the inverted pendulum is presented. The Lagrange’s equations of the second kind are applying to build of the model, the generalized coordinate are selected and the system of the differential equations of the fourth odder is formed.

A laboratory experiment on coupled non-identical pendulums

International Nuclear Information System (INIS)

Li Ang; Zeng Jingyi; Yang Hujiang; Xiao Jinghua

2011-01-01

In this paper, coupled pendulums with different lengths are studied. Through steel magnets, each pendulum is coupled with others, and a stepping motor is used to drive the whole system. To record the data automatically, we designed a data acquisition system with a CCD camera connected to a computer. The coupled system shows in-phase, locked-phase and anti-phase synchronizations when the driving frequency and the coupling strength are changed. With background knowledge from general physics and the simplicity of the equipment, this experiment is easy to implement and would be of interest to undergraduate students.

Foucault Pendulum without Driving

Science.gov (United States)

Yamashita, Yoshifumi

2016-06-01

Foucault pendulums are two-dimensional harmonic oscillators to which the Coriolis force is applied. The Foucault parameter ΩF is the ideal rate of rotation of the plane of oscillation due to the Coriolis force. Kamerlingh Onnes pointed out that the actual behavior of Foucault pendulums can be understood only by taking into account the unavoidable mechanical asymmetry, i.e., the difference between the frequency in the X-direction and that in the Y-direction, which is called the asymmetry parameter δ. Our equations of motion for Foucault pendulums are linear and their solutions are easily obtained. We are interested in slowly varying rotations of the plane of oscillation, where the angle of rotation is denoted by φ. The motion of the bob consists of rapid simple oscillations and the slow rotations mentioned above. Eliminating the rapid oscillations, we obtain an analytic expression for tan 2φ, which is a periodic function with period π /√{Ω F2 + δ 2} . The graphs of the rotation φ versus time t have two distinct appearances. Under the condition ΩF ≥ δ|cos(2θ)| (θ is the initial value of φ), φ decreases monotonically, which is the behavior expected for Foucault pendulums. Otherwise φ repeatedly increases and decreases, which is the behavior of pendulums describing Lissajous figures. The vertical component of angular momentum is also calculated analytically.

Piaget and the Pendulum

Science.gov (United States)

Bond, Trevor G.

Piaget's investigations into children's understanding of the laws governing the movement of a simple pendulum were first reported in 1955 as part of a report into how children's knowledge of the physical world changes during development. Chapter 4 of Inhelder & Piaget (1955/1958) entitled `The Oscillation of a Pendulum and the Operations of Exclusion'' demonstrated how adolescents could construct the experimental strategies necessary to isolate each of the variables, exclude the irrelevant factors and conclude concerning the causal role of length. This became one of the most easily replicable tasks from the Genevan school and was used in a number of important investigations to detect the onset of formal operational thinking. While it seems that the pendulum investigation fits nicely into Piaget's sequence of studies of concepts such as time, distance and speed suggested to him by Einstein, more recent research (Bond 2001) shows Inhelder to be directly responsible for the investigations into children's induction of physical laws. The inter-relationship between the pendulum problem, developing thought and scientific method is revealed in a number of Genevan and post-Piagetian investigations.

Internal friction in irradiated textolite

International Nuclear Information System (INIS)

Zajkin, Yu.A.; Kozhamkulov, B.A.; Koztaeva, U.P.

1996-01-01

Structural relaxation in irradiated textolite of ST and ST-EhTF trade marks presenting pressed material got by method of impregnation of fibreglass by phenole and epoxytriphenole binders relatively. Measuring of temperature dependences of internal friction (TDIF) is carried out in torsional pendulum at oscillation frequency 0.6-1.0 Hz before and after irradiation by stopped gamma-quanta with energy 3 MeV on electron accelerator EhLU-4. α and β peaks, related with segments motion in base and side chains of macromolecular have being observed on TDIF of all textolite. Growth of peaks height after irradiation evident about increase of segments mobility in base chain and about de-freezing of segments in side chains and it could be considered as qualitative measure of radiation destruction rate. Comparison of temperature dependences of internal friction indicates on higher radiation stability of textolite of ST-EhTF trade mark

Internal friction of metallic glass Ni74P16B6Al4 near T/sub x/

International Nuclear Information System (INIS)

Li Xiao-Guang; He Yizhen

1986-01-01

The internal friction of metallic glass Ni 74 P 16 B 6 Al 4 near the crystallization temperature T/sub x/ is investigated using a conventional torsion pendulum. Two internal friction peaks, P 1 and P 2 , are observed and the dependence of the peak positions on heating rate is described by the Kissinger equation. Pre-crystallization reduces the height of the peaks (P 1 and P 2 ) and shifts the positions of these peaks but in opposite directions. A formula showing the dependence of apparent internal friction on volume fraction transformed is derived. The variation of internal friction with annealing corresponds to the variation of the fraction transformed. (author)

Electromagnetic energy harvesting from a dual-mass pendulum oscillator

Science.gov (United States)

Wang, Hongyan; Tang, Jiong

2016-04-01

This paper presents the analysis of a type of vibration energy harvester composed of an electromagnetic pendulum oscillator combined to an elastic main structure. In this study, the elastic main structure connected to the base is considered as a single degree-of-freedom (DOF) spring-mass-damper subsystem. The electromagnetic pendulum oscillator is considered as a dual-mass two-frequency subsystem, which is composed of a hollow bar with a tip winded coil and a magnetic mass with a spring located in the hollow bar. As the pendulum swings, the magnetic mass can move along the axial direction of the bar. Thus, the relative motion between the magnet and the coil induces a wire current. A mathematical model of the coupled system is established. The system dynamics a 1:2:1 internal resonance. Parametric analysis is carried out to demonstrate the effect of the excitation acceleration, excitation frequency, load resistance, and frequency tuning parameters on system performance.

A new class of compact high sensitive tiltmeter based on the UNISA folded pendulum mechanical architecture

Science.gov (United States)

Barone, Fabrizio; Giordano, Gerardo

2018-02-01

We present the Extended Folded Pendulum Model (EFPM), a model developed for a quantitative description of the dynamical behavior of a folded pendulum generically oriented in space. This model, based on the Tait-Bryan angular reference system, highlights the relationship between the folded pendulum orientation in the gravitational field and its natural resonance frequency. Tis model validated by tests performed with a monolithic UNISA Folded Pendulum, highlights a new technique of implementation of folded pendulum based tiltmeters.

Position Control of Servo Systems Using Feed-Forward Friction Compensation

International Nuclear Information System (INIS)

Park, Min Gyu; Kim, Han Me; Shin, Jong Min; Kim, Jong Shik

2009-01-01

Friction is an important factor for precise position tracking control of servo systems. Servo systems with highly nonlinear friction are sensitive to the variation of operating condition. To overcome this problem, we use the LuGre friction model which can consider dynamic characteristics of friction. The LuGre friction model is used as a feed-forward compensator to improve tracking performance of servo systems. The parameters of the LuGre friction model are identified through experiments. The experimental result shows that the tracking performance of servo systems with higherly nonlinear friction can be improved by using feed-forward friction compensation

Pendulum Underwater - An Approach for Quantifying Viscosity

Science.gov (United States)

Leme, José Costa; Oliveira, Agostinho

2017-12-01

The purpose of the experiment presented in this paper is to quantify the viscosity of a liquid. Viscous effects are important in the flow of fluids in pipes, in the bloodstream, in the lubrication of engine parts, and in many other situations. In the present paper, the authors explore the oscillations of a physical pendulum in the form of a long and lightweight wire that carries a ball at its lower end, which is totally immersed in water, so as to determine the water viscosity. The system used represents a viscous damped pendulum and we tried different theoretical models to describe it. The experimental part of the present paper is based on a very simple and low-cost image capturing apparatus that can easily be replicated in a physics classroom. Data on the pendulum's amplitude as a function of time were acquired using digital video analysis with the open source software Tracker.

Pendulum Therapy of Molar Distalization in Mixed Dentition.

Science.gov (United States)

Patil, Raju Umaji; Prakash, Amit; Agarwal, Anshu

2016-01-01

Early and timely pedo-orthodontic treatment is aimed at eliminating the disturbances of skeletal or dentoalveolar development, to harmonize the stomatognathic system before the full eruption of all permanent teeth. The advantages of pendulum appliance are its minimal dependence on patient's compliance (child cooperation), ease of fabrication, onetime activation and adjustment of the springs if necessary to correct minor transverse and vertical molar positions. This article reports a successful treatment method of class II malocclusion with pendulum appliance in mixed dentition phase. Distalization of maxillary molar was done, followed by guidance of canine impaction orthodontically and other dental correction using 0.022 MBT appliances. Posttreatment results were stable and remarkable. How to cite this article: Patil RU, Prakash A, Agarwal A. Pendulum Therapy of Molar Distalization in Mixed Dentition. Int J Clin Pediatr Dent 2016;9(1):67-73.

The Pendulum and the Calculus.

Science.gov (United States)

Sworder, Steven C.

A pair of experiments, appropriate for the lower division fourth semester calculus or differential equations course, are presented. The second order differential equation representing the equation of motion of a simple pendulum is derived. The period of oscillation for a particular pendulum can be predicted from the solution to this equation. As a…

School Foucault pendulum

International Nuclear Information System (INIS)

Lacsny, Boris; Štubna, Igor; Teleki, Aba

2014-01-01

A Foucault pendulum was assembled for a university/high-school physics course. The pendulum is 2.85 m long and the mass of the bob is 4.70 kg. A new technique based on the spark burned points on a sheet of paper was used to register the pendulum’s motion. A Ruhmkorff induction coil was used as a high-voltage source. Plots of the elliptical trajectories (except the first trajectory, which is a straight line) can be created and the angles between the major axes of the ellipses can be determined after assigning the coordinates to the burned points. (paper)

School Foucault pendulum

Science.gov (United States)

Lacsny, Boris; Štubna, Igor; Teleki, Aba

2014-11-01

A Foucault pendulum was assembled for a university/high-school physics course. The pendulum is 2.85 m long and the mass of the bob is 4.70 kg. A new technique based on the spark burned points on a sheet of paper was used to register the pendulum’s motion. A Ruhmkorff induction coil was used as a high-voltage source. Plots of the elliptical trajectories (except the first trajectory, which is a straight line) can be created and the angles between the major axes of the ellipses can be determined after assigning the coordinates to the burned points.

On the stochastic pendulum with Ornstein-Uhlenbeck noise

International Nuclear Information System (INIS)

Mallick, Kirone; Marcq, Philippe

2004-01-01

We study a frictionless pendulum subject to multiplicative random noise. Because of destructive interference between the angular displacement of the system and the noise term, the energy fluctuations are reduced when the noise has a non-zero correlation time. We derive the long time behaviour of the pendulum in the case of Ornstein-Uhlenbeck noise by a recursive adiabatic elimination procedure. An analytical expression for the asymptotic probability distribution function of the energy is obtained and the results agree with numerical simulations. Lastly, we compare our method with other approximation schemes

Search for stress dependence in the internal friction of fused silica

International Nuclear Information System (INIS)

Willems, Phil; Lamb, Corinne; Heptonstall, Alastair; Hough, Jim

2003-01-01

The quality factor (Q) of the vertical bounce mode of a fused silica fiber pendulum is measured at high and low stresses. The internal friction of fused silica fibers is found to be independent of stress from 12.8 to 213 MPa at a level of 1.6x10 -8 . Comparison with Q's of fiber bending modes is consistent with losses concentrated in the surface of the fiber

Noise and vibration in friction systems

CERN Document Server

Sergienko, Vladimir P

2015-01-01

The book analyzes the basic problems of oscillation processes and theoretical aspects of noise and vibration in friction systems. It presents generalized information available in literature data and results of the authors in vibroacoustics of friction joints, including car brakes and transmissions. The authors consider the main approaches to abatement of noise and vibration in non-stationary friction processes. Special attention is paid to materials science aspects, in particular to advanced composite materials used to improve the vibroacoustic characteristics of tribopairs The book is intended for researchers and technicians, students and post-graduates specializing in mechanical engineering, maintenance of machines and transport means, production certification, problems of friction and vibroacoustics.

Foucault pendulum with eddy-current damping of the elliptical motion

Science.gov (United States)

Mastner, G.; Vokurka, V.; Maschek, M.; Vogt, E.; Kaufmann, H. P.

1984-10-01

A newly designed Foucault pendulum is described in which the mechanical Charron ring, used throughout in previous designs for damping of the elliptical motion of the pendulum, is replaced by an electromagnetic eddy-current brake, consisting of a permanent magnet attached to the bottom of the bob and a metallic ring. This damping device is very efficient, as it is self-aligning, symmetrical in the damping effect, and never wears out. The permanent magnet is also used, together with a coil assembly and an electronic circuitry, for the dipole-torque drive of the pendulum as well as for accurate stabilization of the amplitude of the swing. A latched time display, controlled by Hall probes activated by the magnet, is used to visualize the Foucault rotation. The pendulum system and its associated electronic circuitry are described in detail. The optimizing of the drive mode is discussed. Measurements of deviations from theoretical value of the Foucault rotation velocity made automatically in a continuous run show a reproducible accuracy of ±1% or better in individual 360° rotations during the summer months. The quality factor of the pendulum as mechanical resonator was measured as a function of the amplitude in the presence of the eddy-current damping ring.

A comprehensive analytical solution of the nonlinear pendulum

International Nuclear Information System (INIS)

Ochs, Karlheinz

2011-01-01

In this paper, an analytical solution for the differential equation of the simple but nonlinear pendulum is derived. This solution is valid for any time and is not limited to any special initial instance or initial values. Moreover, this solution holds if the pendulum swings over or not. The method of approach is based on Jacobi elliptic functions and starts with the solution of a pendulum that swings over. Due to a meticulous sign correction term, this solution is also valid if the pendulum does not swing over.

Interactive Internet Based Pendulum for Learning Mechatronics

Science.gov (United States)

Sethson, Magnus R.

2003-01-01

This paper describes an Internet based remote experimental setup of a double lined pendulum mechanism for students experiments at the M. Sc. Level. Some of the first year experience using this web-based setup in classes is referred. In most of the courses given at the division of mechanical engineering systems at Linkoeping Institute of Technology we provide experimental setups to enhance the teaching Of M.Sc. students. Many of these experimental setups involve mechatronical systems. Disciplines like fluid power, electronics, and mechanics and also software technologies are used in each experiment. As our campus has recently been split into two different cities some new concepts for distance learning have been studied. The one described here tries to implement remotely controlled mechatronic setups for teaching basic programming of real-time operating systems and analysis of the dynamics of mechanical systems. The students control the regulators for the pendulum through a web interface and get measurement results and a movie back through their email. The present setup uses a double linked pendulum that is controlled by a DC-motor and monitored through both camera and angular position sensors. All software needed is hosted on a double-processor PC running the RedHat 7.1. distribution complemented with real-time scheduling using DIAPM-RTAI 1.7. The Internet site is presented to the students using PHP, Apache and MySQL. All of the used software originates from the open source domain. The experience from integrating these technologies and security issues is discussed together with the web-camera interface. One of the important experiences from this project so far is the need for a good visual feedback. This is both in terms of video speed but also in resolution. It has been noticed that when the students makes misstates and wants to search the failure they want clear, large images with high resolution to support their personal believes in the cause of the failure. Even

An internal-friction study of reactor-pressure-vessel steel embrittlement

International Nuclear Information System (INIS)

Ouytsel, K. van; Fabry, A.; Batist, R. de; Schaller, R.

1997-01-01

Within an enhanced commercial surveillance strategy, the nuclear-research institute SCK.CEN in Mol, Belgium is investigating, by means of internal friction, the microstructural processes responsible for embrittlement of pressure-vessel steels. The experiments were carried out using a torsion pendulum at the Ecole Polytechnique Federale de Lausanne in Switzerland. Amplitude-independent internal-friction experiments teach us that neutron irradiation induces defects which interact with mobile dislocations. Thermal ageing of JRQ and Doel-IV steel does not cause major embrittlement effects. Amplitude-dependent internal-friction experiments allow us to determine a critical amplitude which corresponds to the yield stress of the material as obtained from static tensile tests. The results also correspond to a three-component model for the yield strength taking into account both hardening and non-hardening embrittlement. Investigations of Doel-I-II weld material in different conditions reveal that embrittlement due to irradiation or thermal ageing can be interpreted in terms of a fine interplay between long- and short-range phenomena. (author)

Mathematical Modeling of a Moving Planar Payload Pendulum on Flexible Portal Framework

Directory of Open Access Journals (Sweden)

Edwar Yazid

2012-03-01

Full Text Available Mathematical modeling of a moving planar payload pendulum on elastic portal framework is presented in this paper. The equations of motion of such a system are obtained by modeling the portal frame using finite element in conjunction with moving finite element method and moving planar payload pendulum by using Lagrange’s equations. The generated equations indicate the presence of nonlinear coupling between dynamics of portal framework and the payload pendulum. The combinational direct numerical integration technique, namely Newmarkand fourth-order Runge-Kutta method, is then proposed to solve the coupled equations of motion. Several numerical simulations are performed and the results are verified with several benchmarks. The results indicate that the amplitude and frequency of the payload pendulum swing angle are greatly affected by flexibility of structure and the cable in term of carriage speed. 

[Determination of a Friction Coefficient for THA Bearing Couples].

Science.gov (United States)

Vrbka, M; Nečas, D; Bartošík, J; Hartl, M; Křupka, I; Galandáková, A; Gallo, J

2015-01-01

The wear of articular surfaces is considered one of the most important factors limiting the life of total hip arthroplasty (THA). It is assumed that the particles released from the surface of a softer material induce a complex inflammatory response, which will eventually result in osteolysis and aseptic loosening. Implant wear is related to a friction coefficient which depends on combination of the materials used, roughness of the articulating surfaces, internal clearance, and dimensions of the prosthesis. The selected parameters of the bearing couples tested were studied using an experimental device based on the principle of a pendulum. Bovine serum was used as a lubricant and the load corresponded to a human body mass of 75 kg. The friction coefficient was derived from a curve of slowdown of pendulum oscillations. Roughness was measured with a device working on the principle of interferometry. Clearance was assessed by measuring diameters of the acetabular and femoral heads with a 3D optical scanner. The specimens tested included unused metal-on-highly cross-linked polyethylene, ceramic-on-highly cross-linked polyethylene and ceramic-on-ceramic bearing couples with the diameters of 28 mm and 36 mm. For each measured parameter, an arithmetic mean was calculated from 10 measurements. 1) The roughness of polyethylene surfaces was higher by about one order of magnitude than the roughness of metal and ceramic components. The Protasul metal head had the least rough surface (0.003 μm). 2) The ceramic-on-ceramic couples had the lowest clearance. Bearing couples with polyethylene acetabular liners had markedly higher clearances ranging from 150 μm to 545 μm. A clearance increased with large femoral heads (up to 4-fold in one of the couple tested). 3) The friction coefficient was related to the combination of materials; it was lowest in ceramic-on-ceramic surfaces (0.11 to 0.12) and then in ceramic-on-polyethylene implants (0.13 to 0.14). The friction coefficient is

Two often disregarded aspects of Foucault's pendulum

International Nuclear Information System (INIS)

Pérez, José-Philippe; Pujol, Olivier

2015-01-01

This paper revisits the famous Foucault's pendulum by highlighting two often-disregarded aspects in mechanics courses. The first one concerns the existence of a local accelerated reference frame to express the law of dynamics without the Coriolis force. The second aspect deals with the geometrical phase that appears in pendulum dynamics. This last point, which could appear banal, should be related to analogous consideration in quantum physics. It is also linked to vectorial parallel transport of the pendulum angular momentum eigenvector. Numerical simulations with MATLAB are proposed. (paper)

Fuzzy modeling and control of rotary inverted pendulum system using LQR technique

International Nuclear Information System (INIS)

Fairus, M A; Mohamed, Z; Ahmad, M N

2013-01-01

Rotary inverted pendulum (RIP) system is a nonlinear, non-minimum phase, unstable and underactuated system. Controlling such system can be a challenge and is considered a benchmark in control theory problem. Prior to designing a controller, equations that represent the behaviour of the RIP system must be developed as accurately as possible without compromising the complexity of the equations. Through Takagi-Sugeno (T-S) fuzzy modeling technique, the nonlinear system model is then transformed into several local linear time-invariant models which are then blended together to reproduce, or approximate, the nonlinear system model within local region. A parallel distributed compensation (PDC) based fuzzy controller using linear quadratic regulator (LQR) technique is designed to control the RIP system. The results show that the designed controller able to balance the RIP system

A study on the determination of diffusion coefficient of carbon in 304 austenitic stainless steels by internal friction method

International Nuclear Information System (INIS)

Kim, K.S.; Kim, T.H.

1982-01-01

Internal friction peaks associated with the presence of carbon in 18-8 type 304 stainless steel have been observed from measurements with a torsion pendulum. The temperature for maximum internal friction lies between 250degC and 300degC with a frequency of vibration. The height of the peak rises and the position of the peak shifts to a lower temperature with an increase of the carbon content. And a comparison of the activation energy and the diffusion coefficient determined by internal friction methods with those measured in conventional macro-diffusion experiments reveals that the diffusion data measured by internal friction method and the diffusion data measured by conventional method exist in the same line. It follows from the above fact that observed internal friction peak is associated with the stress-induced diffusion of carbon in face-centered cubic alloys. (Author)

Simple pendulum for blind students

Science.gov (United States)

Goncalves, A. M. B.; Cena, C. R.; Alves, D. C. B.; Errobidart, N. C. G.; Jardim, M. I. A.; Queiros, W. P.

2017-09-01

Faced with the need to teach physics to the visually impaired, in this paper we propose a way to demonstrate the dependence of distance and time in a pendulum experiment to blind students. The periodic oscillation of the pendulum is translated, by an Arduino and an ultrasonic sensor, in a periodic variation of frequency in a speaker. The main advantage of this proposal is the possibility that a blind student understands the movement without necessity of touching it.

Development of Gravity Acceleration Measurement Using Simple Harmonic Motion Pendulum Method Based on Digital Technology and Photogate Sensor

Science.gov (United States)

Yulkifli; Afandi, Zurian; Yohandri

2018-04-01

Development of gravitation acceleration measurement using simple harmonic motion pendulum method, digital technology and photogate sensor has been done. Digital technology is more practical and optimizes the time of experimentation. The pendulum method is a method of calculating the acceleration of gravity using a solid ball that connected to a rope attached to a stative pole. The pendulum is swung at a small angle resulted a simple harmonic motion. The measurement system consists of a power supply, Photogate sensors, Arduino pro mini and seven segments. The Arduino pro mini receives digital data from the photogate sensor and processes the digital data into the timing data of the pendulum oscillation. The calculation result of the pendulum oscillation time is displayed on seven segments. Based on measured data, the accuracy and precision of the experiment system are 98.76% and 99.81%, respectively. Based on experiment data, the system can be operated in physics experiment especially in determination of the gravity acceleration.

Application of Firefly Algorithm for Parameter Estimation of Damped Compound Pendulum

Directory of Open Access Journals (Sweden)

Saad Mohd Sazli

2016-01-01

Full Text Available This paper presents an investigation into the parameter estimation of the damped compound pendulum using Firefly algorithm method. In estimating the damped compound pendulum, the system necessarily needs a good model. Therefore, the aim of the work described in this paper is to obtain a dynamic model of the damped compound pendulum. By considering a discrete time form for the system, an autoregressive with exogenous input (ARX model structures was selected. In order to collect input-output data from the experiment, the PRBS signal is used to be input signal to regulate the motor speed. Where, the output signal is taken from position sensor. Firefly algorithm (FA algorithm is used to estimate the model parameters based on model 2nd orders. The model validation was done by comparing the measured output against the predicted output in terms of the closeness of both outputs via mean square error (MSE value. The performance of FA is measured in terms of mean square error (MSE.

Damping Estimation of Friction Systems in Random Vibrations

DEFF Research Database (Denmark)

Friis, Tobias; Katsanos, Evangelos; Amador, Sandro

Friction is one of the most efficient and economical mechanisms to reduce vibrations in structural mechanics. However, the estimation of the equivalent linear damping of the friction damped systems in experimental modal analysis and operational modal analysis can be adversely affected by several...... assumptions regarding the definition of the linear damping and the identification methods or may be lacking a meaningful interpretation of the damping. Along these lines, this project focuses on assessing the potential to estimate efficiently the equivalent linear damping of friction systems in random...

Adaptation of a fuzzy controller’s scaling gains using genetic algorithms for balancing an inverted pendulum

Directory of Open Access Journals (Sweden)

Duka Adrian-Vasile

2011-12-01

Full Text Available This paper examines the development of a genetic adaptive fuzzy control system for the Inverted Pendulum. The inverted pendulum is a classical problem in Control Engineering, used for testing different control algorithms. The goal is to balance the inverted pendulum in the upright position by controlling the horizontal force applied to its cart. Because it is unstable and has a complicated nonlinear dynamics, the inverted pendulum is a good testbed for the development of nonconventional advanced control techniques. Fuzzy logic technique has been successfully applied to control this type of system, however most of the time the design of the fuzzy controller is done in an ad-hoc manner, and choosing certain parameters (controller gains, membership functions proves difficult. This paper examines the implementation of an adaptive control method based on genetic algorithms (GA, which can be used on-line to produce the adaptation of the fuzzy controller’s gains in order to achieve the stabilization of the pendulum. The performances of the proposed control algorithms are evaluated and shown by means of digital simulation.

[Evaluation of pendulum testing of spasticity].

Science.gov (United States)

Le Cavorzin, P; Hernot, X; Bartier, O; Carrault, G; Chagneau, F; Gallien, P; Allain, H; Rochcongar, P

2002-11-01

To identify valid measurements of spasticity derived from the pendulum test of the leg in a representative population of spastic patients. Pendulum testing was performed in 15 spastic and 10 matched healthy subjects. The reflex-mediated torque evoked in quadriceps femoris, as well as muscle mechanical parameters (viscosity and elasticity), were calculated using mathematical modelling. Correlation with the two main measures derived from the pendulum test reported in the literature (the Relaxation Index and the area under the curve) was calculated in order to select the most valid. Among mechanical parameters, only viscosity was found to be significantly higher in the spastic group. As expected, the computed integral of the reflex-mediated torque was found to be larger in spastics than in healthy subjects. A significant non-linear (logarithmic) correlation was found between the clinically-assessed muscle spasticity (Ashworth grading) and the computed reflex-mediated torque, emphasising the non-linear behaviour of this scale. Among measurements derived from the pendulum test which are proposed in the literature for routine estimation of spasticity, the Relaxation Index exhibited an unsuitable U-shaped pattern of variation with increasing reflex-mediated torque. On the opposite, the area under the curve revealed a linear regression, which is more convenient for routine estimation of spasticity. The pendulum test of the leg is a simple technique for the assessment of spastic hypertonia. However, the measurement generally used in the literature (the Relaxation Index) exhibits serious limitations, and would benefit to be replaced by more valid measures, such as the area under the goniometric curve, especially for the assessment of therapeutics.

Lateral position detection and control for friction stir systems

Science.gov (United States)

Fleming, Paul; Lammlein, David; Cook, George E.; Wilkes, Don Mitchell; Strauss, Alvin M.; Delapp, David; Hartman, Daniel A.

2010-12-14

A friction stir system for processing at least a first workpiece includes a spindle actuator coupled to a rotary tool comprising a rotating member for contacting and processing the first workpiece. A detection system is provided for obtaining information related to a lateral alignment of the rotating member. The detection system comprises at least one sensor for measuring a force experienced by the rotary tool or a parameter related to the force experienced by the rotary tool during processing, wherein the sensor provides sensor signals. A signal processing system is coupled to receive and analyze the sensor signals and determine a lateral alignment of the rotating member relative to a selected lateral position, a selected path, or a direction to decrease a lateral distance relative to the selected lateral position or selected path. In one embodiment, the friction stir system can be embodied as a closed loop tracking system, such as a robot-based tracked friction stir welding (FSW) or friction stir processing (FSP) system.

Parametric pendulum based wave energy converter

Science.gov (United States)

Yurchenko, Daniil; Alevras, Panagiotis

2018-01-01

The paper investigates the dynamics of a novel wave energy converter based on the parametrically excited pendulum. The herein developed concept of the parametric pendulum allows reducing the influence of the gravity force thereby significantly improving the device performance at a regular sea state, which could not be achieved in the earlier proposed original point-absorber design. The suggested design of a wave energy converter achieves a dominant rotational motion without any additional mechanisms, like a gearbox, or any active control involvement. Presented numerical results of deterministic and stochastic modeling clearly reflect the advantage of the proposed design. A set of experimental results confirms the numerical findings and validates the new design of a parametric pendulum based wave energy converter. Power harvesting potential of the novel device is also presented.

Precessional Periods of Long and Short Foucault Pendulums

Science.gov (United States)

Soga, Michitoshi

1978-01-01

Derives the precessional period of a Foucault pendulum without using small oscillation amplitudes. Shows that if the path of the pendulum passes through the origin, the periods for differing amplitudes are essentially the same. (GA)

Internal friction study of hydrides in zirconium at low hydrogen contents

International Nuclear Information System (INIS)

Peretti, H.A.; Corso, H.L.; Gonzalez, O.A.; Fernandez, L.; Ghilarducci, A.A.; Salva, H.R.

1999-01-01

Full text: Internal friction and shear modulus measurements were carried out on crystal bar zirconium in the as received and hydride conditions using an inverted forced pendulum. Hydriding was achieved in two ways: inside and out of the pendulum. The final hydrogen content determined by fusion analysis in the 'in situ' hydride sample was of 36 ppm. Another sample was hydride by the cathodic charge method with 25 ppm. The thermal solid solubility (TSS) phase boundary presents hysteresis between the precipitation (TSSP) and the dissolution (TSSD) temperatures for the zirconium hydrides. During the first thermal cycling the anelastic effects could be attributed to the δ, ε and metastable γ zirconium hydrides. After 'in situ' annealing at 490 K, these peaks completely disappear in the electrolytically charged sample, while in the 'in situ' hydride, the peaks remain with decreasing intensity. This effect can be understood in terms of the different surface conditions of the samples. (author)

Geometric singular perturbation analysis of systems with friction

DEFF Research Database (Denmark)

Bossolini, Elena

This thesis is concerned with the application of geometric singular perturbation theory to mechanical systems with friction. The mathematical background on geometric singular perturbation theory, on the blow-up method, on non-smooth dynamical systems and on regularization is presented. Thereafter......, two mechanical problems with two different formulations of the friction force are introduced and analysed. The first mechanical problem is a one-dimensional spring-block model describing earthquake faulting. The dynamics of earthquakes is naturally a multiple timescale problem: the timescale...... scales. The action of friction is generally explained as the loss and restoration of linkages between the surface asperities at the molecular scale. However, the consequences of friction are noticeable at much larger scales, like hundreds of kilometers. By using geometric singular perturbation theory...

Adaptive controller for regenerative and friction braking system

Science.gov (United States)

Davis, Roy I.

1990-01-01

A regenerative and friction braking system for a vehicle having one or more roadwheels driven by an electric traction motor includes a driver responsive device for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver and friction and regenerative brakes operatively connected with the roadwheels of the vehicle. A system according to this invention further includes control means for operating the friction and regenerative braking subsystems so that maximum brake torques sustainable by the roadwheels of the vehicle without skidding or slipping will not be exceeded.

Robotic system construction with mechatronic components inverted pendulum: humanoid robot

Science.gov (United States)

Sandru, Lucian Alexandru; Crainic, Marius Florin; Savu, Diana; Moldovan, Cristian; Dolga, Valer; Preitl, Stefan

2017-03-01

Mechatronics is a new methodology used to achieve an optimal design of an electromechanical product. This methodology is collection of practices, procedures and rules used by those who work in particular branch of knowledge or discipline. Education in mechatronics at the Polytechnic University Timisoara is organized on three levels: bachelor, master and PhD studies. These activities refer and to design the mechatronics systems. In this context the design, implementation and experimental study of a family of mechatronic demonstrator occupy an important place. In this paper, a variant for a mechatronic demonstrator based on the combination of the electrical and mechanical components is proposed. The demonstrator, named humanoid robot, is equivalent with an inverted pendulum. Is presented the analyze of components for associated functions of the humanoid robot. This type of development the mechatronic systems by the combination of hardware and software, offers the opportunity to build the optimal solutions.

Light rays and the tidal gravitational pendulum

Science.gov (United States)

Farley, A. N. St J.

2018-05-01

Null geodesic deviation in classical general relativity is expressed in terms of a scalar function, defined as the invariant magnitude of the connecting vector between neighbouring light rays in a null geodesic congruence projected onto a two-dimensional screen space orthogonal to the rays, where λ is an affine parameter along the rays. We demonstrate that η satisfies a harmonic oscillator-like equation with a λ-dependent frequency, which comprises terms accounting for local matter affecting the congruence and tidal gravitational effects from distant matter or gravitational waves passing through the congruence, represented by the amplitude, of a complex Weyl driving term. Oscillating solutions for η imply the presence of conjugate or focal points along the rays. A polarisation angle, is introduced comprising the orientation of the connecting vector on the screen space and the phase, of the Weyl driving term. Interpreting β as the polarisation of a gravitational wave encountering the light rays, we consider linearly polarised waves in the first instance. A highly non-linear, second-order ordinary differential equation, (the tidal pendulum equation), is then derived, so-called due to its analogy with the equation describing a non-linear, variable-length pendulum oscillating under gravity. The variable pendulum length is represented by the connecting vector magnitude, whilst the acceleration due to gravity in the familiar pendulum formulation is effectively replaced by . A tidal torque interpretation is also developed, where the torque is expressed as a coupling between the moment of inertia of the pendulum and the tidal gravitational field. Precessional effects are briefly discussed. A solution to the tidal pendulum equation in terms of familiar gravitational lensing variables is presented. The potential emergence of chaos in general relativity is discussed in the context of circularly, elliptically or randomly polarised gravitational waves encountering the null

Contact and friction in systems with fibre reinforced elastomers

NARCIS (Netherlands)

Rodriguez Pareja, Natalia Valentina

2012-01-01

The tribological behaviour (contact and friction) of systems that include fibre reinforced elastomers is studied in this thesis. The elastomer composite is considered to behave as a viscoelastic anisotropic continuum material. In the defined tribo-system, the most influential friction mechanism is

Oblique impact and friction of HMX and/or TATB-based PBXs

Science.gov (United States)

Picart, Didier; Junqua-Moullet, Alexandra

2017-06-01

Transportation, handling, vibrations can lead to moderate compressive but dynamic loadings requiring the characterization of the safety of PBXs submitted to such scenarios. Knowing that ignition can occur at a lower critical height during a fall on an inclined surface than a normal impact, the attention is focused in this paper on the heating due to the friction between PBXs and surfaces. A lot of experiments have been made using free-falling samples in vertical drop configurations on inclined targets or pendulum (skid) drop configurations (Green et al. 1971; Randolph et al. 1976). Data obtained on our HMX and/or TATB-based plastic-bonded explosives using pendulum drop configurations will be detailed. Evaluation of the heating due to friction requires the determination of the tangential projectile/target relative displacement and the contact pressure. The pressure is related to the normal force during the impact and the evolving contact surface, the latter being evaluated using a series of normal impacts. The aim of our paper is to compare the experimental diameter of the contact zones to (i) the classical Hertz's theory of contacting elastic solids and (ii) a spring-mass description of the impact. Data and models are then used to evaluate the increase of the temperature at the projectile/target interface for our explosives. We highlight the experimental bias which has already been attributed to the grits used to mimic the roughness of the surfaces.

Chaotic behaviour of an electrical analogue to the mechanical double pendulum

Directory of Open Access Journals (Sweden)

M. P. Hanias

2008-02-01

Full Text Available In this paper the analogy between a mechanical double pendulum and an oscillating electrical system is presented. Instead of using analytic equations, we used the MultiSim circuit simulation environment in order to reproduce and interpret the response of the electrical oscillator. The electrical double pendulum presents a chaotic regime which is studied quantita-tively by means of state space reconstruction. For this purpose the optimal delay time is calculated and the minimum em-bedding dimension is found with the method of False Nearest Neighbors.

Power Series Solution to the Pendulum Equation

Science.gov (United States)

Benacka, Jan

2009-01-01

This note gives a power series solution to the pendulum equation that enables to investigate the system in an analytical way only, i.e. to avoid numeric methods. A method of determining the number of the terms for getting a required relative error is presented that uses bigger and lesser geometric series. The solution is suitable for modelling the…

Sound Absorption and Friction Properties of Nano-Lotus Leaf Coated Concrete for Rigid Pavement

Directory of Open Access Journals (Sweden)

Marcelo GONZALEZ

2016-09-01

Full Text Available This paper presents the feasibility of superhydrophobic films to create the nano-lotus leaf effect on concrete surface and their influence on sound absorption and friction properties of concrete for application in rigid pavements. The study involved an evaluation of nanomaterials at the laboratory scale to analyze the effects of microtexture modification on the friction and sound absorption of concrete pavement. A number of laboratory specimens were produced by applying different amounts of nano-lotus leaf coating on the top of the textured concrete surface. The British pendulum test was used to measure the friction number, and an impedance tube was used to determine the sound absorption coefficient. Laboratory results indicate that nano-lotus leaf coated concrete can maintain the required friction property for rigid pavement, but may not increase the noise absorption. Further research must be carried out to determine possible benefit of the lotus leaf effect for reducing hydroplaning, particularly during heavy rainfall.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.7638

[Study of friction and loosening in hip endoprostheses].

Science.gov (United States)

Dovzak Bajs, Ivana; Cvjetko, Ivan; Car, Dolores; Kokić, Visnja

2002-01-01

Like any other operative procedure, the implantation of hip prosthesis is associated with certain complications, which diminishes the value and purpose of such a procedure. One of the complications in artificial hip implantation is loosening of the alloplastic material. Therefore, the aim of this study was to examine the effect of lubrication on the torsional moment and its role in the loosening of the femoral component, using an experimental mechanical model. The following hypothesis was tested: the magnitude of torsional loading in the "bone-endoprosthesis-bone cement system" is similar to any other known loading. The testing device was constructed with the possibility of simulation of positions similar to original performances in the implanted hip prosthesis. It refers primarily to the possibilities of achieving definite forces and velocities. The intention was to point quantitatively to the role of friction moment between the acetabular and femoral endoprosthesis part. Trials were conducted by combining 7 types of loading and 4 kinds of lubrication: dry, water, plasma, and light oil. The testing joint (Ring's prosthesis) was connected through tensometric measuring shaft upon the working forepart oscillating mechanism. Graded by the changeable static loading by means of the pendulum and via lever mechanism the testing joint was loaded by force from 610 to 7137 N. As the cause of friction resistance in the moving joint, torque deformaties of the measuring shaft occurred. The testing joint enabled oscillating movement using a four-part mechanism. In this way, it was possible to define not only the maximum values of the frictional moment (or the coefficient of friction) during one movement cycle but also to examine its relation to the kind of lubrication. Change in the measuring torsional moment were computer recorded. Before each trial, the gauging of the complete outfit was performed. Thereafter, cleaning of the frictional surfaces of the whole outfit was done

Sensing and actuation system for the University of Florida Torsion Pendulum for LISA

Science.gov (United States)

Chilton, Andrew; Shelley, Ryan; Olatunde, Taiwo; Ciani, Giacomo; Conklin, John; Mueller, Guido

2014-03-01

Space-based gravitational wave detectors like LISA are a necessity for understanding the low-frequency portion of the gravitational universe. They use test masses (TMs) which are separated by Gm and are in free fall inside their respective spacecraft. Their relative distance is monitored with laser interferometry at the pm/rtHz level in the LISA band, ranging from 0.1 to 100 mHz. Each TM is enclosed in a housing that provides isolation, capacitive sensing, and electrostatic actuation capabilities. The electronics must both be sensitive at the 1 nm/rtHz level and not induce residual acceleration noise above the requirement for LISA Pathfinder (3*10-15 m/sec2Hz1/2at 3 mHz). Testing and developing this technology is one of the roles of the University of Florida Torsion Pendulum, the only US testbed for LISA-like gravitational reference sensor technology. Our implementation of the sensing system functions by biasing our hollow LISA-like TMs with a 100 kHz sine wave and coupling a pair surrounding electrodes as capacitors to a pair of preamps and a differential amplifier; all other processing is done digitally. Here we report on the design of, implementation of, and preliminary results from the UF Torsion Pendulum.

Calculus migration characterization during Ho:YAG laser lithotripsy by high-speed camera using suspended pendulum method.

Science.gov (United States)

Zhang, Jian James; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Chia, Ray W J; Hasenberg, Thomas

2017-07-01

Calculus migration is a common problem during ureteroscopic laser lithotripsy procedure to treat urolithiasis. A conventional experimental method to characterize calculus migration utilized a hosting container (e.g., a "V" grove or a test tube). These methods, however, demonstrated large variation and poor detectability, possibly attributed to the friction between the calculus and the container on which the calculus was situated. In this study, calculus migration was investigated using a pendulum model suspended underwater to eliminate the aforementioned friction. A high-speed camera was used to study the movement of the calculus which covered zero order (displacement), first order (speed), and second order (acceleration). A commercialized, pulsed Ho:YAG laser at 2.1 μm, a 365-μm core diameter fiber, and a calculus phantom (Plaster of Paris, 10 × 10 × 10 mm 3 ) was utilized to mimic laser lithotripsy procedure. The phantom was hung on a stainless steel bar and irradiated by the laser at 0.5, 1.0, and 1.5 J energy per pulse at 10 Hz for 1 s (i.e., 5, 10, and 15 W). Movement of the phantom was recorded by a high-speed camera with a frame rate of 10,000 FPS. The video data files are analyzed by MATLAB program by processing each image frame and obtaining position data of the calculus. With a sample size of 10, the maximum displacement was 1.25 ± 0.10, 3.01 ± 0.52, and 4.37 ± 0.58 mm for 0.5, 1, and 1.5 J energy per pulse, respectively. Using the same laser power, the conventional method showed <0.5 mm total displacement. When reducing the phantom size to 5 × 5 × 5 mm 3 (one eighth in volume), the displacement was very inconsistent. The results suggested that using the pendulum model to eliminate the friction improved sensitivity and repeatability of the experiment. A detailed investigation on calculus movement and other causes of experimental variation will be conducted as a future study.

Stability of controlled inverted pendulum under permanent horizontal perturbations of the supporting point

Science.gov (United States)

Aleksandrov, V. V.; Reyes-Romero, M.; Sidorenko, G. Yu.; Temoltzi-Auila, R.

2010-04-01

We consider the problem of choosing a test perturbation of a movable foundation of a single-link inverted pendulum so as to test a vestibular prosthesis prototype located at the top of this pendulum in an extreme situation. The obtained results permit concluding that the information transmitted from otolithic organs of the human vestibular system to muscles of the locomotor apparatus is very important and improves the quality of stabilization of the human vertical posture preventing the possible fall.

Soup-Can Pendulum

Science.gov (United States)

Peters, Randall D.

2004-01-01

In these studies, a vegetable can containing fluid was swung as a pendulum by supporting its end-lips with a pair of knife edges. The motion was measured with a capacitive sensor and the logarithmic decrement in free decay was estimated from computer-collected records. Measurements performed with nine different homogeneous liquids, distributed…

The quantum pendulum

International Nuclear Information System (INIS)

Aldrovandi, R.; Ferreira, P.L.

1979-01-01

The problem of the mathematical pendulum is treated in its classical, semi-classical and quantum aspects. The Schroedinger equation of the problem is reduced to a Mathieu equation. The energy spectrum and eigenfunctions are discussed, with the requirement of single-valuedness imposed on them. Physical limiting cases are also discussed. (author) [pt

Balancing Inverted Pendulum by Angle Sensing Using Fuzzy Logic Supervised PID Controller Optimized by Genetic Algorithm

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Ashutosh K. AGARWAL

2011-10-01

Full Text Available Genetic algorithms are robust search techniques based on the principles of evolution. A genetic algorithm maintains a population of encoded solutions and guides the population towards the optimum solution. This important property of genetic algorithm is used in this paper to stabilize the Inverted pendulum system. This paper highlights the application and stability of inverted pendulum using PID controller with fuzzy logic genetic algorithm supervisor . There are a large number of well established search techniques in use within the information technology industry. We propose a method to control inverted pendulum steady state error and overshoot using genetic algorithm technique.

Robust hopping based on virtual pendulum posture control

International Nuclear Information System (INIS)

Sharbafi, Maziar A; Ahmadabadi, Majid Nili; Yazdanpanah, Mohammad J; Maufroy, Christophe; Seyfarth, Andre

2013-01-01

A new control approach to achieve robust hopping against perturbations in the sagittal plane is presented in this paper. In perturbed hopping, vertical body alignment has a significant role for stability. Our approach is based on the virtual pendulum concept, recently proposed, based on experimental findings in human and animal locomotion. In this concept, the ground reaction forces are pointed to a virtual support point, named virtual pivot point (VPP), during motion. This concept is employed in designing the controller to balance the trunk during the stance phase. New strategies for leg angle and length adjustment besides the virtual pendulum posture control are proposed as a unified controller. This method is investigated by applying it on an extension of the spring loaded inverted pendulum (SLIP) model. Trunk, leg mass and damping are added to the SLIP model in order to make the model more realistic. The stability is analyzed by Poincaré map analysis. With fixed VPP position, stability, disturbance rejection and moderate robustness are achieved, but with a low convergence speed. To improve the performance and attain higher robustness, an event-based control of the VPP position is introduced, using feedback of the system states at apexes. Discrete linear quartic regulator is used to design the feedback controller. Considerable enhancements with respect to stability, convergence speed and robustness against perturbations and parameter changes are achieved. (paper)

Orion Multi-Purpose Crew Vehicle Solving and Mitigating the Two Main Cluster Pendulum Problem

Science.gov (United States)

Ali, Yasmin; Sommer, Bruce; Troung, Tuan; Anderson, Brian; Madsen, Christopher

2017-01-01

The Orion Multi-purpose Crew Vehicle (MPCV) Orion spacecraft will return humans from beyond earth's orbit, including Mars and will be required to land 20,000 pounds of mass safely in the ocean. The parachute system nominally lands under 3 main parachutes, but the system is designed to be fault tolerant and land under 2 main parachutes. During several of the parachute development tests, it was observed that a pendulum, or swinging, motion could develop while the Crew Module (CM) was descending under two parachutes. This pendulum effect had not been previously predicted by modeling. Landing impact analysis showed that the landing loads would double in some places across the spacecraft. The CM structural design limits would be exceeded upon landing if this pendulum motion were to occur. The Orion descent and landing team was faced with potentially millions of dollars in structural modifications and a severe mass increase. A multidisciplinary team was formed to determine root cause, model the pendulum motion, study alternate canopy planforms and assess alternate operational vehicle controls & operations providing mitigation options resulting in a reliability level deemed safe for human spaceflight. The problem and solution is a balance of risk to a known solution versus a chance to improve the landing performance for the next human-rated spacecraft.

Coupled bending and torsional vibration of a rotor system with nonlinear friction

International Nuclear Information System (INIS)

Hua, Chunli; Cao, Guohua; Zhu, Zhencai; Rao, Zhushi; Ta, Na

2017-01-01

Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating ma- chinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose self- excited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.

Coupled bending and torsional vibration of a rotor system with nonlinear friction

Energy Technology Data Exchange (ETDEWEB)

Hua, Chunli; Cao, Guohua; Zhu, Zhencai [China University of Mining and Technology, Xuzhou (China); Rao, Zhushi; Ta, Na [Shanghai Jiao Tong University, Shanghai (China)

2017-06-15

Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating ma- chinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose self- excited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.

The impact of surface and geometry on coefficient of friction of artificial hip joints.

Science.gov (United States)

Choudhury, Dipankar; Vrbka, Martin; Mamat, Azuddin Bin; Stavness, Ian; Roy, Chanchal K; Mootanah, Rajshree; Krupka, Ivan

2017-08-01

Coefficient of friction (COF) tests were conducted on 28-mm and 36-mm-diameter hip joint prostheses for four different material combinations, with or without the presence of Ultra High Molecular Weight Polyethylene (UHMWPE) particles using a novel pendulum hip simulator. The effects of three micro dimpled arrays on femoral head against a polyethylene and a metallic cup were also investigated. Clearance played a vital role in the COF of ceramic on polyethylene and ceramic on ceramic artificial hip joints. Micro dimpled metallic femoral heads yielded higher COF against a polyethylene cup; however, with metal on metal prostheses the dimpled arrays significantly reduced the COF. In situ images revealed evidence that the dimple arrays enhanced film formation, which was the main mechanism that contributed to reduced friction. Copyright © 2017 Elsevier Ltd. All rights reserved.

The assessment of spasticity: Pendulum test based smart phone movie of passive markers

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Aleksić Antonina

2018-01-01

Full Text Available The pendulum test is the method for quantification of the level of spasticity in persons with spinal cord and brain injuries/diseases. The data for the assessment comes from the analysis of lower leg rotation in the sagittal plane while sitting caused by gravity. We built a simple instrument that uses the smart phone and passive markers for studying the pendulum movement of the leg. We compared the results of the new device with the results acquired with the conventional apparatus which uses a knee joint angle encoder and inertial sensors mounted on the upper and lower leg. The differences of parameters estimated from the test between the two systems are in the range of 5%, which is in the same range as the precision of the positioning of the pendulum apparatus on the leg. The new system is simple for the application (donning, doffing, setup time, accuracy, repeatability and allows a straightforward interpretation to a clinician. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 35003 and Grant no. III 44008

Mathematical modelling of the electrostatic pendulum in school and undergraduate education

International Nuclear Information System (INIS)

Forjan, Matej; Marhl, Marko; Grubelnik, Vladimir

2014-01-01

The electrostatic pendulum, also known as the electrostatic ping-pong, is an exciting experiment in school as well as in undergraduate education. We can easily demonstrate how the frequency of the electrostatic pendulum depends on the voltage across the capacitor. In this paper, we develop a simple mathematical model describing the dynamics of this experiment. In a step-wise manner, we introduce the external forces influencing the dynamics of the electrostatic pendulum. First, we take into account the electric force only. Then, we add air resistance and the non-elasticity of ball collisions with the capacitor plates. The model predictions show that the non-elastic collisions have greater effect on the pendulum dynamics than air resistance; in particular, this is true for higher frequencies of the pendulum. For lower frequencies, however, gravity is of crucial importance. The mathematical model is implemented in a graphic-oriented computer program, which gives the possibility of using this theoretical analysis also at the secondary school level. (paper)

Friction of elastomer-on-glass system and direct observation of its frictional interface

International Nuclear Information System (INIS)

Okamoto, Yoshihiro; Nishio, Kazuyuki; Sugiura, Jun-ichi; Hirano, Motohisa; Nitta, Takahiro

2007-01-01

We performed a study on the static friction of PDMS elastomers with well-defined surface topography sliding over glass. An experimental setup for simultaneous measurements of friction force and direct observations of frictional interface has been developed. The static friction force was nearly proportional to normal load. The static friction force was independent of stick time. The simultaneous measurements revealed that the static friction force was proportional to the total area of contact. The coefficient was nearly independent of the surface topography of PDMS elastomers

Container Shipping Network Efficiency Comparison in Indonesia: Nusantara Pendulum and Sea Tollway

Directory of Open Access Journals (Sweden)

Hafida Fahmiasari

2017-07-01

Full Text Available The disparity of the trading activities in Indonesia has triggered Indonesia Port Corporation to come up with the plan of Nusantara Pendulum, the future network of container shipping in Indonesia. The Sea Tollway plan is the modification of Nusantara Pendulum that is also envisioned by Indonesia President for Indonesia future backbone container plan. Both networks were designed to increase Indonesia container shipping flow from west to east and vice versa like a pendulum, thus results the reduced transport cost. This paper depicts the comparison of network efficiency analysis between these networks: Nusantara Pendulum, Sea Tollway, and the existing network. Two main methods that are used are Nagurney-Qiang and Jenelius-Peterson-Mattson. Mainly, these two methods use the efficiency calculation by considering parameters of demand (goods flow between each region and maritime transportation cost. It is concluded afterward that: 1 Sea Tollway is 8% more efficient than Nusantara Pendulum; 2 Sea Tollway and Nusantara Pendulum are ten times more efficient than current network; 3 Eastern ports in Indonesia (Bitung and Sorong urgently requisite a development.

Comparison of VP broadband tiltmeter and VS vertical pendulum tiltmeter

Directory of Open Access Journals (Sweden)

Wugang Ma

2015-05-01

Full Text Available Vertical pendulum (VP tiltmeter is a kind of earthquake precursor observation equipment, which is used to record the interaction force associated with astronomical tidal tilts caused. Currently, VP broadband tiltmeter and vertical sensor (VS vertical pendulum tiltmeter are primarily used. In this paper, we compare the two different instruments by using four aspects—mechanical structure, circuitry, zeroing, and bandwidth—based on their working principles and applications. We conclude that VP broadband tiltmeter is more superior compared with VS vertical pendulum tiltmeter because of its higher bandwidth and degree of automation.

Contribution to the study of internal friction in graphites

International Nuclear Information System (INIS)

Merlin, J.

1969-03-01

A study has been made of the internal friction in different graphites between -180 C and +500 C using a torsion pendulum; the graphites had been previously treated thermo-mechanically, by neutron irradiation and subjected to partial annealings. It has been shown that there occurs: a hysteretic type dissipation of energy, connected with interactions between dislocations and other defects in the matrix; a dissipation having a partially hysteretic character which can be interpreted by a Granato-Luke type formalism and which is connected with the presence of an 'ultra-micro porosity'; a dissipation by a relaxation mechanism after a small dose of irradiation; this is attributed to the reorientation of bi-interstitials; a dissipation having the characteristics of a solid state transformation, this during an annealing after irradiation. It is attributed to the reorganization of interstitial defects. Some information has thus been obtained concerning graphites, in particular: their behaviour at low mechanical stresses, the nature of irradiation defects and their behaviour during annealing, the structural changes occurring during graphitization, the relationship between internal friction and macroscopic mechanical properties. (author) [fr

Tissue Friendly Pendulum: Soft Liner to prevent Tissue Irritation

Directory of Open Access Journals (Sweden)

Siddharth Shashidhar Revankar

2014-01-01

Full Text Available Palatal mucosal irritation is commonly encountered with the Pendulum appliance. The efficiency of soft liners in reducing tissue irritation has been well documented in the field of prosthodontics. The following article describes an innovative technique where soft liner can be used to reduce palatal mucosal irritation caused by pendulum appliance.

The influences of load mass changing on inverted pendulum stability based on simulation study

Science.gov (United States)

Pangaribuan, Timbang; Nasruddin, M. N.; Marlianto, Eddy; Sigiro, Mula

2017-09-01

An inverted pendulum has nonlinear dynamic, so it is not easy to do in analysis to see its behavior. From many observations which have been made, there are two things that need to be added on the perfection of inverted pendulum. Firstly, when the pendulum has a large mass, and the second when the pendulum is given a load mass much larger than mass of the inverted pendulum. There are some question, first, how big the load mass can be given so that the movement of the inverted pendulum stay stable is. Second, how weight the changes and moves of load mass which can be given. For all the changes, it hopes the inverted pendulum is stay stable. Finally, the final result is still expected to be as stable, it must need conclude what kind of controller is capable of carrying such a mass burden, and how large the mass load limit can be given.

Simulating Dynamics of the System of Articulated Rigid Bodies with Joint Friction

Directory of Open Access Journals (Sweden)

M. V. Michaylyuk

2016-01-01

Full Text Available The subject of the work is to simulate dynamics of the system of articulated rigid bodies in the virtual environment complexes. The work aim is to develop algorithms and methods to simulate the multi-body system dynamics with joint friction to ensure all calculations in real time in line with visual realistic behavior of objects in a scene.The paper describes the multibody system based on a maximal set of coordinates, and to simulate the joint friction is used a Coulomb's law of dry friction. Joints are described using the holonomic constraints and their derivatives that specify the constraints on velocities of joined bodies. Based on The Coulomb’s law a correlation for the friction impulse values has been derived as an inequality. If the friction impulse performs a constraint that is a lack of relative motion of two joint-joined bodies, there is a static friction in the joint. Otherwise, there is a dynamic friction in the joint. Using a semi-implicit Euler method allows us to describe dynamics of articulated rigid bodies with joint friction as a system of linear algebraic equations and inequalities for the unknown velocities and impulse values.To solve the obtained system of equations and inequalities is used an iterative method of sequential impulses, which sequentially processes constraints for each joint with impulse calculation and its application to the joined bodies rather than considers the entire system. To improve the method convergence, at each iteration the calculated impulses are accumulated for their further using as an initial approximation at the next step of simulation.The proposed algorithms and methods have been implemented in the training complex dynamics subsystem, developed in SRISA RAS. Evaluation of these methods and algorithms has demonstrated their full adequacy to requirements for virtual environment systems and training complexes.

Characteristic Modeling and Control of Servo Systems with Backlash and Friction

Directory of Open Access Journals (Sweden)

Yifei Wu

2014-01-01

Full Text Available A novel approach for modeling and control of servo systems with backlash and friction is proposed based on the characteristic model. Firstly, to deal with friction-induced nonlinearities, a smooth Stribeck friction model is introduced. The backlash is modeled by a continuous and derivable mathematical function. Secondly, a characteristic model in the form of a second-order slowly time-varying difference equation is established and verified by simulations. Thirdly, a composite controller including the golden-section adaptive control law and the integral control law is designed and the stability of the closed-loop system is analyzed. The simulation and experimental results show that the proposed control scheme is effective and can improve the steady-state precision and the dynamic performance of the servo system with backlash and friction.

Ratchet baryogenesis and an analogy with the forced pendulum

Science.gov (United States)

Bamba, Kazuharu; Barrie, Neil D.; Sugamoto, Akio; Takeuchi, Tatsu; Yamashita, Kimiko

2018-06-01

A new scenario of baryogenesis via the ratchet mechanism is proposed based on an analogy with the forced pendulum. The oscillation of the inflaton field during the reheating epoch after inflation plays the role of the driving force, while the phase 𝜃 of a scalar baryon field (a complex scalar field with baryon number) plays the role of the angle of the pendulum. When the inflaton is coupled to the scalar baryon, the behavior of the phase 𝜃 can be analogous to that of the angle of the forced pendulum. If the oscillation of the driving force is adjusted to the pendulum’s motion, a directed rotation of the pendulum is obtained with a nonvanishing value of 𝜃˙, which models successful baryogenesis since 𝜃˙ is proportional to the baryon number density. Similar ratchet models which lead to directed motion have been used in the study of molecular motors in biology. There, the driving force is supplied by chemical reactions, while in our scenario this role is played by the inflaton during the reheating epoch.

An energy-optimal solution for transportation control of cranes with double pendulum dynamics: Design and experiments

Science.gov (United States)

Sun, Ning; Wu, Yiming; Chen, He; Fang, Yongchun

2018-03-01

Underactuated cranes play an important role in modern industry. Specifically, in most situations of practical applications, crane systems exhibit significant double pendulum characteristics, which makes the control problem quite challenging. Moreover, most existing planners/controllers obtained with standard methods/techniques for double pendulum cranes cannot minimize the energy consumption when fulfilling the transportation tasks. Therefore, from a practical perspective, this paper proposes an energy-optimal solution for transportation control of double pendulum cranes. By applying the presented approach, the transportation objective, including fast trolley positioning and swing elimination, is achieved with minimized energy consumption, and the residual oscillations are suppressed effectively with all the state constrains being satisfied during the entire transportation process. As far as we know, this is the first energy-optimal solution for transportation control of underactuated double pendulum cranes with various state and control constraints. Hardware experimental results are included to verify the effectiveness of the proposed approach, whose superior performance is reflected by being experimentally compared with some comparative controllers.

Friction of ceramic and metal hip hemi-endoprostheses against cadaveric acetabula.

Science.gov (United States)

Müller, L P; Degreif, J; Rudig, L; Mehler, D; Hely, H; Rommens, P M

2004-12-01

Studies of hip arthroplasty have dealt mainly with total endoprosthesis, while tribology measurement values of hemi-endoprosthetic implants are rare. The small amount of experimental tribological data concerning materials of hemi-endoprosthetic implants in the form of pendulum trials, animal experiments, in vivo measurements on human hip joints and pin on disc studies report friction coefficients between 0.014 and 0.57; the friction coefficients measured in fresh human cadaver hip joints were determined between 0.001 and 0.08. The HEPFlEx-hip simulator was constructed to test the friction coefficients of unipolar femur head hemi-endoprostheses made of metal or ceramic against fresh cadaveric acetabula. Its plane of movement is uniaxial with a flexion-extension movement of +30/-18 degrees . The force is produced pneumatically dynamic with amounts of 2.5 kN. Newborn calf serum serves as a lubricant. We mounted 20 fresh porcine acetabula and 10 fresh human cadaver acetabula in the HEPFlEx-hip simulator and compared the two unipolar femur head hemi-endoprostheses (metal vs. ceramic). The mean friction coefficients against porcine acetabula were micro=0.017-0.082 for ceramic and micro=0.020-0.101 for metal; against human cadaver acetabula micro=0.017-0.083 for ceramic and micro=0.019-0.118 for metal. The frictional coefficient deltas (metal-ceramic) values of all measurements were Deltamicro=0.004 for porcine acetabula and Deltamicro=0.001 for cadaver acetabula. Box-plots graphics document significantly lower frictional coefficients of the ceramics. The lower frictional coefficients of ceramic compared to metal against fresh cadaveric acetabula may have a clinical impact on the process of the protrusion of the corresponding femoral head through the acetabulum.

Effect of the spherical Earth on a simple pendulum

OpenAIRE

Burko, Lior M.

2003-01-01

We consider the period of a simple pendulum in the gravitational field of the spherical Earth. Effectively, gravity is enhanced compared with the often used flat Earth approximation, such that the period of the pendulum is shortened. We discuss the flat Earth approximation, and show when the corrections due to the spherical Earth may be of interest.

Implementation of Push Recovery Strategy Using Triple Linear Inverted Pendulum Model in “T-FloW” Humanoid Robot

Science.gov (United States)

Dimas Pristovani, R.; Raden Sanggar, D.; Dadet, Pramadihanto.

2018-04-01

Push recovery is one of humanbehaviorwhich is a strategy to defend the body from anexternal force in any environment. This paper describes push recovery strategy which usesMIMO decoupled control system method. The dynamics system uses aquasi-dynamic system based on triple linear inverted pendulum model (TLIPM). The analysis of TLIPMuses zero moment point (ZMP) calculation from ZMP simplification in last research. By using this simplification of dynamics system, the control design can be simplified into 3 serial SISOwith known and uncertain disturbance models in each inverted pendulum. Each pendulum has different plan to damp the external force effect. In this experiment, PID controller (closed- loop)is used to arrange the damp characteristic.The experiment result shows thatwhen using push recovery control strategy (closed-loop control) is about 85.71% whilewithout using push recovery control strategy (open-loop control) it is about 28.57%.

Note: A 1-m Foucault pendulum rolling on a ball

Science.gov (United States)

Salva, H. R.; Benavides, R. E.; Venturino, J. A.; Cuscueta, D. J.; Ghilarducci, A. A.

2013-10-01

We have built a short Foucault pendulum of 1-m length. The aim of this work was to increase the sensitivity to elliptical trajectories from other longer pendula. The design was a semi-rigid pendulum that rolls over a small ball. The measurements of the movements (azimuth and elliptical trajectory) were done by an optical method. The resulting pendulum works in a medium satisfactory way due to problems of the correct choice of the mass of the bob together with the diameter of the supporting ball. It is also important to keep the rolling surface very clean.

Chaotic behaviour of a pendulum with variable length

Energy Technology Data Exchange (ETDEWEB)

Bartuccelli, M; Christiansen, P L; Muto, V; Soerensen, M P; Pedersen, N F

1987-08-01

The Melnikov function for the prediction of Smale horseshoe chaos is applied to a driven damped pendulum with variable length. Depending on the parameters, it is shown that this dynamical system undertakes heteroclinic bifurcations which are the source of the unstable chaotic motion. The analytical results are illustrated by new numerical simulations. Furthermore, using the averaging theorem, the stability of the subharmonics is studied.

Internal friction in iron-aluminium alloys having a high aluminium content

International Nuclear Information System (INIS)

Hillairet, J.; Delaplace, J.; Silvent, A.

1966-01-01

By using a torsion pendulum to measure the internal friction of iron-aluminium alloys containing between 25 and 50 atom per cent of aluminium, it has been possible to show the existence of three damping peaks due to interstitial carbon. Their evolution is followed as a function of the carbon content, of the thermal treatment and of the aluminium content. A model based on the preferential occupation of tetrahedral sites is proposed as an interpretation of the results. A study of the Zener peak in these substitution alloys shows also that a part of the short distance disorder existing at high temperatures can be preserved by quenching. (author) [fr

Effect of friction on the slide guide in an elevator system

Energy Technology Data Exchange (ETDEWEB)

Zhang, X-g; Li, H-g; Meng, G [State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, Shanghai 200240 (China)], E-mail: xingang.zhang@gmail.com

2008-02-15

The slide guide in an elevator moves in contact against the guide rail. This kind of surface contact exhibits a highly non-linear hysteretic friction behaviour which hampers greatly the riding quality of the elevator system. This paper presents an experimental investigation on this type of phenomenon through measuring the contact friction force between the interface of the slide guide and the rail under different combination of input parameters. The experiment shows frictional behaviours including pre-sliding/gross-sliding regimes, transition behaviour between them, time lag, and velocity (weakening and strengthening) dependence. In addition, it is found that different materials in contact, lubrications and friction duration have strong impacts on evaluation of the friction characteristics. The observations in the test provide an insight into relationships between different friction behaviours and can be used to validate the appropriate theoretical friction models.

Determination of the Optimal Position of Pendulums of an Active Self-balancing Device

Science.gov (United States)

Ziyakaev, G. R.; Kazakova, O. A.; Yankov, V. V.; Ivkina, O. P.

2017-04-01

The demand of the modern manufacturing industry for machines with high motion speed leads to increased load and vibration activity of the main elements of rotor systems. Vibration reduces operating life of bearings, has adversary effects on human organism, and can cause accidents. One way to compensate for a rotating rotor's imbalance is the use of active self-balancing devices. The aim of this work is to determine the position of their pendulums, in which the imbalance is minimized. As a result of the study, a formula for determining the angle of the pendulums was obtained.

Interval type-2 fuzzy PID controller for uncertain nonlinear inverted pendulum system.

Science.gov (United States)

El-Bardini, Mohammad; El-Nagar, Ahmad M

2014-05-01

In this paper, the interval type-2 fuzzy proportional-integral-derivative controller (IT2F-PID) is proposed for controlling an inverted pendulum on a cart system with an uncertain model. The proposed controller is designed using a new method of type-reduction that we have proposed, which is called the simplified type-reduction method. The proposed IT2F-PID controller is able to handle the effect of structure uncertainties due to the structure of the interval type-2 fuzzy logic system (IT2-FLS). The results of the proposed IT2F-PID controller using a new method of type-reduction are compared with the other proposed IT2F-PID controller using the uncertainty bound method and the type-1 fuzzy PID controller (T1F-PID). The simulation and practical results show that the performance of the proposed controller is significantly improved compared with the T1F-PID controller. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Multi-directional energy harvesting by piezoelectric cantilever-pendulum with internal resonance

Energy Technology Data Exchange (ETDEWEB)

Xu, J.; Tang, J., E-mail: jtang@engr.uconn.edu [Department of Mechanical Engineering, The University of Connecticut, Storrs, Connecticut 06269 (United States)

2015-11-23

This letter reports a piezoelectric cantilever-pendulum design for multi-directional energy harvesting. A pendulum is attached to the tip of a piezoelectric cantilever-type energy harvester. This design aims at taking advantage of the nonlinear coupling between the pendulum motion in 3-dimensional space and the beam bending vibration at resonances. Experimental studies indicate that, under properly chosen parameters, 1:2 internal resonance can be induced, which enables the multi-directional energy harvesting with a single cantilever. The advantages of the design with respect to traditional piezoelectric cantilever are examined.

Multi-directional energy harvesting by piezoelectric cantilever-pendulum with internal resonance

International Nuclear Information System (INIS)

Xu, J.; Tang, J.

2015-01-01

This letter reports a piezoelectric cantilever-pendulum design for multi-directional energy harvesting. A pendulum is attached to the tip of a piezoelectric cantilever-type energy harvester. This design aims at taking advantage of the nonlinear coupling between the pendulum motion in 3-dimensional space and the beam bending vibration at resonances. Experimental studies indicate that, under properly chosen parameters, 1:2 internal resonance can be induced, which enables the multi-directional energy harvesting with a single cantilever. The advantages of the design with respect to traditional piezoelectric cantilever are examined

Global control of reaction wheel pendulum through energy regulation and extended linearization of the state variables

Directory of Open Access Journals (Sweden)

Oscar D. Montoya-Giraldo

2014-01-01

Full Text Available This paper presents the design and simulation of a global controller for the Reaction Wheel Pendulum system using energy regulation and extended linearization methods for the state feedback. The proposed energy regulation is based on the gradual reduction of the energy of the system to reach the unstable equilibrium point. The signal input for this task is obtained from the Lyapunov stability theory. The extended state feedback controller design is used to get a smooth nonlinear function that extends the region of operation to a bigger range, in contrast with the static linear state feedback obtained through the method of approximate linearization around an operating point. The general designed controller operates with a switching between the two control signals depending upon the region of operation; perturbations are applied in the control signal and the (simulated measured variables to verify the robustness and efficiency of the controller. Finally, simulations and tests using the model of the reaction wheel pendulum system, allow to observe the versatility and functionality of the proposed controller in the entire operation region of the pendulum.

Idealisation and Galileo's Pendulum Discoveries: Historical, Philosophical and Pedagogical Considerations

Science.gov (United States)

Matthews, Michael R.

2004-01-01

Galileo's discovery of the properties of pendulum motion depended on his adoption of the novel methodology of idealisation. Galileo's laws of pendulum motion could not be accepted until the empiricist methodological constraints placed on science by Aristotle, and by common sense, were overturned. As long as scientific claims were judged by how the…

Nonlinear analysis of r.c. framed buildings retrofitted with elastomeric and friction bearings under near-fault earthquakes

Science.gov (United States)

Mazza, Mirko

2015-12-01

Reinforced concrete (r.c.) framed buildings designed in compliance with inadequate seismic classifications and code provisions present in many cases a high vulnerability and need to be retrofitted. To this end, the insertion of a base isolation system allows a considerable reduction of the seismic loads transmitted to the superstructure. However, strong near-fault ground motions, which are characterised by long-duration horizontal pulses, may amplify the inelastic response of the superstructure and induce a failure of the isolation system. The above considerations point out the importance of checking the effectiveness of different isolation systems for retrofitting a r.c. framed structure. For this purpose, a numerical investigation is carried out with reference to a six-storey r.c. framed building, which, primarily designed (as to be a fixed-base one) in compliance with the previous Italian code (DM96) for a medium-risk seismic zone, has to be retrofitted by insertion of an isolation system at the base for attaining performance levels imposed by the current Italian code (NTC08) in a high-risk seismic zone. Besides the (fixed-base) original structure, three cases of base isolation are studied: elastomeric bearings acting alone (e.g. HDLRBs); in-parallel combination of elastomeric and friction bearings (e.g. high-damping-laminated-rubber bearings, HDLRBs and steel-PTFE sliding bearings, SBs); friction bearings acting alone (e.g. friction pendulum bearings, FPBs). The nonlinear analysis of the fixed-base and base-isolated structures subjected to horizontal components of near-fault ground motions is performed for checking plastic conditions at the potential critical (end) sections of the girders and columns as well as critical conditions of the isolation systems. Unexpected high values of ductility demand are highlighted at the lower floors of all base-isolated structures, while re-centring problems of the base isolation systems under near-fault earthquakes are

Analysis of balance control methods based on inverted pendulum for legged robots

OpenAIRE

Denisov, A.; Iakovlev, R.; Mamaev, I.; Pavliuk, N.

2017-01-01

Methods of balance control for a legged robot, the model of which is presented as a two-section inverted pendulum, are considered. The following balance methods for humanoid robots are analysed: the parallel algorithm of the network operator method; the method of natural synergies; the method of fuzzy control, the spherical inverted pendulum mode, a dual length linear inverted pendulum method. The best of these methods will be used in the development of the Russian anthropomorphic robot Antares.

Mode competition in a system of two parametrically driven pendulums with nonlinear coupling

NARCIS (Netherlands)

Banning, E.J.; Banning, E.J.; van der Weele, J.P.; Ross, J.C.; Kettenis, M.M.

1997-01-01

This paper is part three in a series on the dynamics of two coupled, parametrically driven pendulums. In the previous parts Banning and van der Weele (1995) and Banning et al. (1997) studied the case of linear coupling; the present paper deals with the changes brought on by the inclusion of a

Dynamic Analysis of a Pendulum Dynamic Automatic Balancer

Directory of Open Access Journals (Sweden)

Jin-Seung Sohn

2007-01-01

Full Text Available The automatic dynamic balancer is a device to reduce the vibration from unbalanced mass of rotors. Instead of considering prevailing ball automatic dynamic balancer, pendulum automatic dynamic balancer is analyzed. For the analysis of dynamic stability and behavior, the nonlinear equations of motion for a system are derived with respect to polar coordinates by the Lagrange's equations. The perturbation method is applied to investigate the dynamic behavior of the system around the equilibrium position. Based on the linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue analysis.

Inverted pendulum as low-frequency pre-isolation for advanced gravitational wave detectors

International Nuclear Information System (INIS)

Takamori, A.; Raffai, P.; Marka, S.; DeSalvo, R.; Sannibale, V.; Tariq, H.; Bertolini, A.; Cella, G.; Viboud, N.; Numata, K.; Takahashi, R.; Fukushima, M.

2007-01-01

We have developed advanced seismic attenuation systems for Gravitational Wave (GW) detectors. The design consists of an Inverted Pendulum (IP) holding stages of Geometrical Anti-Spring Filters (GASF) and pendula, which isolate the test mass suspension from ground noise. The ultra-low-frequency IP suppresses the horizontal seismic noise, while the GASF suppresses the vertical ground vibrations. The three legs of the IP are supported by cylindrical maraging steel flexural joints. The IP can be tuned to very low frequencies by carefully adjusting its load. As a best result, we have achieved an ultra low, ∼12 mHz pendulum frequency for the system prototype made for Advanced LIGO (Laser Interferometer Gravitational Wave Observatory). The measured quality factor, Q, of this IP, ranging from Q∼2500 (at 0.45 Hz) to Q∼2 (at 12 mHz), is compatible with structural damping, and is proportional to the square of the pendulum frequency. Tunable counterweights allow for precise center-of-percussion tuning to achieve the required attenuation up to the first leg internal resonance (∼60 Hz for advanced LIGO prototype). All measurements are in good agreement with our analytical models. We therefore expect good attenuation in the low-frequency region, from ∼0.1to ∼50 Hz, covering the micro-seismic peak. The extremely soft IP requires minimal control force, which simplifies any needed actuation

Non-integrability of the generalized spring-pendulum problem

International Nuclear Information System (INIS)

Maciejewski, Andrzej J; Przybylska, Maria; Weil, Jacques-Arthur

2004-01-01

We investigate a generalization of the three-dimensional spring-pendulum system. The problem depends on two real parameters (k, a), where k is the Young modulus of the spring and a describes the nonlinearity of elastic forces. We show that this system is not integrable when k ≠ -a. We carefully investigated the case k = -a when the necessary condition for integrability given by the Morales-Ruiz-Ramis theory is satisfied. We discuss an application of the higher order variational equations for proving the non-integrability in this case

A simple method to measure the trajectory of a spherical pendulum

Energy Technology Data Exchange (ETDEWEB)

Yang Hujiang; Xiao Jinghua; Yang Tianyu; Qiu Chen, E-mail: jhxiao@bupt.edu.cn [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

2011-07-15

Compared with a single gravity pendulum, the spherical pendulum behaves more complicatedly in experiments, which makes it difficult to measure. In this paper, we present a method to visualize the trajectories of a spherical pendulum by employing a gravity ball with a lit LED and a digital camera. This new measurement is inexpensive and easy to use. We analyse the experimental results with the help of analytical mechanics, and give the numerical simulation for better understanding. The experiment is carried out in our physics undergraduate laboratory. Through the experiment, we can improve students' existing knowledge and evoke their creativity.

Analysis of balance control methods based on inverted pendulum for legged robots

Directory of Open Access Journals (Sweden)

Denisov Alexander

2017-01-01

Full Text Available Methods of balance control for a legged robot, the model of which is presented as a two-section inverted pendulum, are considered. The following balance methods for humanoid robots are analysed: the parallel algorithm of the network operator method; the method of natural synergies; the method of fuzzy control, the spherical inverted pendulum mode, a dual length linear inverted pendulum method. The best of these methods will be used in the development of the Russian anthropomorphic robot Antares.

The electromagnetic impulse pendulum and momentum conservation

International Nuclear Information System (INIS)

Graneau, P.; Graneau, P.N.

1986-01-01

Largely quantitative experiments by Pappas have indicated that the momentum imparted to an electrodynamic impulse pendulum was not balanced by an equal and opposite momentum change of field energy as required by the special theory of relativity. The authors repeated Pappas' experiment using discharge currents from a capacitor bank which contained a known amount of stored energy. It turned out that, for momentum conservation, the magnetic-field energy required would have been 1000 to 2000 times as large as the energy that was actually stored in the capacitors. In the second part of the paper the pendulum experiments are interpreted in terms of Ampere's force law

Spherical Pendulum, Actions, and Spin

NARCIS (Netherlands)

Richter, Peter H.; Dullin, Holger R.; Waalkens, Holger; Wiersig, Jan

1996-01-01

The classical and quantum mechanics of a spherical pendulum are worked out, including the dynamics of a suspending frame with moment of inertia θ. The presence of two separatrices in the bifurcation diagram of the energy-momentum mapping has its mathematical expression in the hyperelliptic nature of

Effective equations for the quantum pendulum from momentous quantum mechanics

Energy Technology Data Exchange (ETDEWEB)

Hernandez, Hector H.; Chacon-Acosta, Guillermo [Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120 (Mexico)

2012-08-24

In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

Missile rolling tail brake torque system. [simulating bearing friction on canard controlled missiles

Science.gov (United States)

Davis, W. T. (Inventor)

1984-01-01

Apparatus for simulating varying levels of friction in the bearings of a free rolling tail afterbody on a canard-controlled missile to determine friction effects on aerodynamic control characteristics is described. A ring located between the missile body and the afterbody is utilized in a servo system to create varying levels of friction between the missile body and the afterbody to simulate bearing friction.

Monodromy in the quantum spherical pendulum

International Nuclear Information System (INIS)

Guillemin, V.; Uribe, A.

1989-01-01

In this article we show that monodromy in the quantum spherical pendulum can be interpreted as a Maslov effect: i.e. as multi-valuedness of a certain generating function of the quantum energy levels. (orig.)

Friction behavior of self-ligating and conventional brackets with different ligature systems.

Science.gov (United States)

Szczupakowski, Alexandra; Reimann, Susanne; Dirk, Cornelius; Keilig, Ludger; Weber, Anna; Jäger, Andreas; Bourauel, Christoph

2016-07-01

Self-ligating brackets are widely believed to offer better clinical efficiency and, in particular, less friction. Thus, the goal of this in vitro investigation was to assess the friction behavior of different bracket/archwire/ligature combinations during simulated canine retraction. An important aspect of this work was to determine whether conventional bracket systems behave differently in passive or active self-ligating brackets used with a Slide™ ligature, an elastic ligature, or a steel ligature. Three conventional (Contour, Class One; Discovery(®), Dentaurum; Mystique MB, GAC) and six self-ligating (Carriere SL, Class One; Clarity™ SL, 3M Unitek; Damon3, Ormco; In-Ovation(®) C, GAC; Speed Appliance, Speed System™; QuicKlear(®), Forestadent(®)) bracket systems were analyzed. All brackets featured a 0.022″ slot (0.56 mm). Each conventional system was tested with a steel ligature (0.25 mm; Remanium(®), Dentaurum), an elastic ligature (1.3 mm in diameter; Dentalastics, Dentaurum), and a modified elastic ligature (Slide™; Leone(®)). Each combination was used with four archwires, including rectangular stainless steel (0.46 × 0.64 mm, 0.018 × 0.025″, Dentaurum), rectangular nickel-titanium with Teflon coating (0.46 × 0.64 mm, 0.018 × 0.025″, Forestadent(®)), round coaxial nickel-titanium (0.46 mm, 0.018″, Speed), and half-round/half-square (D-profile) stainless steel (0.46 mm, 0.018″, Speed). In the orthodontic measurement and simulation system (OMSS), retraction of a canine was simulated on a Frasaco model replicated in resin. Based on the force systems, the respective friction values were determined. For each combination of materials, five brackets of the same type were tested and five single measurements performed. Friction values were found to vary distinctly with the different combinations, modifiers being the ligature systems and the archwire types. Any significant friction differences between the steel-ligated, Slide�

The anisosphere as a new tool for interpreting Foucault pendulum experiments. Part I: harmonic oscillators

Science.gov (United States)

Verreault, René

2017-08-01

In an attempt to explain the tendency of Foucault pendula to develop elliptical orbits, Kamerlingh Onnes derived equations of motion that suggest the use of great circles on a spherical surface as a graphical illustration for an anisotropic bi-dimensional harmonic oscillator, although he did not himself exploit the idea any further. The concept of anisosphere is introduced in this work as a new means of interpreting pendulum motion. It can be generalized to the case of any two-dimensional (2-D) oscillating system, linear or nonlinear, including the case where coupling between the 2 degrees of freedom is present. Earlier pendulum experiments in the literature are revisited and reanalyzed as a test for the anisosphere approach. While that graphical method can be applied to strongly nonlinear cases with great simplicity, this part I is illustrated through a revisit of Kamerlingh Onnes' dissertation, where a high performance pendulum skillfully emulates a 2-D harmonic oscillator. Anisotropy due to damping is also described. A novel experiment strategy based on the anisosphere approach is proposed. Finally, recent original results with a long pendulum using an electronic recording alidade are presented. A gain in precision over traditional methods by 2-3 orders of magnitude is achieved.

Research on the reliability of friction system under combined additive and multiplicative random excitations

Science.gov (United States)

Sun, Jiaojiao; Xu, Wei; Lin, Zifei

2018-01-01

In this paper, the reliability of a non-linearly damped friction oscillator under combined additive and multiplicative Gaussian white noise excitations is investigated. The stochastic averaging method, which is usually applied to the research of smooth system, has been extended to the study of the reliability of non-smooth friction system. The results indicate that the reliability of friction system can be improved by Coulomb friction and reduced by random excitations. In particular, the effect of the external random excitation on the reliability is larger than the effect of the parametric random excitation. The validity of the analytical results is verified by the numerical results.

Einstein versus the Simple Pendulum Formula: Does Gravity Slow All Clocks?

Science.gov (United States)

Puri, Avinash

2015-01-01

According to the Newtonian formula for a simple pendulum, the period of a pendulum is inversely proportional to the square root of "g", the gravitational field strength. Einstein's theory of general relativity leads to the result that time slows down where gravity is intense. The two claims look contradictory and can muddle student and…

An Apparatus to Demonstrate Linear and Nonlinear Oscillations of a Pendulum

Science.gov (United States)

Mayer, V. V.; Varaksina, E. I.

2016-01-01

A physical pendulum with a magnetic load is proposed for comparison of linear and nonlinear oscillations. The magnetic load is repelled by permanent magnets which are disposed symmetrically relative to the load. It is established that positions of the pendulum and the magnets determine the dependence of restoring force on displacement of the load.…

Comparison of VP broadband tiltmeter and VS vertical pendulum tiltmeter

OpenAIRE

Ma, Wugang; Wu, Yanxia; Zhao, Huiqin

2015-01-01

Vertical pendulum (VP) tiltmeter is a kind of earthquake precursor observation equipment, which is used to record the interaction force associated with astronomical tidal tilts caused. Currently, VP broadband tiltmeter and vertical sensor (VS) vertical pendulum tiltmeter are primarily used. In this paper, we compare the two different instruments by using four aspects—mechanical structure, circuitry, zeroing, and bandwidth—based on their working principles and applications. We conclude that VP...

Analysis and simulation of centrifugal pendulum vibration absorbers

OpenAIRE

Smith, Emma

2015-01-01

When environmental laws are constricted and downsizing of engines has become the reality of the vehicle industry, there needs to be a solution for the rise in torsion vibrations in the drivetrain. These increased levels of torsion vibrations are mostly due to excitations from the firing pulses, which in turn have become increased due to higher cylinder pressures. One of the solutions for further dampening the system is to add a centrifugal pendulum absorber to the flywheel, and predicting the...

Frictional coefficient depending on active friction radius with BPV ...

African Journals Online (AJOL)

Frictional coefficient depending on active friction radius with BPV and BTV in automobile disc braking system. ... International Journal of Engineering, Science and Technology. Journal Home · ABOUT ... AJOL African Journals Online. HOW TO ...

Period of an Interrupted Pendulum

Science.gov (United States)

Miller, Bradley E.

2002-11-01

While demonstrating a classic conservation-of-energy problem to my AP Physics students, I became curious about the periodic motion that ensued for certain initial conditions. The original problem consists of releasing a mass at the end of a string from an initial position horizontal to the plane of a table. The string comes in contact with a peg some distance below the point where the string is attached at the top. One is asked to find what minimum fraction of the string's length should the peg be placed to have the mass complete a circle about the peg. However, when the mass is released from much lower heights, the system undergoes periodic motion that can be thought of as an interrupted pendulum.

The Bravais Pendulum: The Distinct Charm of an Almost Forgotten Experiment

Science.gov (United States)

Babovic, V. M.; Mekic, S.

2011-01-01

In the year 1851 in Paris, the apparent change of the plane of oscillation of a linear pendulum was observed by Leon Foucault. In the same year, at the same place, the unequal duration of the oscillations of a right- and left-handed conical pendulum was observed by Bravais. Today, the Foucault pendula are common at universities, the Bravais…

Reduced friction in engine sealing system for truck engines; Reibungsreduzierende Motorabdichtung bei Nutzfahrzeugmotoren

Energy Technology Data Exchange (ETDEWEB)

Reichert, Joachim [Kaco GmbH und Co. KG, Heilbronn (Germany). RADIA-Dichtsysteme; Schaefer, Peter [Kaco GmbH und Co. KG, Heilbronn (Germany). Nutzfahrzeuganwendungen

2010-04-15

The mechanical efficiency of the drive unit components, e.g. the prevention of friction loss, becomes more the focus point of many new developments in engines and drive trains. Radia rotary shaft seal rings as commonly used in utility vehicles cause an accordingly high friction, particularly when in big dimensions. Kaco has engineered a tailor made design of state of the art friction reducing sealing system generation called Fred. In the acronym ''F'' stands for friction and ''red'' stands for reduced. Kaco has defined three focus points of the performance profile from the already established Fred sealing system generation for further engineering when applied in utility vehicles. (orig.)

Pendulum Motion and Differential Equations

Science.gov (United States)

Reid, Thomas F.; King, Stephen C.

2009-01-01

A common example of real-world motion that can be modeled by a differential equation, and one easily understood by the student, is the simple pendulum. Simplifying assumptions are necessary for closed-form solutions to exist, and frequently there is little discussion of the impact if those assumptions are not met. This article presents a…

Effects of springs on a pendulum electromechanical energy harvester

OpenAIRE

Arnaud Notué Kadjie; Paul Woafo

2014-01-01

This paper studies a model of energy harvester that consists of an electromechanical pendulum system subjected to nonlinear springs. The output power is analyzed in terms of the intrinsic parameters of the device leading to optimal parameters for energy harvesting. It is found that in an appropriate range of the springs constant, the power attains higher values as compared to the case without springs. The dynamical behavior of the device shows transition to chaos.

Identification and compensation of friction for a novel two-axis differential micro-feed system

Science.gov (United States)

Du, Fuxin; Zhang, Mingyang; Wang, Zhaoguo; Yu, Chen; Feng, Xianying; Li, Peigang

2018-06-01

Non-linear friction in a conventional drive feed system (CDFS) feeding at low speed is one of the main factors that lead to the complexity of the feed drive. The CDFS will inevitably enter or approach a non-linear creeping work area at extremely low speed. A novel two-axis differential micro-feed system (TDMS) is developed in this paper to overcome the accuracy limitation of CDFS. A dynamic model of TDMS is first established. Then, a novel all-component friction parameter identification method (ACFPIM) using a genetic algorithm (GA) to identify the friction parameters of a TDMS is introduced. The friction parameters of the ball screw and linear motion guides are identified independently using the method, assuring the accurate modelling of friction force at all components. A proportional-derivate feed drive position controller with an observer-based friction compensator is implemented to achieve an accurate trajectory tracking performance. Finally, comparative experiments demonstrate the effectiveness of the TDMS in inhibiting the disadvantageous influence of non-linear friction and the validity of the proposed identification method for TDMS.

Dose distributions of pendulum fields in the field border plane

International Nuclear Information System (INIS)

Schrader, R.

1986-01-01

Calculations (program SIDOS-U2) and LiF measurements taken in a cylindric water phantom are used to investigate the isodose distributions of different pendulum irradiation methods (Co-60) in a plane which is parallel to the central ray plane and crosses the field borders at the depth of the axis. The dose values compared to the maximum values of the central ray plane are completely different for each pendulum method. In case of monoaxial pendulum methods around small angles, the maximum dose value found in the border plane is less than 50% of the dose in the central ray plane. The relative maximum of the border plane moves to tissues laying in a greater depth. In case of bi-axial methods, the maximum value of the border plane can be much more than 50% of the maximum dose measured in the central ray plane. (orig.) [de

On the formation of limit cycle of the friction-induced stick-slip vibration in oilwell drillstring

Directory of Open Access Journals (Sweden)

Xiaohua Zhu

2015-03-01

Full Text Available In this paper, the stick-slip vibration in oilwell drillstring is studied. The drilling system is modelled as a lumped-parameter torsional pendulum and the interaction between the drill bit and the rock is treated as Coulomb friction. Equation of motion of the drill bit is established and the dynamic responses of the drill bit are obtained. A drilling system with the drillstring length 3000 m is analysed, in which the system parameters are selected by reference to the actual drilling situation. After the slip vibrations in the initial stage, final state of the drill bit is a stable stick-slip vibration of which the limit cycle is a closed loop. In order to find the stability of the limit cycle corresponds to the periodically stick-slip vibration, different initial conditions for the drill bit are studied. Results show that the drill bit will lead to a periodic motion and the phase trajectories ultimately converge to the same limit cycle corresponds to stable stick-slip vibration.

An approximate and an analytical solution to the carousel-pendulum problem

Energy Technology Data Exchange (ETDEWEB)

Vial, Alexandre [Pole Physique, Mecanique, Materiaux et Nanotechnologies, Universite de technologie de Troyes, 12, rue Marie Curie BP-2060, F-10010 Troyes Cedex (France)], E-mail: alexandre.vial@utt.fr

2009-09-15

We show that an improved solution to the carousel-pendulum problem can be easily obtained through a first-order Taylor expansion, and its accuracy is determined after the obtention of an unusable analytical exact solution, advantageously replaced by a numerical one. It is shown that the accuracy is unexpectedly high, even when the ratio length of the pendulum to carousel radius approaches unity. (letters and comments)

Effects of springs on a pendulum electromechanical energy harvester

Directory of Open Access Journals (Sweden)

Arnaud Notué Kadjie

2014-01-01

Full Text Available This paper studies a model of energy harvester that consists of an electromechanical pendulum system subjected to nonlinear springs. The output power is analyzed in terms of the intrinsic parameters of the device leading to optimal parameters for energy harvesting. It is found that in an appropriate range of the springs constant, the power attains higher values as compared to the case without springs. The dynamical behavior of the device shows transition to chaos.

Stochastic modeling of friction force and vibration analysis of a mechanical system using the model

International Nuclear Information System (INIS)

Kang, Won Seok; Choi, Chan Kyu; Yoo, Hong Hee

2015-01-01

The squeal noise generated from a disk brake or chatter occurred in a machine tool primarily results from friction-induced vibration. Since friction-induced vibration is usually accompanied by abrasion and lifespan reduction of mechanical parts, it is necessary to develop a reliable analysis model by which friction-induced vibration phenomena can be accurately analyzed. The original Coulomb's friction model or the modified Coulomb friction model employed in most commercial programs employs deterministic friction coefficients. However, observing friction phenomena between two contact surfaces, one may observe that friction coefficients keep changing due to the unevenness of contact surface, temperature, lubrication and humidity. Therefore, in this study, friction coefficients are modeled as random parameters that keep changing during the motion of a mechanical system undergoing friction force. The integrity of the proposed stochastic friction model was validated by comparing the analysis results obtained by the proposed model with experimental results.

Features of free and forced vibrations in systems with dry and viscous friction

International Nuclear Information System (INIS)

Kislyi, A.A.; Borovik, O.V.

1995-01-01

Curve-fitting methods are usually used to obtain the exact solution to vibration problems in which allowance is made for dry (Coulomb) friction, but these methods permit determination of the laws of motion only in individual cases. The fact that the initial differential equations contain a piecewise-linear function characterizing dry friction makes it difficult to establish-and, thus to analyze-the general law governing vibratory motion for this case. As a result, dry friction is replaced by an equivalent viscous friction, and the corresponding areas of the hysteresis loops are equated. However, such a substitution cannot be justified in many cases, since dry and viscous friction differ in physical nature and differently affect the main characteristics of both free and forced vibrations. Moreover, the area of the hysteresis loop is proportional to the square of the amplitude in viscous friction but is proportional to the first power of the latter in dry friction. If the method of signum-function delay is used, then it becomes possible to determine the continuous laws of motion of such systems and establish the features of dry friction compared to viscous friction

Investigation of the Relationship Between Molluscum Pendulum and Impairment of Carbohydrate Metabolism

Directory of Open Access Journals (Sweden)

Murat Kemal

2011-12-01

Full Text Available Background and Design: High blood sugar level, insulin resistance and dyslipidemia are accepted to be indicators of impaired carbohydrate metabolism. The potential role of these markers as well as the serum levels of insulin growth factor (IGF-1 and insulin growth factor binding protein (IGFBP-3 in the pathogenesis of molluscum pendulum were investigated in this study. Materials and methods: Forty-five molluscum pendulum patients and 45 age-, sex- and body mass index-matched healthy individuals as controls were enrolled in the study. Evaluation included dermatological examination, measurement of insulin resistance using HOMA-IR method, lipid profile, fasting blood glucose, postprandial blood glucose, fasting insulin, postprandial insulin, serum IGF-1 and IGFBP-3 levels. Results: Postprandial blood glucose, fasting insulin, postprandial insulin and Homeostazis Model Assesment (HOMA-IR levels of molluscum pendulum patients were statistically higher than those of controls (p=0.037, p=0.027, p=0.03, p=0.021 respectively, whereas serum IGF-1 and IGFBP-3 levels were significantly lower than those of controls (p=0.008, p=0.001. There was no difference in fasting glucose and lipid profile between the two groups. Three patients (6.7% had DM and one patient (13.3% had impaired glucose tolerance. Only one participant from the control group (2,2% had impaired glucose tolerance. The number of molluscum pendulum lesions correlated with fasting glucose, postprandial glucose, fasting insulin, postprandial insulin, HOMA-IR, total cholesterol and triglyceride levels. Conclusion: Molluscum pendulum patients should have blood glucose and insulin resistance measurements done and be followed up for DM. Patients with multiple lesions need to be evaluated for lipid problems. We suggest that serum IGF-1 and IGFBP-3 levels have no role in the pathogenesis of molluscum pendulum. (Turk­derm 2011; 45: 188-92

Friction induced hunting limit cycles : a comparison between the LuGre and switch friction model

NARCIS (Netherlands)

Hensen, R.H.A.; Molengraft, van de M.J.G.; Steinbuch, M.

2003-01-01

In this paper, friction induced limit cycles are predicted for a simple motion system consisting of a motor-driven inertia subjected to friction and a PID-controlled regulator task. The two friction models used, i.e., (i) the dynamic LuGre friction model and (ii) the static switch friction model,

Adaptive back-stepping control of the harmonic drive system with LuGre model-based friction compensation

Science.gov (United States)

Liu, Sen; Gang, Tieqiang

2018-03-01

Harmonic drives are widely used in aerospace and industrial robots. Flexibility, friction and parameter uncertainty will result in transmission performance degradation. In this paper, an adaptive back-stepping method with friction compensation is proposed to improve the tracking performance of the harmonic drive system. The nonlinear friction is described by LuGre model and compensated with a friction observer, and the uncertainty of model parameters is resolved by adaptive parameter estimation method. By using Lyapunov stability theory, it is proved that all the errors of the closed-loop system are uniformly ultimately bounded. Simulations illustrate the effectiveness of our friction compensation method.

Impact-friction vibrations of tubular systems. Numerical simulation and experimental validation

International Nuclear Information System (INIS)

Jacquart, G.

1993-05-01

This note presents a summary on the numerical developments made to simulate impact-friction vibrations of tubular systems, detailing the algorithms used and the expression of impact and friction forces. A synthesis of the experimental results obtained on MASSIF workbench is also presented, as well as their comparison with numerical computations in order to validate the numerical approach. (author). 5 refs

A Wave Power Device with Pendulum Based on Ocean Monitoring Buoy

Science.gov (United States)

Chai, Hui; Guan, Wanchun; Wan, Xiaozheng; Li, Xuanqun; Zhao, Qiang; Liu, Shixuan

2018-01-01

The ocean monitoring buoy usually exploits solar energy for power supply. In order to improve power supply capacity, this paper proposes a wave power device according to the structure and moving character of buoy. The wave power device composes of pendulum mechanism that converts wave energy into mechanical energy and energy storage mechanism where the mechanical energy is transferred quantitatively to generator. The hydrodynamic equation for the motion of buoy system with generator devise is established based on the potential flow theory, and then the characteristics of pendulum motion and energy conversion properties are analysed. The results of this research show that the proposed wave power devise is able to efficiently and periodically convert wave energy into power, and increasing the stiffness of energy storage spring is benefit for enhancing the power supply capacity of the buoy. This study provides a theory reference for the development of technology on wave power generator for ocean monitoring buoy.

Skin friction related behaviour of artificial turf systems.

Science.gov (United States)

Tay, Sock Peng; Fleming, Paul; Hu, Xiao; Forrester, Steph

2017-08-01

The occurrence of skin friction related injuries is an issue for artificial turf sports pitches and remains a barrier to their acceptance. The purpose of this study was to evaluate the current industry standard Securisport® Sports Surface Tester that measures skin surface related frictional behaviour of artificial turf. Little research has been published about the device and its efficacy, despite its widespread use as a standard FIFA test instrument. To achieve a range of frictional behaviours, several "third generation" (3G) carpet and infill combinations were investigated; friction time profiles throughout the Securisport rotations were assessed in combination with independent measurements of skin roughness before and after friction testing via 3D surface scanning. The results indicated that carpets without infill had greatest friction (coefficients of friction 0.97-1.20) while those completely filled with sand or rubber had similar and lower values independent of carpet type (coefficient of friction (COF) ≈0.57). Surface roughness of a silicone skin (s-skin) decreased after friction testing, with the largest change on sand infilled surfaces, indicating an "abrasive" polishing effect. The combined data show that the s-skin is damaged in a surface-specific manner, thus the Securisport COF values appear to be a poor measure of the potential for skin abrasion. It is proposed that the change in s-skin roughness improves assessment of the potential for skin damage when players slide on artificial turf.

Estimation method for first excursion probability of secondary system with impact and friction using maximum response

International Nuclear Information System (INIS)

Shigeru Aoki

2005-01-01

The secondary system such as pipings, tanks and other mechanical equipment is installed in the primary system such as building. The important secondary systems should be designed to maintain their function even if they are subjected to destructive earthquake excitations. The secondary system has many nonlinear characteristics. Impact and friction characteristic, which are observed in mechanical supports and joints, are common nonlinear characteristics. As impact damper and friction damper, impact and friction characteristic are used for reduction of seismic response. In this paper, analytical methods of the first excursion probability of the secondary system with impact and friction, subjected to earthquake excitation are proposed. By using the methods, the effects of impact force, gap size and friction force on the first excursion probability are examined. When the tolerance level is normalized by the maximum response of the secondary system without impact or friction characteristics, variation of the first excursion probability is very small for various values of the natural period. In order to examine the effectiveness of the proposed method, the obtained results are compared with those obtained by the simulation method. Some estimation methods for the maximum response of the secondary system with nonlinear characteristics have been developed. (author)

Acoustics of friction

Science.gov (United States)

Akay, Adnan

2002-04-01

This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media. Among the many everyday examples of friction sounds, violin music and brake noise in automobiles represent the two extremes in terms of the sounds they produce and the mechanisms by which they are generated. Of the multiple examples of friction sounds in nature, insect sounds are prominent. Friction also provides a means by which energy dissipation takes place at the interface of solids. Friction damping that develops between surfaces, such as joints and connections, in some cases requires only microscopic motion to dissipate energy. Modeling of friction-induced vibrations and friction damping in mechanical systems requires an accurate description of friction for which only approximations exist. While many of the components that contribute to friction can be modeled, computational requirements become prohibitive for their contemporaneous calculation. Furthermore, quantification of friction at the atomic scale still remains elusive. At the atomic scale, friction becomes a mechanism that converts the kinetic energy associated with the relative motion of surfaces to thermal energy. However, the description of the conversion to thermal energy represented by a disordered state of oscillations of atoms in a solid is still not well understood. At the macroscopic level, friction interacts with the vibrations and waves that it causes. Such interaction sets up a feedback between the friction force and waves at the surfaces, thereby making friction and surface motion interdependent. Such interdependence forms the basis for friction-induced motion as in the case of

Measuring the fill height of sealed cans with a compound pendulum

International Nuclear Information System (INIS)

Rinard, P.M.

1995-06-01

A compound pendulum has been designed, fabricated, tested, and used to determine the fill height of material in sealed cans. The specific cans that stimulated this work are partially filled with uranium and plutonium oxide. Fill height affects nondestructive assays using fission neutrons, but corrections for various fill heights can be made once the height is known. Heights vary with use as the powder compacts or loosens, so it is necessary to determine the height at the time of the neutron measurement. The pendulum is small and readily portable so it can be taken to the location of the neutron measurement. Tests with open cans filled with sand to various known heights had accuracies generally within 3%. Factors that can affect the accuracy are examined and discussed. Experience in using the pendulum on sealed cans is related

Reflections on Friction in Quantum Mechanics

Directory of Open Access Journals (Sweden)

Yair Rezek

2010-08-01

Full Text Available Distinctly quantum friction effects of three types are surveyed: internalfriction, measurement-induced friction, and quantum-fluctuation-induced friction. We demonstrate that external driving will lead to quantum internal friction, and critique the measurement-based interpretation of friction. We conclude that in general systems will experience internal and external quantum friction over and beyond the classical frictional contributions.

The friction coefficient of shoulder joints remains remarkably low over 24 h of loading.

Science.gov (United States)

Jones, Brian K; Durney, Krista M; Hung, Clark T; Ateshian, Gerard A

2015-11-05

The frictional response of whole human joints over durations spanning activities of daily living has not been reported previously. This study measured the friction of human glenohumeral joints during 24 h of reciprocal loading in a pendulum testing device, at moderate (0.2 mm/s, 4320 cycles) and low (0.02 mm/s, 432 cycles) sliding speeds, under a 200 N load. The effect of joint congruence was also investigated by testing human humeral heads against significantly larger mature bovine glenoids. Eight human joints and six bovine joints were tested in four combinations: human joints tested at moderate (hHCMS, n=6) and low speed (hHCLS, n=3), human humeral heads tested against bovine glenoids at moderate speed (LCMS, n=3), and bovine joints tested at moderate speed (bHCMS, n=3). In the first half hour the mean±standard deviation of the friction coefficient was hHCMS: 0.0016±0.0011, hHCLS: 0.0012±0.0002, LCMS: 0.0008±0.0002 and bHCMS: 0.0024±0.0008; in the last four hours it was hHCMS: 0.0057±0.0025, hHCLS: 0.0047±0.0017, LCMS: 0.0012±0.0003 and bHCMS: 0.0056±0.0016. The initial value was lower than the final value (pfriction coefficient of natural human shoulders remains remarkably low (averaging as little as 0.0015 and no greater than 0.006) for up to 24 h of continuous loading. The sustained low friction coefficients observed in incongruent joints (~0.001) likely represent rolling rather than sliding friction. Copyright © 2015. Published by Elsevier Ltd.

The Friction Coefficient of Shoulder Joints Remains Remarkably Low Over 24 h of Loading

Science.gov (United States)

Jones, Brian K.; Durney, Krista M.; Hung, Clark T.; Ateshian, Gerard A.

2015-01-01

The frictional response of whole human joints over durations spanning activities of daily living has not been reported previously. This study measured the friction of human glenohumeral joints during 24 h of reciprocal loading in a pendulum testing device, at moderate (0.2 mm/s, 4320 cycles) and low (0.02 mm/s, 432 cycles) sliding speeds, under a 200 N load. The effect of joint congruence was also investigated by testing human humeral heads against significantly larger mature bovine glenoids. Six human joints and six bovine joints were tested in four combinations: human joints tested at moderate (hHCMS, n=6) and low speed (hHCLS, n=3), human humeral heads tested against bovine glenoids at moderate speed (LCMS, n=3), and bovine joints tested at moderate speed (bHCMS, n=3). In the first half hour the mean ± standard deviation of the friction coefficient was hHCMS: 0.0016±0.0011, hHCLS: 0.0012±0.0002, LCMS: 0.0008±0.0002 and bHCMS: 0.0024±0.0008; in the last four hours it was hHCMS: 0.0057±0.0025, hHCLS: 0.0047±0.0017, LCMS: 0.0012±0.0003 and bHCMS: 0.0056±0.0016. The initial value was lower than the final value (pfriction coefficient of natural human shoulders remains remarkably low (averaging as little as 0.0015 and no greater than 0.006) for up to 24 h of continuous loading. The sustained low friction coefficients observed in incongruent joints (~0.001) likely represent rolling rather than sliding friction. PMID:26472306

New design head pendulum test rig for window airbag development; Neu entwickelte Kopfpendel-Testanlage fuer die Window-Airbag -Auslegung

Energy Technology Data Exchange (ETDEWEB)

Grundheber, C. [Adam Opel AG, Ruesselsheim (Germany); Lindstromberg, M. [Siemens Restraint Systems, Alzenau (Germany)

2001-07-01

Comparisons between vehicle crash tests and pendulum tests demonstrate good correlation. The head pendulum rig presents a faster, more economical alternative to the usual sled facilities. This is above all due to the simpler test set-up, which only considers the body parts relevant to the window airbag development, i.e. dummy head, neck and shoulder. The tuning of the system to new baseline values can also be carried out very quickly, by specific adjustments to the spring-damper arrangement. (orig.)

Development of an indirect counterbalanced pendulum optical-lever thrust balance for micro- to millinewton thrust measurement

International Nuclear Information System (INIS)

Grubišić, A N; Gabriel, S B

2010-01-01

This paper describes the design and testing of an indirect hanging pendulum thrust balance using a laser-optical-lever principle to provide micro- to millinewton thrust measurement for the development of electric propulsion systems. The design philosophy allows the selection of the total thrust range in order to maximize resolution through a counterbalanced pendulum principle, as well as passive magnetic damping in order to allow relatively rapid transient thrust measurement. The balance was designed for the purpose of hollow cathode microthruster characterization, but could be applied to other electric propulsion devices in the thrust range of micro- to millinewtons. An initial thrust characterization of the T5 hollow cathode is presented

Development of a software-hardware complex for studying the process of grinding by a pendulum deformer

Science.gov (United States)

Borisov, A. P.

2018-01-01

The article is devoted to the development of a software and hardware complex for investigating the grinding process on a pendulum deformer. The hardware part of this complex is the Raspberry Pi model 2B platform, to which a contactless angle sensor is connected, which allows to obtain data on the angle of deviation of the pendulum surface, usb-cameras, which allow to obtain grain images before and after grinding, and stepping motors allowing lifting of the pendulum surface and adjust the clearance between the pendulum and the supporting surfaces. The program part of the complex is written in C # and allows receiving data from the sensor and usb-cameras, processing the received data, and also controlling the synchronous-step motors in manual and automatic mode. The conducted studies show that the rational mode is the deviation of the pendulum surface by an angle of 400, and the location of the grain in the central zone of the support surface, regardless of the orientation of the grain in space. Also, due to the non-contact angle sensor, energy consumption for grinding, speed and acceleration of the pendulum surface, as well as vitreousness of grain and the energy consumption are calculated. With the help of photographs obtained from usb cameras, the work of a pendulum deformer based on the Rebinder formula and calculation of the grain area before and after grinding is determined.

A nearly-linear computational-cost scheme for the forward dynamics of an N-body pendulum

Science.gov (United States)

Chou, Jack C. K.

1989-01-01

The dynamic equations of motion of an n-body pendulum with spherical joints are derived to be a mixed system of differential and algebraic equations (DAE's). The DAE's are kept in implicit form to save arithmetic and preserve the sparsity of the system and are solved by the robust implicit integration method. At each solution point, the predicted solution is corrected to its exact solution within given tolerance using Newton's iterative method. For each iteration, a linear system of the form J delta X = E has to be solved. The computational cost for solving this linear system directly by LU factorization is O(n exp 3), and it can be reduced significantly by exploring the structure of J. It is shown that by recognizing the recursive patterns and exploiting the sparsity of the system the multiplicative and additive computational costs for solving J delta X = E are O(n) and O(n exp 2), respectively. The formulation and solution method for an n-body pendulum is presented. The computational cost is shown to be nearly linearly proportional to the number of bodies.

Friction

Science.gov (United States)

Matsuo, Yoshihiro; Clarke, Daryl D.; Ozeki, Shinichi

Friction materials such as disk pads, brake linings, and clutch facings are widely used for automotive applications. Friction materials function during braking due to frictional resistance that transforms kinetic energy into thermal energy. There has been a rudimentary evolution, from materials like leather or wood to asbestos fabric or asbestos fabric saturated with various resins such as asphalt or resin combined with pitch. These efforts were further developed by the use of woven asbestos material saturated by either rubber solution or liquid resin binder and functioned as an internal expanding brake, similar to brake lining system. The role of asbestos continued through the use of chopped asbestos saturated by rubber, but none was entirely successful due to the poor rubber heat resistance required for increased speeds and heavy gearing demands of the automobile industry. The use of phenolic resins as binder for asbestos friction materials provided the necessary thermal resistance and performance characteristics. Thus, the utility of asbestos as the main friction component, for over 100 years, has been significantly reduced in friction materials due to asbestos identity as a carcinogen. Steel and other fibrous components have displaced asbestos in disk pads. Currently, non-asbestos organics are the predominate friction material. Phenolic resins continue to be the preferred binder, and increased amounts are necessary to meet the requirements of highly functional asbestos-free disk pads for the automotive industry. With annual automobile production exceeding 70 million vehicles and additional automobile production occurring in developing countries worldwide and increasing yearly, the amount of phenolic resin for friction material is also increasing (Fig. 14.1). Fig. 14.1 Worldwide commercial vehicle production In recent years, increased fuel efficiency of passenger car is required due to the CO2 emission issue. One of the solutions to improve fuel efficiency is to

Dynamic response analysis of block foundations with nonlinear dry friction mounting system to impact loads

International Nuclear Information System (INIS)

Zheng, Enlai; Zhu, Sihong; Zhou, Xinlong

2014-01-01

It is essential to establish a dynamic model to predict and evaluate the dynamic performance of a nonlinear dry friction mounting system during design procedure, when it is impossible to carry out the test of prototype. Unlike the conventional ideal dry friction model where the direction of dry friction force is always considered to be opposite to that of relative velocity, a new equivalent resistance model of dry friction force is proposed based on the bilinear hysteretic model by introducing a parameter g in this work. The equivalent resistance contains spring force and damping force, whose direction is not opposite to that of relative velocity. Then, a dynamic model of the block foundation with nonlinear dry friction mounting system is established. When the equivalent resistance is applied to the dynamic model, its dynamic responses are obtained under common practical forms of press loads: rectangular pulse, half-sine pulse, and triangular pulse. Compared to experimental results, the dynamic responses based on the equivalent resistance model are more consistent with the simulation results based on the ideal dry friction model and the validity of the equivalent resistance model for the bilinear hysteretic model in this work is verified. Furthermore, the effect of the pulse shape and pulse duration on the dynamic responses of the block foundation with nonlinear dry friction mounting system is investigated.

On rotational solutions for elliptically excited pendulum

International Nuclear Information System (INIS)

Belyakov, Anton O.

2011-01-01

The author considers the planar rotational motion of the mathematical pendulum with its pivot oscillating both vertically and horizontally, so the trajectory of the pivot is an ellipse close to a circle. The analysis is based on the exact rotational solutions in the case of circular pivot trajectory and zero gravity. The conditions for existence and stability of such solutions are derived. Assuming that the amplitudes of excitations are not small while the pivot trajectory has small ellipticity the approximate solutions are found both for high and small linear dampings. Comparison between approximate and numerical solutions is made for different values of the damping parameter. -- Highlights: → We study rotations of the mathematical pendulum when its pivot moves along an ellipse. → There are stable exact solutions for a circular pivot trajectory and zero gravity. → Asymptotic solutions are found for an elliptical pivot trajectory

Proximity friction reexamined

International Nuclear Information System (INIS)

Krappe, H.J.

1989-01-01

The contribution of inelastic excitations to radial and tangential friction form-factors in heavy-ion collisions is investigated in the frame-work of perturbation theory. The dependence of the form factors on the essential geometrical and level-density parameters of the scattering system is exhibited in a rather closed form. The conditions for the existence of time-local friction coefficients are discussed. Results are compared to form factors from other models, in particular the transfer-related proximity friction. For the radial friction coefficient the inelastic excitation mechanism seems to be the dominant contribution in peripheral collisions. (orig.)

Visual interface for the automation of the instrumented pendulum of Charpy tests used in the surveillance program of reactors vessel of nuclear power plants

International Nuclear Information System (INIS)

Rojas S, A.S.; Sainz M, E.; Ruiz E, J.A.

2004-01-01

Inside the Programs of Surveillance of the nuclear power stations periodic information is required on the state that keep the materials with those that builds the vessel of the reactor. This information is obtained through some samples or test tubes that are introduced inside the core of the reactor and it is observed if its physical characteristics remain after having been subjected to the radiation changes and temperature. The rehearsal with the instrumented Charpy pendulum offers information on the behavior of fracture dynamics of a material. In the National Institute of Nuclear Research (ININ) it has an instrumented Charpy pendulum. The operation of this instrument is manual, having inconveniences to carry out rehearsals with radioactive material, handling of high and low temperatures, to fulfill the normative ones for the realization of the rehearsals, etc. In this work the development of a computational program is presented (virtual instrument), for the automation of the instrumented pendulum. The system has modules like: Card of data acquisition, signal processing, positioning system, tempered system, pneumatic system, compute programs like it is the visual interface for the operation of the instrumented Charpy pendulum and the acquisition of impact signals. This system shows that given the characteristics of the nuclear industry with radioactive environments, the virtual instrumentation and the automation of processes can contribute to diminish the risks to the personnel occupationally exposed. (Author)

The non-separability of ''dielectric'' and ''mechanical'' friction in molecular systems: A simulation study

International Nuclear Information System (INIS)

Kumar, P. V.; Maroncelli, M.

2000-01-01

Simulations of the time-dependent friction controlling rotational, translational, and vibrational motions of dipolar diatomic solutes in acetonitrile and methanol have been used to examine the nature of ''dielectric'' friction. The way in which electrical interactions increase the friction beyond that present in nonpolar systems is found to be rather different than what is anticipated by most theories of dielectric friction. Long-range electrostatic forces do not simply add an independent contribution to the friction due to short-ranged or ''mechanical'' sources (modeled here in terms of Lennard-Jones forces). Rather, the electrical and Lennard-Jones contributions are found to be strongly anticorrelated and not separable in any useful way. For some purposes, the mechanism by which electrical interactions increase friction is better viewed as a static electrostriction effect: electrical forces cause a subtle increase in atomic density in the solute's first solvation shell, which increases the amplitude of the force fluctuations derived from the Lennard-Jones interactions, i.e., the mechanical friction. However, electrical interactions also modify the dynamics of the friction, typically adding a long-time tail, which significantly increases the integral friction. Both of these effects must be included in a correct description of friction in the presence of polar interactions. (c) 2000 American Institute of Physics

Types and stability of quasi-periodic response of a spherical pendulum

Czech Academy of Sciences Publication Activity Database

Náprstek, Jiří; Fischer, Cyril

2013-01-01

Roč. 124, č. 8 (2013), s. 74-87 ISSN 0045-7949 R&D Projects: GA ČR(CZ) GA103/09/0094; GA AV ČR(CZ) IAA200710902 Institutional support: RVO:68378297 Keywords : non-linear vibration * spherical pendulum * auto-parametric systems * quasi-periodic processes * dynamic stability * asymptotic methods Subject RIV: JM - Building Engineering Impact factor: 2.178, year: 2013 http://www.sciencedirect.com/science/article/pii/S0045794912002672

Maxillary molar distalization or mandibular enhancement: a cephalometric comparison of comprehensive orthodontic treatment including the pendulum and the Herbst appliances.

Science.gov (United States)

Burkhardt, Donald R; McNamara, James A; Baccetti, Tiziano

2003-02-01

systems evaluated. The 2 general approaches we evaluated involved a substantial dentoalveolar component in the treatment of Class II malocclusion. A comparison of a molar-distalizing appliance such as the pendulum with other types of functional appliances might yield differing results.

Investigation of a Chaotic Double Pendulum in the Basic Level Physics Teaching Laboratory

Science.gov (United States)

Vanko, Peter

2007-01-01

First-year physics students at the Technical University of Budapest carry out a wide range of measurements in the Basic Level Physics Teaching Laboratory. One of the most exciting experiments is the investigation of a chaotic double pendulum by a V-scope, a powerful three-dimensional motion tracking system. After a brief introduction to the…

The Bravais pendulum: the distinct charm of an almost forgotten experiment

International Nuclear Information System (INIS)

Babovic, V M; Mekic, S

2011-01-01

In the year 1851 in Paris, the apparent change of the plane of oscillation of a linear pendulum was observed by Leon Foucault. In the same year, at the same place, the unequal duration of the oscillations of a right- and left-handed conical pendulum was observed by Bravais. Today, the Foucault pendula are common at universities, the Bravais pendula not at all. We have revisited and experimentally tested Bravais's method and found it worthy of revitalization in student labs.

The Bravais pendulum: the distinct charm of an almost forgotten experiment

Energy Technology Data Exchange (ETDEWEB)

Babovic, V M; Mekic, S [Department of Mathematics, Physics and Informatics, State University of Novi Pazar, Vuka Karadzica bb, 36300 Novi Pazar (Serbia)

2011-07-15

In the year 1851 in Paris, the apparent change of the plane of oscillation of a linear pendulum was observed by Leon Foucault. In the same year, at the same place, the unequal duration of the oscillations of a right- and left-handed conical pendulum was observed by Bravais. Today, the Foucault pendula are common at universities, the Bravais pendula not at all. We have revisited and experimentally tested Bravais's method and found it worthy of revitalization in student labs.

Dynamic Mesh CFD Simulations of Orion Parachute Pendulum Motion During Atmospheric Entry

Science.gov (United States)

Halstrom, Logan D.; Schwing, Alan M.; Robinson, Stephen K.

2016-01-01

This paper demonstrates the usage of computational fluid dynamics to study the effects of pendulum motion dynamics of the NASAs Orion Multi-Purpose Crew Vehicle parachute system on the stability of the vehicles atmospheric entry and decent. Significant computational fluid dynamics testing has already been performed at NASAs Johnson Space Center, but this study sought to investigate the effect of bulk motion of the parachute, such as pitching, on the induced aerodynamic forces. Simulations were performed with a moving grid geometry oscillating according to the parameters observed in flight tests. As with the previous simulations, OVERFLOW computational fluid dynamics tool is used with the assumption of rigid, non-permeable geometry. Comparison to parachute wind tunnel tests is included for a preliminary validation of the dynamic mesh model. Results show qualitative differences in the flow fields of the static and dynamic simulations and quantitative differences in the induced aerodynamic forces, suggesting that dynamic mesh modeling of the parachute pendulum motion may uncover additional dynamic effects.

Performance Evaluation on Transmission Tower-Line System with Passive Friction Dampers Subjected to Wind Excitations

Directory of Open Access Journals (Sweden)

Bo Chen

2015-01-01

Full Text Available The vibration control and performance evaluation on a transmission-tower line system by using friction dampers subjected to wind excitations are carried out in this study. The three-dimensional finite element (FE model of a transmission tower is firstly constructed. A two-dimensional lumped mass model of a transmission tower is developed for dynamic analysis. The analytical model of transmission tower-line system is proposed by taking the dynamic interaction between the tower and the transmission lines into consideration. The mechanical model of passive friction damper is presented by involving the effects of damper axial stiffness. The equation of motion of the transmission tower-line system incorporated with the friction dampers disturbed by wind excitations is established. A real transmission tower-line system is taken as an example to examine the feasibility and reliability of the proposed control approach. An extensive parameter study is carried out to find the optimal parameters of friction damper and to assess the effects of slipping force axial stiffness and hysteresis loop on control performance. The work on an example structure indicates that the application of friction dampers with optimal parameters could significantly reduce wind-induced responses of the transmission tower-line system.

The contact area and sliding friction in nanotribological systems

International Nuclear Information System (INIS)

Wolloch, M.

2014-01-01

Although friction, wear, and lubrication have been investigated for hundreds of years, many important questions in the field, now dubbed tribology, remain open. Two of these are the determination of the real area of contact and the direction dependence of friction forces on the nanoscale, which are investigated in this thesis. The invention of the atomic force microscope (AFM) in 1986 by Binnig , Quate, and Gerber was invaluable for the investigation of frictional forces on the atomic scale, giving a boost to the emerging field of nanotribology. While experimental AFM set-ups where quickly modeled with classical molecular dynamic (MD) simulations, the use of 'ab-initio' methods on tribological problems remained scarce until recently. In this thesis density functional theory (DFT) is used to develop parameter free methods in the field of nanotribology. Since the discovery that the apparent area of contact can be orders of magnitude larger than the true area of contact, the definition and determination of the latter has been an important topic of research. While classical contact mechanics provides satisfactory theories and results for various macroscopic systems, the application of these methods to atomistic systems is dubious, as the contacting bodies are not continuous at this length scale. We developed a parameter free approach to define and calculate the real area of contact between two bodies depending on distance. Strong relaxations at distinct distances, like the j ump to contact , which is often observed in AFM experiments, are used to define the onset of contact and Bader-s Quantum Theory of Atoms in Molecules is used to calculate the real area of contact at a given distance. Bader's method partitions the charge density ρ unambiguously into atoms, which theoretically fill all space and thus give non zero contact areas for all distances. It is therefore necessary to use a density cutoff ρ cut which assigns all regions in space where ρ < �

Robust sliding mode control for uncertain servo system using friction observer and recurrent fuzzy neural networks

International Nuclear Information System (INIS)

Han, Seong Ik; Jeong, Chan Se; Yang, Soon Yong

2012-01-01

A robust positioning control scheme has been developed using friction parameter observer and recurrent fuzzy neural networks based on the sliding mode control. As a dynamic friction model, the LuGre model is adopted for handling friction compensation because it has been known to capture sufficiently the properties of a nonlinear dynamic friction. A developed friction parameter observer has a simple structure and also well estimates friction parameters of the LuGre friction model. In addition, an approximation method for the system uncertainty is developed using recurrent fuzzy neural networks technology to improve the precision positioning degree. Some simulation and experiment provide the verification on the performance of a proposed robust control scheme

Robust sliding mode control for uncertain servo system using friction observer and recurrent fuzzy neural networks

Energy Technology Data Exchange (ETDEWEB)

Han, Seong Ik [Pusan National University, Busan (Korea, Republic of); Jeong, Chan Se; Yang, Soon Yong [University of Ulsan, Ulsan (Korea, Republic of)

2012-04-15

A robust positioning control scheme has been developed using friction parameter observer and recurrent fuzzy neural networks based on the sliding mode control. As a dynamic friction model, the LuGre model is adopted for handling friction compensation because it has been known to capture sufficiently the properties of a nonlinear dynamic friction. A developed friction parameter observer has a simple structure and also well estimates friction parameters of the LuGre friction model. In addition, an approximation method for the system uncertainty is developed using recurrent fuzzy neural networks technology to improve the precision positioning degree. Some simulation and experiment provide the verification on the performance of a proposed robust control scheme.

Comparative Research on Characteristics of the Isolation Systems with Dry Friction Damping and with Vicious Damping under Base Excitation

Science.gov (United States)

Hou, Junfang; jing, Min; Zhang, Weihua; Lu, Yahui; He, Haiwen

2017-12-01

As for the isolation problem of electronic equipments on vehicle, the vibration response characteristics of dry friction damping isolation system under base displacement excitation was analyzed in theory by harmonic balance method, and the displacement response was compared between the isolation systems with dry friction damping and vicious damping separately. The results show that the isolation system with small dry friction damping can’t meet the demands of displacement reduction close to the natural frequency, and it can realize full-frequency vibration isolation by improving dry friction damping when the lock frequency passes beyond the resonance frequency band. The results imply that the damping mechanism of dry friction isolator can’t be described only by dry friction damping, and the composite damping with dry friction and vicious damping is more appropriate.

Analysis of a simple pendulum driven at its suspension point

International Nuclear Information System (INIS)

Yoshida, S; Findley, T

2005-01-01

To familiarize undergraduate students with the dynamics of a damped driven harmonic oscillator, a simple pendulum was set up and driven at its suspension point under different damping conditions. From the time domain analysis, the decay constant was estimated and used to predict the frequency response. The simple pendulum was then driven at a series of frequencies near the resonance. By measuring the maximum amplitude at each driving frequency, the frequency response was determined. With one free parameter, which was determined under the first damping condition, the predicted frequency responses showed good agreement with the measured frequency responses under all damping conditions

Dynamical stability of a many-body Kapitza pendulum

Energy Technology Data Exchange (ETDEWEB)

Citro, Roberta, E-mail: citro@sa.infn.it [Dipartimento di Fisica “E. R. Caianiello” and Spin-CNR, Universita’ degli Studi di Salerno, Via Giovanni Paolo II, I-84084 Fisciano (Italy); Dalla Torre, Emanuele G., E-mail: emanuele.dalla-torre@biu.ac.il [Department of Physics, Bar Ilan University, Ramat Gan 5290002 (Israel); Department of Physics, Harvard University, Cambridge, MA 02138 (United States); D’Alessio, Luca [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Department of Physics, Boston University, Boston, MA 02215 (United States); Polkovnikov, Anatoli [Department of Physics, Boston University, Boston, MA 02215 (United States); Babadi, Mehrtash [Department of Physics, Harvard University, Cambridge, MA 02138 (United States); Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125 (United States); Oka, Takashi [Department of Applied Physics, University of Tokyo, Tokyo, 113-8656 (Japan); Demler, Eugene [Department of Physics, Harvard University, Cambridge, MA 02138 (United States)

2015-09-15

We consider a many-body generalization of the Kapitza pendulum: the periodically-driven sine–Gordon model. We show that this interacting system is dynamically stable to periodic drives with finite frequency and amplitude. This finding is in contrast to the common belief that periodically-driven unbounded interacting systems should always tend to an absorbing infinite-temperature state. The transition to an unstable absorbing state is described by a change in the sign of the kinetic term in the Floquet Hamiltonian and controlled by the short-wavelength degrees of freedom. We investigate the stability phase diagram through an analytic high-frequency expansion, a self-consistent variational approach, and a numeric semiclassical calculation. Classical and quantum experiments are proposed to verify the validity of our results.

The Pendulum as a Vehicle for Transitioning from Classical to Quantum Physics: History, Quantum Concepts, and Educational Challenges

Science.gov (United States)

Barnes, Marianne B.; Garner, James; Reid, David

2004-01-01

In this article we use the pendulum as the vehicle for discussing the transition from classical to quantum physics. Since student knowledge of the classical pendulum can be generalized to all harmonic oscillators, we propose that a quantum analysis of the pendulum can lead students into the unanticipated consequences of quantum phenomena at the…

The Effect of a Variable Disc Pad Friction Coefficient for the Mechanical Brake System of a Railway Vehicle

Science.gov (United States)

Lee, Nam-Jin; Kang, Chul-Goo

2015-01-01

A brake hardware-in-the-loop simulation (HILS) system for a railway vehicle is widely applied to estimate and validate braking performance in research studies and field tests. When we develop a simulation model for a full vehicle system, the characteristics of all components are generally properly simplified based on the understanding of each component’s purpose and interaction with other components. The friction coefficient between the brake disc and the pad used in simulations has been conventionally considered constant, and the effect of a variable friction coefficient is ignored with the assumption that the variability affects the performance of the vehicle braking very little. However, the friction coefficient of a disc pad changes significantly within a range due to environmental conditions, and thus, the friction coefficient can affect the performance of the brakes considerably, especially on the wheel slide. In this paper, we apply a variable friction coefficient and analyzed the effects of the variable friction coefficient on a mechanical brake system of a railway vehicle. We introduce a mathematical formula for the variable friction coefficient in which the variable friction is represented by two variables and five parameters. The proposed formula is applied to real-time simulations using a brake HILS system, and the effectiveness of the formula is verified experimentally by testing the mechanical braking performance of the brake HILS system. PMID:26267883

The Effect of a Variable Disc Pad Friction Coefficient for the Mechanical Brake System of a Railway Vehicle.

Science.gov (United States)

Lee, Nam-Jin; Kang, Chul-Goo

2015-01-01

A brake hardware-in-the-loop simulation (HILS) system for a railway vehicle is widely applied to estimate and validate braking performance in research studies and field tests. When we develop a simulation model for a full vehicle system, the characteristics of all components are generally properly simplified based on the understanding of each component's purpose and interaction with other components. The friction coefficient between the brake disc and the pad used in simulations has been conventionally considered constant, and the effect of a variable friction coefficient is ignored with the assumption that the variability affects the performance of the vehicle braking very little. However, the friction coefficient of a disc pad changes significantly within a range due to environmental conditions, and thus, the friction coefficient can affect the performance of the brakes considerably, especially on the wheel slide. In this paper, we apply a variable friction coefficient and analyzed the effects of the variable friction coefficient on a mechanical brake system of a railway vehicle. We introduce a mathematical formula for the variable friction coefficient in which the variable friction is represented by two variables and five parameters. The proposed formula is applied to real-time simulations using a brake HILS system, and the effectiveness of the formula is verified experimentally by testing the mechanical braking performance of the brake HILS system.

Development of pendulum mechanism and kinematic coordination from the first unsupported steps in toddlers

NARCIS (Netherlands)

Ivanenko, Yuri P; Dominici, Nadia; Cappellini, Germana; Dan, Bernard; Cheron, Guy; Lacquaniti, Francesco

2004-01-01

The inverted pendulum model in which the centre of mass of the body vaults over the stance leg in an arc represents a basic mechanism of bipedal walking. Is the pendulum mechanism innate, or is it learnt through walking experience? We studied eight toddlers (about 1 year old) at their first

A Novel Real-Time Data Acquisition Using an Excel Spreadsheet in Pendulum Experiment Tool with Light-Based Timer

Science.gov (United States)

Adhitama, Egy; Fauzi, Ahmad

2018-01-01

In this study, a pendulum experimental tool with a light-based timer has been developed to measure the period of a simple pendulum. The obtained data was automatically recorded in an Excel spreadsheet. The intensity of monochromatic light, sensed by a 3DU5C phototransistor, dynamically changes as the pendulum swings. The changed intensity varies…

A novel real-time data acquisition using an Excel spreadsheet in pendulum experiment tool with light-based timer

Science.gov (United States)

Adhitama, Egy; Fauzi, Ahmad

2018-05-01

In this study, a pendulum experimental tool with a light-based timer has been developed to measure the period of a simple pendulum. The obtained data was automatically recorded in an Excel spreadsheet. The intensity of monochromatic light, sensed by a 3DU5C phototransistor, dynamically changes as the pendulum swings. The changed intensity varies the resistance value and was processed by the microcontroller, ATMega328, to obtain a signal period as a function of time and brightness when the pendulum crosses the light. Through the experiment, using calculated average periods, the gravitational acceleration value has been accurately and precisely determined.

Seismometer using a vertical long natural-period rotational pendulum with magnetic levitation

International Nuclear Information System (INIS)

Otake, Yuji; Araya, Akito; Hidano, Kazuo

2005-01-01

We have demonstrated a highly sensitive/wideband vertical-component seismometer using an astatic rotational pendulum to obtain a long natural period. This seismometer employs magnetic levitation for removing any parasitic resonances of a spring to support a weight due to gravity and the thermal dependence of the spring constant. The pendulum has a cylindrical plunger-type permanent magnet that has a weight at one side of its end edge. The plunger magnet is inserted into a uniform magnetic field generated by a window-frame-type permanent magnet, and attached to two crossed-leaf spring hinges as a rotational axis outside of the bore of the magnet. Magnetic forces applied to the plunger magnet counterbalance the gravitational force at the weight. To realize stable operation of the rotational pendulum without any unnecessary movements of the plunger magnet, a tilt of lines of the magnetic force in the bore of the window-frame magnet was compensated by a tilted magnetic-pole surface near to its opening. The field uniformity reached 10 -4 owing to this compensation. The thermal dependence of a magnetic field strength of about 10 -3 /K was also compensated by as much as 9x10 -5 /K by Ni-Fe metal having a negative permeability coefficient. The metal was attached along the sidewalls of the window-frame magnet. To determine the feedback control parameters for a feedback control seismometer, the natural period of a prototype rotational pendulum was measured. It was more than 8 s, and was able to be changed from 5 to 8 s by using an additional magnetic spring, similar to the voice coil actuator of a speaker. This change was in accordance with theoretical calculations, and showed that the pendulum movement did not include a big nonlinearity caused by the tilt of the lines of the magnetic force. No parasitic resonances were found during experiments. A velocity feedback-control circuit and a capacitance position detector to measure the weight position were applied to the

Static and dynamic properties of frictional phenomena in a one-dimensional system with randomness

International Nuclear Information System (INIS)

Kawaguchi, T.; Matsukawa, H.

1997-01-01

Static and dynamic frictional phenomena at the interface with random impurities are investigated in a two-chain model with incommensurate structure. Static frictional force is caused by the impurity pinning and/or by the pinning due to the regular potential, which is responsible for the breaking of analyticity transition for impurity-free cases. It is confirmed that the static frictional force is always finite in the presence of impurities, in contrast to the impurity-free system. The nature of impurity pinning is discussed in connection with that in density waves. The kinetic frictional force of a steady sliding state is also investigated numerically. The relationship between the sliding velocity dependence of the kinetic frictional force and the strength of impurity potential is discussed. copyright 1997 The American Physical Society

Towards measuring the off-resonant thermal noise of a pendulum mirror

CERN Document Server

Leonhardt, V; Kloevekorn, P; Willke, B; Lück, H B; Danzmann, K

2002-01-01

Thermal noise is one of the dominant noise sources in interferometric length measurements and can limit the sensitivity of gravitational wave detectors. Our goal is to analyse the off-resonant thermal noise of a high Q pendulum. Therefore we interferometrically detect the length changes of a 2.3 cm long optical resonator, which for good seismic isolation consists of two multiple stage pendulums. We are able to lock the length of this optical resonator to a frequency-stabilized laser beam and as a result get the spectral density of the differential mirror movement.

Parameter Identification and Adaptive Control Applied to the Inverted Pendulum

Directory of Open Access Journals (Sweden)

Carlos A. Saldarriaga-Cortés

2012-06-01

Full Text Available This paper presents a methodology to implement an adaptive control of the inverted pendulum system; which uses the recursive square minimum method for the identification of a dynamic digital model of the plant and then, with its estimated parameters, tune in real time a pole placement control. The plant to be used is an unstable and nonlinear system. This fact, combined with the adaptive controller characteristics, allows the obtained results to be extended to a great variety of systems. The results show that the above methodology was implemented satisfactorily in terms of estimation, stability and control of such a system. It was established that adaptive techniques have a proper performance even in systems with complex features such as nonlinearity and instability.

The exact equation of motion of a simple pendulum of arbitrary amplitude: a hypergeometric approach

International Nuclear Information System (INIS)

Qureshi, M I; Rafat, M; Azad, S Ismail

2010-01-01

The motion of a simple pendulum of arbitrary amplitude is usually treated by approximate methods. By using generalized hypergeometric functions, it is however possible to solve the problem exactly. In this paper, we provide the exact equation of motion of a simple pendulum of arbitrary amplitude. A new and exact expression for the time of swinging of a simple pendulum from the vertical position to an arbitrary angular position θ is given by equation (3.10). The time period of such a pendulum is also exactly expressible in terms of hypergeometric functions. The exact expressions thus obtained are used to plot the graphs that compare the exact time period T(θ 0 ) with the time period T(0) (based on simple harmonic approximation). We also compare the relative difference between T(0) and T(θ 0 ) found from the exact equation of motion with the usual perturbation theory estimate. The treatment is intended for graduate students, who have acquired some familiarity with the hypergeometric functions. This approach may also be profitably used by specialists who encounter during their investigations nonlinear differential equations similar in form to the pendulum equation. Such nonlinear differential equations could arise in diverse fields, such as acoustic vibrations, oscillations in small molecules, turbulence and electronic filters, among others.

Some aspects of the electromagnetic-impulse pendulum and Biot-Savart-Lorentz force

International Nuclear Information System (INIS)

Moyssides, P.G.; Hatzikonstantinou, P.

1988-01-01

The purpose of this paper is to cast light on various serious mistakes which have been involved during the analysis of two experiments, related to the correctness of the Biot-Savart-Lorentz force law. At first in the MIT experiment, carried out by Graneau et al., they claim that the calculated momentum, imparted to an electrodynamic-impulse pendulum, using the BSL force law, is 43% larger than the experimentally measured momentum of the pi-frame pendulum. It has been found that discrepancy, using their own data, is due to the use of a wrong value for the time constant parameter introduced in the current formula. In addition Pappas, like Graneau, although states that all the available energy is dissipated to Joule heating, considers that all the pendulum momentum is imparted to field momentum yielding an enormous amount of field-radiated energy, which is also completely wrong

Comment on 'Approximation for a large-angle simple pendulum period'

International Nuclear Information System (INIS)

Yuan Qingxin; Ding Pei

2009-01-01

In a recent letter, Belendez et al (2009 Eur. J. Phys. 30 L25-8) proposed an alternative of approximation for the period of a simple pendulum suggested earlier by Hite (2005 Phys. Teach. 43 290-2) who set out to improve on the Kidd and Fogg formula (2002 Phys. Teach. 40 81-3). As a response to the approximation scheme, we obtain another analytical approximation for the large-angle pendulum period, which owns the simplicity and accuracy in evaluating the exact period, and moreover, for amplitudes less than 144 deg. the analytical approximate expression is more accurate than others in the literature. (letters and comments)

Two calibration procedures for a gyroscope-free inertial measurement system based on a double-pendulum apparatus

Science.gov (United States)

Cappa, P.; Patanè, F.; Rossi, S.

2008-05-01

This paper presents a novel calibration algorithm to be used with a gyro-free inertial measurement unit (GF-IMU) based on the use of linear accelerometers (AC). The analytical approach can be implemented in two calibration procedures. The first procedure (P-I) is articulated in the conduction of a static trial, to compute the sensitivity and the direction of the sensing axis of each AC, followed by a dynamic trial, to determine the AC locations. By contrast, the latter procedure (P-II) consists in the calculation of the previously indicated calibration parameters by means of a dynamic trial only. The feasibility of the two calibration procedures has been investigated by testing two GF-IMUs, equipped with ten and six bi-axial linear ACs, with an ad hoc instrumented double-pendulum apparatus. P-I and P-II were compared to a calibration procedure used as a reference (P-REF), which incorporates the AC positions measured with an optoelectronic system. The experimental results we present in this paper demonstrate that (i) P-I is able to determine the calibration parameters of the AC array with a higher accuracy than P-II; (ii) consequently, the errors associated with translational (a0 - g) and rotational (\\dot{\\bm \\omega }) acceleration components for the two GF-IMUs are significantly greater using P-II than P-I and (iii) the errors in (a0 - g) and \\dot{\\bm \\omega } obtained with P-I are comparable with the ones obtainable by using P-REF. Thus, the proposed novel algorithm used in P-I, in conjunction with the double-pendulum apparatus, can be globally considered a viable tool in GF-IMU calibration.

Nonlinear Coupling Characteristics Analysis of Integrated System of Electromagnetic Brake and Frictional Brake of Car

Directory of Open Access Journals (Sweden)

Ren He

2015-01-01

Full Text Available Since theoretical guidance is lacking in the design and control of the integrated system of electromagnetic brake and frictional brake, this paper aims to solve this problem and explores the nonlinear coupling characteristics and dynamic characteristics of the integrated system of electromagnetic brake and frictional brake. This paper uses the power bond graph method to establish nonlinear coupling mathematical model of the integrated system of electromagnetic brake and frictional brake and conducts the contrastive analysis on the dynamic characteristics based on this mathematical model. Meanwhile, the accuracy of the nonlinear coupling mathematical model proposed above is verified on the hardware in the loop simulation platform, and nonlinear coupling characteristics of the integrated system are also analyzed through experiments.

Dynamic response of piping system on rack structure with gaps and frictions

International Nuclear Information System (INIS)

Kobayashi, Hiroe; Yoshida, Misutoyo; Ochi, Yoshio

1989-01-01

In the seismic design of a piping system on a rack structure, the interaction between the piping system and the rack structure must be evaluated under the condition that the rack structure is not stiff and heavy enough compared with the piping system. Moreover, there are local nonlinearities due to the gap and friction between the piping system and the rack structure. This paper presents the influence of the interaction and the local nonlinearities upon the seismic response by numerical study and a vibration test using a shaking table. In the numerical study, the piping system and the rack structure were represented by the three degrees of freedom mass-spring model taking a vibration mode of the piping system into account. The nonlinearities due to gap and friction were defined as a function of motion and treated as the pseudo force vector (additional applied force) in an equation of motion. From the results of the numerical study and the vibration test, it was clarified that seismic response of both the rack structure and the piping system is reduced by gap and friction. Moreover, the piping system and rack structure can be represented by the three degrees of freedom mass spring model. And the local nonlinearities can be treated by the pseudo force in an equation of motion. (orig.)

World pendulum-a distributed remotely controlled laboratory (RCL) to measure the Earth's gravitational acceleration depending on geographical latitude

International Nuclear Information System (INIS)

Groeber, S; Vetter, M; Eckert, B; Jodl, H-J

2007-01-01

We suggest that different string pendulums are positioned at different locations on Earth and measure at each place the gravitational acceleration (accuracy Δg ∼ 0.01 m s -2 ). Each pendulum can be remotely controlled via the internet by a computer located somewhere on Earth. The theoretical part describes the physical origin of this phenomenon g(ψ), that the Earth's effective gravitational acceleration g depends on the angle of latitude ψ. Then, we present all necessary formula to deduce g(ψ) from oscillations of a string pendulum. The technical part explains tips and tricks to realize such an apparatus to measure all necessary values with sufficient accuracy. In addition, we justify the precise dimensions of a physical pendulum such that the formula for a mathematical pendulum is applicable to determine g(ψ) without introducing errors. To conclude, we describe the internet version-the string pendulum as a remotely controlled laboratory. The teaching relevance and educational value will be discussed in detail at the end of this paper including global experimenting, using the internet and communication techniques in teaching and new ways of teaching and learning methods

Operational Modal Analysis based Stress Estimation in Friction Systems

DEFF Research Database (Denmark)

Tarpø, Marius; Friis, Tobias; Nabuco, Bruna

this assumption. In this paper, the precision of estimating the strain response of a nonlinear system is investigated using the operational response of numerical simulations. Local nonlinearities are introduced by adding friction to the test specimen and this paper finds that this approach of strain estimation...

Approximate Expressions for the Period of a Simple Pendulum Using a Taylor Series Expansion

Science.gov (United States)

Belendez, Augusto; Arribas, Enrique; Marquez, Andres; Ortuno, Manuel; Gallego, Sergi

2011-01-01

An approximate scheme for obtaining the period of a simple pendulum for large-amplitude oscillations is analysed and discussed. When students express the exact frequency or the period of a simple pendulum as a function of the oscillation amplitude, and they are told to expand this function in a Taylor series, they always do so using the…

Identification of complex systems by artificial neural networks. Applications to mechanical frictions

International Nuclear Information System (INIS)

Dominguez, Manuel

1998-01-01

In the frame of complex systems modelization, we describe in this report the contribution of neural networks to mechanical friction modelization. This thesis is divided in three parts, each one corresponding to every stage of the realized work. The first part takes stock of the properties of neural networks by replacing them in the statistic frame of learning theory (particularly: non-linear and non-parametric regression models) and by showing the existing links with other more 'classic' techniques from automatics. We show then how identification models can be integrated in the neural networks description as a larger nonlinear model class. A methodology of neural networks use have been developed. We focused on validation techniques using correlation functions for non-linear systems, and on the use of regularization methods. The second part deals with the problematic of friction in mechanical systems. Particularly, we present the main current identified physical phenomena, which are integrated in advanced friction modelization. Characterization of these phenomena allows us to state a priori knowledge to be used in the identification stage. We expose some of the most well-known friction models: Dahl's model, Reset Integrator and Canuda's dynamical model, which are then used in simulation studies. The last part links the former one by illustrating a real-world application: an electric jack from SFIM-Industries, used in the Very Large Telescope (VLT) control scheme. This part begins with physical system presentation. The results are compared with more 'classic' methods. We finish using neural networks compensation scheme in closed-loop control. (author) [fr

Nonlinear dynamic analysis of a structure with a friction-based seismic base isolation system

NARCIS (Netherlands)

Suy, H.M.R.; Fey, R.H.B.; Galanti, F.M.B.; Nijmeijer, H.

2007-01-01

Abstract Many dynamical systems are subject to some form of non-smooth or discontinuous nonlinearity. One eminent example of such a nonlinearity is friction. This is caused by the fact that friction always opposes the direction of movement, thus changing sign when the sliding velocity changes sign.

Internal friction in hydrited Zircaloy 4

International Nuclear Information System (INIS)

Piquin, R.; Ghilarducci, Ada A.; Salva, Horacio R.

2007-01-01

The aim of this work is to investigate the microscopic basis of inelastic effects on standard Zry4 alloy, after plastic deformation and hydriding. Polycrystalline samples with cylindrical geometry were taken with dimension 1.62mm in diameter and 40 mm in length. In order to obtain the internal friction and elastic modulus spectra at low frequencies (0.01 to 10Hz), a sub resonant forced pendulum was used, with resonance at about 130Hz. The results are peaks between 150 and 350K. They are analysed on the basis of their response at frequency changes, amplitude of measurement, grade of plastic deformation 'in situ' and cathodical hydriding (650 H wt ppm). The peaks are interpreted as follows: the 250K peak corresponds to the interaction between dislocations and Cottrel cloud of solute atoms surrounding the dislocation cores. After hydruration, the spectrum is dominated by the 220K peak, which is attributed to the hydrogen atoms in solid solution trapped by the dislocation cores. The anelastic parameters allow to evaluate the H concentration segregated on dislocations, in this case it is 300 wt ppm H. (author) [es

Friction, Free Axes of Rotation and Entropy

Directory of Open Access Journals (Sweden)

Alexander Kazachkov

2017-03-01

Full Text Available Friction forces acting on rotators may promote their alignment and therefore eliminate degrees of freedom in their movement. The alignment of rotators by friction force was shown by experiments performed with different spinners, demonstrating how friction generates negentropy in a system of rotators. A gas of rigid rotators influenced by friction force is considered. The orientational negentropy generated by a friction force was estimated with the Sackur-Tetrode equation. The minimal change in total entropy of a system of rotators, corresponding to their eventual alignment, decreases with temperature. The reported effect may be of primary importance for the phase equilibrium and motion of ubiquitous colloidal and granular systems.

Mechanical Systems based on Dry Friction Force used for Building Isolation against Seismic Actions

Directory of Open Access Journals (Sweden)

Fanel Dorel Şcheaua

2017-11-01

Full Text Available Today there are multiple solutions intended to avoid the earthquake damaging effects on building structures. There are methods based on the use of special mechanical systems attached directly to the structure's resistance frames, by means of which an improved building behavior is achieved during the earthquake. The systems used work on the principle of structure base isolation based on the dry friction force (Coulomb friction. Some constructive types of these isolation systems patterns are described in this paper

Classroom Explorations: Pendulums, Mirrors, and Galileo's Drama

Science.gov (United States)

Cavicchi, Elizabeth

2011-01-01

What do you see in a mirror when not looking at yourself? What goes on as a pendulum swings? Undergraduates in a science class supposed that these behaviors were obvious until their explorations exposed questions with no quick answers. While exploring materials, students researched Galileo, his trial, and its aftermath. Galileo came to life both…

Nonlinear dynamic analysis of a structure with a friction-based seismic base isolation system

NARCIS (Netherlands)

Suy, H.M.R.; Fey, R.H.B.; Galanti, F.M.B.; Nijmeijer, H.

2007-01-01

Many dynamical systems are subject to some form of non-smooth or discontinuous nonlinearity. One eminent example of such a nonlinearity is friction. This is caused by the fact that friction always opposes the direction of movement, thus changing sign when the sliding velocity changes sign. In this

Analytical results on the periodically driven damped pendulum. Application to sliding charge-density waves and Josephson junctions

International Nuclear Information System (INIS)

Azbel, M.Y.; Bak, P.

1984-01-01

The differential equation epsilonphi-dieresis+phi-dot-(1/2)α sin(2phi) = I+summation/sub n/ = -infinity/sup infinity/A/sub n/delta(t-t/sub n/) describing the periodically driven damped pendulum is analyzed in the strong damping limit epsilon<<1, using first-order perturbation theory. The equation may represent the motion of a sliding charge-density wave (CDW) in ac plus dc electric fields, and the resistively shunted Josephson junction driven by dc and microwave currents. When the torque I exceeds a critical value the pendulum rotates with a frequency ω. For infinite damping, or zero mass (epsilon = 0), the equation can be transformed to the Schroedinger equation of the Kronig-Penney model. When A/sub n/ is random the pendulum exhibits chaotic motion. In the regular case A/sub n/ = A the frequency ω is a smooth function of the parameters, so there are no phase-locked subharmonic plateaus in the ω(I) curve, or the I-V characteristics for the CDW or Josephson-junction systems. For small nonzero epsilon the return map expressing the phase phi(t/sub n/+1) as a function of the phase phi(t/sub n/) is a one-dimensional circle map. Applying known analytical results for the circle map one finds narrow subharmonic plateaus at all rational frequencies, in agreement with experiments on CDW systems

Proportional Retarded Controller to Stabilize Underactuated Systems with Measurement Delays: Furuta Pendulum Case Study

Directory of Open Access Journals (Sweden)

T. Ortega-Montiel

2017-01-01

Full Text Available The design and tuning of a simple feedback strategy with delay to stabilize a class of underactuated mechanical systems with dead time are presented. A linear time-invariant (LTI model with time delay of fourth order and a Proportional Retarded (PR controller are considered. The PR controller is shown as an appealing alternative to the application of observer-based controllers. This paper gives a step forward to obtain a better understanding of the effect of output delays and related phenomena in mechatronic systems, making it possible to design resilient control laws under the presence of uncertain time delays in measurements and obtain an acceptable performance without using a derivative action. The Furuta pendulum is a standard two-degrees-of-freedom benchmark example from the class of underactuated mechanical systems. The configuration under study includes an inherent output delay due to wireless communication used to transmit measurements of the pendulum’s angular position. Our approach offers a constructive design and a procedure based on a combination of root loci and Mikhailov methods for the analysis of stability. Experiments over a laboratory platform are reported and a comparison with a standard linear state feedback control law shows the advantages of the proposed scheme.

Measurement of g using a magnetic pendulum and a smartphone magnetometer

Science.gov (United States)

Pili, Unofre; Violanda, Renante; Ceniza, Claude

2018-04-01

The internal sensors in smartphones for their advanced add-in functions have also paved the way for these gadgets becoming multifunctional tools in elementary experimental physics. For instance, the acceleration sensor has been used to analyze free-falling motion and to study the oscillations of a spring-mass system. The ambient light sensor on the other hand has been proven to be a capable tool in studying an astronomical phenomenon as well as in measuring speed and acceleration. In this paper we present an accurate, convenient, and engaging use of the smartphone magnetic field sensor to measure the acceleration due to gravity via measurement of the period of oscillations (simply called "period" in what follows) of a simple pendulum. Measurement of the gravitational acceleration via the simple pendulum is a standard elementary physics laboratory activity, but the employment of the magnetic field sensor of a smartphone device in measuring the period is quite new and the use of it is seen as fascinating among students. The setup and procedure are rather simple and can easily be replicated as a classroom demonstration or as a regular laboratory activity.

Advances on LuGre friction model

OpenAIRE

Fuad, Mohammad; Ikhouane, Fayçal

2013-01-01

LuGre friction model is an ordinary differential equation that is widely used in describing the friction phenomenon for mechanical systems. The importance of this model comes from the fact that it captures most of the friction behavior that has been observed including hysteresis. In this paper, we study some aspects related to the hysteresis behavior induced by the LuGre friction model.

Low temperature internal friction on γ-irradiated polyvinylidene fluoride (PVDF)

International Nuclear Information System (INIS)

Callens, A.; Eersels, L.; De Batist, R.

1978-01-01

A least-squares fitting of the below room temperature part of the internal friction spectra, obtained by the torsion pendulum technique on as-received and γ-irradiated (up to 1 Grad) strips and fibres of polyvinylidene fluoride by a superposition of single Debye functions, reveals that the spectral component features are determined not only by purely amorphous chain characteristics but also by the dose-dependence of crystallinity. A careful analysis of the relaxation spectra confirms that at least one relaxation effect (approximately 236 K) is created upon irradiation. The analysis of the dose dependence of the characteristics of the β (glass transition; approximately 220 K) and βsub(u) (apparent upper glass transition; approximately 270 K) relaxations, suggests the probable influence of crystallinity on the molecular motion in the amorphous phase. The increase of the intensity of the γ relaxation (approximately 190 K) is related to the irradiation-induced crystallite degradation. (author)

Application of Kingview and PLC in friction durability test system

Science.gov (United States)

Gao, Yinhan; Cui, Jing; Yang, Kaiyu; Ke, Hui; Song, Bing

2013-01-01

Using PLC and Kingview software, a friction durability test system is designed. The overall program, hardware configuration, software structure and monitoring interface are described in detail. PLC ensures the stability of data acquisition, and the KingView software makes the HMI easy to manipulate. The practical application shows that the proposed system is cheap, economical and highly reliable.

Regularized friction and continuation: Comparison with Coulomb's law

OpenAIRE

Vigué, Pierre; Vergez, Christophe; Karkar, Sami; Cochelin, Bruno

2016-01-01

International audience; Periodic solutions of systems with friction are difficult to investigate because of the irregular nature of friction laws. This paper examines periodic solutions and most notably stick-slip, on a simple one-degre-of-freedom system (mass, spring, damper, belt), with Coulomb's friction law, and with a regularized friction law (i.e. the friction coefficient becomes a function of relative speed, with a stiffness parameter). With Coulomb's law, the stick-slip solution is co...

The compound pendulum in intermediate laboratories and demonstrations

DEFF Research Database (Denmark)

Pedersen, Niels Falsig; Sørensen, O. Hoffmann

1977-01-01

A student laboratory course on the motion of the compound pendulum is described. The course is suited for physics and engineering students in their first year and requires a background in mechanics and mathematics corresponding to a one-semester course in these disciplines. The purpose of this co...

Enhanced nanoscale friction on fluorinated graphene.

Science.gov (United States)

Kwon, Sangku; Ko, Jae-Hyeon; Jeon, Ki-Joon; Kim, Yong-Hyun; Park, Jeong Young

2012-12-12

Atomically thin graphene is an ideal model system for studying nanoscale friction due to its intrinsic two-dimensional (2D) anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro- and nanomechanical devices. Here, we report unexpectedly enhanced nanoscale friction on chemically modified graphene and a relevant theoretical analysis associated with flexural phonons. Ultrahigh vacuum friction force microscopy measurements show that nanoscale friction on the graphene surface increases by a factor of 6 after fluorination of the surface, while the adhesion force is slightly reduced. Density functional theory calculations show that the out-of-plane bending stiffness of graphene increases up to 4-fold after fluorination. Thus, the less compliant F-graphene exhibits more friction. This indicates that the mechanics of tip-to-graphene nanoscale friction would be characteristically different from that of conventional solid-on-solid contact and would be dominated by the out-of-plane bending stiffness of the chemically modified graphene. We propose that damping via flexural phonons could be a main source for frictional energy dissipation in 2D systems such as graphene.

Chaotic mechanics in systems with impacts and friction

CERN Document Server

Blazejczyk-Okolewska, Barbara; Kapitaniak, Tomasz; Wojewoda, Jerzy

1999-01-01

This book is devoted to the theory of chaotic oscillations in mechanical systems. Detailed descriptions of the basic types of nonlinearity - impacts and dry friction - are presented. The properties of such behavior are discussed, and the numerical and experimental results obtained by the authors are presented.The dynamic properties of systems described here can be useful in the proper design and use of mechanics where such behavior still creates problems.This book will be very useful for anyone with a fundamental knowledge of nonlinear mechanics who is beginning research in the field.

High speed friction microscopy and nanoscale friction coefficient mapping

International Nuclear Information System (INIS)

Bosse, James L; Lee, Sungjun; Huey, Bryan D; Andersen, Andreas Sø; Sutherland, Duncan S

2014-01-01

As mechanical devices in the nano/micro length scale are increasingly employed, it is crucial to understand nanoscale friction and wear especially at technically relevant sliding velocities. Accordingly, a novel technique has been developed for friction coefficient mapping (FCM), leveraging recent advances in high speed AFM. The technique efficiently acquires friction versus force curves based on a sequence of images at a single location, each with incrementally lower loads. As a result, true maps of the coefficient of friction can be uniquely calculated for heterogeneous surfaces. These parameters are determined at a scan velocity as fast as 2 mm s −1 for microfabricated SiO 2 mesas and Au coated pits, yielding results that are identical to traditional speed measurements despite being ∼1000 times faster. To demonstrate the upper limit of sliding velocity for the custom setup, the friction properties of mica are reported from 200 µm s −1 up to 2 cm s −1 . While FCM is applicable to any AFM and scanning speed, quantitative nanotribology investigations of heterogeneous sliding or rolling components are therefore uniquely possible, even at realistic velocities for devices such as MEMS, biological implants, or data storage systems. (paper)

Friction dampers, the positive side of friction

NARCIS (Netherlands)

Lopez Arteaga, I.; Nijmeijer, H.; Busturia, J.M.; Sas, P.; Munck, de M.

2004-01-01

Friction is frequently seen as an unwanted phenomenon whose influence has to be either minimised or controlled. In this work one of the positive sides of friction is investigated: friction damping. Friction dampers can be a cheap and efficient way to reduce the vibration levels of a wide range of

Adaptive integral backstepping sliding mode control for opto-electronic tracking system based on modified LuGre friction model

Science.gov (United States)

Yue, Fengfa; Li, Xingfei; Chen, Cheng; Tan, Wenbin

2017-12-01

In order to improve the control accuracy and stability of opto-electronic tracking system fixed on reef or airport under friction and external disturbance conditions, adaptive integral backstepping sliding mode control approach with friction compensation is developed to achieve accurate and stable tracking for fast moving target. The nonlinear observer and slide mode controller based on modified LuGre model with friction compensation can effectively reduce the influence of nonlinear friction and disturbance of this servo system. The stability of the closed-loop system is guaranteed by Lyapunov theory. The steady-state error of the system is eliminated by integral action. The adaptive integral backstepping sliding mode controller and its performance are validated by a nonlinear modified LuGre dynamic model of the opto-electronic tracking system in simulation and practical experiments. The experiment results demonstrate that the proposed controller can effectively realise the accuracy and stability control of opto-electronic tracking system.

Controlling chaos in a nonlinear pendulum using an extended time-delayed feedback control method

International Nuclear Information System (INIS)

Souza de Paula, Aline; Savi, Marcelo Amorim

2009-01-01

Chaos control is employed for the stabilization of unstable periodic orbits (UPOs) embedded in chaotic attractors. The extended time-delayed feedback control uses a continuous feedback loop incorporating information from previous states of the system in order to stabilize unstable orbits. This article deals with the chaos control of a nonlinear pendulum employing the extended time-delayed feedback control method. The control law leads to delay-differential equations (DDEs) that contain derivatives that depend on the solution of previous time instants. A fourth-order Runge-Kutta method with linear interpolation on the delayed variables is employed for numerical simulations of the DDEs and its initial function is estimated by a Taylor series expansion. During the learning stage, the UPOs are identified by the close-return method and control parameters are chosen for each desired UPO by defining situations where the largest Lyapunov exponent becomes negative. Analyses of a nonlinear pendulum are carried out by considering signals that are generated by numerical integration of the mathematical model using experimentally identified parameters. Results show the capability of the control procedure to stabilize UPOs of the dynamical system, highlighting some difficulties to achieve the stabilization of the desired orbit.

A systems based experimental approach to tactile friction

NARCIS (Netherlands)

Masen, Marc Arthur

2011-01-01

This work focuses on the friction in contacts where the human finger pad is one of the interacting surfaces. This ‘tactile friction’ requires a full understanding of the contact mechanics and the behaviour of human skin. The coefficient of friction cannot be considered as a property of the skin

Development and Verification of the Tire/Road Friction Estimation Algorithm for Antilock Braking System

Directory of Open Access Journals (Sweden)

Jian Zhao

2014-01-01

Full Text Available Road friction information is very important for vehicle active braking control systems such as ABS, ASR, or ESP. It is not easy to estimate the tire/road friction forces and coefficient accurately because of the nonlinear system, parameters uncertainties, and signal noises. In this paper, a robust and effective tire/road friction estimation algorithm for ABS is proposed, and its performance is further discussed by simulation and experiment. The tire forces were observed by the discrete Kalman filter, and the road friction coefficient was estimated by the recursive least square method consequently. Then, the proposed algorithm was analysed and verified by simulation and road test. A sliding mode based ABS with smooth wheel slip ratio control and a threshold based ABS by pulse pressure control with significant fluctuations were used for the simulation. Finally, road tests were carried out in both winter and summer by the car equipped with the same threshold based ABS, and the algorithm was evaluated on different road surfaces. The results show that the proposed algorithm can identify the variation of road conditions with considerable accuracy and response speed.

Friction Material Composites Materials Perspective

CERN Document Server

Sundarkrishnaa, K L

2012-01-01

Friction Material Composites is the first of the five volumes which strongly educates and updates engineers and other professionals in braking industries, research and test labs. It explains besides the formulation of design processes and its complete manufacturing input. This book gives an idea of mechanisms of friction and how to control them by designing .The book is  useful for designers  of automotive, rail and aero industries for designing the brake systems effectively with the integration of friction material composite design which is critical. It clearly  emphasizes the driving  safety and how serious designers should  select the design input. The significance of friction material component like brake pad or a liner as an integral part of the brake system of vehicles is explained. AFM pictures at nanolevel illustrate broadly the explanations given.

Studies on internal friction in electron-irradiated iron crystals after plastic deformation

International Nuclear Information System (INIS)

Wolf, J.

1986-01-01

For the analysis of atomic point defects in high-purity the generation of atomic point defects was, above all, carried out by electron radiation, but in addition, also by plastic deformation. The exposure to radiation was realized at different temperatures in the Dynamitron of the University of Stuttgart (80 K, 160 K) and also in the low-temperature radiation facility of the nuclear research plant (KfA) Juelich (50 K). The radiation doses ranged between 2.7.10 21 e - /m 2 and 1.0.10 23 e - /m 2 . In situ plastic deformation was achieved at about 80 K (torsion, 4%). Internal friction which was determined in an inverse torsion pendulum in the temperature range of 80 K - 700 K and at frequencies of about 1 Hz served as defect indicator. In this study simulation programs were developed which were to give information prior to the realization of measurements on the temperatures and the intensity of the damping peaks to be expected. The internal friction peaks measured in the framework of this study could be assigned to the recovery stages I-IV. The measured values were discussed for three temperature ranges with main emphasis on the investigation of the recovering, radiation-induced or deformation-induced, atomic point defect in the temperature range of the recovery stage III (200 K - 270 K). (orig./MM) [de

Reduction of Noise from Disc Brake Systems Using Composite Friction Materials Containing Thermoplastic Elastomers (TPEs)

Science.gov (United States)

Masoomi, Mohsen; Katbab, Ali Asghar; Nazockdast, Hossein

2006-09-01

Attempts have been made for the first time to prepare a friction material with the characteristic of thermal sensitive modulus, by the inclusion of thermoplastic elastomers (TPE) as viscoelastic polymeric materials into the formulation in order to the increase the damping behavior of the cured friction material. Styrene butadiene styrene (SBS), styrene ethylene butylene styrene (SEBS) and nitrile rubber/polyvinyl chloride (NBR/PVC) blend system were used as TPE materials. In order to evaluate the viscoelastic parameters such as loss factor (tan δ) and storage modulus (E‧) for the friction material, dynamic mechanical analyzer (DMA) were used. Natural frequencies and mode shapes of friction material and brake disc were determined by modal analysis. However, NBR/PVC and SEBS were found to be much more effective in damping behavior. The results from this comparative study suggest that the damping characteristics of commercial friction materials can be strongly affected by the TPE ingredients. This investigation also confirmed that the specimens with high TPE content had low noise propensity.

Slip safety risk analysis of surface properties using the coefficients of friction of rocks.

Science.gov (United States)

Çoşkun, Gültekin; Sarıışık, Gencay; Sarıışık, Ali

2017-12-19

This study was conducted to determine the most appropriate surface processing techniques (SPT), environmental conditions (EC) and surface roughness (SR) to minimize the risk of slipping when pedestrians walk on a floor covering of rocks barefoot and with shoes. Coefficients of friction (COFs) and values of SR were found using five different types of rocks, four SPT and two (ramp and pendulum) tests. Results indicate that the parameters which affect the COF values of rocks include SR, EC and SPT. Simple linear regression was performed to examine the relationship between the values of the COF and the SR. The value of the COF was identified as R 2  ≥ 0.864. Statistical results, which are based on experimental measurements, show that rocks are classified according to their safe use areas depending on their COF and SR values.

Assessment of semi-active friction dampers

Science.gov (United States)

dos Santos, Marcelo Braga; Coelho, Humberto Tronconi; Lepore Neto, Francisco Paulo; Mafhoud, Jarir

2017-09-01

The use of friction dampers has been widely proposed for a variety of mechanical systems for which applying viscoelastic materials, fluid based dampers or other viscous dampers is impossible. An important example is the application of friction dampers in aircraft engines to reduce the blades' vibration amplitudes. In most cases, friction dampers have been studied in a passive manner, but significant improvements can be achieved by controlling the normal force in the contact region. The aim of this paper is to present and study five control strategies for friction dampers based on three different hysteresis cycles by using the Harmonic Balance Method (HBM), a numerical and experimental analysis. The first control strategy uses the friction force as a resistance when the system is deviating from its equilibrium position. The second control strategy maximizes the energy removal in each harmonic oscillation cycle by calculating the optimal normal force based on the last displacement peak. The third control strategy combines the first strategy with the homogenous modulation of the friction force. Finally, the last two strategies attempt to predict the system's movement based on its velocity and acceleration and our knowledge of its physical properties. Numerical and experimental studies are performed with these five strategies, which define the performance metrics. The experimental testing rig is fully identified and its parameters are used for numerical simulations. The obtained results show the satisfactory performance of the friction damper and selected strategy and the suitable agreement between the numerical and experimental results.

Galileo and the Pendulum: Latching on to Time

Science.gov (United States)

Machamer, Peter; Hepburn, Brian

2004-01-01

Galileo changed the very concepts or categories by which natural philosophy could deal with matter and motion. Central to these changes was his introduction of time as a fundamental concept. He worked with the pendulum and with the inclined plane to discover his new concept of motion. Both of these showed him that acceleration and time were…

Energy harvester for rotating environments using offset pendulum and nonlinear dynamics

International Nuclear Information System (INIS)

Roundy, Shad; Tola, Jeffry

2014-01-01

We present an energy harvester for environments that rotate through the Earth’s gravitational field. Example applications include shafts connected to motors, axles, propellers, fans, and wheels or tires. Our approach uses the unique dynamics of an offset pendulum along with a nonlinear bistable restoring spring to improve the operational bandwidth of the system. Depending on the speed of the rotating environment, the system can act as a bistable oscillator, monostable stiffening oscillator, or linear oscillator. We apply our approach to a tire pressure monitoring system mounted on a car rim. Simulation and experimental test results show that the prototype generator is capable of directly powering an RF transmission every 60 s or less over a speed range of 10 to 155 kph. (paper)

Energy harvester for rotating environments using offset pendulum and nonlinear dynamics

Science.gov (United States)

Roundy, Shad; Tola, Jeffry

2014-10-01

We present an energy harvester for environments that rotate through the Earth’s gravitational field. Example applications include shafts connected to motors, axles, propellers, fans, and wheels or tires. Our approach uses the unique dynamics of an offset pendulum along with a nonlinear bistable restoring spring to improve the operational bandwidth of the system. Depending on the speed of the rotating environment, the system can act as a bistable oscillator, monostable stiffening oscillator, or linear oscillator. We apply our approach to a tire pressure monitoring system mounted on a car rim. Simulation and experimental test results show that the prototype generator is capable of directly powering an RF transmission every 60 s or less over a speed range of 10 to 155 kph.

Flow Friction or Spontaneous Ignition?

Science.gov (United States)

Stoltzfus, Joel M.; Gallus, Timothy D.; Sparks, Kyle

2012-01-01

"Flow friction," a proposed ignition mechanism in oxygen systems, has proved elusive in attempts at experimental verification. In this paper, the literature regarding flow friction is reviewed and the experimental verification attempts are briefly discussed. Another ignition mechanism, a form of spontaneous combustion, is proposed as an explanation for at least some of the fire events that have been attributed to flow friction in the literature. In addition, the results of a failure analysis performed at NASA Johnson Space Center White Sands Test Facility are presented, and the observations indicate that spontaneous combustion was the most likely cause of the fire in this 2000 psig (14 MPa) oxygen-enriched system.

Friction and dissipative phenomena in quantum mechanics

International Nuclear Information System (INIS)

Kostin, M.D.

1975-01-01

Frictional and dissipative terms of the Schroedinger equation are studied. A proof is given showing that the frictional term of the Schroedinger--Langevin equation causes the quantum system to lose energy. General expressions are derived for the frictional term of the Schroedinger equation. (U.S.)

Foucault's pendulum, a classical analog for the electron spin state

Science.gov (United States)

Linck, Rebecca A.

Spin has long been regarded as a fundamentally quantum phenomena that is incapable of being described classically. To bridge the gap and show that aspects of spin's quantum nature can be described classically, this work uses a classical Lagrangian based on the coupled oscillations of Foucault's pendulum as an analog for the electron spin state in an external magnetic field. With this analog it is possible to demonstrate that Foucault's pendulum not only serves as a basis for explaining geometric phase, but is also a basis for reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured electron spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

Development of Friction Pendulum System to Reduce the Seismic Force

International Nuclear Information System (INIS)

Jang, J. B.; Kim, J. K.; Hwang, K. M.; Kwon, H. O.; Lee, C. W

2007-01-01

Most of the damages in electrical facilities are occurred at transformer due to the great earthquake. The damage types of transformer are the failure of upper bushing of transformer, overturning of transformer due to geometry with high height, and the failure of anchorage of transformer. The objective of this study is to develop the seismic isolator to prevent the damage of transformer due to earthquake considering the importance of transformer

Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring Systems

Science.gov (United States)

Bentley, Nicole; Brower, David; Le, Suy Q.; Seaman, Calvin; Tang, Henry

2017-01-01

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system that can be deployed on existing subsea structures. This paper provides a summary of the design concept, prototype development, prototype performance testing, and design refinements of the device. The results of the laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are included in this paper. Limitations of the initial design were identified and future design improvements were proposed. These new features will enhance the coupling of the device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on subsea structures, flowlines or risers. The work described in this paper investigates the design of a friction-based coupling device (friction clamp), which is applicable for pipelines and structures that are suspended in the water column and those that are resting on the seabed. The monitoring elements consist of fiber-optic sensors that are bonded to a metal clamshell with a high-friction coating. The friction clamp has a single hinge design to facilitate the operation of the clamp and dual rows of opposing fasteners to distribute the clamping force on the structure. The friction clamp can be installed by divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain

Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications

Science.gov (United States)

Bentley, Nicole L.; Brower, David V.; Le, Suy Q.; Seaman, Calvin H.; Tang, Henry H.

2017-01-01

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system capable of measuring pressure, strain, and temperature that can be deployed on existing subsea structures. A summary is provided of the design concept, prototype development, prototype performance testing, and subsequent design refinements of the device. The results of laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are also included. Limitations of the initial concept were identified during testing and future design improvements were proposed and later implemented. These new features enhance the coupling of the sensor device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on flowlines, risers, and other subsea structures. The work described in this paper investigates the design and test of a friction-based coupling device (herein referred to as a friction clamp) which is suitable for pipelines and structures that are suspended in the water column as well as for those that are resting on the seabed. The monitoring elements consist of fiberoptic sensors that are bonded to a stainless steel clamshell assembly with a high-friction surface coating. The friction clamp incorporates a single hinge design to facilitate installation of the clamp and dual rows of opposing fasteners to distribute the clamping force along the structure. The friction clamp can be modified to be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating

Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring System

Science.gov (United States)

Bentley, Nicole L.; Brower, David V.; Le, Suy Q.; Seaman, Calvin H.; Tang, Henry H.

2017-01-01

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system that can be deployed on existing subsea structures. This paper provides a summary of the design concept, prototype development, prototype performance testing, and design refinements of the device. The results of the laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are included in this paper. Limitations of the initial design were identified and future design improvements were proposed. These new features will enhance the coupling of the device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on subsea structures, flowlines or risers. The work described in this paper investigates the design of a friction-based coupling device (friction clamp), which is applicable for pipelines and structures that are suspended in the water column and those that are resting on the seabed. The monitoring elements consist of fiber-optic sensors that are bonded to a metal clamshell with a high-friction coating. The friction clamp has a single hinge design to facilitate the operation of the clamp and dual rows of opposing fasteners to distribute the clamping force on the structure. The friction clamp can be installed by divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain

Friction interface mechanics and self-induced vibrations

OpenAIRE

Wernitz, Boris Alexander

2013-01-01

Vibrations in braking systems have been studied since the beginning of the last century and despite several insights, still many phenomena, particularly in the area of friction induced vibrations, are not fully understood. The objective of the actual study was the identification of the complex dynamics in the friction interface of a dry friction brake system. In this context, particular consideration was given to the generation of instabilities and brake squeal. In work presently being ...

Friction measurement in a hip wear simulator.

Science.gov (United States)

Saikko, Vesa

2016-05-01

A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated. © IMechE 2016.

A trigonometric approximation for the tension in the string of a simple pendulum accurate for all amplitudes

International Nuclear Information System (INIS)

Lima, F M S

2009-01-01

In a previous work, O'Connell (Phys. Teach. 40, 24 (2002)) investigated the time dependence of the tension in the string of a simple pendulum oscillating within the small-angle regime. In spite of the approximation sin θ ∼ θ being accurate only for amplitudes below 7 deg., his experimental results are for a pendulum oscillating with an amplitude of about 18 deg., therefore beyond the small-angle regime. This lapse may also be found in some textbooks, laboratory manuals and internet. By noting that the exact analytical solution for this problem involves the so-called Jacobi elliptic functions, which are unknown to most students (even instructors), I take into account a sinusoidal approximate solution for the pendulum equation I introduced in a recent work (Eur. J. Phys. 29 1091 (2008)) for deriving a simple trigonometric approximation for the tension valid for all possible amplitudes. This approximation is compared to both the O'Connell and the exact results, revealing that it is accurate enough for analysing large-angle pendulum experiments. (letters and comments)

The Nonsmooth Vibration of a Relative Rotation System with Backlash and Dry Friction

Directory of Open Access Journals (Sweden)

Minjia He

2017-01-01

Full Text Available We investigate a relative rotation system with backlash and dry friction. Firstly, the corresponding nonsmooth characters are discussed by the differential inclusion theory, and the analytic conditions for stick and nonstick motions are developed to understand the motion switching mechanism. Based on such analytic conditions of motion switching, the influence of the maximal static friction torque and the driving torque on the stick motion is studied. Moreover, the sliding time bifurcation diagrams, duty cycle figures, time history diagrams, and the K-function time history diagram are also presented, which confirm the analytic results. The methodology presented in this paper can be applied to predictions of motions in nonsmooth dynamical systems.

Torsion pendulum for the performance test of the inertial sensor for ASTROD-I

International Nuclear Information System (INIS)

Zhou, Z B; Gao, S W; Luo, J

2005-01-01

A torsion pendulum facility for a ground-based performance test of the inertial sensor for ASTROD-1 has been constructed. The twist motion of the test mass is monitored and servo-controlled. The sensitivity of the electrostatic servo-controlled actuator is calibrated based on the elastic torque of the torsion fibre, and the torque resolution of the servo-controlled torsion pendulum comes to 2 x 10 -11 N m Hz -1/2 from 1 mHz to 0.1 Hz, which is likely limited by the seismic noise, electronic noise and the cross coupling between the translation and twist modes

Real-Time Demonstration of the Main Characteristics of Chaos in the Motion of a Real Double Pendulum

Science.gov (United States)

Vadai, Gergely; Gingl, Zoltan; Mellar, Janos

2012-01-01

Several studies came to the conclusion that chaotic phenomena are worth including in high school and undergraduate education. The double pendulum is one of the simplest systems that is chaotic; therefore, numerical simulations and theoretical studies of it have been given large publicity, and thanks to its spectacular motion, it has become one of…

Modeling Friction in Modelica with the Lund-Grenoble Friction Model

OpenAIRE

Aberger, Martin; Otter, Martin

2002-01-01

The properties of the Lund-Grenoble friction model are summarized and different types of friction elements - bearing friction, clutch, one-way clutch, are implemented in Modelica using this friction formulation. The dynamic properties of these components are determined in simulations and compared with the friction models available in the Modelica standard library. This includes also an automatic gearbox model where 6 friction elements are coupled dynamically.

Velocity Dependence in the Cyclic Friction Arising with Gears

OpenAIRE

García Armada, Elena; González de Santos, Pablo; Canudas de Wit, Carlos

2002-01-01

Recent research on friction in robot joints and transmission systems has considered meshing friction a position-dependent friction component. However, in this paper we show experimental evidence that meshing friction depends highly on joint speed.We identify the meshing friction in the gearboxes of a robotic leg, and we propose a new mathematical model that considers the rate dependency of meshing friction. The resulting model is validated through experimentation. Results...

Frictional Resistance of Three Types of Ceramic Brackets

Directory of Open Access Journals (Sweden)

Claire L Williams

2014-01-01

Full Text Available Objectives: To investigate the static frictional resistance at the bracket/archwire interface in two recently introduced bracket systems and compare them to conventional ceramic and conventional metal bracket systems. Three variables were considered including the bracket system, archwire type and archwire angulation. Material and Methods: Four bracket systems were tested in vitro: Self ligating ceramic, ceramic with metal slot and module, conventional ceramic with module and conventional metal with module. A specially constructed jig and an Instron testing machine were used to measure the static frictional resistance for 0.014 inches round and 0.018 x 0.025 inches rectangular stainless steel wires at 0° and 7° angulations. Main outcome measures: static frictional force at the bracket/archwire interface; recorded and measured in units of force (Newtons. Results: Self ligating ceramic and metal slot ceramic bracket systems generated significantly less static frictional resistance than conventional ceramic bracket systems with the wire at both angulations (P < 0.05. Changing the wire from 0.014 round to 0.018 x 0.025 rectangular wire significantly increased frictional forces for metal slot ceramic and conventional metal bracket systems (P < 0.01. Increasing wire angulation significantly increased frictional resistance at the bracket/archwire interface for all four types of bracket systems tested (P < 0.001. Conclusions: Compared to conventional ceramic, self ligating ceramic and metal slot ceramic bracket systems should give improved clinical performance, matching that of conventional metal brackets.

Determination of the Optimal Position of Pendulums of an Active Self-balancing Device

OpenAIRE

Ziyakaev, Gregory Rakitovich; Kazakova, Oksana Aleksandrovna; Yankov, V. V.; Ivkina, O. P.

2017-01-01

The demand of the modern manufacturing industry for machines with high motion speed leads to increased load and vibration activity of the main elements of rotor systems. Vibration reduces operating life of bearings, has adversary effects on human organism, and can cause accidents. One way to compensate for a rotating rotor's imbalance is the use of active self-balancing devices. The aim of this work is to determine the position of their pendulums, in which the imbalance is minimized. As a res...

The effect of friction in coulombian damper

Science.gov (United States)

Wahad, H. S.; Tudor, A.; Vlase, M.; Cerbu, N.; Subhi, K. A.

2017-02-01

The study aimed to analyze the damping phenomenon in a system with variable friction, Stribeck type. Shock absorbers with limit and dry friction, is called coulombian shock-absorbers. The physical damping vibration phenomenon, in equipment, is based on friction between the cushioning gasket and the output regulator of the shock-absorber. Friction between them can be dry, limit, mixture or fluid. The friction is depending on the contact pressure and lubricant presence. It is defined dimensionless form for the Striebeck curve (µ friction coefficient - sliding speed v). The friction may damp a vibratory movement or can maintain it (self-vibration), depending on the µ with v (it can increase / decrease or it can be relative constant). The solutions of differential equation of movement are obtained for some work condition of one damper for automatic washing machine. The friction force can transfer partial or total energy or generates excitation energy in damper. The damping efficiency is defined and is determined analytical for the constant friction coefficient and for the parabolic friction coefficient.

Switching sliding mode force tracking control of piezoelectric-hydraulic pump-based friction element actuation systems for automotive transmissions

Science.gov (United States)

Kim, Gi-Woo; Wang, K. W.

2009-08-01

In this study, a nonlinear sliding-mode controller is designed for force tracking of a piezoelectric-hydraulic pump (PHP)-based actuation system, which is developed to replace the current electro-hydraulic actuation systems for automatic transmission (AT) friction elements, such as band brakes or clutches. By utilizing the PHP, one can eliminate the various hydraulic components (oil pump, regulating valve and control valve) in current ATs and achieve a simpler configuration with more efficient operation. With the derived governing equation of motion of the PHP-based actuation system integrated with the friction element (band brake), a switching control law is synthesized based on the sliding-mode theory. To evaluate the effectiveness of the proposed control law, its force tracking performance for the engagement of a friction element during an AT 1\\to 2 up-shift is examined experimentally. It is shown that one can successfully track the desired force trajectory for AT shift control with small tracking error. This study demonstrates the potential of the PHP as a new controllable actuation system for AT friction elements.

Switching sliding mode force tracking control of piezoelectric-hydraulic pump-based friction element actuation systems for automotive transmissions

International Nuclear Information System (INIS)

Kim, Gi-Woo; Wang, K W

2009-01-01

In this study, a nonlinear sliding-mode controller is designed for force tracking of a piezoelectric-hydraulic pump (PHP)-based actuation system, which is developed to replace the current electro-hydraulic actuation systems for automatic transmission (AT) friction elements, such as band brakes or clutches. By utilizing the PHP, one can eliminate the various hydraulic components (oil pump, regulating valve and control valve) in current ATs and achieve a simpler configuration with more efficient operation. With the derived governing equation of motion of the PHP-based actuation system integrated with the friction element (band brake), a switching control law is synthesized based on the sliding-mode theory. To evaluate the effectiveness of the proposed control law, its force tracking performance for the engagement of a friction element during an AT 1→2 up-shift is examined experimentally. It is shown that one can successfully track the desired force trajectory for AT shift control with small tracking error. This study demonstrates the potential of the PHP as a new controllable actuation system for AT friction elements

An Experiment on a Physical Pendulum and Steiner's Theorem

Science.gov (United States)

Russeva, G. B.; Tsutsumanova, G. G.; Russev, S. C.

2010-01-01

Introductory physics laboratory curricula usually include experiments on the moment of inertia, the centre of gravity, the harmonic motion of a physical pendulum, and Steiner's theorem. We present a simple experiment using very low cost equipment for investigating these subjects in the general case of an asymmetrical test body. (Contains 3 figures…

Optical Foucault Pendulum: photons and the Coriolis effect

Science.gov (United States)

Rogers, Charles; Selvaggi, Richard

2012-10-01

Consider the motion of photons within a rotating photon clock. Will light behave as a particle as it reflects back and forth between two parallel mirrors rotating in a manner similar to the motion of a Foucault pendulum? An experiment to measure the trajectory of light in a rotating cavity is presented. Implementation details for this experiment and initial data collected are also reported.

Gas desorption during friction of amorphous carbon films

International Nuclear Information System (INIS)

Rusanov, A; Fontaine, J; Martin, J-M; Mogne, T L; Nevshupa, R

2008-01-01

Gas desorption induced by friction of solids, i.e. tribodesorption, is one of the numerous physical and chemical phenomena, which arise during friction as result of thermal and structural activation of material in a friction zone. Tribodesorption of carbon oxides, hydrocarbons, and water vapours may lead to significant deterioration of ultra high vacuum conditions in modern technological equipment in electronic, optoelectronic industries. Therefore, knowledge of tribodesorption is crucial for the performance and lifetime of vacuum tribosystems. Diamond-like carbon (DLC) coatings are interesting materials for vacuum tribological systems due to their high wear resistance and low friction. Highly hydrogenated amorphous carbon (a-C:H) films are known to exhibit extremely low friction coefficient under high vacuum or inert environment, known as 'superlubricity' or 'superlow friction'. However, the superlow friction period is not always stable and then tends to spontaneous transition to high friction. It is supposed that hydrogen supply from the bulk to the surface is crucial for establishing and maintaining superlow friction. Thus, tribodesorption can serve also as a new technique to determine the role of gases in superlow friction mechanisms. Desorption of various a-C:H films, deposited by PECVD, ion-beam deposition and deposition using diode system, has been studied by means of ultra-high vacuum tribometer equipped with a mass spectrometer. It was found that in superlow friction period desorption rate was below the detection limit in the 0-85 mass range. However, transition from superlow friction to high friction was accompanied by desorption of various gases, mainly of H 2 and CH 4 . During friction transition, surfaces were heavily damaged. In experiments with DLC films with low hydrogen content tribodesorption was significant during the whole experiment, while low friction was not observed. From estimation of maximum surface temperature during sliding contact it

Cooperative and submolecular dissipation mechanisms of sliding friction in complex organic systems.

Science.gov (United States)

Knorr, Daniel B; Gray, Tomoko O; Overney, René M

2008-08-21

Energy dissipation in single asperity sliding friction was directly linked to submolecular modes of mobility by intrinsic friction analysis, involving time-temperature superposition along with thermodynamic stress and reaction rate models. Thereby, polystyrene served as a representative tribological sample for organic and amorphous complex systems. This study reveals the significance of surface and subsurface (alpha-, beta-, and gamma-) relaxational modes, which couple under appropriate external conditions (load, temperature, and rate) with shear induced disturbances, and thus gives rise to material specific frictional dissipation. At low pressures and temperatures below the glass transition point, the phenyl pendant side groups of polystyrene, known for their preferential orientation at the free surface, were noticed to be the primary channel for dissipation of kinetic sliding-energy. While this process was found to be truly enthalpic (activation energy of 8 kcalmol), energy dissipation was shown to possess both enthalpic and cooperative entropic contributions above the loading capacity of the surface phenyl groups (9.9 kcalmol) or above the glass transition. Apparent Arrhenius activation energies of frictional dissipation of 22 and 90 kcalmol, respectively, and cooperative contributions up to 80% were found. As such, this study highlights issues critical to organic lubricant design, i.e., the intrinsic enthalpic activation barriers of mobile linker groups, the evaluation of cooperative mobility phenomena, and critical tribological parameters to access or avoid coupling between shear disturbances and molecular actuators.

Friction and anchorage loading revisited.

Science.gov (United States)

Dholakia, Kartik D

2012-01-01

Contemporary concepts of sliding mechanics explain that friction is inevitable. To overcome this frictional resistance, excess force is required to retract the tooth along the archwire (ie, individual retraction of canines, en masse retraction of anterior teeth), in addition to the amount of force required for tooth movement. The anterior tooth retraction force, in addition to excess force (to overcome friction), produces reciprocal protraction force on molars, thereby leading to increased anchorage loading. However, this traditional concept was challenged in recent literature, which was based on the finite element model, but did not bear correlation to the clinical scenario. This article will reinforce the fact that clinically, friction increases anchorage loading in all three planes of space, considering the fact that tooth movement is a quasistatic process rather than a purely continuous or static one, and that conventional ways of determining the effects of static or dynamic friction on anchorage load cannot be applied to clinical situations (which consist of anatomical resistance units and a complex muscular force system). The article does not aim to quantify friction and its effect on the amount of anchorage load. Rather, a new perspective regarding the role of various additional factors (which is not explained by contemporary concept) that may influence friction and anchorage loading is provided..

Nonlinear friction dynamics on polymer surface under accelerated movement

Directory of Open Access Journals (Sweden)

Yuuki Aita

2017-04-01

Full Text Available Nonlinear phenomena on the soft material surface are one of the most exciting topics of chemical physics. However, only a few reports exist on the friction phenomena under accelerated movement, because friction between two solid surfaces is considered a linear phenomenon in many cases. We aim to investigate how nonlinear accelerated motion affects friction on solid surfaces. In the present study, we evaluate the frictional forces between two polytetrafluoroethylene (PTFE resins using an advanced friction evaluation system. On PTFE surfaces, the normalized delay time δ, which is the time lag in the response of the friction force to the accelerated movement, is observed in the pre-sliding friction process. Under high-velocity conditions, kinetic friction increases with velocity. Based on these experimental results, we propose a two-phase nonlinear model including a pre-sliding process (from the beginning of sliding of a contact probe to the establishment of static friction and a kinetic friction process. The present model consists of several factors including velocity, acceleration, stiffness, viscosity, and vertical force. The findings reflecting the viscoelastic properties of soft material is useful for various fields such as in the fabrication of clothes, cosmetics, automotive materials, and virtual reality systems as well as for understanding friction phenomena on soft material surfaces.

Argo packing friction research update

International Nuclear Information System (INIS)

VanTassell, D.M.

1994-01-01

This paper focuses on the issue of valve packing friction and its affect on the operability of motor- and air-operated valves (MOVs and AOVs). At this time, most nuclear power plants are required to perform postmaintenance testing following a packing adjustment or replacement. In many cases, the friction generated by the packing does not impact the operability window of a valve. However, to date there has not been a concerted effort to substantiate this claim. To quantify the effects of packing friction, it has become necessary to develop a formula to predict the friction effects accurately. This formula provides a much more accurate method of predicting packing friction than previously used factors based strictly on stem diameter. Over the past 5 years, Argo Packing Company has been developing and testing improved graphite packing systems at research facilities, such as AECL Chalk River and Wyle Laboratories. Much of this testing has centered around reducing and predicting friction that is related to packing. In addition, diagnostic testing for Generic Letter 89-10 MOVs and AOVs has created a significant data base. In July 1992 Argo asked several utilities to provide running load data that could be used to quantify packing friction repeatability and predictability. This technical paper provides the basis to predict packing friction, which will improve calculations for thrust requirements for Generic Leter 89-10 and future AOV programs. In addition, having an accurate packing friction formula will improve packing performance when low running loads are identified that would indicate insufficient sealing force

Amontonian frictional behaviour of nanostructured surfaces.

Science.gov (United States)

Pilkington, Georgia A; Thormann, Esben; Claesson, Per M; Fuge, Gareth M; Fox, Oliver J L; Ashfold, Michael N R; Leese, Hannah; Mattia, Davide; Briscoe, Wuge H

2011-05-28

With nanotextured surfaces and interfaces increasingly being encountered in technological and biomedical applications, there is a need for a better understanding of frictional properties involving such surfaces. Here we report friction measurements of several nanostructured surfaces using an Atomic Force Microscope (AFM). These nanostructured surfaces provide well defined model systems on which we have tested the applicability of Amontons' laws of friction. Our results show that Amontonian behaviour is observed with each of the surfaces studied. However, no correlation has been found between measured friction and various surface roughness parameters such as average surface roughness (R(a)) and root mean squared (rms) roughness. Instead, we propose that the friction coefficient may be decomposed into two contributions, i.e., μ = μ(0) + μ(g), with the intrinsic friction coefficient μ(0) accounting for the chemical nature of the surfaces and the geometric friction coefficient μ(g) for the presence of nanotextures. We have found a possible correlation between μ(g) and the average local slope of the surface nanotextures. This journal is © the Owner Societies 2011

Nuclear friction and chaotic motion

International Nuclear Information System (INIS)

Srokowski, T.; Szczurek, A.; Drozdz, S.

1990-01-01

The concept of nuclear friction is considered from the point of view of regular versus chaotic motion in an atomic nucleus. Using a realistic nuclear Hamiltonian it is explicitly shown that the frictional description of the gross features of nuclear collisions is adequate if the system behaves chaotically. Because of the core in the Hamiltonian, the three-body nuclear system already reveals a structure of the phase space rich enough for this concept to be applicable

Controlled damping of a physical pendulum: experiments near critical conditions

International Nuclear Information System (INIS)

Gonzalez, Manuel I; Bol, Alfredo

2006-01-01

This paper presents an experimental device for the study of damped oscillatory motion along with three associated experiments. Special emphasis is given on both didactic aspects and the interactivity of the experimental set-up, in order to assist students in understanding fundamental aspects of damped oscillatory motion and allow them to directly compare their experimental results with the well-known theory they can find in textbooks. With this in mind, a physical pendulum was selected with an eddy-current damping system that allows the damping conditions to be controlled with great precision. The three experiments examine accurate control of damping, frequency shift near critical damping and the transition from underdamped to overdamped conditions

A Physics-Based Rock Friction Constitutive Law: Steady State Friction

Science.gov (United States)

Aharonov, Einat; Scholz, Christopher H.

2018-02-01

Experiments measuring friction over a wide range of sliding velocities find that the value of the friction coefficient varies widely: friction is high and behaves according to the rate and state constitutive law during slow sliding, yet markedly weakens as the sliding velocity approaches seismic slip speeds. We introduce a physics-based theory to explain this behavior. Using conventional microphysics of creep, we calculate the velocity and temperature dependence of contact stresses during sliding, including the thermal effects of shear heating. Contacts are assumed to reach a coupled thermal and mechanical steady state, and friction is calculated for steady sliding. Results from theory provide good quantitative agreement with reported experimental results for quartz and granite friction over 11 orders of magnitude in velocity. The new model elucidates the physics of friction and predicts the connection between friction laws to independently determined material parameters. It predicts four frictional regimes as function of slip rate: at slow velocity friction is either velocity strengthening or weakening, depending on material parameters, and follows the rate and state friction law. Differences between surface and volume activation energies are the main control on velocity dependence. At intermediate velocity, for some material parameters, a distinct velocity strengthening regime emerges. At fast sliding, shear heating produces thermal softening of friction. At the fastest sliding, melting causes further weakening. This theory, with its four frictional regimes, fits well previously published experimental results under low temperature and normal stress.

Internal rotor friction instability

Science.gov (United States)

Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

1990-01-01

The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

Double pendulum model for a tennis stroke including a collision process

Science.gov (United States)

Youn, Sun-Hyun

2015-10-01

By means of adding a collision process between the ball and racket in the double pendulum model, we analyzed the tennis stroke. The ball and the racket system may be accelerated during the collision time; thus, the speed of the rebound ball does not simply depend on the angular velocity of the racket. A higher angular velocity sometimes gives a lower rebound ball speed. We numerically showed that the proper time-lagged racket rotation increased the speed of the rebound ball by 20%. We also showed that the elbow should move in the proper direction in order to add the angular velocity of the racket.

Rubber friction and tire dynamics

International Nuclear Information System (INIS)

Persson, B N J

2011-01-01

We propose a simple rubber friction law, which can be used, for example, in models of tire (and vehicle) dynamics. The friction law is tested by comparing numerical results to the full rubber friction theory (Persson 2006 J. Phys.: Condens. Matter 18 7789). Good agreement is found between the two theories. We describe a two-dimensional (2D) tire model which combines the rubber friction model with a simple mass-spring description of the tire body. The tire model is very flexible and can be used to accurately calculate μ-slip curves (and the self-aligning torque) for braking and cornering or combined motion (e.g. braking during cornering). We present numerical results which illustrate the theory. Simulations of anti-blocking system (ABS) braking are performed using two simple control algorithms.

Rubber friction and tire dynamics.

Science.gov (United States)

Persson, B N J

2011-01-12

We propose a simple rubber friction law, which can be used, for example, in models of tire (and vehicle) dynamics. The friction law is tested by comparing numerical results to the full rubber friction theory (Persson 2006 J. Phys.: Condens. Matter 18 7789). Good agreement is found between the two theories. We describe a two-dimensional (2D) tire model which combines the rubber friction model with a simple mass-spring description of the tire body. The tire model is very flexible and can be used to accurately calculate μ-slip curves (and the self-aligning torque) for braking and cornering or combined motion (e.g. braking during cornering). We present numerical results which illustrate the theory. Simulations of anti-blocking system (ABS) braking are performed using two simple control algorithms.

Experimental analysis of the influence of damping on the resonance behavior of a spherical pendulum

Czech Academy of Sciences Publication Activity Database

Pospíšil, Stanislav; Fischer, Cyril; Náprstek, Jiří

2014-01-01

Roč. 78, č. 1 (2014), s. 371-390 ISSN 0924-090X R&D Projects: GA ČR(CZ) GC13-34405J Grant - others:NSC(TW) 101WFD0400131 Institutional support: RVO:68378297 Keywords : auto -parametric system * experimental verification * spherical pendulum * stability of semi-trivial solution Subject RIV: JM - Building Engineering Impact factor: 2.849, year: 2014 http://link.springer.com/article/10.1007%2Fs11071-014-1446-6#page-1

Analysis of the NASA White Sands Test Facility (WSTF) Test System for Friction-Ignition of Metallic Materials

Science.gov (United States)

Shoffstall, Michael S.; Wilson, D. Bruce; Stoltzfus, Joel M.

2000-01-01

Friction is a known ignition source for metals in oxygen-enriched atmospheres. The test system developed by the NASA White Sands Test Facility in response to ASTM G-94 has been used successfully to determine the relative ignition from friction of numerous metallic materials and metallic materials pairs. These results have been ranked in terms of a pressure-velocity product (PV) as measured under the prescribed test conditions. A high value of 4.1(exp 8) watts per square meter for Inconel MA 754 is used to imply resistance to friction ignition, whereas a low value of 1.04(exp 8) watts per square meter for stainless steel 304 is taken as indicating material susceptible to friction ignition. No attempt has been made to relate PV values to other material properties. This work reports the analysis of the WSTF friction-ignition test system for producing fundamental properties of metallic materials relating to ignition through friction. Three materials, aluminum, titanium, and nickel were tested in the WSTF frictional ignition instrument system under atmospheres of oxygen or nitrogen. Test conditions were modified to reach a steady state of operation, that is applied, the force was reduced and the rotational speed was reduced. Additional temperature measurements were made on the stator sample. The aluminum immediately galled on contact (reproducible) and the test was stopped. Titanium immediately ignited as a result of non-uniform contact of the stator and rotor. This was reproducible. A portion of the stator sampled burned, but the test continued. Temperature measurements on the stator were used to validate the mathematical model used for estimating the interface (stator/rotor) temperature. These interface temperature measurements and the associate thermal flux into the stator were used to distinguish material-phase transitions, chemical reaction, and mechanical work. The mechanical work was used to analyze surface asperities in the materials and to estimate a

Phenomenological description of internal friction spectra in glass-forming and glassy systems

International Nuclear Information System (INIS)

Lomovskij, V.A.

1999-01-01

Dissipative events in different by chemical nature glass-forming systems, including B 2 O 3 , are studied. It is established from the spectra of internal friction of these systems that the maxima of the energy dissipation of the external power impact are positioned both in the area of viscous flow metastable structural liquid state and in the area of solid elastic state

Chaotic orbits of a pendulum with variable length

Directory of Open Access Journals (Sweden)

Massimo Furi

2004-03-01

Full Text Available The main purpose of this investigation is to show that a pendulum, whose pivot oscillates vertically in a periodic fashion, has uncountably many chaotic orbits. The attribute chaotic is given according to the criterion we now describe. First, we associate to any orbit a finite or infinite sequence as follows. We write 1 or $-1$ every time the pendulum crosses the position of unstable equilibrium with positive (counterclockwise or negative (clockwise velocity, respectively. We write 0 whenever we find a pair of consecutive zero's of the velocity separated only by a crossing of the stable equilibrium, and with the understanding that different pairs cannot share a common time of zero velocity. Finally, the symbol $omega$, that is used only as the ending symbol of a finite sequence, indicates that the orbit tends asymptotically to the position of unstable equilibrium. Every infinite sequence of the three symbols ${1,-1,0}$ represents a real number of the interval $[0,1]$ written in base 3 when $-1$ is replaced with 2. An orbit is considered chaotic whenever the associated sequence of the three symbols ${1,2,0}$ is an irrational number of $[0,1]$. Our main goal is to show that there are uncountably many orbits of this type.

A Proposal Of Simulation Model Of A Wind-Steering System For Sailing Yachts, Based On Single-Stage Servo-Pendulum Coupled With Main Rudder

Directory of Open Access Journals (Sweden)

Piętak Andrzej

2015-04-01

Full Text Available The aim of this study was to investigate possible application of fast design prototyping methods for wind-steering systems used in offshore sailing yachts. The development of such methods would help to speed up the construction work and reduce the scope of necessary experimental research, prior to implementation of the system. In the present work, based on an analysis of existing designs of windvane systems, a preliminary selection of the system configuration has been undertaken, in terms of a compromise between efficiency, performance, and design complexity. Construction design of a single-stage, servo – pendulum system, has been developed by using the Autodesk Inventor design package. Next, based on the design data, a simulation model of the system, has been produced by using Matlab - Simulink software and SimMechanics library. The model was further verified in terms of kinematics mapping with the use of Matlab visualization tools.

Parameter Estimation of Damped Compound Pendulum Using Bat Algorithm

Directory of Open Access Journals (Sweden)

Saad Mohd Sazli

2016-01-01

Full Text Available In this study, the parameter identification of the damped compound pendulum system is proposed using one of the most promising nature inspired algorithms which is Bat Algorithm (BA. The procedure used to achieve the parameter identification of the experimental system consists of input-output data collection, ARX model order selection and parameter estimation using bat algorithm (BA method. PRBS signal is used as an input signal to regulate the motor speed. Whereas, the output signal is taken from position sensor. Both, input and output data is used to estimate the parameter of the autoregressive with exogenous input (ARX model. The performance of the model is validated using mean squares error (MSE between the actual and predicted output responses of the models. Finally, comparative study is conducted between BA and the conventional estimation method (i.e. Least Square. Based on the results obtained, MSE produce from Bat Algorithm (BA is outperformed the Least Square (LS method.

Surface Friction of Polyacrylamide Hydrogel Particles

Science.gov (United States)

Cuccia, Nicholas; Burton, Justin

Polyacrylamide hydrogel particles have recently become a popular system for modeling low-friction, granular materials near the jamming transition. Because a gel consists of a polymer network filled with solvent, its frictional behavior is often explained using a combination of hydrodynamic lubrication and polymer-surface interactions. As a result, the frictional coefficient can vary between 0.001 and 0.03 depending on several factors such as contact area, sliding velocity, normal force, and the gel surface chemistry. Most tribological measurements of hydrogels utilize two flat surfaces, where the contact area is not well-defined. We have built a custom, low-force tribometer to measure the single-contact frictional properties of spherical hydrogel particles on flat hydrogel surfaces under a variety of measurement conditions. At high velocities (> 1 cm/s), the friction coefficient depends linearly on velocity, but does not tend to zero at zero velocity. We also compare our measurements to solid particles (steel, glass, etc.) on hydrogel surfaces, which exhibit larger frictional forces, and show less dependence on velocity. A physical model for the friction which includes the lubrication layer between the deformed surfaces will be discussed. National Science Foundation Grant No. 1506446.

[Tribological assessment of articular cartilage. A system for the analysis of the friction coefficient of cartilage, regenerates and tissue engineering constructs; initial results].

Science.gov (United States)

Schwarz, M L R; Schneider-Wald, B; Krase, A; Richter, W; Reisig, G; Kreinest, M; Heute, S; Pott, P P; Brade, J; Schütte, A

2012-10-01

Values for the friction coefficient of articular cartilage are given in ranges of percentage and lower and are calculated as a quotient of the friction force and the perpendicular loading force acting on it. Thus, a sophisticated system has to be provided for analysing the friction coefficient under different conditions in particular when cartilage should be coupled as friction partner. It is possible to deep-freeze articular cartilage before measuring the friction coefficient as the procedure has no influence on the results. The presented tribological system was able to distinguish between altered and native cartilage. Furthermore, tissue engineered constructs for cartilage repair were differentiated from native cartilage probes by their friction coefficient. In conclusion a tribological equipment is presented to analyze the friction coefficient of articular cartilage, in vivo generated cartilage regenerates and in vitro tissue engineered constructs regarding their biomechanical properties for quality assessment.

A novel tri-axis MEMS gyroscope with in-plane tetra-pendulum proof masses and enhanced sensitive springs

International Nuclear Information System (INIS)

Wang, M C; Jiao, J W; Yan, P L; Mi, B W; Qin, S

2014-01-01

This paper presents a tri-axis MEMS gyroscope design with novel tetra-pendulum proof masses for X-, Y-axis and regular proof masses for Z-axis rate sensing, which are all coupled with and embedded in a conventional tuning fork driving frame. The four pendulum proof masses are suspended via the torsional springs to a common center anchor and can be driven to swing around the anchor via the tilted transforming springs as the driving frame is oscillated in an anti-phase mode. As an X-, Y-axis angular rate is applied, the tetra-pendulum proof masses will rotate around the torsional springs in pairs for X- and Y-axis differential sensing, respectively. In particular, we investigated the relationship between the tilting angle of the transforming spring and its transforming efficiency, i.e. the amplitude ratio of the pendulum's swing to the driving oscillation, which shows a straight impact on the sensitivity. By theoretical analysis and Ansys simulation, we achieved an optimal tilting angle of 22.5°, which extends along the angular bisector of the pendulum's and driving mass’ moving direction and demonstrates a significant increase in transforming efficiency by about 40%, compared with the trivial tilting angle of 45°. By employing an SOI-based bulk micromachining process, the prototype device with the optimal design of the transforming spring (type I) and that with the trivial design (type II) for reference have been successfully fabricated. As expected, the testing results indicate an increase of more than 20% in the X- and Y- sensitivities, which is mainly from the enhanced sensitive transforming springs. (paper)

Friction-Induced Mitochondrial Dysregulation Contributes to Joint Deterioration in Prg4 Knockout Mice

Directory of Open Access Journals (Sweden)

Kimberly A. Waller

2017-06-01

Full Text Available Deficiency of PRG4 (lubricin, the boundary lubricant in mammalian joints, contributes to increased joint friction accompanied by superficial and upper intermediate zone chondrocyte caspase-3 activation, as shown in lubricin-null (Prg4−/− mice. Caspase-3 activity appears to be reversible upon the restitution of Prg4 either endogenously in vivo, in a gene trap mouse, or as an applied lubricant in vitro. In this study we show that intra-articular injection of human PRG4 in vivo in Prg4−/− mice prevented caspase-3 activation in superficial zone chondrocytes and was associated with a modest decrease in whole joint friction measured ex vivo using a joint pendulum method. Non-lubricated Prg4−/− mouse cartilage shows caspase cascade activation caused by mitochondrial dysregulation, and significantly higher levels of peroxynitrite (ONOO− and −OH and superoxide (O−2 compared to Prg4+/+ and Prg4+/− cartilage. Enzymatic activity levels of caspase 8 across Prg4 mutant mice were not significantly different, indicating no extrinsic apoptosis pathway activation. Western blots showed caspase-3 and 9 activation in Prg4−/− tissue extracts, and the appearance of nitrosylated Cys163 in the active cleft of caspase-3 which inhibits its enzymatic activity. These findings are relevant to patients at risk for arthrosis, from camptodactyl-arthropathy-coxa vara-pericarditis (CACP syndrome and transient lubricin insufficiency due to trauma and inflammation.

Slow rupture of frictional interfaces

Science.gov (United States)

Bar Sinai, Yohai; Brener, Efim A.; Bouchbinder, Eran

2012-02-01

The failure of frictional interfaces and the spatiotemporal structures that accompany it are central to a wide range of geophysical, physical and engineering systems. Recent geophysical and laboratory observations indicated that interfacial failure can be mediated by slow slip rupture phenomena which are distinct from ordinary, earthquake-like, fast rupture. These discoveries have influenced the way we think about frictional motion, yet the nature and properties of slow rupture are not completely understood. We show that slow rupture is an intrinsic and robust property of simple non-monotonic rate-and-state friction laws. It is associated with a new velocity scale cmin, determined by the friction law, below which steady state rupture cannot propagate. We further show that rupture can occur in a continuum of states, spanning a wide range of velocities from cmin to elastic wave-speeds, and predict different properties for slow rupture and ordinary fast rupture. Our results are qualitatively consistent with recent high-resolution laboratory experiments and may provide a theoretical framework for understanding slow rupture phenomena along frictional interfaces.

An empirical model for friction in cold forging

DEFF Research Database (Denmark)

Bay, Niels; Eriksen, Morten; Tan, Xincai

2002-01-01

With a system of simulative tribology tests for cold forging the friction stress for aluminum, steel and stainless steel provided with typical lubricants for cold forging has been determined for varying normal pressure, surface expansion, sliding length and tool/work piece interface temperature...... of normal pressure and tool/work piece interface temperature. The model is verified by process testing measuring friction at varying reductions in cold forward rod extrusion. KEY WORDS: empirical friction model, cold forging, simulative friction tests....

Approximate expressions for the period of a simple pendulum using a Taylor series expansion

International Nuclear Information System (INIS)

Belendez, Augusto; Marquez, Andres; Ortuno, Manuel; Gallego, Sergi; Arribas, Enrique

2011-01-01

An approximate scheme for obtaining the period of a simple pendulum for large-amplitude oscillations is analysed and discussed. When students express the exact frequency or the period of a simple pendulum as a function of the oscillation amplitude, and they are told to expand this function in a Taylor series, they always do so using the oscillation amplitude as the variable, without considering that if they change the variable (in this paper to the new variable m), a different Taylor series expansion may be performed which is in addition more accurate than previously published ones. Students tend to believe that there is one and only one way of performing a Taylor series expansion of a specific function. The approximate analytical formula for the period is obtained by means of a Taylor expansion of the exact frequency taking into account the Kidd-Fogg formula for the period. This approach based on the Taylor expansion of the frequency about a suitable value converges quickly even for large amplitudes. We believe that this method may be very useful for teaching undergraduate courses on classical mechanics and helping students understand nonlinear oscillations of a simple pendulum.

Approximate expressions for the period of a simple pendulum using a Taylor series expansion

Energy Technology Data Exchange (ETDEWEB)

Belendez, Augusto; Marquez, Andres; Ortuno, Manuel; Gallego, Sergi [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Arribas, Enrique, E-mail: a.belendez@ua.es [Departamento de Fisica Aplicada, Escuela Superior de IngenierIa Informatica, Universidad de Castilla-La Mancha, Avda de Espana, s/n, E-02071 Albacete (Spain)

2011-09-15

An approximate scheme for obtaining the period of a simple pendulum for large-amplitude oscillations is analysed and discussed. When students express the exact frequency or the period of a simple pendulum as a function of the oscillation amplitude, and they are told to expand this function in a Taylor series, they always do so using the oscillation amplitude as the variable, without considering that if they change the variable (in this paper to the new variable m), a different Taylor series expansion may be performed which is in addition more accurate than previously published ones. Students tend to believe that there is one and only one way of performing a Taylor series expansion of a specific function. The approximate analytical formula for the period is obtained by means of a Taylor expansion of the exact frequency taking into account the Kidd-Fogg formula for the period. This approach based on the Taylor expansion of the frequency about a suitable value converges quickly even for large amplitudes. We believe that this method may be very useful for teaching undergraduate courses on classical mechanics and helping students understand nonlinear oscillations of a simple pendulum.

Suggested Research Method for Testing Selected Tribological Properties of Friction Components in Vehicle Braking Systems

Directory of Open Access Journals (Sweden)

Borawski Andrzej

2016-09-01

Full Text Available The braking system is one of the most important systems in any vehicle. Its proper functioning may determine the health and life the people inside the vehicle as well as other road users. Therefore, it is important that the parameters which characterise the functioning of brakes changed as little as possible throughout their lifespan. Multiple instances of heating and cooling of the working components of the brake system as well as the environment they work in may impact their tribological properties. This article describes a method of evaluating the coefficient of friction and the wear speed of abrasive wear of friction working components of brakes. The methodology was developed on the basis of Taguchi’s method of process optimization.

In-Vivo Human Skin to Textiles Friction Measurements

Science.gov (United States)

Pfarr, Lukas; Zagar, Bernhard

2017-10-01

We report on a measurement system to determine highly reliable and accurate friction properties of textiles as needed for example as input to garment simulation software. Our investigations led to a set-up that allows to characterize not just textile to textile but also textile to in-vivo human skin tribological properties and thus to fundamental knowledge about genuine wearer interaction in garments. The method of test conveyed in this paper is measuring concurrently and in a highly time resolved manner the normal force as well as the resulting shear force caused by a friction subject intending to slide out of the static friction regime and into the dynamic regime on a test bench. Deeper analysis of various influences is enabled by extending the simple model following Coulomb's law for rigid body friction to include further essential parameters such as contact force, predominance in the yarn's orientation and also skin hydration. This easy-to-use system enables to measure reliably and reproducibly both static and dynamic friction for a variety of friction partners including human skin with all its variability there might be.

The effect of ligation method on friction in sliding mechanics.

Science.gov (United States)

Hain, Max; Dhopatkar, Ashish; Rock, Peter

2003-04-01

During orthodontic tooth movement with the preadjusted edgewise system, friction generated at the bracket/archwire interface tends to impede the desired movement. The method of ligation is an important contributor to this frictional force. This in vitro study investigated the effect of ligation method on friction and evaluated the efficacy of the new slick elastomeric modules from TP Orthodontics (La Porte, Ind), which are claimed to reduce friction at the module/wire interface. Slick modules were compared with regular nonslick modules, stainless steel ligatures, and the SPEED self-ligating bracket system (Strite Industries, Cambridge, Ontario, Canada). The effect of using slick modules with metal-reinforced ceramic (Clarity, 3M Unitek, Monrovia, Calif) and miniature brackets (Minitwin, 3M Unitek) was also examined. Results showed that, when considering tooth movement along a 0.019 x 0.025-in stainless steel archwire, saliva-lubricated slick modules can reduce static friction at the module/archwire interface by up to 60%, regardless of the bracket system. The SPEED brackets produced the lowest friction compared with the 3 other tested bracket systems when regular modules were used. The use of slick modules, however, with all of the ligated bracket types tested significantly reduced friction to below the values recorded in the SPEED groups. Loosely tied stainless steel ligatures were found to generate the least friction.

PEBBLES Simulation of Static Friction and New Static Friction Benchmark

International Nuclear Information System (INIS)

Cogliati, Joshua J.; Ougouag, Abderrafi M.

2010-01-01

Pebble bed reactors contain large numbers of spherical fuel elements arranged randomly. Determining the motion and location of these fuel elements is required for calculating certain parameters of pebble bed reactor operation. This paper documents the PEBBLES static friction model. This model uses a three dimensional differential static friction approximation extended from the two dimensional Cundall and Strack model. The derivation of determining the rotational transformation of pebble to pebble static friction force is provided. A new implementation for a differential rotation method for pebble to container static friction force has been created. Previous published methods are insufficient for pebble bed reactor geometries. A new analytical static friction benchmark is documented that can be used to verify key static friction simulation parameters. This benchmark is based on determining the exact pebble to pebble and pebble to container static friction coefficients required to maintain a stable five sphere pyramid.

The Pit and the Safety Pendulum

Energy Technology Data Exchange (ETDEWEB)

Nitschke, Robert Leon; Ramos, Amadeo Gabriel

2000-11-01

The hypothesis of this paper is that the safety analysis pendulum has swung considerably in the direction of increasingly complex and lengthy safety evaluations and intense reviews during the past 30 years. The test of this hypothesis will be a review of the safety analysis conducted for various activities associated with the retrieval of transuranic radioactive waste from burial pits at a National Laboratory site over a span of 30 years. The examination will focus on the safety aspects and the safety analysis that was conducted for the projects. At the conclusion of this examination, the paper will identify five reasons why the changes have taken place.

Trial manufacture of rotary friction tester and frictional force measurement of metals

CERN Document Server

Abe, T; Kanari, M; Tanzawa, S

2002-01-01

In the plasma confinement type fusion reactor, in-vessel structures such as a blanket module slide at the joints each other when plasma disruption occurs, and then frictional heat is generated there. Therefore, for the selection of material and the use as the design data, it is important to understand the frictional characteristics of metals and ceramic films in the vacuum. In the present study, we have manufactured a prototype of rotary friction tester and examined the performances of the tester. The frictional characteristics of metals in the room air was measured using the friction tester, and the results obtained are as follows. A drifting friction force for a constant time and a friction force during the idling were 98 mN and 225 mN, respectively. These values were sufficiently small as compared to pressing load (9.8 - 57.8 N) used in the friction test. In a friction force measurement of stainless steel, dynamic friction force obeyed Amontons' law which indicated that dynamic friction force is not depend...

Characterization of pavement texture by means of height difference correlation and relation to wet skid resistance

Directory of Open Access Journals (Sweden)

Stefan Torbruegge

2015-04-01

We deduce within this article the correlation between classical surface roughness parameters and the parameter set of self-affine surfaces. These parameters allow for a detailed understanding of the relationship between pavement texture and its wet skid resistance. We present wet skid resistance measurements with the British pendulum and a linear friction tester device on different pavement textures. We demonstrate that the so-called estimated texture depth does not correlate to the surface skid resistance measured with the British pendulum. Finally, we deduce a dependency of wet skid resistance on pavement texture which is supported by current models for hysteresis friction.

Simple analytic formula for the period of the nonlinear pendulum via the Struve function: connection to acoustical impedance matching

International Nuclear Information System (INIS)

Douvropoulos, Theodosios G

2012-01-01

An approximate formula for the period of pendulum motion beyond the small amplitude regime is obtained based on physical arguments. Two different schemes of different accuracy are developed: in the first less accurate scheme, emphasis is given on the non-quadratic form of the potential in connection to isochronism, and a specific form of a generic formula that is met in many previous works is produced, while the second and main result contains the Struve function which is further approximated by a simple sinusoidal expression based on its maximum value. The accuracy of the final formula gives a relative error of less than 0.2% for angles up to 140°. In addition, a simple relation between the Struve function and the complete elliptic integral of the first kind is produced, since they both constitute solutions of the pendulum period. This relation makes it possible for someone to connect different areas in physics and solve a difficult task by comparison with another much more simple one. As an example, a connection between the pendulum period and the acoustical radiation impedance is proposed through impedance matching and some interesting relations are produced. This paper is intended for undergraduate students to be useful for analysing pendulum experiments in introductory physics labs and it is also believed to offer valuable insight into some properties of the simple pendulum in undergraduate courses on general physics. (paper)

Existence of Stick-Slip Periodic Solutions in a Dry Friction Oscillator

International Nuclear Information System (INIS)

Li Qun-Hong; Chen Yu-Ming; Qin Zhi-Ying

2011-01-01

The stick-slip behavior in friction oscillators is very complicated due to the non-smoothness of the dry friction, which is the basic form of motion of dynamical systems with friction. In this paper, the stick-slip periodic solution in a single-degree-of-freedom oscillator with dry friction is investigated in detail. Under the assumption of kinetic friction being the Coulomb friction, the existence of the stick-slip periodic solution is considered to give out an analytic criterion in a class of friction systems. A two-parameter unfolding diagram is also described. Moreover, the time and states of motion on the boundary of the stick and slip motions are semi-analytically obtained in a single stick-slip period. (general)

Learning by experience on the example of mathematic pendulum

Science.gov (United States)

Horváth, Peter

2017-01-01

The very suitable topic for independent student activities is the investigation of factors influencing an oscillation period of the mathematic pendulum. The article describes the experience from particular lessons. Students themselves were discovering new facts. They learned about the physics practice of acquiring new knowledge. The knowledge quality and retention was compared between the experimental classes and classes with a traditional instruction one year after the experiment.

Friction Anisotropy with Respect to Topographic Orientation

Science.gov (United States)

Yu, Chengjiao; Wang, Q. Jane

2012-01-01

Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties. PMID:23248751

Enhanced surface friction coefficient and hydrophobicity of TPE substrates using an APPJ system

Science.gov (United States)

Sainz-García, Elisa; Alba-Elías, Fernando; Múgica-Vidal, Rodolfo; González-Marcos, Ana

2015-02-01

An APPJ system was used to deposit a coating that combines a low friction coefficient with a high water contact angle (WCA) on a thermoplastic elastomer substrate (TPE) that is used in automotive profiling. The main drawback of this research is that groups that improve the hydrophobicity of the surface worsen its tribological properties. To overcome this, this study explored the use of various mixtures of differing proportions of two precursors. They were a siloxane, aminopropyltriethoxysilane (APTES) that was used to reduce the friction coefficient by its content of SiOx and a fluorinated compound, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FLUSI) that was used to improve the water-repellency characteristics, due to the presence of CF2 long chains. The coatings were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), dynamic Water Contact Angle (WCA), stability tests and tribological tests. It was found that an increase of the absorbance area under the SiOSi peak and inorganic groups is related to lower friction coefficients. On the other hand, the higher the CF2 percentage is, the higher the WCA is. The sample that was coated with 25% of FLUSI and 75% of APTES combined the improvements of both functional properties, the friction coefficient and the WCA. It has an average friction coefficient that is (0.530 ± 0.050) 51.5% lower and a WCA that is (θadv = 119.8° ± 4.75) 4.4% higher than the uncoated TPE sample. A satisfactory stability in humid ambient for twelve months showed a slight decrease of WCA (4.4%) for this sample. The results of this study permit one to realize the effectiveness of using fluorinated precursors to avoid a significant decrease in the WCA when applying a precursor to anti-friction improvement.

Friction and Adhesion Forces of Bacillus thuringiensis Spores on Planar Surfaces in Atmospheric Systems

Energy Technology Data Exchange (ETDEWEB)

Kweon, Hyojin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2011-11-07

The kinetic friction force and the adhesion force of Bacillus thuringiensis spores on planar surfaces in atmospheric systems were studied using atomic force microscopy. The influence of relative humidity (RH) on these forces varied for different surface properties including hydrophobicity, roughness, and surface charge. The friction force of the spore was greater on a rougher surface than on mica, which is atomically flat. As RH increases, the friction force of the spores decreases on mica whereas it increases on rough surfaces. The influence of RH on the interaction forces between hydrophobic surfaces is not as strong as for hydrophilic surfaces. The friction force of the spore is linear to the sum of the adhesion force and normal load on the hydrophobic surface. In conclusion, the poorly defined surface structure of the spore and the adsorption of contaminants from the surrounding atmosphere are believed to cause a discrepancy between the calculated and measured adhesion forces.

Simple Model-Free Controller for the Stabilization of Planetary Inverted Pendulum

Directory of Open Access Journals (Sweden)

Huanhuan Mai

2012-01-01

Full Text Available A simple model-free controller is presented for solving the nonlinear dynamic control problems. As an example of the problem, a planetary gear-type inverted pendulum (PIP is discussed. To control the inherently unstable system which requires real-time control responses, the design of a smart and simple controller is made necessary. The model-free controller proposed includes a swing-up controller part and a stabilization controller part; neither controller has any information about the PIP. Since the input/output scaling parameters of the fuzzy controller are highly sensitive, we use genetic algorithm (GA to obtain the optimal control parameters. The experimental results show the effectiveness and robustness of the present controller.

Pendulum impact tests of wooden and steel highway guardrail posts

Science.gov (United States)

Charles J. Gatchell; Jarvis D. Michie

1974-01-01

Impact strength characteristics of southern pine, red oak, and steel highway guardrail posts were evaluated in destructive impact testing with a 4,000-pound pendulum at the Southwest Research Institute. Effects were recorded with high-speed motion-picture equipment. Comparisons were based on reactions to the point of major post failure. Major comparisons of 6x6-inch...

System size effects on the mechanical response of cohesive-frictional granular ensembles

Directory of Open Access Journals (Sweden)

Singh Saurabh

2017-01-01

Full Text Available Shear resistance in granular ensembles is a result of interparticle interaction and friction. However, even the presence of small amounts of cohesion between the particles changes the landscape of the mechanical response considerably. Very often such cohesive frictional (c-ϕ granular ensembles are encountered in nature as well as while handling and storage of granular materials in the pharmaceutical, construction and mining industries. Modeling of these c-ϕ materials, especially in engineering applications have relied on the oft-made assumption of a “continua” and have utilized the popular tenets of continuum plasticity theory. We present an experimental investigation on the fundamental mechanics of c-ϕ materials specifically; we investigate if there exists a system size effect and any additional length scales beyond the continuum length scale on their mechanical response. For this purpose, we conduct a series of 1-D compression (UC tests on cylindrical specimens reconstituted in the laboratory with a range of model particle–binder combinations such as sandcement, sand-epoxy, and glass ballotini-epoxy mixtures. Specimens are reconstituted to various diameters ranging from 10 mm to 150 mm (with an aspect ratio of 2 to a predefined packing fraction. In addition to the effect of the type of binder (cement, epoxy and system size, the mean particle size is also varied from 0.5 to 2.5 mm. The peak strength of these materials is significant as it signals the initiation of the cohesive-bond breaking and onset of mobilization of the inter particle frictional resistance. For these model systems, the peak strength is a strong function of the system size of the ensemble as well as the mean particle size. This intriguing observation is counter to the traditional notion of a continuum plastic typical granular ensemble. Microstructure studies in a computed-tomograph have revealed the existence of a web patterned ‘entangled-chain’ like structure

System size effects on the mechanical response of cohesive-frictional granular ensembles

Science.gov (United States)

Singh, Saurabh; Kandasami, Ramesh Kannan; Mahendran, Rupesh Kumar; Murthy, Tejas

2017-06-01

Shear resistance in granular ensembles is a result of interparticle interaction and friction. However, even the presence of small amounts of cohesion between the particles changes the landscape of the mechanical response considerably. Very often such cohesive frictional (c-ϕ) granular ensembles are encountered in nature as well as while handling and storage of granular materials in the pharmaceutical, construction and mining industries. Modeling of these c-ϕ materials, especially in engineering applications have relied on the oft-made assumption of a "continua" and have utilized the popular tenets of continuum plasticity theory. We present an experimental investigation on the fundamental mechanics of c-ϕ materials specifically; we investigate if there exists a system size effect and any additional length scales beyond the continuum length scale on their mechanical response. For this purpose, we conduct a series of 1-D compression (UC) tests on cylindrical specimens reconstituted in the laboratory with a range of model particle-binder combinations such as sandcement, sand-epoxy, and glass ballotini-epoxy mixtures. Specimens are reconstituted to various diameters ranging from 10 mm to 150 mm (with an aspect ratio of 2) to a predefined packing fraction. In addition to the effect of the type of binder (cement, epoxy) and system size, the mean particle size is also varied from 0.5 to 2.5 mm. The peak strength of these materials is significant as it signals the initiation of the cohesive-bond breaking and onset of mobilization of the inter particle frictional resistance. For these model systems, the peak strength is a strong function of the system size of the ensemble as well as the mean particle size. This intriguing observation is counter to the traditional notion of a continuum plastic typical granular ensemble. Microstructure studies in a computed-tomograph have revealed the existence of a web patterned `entangled-chain' like structure, we argue that this ushers

Biped Robot Gait Planning Based on 3D Linear Inverted Pendulum Model

Science.gov (United States)

Yu, Guochen; Zhang, Jiapeng; Bo, Wu

2018-01-01

In order to optimize the biped robot’s gait, the biped robot’s walking motion is simplify to the 3D linear inverted pendulum motion mode. The Center of Mass (CoM) locus is determined from the relationship between CoM and the Zero Moment Point (ZMP) locus. The ZMP locus is planned in advance. Then, the forward gait and lateral gait are simplified as connecting rod structure. Swing leg trajectory using B-spline interpolation. And the stability of the walking process is discussed in conjunction with the ZMP equation. Finally the system simulation is carried out under the given conditions to verify the validity of the proposed planning method.

Friction testing for the National Highway System for 2001 : all Louisiana districts : technical assistance report.

Science.gov (United States)

2002-11-01

This report contains the results of friction testing conducted by the pavement/systems group of the Louisiana Transportation Research Center (LTRC) on the National Highway System (NHS) in 2000 and 2001. The data contained in this report covers all Lo...

FRICTION-BOON OR BANE IN ORTHODONTICS

Directory of Open Access Journals (Sweden)

Sameer

2015-11-01

Full Text Available OBJECTIVE: Most fixed appliance techniques involve some degree of sliding between brackets and arch wires. A sound knowledge of the various factors affecting the magnitude of friction is of paramount importance to the clinician. The present study was performed to evaluate and compare the frictional resistance and characteristics between self-ligating brackets and pre-adjusted edgewise brackets with different types of ligation. MATERIALS AND METHODS: Tidy's frictional test design was used to simulate retraction of tooth along with artificial saliva to simulate wet conditions in oral cavity. The jig with this assembly was mounted on the Instron machine with the cross head moving upwards at a speed of 5mm/min. The movable bracket was suspended from the load cell of the testing machine, while the jig was mounted on cross head of machine and the load cell readings were recorded on digital display. Following wires are used 0.016 HANT, 0.019X 0.025HANT, 0.019X 0.025 SS, 0.021X 0.025 SS wires are used. The brackets used were 0.022 slot Damon, 0.022 Smart clip and 0.022 slot MBT system. RESULTS: Self ligating brackets were shown to produce lesser friction when compared to the conventional brackets used with modules, and stainless steel ligatures. Damon self-ligating brackets produce a least friction of all the brackets used in the study. Stainless steel ligatures produced the least friction compared to elastomeric. CONCLUSION: Self ligation brackets produce lesser friction than the conventional brackets ligated with elastomeric modules and stainless steel ligature. Damon self-ligating brackets produce a least friction of all the brackets used in the study width of the bracket was also found to be directly proportional to the friction produced 0.0016HANT with elastomeric modules produce more friction due increase in flexibility of wire.

Development of a Simulink® toolbox for friction control design and compensation

Directory of Open Access Journals (Sweden)

Teodor DUMITRIU

2005-12-01

Full Text Available This paper focuses on the development of a MATLAB/Simulink® library for servo-systems with friction as a part of a new simulation platform dedicated to model, analysis and control design of friction. It is well known that friction is a very important process for the control engineering both for high-precision servo – mechanisms and simple pneumatic and hydraulic systems. Highly nonlinear process, friction may result in steady state errors, limit cycles and poor performance. It is therefore important for control engineering to understand friction phenomena and to know how to deal with them. Moreover, a reliable library of friction models that captures the friction behavior provides an important tool in order to investigate by analysis and simulation the properties of friction that are relevant to control design.

Blade Bearing Friction Estimation of Operating Wind Turbines

DEFF Research Database (Denmark)

Perisic, Nevena; Pedersen, Bo Juul; Kirkegaard, Poul Henning

2012-01-01

Blade root bearing on a wind turbine (WTG) enables pitching of blades for power control and rotor braking and is a WTG critical component. As the size of modern WTGs is constantly increasing, this leads to relatively less rigid bearings, more sensitive to deformations, thus WTG operational...... reliability can be increased by continuous monitoring of blade bearing. High blade bearing friction is undesirable, as it may be associated with excessive heating of the surfaces, damage and/or inefficient operation. Thus, continuous observation of bearing friction level is crucial for blade bearing health...... monitoring systems. A novel algorithm for online monitoring of bearing friction level is developed combining physical knowledge about pitch system dynamics with state estimator, i.e. observer theory and signal processing assuming realistic sensor availability. Results show estimation of bearing friction...

Identification of GMS friction model without friction force measurement

International Nuclear Information System (INIS)

Grami, Said; Aissaoui, Hicham

2011-01-01

This paper deals with an online identification of the Generalized Maxwell Slip (GMS) friction model for both presliding and sliding regime at the same time. This identification is based on robust adaptive observer without friction force measurement. To apply the observer, a new approach of calculating the filtered friction force from the measurable signals is introduced. Moreover, two approximations are proposed to get the friction model linear over the unknown parameters and an approach of suitable filtering is introduced to guarantee the continuity of the model. Simulation results are presented to prove the efficiency of the approach of identification.

Slow rupture of frictional interfaces

OpenAIRE

Sinai, Yohai Bar; Brener, Efim A.; Bouchbinder, Eran

2011-01-01

The failure of frictional interfaces and the spatiotemporal structures that accompany it are central to a wide range of geophysical, physical and engineering systems. Recent geophysical and laboratory observations indicated that interfacial failure can be mediated by slow slip rupture phenomena which are distinct from ordinary, earthquake-like, fast rupture. These discoveries have influenced the way we think about frictional motion, yet the nature and properties of slow rupture are not comple...

Structural Damping with Friction Beams

Directory of Open Access Journals (Sweden)

L. Gaul

2008-01-01

Full Text Available In the last several years, there has been increasing interest in the use of friction joints for enhancing damping in structures. The joints themselves are responsible for the major part of the energy dissipation in assembled structures. The dissipated work in a joint depends on both the applied normal force and the excitation force. For the case of a constant amplitude excitation force, there is an optimal normal force which maximizes the damping. A ‘passive’ approach would be employed in this instance. In most cases however, the excitation force, as well as the interface parameters such as the friction coefficient, normal pressure distribution, etc., are not constant. In these cases, a ‘semi-active’ approach, which implements an active varying normal force, is necessary. For the ‘passive’ and ‘semi-active’ approaches, the normal force has to be measured. Interestingly, since the normal force in a friction joint influences the local stiffness, the natural frequencies of the assembled structure can be tuned by adjusting the normal force. Experiments and simulations are performed for a simple laboratory structure consisting of two superposed beams with friction in the interface. Numerical simulation of the friction interface requires non-linear models. The response of the double beam system is simulated using a numerical algorithm programmed in MATLAB which models point-to-point friction with the Masing friction model. Numerical predictions and measurements of the double beam free vibration response are compared. A practical application is then described, in which a friction beam is used to damp the vibrations of the work piece table on a milling machine. The increased damping of the table reduces vibration amplitudes, which in turn results in enhanced surface quality of the machined parts, reduction in machine tool wear, and potentially higher feed rates. Optimal positioning of the friction beams is based on knowledge of the mode

Fragility and hysteretic creep in frictional granular jamming.

Science.gov (United States)

Bandi, M M; Rivera, M K; Krzakala, F; Ecke, R E

2013-04-01

The granular jamming transition is experimentally investigated in a two-dimensional system of frictional, bidispersed disks subject to quasistatic, uniaxial compression without vibrational disturbances (zero granular temperature). Three primary results are presented in this experimental study. First, using disks with different static friction coefficients (μ), we experimentally verify numerical results that predict jamming onset at progressively lower packing fractions with increasing friction. Second, we show that the first compression cycle measurably differs from subsequent cycles. The first cycle is fragile-a metastable configuration with simultaneous jammed and unjammed clusters-over a small packing fraction interval (φ(1)disk displacements over the same packing fraction interval. This fragile behavior is explained through a percolation mechanism of stressed contacts where cluster growth exhibits spatial correlation with disk displacements and contributes to recent results emphasizing fragility in frictional jamming. Control experiments show that the fragile state results from the experimental incompatibility between the requirements for zero friction and zero granular temperature. Measurements with several disk materials of varying elastic moduli E and friction coefficients μ show that friction directly controls the start of the fragile state but indirectly controls the exponential pressure rise. Finally, under repetitive loading (compression) and unloading (decompression), we find the system exhibits pressure hysteresis, and the critical packing fraction φ(c) increases slowly with repetition number. This friction-induced hysteretic creep is interpreted as the granular pack's evolution from a metastable to an eventual structurally stable configuration. It is shown to depend on the quasistatic step size Δφ, which provides the only perturbative mechanism in the experimental protocol, and the friction coefficient μ, which acts to stabilize the pack.

Confinement-Dependent Friction in Peptide Bundles

Science.gov (United States)

Erbaş, Aykut; Netz, Roland R.

2013-01-01

Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V → 0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. PMID:23528088

Transient effects in friction fractal asperity creep

CERN Document Server

Goedecke, Andreas

2013-01-01

Transient friction effects determine the behavior of a wide class of mechatronic systems. Classic examples are squealing brakes, stiction in robotic arms, or stick-slip in linear drives. To properly design and understand mechatronic systems of this type, good quantitative models of transient friction effects are of primary interest. The theory developed in this book approaches this problem bottom-up, by deriving the behavior of macroscopic friction surfaces from the microscopic surface physics. The model is based on two assumptions: First, rough surfaces are inherently fractal, exhibiting roughness on a wide range of scales. Second, transient friction effects are caused by creep enlargement of the real area of contact between two bodies. This work demonstrates the results of extensive Finite Element analyses of the creep behavior of surface asperities, and proposes a generalized multi-scale area iteration for calculating the time-dependent real contact between two bodies. The toolset is then demonstrated both...

The experiment research of the friction sliding isolation structure

Science.gov (United States)

Zhang, Shirong; Li, Jiangle; Wang, Sheliang

2018-04-01

This paper investigated the theory of the friction sliding isolation structure, The M0S2 solid lubricant was adopted as isolation bearing friction materials, and a new sliding isolation bearing was designed and made. The formula of the friction factor and the compression stress was proposed. The feasibility of the material MoS2 used as the coating material in a friction sliding isolation system was tested on the 5 layers concrete frame model. Two application experiment conditions were presented. The results of the experiment research indicated that the friction sliding isolation technology have a good damping effect.

Fuzzy logic inference-based Pavement Friction Management and real-time slippery warning systems: A proof of concept study.

Science.gov (United States)

Najafi, Shahriar; Flintsch, Gerardo W; Khaleghian, Seyedmeysam

2016-05-01

Minimizing roadway crashes and fatalities is one of the primary objectives of highway engineers, and can be achieved in part through appropriate maintenance practices. Maintaining an appropriate level of friction is a crucial maintenance practice, due to the effect it has on roadway safety. This paper presents a fuzzy logic inference system that predicts the rate of vehicle crashes based on traffic level, speed limit, and surface friction. Mamdani and Sugeno fuzzy controllers were used to develop the model. The application of the proposed fuzzy control system in a real-time slippery road warning system is demonstrated as a proof of concept. The results of this study provide a decision support model for highway agencies to monitor their network's friction and make appropriate judgments to correct deficiencies based on crash risk. Furthermore, this model can be implemented in the connected vehicle environment to warn drivers of potentially slippery locations. Published by Elsevier Ltd.

Bioinspired orientation-dependent friction.

Science.gov (United States)

Xue, Longjian; Iturri, Jagoba; Kappl, Michael; Butt, Hans-Jürgen; del Campo, Aránzazu

2014-09-23

Spatular terminals on the toe pads of a gecko play an important role in directional adhesion and friction required for reversible attachment. Inspired by the toe pad design of a gecko, we study friction of polydimethylsiloxane (PDMS) micropillars terminated with asymmetric (spatular-shaped) overhangs. Friction forces in the direction of and against the spatular end were evaluated and compared to friction forces on symmetric T-shaped pillars and pillars without overhangs. The shape of friction curves and the values of friction forces on spatula-terminated pillars were orientation-dependent. Kinetic friction forces were enhanced when shearing against the spatular end, while static friction was stronger in the direction toward the spatular end. The overall friction force was higher in the direction against the spatula end. The maximum value was limited by the mechanical stability of the overhangs during shear. The aspect ratio of the pillar had a strong influence on the magnitude of the friction force, and its contribution surpassed and masked that of the spatular tip for aspect ratios of >2.

Comparison for the interfacial and wall friction models in thermal-hydraulic system analysis codes

International Nuclear Information System (INIS)

Hwang, Moon Kyu; Park, Jee Won; Chung, Bub Dong; Kim, Soo Hyung; Kim, See Dal

2007-07-01

The average equations employed in the current thermal hydraulic analysis codes need to be closed with the appropriate models and correlations to specify the interphase phenomena along with fluid/structure interactions. This includes both thermal and mechanical interactions. Among the closure laws, an interfacial and wall frictions, which are included in the momentum equations, not only affect pressure drops along the fluid flow, but also have great effects for the numerical stability of the codes. In this study, the interfacial and wall frictions are reviewed for the commonly applied thermal-hydraulic system analysis codes, i.e. RELAP5-3D, MARS-3D, TRAC-M, and CATHARE

Novel application of a Wii remote to measure spasticity with the pendulum test: Proof of concept.

Science.gov (United States)

Yeh, Chien-Hung; Hung, Chi-Yao; Wang, Yung-Hung; Hsu, Wei-Tai; Chang, Yi-Chung; Yeh, Jia-Rong; Lee, Po-Lei; Hu, Kun; Kang, Jiunn-Horng; Lo, Men-Tzung

2016-01-01

The pendulum test is a standard clinical test for quantifying the severity of spasticity. In the test, an electrogoniometer is typically used to measure the knee angular motion. The device is costly and difficult to set up such that the pendulum test is normally time consuming. The goal of this study is to determine whether a Nintendo Wii remote can replace the electrogroniometer for reliable assessment of the angular motion of the knee in the pendulum test. The pendulum test was performed in three control participants and 13 hemiplegic stroke patients using both a Wii remote and an electrogoniometer. The correlation coefficient and the Bland-Altman difference plot were used to compare the results obtained from the two devices. The Wilcoxon signed-rank test was used to compare the difference between hemiplegia-affected and nonaffected sides in the hemiplegic stroke patients. There was a fair to strong correlation between measurements from the Wii remote and the electrogoniometer (0.513

Comparison of Interfacial and Wall Friction Models in Thermal-Hydraulic System Analysis Codes (Rev1.0)

International Nuclear Information System (INIS)

Hwang, Moon Kyu; Kim, Soo Hyung; Kim, Byung Jae; Chung, Bub Dong; Kim, Hee Cheol

2010-04-01

This reports is a literature survey on models and correlations for interfacial and wall friction models that are used to simulate thermal-hydraulics in nuclear reactors. The interfacial and wall frictions are needed to solve the momentum equations of gas, continuous liquid and droplet. Not only existing system codes, such as RELAP5-3D, TRAC-M, MARS, TRACE, CATHARE) but also up-to-date researches were reviewed. This report is a revised version of the previous technical report(KAERI/TR-3437/2007)

Parameter Estimation of Damped Compound Pendulum Differential Evolution Algorithm

Directory of Open Access Journals (Sweden)

Saad Mohd Sazli

2016-01-01

Full Text Available This paper present the parameter identification of damped compound pendulum using differential evolution algorithm. The procedure used to achieve the parameter identification of the experimental system consisted of input output data collection, ARX model order selection and parameter estimation using conventional method least square (LS and differential evolution (DE algorithm. PRBS signal is used to be input signal to regulate the motor speed. Whereas, the output signal is taken from position sensor. Both, input and output data is used to estimate the parameter of the ARX model. The residual error between the actual and predicted output responses of the models is validated using mean squares error (MSE. Analysis showed that, MSE value for LS is 0.0026 and MSE value for DE is 3.6601×10-5. Based results obtained, it was found that DE have lower MSE than the LS method.

Ratchet due to broken friction symmetry

DEFF Research Database (Denmark)

Norden, Bengt; Zolotaryuk, Yaroslav; Christiansen, Peter Leth

2002-01-01

A ratchet mechanism that occurs due to asymmetric dependence of the friction of a moving system on its velocity or a driving force is reported. For this kind of ratchet, instead of a particle moving in a periodic potential, the dynamics of which have broken space-time symmetry, the system must...... be provided with sonic internal structure realizing such a velocity- or force-friction dependence. For demonstration of a ratchet mechanism of this type, an experimental setup (gadget) that converts longitudinal oscillating or fluctuating motion into a unidirectional rotation has been built and experiments...... with it have been carried out. In this device, an asymmetry of friction dependence on an applied force appears, resulting in rectification of rotary motion, In experiments, our setup is observed to rotate only in one direction, which is in accordance with given theoretical arguments, Despite the setup being...

A unified modeling and control design for precision transmission system with friction and backlash

Directory of Open Access Journals (Sweden)

Xiulan Bao

2016-05-01

Full Text Available The structural flexibility, nonlinear friction, and backlash are the major factors limiting the control performance of precision transmission systems. If uncompensated, these factors compromise the positioning and tracking accuracy of precision transmission systems and even cause limit cycles and oscillation. In this article, a framework for integrated design from dynamic modeling to controller design is proposed. A multi-state dynamic model is presented, which can unify the modeling for a multi-state, discontinuous system including the motor state, the motion state, the mechanical contact state, and the friction state. Then, a control design method related to the dynamic modeling using perturbation separation of the model parameters is presented. Using the proposed modeling method, a continuous dynamic model is established to include all different partition models. The model comprehensively describes the mechanical and electrical characteristics of the precision transmission system. A robust controller is designed using the proposed control method. Experimental results demonstrate that the proposed modeling method is accurate and the proposed control method significantly improves accuracy and robustness of the controller compared to traditional control methods.

FRICTION - WELDING MACHINE AUTOMATIC CONTROL CIRCUIT DESIGN AND APPLICATION

Directory of Open Access Journals (Sweden)

Hakan ATEŞ

2003-02-01

Full Text Available In this work, automatic controllability of a laboratory-sized friction-welding machine has been investigated. The laboratory-sized friction-welding machine was composed of motor, brake, rotary and constant samples late pliers, and hydraulic unit. In automatic method, welding parameters such as friction time, friction pressure, forge time and forge pressure can be applied sensitively using time relays and contactors. At the end of the experimental study it's observed that automatic control system has been worked successfully.

The development of an electronic system to continually monitor, indicate and control, 'belt slippage' in industrial friction 'V' belt drive transmission systems

International Nuclear Information System (INIS)

Brown, R E

2012-01-01

Belts have been used for centuries as a mechanism to transfer power from some form of drive system to a variety of load systems. Within industry today, many designs of belts but particularly friction, trapezoidal shaped 'V' belts are used and generally transfer power generated by electrical motors to numerous forms of driven load systems. It is suggested that belt systems, through their simplicity are sadly neglected by maintenance functions and generally are left unattended until high degrees of 'belt slippage' through loss of friction or 'belt breakage' provokes maintenance attention. These circumstances are most often identified through the reduced or loss of manufacturing production or the occurrence of catastrophic circumstances such as fire caused through excessive friction/ high belt slippage conditions. Obviously, these situations incur financial losses to companies and in some cases the near loss of the company's main manufacturing plant. Consequently, a satisfactory, viable solution is currently sought by industry to improve on current labour intensive maintenance practices. This paper will present an account of the development of an industrially robust, accurate and repeatable electronic system which continually monitors and indicates the degree of 'slippage' in a 'V' belt drive transmission system and in the circumstance of belt breakage or high belt slippage will enable and control the switching off the drive motor.

Real-Time Dynamic Observation of Micro-Friction on the Contact Interface of Friction Lining

Science.gov (United States)

Zhang, Dekun; Chen, Kai; Guo, Yongbo

2018-01-01

This paper aims to investigate the microscopic friction mechanism based on in situ microscopic observation in order to record the deformation and contact situation of friction lining during the frictional process. The results show that friction coefficient increased with the shear deformation and energy loss of the surfacee, respectively. Furthermore, the friction mechanism mainly included adhesive friction in the high-pressure and high-speed conditions, whereas hysteresis friction was in the low-pressure and low-speed conditions. The mixed-friction mechanism was in the period when the working conditions varied from high pressure and speed to low pressure and speed. PMID:29498677

An asymptotic preserving multidimensional ALE method for a system of two compressible flows coupled with friction

Science.gov (United States)

Del Pino, S.; Labourasse, E.; Morel, G.

2018-06-01

We present a multidimensional asymptotic preserving scheme for the approximation of a mixture of compressible flows. Fluids are modelled by two Euler systems of equations coupled with a friction term. The asymptotic preserving property is mandatory for this kind of model, to derive a scheme that behaves well in all regimes (i.e. whatever the friction parameter value is). The method we propose is defined in ALE coordinates, using a Lagrange plus remap approach. This imposes a multidimensional definition and analysis of the scheme.

Robust Control Design of Wheeled Inverted Pendulum Assistant Robot

Institute of Scientific and Technical Information of China (English)

Magdi S.Mahmoud; Mohammad T.Nasir

2017-01-01

This paper examines the design concept and mobile control strategy of the human assistant robot I-PENTAR（inverted pendulum type assistant robot）. The motion equation is derived considering the non-holonomic constraint of the twowheeled mobile robot. Different optimal control approaches are applied to a linearized model of I-PENTAR. These include linear quadratic regulator（LQR）, linear quadratic Gaussian control（LQG）, H2 control and H∞ control. Simulation is performed for all the approaches yielding good performance results.

Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part II, Friction, heating, and torque.

Science.gov (United States)

Davidson, J A; Schwartz, G; Lynch, G; Gir, S

1988-04-01

In Part I, (J.A. Davidson and G. Schwartz, "Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part I, A review," J. Biomed. Mater. Res., 21, 000-000 (1987) it was shown that lubrication of the artificial hip joint was complex and that long-term performance is governed by the combined wear, creep, and to a lesser extent, oxidation degradation of the articulating materials. Importantly, it was shown that a tendency for heating exists during articulation in the hip joint and that elevated temperatures can increase the wear, creep, and oxidation degradation rate of UHMWPE. The present study was performed to examine closely the propensity to generate heat during articulation in a hip joint simulator. The systems investigated were polished Co-Cr-Mo alloy articulating against UHMWPE, polished alumina ceramic against UHMWPE, and polished alumina against itself. Frictional torque was also evaluated for each system at various levels of applied loads. A walking load history was used in both the frictional heating and torque tests. The majority of tests were performed with 5 mL of water lubricant. However, the effect of various concentrations of hyaluronic acid was also evaluated. Results showed frictional heating to occur in all three systems, reaching an equilibrium after roughly 30 min articulation time. Ceramic systems showed reduced levels of heating compared to the cobalt alloy-UHMWPE system. The level of frictional torque for each system ranked similar to their respective tendencies to generate heat. Hyaluronic acid had little effect, while dry conditions and the presence of small quantities of bone cement powder in water lubricant significantly increased frictional torque.

Trajectory Planning and Optimized Adaptive Control for a Class of Wheeled Inverted Pendulum Vehicle Models.

Science.gov (United States)

Yang, Chenguang; Li, Zhijun; Li, Jing

2013-02-01

In this paper, we investigate optimized adaptive control and trajectory generation for a class of wheeled inverted pendulum (WIP) models of vehicle systems. Aiming at shaping the controlled vehicle dynamics to be of minimized motion tracking errors as well as angular accelerations, we employ the linear quadratic regulation optimization technique to obtain an optimal reference model. Adaptive control has then been developed using variable structure method to ensure the reference model to be exactly matched in a finite-time horizon, even in the presence of various internal and external uncertainties. The minimized yaw and tilt angular accelerations help to enhance the vehicle rider's comfort. In addition, due to the underactuated mechanism of WIP, the vehicle forward velocity dynamics cannot be controlled separately from the pendulum tilt angle dynamics. Inspired by the control strategy of human drivers, who usually manipulate the tilt angle to control the forward velocity, we design a neural-network-based adaptive generator of implicit control trajectory (AGICT) of the tilt angle which indirectly "controls" the forward velocity such that it tracks the desired velocity asymptotically. The stability and optimal tracking performance have been rigorously established by theoretic analysis. In addition, simulation studies have been carried out to demonstrate the efficiency of the developed AGICT and optimized adaptive controller.

Dentoalveolar and skeletal changes associated with the pendulum appliance followed by fixed orthodontic treatment.

Science.gov (United States)

Angelieri, Fernanda; Almeida, Renato Rodrigues de; Almeida, Marcio Rodrigues de; Fuziy, Acácio

2006-04-01

This prospective clinical study analyzed the distalization of maxillary molars achieved by the pendulum appliance and its effect on the anchorage teeth during and after fixed orthodontic treatment. Lateral cephalograms of 22 adolescents (15 girls, 7 boys) taken pretreatment, after distalization, after leveling and aligning, and after fixed orthodontic treatment were evaluated. The initial mean age was 14.5 years (SD = 1.80). The mean time for distalization of the maxillary molars was 5.85 months (SD = 1.82), and the total treatment time was 3.61 years (SD = 1.83). The pendulum appliance moved the maxillary molars distally, but with significant distal inclination, protrusion of the anterior teeth, and increase in lower anterior facial height (LAFH) due to the clockwise mandibular rotation. After fixed orthodontic treatment, the maxillary incisors and the maxillary first premolars and first molars were returned to their pretreatment anteroposterior positions. Thus, at postdistalization, there was 2.1 mm of protrusion of the maxillary first molars, despite the anchorage reinforcement (Nance button and cervical headgear worn at night during fixed appliance therapy). However, at the end of treatment, all patients had Class I molar relationships. The pendulum appliance followed by fixed orthodontic treatment corrected the Class II sagittal relationship, especially due to the dentoalveolar changes secondary to the spontaneous mandibular growth in the anterior direction during fixed appliance treatment.

Modeling Friction Performance of Drill String Torsional Oscillation Using Dynamic Friction Model

Directory of Open Access Journals (Sweden)

Xingming Wang

2017-01-01

Full Text Available Drill string torsional and longitudinal oscillation can significantly reduce axial drag in horizontal drilling. An improved theoretical model for the analysis of the frictional force was proposed based on microscopic contact deformation theory and a bristle model. The established model, an improved dynamic friction model established for drill strings in a wellbore, was used to determine the relationship of friction force changes and the drill string torsional vibration. The model results were in good agreement with the experimental data, verifying the accuracy of the established model. The analysis of the influence of drilling mud properties indicated that there is an approximately linear relationship between the axial friction force and dynamic shear and viscosity. The influence of drill string torsional oscillation on the axial friction force is discussed. The results indicated that the drill string transverse velocity is a prerequisite for reducing axial friction. In addition, low amplitude of torsional vibration speed can significantly reduce axial friction. Then, increasing the amplitude of transverse vibration speed, the effect of axial reduction is not significant. In addition, by involving general field drilling parameters, this model can accurately describe the friction behavior and quantitatively predict the frictional resistance in horizontal drilling.

Two Kinds of Self-Oscillating Circuits Mechanically Demonstrated

OpenAIRE

Shiang-Hwua Yu; Po-Hsun Wu

2015-01-01

This study introduces two types of self-oscillating circuits that are frequently found in power electronics applications. Special effort is made to relate the circuits to the analogous mechanical systems of some important scientific inventions: Galileo’s pendulum clock and Coulomb’s friction model. A little touch of related history and philosophy of science will hopefully encourage curiosity, advance the understanding of self-oscillating systems and satisfy the aspiration ...

Frictional ageing from interfacial bonding and the origins of rate and state friction.

Science.gov (United States)

Li, Qunyang; Tullis, Terry E; Goldsby, David; Carpick, Robert W

2011-11-30

Earthquakes have long been recognized as being the result of stick-slip frictional instabilities. Over the past few decades, laboratory studies of rock friction have elucidated many aspects of tectonic fault zone processes and earthquake phenomena. Typically, the static friction of rocks grows logarithmically with time when they are held in stationary contact, but the mechanism responsible for this strengthening is not understood. This time-dependent increase of frictional strength, or frictional ageing, is one manifestation of the 'evolution effect' in rate and state friction theory. A prevailing view is that the time dependence of rock friction results from increases in contact area caused by creep of contacting asperities. Here we present the results of atomic force microscopy experiments that instead show that frictional ageing arises from the formation of interfacial chemical bonds, and the large magnitude of ageing at the nanometre scale is quantitatively consistent with what is required to explain observations in macroscopic rock friction experiments. The relative magnitude of the evolution effect compared with that of the 'direct effect'--the dependence of friction on instantaneous changes in slip velocity--determine whether unstable slip, leading to earthquakes, is possible. Understanding the mechanism underlying the evolution effect would enable us to formulate physically based frictional constitutive laws, rather than the current empirically based 'laws', allowing more confident extrapolation to natural faults.

Synchronizing chaos in an experimental chaotic pendulum using methods from linear control theory

NARCIS (Netherlands)

Kaart, S.; Schouten, J.C.; Bleek, van den C.M.

1999-01-01

Linear feedback control, specifically model predictive control (MPC), was used successfully to synchronize an experimental chaotic pendulum both on unstable periodic and aperiodic orbits. MPC enables tuning of the controller to give an optimal controller performance. That is, both the fluctuations

Pressure drop and friction factor correlations of supercritical flow

International Nuclear Information System (INIS)

Fang Xiande; Xu Yu; Su Xianghui; Shi Rongrong

2012-01-01

Highlights: ► Survey and evaluation of friction factor models for supercritical flow. ► Survey of experimental study of supercritical flow. ► New correlation of friction factor for supercritical flow. - Abstract: The determination of the in-tube friction pressure drop under supercritical conditions is important to the design, analysis and simulation of transcritical cycles of air conditioning and heat pump systems, nuclear reactor cooling systems and some other systems. A number of correlations for supercritical friction factors have been proposed. Their accuracy and applicability should be examined. This paper provides a comprehensive survey of experimental investigations into the pressure drop of supercritical flow in the past decade and a comparative study of supercritical friction factor correlations. Our analysis shows that none of the existing correlations is completely satisfactory, that there are contradictions between the existing experimental results and thus more elaborate experiments are needed, and that the tube roughness should be considered. A new friction factor correlation for supercritical tube flow is proposed based on 390 experimental data from the available literature, including 263 data of supercritical R410A cooling, 45 data of supercritical R404A cooling, 64 data of supercritical carbon dioxide (CO 2 ) cooling and 18 data of supercritical R22 heating. Compared with the best existing model, the new correlation increases the accuracy by more than 10%.

Evaluation of frictional forces of polycarbonate self-ligating brackets.

Science.gov (United States)

Fernandes, Daniel J; Miguel, José Augusto M; Quintão, Catia C A; Elias, Carlos N

2010-01-01

To evaluate the frictional forces generated by ceramic- (Opal, Ultradent) and glass-fiber-reinforced polycarbonate self-ligating brackets (Oyster, Gestenco) and compare the effectiveness of these ligatureless systems with glass-fiber-reinforced polycarbonate conventional brackets (Blonde, Gestenco). The hypothesis is that there is no difference between frictional forces generated by ceramic- and glass-fiber-reinforced polycarbonate self-ligating and glass-fiber-reinforced polycarbonate conventional brackets. Twelve preadjusted 0.022 3 0.028-inch maxillary canine brackets were tested, divided into three groups: Opal, Oyster, and Blonde. Frictional tests were conducted with the Emic DL 10000 testing machine with a 20 N loadcell for 40 seconds at a 0.5 cm/min speed. Each bracket-wire combination was tested five times. The data generated were analyzed by parametric analysis of variance (one-way ANOVA) and Bonferroni tests. Analysis of variance indicated significant differences for the three groups (Pfrictional forces of the Oyster glass-fiber-reinforced polycarbonate self-ligating brackets were significantly lower (37.0 ± 8.9 cN) than those of the Opal ceramic-reinforced polycarbonate self-ligating brackets (49.5 ± 10.1 cN), while the Blonde glass-fiber-reinforced conventional bracket frictional forces were 105.8 ± 6.4 cN. Oyster glass-fiber-reinforced polycarbonate brackets produced less friction than Opal ceramic-reinforced polycarbonate brackets. The polycarbonate ligatureless system showed significantly lower frictional forces compared to Blonde conventional polycarbonate brackets tied with elastomeric ligatures. The study rejected the initial hypothesis because there are significant differences of frictional forces among the tested systems. © 2010 BY QUINTESSENCE PUBLISHING CO, INC.

Investigation of squeal noise under positive friction characteristics condition provided by friction modifiers

Science.gov (United States)

Liu, Xiaogang; Meehan, Paul A.

2016-06-01

Field application of friction modifiers on the top of rail has been shown to effectively curb squeal and reduce lateral forces, but performance can be variable, according to other relevant research. Up to now, most investigations of friction modifiers were conducted in the field, where it is difficult to control or measure important parameters such as angle of attack, rolling speed, adhesion ratio etc. In the present investigation, the effect of different friction modifiers on the occurrence of squeal was investigated on a rolling contact two disk test rig. In particular, friction-creep curves and squeal sound pressure levels were measured under different rolling speeds and friction modifiers. The results show friction modifiers can eliminate or reduce the negative slope of friction-creep curves, but squeal noise still exists. Theoretical modelling of instantaneous creep behaviours reveals a possible reason why wheel squeal still exists after the application of friction modifiers.

Study of nano-scale friction using vortices in superconductors

International Nuclear Information System (INIS)

Maeda, A.; Nakamura, D.; Kitano, H.; Matsumura, H.

2007-01-01

Toward the microscopic understanding of physics of friction at the solid interface, we use the dynamics of driven vortices of superconductor as a new model system. We measured the static friction as a function of the aging time, and compared with the kinetic friction as a function of velocity for the driven vortex lattice of La 1.85 Sr 0.15 CuO 4 . No definite relationship, such as the one proposed for the friction of thick papers, was observed. This supports our previous proposal of the critical phenomena view that the non-Amontons-Coulomb-like behavior of the kinetic friction is a broadened dynamic transition between the static and kinetic regimes

Clutches using engineering ceramics as friction material

Energy Technology Data Exchange (ETDEWEB)

Albers, A.; Arslan, A.; Mitariu, M. [Universitaet Karlsruhe (T.H.), IPEK - Institut fuer Produktentwicklung, Kaiserstr. 10, 76131 Karlsruhe (Germany)

2005-03-01

The experimental and constructive results illustrate that engineering ceramic materials have a high potential in the field of dry running friction systems. According to first estimations, it is possible to build the vehicle clutch 53 % smaller or to transmit up to 180 % higher torque with the same size by an appropriate selection of the system friction pairing and an adequate ceramic design [1, 2]. The friction coefficient characteristic (decreasing friction coefficient above sliding speed) is unfavourable with regard to comfort (self-induced grab oscillations [3]) of the vehicle clutch. Furthermore, it is important to select the test procedure of the experimental analyses to be as close to the system as possible in order to obtain exact information concerning the target system. (Abstract Copyright [2005], Wiley Periodicals, Inc.) [German] Die experimentellen und konstruktiven Ergebnisse haben gezeigt, dass ingenieurkeramische Werkstoffe ein hohes Potenzial im Bereich der trockenlaufenden Friktionssysteme haben. Durch geeignete Wahl der Systemreibpaarung und eine keramikgerechte Konstruktion ist es nach ersten Abschaetzungen moeglich, die Kfz-Kupplung um 53 % kleiner zu bauen bzw. bei gleicher Groesse bis zu 180 % hoehere Drehmomente zu uebertragen [1, 2]. Die Reibungszahlcharakteristik (fallende Reibungszahl ueber Gleitgeschwindigkeit) ist im Hinblick auf Komfort (selbsterregte Rupfschwingungen [3]) fuer die Kraftfahrzeugkupplung unguenstig. Des Weiteren ist es wichtig, die Versuchsfuehrung der experimentellen Untersuchungen so systemnah wie moeglich zu waehlen, um genauere Aussagen auf das Zielsystem zu erhalten. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Simulating a Rotational Inverted Pendulum Model by using Matlab and Easy Java Simulations

Directory of Open Access Journals (Sweden)

Oscar O. Rodríguez-Díaz

2012-06-01

Full Text Available This paper presents the analysis, design and construction of a virtual simulator, in which the behavior of a non-lineal system as the rotational inverted pendulum is represented graphically in an interface. This uses an Applet of Java that allows users change parameters of the model. The use of this tool is a good alternative for bridging the gap between the theoretical concepts and the actual behaviors of a process. The server uses Matlab/Simulink as a calculation engine, taking advantage of its ease for constructing non-lineal models by using block diagrams. The user interface has been created by a free software tool called Easy Java Simulations that allows designing interactive graphical applications as 3D interfaces. Easy Java results an interesting tool for automatic control system education.

Aspects Regarding Evaluation of Friction Effects in Robotic Systems

Directory of Open Access Journals (Sweden)

Florina-Carmen Ciornei

2016-06-01

Full Text Available The paper reveals both experimentally and by numerical simulation that modelling the dynamic behaviour of a robotic system that contains pairs where spin motion exists, finally leads towards nonlinear dynamical models. Despite the fact that academic monographs upon rigid mechanics use the hypothesis that spinning torque depends linearly on the normal force, a simple experiment contradicts this assumption. To this end, the motion of an axi-symmetric body making two contacts with dry friction is analyzed. The qualitative non-linearity of spinning torque on loading force dependence is validated in the end by the modelling of the test using dynamical simulation software.

A Study of Seismic Capacity of Nuclear Equipment with Seismic Isolation System

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Kyu; Choun, Young Sun; Choi, In Kil; Seo, Jeong Moon

2004-05-15

In this study, the base isolation systems for equipment are presented and the responses of each isolation system are investigated. As for the base isolation systems, a natural rubber bearing (NRB), a high damping rubber bearing (HDRB) and a friction pendulum system (FPS) are selected. The shaking table tests are carried out for three kinds of structural types. As input motions, artificial time histories enveloping the US NRC RG 1.60 spectrum and the probability-based scenario earthquake spectra developed for the Korean nuclear power plant site as well as a typical near-fault earthquake record are used. Uniaxial, biaxial, and triaxial excitations are conducted with PGAs of 0.05, 0.1, 0.2 and 0.25g. Acceleration responses are measured at the top of the equipment model and the floors using an accelerometer. The reduction of the seismic forces transmitted to the equipment models are determined for different isolation systems and input motions.

A Study of Seismic Capacity of Nuclear Equipment with Seismic Isolation System

International Nuclear Information System (INIS)

Kim, Min Kyu; Choun, Young Sun; Choi, In Kil; Seo, Jeong Moon

2004-05-01

In this study, the base isolation systems for equipment are presented and the responses of each isolation system are investigated. As for the base isolation systems, a natural rubber bearing (NRB), a high damping rubber bearing (HDRB) and a friction pendulum system (FPS) are selected. The shaking table tests are carried out for three kinds of structural types. As input motions, artificial time histories enveloping the US NRC RG 1.60 spectrum and the probability-based scenario earthquake spectra developed for the Korean nuclear power plant site as well as a typical near-fault earthquake record are used. Uniaxial, biaxial, and triaxial excitations are conducted with PGAs of 0.05, 0.1, 0.2 and 0.25g. Acceleration responses are measured at the top of the equipment model and the floors using an accelerometer. The reduction of the seismic forces transmitted to the equipment models are determined for different isolation systems and input motions

Friction and Wear Behavior of Several Hard Materials

NARCIS (Netherlands)

Quercia Bianchi, G.; Grigorescu, I.C.; Di Rauso, C.; Contreras, H.; Gutierrez, D.

2001-01-01

Sliding friction, abrasion and erosion tests were performed on several materials: cemented carbides, partially stabilized zirconia (Mg–PSZ), electroless Ni–P coatings and SAE 4140 steel as reference material. Sliding friction test was carried out in a pin-on-disk system. A micro-abrasion test was

Friction analysis of kinetic schemes : the friction coefficient

NARCIS (Netherlands)

Lolkema, Juke S.

1995-01-01

Friction analysis is proposed as the application of general control analysis to single enzymes to describe the control of elementary kinetic steps on the overall catalytic rate. For each transition, a friction coefficient is defined that measures the sensitivity of the turnover rate to the free

Nonlinear feedback control of chaotic pendulum in presence of saturation effect

Energy Technology Data Exchange (ETDEWEB)

Alasty, Aria [Center of Excellence in Design, Robotics, and Automation (CEDRA), Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, Tehran 1458889694 (Iran, Islamic Republic of)]. E-mail: aalasti@sharif.edu; Salarieh, Hassan [Center of Excellence in Design, Robotics, and Automation (CEDRA), Department of Mechanical Engineering, Sharif University of Technology, Azadi Avenue, Tehran 1458889694 (Iran, Islamic Republic of)]. E-mail: salarieh@mehr.sharif.edu

2007-01-15

In present paper, a feedback linearization control is applied to control a chaotic pendulum system. Tracking the desired periodic orbits such as period-one, period-two, and period-four orbits is efficiently achieved. Due to the presence of saturation in real world control signals, the stability of controller is investigated in presence of saturation and sufficient stability conditions are obtained. At first feedback linearization control law is designed, then to avoid the singularity condition, a saturating constraint is applied to the control signal. The stability conditions are obtained analytically. These conditions must be investigated for each specific case numerically. Simulation results show the effectiveness and robustness of proposed controller. A major advantage of this method is its shorter chaotic transient time in compare to other methods such as OGY and Pyragas controllers.

Dynamics of translational friction in needle-tissue interaction during needle insertion.

Science.gov (United States)

Asadian, Ali; Patel, Rajni V; Kermani, Mehrdad R

2014-01-01

In this study, a distributed approach to account for dynamic friction during needle insertion in soft tissue is presented. As is well known, friction is a complex nonlinear phenomenon. It appears that classical or static models are unable to capture some of the observations made in systems subjected to significant frictional effects. In needle insertion, translational friction would be a matter of importance when the needle is very flexible, or a stop-and-rotate motion profile at low insertion velocities is implemented, and thus, the system is repeatedly transitioned from a pre-sliding to a sliding mode and vice versa. In order to characterize friction components, a distributed version of the LuGre model in the state-space representation is adopted. This method also facilitates estimating cutting force in an intra-operative manner. To evaluate the performance of the proposed family of friction models, experiments were conducted on homogeneous artificial phantoms and animal tissue. The results illustrate that our approach enables us to represent the main features of friction which is a major force component in needle-tissue interaction during needle-based interventions.

Method for Friction Force Estimation on the Flank of Cutting Tools

Directory of Open Access Journals (Sweden)

Luis Huerta

2017-01-01

Full Text Available Friction forces are present in any machining process. These forces could play an important role in the dynamics of the system. In the cutting process, friction is mainly present in the rake face and the flank of the tool. Although the one that acts on the rake face has a major influence, the other one can become also important and could take part in the stability of the system. In this work, experimental identification of the friction on the flank is presented. The experimental determination was carried out by machining aluminum samples in a CNC lathe. As a result, two friction functions were obtained as a function of the cutting speed and the relative motion of the contact elements. Experiments using a worn and a new insert were carried out. Force and acceleration were recorded simultaneously and, from these results, different friction levels were observed depending on the cutting parameters, such as cutting speed, feed rate, and tool condition. Finally, a friction model for the flank friction is presented.

On the nature of the static friction, kinetic friction and creep

DEFF Research Database (Denmark)

Persson, B. N. J.; Albohr, O.; Mancosu, F.

2003-01-01

of capillary bridges. However, there is no single value of the static friction coefficient, since it depends upon the initial dwell time and on rate of starting.We argue that the correct basis for the Coulomb friction law, which states that the friction force is proportional to the normal load...

Enhanced surface friction coefficient and hydrophobicity of TPE substrates using an APPJ system

Energy Technology Data Exchange (ETDEWEB)

Sainz-García, Elisa, E-mail: elisa.sainzg@unirioja.es; Alba-Elías, Fernando, E-mail: fernando.alba@unirioja.es; Múgica-Vidal, Rodolfo, E-mail: rodolfo.mugica@alum.unirioja.es; González-Marcos, Ana, E-mail: ana.gonzalez@unirioja.es

2015-02-15

Highlights: • Coatings on thermoplastic elastomers by atmospheric pressure plasma jet. • Study of influence of APTES and FLUSI percentage on the coating's properties. • The best sample (AF{sub 75}) used 75% of APTES and 25% of FLUSI as precursor mixture. • Sample AF{sub 75} reduced a 51.5% the FC and increased a 4.4% the WCA. - Abstract: An APPJ system was used to deposit a coating that combines a low friction coefficient with a high water contact angle (WCA) on a thermoplastic elastomer substrate (TPE) that is used in automotive profiling. The main drawback of this research is that groups that improve the hydrophobicity of the surface worsen its tribological properties. To overcome this, this study explored the use of various mixtures of differing proportions of two precursors. They were a siloxane, aminopropyltriethoxysilane (APTES) that was used to reduce the friction coefficient by its content of SiO{sub x} and a fluorinated compound, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FLUSI) that was used to improve the water-repellency characteristics, due to the presence of CF{sub 2} long chains. The coatings were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), dynamic Water Contact Angle (WCA), stability tests and tribological tests. It was found that an increase of the absorbance area under the SiOSi peak and inorganic groups is related to lower friction coefficients. On the other hand, the higher the CF{sub 2} percentage is, the higher the WCA is. The sample that was coated with 25% of FLUSI and 75% of APTES combined the improvements of both functional properties, the friction coefficient and the WCA. It has an average friction coefficient that is (0.530 ± 0.050) 51.5% lower and a WCA that is (θ{sub adv} = 119.8° ± 4.75) 4.4% higher than the uncoated TPE sample. A satisfactory

Study of a Car Body Tilting System Using a Variable Link Mechanism: Fundamental Characteristics of Pendulum Motion and Strategy for Perfect Tilting

Science.gov (United States)

Yoshida, Hidehisa; Nagai, Masao

This paper analyzes the fundamental dynamic characteristics of a tilting railway vehicle using a variable link mechanism for compensating both the lateral acceleration experienced by passengers and the wheel load imbalance between the inner and outer rails. The geometric relations between the center of rotation, the center of gravity, and the positions of all four links of the tilting system are analyzed. Then, equations of the pendulum motions of the railway vehicle body with a four-link mechanism are derived. A theoretically discussion is given on the geometrical shapes employed in the link mechanism that can simultaneously provide zero lateral acceleration and zero wheel load fluctuation. Then, the perfect tilting condition, which is the control target of the feedforward tilting control, is derived from the linear equation of tilting motion.

Results of automatic system implementation for the friction control rods execution in Cofrentes nuclear power plant

International Nuclear Information System (INIS)

Curiel, M.; Palomo, M. J.; Urrea, M.; Arnaldos, A.

2010-10-01

The purpose of this presentation is to show the obtained results in Cofrentes nuclear power plant (Spain) of control rods Pcc/24 friction test procedure. In order to perform this, a control rod friction test system has been developed. Principally, this system consists on software and data acquisition hardware that obtains and analyzes the control rod pressure variation on which the test is being made. The Pcc/24 procedure objective is to detect an excessive friction in the control rod movement that could cause a control rod drive movement slower than usual. This test is necessary every time that an anomalous alteration is produced in the reactor core that could affect to a fuel rod, and it is executed before the time measure of control rods rapid scram test of the affected rods. This test has to be carried out to all the reactor control rods and takes valuable time during plant refuelling. So, by means of an automatic system to perform the test, we obtain an important time saving during refuelling. On the other hand, the on-line monitoring of the control rod insertion and changes in differential pressure, permits a control rod operation fast and safe validation. Moreover, an automatic individual report of every rod is generated by the system and a final global result report of the entire test developed in refuelling is generated. The mentioned reports can be attached directly to the procedure documents obtaining an office data processing important saving time. (Author)

Results of automatic system implementation for the friction control rods execution in Cofrentes nuclear power plant

Energy Technology Data Exchange (ETDEWEB)

Curiel, M. [Logistica y Acondicionamientos Industriales SAU, Sorolla Center, local 10, Av. de las Cortes Valencianas, 46015 Valencia (Spain); Palomo, M. J. [ISIRYM, Universidad Politecnica de Valencia, Camino de Vera s/n, Valencia (Spain); Urrea, M. [Iberdrola Generacion S. A., Central Nuclear Cofrentes, Carretera Almansa Requena s/n, 04662 Cofrentes, Valencia (Spain); Arnaldos, A., E-mail: m.curiel@lainsa.co [TITANIA Servicios Tecnologicos SL, Sorolla Center, local 10, Av. de las Cortes Valencianas No. 58, 46015 Valencia (Spain)

2010-10-15

The purpose of this presentation is to show the obtained results in Cofrentes nuclear power plant (Spain) of control rods Pcc/24 friction test procedure. In order to perform this, a control rod friction test system has been developed. Principally, this system consists on software and data acquisition hardware that obtains and analyzes the control rod pressure variation on which the test is being made. The Pcc/24 procedure objective is to detect an excessive friction in the control rod movement that could cause a control rod drive movement slower than usual. This test is necessary every time that an anomalous alteration is produced in the reactor core that could affect to a fuel rod, and it is executed before the time measure of control rods rapid scram test of the affected rods. This test has to be carried out to all the reactor control rods and takes valuable time during plant refuelling. So, by means of an automatic system to perform the test, we obtain an important time saving during refuelling. On the other hand, the on-line monitoring of the control rod insertion and changes in differential pressure, permits a control rod operation fast and safe validation. Moreover, an automatic individual report of every rod is generated by the system and a final global result report of the entire test developed in refuelling is generated. The mentioned reports can be attached directly to the procedure documents obtaining an office data processing important saving time. (Author)

Physically representative atomistic modeling of atomic-scale friction

Science.gov (United States)

Dong, Yalin

Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a door to understand macroscopic friction from the most bottom atomic level, and therefore serves as a bridge between science and engineering. This thesis focuses on solid/solid atomic friction and its associated energy dissipation through theoretical analysis, atomistic simulation, transition state theory, and close collaboration with experimentalists. Reduced-order models have many advantages for its simplification and capacity to simulating long-time event. We will apply Prandtl-Tomlinson models and their extensions to interpret dry atomic-scale friction. We begin with the fundamental equations and build on them step-by-step from the simple quasistatic one-spring, one-mass model for predicting transitions between friction regimes to the two-dimensional and multi-atom models for describing the effect of contact area. Theoretical analysis, numerical implementation, and predicted physical phenomena are all discussed. In the process, we demonstrate the significant potential for this approach to yield new fundamental understanding of atomic-scale friction. Atomistic modeling can never be overemphasized in the investigation of atomic friction, in which each single atom could play a significant role, but is hard to be captured experimentally. In atomic friction, the

Microscopic Stern-Gerlach effect and spin-orbit pendulum

International Nuclear Information System (INIS)

Rozmej, P.; Arvieu, R.

1996-01-01

The motion of a particle with spin in spherical harmonic oscillator potential with spin-orbit interaction is discussed. The attention is focused on the spatial motion of wave packets. The particular case of wave packets moving along the circular orbits for which the most transparent and pedagogical description is possible is considered. The splitting of the wave packets into two components moving differently along classical orbits reflects a strong analogy with the Stern-Gerlach experiment. The periodic transfer of average angular momentum between spin and orbital subspaces accompanying this time evolution is called the spin-orbit pendulum. (author). 6 refs, 3 figs

Foucault's Pendulum, Analog for an Electron Spin State

Science.gov (United States)

Linck, Rebecca

2012-11-01

The classical Lagrangian that describes the coupled oscillations of Foucault's pendulum presents an interesting analog to an electron's spin state in an external magnetic field. With a simple modification, this classical Lagrangian yields equations of motion that directly map onto the Schrodinger-Pauli Equation. This analog goes well beyond the geometric phase, reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

Friction behavior of ceramic injection-molded (CIM) brackets.

Science.gov (United States)

Reimann, Susanne; Bourauel, Christoph; Weber, Anna; Dirk, Cornelius; Lietz, Thomas

2016-07-01

Bracket material, bracket design, archwire material, and ligature type are critical modifiers of friction behavior during archwire-guided movement of teeth. We designed this in vitro study to compare the friction losses of ceramic injection-molded (CIM) versus pressed-ceramic (PC) and metal injection-molded (MIM) brackets-used with different ligatures and archwires-during archwire-guided retraction of a canine. Nine bracket systems were compared, including five CIM (Clarity™ and Clarity™ ADVANCED, both by 3M Unitek; discovery(®) pearl by Dentaurum; Glam by Forestadent; InVu by TP Orthodontics), two PC (Inspire Ice by Ormco; Mystique by DENTSPLY GAC), and two MIM (discovery(®) and discovery(®) smart, both by Dentaurum) systems. All of these were combined with archwires made of either stainless steel or fiberglass-reinforced resin (remanium(®) ideal arch or Translucent pearl ideal arch, both by Dentaurum) and with elastic ligatures or uncoated or coated stainless steel (all by Dentaurum). Archwire-guided retraction of a canine was simulated with a force of 0.5 N in the orthodontic measurement and simulation system (OMSS). Friction loss was determined by subtracting the effective orthodontic forces from the applied forces. Based on five repeated measurements performed on five brackets each, weighted means were calculated and evaluated by analysis of variance and a Bonferroni post hoc test with a significance level of 0.05. Friction losses were significantly (p brackets used with a stainless-steel ligature and the resin archwire. No critical difference to friction behavior was apparent between the various manufacturing technologies behind the bracket systems.

Static friction of porous bioceramic beta-TCP on intestinal mucus films.

Science.gov (United States)

Wang, Xin-Yu; Han, Ying-Chao; Jiang, Xin; Dai, Hong-Lian; Li, Shi-Pu

2006-09-01

The static friction behavior between a porous bioceramic material and an intestinal mucus film was investigated in order to develop a new intestine robotic endoscope. Here, the friction couple is porous beta-tricalcium phosphate (beta-TCP) and an artificial intestine mucus film. The effect of pore size of the beta-TCP material on the friction behavior is investigated. The results illustrated that in this friction system there is a relatively small normal force upon the intestinal mucus film of the intestine wall during locomotion. The maximum static friction force in this friction couple varies with the pore size of the porous beta-TCP material.

Static friction of porous bioceramic β-TCP on intestinal mucus films

International Nuclear Information System (INIS)

Wang Xinyu; Han Yingchao; Jiang Xin; Dai Honglian; Li Shipu

2006-01-01

The static friction behavior between a porous bioceramic material and an intestinal mucus film was investigated in order to develop a new intestine robotic endoscope. Here, the friction couple is porous β-tricalcium phosphate (β-TCP) and an artificial intestine mucus film. The effect of pore size of the β-TCP material on the friction behavior is investigated. The results illustrated that in this friction system there is a relatively small normal force upon the intestinal mucus film of the intestine wall during locomotion. The maximum static friction force in this friction couple varies with the pore size of the porous β-TCP material

Stick-slip chaos in a mechanical oscillator with dry friction

Science.gov (United States)

Kousaka, Takuji; Asahara, Hiroyuki; Inaba, Naohiko

2018-03-01

This study analyzes a forced mechanical dynamical system with dry friction that can generate chaotic stick-slip vibrations. We find that the dynamics proposed by Yoshitake et al. [Trans. Jpn. Soc. Mech. Eng. C 61, 768 (1995)] can be expressed as a nonautonomous constraint differential equation owing to the static friction force. The object is constrained to the surface of a moving belt by a static friction force from when it sticks to the surface until the force on the object exceeds the maximal static friction force. We derive a 1D Poincaré return map from the constrained mechanical system, and prove numerically that this 1D map has an absolutely continuous invariant measure and a positive Lyapunov exponent, providing strong evidence for chaos.

Accurate solutions of Colebrook-White's friction factor formulae ...

African Journals Online (AJOL)

Estimations of friction factor (Ff) in pipeline systems and fluid transport are essential ingredients in engineering fields and processes. In this paper explicit friction factor formulae (Fff) were proposed and evaluated with an aim of developing error free Fff. General Fff that relate Ff, Reynolds number (Re) and relative roughness ...

Chemical origins of frictional aging.

Science.gov (United States)

Liu, Yun; Szlufarska, Izabela

2012-11-02

Although the basic laws of friction are simple enough to be taught in elementary physics classes and although friction has been widely studied for centuries, in the current state of knowledge it is still not possible to predict a friction force from fundamental principles. One of the highly debated topics in this field is the origin of static friction. For most macroscopic contacts between two solids, static friction will increase logarithmically with time, a phenomenon that is referred to as aging of the interface. One known reason for the logarithmic growth of static friction is the deformation creep in plastic contacts. However, this mechanism cannot explain frictional aging observed in the absence of roughness and plasticity. Here, we discover molecular mechanisms that can lead to a logarithmic increase of friction based purely on interfacial chemistry. Predictions of our model are consistent with published experimental data on the friction of silica.

Status of Stellite 6 friction testing

International Nuclear Information System (INIS)

Watkins, J.C.; DeWall, K.G.

1998-01-01

For the past several years, researchers at the Idaho National Engineering and Environmental Laboratory, under the sponsorship of the US Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, have been investigating the performance of motor-operated valves subjected to design basis flow and pressure loads. Part of this research addresses the friction that occurs at the interface between the valve disc and the valve body seats during operation of a gate valve. In most gate valves, these surfaces are hardfaced with Stellite 6, a cobalt-based alloy. Analytical methods exist for predicting the thrust needed to operate these valves at specific pressure conditions. To produce accurate valve thrust predictions, the analyst must have a reasonably accurate, though conservative, estimate of the coefficient of friction at the disc-to-seat interface. One of the questions that remains to be answered is whether, and to what extent, aging of the disc and seat surfaces effects the disc-to-seat coefficient of friction. Specifically, does the environment in a nuclear plants piping system cause the accumulation of an oxide film on these surfaces that increases the coefficient of friction; and if so, how great is the increase? This paper presents results of specimen tests addressing this issue, with emphasis on the following: (1) the characteristics and thickness of the oxide film that develops on Stellite 6 as it ages; (2) the change in the friction coefficient of Stellite 6 as it ages, including the question of whether the friction coefficient eventually reaches a plateau; and (3) the effect in-service cycling has on the characteristics and thickness of the oxide film and on the friction coefficient

Novel friction law for the static friction force based on local precursor slipping.

Science.gov (United States)

Katano, Yu; Nakano, Ken; Otsuki, Michio; Matsukawa, Hiroshi

2014-09-10

The sliding of a solid object on a solid substrate requires a shear force that is larger than the maximum static friction force. It is commonly believed that the maximum static friction force is proportional to the loading force and does not depend on the apparent contact area. The ratio of the maximum static friction force to the loading force is called the static friction coefficient µM, which is considered to be a constant. Here, we conduct experiments demonstrating that the static friction force of a slider on a substrate follows a novel friction law under certain conditions. The magnitude of µM decreases as the loading force increases or as the apparent contact area decreases. This behavior is caused by the slip of local precursors before the onset of bulk sliding and is consistent with recent theory. The results of this study will develop novel methods for static friction control.

Pendulum support of the W7-X plasma vessel: Design, tests, manufacturing, assembly, critical aspects, status

Energy Technology Data Exchange (ETDEWEB)

Missal, B., E-mail: bernd.missal@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Leher, F.; Schiller, T. [MAN Diesel and Turbo SE, Werftstraße 17, 94469 Deggendorf (Germany); Friedrich, P. [Universität Rostock, FB Maschinenbau und Schiffstechnik, Albert-Einsteins-Straße 2, 18051 Rostock (Germany); Capriccioli, A. [ENEA Frascati, Fusion Technology Unit, Frascati (Italy)

2014-10-15

Highlights: • Plasma vessel support has to allow vertical adjustment and horizontal passive movement. • Planar sliding tables with PTFE do not fulfill all requirements. • Pendulums can fulfill all requirements. • Geometry and material of spherical bearings had to be optimized in calculations and tests. • Optimized pendulums were manufactured and assembled. - Abstract: The superconducting helical advanced stellarator Wendelstein 7-X (W7-X) is under construction at the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald, Germany. The three dimensional shape of plasma will be generated by 50 non-planar magnetic coils. The plasma vessel geometry follows exactly this three dimensional shape of plasma. To ensure the superconductivity of coils a cryo vacuum has to be generated. Therefore the coils and their support structure are enclosed within the outer vessel. Plasma vessel, coil structures and outer vessel have to be supported separately. This paper will describe the vertical supports of plasma vessel which have to fulfill two special requirements, vertical adjustability and horizontal mobility. These two tasks will be carried out by plasma vessel supports (PVS) with hydraulic cylinders, special sliding tables during assembly and pendulum supports during operating phase. The paper will give an overview of design, calculation, tests, fabrication, assembly, critical aspects and status of PVS.

An Extension of the Burridge-Knopoff Model for Friction

Directory of Open Access Journals (Sweden)

Veturia Chiroiu

2015-09-01

Full Text Available The paper presents an extension of the Burridge-Knopoff (BK model with an additional kinetic equation for the friction force in order to reproduce the both the velocity weakening friction between the tire and the road and the increase of static friction with time when the car is not moving. The BK was initially proposed to investigate statistical properties of earthquakes. In this model the sliding force decreases monotonously from a reference value, and the static friction can have negative values to prevent back sliding. The stability of the system is affected and the sliding regime at small sliding velocities and large stiffness cannot be reproduced. The extended model BK assures the stability of the diagram sliding-stationary sliding, and correctly reproduces the stability diagram for sliding friction under various loading conditions.

Quantum Drude friction for time-dependent density functional theory

Science.gov (United States)

Neuhauser, Daniel; Lopata, Kenneth

2008-10-01

Friction is a desired property in quantum dynamics as it allows for localization, prevents backscattering, and is essential in the description of multistage transfer. Practical approaches for friction generally involve memory functionals or interactions with system baths. Here, we start by requiring that a friction term will always reduce the energy of the system; we show that this is automatically true once the Hamiltonian is augmented by a term of the form ∫a(q ;n0)[∂j(q,t)/∂t]ṡJ(q)dq, which includes the current operator times the derivative of its expectation value with respect to time, times a local coefficient; the local coefficient will be fitted to experiment, to more sophisticated theories of electron-electron interaction and interaction with nuclear vibrations and the nuclear background, or alternately, will be artificially constructed to prevent backscattering of energy. We relate this term to previous results and to optimal control studies, and generalize it to further operators, i.e., any operator of the form ∫a(q ;n0)[∂c(q,t)/∂t]ṡC(q)dq (or a discrete sum) will yield friction. Simulations of a small jellium cluster, both in the linear and highly nonlinear excitation regime, demonstrate that the friction always reduces energy. The energy damping is essentially double exponential; the long-time decay is almost an order of magnitude slower than the rapid short-time decay. The friction term stabilizes the propagation (split-operator propagator here), therefore increasing the time-step needed for convergence, i.e., reducing the overall computational cost. The local friction also allows the simulation of a metal cluster in a uniform jellium as the energy loss in the excitation due to the underlying corrugation is accounted for by the friction. We also relate the friction to models of coupling to damped harmonic oscillators, which can be used for a more sophisticated description of the coupling, and to memory functionals. Our results open the

Optimization of Membership Functions for the Fuzzy Controllers of the Water Tank and Inverted Pendulum with Differents PSO Variants

Directory of Open Access Journals (Sweden)

Patricia Melin

2013-11-01

Full Text Available In this paper the Particle Swarm Optimization metaheuristic and two of its variants (inertia weight and constriction coefficient are used as an optimization strategy for the design of optimal membership functions of fuzzy control systems for the water tank and inverted pendulum benchmark problems. Each variant has its own advantages in the algorithm, allowing the exploration and exploitation in different ways and this allows finding the optimal solution in a better way.

Nano-friction behavior of phosphorene.

Science.gov (United States)

Bai, Lichun; Liu, Bo; Srikanth, Narasimalu; Tian, Yu; Zhou, Kun

2017-09-01

Nano-friction of phosphorene plays a significant role in affecting the controllability and efficiency of applying strain engineering to tune its properties. So far, the friction behavior of phosphorene has not been studied. This work studies the friction of single-layer and bilayer phosphorene on an amorphous silicon substrate by sliding a rigid tip. For the single-layer phosphorene, it is found that its friction is highly anisotropic, i.e. the friction is larger along the armchair direction than that along the zigzag direction. Moreover, pre-strain of the phosphorene also exhibits anisotropic effects. The friction increases with the pre-strain along the zigzag direction, but decreases with that along the armchair direction. Furthermore, the strong adhesion between the phosphorene and its substrate increases the friction between the phosphorene and the tip. For bilayer phosphorene, its friction highly depends on its stacking mode, which determines the contact interface with a commensurate or incommensurate pattern. This friction behavior is quite unique and greatly differs from that of graphene and molybdenum disulfide. Detailed analysis reveals that this behavior results from the combination effect of the friction contact area, the potential-energy profile of phosphorene, and its unique elongation.

Frictional Heating with Time-Dependent Specific Power of Friction

Directory of Open Access Journals (Sweden)

Topczewska Katarzyna

2017-06-01

Full Text Available In this paper analytical solutions of the thermal problems of friction were received. The appropriate boundary-value problems of heat conduction were formulated and solved for a homogeneous semi–space (a brake disc heated on its free surface by frictional heat fluxes with different and time-dependent intensities. Solutions were obtained in dimensionless form using Duhamel's theorem. Based on received solutions, evolution and spatial distribution of the dimensionless temperature were analyzed using numerical methods. The numerical results allowed to determine influence of the time distribution of friction power on the spatio-temporal temperature distribution in brake disc.

Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles.

Science.gov (United States)

Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

2016-07-08

The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism.

An Experimental Investigation of the Effect of Corrosion on Dry Friction Noise

International Nuclear Information System (INIS)

Baek, Jongsu; Kang, Jaeyoung

2015-01-01

This study investigates the friction noise characteristic in relation to the corrosion of metal by using the frictional reciprocating and pin-on-disk system. From the experiments, it is found that the corrosion of metal advances the onset time and increases the magnitude of friction noise. Further, it is observed that the effect of corrosion on friction noise stems from the alteration of tribo-surface during repetitive frictional motion. The alteration of the corrosive contact surface induces a negative friction-velocity slope, by which the corrosion of metal can generate dynamic instability faster than non-corrosion of metal

Frictional Forces Required for unrestrained locomotion in dairy cattle

NARCIS (Netherlands)

Tol, van der P.P.J.; Metz, J.H.M.; Noordhuizen-Stassen, E.N.; Back, W.; Braam, C.R.

2005-01-01

Most free-stall housing systems in the Netherlands are equipped with slatted or solid concrete floors with manure scrapers. A slipping incident occurs when the required coefficient of friction (RCOF) exceeds the coefficient of friction (COF) at the claw–floor interface. An experiment was conducted

Frictional behaviour of high performance fibrous tows: Friction experiments

NARCIS (Netherlands)

Cornelissen, Bo; Rietman, Bert; Akkerman, Remko

2013-01-01

Tow friction is an important mechanism in the production and processing of high performance fibrous tows. The frictional behaviour of these tows is anisotropic due to the texture of the filaments as well as the tows. This work describes capstan experiments that were performed to measure the

On the mechanical friction losses occurring in automotive differential gearboxes.

Science.gov (United States)

Antoni, Grégory

2014-01-01

In the automobile industry, the mechanical losses resulting from friction are largely responsible for various kinds of surface damage, such as the scuffing occurring in some mechanical assemblies. These scuffing processes seem to be due to a local loss of lubrication between certain mechanical elements of the same assembly, leading to a sharp increase in the friction, which can lead to a surface and volume damage in some of them, and even can cause, in the worst case, the whole destruction of the mechanical system if it has continued to operate. Predicting and checking the occurrence of this kind of undesirable phenomena, especially in some principal systems of the vehicle, represents nowadays, a crucial challenge in terms of automobile reliability and safety. This study focuses on the mechanical friction losses liable to occur in differential automobile gearboxes, which can lead in the long term to the scuffing of these mechanical systems. The friction losses involved were modeled, using a simple analytical approach, which is presented and discussed.

Three-dimensional visualization of material flow during friction stir welding by two pairs of X-ray transmission systems

International Nuclear Information System (INIS)

Morisada, Y.; Fujii, H.; Kawahito, Y.; Nakata, K.; Tanaka, M.

2011-01-01

Material flow during friction stir welding is crucial to obtaining sound joints. However, this phenomenon is still not fully understood despite many investigations and numerous models. In this study, the material flow is three-dimensionally visualized by X-ray radiography using a tiny spherical tungsten tracer. The movement of the tracer during the friction stir welding is observed by two pairs of X-ray transmission real-time imaging systems. The three-dimensional material flow is obtained by following the locus of the tracer.

Results of automatic system implementation for the friction control rods execution in Cofrentes nuclear power plant

International Nuclear Information System (INIS)

Palomo, M.; Urrea, M.; Arnaldos, A.

2011-01-01

The purpose of this presentation is to show the obtained results in Cofrentes Nuclear Power Plant (Spain) of Control Rods PCC/24 Friction Test Procedure. In order to perform this, a Control Rod Friction Test System has been developed. Principally, this system consists on software and data acquisition hardware that obtains and analyzes the control rod pressure variation on which the test is being made. The PCC/24 Procedure objective is to detect an excessive friction in the control rod movement that could cause a CRD (Control Rod Drive) movement slower than usual. This test is necessary every time that an anomalous alteration is produced in the reactor core that could affect to a fuel rod, and it is executed before the time measure of control rods rapid scram test of the affected rods. This test has to be carried out to all the reactor control rods and takes valuable time during plant refuelling. So, by means of an automatic system to perform the test, we obtain an important time saving during refuelling. On the other hand, the on-line monitoring of the control rod insertion and changes in differential pressure, permits a control rod operation fast and safe validation. Moreover, an automatic individual report of every rod is generated by the system and a final global result report of the entire test developed in refuelling is generated. The mentioned reports can be attached directly to the procedure documents obtaining an office data processing important saving time.(author)

Results of automatic system implementation for the friction control rods execution in Cofrentes nuclear power plant

Energy Technology Data Exchange (ETDEWEB)

Palomo, M., E-mail: mpalomo@iqn.upv.es [Universidad Politecnica de Valencia (UPV) (Spain); Urrea, M., E-mail: matias.urrea@iberdrola.es [Iberdrola Generacion S.A. Valencia (Spain). C.N. Cofrentes; Curiel, M., E-mail: m.curiel@lainsa.com [Logistica y Acondicionamientos Industriales (LAINSA), Valencia (Spain); Arnaldos, A., E-mail: a.arnaldos@titaniast.com [TITANIA Servicios Teconologicos, Valencia (Spain)

2011-07-01

The purpose of this presentation is to show the obtained results in Cofrentes Nuclear Power Plant (Spain) of Control Rods PCC/24 Friction Test Procedure. In order to perform this, a Control Rod Friction Test System has been developed. Principally, this system consists on software and data acquisition hardware that obtains and analyzes the control rod pressure variation on which the test is being made. The PCC/24 Procedure objective is to detect an excessive friction in the control rod movement that could cause a CRD (Control Rod Drive) movement slower than usual. This test is necessary every time that an anomalous alteration is produced in the reactor core that could affect to a fuel rod, and it is executed before the time measure of control rods rapid scram test of the affected rods. This test has to be carried out to all the reactor control rods and takes valuable time during plant refuelling. So, by means of an automatic system to perform the test, we obtain an important time saving during refuelling. On the other hand, the on-line monitoring of the control rod insertion and changes in differential pressure, permits a control rod operation fast and safe validation. Moreover, an automatic individual report of every rod is generated by the system and a final global result report of the entire test developed in refuelling is generated. The mentioned reports can be attached directly to the procedure documents obtaining an office data processing important saving time.(author)

Effect of humidity and interlayer cation on frictional strength of montmorillonite

Science.gov (United States)

Tetsuka, H.; Katayama, I.; Sakuma, H.; Tamura, K.

2016-12-01

Smectite has been ubiquitously seen in fault gouge (Schleicher et al., 2006; Kuo et al., 2009; Si et al., 2014; Kameda, 2015) and is characteristic by low frictional coefficient (Saffer et al., 2001; Ikari et al., 2007); consequently, it has a key role in fault dynamics. The frictional strength of montmorillonite (a typical type of smectite) is affected by mainly two factors, 1) hydration state and 2) interlayer cation. Previous laboratory experiments have shown that the frictional strength of montmorillonite changes with hydration state (Ikari et al., 2007) and with interlayer cation (Behnsen and Faulkner, 2013). However, experimental study for frictional strengths of interlayer cation-exchanged montmorillonite under controlled hydration state has not been reported. We are developing humidity control system in biaxial friction testing machine and try to investigate the effect of relative humidity and interlayer cation on frictional strength of montmorillonite. The humidity control system consists of two units, 1) the pressure vessel (core holder) unit controlled by a constant temperature and 2) the vapor generating unit controlled by variable temperature. We control relative humidity around sample, which is calculated from the temperature around sample and the vapor pressure at vapor generating unit. Preliminary experiments under controlled humidity show frictional coefficient of montmorillonite decrease with increasing relative humidity. In the meeting, we will report the systematic study of frictional coefficient as function of relative humidity and interlayer cation species.

Real-world damping of a physical pendulum

International Nuclear Information System (INIS)

Bacon, M E; Do Dai Nguyen

2005-01-01

Damped periodic motion is ubiquitous in the physical world and is a subject of study at all levels of undergraduate education. In this paper we investigate the damping of a metre stick acting as a physical pendulum subject to air drag. We do not limit our investigation to small angles and find that the air drag is well described by a retarding torque equal to a term proportional to the angular velocity together with a term proportional to the square on the angular velocity. The study is made possible by the use of a video camera, video capture and analysis software and an easy-to-use intuitive, icon-based, simulation program to numerically solve the equation of motion. Suggestions are made for further study

The Actuator Fault Diagnosis Based on the Valve Friction

Directory of Open Access Journals (Sweden)

Jiajiang Li

2014-08-01

Full Text Available Control valve (actuator is the frequently moving terminal Instrument of the control system. To avoid the leaking of the actuator, there is packing at the moving parts. However, the friction caused by the packing can do harm to the control of the system. The washing effect of the media, high temperature, high pressure, frequent movement and other effects can result in the leaking of the packing and the deformation of the valve stem, which causes the change of the friction. The study of the control of the friction has always been an interesting topic in the industry. In this paper, we theoretically analyze the relationship of the friction of the packing and the static performance of the control valve, and offer a method to check the quality of the moving parts by attaching a strain gage (strain rosette to the empty part of the valve stem. This method has been demonstrated via experiment and a method to do error detection is provided at last.

Effect of Process Parameters on Friction Model in Computer Simulation of Linear Friction Welding

Directory of Open Access Journals (Sweden)

A. Yamileva

2014-07-01

Full Text Available The friction model is important part of a numerical model of linear friction welding. Its selection determines the accuracy of the results. Existing models employ the classical law of Amonton-Coulomb where the friction coefficient is either constant or linearly dependent on a single parameter. Determination of the coefficient of friction is a time consuming process that requires a lot of experiments. So the feasibility of determinating the complex dependence should be assessing by analysis of effect of approximating law for friction model on simulation results.

Modeling of Instabilities and Self-organization at the Frictional Interface

Science.gov (United States)

Mortazavi, Vahid

The field of friction-induced self-organization and its practical importance remains unknown territory to many tribologists. Friction is usually thought of as irreversible dissipation of energy and deterioration; however, under certain conditions, friction can lead to the formation of new structures at the interface, including in-situ tribofilms and various patterns at the interface. This thesis studies self-organization and instabilities at the frictional interface, including the instability due to the temperature-dependency of the coefficient of friction, the transient process of frictional running-in, frictional Turing systems, the stick-and-slip phenomenon, and, finally, contact angle (CA) hysteresis as an example of solid-liquid friction and dissipation. All these problems are chosen to bridge the gap between fundamental interest in understanding the conditions leading to self-organization and practical motivation. We study the relationship between friction-induced instabilities and friction-induced self-organization. Friction is usually thought of as a stabilizing factor; however, sometimes it leads to the instability of sliding, in particular when friction is coupled with another process. Instabilities constitute the main mechanism for pattern formation. At first, a stationary structure loses its stability; after that, vibrations with increasing amplitude occur, leading to a limit cycle corresponding to a periodic pattern. The self-organization is usually beneficial for friction and wear reduction because the tribological systems tend to enter a state with the lowest energy dissipation. The introductory chapter starts with basic definitions related to self-organization, instabilities and friction, literature review, and objectives. We discuss fundamental concepts that provide a methodological tool to investigate, understand and enhance beneficial processes in tribosystems which might lead to self-organization. These processes could result in the ability of a

Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction

International Nuclear Information System (INIS)

Li Zhi-Xin; Cao Qing-Jie; Alain, Léger

2016-01-01

We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous (SD) oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography. (paper)

Non-linear friction in reciprocating hydraulic rod seals: Simulation and measurement

International Nuclear Information System (INIS)

Bullock, A K; Tilley, D G; Johnston, D N; Bowen, C R; Keogh, P S

2009-01-01

Non-linear seal friction can impede the performance of hydraulic actuation systems designed for high precision positioning with favourable dynamic response. Methods for predicting seal friction are required to help develop sealing systems for this type of application. Recent simulation techniques have claimed progress, although have yet to be validated experimentally. A conventional reciprocating rod seal is analysed using established elastohydrodynamic theory and the mixed lubrication Greenwood-Williamson-average Reynolds model. A test rig was used to assess the accuracy of the simulation results for both instroke and outstroke. Inverse hydrodynamic theory is shown to predict a U 0.5 power law between rod speed and friction. Comparison with experimental data shows the theory to be qualitatively inaccurate and to predict friction levels an order of magnitude lower than those measured. It was not possible to model the regions very close to the inlet and outlet due to the high pressure gradients at the edges of the contact. The mixed lubrication model produces friction levels within the correct order of magnitude, although incorrectly predicts higher friction during instroke than outstroke. Previous experiments have reported higher friction during instroke than outstroke for rectangular seals, suggesting that the mixed lubrication model used could possibly be suitable for symmetric seals, although not for seal tribology in general.

Micromechanical study of macroscopic friction and dissipation in idealised granular materials: the effect of interparticle friction

NARCIS (Netherlands)

Kruyt, Nicolaas P.; Gutkowski, Witold; Rothenburg, L.; Kowalewski, Tomasz A.

2004-01-01

Using Discrete Element Method (DEM) simulations with varying interparticle friction coefficient, the relation between interparticle friction coefficient and macroscopic continuum friction and dissipation is investigated. As expected, macroscopic friction and dilatancy increase with interparticle

Friction welded closures of waste canisters

International Nuclear Information System (INIS)

Klein, R.F.

1987-01-01

Liquid radioactive waste presently stored in underground tanks is to undergo a vitrifying process which will immobilize it into a solid form. This solid waste will be contained in a stainless steel canister. The canister opening requires a positive-seal weld, the properties and thickness of which must be at least equal to those of the canister material. All studies and tests performed in the work discussed in this paper have the inertia friction welding concept to be highly feasible in this application. This paper describes the decision to investigate the inertia friction welding process, the inertia friction welding process itself, and a proposed equipment design concept. This system would provide a positive, reliable, inspectable, and full-thickness seal weld while utilizing easily maintainable equipment. This high-quality weld can be achieved even in highly contaminated hot cell

Science 101: What Causes Friction?

Science.gov (United States)

Robertson, Bill

2014-01-01

Defining friction and asking what causes it might seem like a trivial question. Friction seems simple enough to understand. Friction is a force between surfaces that pushes against things that are moving or tending to move, and the rougher the surfaces, the greater the friction. Bill Robertson answers this by saying, "Well, not exactly".…

O efeito de Coriolis: de pêndulos a moléculas The Coriolis effect: from pendulums to molecules

Directory of Open Access Journals (Sweden)

Emílio Borges

2010-01-01

Full Text Available Coriolis force is an effect which arises in rotating reference frames such as the Earth. This force influences large oceanic motions, atmospheric inertial circles, horizontal and vertical deviations in moving bodies. The Foucault's pendulum is another special case about the Coriolis force influence on macroscopic processes. This pendulum is an example of how experimental sciences can be essential for philosophical and social changes, since it was crucial to prove the Earth's rotation. The Coriolis force has an important role also at microscopic level; it couples vibrational and rotational molecular motions and this fact has consequences in spectroscopic and energetic molecular processes. These points are discussed in this paper.

Instrumentation of a Charpy-pendulum. Additional data obtained from it and its application to nuclear reactor pressure vessels surveillance programs

International Nuclear Information System (INIS)

Chomik, Enrique P.; Dhers, Horacio; Iorio, Antonio F.; Ciriani, Dario F.

1999-01-01

Charpy test gives information about a material dynamic fracture behavior. In a plain Charpy test, this information is the absorbed energy during fracture of the specimen, lateral deformation and the percentage of ductile fracture of the specimen. These parameters can then be used for the determination of the material response to a dynamic applied load, and are used at present to determine the brittle-ductile transition temperature of a material. However, there is a lot of additional information that can be obtained from a Charpy test, which is vital for the case of surveillance programs of nuclear power plants, where it is necessary to get the most available information from the specimens to be tested, because each one of them was irradiated for many years under temperature and neutronic flux conditions similar to that of the internal surface of the reactor pressure vessel, which converts these specimens in unique and very expensive ones. This additional information can be obtained from the curve that determines the evolution of the applied force to the specimen throughout the time involved in its fracture. It was possible to instrument a Charpy pendulum at a fraction of the cost necessary to buy an instrumentation package like the ones available in the market, and since the instrumentation equipment obtained is easy to transport. It has the additional advantage that can be used to instrument any other pendulum replacing only the hammer of the pendulum with a instrumented one for that pendulum. (author)

Novel Friction Law for the Static Friction Force based on Local Precursor Slipping

OpenAIRE

Katano, Yu; Nakano, Ken; Otsuki, Michio; Matsukawa, Hiroshi

2014-01-01

The sliding of a solid object on a solid substrate requires a shear force that is larger than the maximum static friction force. It is commonly believed that the maximum static friction force is proportional to the loading force and does not depend on the apparent contact area. The ratio of the maximum static friction force to the loading force is called the static friction coefficient µ M, which is considered to be a constant. Here, we conduct experiments demonstrating that the static fricti...

On the "pendulum" of bioethics.

Science.gov (United States)

Petrini, C

According to a well-known philosopher, the life of ethics was saved, at the beginning of the 1970s, by medicine. The claim is based on the consideration that the questions then being posed by medicine were actual and dramatic, forcing ethicists and philosophers to abandon their mostly useless abstract speculations. Since the early years of the new century some authors have been harsh in their criticism of bioethics, accusing it not only of not "returning the favour" to medicine but also of seriously hindering medical practice and, above all, research, by subjecting them to unnecessary constraints. Some of the more restrictive and bureaucratic regulations have been relaxed over the years, to the extent that some authors suggest that the bioethics pendulum "is taking a swing to the permissive". There are nonetheless some fundamental principles and values that do not admit of concessions. Provided these are properly guaranteed, it is appropriate to simplify overly rigid regulations (such as those concerning consent to the use of health data) and allow research to achieve potentially useful results.

High precision tracking control of a servo gantry with dynamic friction compensation.

Science.gov (United States)

Zhang, Yangming; Yan, Peng; Zhang, Zhen

2016-05-01

This paper is concerned with the tracking control problem of a voice coil motor (VCM) actuated servo gantry system. By utilizing an adaptive control technique combined with a sliding mode approach, an adaptive sliding mode control (ASMC) law with friction compensation scheme is proposed in presence of both frictions and external disturbances. Based on the LuGre dynamic friction model, a dual-observer structure is used to estimate the unmeasurable friction state, and an adaptive control law is synthesized to effectively handle the unknown friction model parameters as well as the bound of the disturbances. Moreover, the proposed control law is also implemented on a VCM servo gantry system for motion tracking. Simulations and experimental results demonstrate good tracking performance, which outperform traditional control approaches. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Modeling of Compressible Flow with Friction and Heat Transfer Using the Generalized Fluid System Simulation Program (GFSSP)

Science.gov (United States)

Bandyopadhyay, Alak; Majumdar, Alok

2007-01-01

The present paper describes the verification and validation of a quasi one-dimensional pressure based finite volume algorithm, implemented in Generalized Fluid System Simulation Program (GFSSP), for predicting compressible flow with friction, heat transfer and area change. The numerical predictions were compared with two classical solutions of compressible flow, i.e. Fanno and Rayleigh flow. Fanno flow provides an analytical solution of compressible flow in a long slender pipe where incoming subsonic flow can be choked due to friction. On the other hand, Raleigh flow provides analytical solution of frictionless compressible flow with heat transfer where incoming subsonic flow can be choked at the outlet boundary with heat addition to the control volume. Nonuniform grid distribution improves the accuracy of numerical prediction. A benchmark numerical solution of compressible flow in a converging-diverging nozzle with friction and heat transfer has been developed to verify GFSSP's numerical predictions. The numerical predictions compare favorably in all cases.

Experimental studies to the dose distribution from pendulum irradiation of the middle part of the ESOPHAGUS with electrons and X-rays from a 42 MeV betatron

International Nuclear Information System (INIS)

Bark, R.

1973-01-01

Experimental studies of the dose distributions in the area of the middle esophagus resulting from pendulum irradiation with electrons and X-rays are reported. In these studies the energy and the arrangement of the pendulum angle were to be varied so as to generate the maximum possible dose decrease from the focal area to the healthy tissue. The electron energies used were 30 and 42 MeV, the energies of ultrahard X-rays were 42 MV. All studies carried out with the different pendulum angles indicated that electron therapy is in no way capable of meeting the existing requirements in terms of low exposures of the lung, bone marrow and skin. However, the use of ultrahard X-rays offers much better dose distribution conditions. These can be achieved only by bi-segmental pendulum irradiation under a bilateral angle of 70 0 (30 0 dorsal, 40 0 ventral). (orig./RF) [de

A simple pendulum borehole tiltmeter based on a triaxial optical-fibre displacement sensor

Science.gov (United States)

Chawah, P.; Chéry, J.; Boudin, F.; Cattoen, M.; Seat, H. C.; Plantier, G.; Lizion, F.; Sourice, A.; Bernard, P.; Brunet, C.; Boyer, D.; Gaffet, S.

2015-11-01

Sensitive instruments like strainmeters and tiltmeters are necessary for measuring slowly varying low amplitude Earth deformations. Nonetheless, laser and fibre interferometers are particularly suitable for interrogating such instruments due to their extreme precision and accuracy. In this paper, a practical design of a simple pendulum borehole tiltmeter based on laser fibre interferometric displacement sensors is presented. A prototype instrument has been constructed using welded borosilicate with a pendulum length of 0.85 m resulting in a main resonance frequency of 0.6 Hz. By implementing three coplanar extrinsic fibre Fabry-Perot interferometric probes and appropriate signal filtering, our instrument provides tilt measurements that are insensitive to parasitic deformations caused by temperature and pressure variations. This prototype has been installed in an underground facility (Rustrel, France) where results show accurate measurements of Earth strains derived from Earth and ocean tides, local hydrologic effects, as well as local and remote earthquakes. The large dynamic range and the high sensitivity of this tiltmeter render it an invaluable tool for numerous geophysical applications such as transient fault motion, volcanic strain and reservoir monitoring.

Kalker's algorithm Fastsim solves tangential contact problems with slip-dependent friction and friction anisotropy

Science.gov (United States)

Piotrowski, J.

2010-07-01

This paper presents two extensions of Kalker's algorithm Fastsim of the simplified theory of rolling contact. The first extension is for solving tangential contact problems with the coefficient of friction depending on slip velocity. Two friction laws have been considered: with and without recuperation of the static friction. According to the tribological hypothesis for metallic bodies shear failure, the friction law without recuperation of static friction is more suitable for wheel and rail than the other one. Sample results present local quantities inside the contact area (division to slip and adhesion, traction) as well as global ones (creep forces as functions of creepages and rolling velocity). For the coefficient of friction diminishing with slip, the creep forces decay after reaching the maximum and they depend on the rolling velocity. The second extension is for solving tangential contact problems with friction anisotropy characterised by a convex set of the permissible tangential tractions. The effect of the anisotropy has been shown on examples of rolling without spin and in the presence of pure spin for the elliptical set. The friction anisotropy influences tangential tractions and creep forces. Sample results present local and global quantities. Both extensions have been described with the same language of formulation and they may be merged into one, joint algorithm.

Visual interface for the automation of the instrumented pendulum of Charpy tests used in the surveillance program of reactors vessel of nuclear power plants; Interfase visual para la automatizacion del pendulo instrumentado de pruebas Charpy utilizado en el programa de vigilancia de la vasija de reactores de centrales nucleares

Energy Technology Data Exchange (ETDEWEB)

Rojas S, A.S.; Sainz M, E.; Ruiz E, J.A. [ININ, Carretera Mexico-Toluca Km.36.5, Mpio. de Ocoyoacac, Estado de Mexico (Mexico)]. E-mail: asrs@nuclear.inin.mx; esm@nuclear.inin.mx; jare@nuclear.inin.mx

2004-07-01

Inside the Programs of Surveillance of the nuclear power stations periodic information is required on the state that keep the materials with those that builds the vessel of the reactor. This information is obtained through some samples or test tubes that are introduced inside the core of the reactor and it is observed if its physical characteristics remain after having been subjected to the radiation changes and temperature. The rehearsal with the instrumented Charpy pendulum offers information on the behavior of fracture dynamics of a material. In the National Institute of Nuclear Research (ININ) it has an instrumented Charpy pendulum. The operation of this instrument is manual, having inconveniences to carry out rehearsals with radioactive material, handling of high and low temperatures, to fulfill the normative ones for the realization of the rehearsals, etc. In this work the development of a computational program is presented (virtual instrument), for the automation of the instrumented pendulum. The system has modules like: Card of data acquisition, signal processing, positioning system, tempered system, pneumatic system, compute programs like it is the visual interface for the operation of the instrumented Charpy pendulum and the acquisition of impact signals. This system shows that given the characteristics of the nuclear industry with radioactive environments, the virtual instrumentation and the automation of processes can contribute to diminish the risks to the personnel occupationally exposed. (Author)

Approximations for Large Deflection of a Cantilever Beam under a Terminal Follower Force and Nonlinear Pendulum

Directory of Open Access Journals (Sweden)

H. Vázquez-Leal

2013-01-01

Full Text Available In theoretical mechanics field, solution methods for nonlinear differential equations are very important because many problems are modelled using such equations. In particular, large deflection of a cantilever beam under a terminal follower force and nonlinear pendulum problem can be described by the same nonlinear differential equation. Therefore, in this work, we propose some approximate solutions for both problems using nonlinearities distribution homotopy perturbation method, homotopy perturbation method, and combinations with Laplace-Padé posttreatment. We will show the high accuracy of the proposed cantilever solutions, which are in good agreement with other reported solutions. Finally, for the pendulum case, the proposed approximation was useful to predict, accurately, the period for an angle up to 179.99999999∘ yielding a relative error of 0.01222747.

A GENERALIZED COEFFICIENT OF FRICTION FOR ASSESSING ENERGY EFFICIENCY OF BEARING SYSTEMS

OpenAIRE

Al-Bender, Farid

2011-01-01

Environmental impact estimations, often carried out in the framework of Life Cycle Assessment (LCA) on production machines and machine tools, show that a significant (if not the greatest) part of the environmental impact is related to the use-phase of the machine. A closer analysis reveals that the energy efficiency of the bearing systems, i.e. their friction loss, is the main culprit in this. Cost reduction and maintenance savings were the main motivations that initiated tribology as a s...

Effect of Friction Model and Tire Maneuvering on Tire-Pavement Contact Stress

OpenAIRE

Haichao Zhou; Guolin Wang; Yangmin Ding; Jian Yang; Chen Liang; Jing Fu

2015-01-01

This paper aims to simulate the effects of different friction models on tire braking. A truck radial tire (295/80R22.5) was modeled and the model was validated with tire deflection. An exponential decay friction model that considers the effect of sliding velocity on friction coefficients was adopted for analyzing braking performance. The result shows that the exponential decay friction model used for evaluating braking ability meets design requirements of antilock braking system (ABS). The ti...

Friction modelling in sheet metal forming simulations: application and validation on an U-Bend product

NARCIS (Netherlands)

Sigvant, Mats; Hol, Johan; Chezan, Toni; van den Boogaard, Ton; Hora, P.

2015-01-01

The accuracy of sheet metal forming simulations strongly depends on, amongst others, friction modelling. The industrial standard is to use the Coulomb friction model with a constant coefficient of friction. However, it is known that the true friction conditions are dependent on the tribology system,

Measurement of friction force between two mica surfaces with multiple beam interferometry

Directory of Open Access Journals (Sweden)

Jung J.C.

2010-06-01

Full Text Available Friction forces play a crucial role in the tribological behaviour of microcomponents and the application of MEMS products. It is necessary to develop a measurement system to understand and control the material characteristics. In this study, a microscopic measurement system based on multiple beam interferometry is developed to measure the friction force between two mica thin films. Some frictional behaviour between the two mica sheets in contact are reported. The evaluated shear strength of mica agrees well to the existing data. It is possible to use the developed system for micro-tribology study.

Rubber friction: role of the flash temperature

International Nuclear Information System (INIS)

Persson, B N J

2006-01-01

When a rubber block is sliding on a hard rough substrate, the substrate asperities will exert time-dependent deformations of the rubber surface resulting in viscoelastic energy dissipation in the rubber, which gives a contribution to the sliding friction. Most surfaces of solids have roughness on many different length scales, and when calculating the friction force it is necessary to include the viscoelastic deformations on all length scales. The energy dissipation will result in local heating of the rubber. Since the viscoelastic properties of rubber-like materials are extremely strongly temperature dependent, it is necessary to include the local temperature increase in the analysis. At very low sliding velocity the temperature increase is negligible because of heat diffusion, but already for velocities of order 10 -2 m s -1 the local heating may be very important. Here I study the influence of the local heating on the rubber friction, and I show that in a typical case the temperature increase results in a decrease in rubber friction with increasing sliding velocity for v>0.01 m s -1 . This may result in stick-slip instabilities, and is of crucial importance in many practical applications, e.g. for tyre-road friction and in particular for ABS braking systems

Corrosion effects on friction factors

International Nuclear Information System (INIS)

Magleby, H.L.; Shaffer, S.J.

1996-01-01

This paper presents the results of NRC-sponsored material specimen tests that were performed to determine if corrosion increases the friction factors of sliding surfaces of motor-operated gate valves, which could require higher forces to close and open safety-related valves when subjected to their design basis differential pressures. Friction tests were performed with uncorroded specimens and specimens subjected to accelerated corrosion. Preliminary tests at ambient conditions showed that corrosion increased the friction factors, indicating the need for additional tests duplicating valve operating parameters at hot conditions. The additional tests showed friction factors of corroded specimens were 0.1 to 0.2 higher than for uncorroded specimens, and that the friction factors of the corroded specimens were not very dependent on contact stress or corrosion film thickness. The measured values of friction factors for the three corrosion films tested (simulating three operating times) were in the range of 0.3 to 0.4. The friction factor for even the shortest simulated operating time was essentially the same as the others, indicating that the friction factors appear to reach a plateau and that the plateau is reached quickly

A wear-resistant zirconia ceramic for low friction application

International Nuclear Information System (INIS)

Winnubst, A.J.A.; Ran, S.; Wiratha, K.W.; Blank, D.H.A.; Pasaribu, H.R.; Sloetjes, J.W.; Schipper, D.J.

2004-01-01

A high wear-resistant ceramic/ceramic couple is described associated with low friction. By adding a small amount CuO to yttria-doped tetragonal zirconia (Y-TZP) the (dry) coefficient of friction against alumina is only 0.2 during a sliding distance of 3-5 km after which the coefficient drastically increases and a transition from mild to sever wear occurs. Pure Y-TZP exhibits a coefficient of friction of 0.7 under the same experimental conditions but wear remains mild during the test (upto 10 km of sliding distance). These small amounts of CuO also strongly influence the densification behaviour. Sintering of this system occurs in several steps where among other things dissolution of CuO in the Y-TZP matrix as well as liquid phase sintering takes place. Non-uniform shrinkage of the CuO-doped system resulting in relative large microcracks in the ceramic can explain its sudden drastic increase in coefficient of friction and wear rate after 3-5 km of operation. (orig.)

Gimballed Shoulders for Friction Stir Welding

Science.gov (United States)

Carter, Robert; Lawless, Kirby

2008-01-01

In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding. Some definitions of terms, recapitulated from related prior NASA Tech Briefs articles, are prerequisite to a meaningful description of the proposed improvement. In friction stir welding, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a pin that rotates with the shoulder and protrudes from the shoulder into the depth of the workpiece. In conventional friction stir welding, the main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional friction stir welding is augmented with an auto-adjustable pin-tool (APT) capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or forcecontrol system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding as practiced heretofore, there are two shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. Both shoulders rotate with the pin and remain aligned coaxially with the pin. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft into the friction-stir-welding machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. This concludes the prerequisite definitions of terms.

Measurement and Calculation of Frictional Loss in Large Two-Stroke Engines

DEFF Research Database (Denmark)

Vølund, Anders

2003-01-01

The total frictional loss in a large two-stroke marine diesel engine is rather well determined. However, the contribution (size and distribution) from the different machine elements are not well known. The aim of this study is to establish methods to measure and calculate friction in the piston...... assembly and guide shoe system for a large two-stroke marine diesel engine. These components are the two major contributors to the total friction in a two-stroke marine diesel engine. The piston pack represents approximately 60% of the total mechanical loss at full load and the guide shoe system 23...

Origins of Rolling Friction

Science.gov (United States)

Cross, Rod

2017-01-01

When a hard object rolls on a soft surface, or vice versa, rolling friction arises from deformation of the soft object or the soft surface. The friction force can be described in terms of an offset in the normal reaction force or in terms of energy loss arising from the deformation. The origin of the friction force itself is not entirely clear. It…

Characterization of friction and wear behavior of friction modifiers used in wheel-rail contacts

NARCIS (Netherlands)

Oomen, M. A.; Bosman, R.; Lugt, P. M.

2017-01-01

Reliable traction between wheel and rail is an important issue in the railway industry. To reduce variations in the coefficient of friction, so-called “friction modifiers” (carrier with particles) are used. Twin-disk tests were done with three commercial friction modifiers, based on different

Synchronization dynamics of two different dynamical systems

International Nuclear Information System (INIS)

Luo, Albert C.J.; Min Fuhong

2011-01-01

Highlights: → Synchronization dynamics of two distinct dynamical systems. → Synchronization, de-synchronization and instantaneous synchronization. → A controlled pendulum synchronizing with the Duffing oscillator. → Synchronization invariant set. → Synchronization parameter map. - Abstract: In this paper, synchronization dynamics of two different dynamical systems is investigated through the theory of discontinuous dynamical systems. The necessary and sufficient conditions for the synchronization, de-synchronization and instantaneous synchronization (penetration or grazing) are presented. Using such a synchronization theory, the synchronization of a controlled pendulum with the Duffing oscillator is systematically discussed as a sampled problem, and the corresponding analytical conditions for the synchronization are presented. The synchronization parameter study is carried out for a better understanding of synchronization characteristics of the controlled pendulum and the Duffing oscillator. Finally, the partial and full synchronizations of the controlled pendulum with periodic and chaotic motions are presented to illustrate the analytical conditions. The synchronization of the Duffing oscillator and pendulum are investigated in order to show the usefulness and efficiency of the methodology in this paper. The synchronization invariant domain is obtained. The technique presented in this paper should have a wide spectrum of applications in engineering. For example, this technique can be applied to the maneuvering target tracking, and the others.

Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

Science.gov (United States)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process used in the fabrication of cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

Actuation crosstalk in free-falling systems: Torsion pendulum results for the engineering model of the LISA pathfinder gravitational reference sensor

Science.gov (United States)

Bassan, M.; Cavalleri, A.; De Laurentis, M.; De Marchi, F.; De Rosa, R.; Di Fiore, L.; Dolesi, R.; Finetti, N.; Garufi, F.; Grado, A.; Hueller, M.; Marconi, L.; Milano, L.; Minenkov, Y.; Pucacco, G.; Stanga, R.; Vetrugno, D.; Visco, M.; Vitale, S.; Weber, W. J.

2018-01-01

In this paper we report on measurements on actuation crosstalk, relevant to the gravitational reference sensors for LISA Pathfinder and LISA. In these sensors, a Test Mass (TM) falls freely within a system of electrodes used for readout and control. These measurements were carried out on ground with a double torsion pendulum that allowed us to estimate both the torque injected into the sensor when a control force is applied and, conversely, the force leaking into the translational degree of freedom due to the applied torque.The values measured on our apparatus (the engineering model of the LISA Pathfinder sensor) agree to within 0.2% (over a maximum measured crosstalk of 1%) with predictions of a mathematical model when measuring force to torque crosstalk, while it is somewhat larger than expected (up to 3.5%) when measuring torque to force crosstalk. However, the values in the relevant range, i.e. when the TM is well centered ( ± 10 μm) in the sensor, remain smaller than 0.2%, satisfying the LISA Pathfinder requirements.

Experimental research on friction factor of end faces of contacting mechanical seals

Science.gov (United States)

Wei, Long; Gu, Bo-qin; Feng, Xiu; Sun, Jian-jun

2008-11-01

The friction of the seal faces is the most important phenomenon in working process of contacting mechanical seals. The friction factor f is a key parameter for expressing the friction regime of the seal faces, the frictional power, the wearing capacity, the friction heat productivity, the temperature distortion of the end face and the temperature of the end face. The relationship between the friction factor f and the friction regime of the end faces of contacting mechanical seals was discussed from a microscopic point of view. The friction factor is usually worked out by the friction torque which is measured in the test. In the computer aided testing device of the mechanical seal system, the experimental investigations on the basic performance of the B104a-70 contacting mechanical seal was carried out. The test results indicate that the bigger the spring pressure of B104a-70 contacting mechanical seal, the bigger the friction factor. When the spring pressure is less, the bigger the rotational speed, the bigger the friction factor. But when the spring pressure is equal to 0.0866 MPa, the friction factor is not almost influenced by the rotational speed. When the rotational speed and spring pressure are less, the medium pressure has a less influence on the friction factor. When the rotational speed or spring pressure is bigger, the bigger the medium pressure, the less the friction factor.

Control strategies for friction dampers: numerical assessment and experimental investigations.

OpenAIRE

Coelho H.T.; Santos M.B.; Lepore Neto F.P.; Mahfoud J.

2014-01-01

The use of friction dampers has been proposed in a wide variety of mechanical systems for which it is not possible to apply viscoelastic materials, fluid based dampers or others viscous dampers. An important example is the application of friction dampers in aircraft engines to reduce the blades vibration amplitudes. In most cases, friction dampers have been studied in a passive way, however, a significant improvement can be achieved by controlling the normal force in the dampers. The aim of t...

The molecular dynamic simulation on impact and friction characters of nanofluids with many nanoparticles system

Directory of Open Access Journals (Sweden)

Bai Minli

2011-01-01

Full Text Available Abstract Impact and friction model of nanofluid for molecular dynamics simulation was built which consists of two Cu plates and Cu-Ar nanofluid. The Cu-Ar nanofluid model consisted of eight spherical copper nanoparticles with each particle diameter of 4 nm and argon atoms as base liquid. The Lennard-Jones potential function was adopted to deal with the interactions between atoms. Thus motion states and interaction of nanoparticles at different time through impact and friction process could be obtained and friction mechanism of nanofluids could be analyzed. In the friction process, nanoparticles showed motions of rotation and translation, but effected by the interactions of nanoparticles, the rotation of nanoparticles was trapped during the compression process. In this process, agglomeration of nanoparticles was very apparent, with the pressure increasing, the phenomenon became more prominent. The reunited nanoparticles would provide supporting efforts for the whole channel, and in the meantime reduced the contact between two friction surfaces, therefore, strengthened lubrication and decreased friction. In the condition of overlarge positive pressure, the nanoparticles would be crashed and formed particles on atomic level and strayed in base liquid.

Semi-active friction damper for buildings subject to seismic excitation

Science.gov (United States)

Mantilla, Juan S.; Solarte, Alexander; Gomez, Daniel; Marulanda, Johannio; Thomson, Peter

2016-04-01

Structural control systems are considered an effective alternative for reducing vibrations in civil structures and are classified according to their energy supply requirement: passive, semi-active, active and hybrid. Commonly used structural control systems in buildings are passive friction dampers, which add energy dissipation through damping mechanisms induced by sliding friction between their surfaces. Semi-Active Variable Friction Dampers (SAVFD) allow the optimum efficiency range of friction dampers to be enhanced by controlling the clamping force in real time. This paper describes the development and performance evaluation of a low-cost SAVFD for the reduction of vibrations of structures subject to earthquakes. The SAVFD and a benchmark structural control test structure were experimentally characterized and analytical models were developed and updated based on the dynamic characterization. Decentralized control algorithms were implemented and tested on a shaking table. Relative displacements and accelerations of the structure controlled with the SAVFD were 80% less than those of the uncontrolled structure

Active Elastic Support/Dry Friction Damper with Piezoelectric Ceramic Actuator

Directory of Open Access Journals (Sweden)

Liao Mingfu

2014-01-01

Full Text Available The basic operation principle of elastic support/dry friction damper in rotor system was introduced and the unbalance response of the rotor with elastic support/dry friction damper was analyzed theoretically. Based on the previous structure using an electromagnet as actuator, an active elastic support/dry friction damper using piezoelectric ceramic actuator was designed and its effectiveness of reducing rotor vibration when rotor traverses its critical speed and blade-out event happened was experimentally verified. The experimental results show that the active elastic support/dry friction damper with piezoelectric ceramic actuator can significantly reduce vibration in rotor system; the vibration amplitude of the rotor in critical speed region decreased more than 2 times, and the active damper can protect the rotor when a blade-out event happened, so the rotor can traverse the critical speed and shut down smoothly. In addition, the structure is much simpler than the previous, the weight was reduced by half and the power consumption was only 5 W.

Seismic shear waves as Foucault pendulum

Science.gov (United States)

Snieder, Roel; Sens-Schönfelder, Christoph; Ruigrok, Elmer; Shiomi, Katsuhiko

2016-03-01

Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of ScS and ScS2 waves, we show that the Foucault-like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed SKS splitting.

Dynamics of braking vehicles: from Coulomb friction to anti-lock braking systems

International Nuclear Information System (INIS)

Tavares, J M

2009-01-01

The dynamics of braking of wheeled vehicles is studied using the Coulomb approximation for the friction between road and wheels. The dependence of the stopping distance on the mass of the vehicle, on the number of its wheels and on the intensity of the braking torque is established. It is shown that there are two regimes of braking, with and without sliding. The advantage of using an anti-lock braking system (ABS) is put in evidence, and a quantitative estimate of its efficiency is proposed and discussed

Asymptotic shape of solutions to the perturbed simple pendulum problems

Directory of Open Access Journals (Sweden)

Tetsutaro Shibata

2007-05-01

Full Text Available We consider the positive solution of the perturbed simple pendulum problem $$ u''(r + frac{N-1}{r}u'(r - g(u(t + lambda sin u(r = 0, $$ with $0 < r < R$, $ u'(0 = u(R = 0$. To understand well the shape of the solution $u_lambda$ when $lambda gg 1$, we establish the leading and second terms of $Vert u_lambdaVert_q$ ($1 le q < infty$ with the estimate of third term as $lambda o infty$. We also obtain the asymptotic formula for $u_lambda'(R$ as $lambda o infty$.

Trapping of a microsphere pendulum resonator in an optical potential

International Nuclear Information System (INIS)

Ward, J. M.; Wu, Y.; Nic Chormaic, S.; Minogin, V. G.

2009-01-01

We propose a method to spatially confine or corral the movements of a micropendulum via the optical forces produced by two simultaneously excited optical modes of a photonic molecule comprising two microspherical cavities. We discuss how the cavity-enhanced optical force generated in the photonic molecule can create an optomechanical potential of about 10 eV deep and 30 pm wide, which can be used to trap the pendulum at any given equilibrium position by a simple choice of laser frequencies. This result presents opportunities for very precise all-optical self-alignment of microsystems.

Tactile friction of topical formulations.

Science.gov (United States)

Skedung, L; Buraczewska-Norin, I; Dawood, N; Rutland, M W; Ringstad, L

2016-02-01

The tactile perception is essential for all types of topical formulations (cosmetic, pharmaceutical, medical device) and the possibility to predict the sensorial response by using instrumental methods instead of sensory testing would save time and cost at an early stage product development. Here, we report on an instrumental evaluation method using tactile friction measurements to estimate perceptual attributes of topical formulations. Friction was measured between an index finger and an artificial skin substrate after application of formulations using a force sensor. Both model formulations of liquid crystalline phase structures with significantly different tactile properties, as well as commercial pharmaceutical moisturizing creams being more tactile-similar, were investigated. Friction coefficients were calculated as the ratio of the friction force to the applied load. The structures of the model formulations and phase transitions as a result of water evaporation were identified using optical microscopy. The friction device could distinguish friction coefficients between the phase structures, as well as the commercial creams after spreading and absorption into the substrate. In addition, phase transitions resulting in alterations in the feel of the formulations could be detected. A correlation was established between skin hydration and friction coefficient, where hydrated skin gave rise to higher friction. Also a link between skin smoothening and finger friction was established for the commercial moisturizing creams, although further investigations are needed to analyse this and correlations with other sensorial attributes in more detail. The present investigation shows that tactile friction measurements have potential as an alternative or complement in the evaluation of perception of topical formulations. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Friction laws at the nanoscale.

Science.gov (United States)

Mo, Yifei; Turner, Kevin T; Szlufarska, Izabela

2009-02-26

Macroscopic laws of friction do not generally apply to nanoscale contacts. Although continuum mechanics models have been predicted to break down at the nanoscale, they continue to be applied for lack of a better theory. An understanding of how friction force depends on applied load and contact area at these scales is essential for the design of miniaturized devices with optimal mechanical performance. Here we use large-scale molecular dynamics simulations with realistic force fields to establish friction laws in dry nanoscale contacts. We show that friction force depends linearly on the number of atoms that chemically interact across the contact. By defining the contact area as being proportional to this number of interacting atoms, we show that the macroscopically observed linear relationship between friction force and contact area can be extended to the nanoscale. Our model predicts that as the adhesion between the contacting surfaces is reduced, a transition takes place from nonlinear to linear dependence of friction force on load. This transition is consistent with the results of several nanoscale friction experiments. We demonstrate that the breakdown of continuum mechanics can be understood as a result of the rough (multi-asperity) nature of the contact, and show that roughness theories of friction can be applied at the nanoscale.

Friction surfaced Stellite6 coatings

International Nuclear Information System (INIS)

Rao, K. Prasad; Damodaram, R.; Rafi, H. Khalid; Ram, G.D. Janaki; Reddy, G. Madhusudhan; Nagalakshmi, R.

2012-01-01

Solid state Stellite6 coatings were deposited on steel substrate by friction surfacing and compared with Stellite6 cast rod and coatings deposited by gas tungsten arc and plasma transferred arc welding processes. Friction surfaced coatings exhibited finer and uniformly distributed carbides and were characterized by the absence of solidification structure and compositional homogeneity compared to cast rod, gas tungsten arc and plasma transferred coatings. Friction surfaced coating showed relatively higher hardness. X-ray diffraction of samples showed only face centered cubic Co peaks while cold worked coating showed hexagonally close packed Co also. - Highlights: ► Stellite6 used as coating material for friction surfacing. ► Friction surfaced (FS) coatings compared with casting, GTA and PTA processes. ► Finer and uniformly distributed carbides in friction surfaced coatings. ► Absence of melting results compositional homogeneity in FS Stellite6 coatings.

Friction and wear of TPS fibers. Progress Report

International Nuclear Information System (INIS)

Bascom, W.D.; Wong, S.

1987-11-01

The sliding friction behavior of single filaments of SiO 2 , SiC, and an aluminoborosilicate has been determined. These fibers are used in thermal protection systems (TPS) and are subject to damage during weaving and aero-maneuvering. All fibers exhibited stick-slip friction indicating the successive formation and rupture of strong junctions between the contacting filaments. The static frictional resistance of the sized SiC filament was 4X greater than for the same filament after heat cleaning. This result suggests that the sizing is an organic polymer with a high shear yield strength. Heat cleaning exposes the SiC surface and/or leaves an inorganic residue so that the adhesional contact between filaments has a low fracture energy and frictional sliding occurs by brittle fracture. The frictional resistances of the sized and heat cleaned SiO 2 and glass filaments were all comparable to that of the heat cleaned SiC. It would appear that the sizings as well as the heat cleaned surfaces of the silica and glass have low fracture energies so that the sliding resistance is determined by brittle fracture

Design, optimization and numerical modelling of a novel floating pendulum wave energy converter with tide adaptation

Science.gov (United States)

Yang, Jing; Zhang, Da-hai; Chen, Ying; Liang, Hui; Tan, Ming; Li, Wei; Ma, Xian-dong

2017-10-01

A novel floating pendulum wave energy converter (WEC) with the ability of tide adaptation is designed and presented in this paper. Aiming to a high efficiency, the buoy's hydrodynamic shape is optimized by enumeration and comparison. Furthermore, in order to keep the buoy's well-designed leading edge always facing the incoming wave straightly, a novel transmission mechanism is then adopted, which is called the tidal adaptation mechanism in this paper. Time domain numerical models of a floating pendulum WEC with or without tide adaptation mechanism are built to compare their performance on various water levels. When comparing these two WECs in terms of their average output based on the linear passive control strategy, the output power of WEC with the tide adaptation mechanism is much steadier with the change of the water level and always larger than that without the tide adaptation mechanism.

Analysis of load reduction possibilities using a hydraulic soft yaw system for a 5-MW turbine and its sensitivity to yaw-bearing friction

DEFF Research Database (Denmark)

Stubkier, S.; Pedersen, H. C.; Jonkman, J. M.

2014-01-01

With the increasing size of wind turbines and with increasing lifetime demands, new methods for load reduction in the turbines need to be examined. One method is to make the yaw system of the turbine flexible, thereby dampening the loads to the system. This paper presents a hydraulic soft yaw...... concept and investigates the effect this has on critical loads in the turbine. To analyze the system, a novel friction model is developed and implemented for the yaw system using the NREL 5-MW turbine in the aerodynamic code FAST. Based on this model, the influence of friction is investigated...

Analytical and experimental investigation of the static friction regime for rubber-rigid ball contact

NARCIS (Netherlands)

Deladi, E.L.; de Rooij, Matthias B.; de Vries, Erik G.; de Vries, Erik G.; Schipper, Dirk J.

2006-01-01

The static friction regime is of great importance for systems requiring accurate positioning. The parameters of the static friction regime in terms of static friction force and limiting displacement before gross sliding are investigated for a rubber ball/metal flat configuration. Single-asperity

Designing a Tool System for Lowering Friction during the Ejection of In-Die Sintered Micro Gears

DEFF Research Database (Denmark)

Cannella, Emanuele; Nielsen, Emil Krabbe; Stolfi, Alessandro

2017-01-01

is affected by the influence of friction during the ejection phase, caused by radial expansion of the compacted and sintered powder. This paper presents the development of a pre-stressed tool system for the manufacture of micro gears made of aluminum. By using the hot isostatic pressing (HIP) sintering...

Intelligent Control System Taking Account of Cooperativeness Using Weighting Information on System Objective

Directory of Open Access Journals (Sweden)

Masaki Takahashi

2004-08-01

Full Text Available This study considers an intelligent control system to integrate flexibly its components by using weighted information where the system evaluation is reflected. Such system evaluates the information flowing through the components and converts them by weighting depending on the degree of importance. Integration of components based on the system evaluation enables a system consisting of them to realize various, flexible and adaptive control. In this study, the intelligent control method is applied to a swing up and stabilization control problem of a number of cart and pendulum systems on a restricted straight guide. To stabilize the pendulum in a restricted environment, each system should realize not only a swing-up and stabilization control of the pendulum, but also a position control of the cart to avoid collision or deadlock. The experiment using a real apparatus demonstrated that the controller learning light interaction acquires egoistic character, the controller learning heavy interaction behaves altruistically, and the controller equally considering self cart and another cart becomes cooperative. In other words, these autonomous decentralized controllers can acquire various characters and flexibility for cooperation.

Certification of a weld produced by friction stir welding

Science.gov (United States)

Obaditch, Chris; Grant, Glenn J

2013-10-01

Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

Tidal Friction in the Earth-Moon System and Laplace Planes: Darwin Redux

Science.gov (United States)