Статті в журналах з теми "Moment of frictional forces"
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1
Choi, D. H., and W. Hwang. "Measurement of Frictional Forces in Atomic Force Microscopy." Solid State Phenomena 121-123 (March 2007): 851–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.851.
Повний текст джерелаАнотація:
A new calibration method of frictional forces in atomic force microscopy (AFM) is suggested. An angle conversion factor is defined using the relationship between torsional angle and frictional signal. When the factor is measured, the slopes of the torsional angle and the frictional signal as a function of the normal force are used to eliminate the effect of the adhesive force. Moment balance equations on the flat surface and the top edge of a commercial step grating are used to obtain the angle conversion factor. After the factor is obtained from an AFM system, it can be applied to all cantilevers without additional experiments.
2
Salaani, Mohamed Kamel. "Analytical Tire Forces and Moments with Physical Parameters2." Tire Science and Technology 36, no. 1 (March 1, 2008): 3–42. http://dx.doi.org/10.2346/1.2804130.
Повний текст джерелаАнотація:
Abstract The pneumatic tire behaves as a highly nonlinear system. Its complexity has limited the development of a complete and reasonable theory governing its mechanics. Practical tire models used in vehicle dynamics simulation and tire-related research rely basically on curve-fitted experimental data and empirical adjustments of theoretical models. This paper introduces a validated analytical model based on the physical properties of the tire by formulating the shear contact phenomena with elliptical normal pressure distribution and planar stress-strain laws. Adjustments are introduced to current methods for estimating distributed stiffness, the use of friction, and the forces saturation phenomena. The analytical model is formulated and normalized to accept tire physical parameters that are easily estimated from force and moments measurements. These parameters are universal to all tires: lateral and longitudinal stiffnesses, aligning pneumatic trail, overturning effective moment arm, and frictional properties. The method of using fundamental mechanics for modeling contact patch forces and moments with tire physical parameters constitutes a significant advancement. The tire model is validated with experimental data.
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Liu, Zhao, Antoine Hinaut, Stefan Peeters, Sebastian Scherb, Ernst Meyer, Maria Clelia Righi, and Thilo Glatzel. "2D KBr/Graphene Heterostructures—Influence on Work Function and Friction." Nanomaterials 12, no. 6 (March 15, 2022): 968. http://dx.doi.org/10.3390/nano12060968.
Повний текст джерелаАнотація:
The intercalation of graphene is an effective approach to modify the electronic properties of two-dimensional heterostructures for attractive phenomena and applications. In this work, we characterize the growth and surface properties of ionic KBr layers altered by graphene using ultra-high vacuum atomic force microscopy at room temperature. We observed a strong rippling of the KBr islands on Ir(111), which is induced by a specific layer reconstruction but disappears when graphene is introduced in between. The latter causes a consistent change in both the work function and the frictional forces measured by Kelvin probe force microscopy and frictional force microscopy, respectively. Systematic density functional theory calculations of the different systems show that the change in work function is induced by the formation of a surface dipole moment while the friction force is dominated by adhesion forces.
4
Fazeli, Nima, Roman Kolbert, Russ Tedrake, and Alberto Rodriguez. "Parameter and contact force estimation of planar rigid-bodies undergoing frictional contact." International Journal of Robotics Research 36, no. 13-14 (April 1, 2017): 1437–54. http://dx.doi.org/10.1177/0278364917698749.
Повний текст джерелаАнотація:
This paper addresses the identification of the inertial parameters and the contact forces associated with objects making and breaking frictional contact with the environment. Our goal is to explore under what conditions, and to what degree, the observation of physical interaction, in the form of motions and/or applied external forces, is indicative of the underlying dynamics that governs it. In this study we consider the cases of passive interaction, where an object free-falls under gravity, and active interaction, where known external perturbations act on an object at contact. We assume that both object and environment are planar and rigid, and exploit the well-known complementarity formulation for contact resolution to establish a constrained optimization-based problem to estimate inertial parameters and contact forces. We also show that when contact modes are known, or guessed, the formulation provides a closed-form relationship between inertial parameters, contact forces, and observed motions, that turns into a least squares problem. Consistent with intuition, the analysis indicates that without the application of known external forces, the identifiable set of parameters remains coupled, i.e. the ratio of mass moment of inertia to mass and the ratio of contact forces to the mass. Interestingly the analysis also shows that known external forces can lead to decoupling and identifiability of mass, mass moment of inertia, and normal and tangential contact forces. We evaluate the proposed algorithms both in simulation and with real experiments for the cases of a free falling square, ellipse, and rimless wheel interacting with the ground, as well as a disk interacting with a manipulator.
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Bilaloglu, Seda, Ying Lu, Daniel Geller, John Ross Rizzo, Viswanath Aluru, Esther P. Gardner, and Preeti Raghavan. "Effect of blocking tactile information from the fingertips on adaptation and execution of grip forces to friction at the grasping surface." Journal of Neurophysiology 115, no. 3 (March 1, 2016): 1122–31. http://dx.doi.org/10.1152/jn.00639.2015.
Повний текст джерелаАнотація:
Adaptation of fingertip forces to friction at the grasping surface is necessary to prevent use of inadequate or excessive grip forces. In the current study we investigated the effect of blocking tactile information from the fingertips noninvasively on the adaptation and efficiency of grip forces to surface friction during precision grasp. Ten neurologically intact subjects grasped and lifted an instrumented grip device with 18 different frictional surfaces under three conditions: with bare hands or with a thin layer of plastic (Tegaderm) or an additional layer of foam affixed to the fingertips. The coefficient of friction at the finger-object interface of each surface was obtained for each subject with bare hands and Tegaderm by measuring the slip ratio (grip force/load force) at the moment of slip. We found that the foam layer reduced sensibility for two-point discrimination and pressure sensitivity at the fingertips, but Tegaderm did not. However, Tegaderm reduced static, but not dynamic, tactile discrimination. Adaptation of fingertip grip forces to surface friction measured by the rate of change of peak grip force, and grip force efficiency measured by the grip-load force ratio at lift, showed a proportional relationship with bare hands but were impaired with Tegaderm and foam. Activation of muscles engaged in precision grip also varied with the frictional surface with bare hands but not with Tegaderm and foam. The results suggest that sensitivity for static tactile discrimination is necessary for feedforward and feedback control of grip forces and for adaptive modulation of muscle activity during precision grasp.
6
Spector, A. A., and R. C. Batra. "Rolling/Sliding of a Vibrating Elastic Body on an Elastic Substrate." Journal of Tribology 118, no. 1 (January 1, 1996): 147–52. http://dx.doi.org/10.1115/1.2837070.
Повний текст джерелаАнотація:
The rolling/sliding in the presence of friction of a vibrating elastic body on an elastic substrate is studied. It is shown that the longitudinal components of the velocity of the center of mass of the body and of the resultant frictional force are not affected by the vibration process. However, the normal vibration of the body influences the slip velocities and the distribution of frictional forces. For the problem of a harmonically oscillating long cylinder rolling/sliding on the flat surface of an elastic substrate, the time histories of the width of the contact zone and the length of adhesion subzone are computed. It is shown that the local frictional forces and slip velocities oscillate, and that the set of admissible values of the external frictional forces and moments providing the rolling/sliding regime is smaller under conditions of normal vibrations than that when the cylinder does not vibrate.
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Cawley, Patrick W., Robert S. Heidt, Pierce E. Scranton, Gary M. Losse, and Mark E. Howard. "Physiologic Axial Load, Frictional Resistance, and the Football Shoe—Surface Interface." Foot & Ankle International 24, no. 7 (July 2003): 551–56. http://dx.doi.org/10.1177/107110070302400705.
Повний текст джерелаАнотація:
The purpose of this investigation was to report on the interaction between different types of athletic shoes and playing surfaces using physiologic loads of 40 and 220 lbs. This is a continuation of our previous report using a load of 25 lbs. Nine shoes by three manufacturers were characterized as turf, court, molded cleat, or traditional cleat and tested on both natural grass and synthetic turf. A specially designed pneumatic testing device was used in order to measure translational resistance and rotational torque of the shoe-surface interface. Measurements were acquired for 1) force-X describing translational loading, 2) moment-Y describing the torque generated by linear translation, and 3) moment-Z describing the moment generated by axial rotation, and data were analyzed using repeated measures analysis of variance and Tukey's post-hoc comparison. It was found that increased the axial loads from 40 to 220 lbs significantly increased the frictional resistance ( p < .05) between the shoe and the artificial turf surface in a nonlinear fashion. Turf shoes demonstrated the most frictional resistance of any group for this condition. Increases in the forces generated in linear translation from the axial load of 40 to 220 lbs produced the most significant increases of any resistance test on the turf surface. The cleated shoes (both traditional and molded) generated the highest frictional and torsional resistance on the grass surface when compared to the other categories of shoes. Grass generated higher peak moments than turf for the cleated shoes. These results demonstrate the considerable differences between laboratory and physiologic conditions and that the increase in frictional resistance is nonlinear with increasing loads.
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Bechtel, S. E., S. Vohra, K. I. Jacob, and C. D. Carlson. "The Stretching and Slipping of Belts and Fibers on Pulleys." Journal of Applied Mechanics 67, no. 1 (September 28, 1999): 197–206. http://dx.doi.org/10.1115/1.321164.
Повний текст джерелаАнотація:
We derive the equations of motion for an extensible belt on a pulley in which all effects of inertia, including (for the first time) acceleration due to stretching, are retained in the momentum balance. These equations are also valid for fibers and films on rollers undergoing cold draw. We apply our equations to the problem of torque transmission by a belt between two pulleys, and compare the resulting solution to solutions in which centrifugal acceleration is included but stretching acceleration is neglected (the common engineering practice), and the solution in which both centrifugal and stretching accelerations are neglected. We find that ignoring both centrifugal and stretching accelerations results in an overprediction of the maximum moment that can be transmitted, and, for a given transmitted moment, underprediction of the slip angles on the driving and driven pulleys and overprediction of belt strain rates and normal and frictional forces from the pulley on the belt in the slip zones. The common engineering practice of including the effects of centrifugal acceleration but neglecting stretching acceleration also results in errors, for example underpredicting the maximum moment that can be transmitted, overpredicting the slip angles, and underpredicting belt strain rates and normal and frictional forces on the driving pulley. The percentage error increases as the ratios of belt stiffness to centrifugal acceleration or initial belt tension decrease. [S0021-8936(00)01401-X]
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Hyeung-Sik, Choi. "Modeling of robot manipulators working under the sea and the design of a robust controller." Robotica 14, no. 2 (March 1996): 213–18. http://dx.doi.org/10.1017/s0263574700019123.
Повний текст джерелаАнотація:
SUMMARYThis paper presents a study of the dynamics of undersea robot manipulators in an unstructured sea water environment and a control scheme appropriate for manipulating them. Under the sea, the buoyancy and the added mass should be considered in modeling the dynamics of the robot manipulators. However, due to the complexity of the modeling of the added mass, the dynamics of the robot manipulators are treated as an unmodeled dynamics in this paper. In addition to the buoyancy and added mass/moment of inertia, disturbing forces due to drag, and current affecting the dynamics of the robot manipulators should be considered. In this paper, the forces due to the drag are defined as disturbance forces in addition to the frictional force of manipulator joints. In order to control the manipulator, a robust control scheme is devised to achieve trajectory tracking while regulating disturbance forces. A numerical example is shown.
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Kozak, F. V., S. I. Krystopa, L. I. Krystopa, and Y. M. Arsenych. "IMPROVING OF EFFICIENCY OF BAND-BLOCK BRAKE WORK BY REDUCING OF DYNAMIC AND THERMAL LOADINGS." PRECARPATHIAN BULLETIN OF THE SHEVCHENKO SCIENTIFIC SOCIETY Number, no. 2(46) (December 26, 2018): 218–25. http://dx.doi.org/10.31471/2304-7399-2018-2(46)-218-225.
Повний текст джерелаАнотація:
This article is devoted to theoretical and experimental research of loading of new multi-pair friction units of band-block brakes of drilling hoists of drill units in stand conditions.Mathematical dependencies are made to determine frictional forces, efforts of tensions of incident and matching branches of the tape and the brake moments developed by the internal and external friction pairs. On the basis of dynamic and thermal loading of the latter, rational structural parameters of the brake were determined.
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Birznieks, Ingvars, Magnus K. O. Burstedt, Benoni B. Edin, and Roland S. Johansson. "Mechanisms for Force Adjustments to Unpredictable Frictional Changes at Individual Digits During Two-Fingered Manipulation." Journal of Neurophysiology 80, no. 4 (October 1, 1998): 1989–2002. http://dx.doi.org/10.1152/jn.1998.80.4.1989.
Повний текст джерелаАнотація:
Birznieks, Ingvars, Magnus K. O. Burstedt, Benoni B. Edin, and Roland S. Johansson. Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation. J. Neurophysiol. 80: 1989–2002, 1998. Previous studies on adaptation of fingertip forces to local friction at individual digit–object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces increased at both fingers. Thus to independently adapt fingertip forces to the local friction the normal forces were controlled at an interdigital level by using sensory information from both engaged digits. Furthermore, subjects used both short- and long-term anticipatory mechanisms in a manner consistent with the notion that the central nervous system (CNS) entertains internal models of relevant object and task properties during manipulation.
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Paliichuk, І. І. "Stress-Strain State of the Bottom of the Casing String in the Horizontal Well." Prospecting and Development of Oil and Gas Fields, no. 4(73) (December 30, 2019): 54–64. http://dx.doi.org/10.31471/1993-9973-2019-4(73)-54-64.
Повний текст джерелаАнотація:
The purpose of the work is to develop the method for calculating the stress-strain state parameters of the bottom of the casing which is lowered into a horizontal well during its construction. When pushed into a well, a long casing string on the supports experiences cross bendings and bucklings which are caused by its own gravity and frictional forces created by axial forces of string compression. The latter are variables in length and depend on the reactions at the supports. The problem is solved by integrating the differential equation of the long rod buckling caused by its own gravity. In a first approximation, the reactions at the supports are found out disregard-ing the axial forces of friction. The author finds the general solution of the basic differential equation of horizontal pipe column deformations taking into account friction and axial forces acting during its lowering. It forms the basis for calculating bucklings and bendings, angles of rod rotation, its inner bending moments and cross forces at the sections between the supports. Geometric and power parameters of pipe deformations at the sections between the supports can be determined using the system of equations of the compatibleness of the angles of rotation and the support moments equilibrium. These equations contain axial force parameters, which can also be derived using the suggested system of algebraic equations. The solution of the problem becomes possible due to adding the transverse force equations to this system. These equations are obtained on the basis of the established relation between transverse and axial forces in the column and reactions and friction at the supports. It allows determining the axial compressive forces simultaneously. The method of linearization of the algebraic equations system and its iterative solution with high accuracy is developed. Due to the value of axial forces, calculated in a first approxi-mation, the system becomes linear, and its iterative solution allows finding the desired parameters with high accu-racy. The obtained results take into account the requirements to the construction technology of a horizontal well. The author considers the deviations of the well direction from the horizontal on the change of the stress-strain state of the casing. The paper offers the formulae to calculate the optimal distance between the casing centralizers as well as solves the problem of its reverse motion. The author takes into consideration additional moments of frictional forces affecting the casing centralizers. The obtained results might serve for the analysis of the stress-strain state of the casing column in the technological process of the horizontal well construction which makes it possible to increase its reliability and lifelength.
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Baktash, Parvaneh, and Cedric Marsh. "Damped moment-resistant braced frames: a comparative study." Canadian Journal of Civil Engineering 14, no. 3 (June 1, 1987): 342–46. http://dx.doi.org/10.1139/l87-054.
Повний текст джерелаАнотація:
This paper reports a study on the comparisons between the behaviours of braced steel building frames with friction joints and with eccentric bracing, under seismic forces. Nonlinear time-history dynamic analysis is used. Friction damping is shown to be of particular merit. Key words: bracing, damping, ductility, dynamics, earthquakes, eccentric; energy dissipation, friction, hysteresis loops, response, steel frames, time history.
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Ahmadizadeh, M., A. M. Shafei, and R. Jafari. "Frictional Impact-Contacts in Multiple Flexible Links." International Journal of Structural Stability and Dynamics 21, no. 06 (March 10, 2021): 2150075. http://dx.doi.org/10.1142/s0219455421500759.
Повний текст джерелаАнотація:
Multiple impacts of 2D (planar) open-loop robotic systems composed of [Formula: see text] elastic links and revolute joints are studied in this paper. The dynamic equations of motion for such systems are derived by the Gibbs-Appell recursive algorithm, while the regularized method is employed to model the impact-contact mechanism. The Timoshenko beam theory is used to model the transverse vibrations of the links. Also, both the structural damping and air damping are considered to enhance the modeling accuracy. The system joints are assumed to be frictionless and slack-free, but friction force is included for the links colliding with the ground. The [Formula: see text]-flexible-link system considered goes through a flight phase and an impact phase during its motion. In the impact phase, new equations of motion are derived by including the terms caused by the viscoelastic forces in the system’s differential equations. Owing to the extremely short acting time of the impact force, the related differential equations can be solved only via special treatment, i.e. by detecting the exact moment of impact. To this end, entering or leaving the impact phase is analyzed and controlled with high precision by a special computational algorithm presented in this work. To demonstrate the efficacy and precision of the algorithm developed, computer simulations are conducted to study the dynamic behavior of a 3-link robotic mechanism. To investigate the effect of mode shape on the elastic deformation of links, four different mode shapes are used in the simulations and their results are compared.
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Schruben, Dale L. "Frictional force and impulse measured in the slip method of determining inertial moment." American Journal of Physics 54, no. 12 (December 1986): 1143–45. http://dx.doi.org/10.1119/1.14733.
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Raghunathan, M., Y. Marandet, H. Bufferand, G. Ciraolo, Ph Ghendrih, P. Tamain, and E. Serre. "Multi-temperature generalized Zhdanov closure for scrape-off layer/edge applications." Plasma Physics and Controlled Fusion 64, no. 4 (February 11, 2022): 045005. http://dx.doi.org/10.1088/1361-6587/ac414d.
Повний текст джерелаАнотація:
Abstract The derivation of the multi-temperature generalized Zhdanov closure is provided, starting from the most general form of the left-hand side of the moment-averaged kinetic equation with the Sonine–Hermite polynomial ansatz for an arbitrary number of moments. The process of arriving at the reduced higher-order moment equations, with its assumptions and approximations, is explicitly outlined. The generalized multi-species multi-temperature coefficients from our previous article are used to compute values of higher-order moments such as heat flux in terms of the lower-order moments. Transport coefficients and the friction and thermal forces for magnetic confinement fusion relevant cases with the generalized coefficients are compared to the scheme with the single-temperature coefficients previously provided by Zhdanov et al. It is found that the 21 N-moment multi-temperature coefficients are adequate for most cases relevant to fusion. Furthermore, the 21 N-moment scheme is also tested against the trace approximation to determine the range of validity of the trace approximation with respect to fusion-relevant plasmas. Possible refinements to the closure scheme are also illustrated to account for quantities which might be significant in certain schemes, such as the drift approximation.
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Spector, A., and R. C. Batra. "On the Motion of an Elastic Body Rolling/Sliding on an Elastic Substrate." Journal of Tribology 117, no. 2 (April 1, 1995): 308–14. http://dx.doi.org/10.1115/1.2831248.
Повний текст джерелаАнотація:
The three-dimensional evolutionary problem of rolling/sliding of a linear elastic body on a linear elastic substrate is studied. The inertial properties of the body regarded as rigid are accounted for. By employing an asymptotic analysis, it is shown that the process can be divided into two phases: transient and quasistationary. An expression for the frictional force as a function of the externally applied forces and moments, and inertial properties of the body is derived. For an ellipsoid rolling/sliding on a linear elastic substrate, numerical results for the frictional force distribution, slip/adhesion subareas, and the evolution of the slip velocity are given.
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Pytka, Jaroslaw, Piotr Budzyński, Tomasz Łyszczyk, Jerzy Józwik, Joanna Michałowska, Arkadiusz Tofil, Dariusz Błażejczak, and Jan Laskowski. "Determining Wheel Forces and Moments on Aircraft Landing Gear with a Dynamometer Sensor." Sensors 20, no. 1 (December 31, 2019): 227. http://dx.doi.org/10.3390/s20010227.
Повний текст джерелаАнотація:
This paper describes airfield measurement of forces and moments that act on a landing gear wheel. For the measurement, a wheel force sensor was used. The sensor was designed and built based on strain gage technology and was embedded in the left landing gear wheel of a test aircraft. The sensor is capable of measuring simultaneously three perpendicular forces and three moments and sends data to a handheld device wirelessly. For the airfield tests, the sensor was installed on a PZL 104 Wilga 35A multipurpose aircraft. The aircraft was towed at a “marching man” speed and the measurements were performed at three driving modes: Free rolling, braking, and turning. The paper contains results obtained in the field measurements performed on a grassy runway of the Rzeszów Jasionka Aerodrome, Poland. Rolling resistance of aircraft tire, braking friction, as well as aligning moment were analyzed and discussed with respect to surface conditions.
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Vogel, Danny, Paul Henke, Annika Haenel, Jan Mokros, Martin Liebelt, and Rainer Bader. "Experimental evaluation of the primary fixation stability of uncemented ceramic hip resurfacing implants." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 236, no. 4 (February 15, 2022): 496–503. http://dx.doi.org/10.1177/09544119211070892.
Повний текст джерелаАнотація:
Hip resurfacing arthroplasty is associated with increased frictional moments compared to standard heads owing to their large diameter. High frictional moments may harbor the risk of the implant loosening if the frictional moments exceed the fixation stability of the hip resurfacing arthroplasty. Therefore, the aim of this experimental study was to evaluate the fixation stability of ceramic hip resurfacing implants through a turn-off test. The test specimens, made of alumina toughened zirconia (ATZ) ceramics with an inner titanium-coated surface and square base bodies for better application to the test setup, were pushed on artificial bone materials until a predefined seating depth was achieved. Thereafter, the specimens were turned off from the artificial bone material by using a lever-arm and the turn-off moments were calculated. The density of the artificial bone material utilized (15 and 25 pcf), the press-fit (0.4 and 0.8 mm) and the size of the test specimens varied. The push-on forces ranged from 0.6 ± 0.1 kN to 5.6 ± 0.5 kN depending on the press-fit and artificial bone material. The turn-off moments relied on the respective press-fit, artificial bone material and size of the specimen. They belonged between the range of 8.5 ± 0.4 Nm and 105.4 ± 0.2 Nm. Most of the previously described frictional moments are lower compared to the turn-off moments determined in this study. However, in the worst-case scenario, the turn-off moments of the hip resurfacing implants may be reduced, especially when the adjacent bone stock has a low mineral density.
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Badreldin, A., and A. Seireg. "Generalized Solution for the Optimal Prehension State Using End Effectors With Multi-Articulated Fingers." Journal of Mechanical Design 112, no. 1 (March 1, 1990): 84–89. http://dx.doi.org/10.1115/1.2912584.
Повний текст джерелаАнотація:
A general formulation for the mechanics of the grasp with elastic multi-articulated fingers is presented. A procedure utilizing linear programming is given for computing a unique solution for the normal forces as well as the frictional forces and moments at the contact areas which insures stability of the grasp at the considered configuration. The procedure is particularly useful when the deformation or precision movement of the grasped object is of importance. An efficient optimization algorithm is also given to determine the best grasping configuration for any shape object undergoing any task using end effectors with any number of fingers.
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Liu, Jing, Yajun Xu, Yimin Shao, Huifang Xiao, and Hongwu Li. "The effect of a localized fault in the planet bearing on vibrations of a planetary gear set." Journal of Strain Analysis for Engineering Design 53, no. 5 (April 23, 2018): 313–23. http://dx.doi.org/10.1177/0309324718769491.
Повний текст джерелаАнотація:
Dynamic characteristics of a planetary gear set can be greatly affected by a localized fault in the planet bearing. To understand the relationship between the dynamic characteristic of the planetary gear set and the localized fault sizes, a dynamic finite element model for a planetary gear set is developed. A localized fault is assumed to be located in the outer race of the planet bearing. The fault profile is defined as a rectangular one. To formulate the elastic deformations of the components and elastic contact deformations between the mating components, all components of the planetary gear set are considered as elastic bodies in the finite element model. A standard gravity is also considered in the finite element model. A Coulomb frictional model is used to formulate the frictional forces in the planetary gear set. Influences of the rotational velocity, moment, and fault width on the dynamic characteristics of the planetary gear set are discussed. The simulation results are compared with those from the previous method to validate the finite element model. It seems that the presented finite element model can be applied to simulate the dynamic characteristics of a planetary gear set caused by a localized fault in the outer race of the planet bearing.
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POPOLO, ANTONINO DEL, and S. YEŞILYURT. "ON THE NATURE OF GRAVITATIONAL FORCES." International Journal of Modern Physics D 16, no. 08 (August 2007): 1349–68. http://dx.doi.org/10.1142/s0218271807010808.
Повний текст джерелаАнотація:
In this paper, we will show how the statistics of the gravitational field is changed when the system is characterized by a non-uniform distribution of particles. We will show how the distribution functions W(F) and W(F,dF/dt), giving the joint probability that a test particle is subject to a force F and an associated rate of change of F given by dF/dt, are modified by inhomogeneity. Then we will calculate the first moment of dF/dt to study the effects of inhomogenity on dynamical friction. Finally we will test, by N-Body simulations, that the theoretical W(F) and dF/dt describes correctly the experimental data and we find that the stochastic force distribution obtained for the evolved system is in good agreement with theory. Moreover, we find that in an inhomogeneous background, the friction force is actually enhanced relative to the homogeneous case.
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Woodhead, Johnpaul, Julian D. Booker, Christopher E. Truman, and Vadim Davydov. "Measurement of Forming Stresses in Plain Spherical Bearings Using Neutron Diffraction." Materials Science Forum 777 (February 2014): 58–64. http://dx.doi.org/10.4028/www.scientific.net/msf.777.58.
Повний текст джерелаАнотація:
Nosing is a cold metal-forming process used in the manufacture of plain spherical bearings. This process ensures the outer bearing race conforms to the shape of the inner race (a ball), with a composite liner in-between to provide a low frictional moment. These bearings must be precision engineered due to the large forces and demanding environments they operate within in service. The manufacture of these bearings and related process settings is very much an experiential route, although increasingly Finite Element simulations are used to predict and characterise complex material behaviour. It is imperative the numerical nosing models are validated against experimental measurements due to uncertainties in material properties, process variables and part manufacture variations. In this paper, neutron diffraction is used to determine the residual stresses in a large nosed bearing. Measurements were made on the POLDI instrument at PSI, Switzerland. This paper compares the predicted stresses with measurement results, and draws conclusions concerning the validity and usability of the models.
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Lee, Soo Hong, and M. R. Cutkosky. "Fixture Planning With Friction." Journal of Engineering for Industry 113, no. 3 (August 1, 1991): 320–27. http://dx.doi.org/10.1115/1.2899703.
Повний текст джерелаАнотація:
A fixture planning module is being developed as part of a computational system for concurrent product and process design. The module employs symbolic and numerical analyses at different levels of detail, from fast geometric checks to more time consuming force and friction analyses, depending on the completeness of the machining plan. In this paper we focus on the approaches used for analyzing fixture kinematics and clamping forces, including the analysis of friction. Since many fixture arrangements rely on friction to hold a part, the ability to reason about friction is an important component of fixture planning. Limit surfaces in force/moment space are introduced as a convenient formalism to check whether parts will slip and to help in specifying clamping forces.
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Stavytskyi, Valerii, Oleksandr Bashta, Pavlo Nosko, and Yurii Tsybrii. "Determination of Hydrodynamic Power Losses in a Gearing." Acta Mechanica et Automatica 16, no. 1 (January 1, 2022): 1–7. http://dx.doi.org/10.2478/ama-2022-0001.
Повний текст джерелаАнотація:
Abstract Despite the relatively numerous experimental studies, there are few published works on the topic of development of mathematical models that describe the hydrodynamic processes in gears. There is no generic analytical model that integrates all types of losses. The purpose of this work is to develop a modern generalised methodology for calculating the hydrodynamic power losses of high-speed gears. For each gear, partially or fully immersed into an oil bath, the power spent to overcome the hydromechanical resistance can be represented as the sum of the following: the Coriolis force moment arising from the radial movement of the oil in the tooth spaces of the rotating gear, the viscous friction forces moment on the periphery of the gear addendums in the oil bath and the viscous friction forces moment at the face of the gear in the oil bath. The hydrodynamic power losses due to the Coriolis force action, viscosity friction losses at the periphery of the gear and the viscosity friction at the face of the gear (both turbulent and laminar modes) were observed separately. From the mathematical simulation of the rotation processes when the gear is immersed into the oil bath, an analytical dependence was obtained. It allows predicting the influence of the geometrical parameters of the gearing on the hydrodynamic power losses. Analysis of the calculation results of the power losses due to the action of hydraulic resistance forces and results from experimental studies is provided for several gears with different hydromechanical parameters. The proposed method of calculating power loss due to hydromechanical resistance of the oil bath to the rotation of the gear gave results that were close to the experimental data. Acceptable coincidence of theoretical and experimental results allows recommending the received analytical dependencies for practical calculations of high-speed gears.
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Лесных, К. А., С. А. Никонов, and Н. В. Островская. "Features of dynamic problems with friction calculation by means of an «ADAMS» package." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII), no. 2(52) (June 20, 2021): 130–37. http://dx.doi.org/10.37220/mit.2021.52.2.043.
Повний текст джерелаАнотація:
Актуальность поднимаемых в статье вопросов обусловлена широким применением программных комплексов для численного эксперимента в области механики и необходимостью верификации полученных результатов. В представленной работе отражены возможности программного пакета виртуального моделирования ADAMS для численного анализа динамических задач с учетом трения. В качестве объекта исследования рассмотрено устройство кривошипно-шатунного механизма, имеющего в своём составе фрикционную муфту. Для демонстрации возможностей моделирования задач с учетом трения в ПК ADAMS приведены различные примеры, верифицирующие аналитические решения с численными. Для исследования работы муфты была подтверждена зависимость момента сил трения от относительной скорости и смоделирована работа кривошипно-шатунного механизма. Отдельно была рассмотрена задача о получении коэффициентов трения качения, которые в результате моделирования в ПК ADAMS, оказываются значительно меньше своих предельных коэффициентов трения качения. The relevance of the issues raised in the article is due to the widespread use of software systems for numerical experiments in the field of mechanics and the need to verify the results obtained. Possibilities of the virtual modeling software package ADAMS for the numerical analysis of dynamic tasks taking into account friction are reflected in work. As an object of a research the device of the crank-conrod mechanism in corporating the frictional coupling is considered. For demonstration of tasks taking into account friction modeling opportunities in an ADAMS package various examples verifying analytical decisions with numerical are given. For a research of the coupling the dependence of the friction forces moment operation on relative speed was confirmed and operation of the crank-conrod mechanism is simulated. The task about receiving coefficients of swing friction which as a result of modeling in an ADAMS package, appear much less than the limit coefficients of swing friction was separately considered.
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Fischer, Steven L., Bryan R. Picco, Richard P. Wells, and Clark R. Dickerson. "The Roles of Whole Body Balance, Shoe-Floor Friction, and Joint Strength During Maximum Exertions: Searching for the “Weakest Link”." Journal of Applied Biomechanics 29, no. 1 (February 2013): 1–11. http://dx.doi.org/10.1123/jab.29.1.1.
Повний текст джерелаАнотація:
Exerting manual forces is critical during occupational performance. Therefore, being able to estimate maximum force capacity is particularly useful for determining how these manual exertion demands relate to available capacity. To facilitate this type of prediction requires a complete understanding of how maximum force capacity is governed biomechanically. This research focused on identifying how factors including joint moment strength, balance and shoe-floor friction affected hand force capacity during pulling, pressing downward and pushing medially. To elucidate potential limiting factors, joint moments were calculated and contrasted with reporte joint strength capacities, the balancing point within the shoe-floor interface was calculated and expresess relative to the area defined by the shoe-floor interface, and the net applied horizontal forces were compare with the available friction. Each of these variables were calculated as participants exerted forces in a series o conditions designed to systematically control or restrict certain factors from limiting hand force capacity. The results demonstrated that hand force capacity, in all tested directions, was affected by the experimental conditions (up to 300%). Concurrently, biomechanical measures reached or surpassed reported criterion threshold inferring specific biomechanical limitations. Downward exertions were limited by elbow strength, wherea pulling exertions were often limited by balance along the anterior-posterior axis. No specific limitations wer identified for medial exertions.
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Sepehri, Ali, and Kambiz Farhang. "Closed-Form Equations for Contact Force and Moment in Elastic Contact of Rough Surfaces." Modelling and Simulation in Engineering 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/739562.
Повний текст джерелаАнотація:
It is reasonable to expect that, when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply noneven distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper, we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment, and thereby contact moment is derived. Through this scheme, it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force, however, is shown to be of a much smaller order than the contact normal force. Approximate closed-form equations are found for contact force and moment for the contact of rough surfaces.
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Park, K. S., C. W. Oh, T. W. Kim, Hyun-Yong Jeong, and Y. H. Kim. "An improved friction model and its implications for the slip, the frictional energy, and the cornering force and moment of tires." Journal of Mechanical Science and Technology 20, no. 9 (September 2006): 1399–409. http://dx.doi.org/10.1007/bf02915963.
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Komnik, Igor, Sina David, Christine Haberrer, Stefan Weiss, and Wolfgang Potthast. "Influence of friction on knee internal rotation in patients with knee arthroplasties during activities of daily living." Orthopaedic Journal of Sports Medicine 7, no. 6_suppl4 (June 1, 2019): 2325967119S0022. http://dx.doi.org/10.1177/2325967119s00224.
Повний текст джерелаАнотація:
Aims and Objectives: In recent decades, knee arthroplasty (KA) succeeded to improve patients’ clinical scores and gait patterns [1]. However, to date, studies primary focused on biomechanical analysis of level walking with total knee arthroplasty (TKA) patients. The investigation of neuromuscular more challenging activities of daily living (ADL) like stair climbing and especially ramp negotiation was partly neglected [2]. Furthermore, non-sagittal plane parameters have mostly not been considered, whereby the evaluation of e.g. transverse plane kinematics and kinetics may reveal potential differences between various endoprosthetic designs. Additionally, frictional forces transmit appreciable shear between the femoral component and the tibial polyethylene insert, potentially contributing to axial knee rotational constraints and implant loosening [3]. The aim of this study was to investigate transverse plane kinematics and kinetics in connection with the force of friction (FOF) during ADL in patients after TKA and unicondylar knee arthroplasty (UKA) surgery. Materials and Methods: - Motion analysis was performed using a ten-camera 3D- motion capture system (100 Hz, Vicon). - Ground reaction forces were measured utilizing in a total five force plates (1000 Hz, Kistler) - Kinematics and inverse dynamics were calculated with AnyBody Modeling SystemTM (AnyBody Technology). - FOF was estimated of the two articulating artificial surfaces (#CHR: mu_LOWER# =0.12) compared with the cartilage on cartilage friction (#CHR: mu_LOWER# =0.01). The Coulomb model of friction was applied to calculate FOF (Ff=Fn* #CHR: mu_LOWER#). - Completed ADL: level and decline walking, stair descent. - Participants: TKA (n=11), UKA (n=13), controls (CG, n=13). - Statistics: Statistical non-Parametric Mapping (SnPM). Results: No statistically significant differences were detected between the TKA and UKA group, regardless of the locomotion task. Each motor task revealed impaired knee internal rotation angles in the TKA group compared with the CG (Fig. 1, a-c). Fig. 1 (d) clarifies the determining role of the coefficient of friction regarding FOF which showed the highest values during stair ascent and decline walking in all groups. Interestingly, the mentioned tasks exposed lower knee internal moment time series compared with level walking. Lower internal rotation moments might contribute in connection with high friction to the constraint knee internal rotation motion, particularly during ADL including greater normal force values, such as stair climbing and ramp negotiation. Conclusion: Apart from implant congruency in the TKA group, FOF could represent a mechanical resistance, which contributes to the impaired knee motion in the transverse plane. References Smith A, et al., J Orthop Res. 22:260-266, 2004. Komnik I, et al., Gait Posture. 41:370-377, 2015. Wolterbeek N, et al., Gait Posture. 36:394-398, 2012
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Li, Jingyuan, Qinghe Zhang, and Tongqing Chen. "Numerical Investigation of Internal Solitary Wave Forces on Submarines in Continuously Stratified Fluids." Journal of Marine Science and Engineering 9, no. 12 (December 3, 2021): 1374. http://dx.doi.org/10.3390/jmse9121374.
Повний текст джерелаАнотація:
A numerical model of internal solitary waves in continuously stratified fluids is developed by introducing a density transport equation to the three-dimensional Navier–Stokes equation and adopting the fully nonlinear models of the Dubreil-Jacotin-Long equation to obtain the initial field of the ISW. The corresponding turbulence model has also been modified to ensure that it considers the variable density field. Comparisons between numerical simulation results and experimental results show that the total resistance, the nondimensional pressure coefficient, and the nondimensional friction coefficient for the standard submarine model proposed by the Defense Advanced Research Projects Agency under different flow field conditions are highly consistent with the experimental results. The model established is used to numerically analyse the forces and moments of the standard submarine model encountering ISWs at different submergence depths. The influence of the rotation centre position on the moment is discussed, and the position range of the optimal rotation centre is proposed.
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Feng, Chang Lin, De Shi Wang, and Yong Yong Zhu. "Analysis of Moment Transmitted by Universal Joint in Varying Operating Condition." Advanced Engineering Forum 2-3 (December 2011): 999–1003. http://dx.doi.org/10.4028/www.scientific.net/aef.2-3.999.
Повний текст джерелаАнотація:
The moments transmitted by a universal joint in varying operating condition was investigated. A model of shaft system driven by a universal joint which consists of a driving shaft, a driven shaft and a cross piece is chose. Both structure misalignment and error misalignment between the two shafts at the universal joint was considered, and the study was based on the assumption that friction, inertia and elastic forces of the cross piece were disregarded. Two pairs of Euler angles were introduced to denote structure misalignment and error misalignment respectively, sets of reference frames were built up on the driving shaft, driven shaft and cross piece. Using direction cosine matrixes to describe the relation between different frames, then the expressions of components of the transmitted moment acting on the driven shaft were obtained via method of vector projection. Based on engineering fact, the transmitted moment model was simplified with respect to different misalignment conditions, such as only structure misalignment or only error misalignment is considered. Then for different misalignment situations, the lateral and torsional components of the transmitted moment acting on the driven shaft were simulated through numerical examples. It turns out that both the lateral moment and torque components will fluctuate based on the import torque, and that due to accelerating of the driving shaft, the fluctuation of transmitted moment will be more distinct, consequently, more complicated nonlinear dynamics behavior will arise.
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Jian, Xiao Gang, Peng Chun Yang, and Ye Feng Wang. "Force Analysis and Numerical Simulation of Screw Mechanism for Subsurface Robotic Exploration." Applied Mechanics and Materials 189 (July 2012): 433–37. http://dx.doi.org/10.4028/www.scientific.net/amm.189.433.
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A scheme of drilling robot, which is propelled by the screw mechanism, is proposed for subsurface exploration. Firstly, in order to analyze the forces acting on the screw, theoretical model for the working principle of the robot is built, and by this model the soil friction moment, propelling and resisting forces can be calculated. Secondly, with the help of ANSYS/LS-DYNA, the dynamic numerical simulation of the interaction between the screw mechanism and the soil is conducted and the results verify the feasibility of the screw propelling method for the robot.
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ZHANG, KUNPENG, and QIAN DING. "LATERAL AND TORSIONAL VIBRATIONS OF A TWO-DISK ROTOR-STATOR SYSTEM WITH AXIAL CONTACT/RUBS." International Journal of Applied Mechanics 01, no. 02 (June 2009): 305–26. http://dx.doi.org/10.1142/s1758825109000137.
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The dynamics of a rotor system with axial contact/rub events between the disks and stator are investigated by numerical simulations. The formula for determining the contact/rub points, axial contact forces and dry friction forces are deduced. To account for their influence, the axial contact forces are substituted by equivalent forces acting at the disk centers, based on the equivalent moment rule. One-parametric model is used to estimate the contact-induced dry friction forces. The coupled equations of lateral and torsional motions of rotor and the lateral motion of disk are then established. Numerical simulations are carried out to reveal the lateral and torsional vibrations for both two-disk contact/rubs with different axial clearances, and one disk contact/rubs. Bifurcation diagrams, orbits, phase portraits, amplitude-frequency spectra and Poincaré maps are adopted to demonstrate the dynamical behaviors of the system. The results show that though both the lateral and torsional vibrations can reflect the influences of contact/rubs on rotor dynamics, the spectrum analyses of the torsional vibrations are more suitable to determine straight the extent of their effect.
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Wu, Yu Hou, Jia Sun, and Ke Zhang. "Analysis of Stress-Strain Distribution for Wire Rope of Traction Hoister." Applied Mechanics and Materials 268-270 (December 2012): 1198–202. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.1198.
Повний текст джерелаАнотація:
Besides the material properties and operating environment, the strain and strain state of the wires in multi-stage twisted rope with large frictional contact force, as applied in traction hoister of suspended access platform, strongly influence their service life. For an accurate quantitative prediction of the performance and a proper understanding of the underlying phenomena, a detailed analysis of the stress-strain distribution along all individual wires is required. For this, a numerical model for a wore rope in traction hoister was describe to be considering the complex strand pattern, mutual interaction by contacts form surrounding strands and contact deformation, in this paper. The model well understood response of wire rope under an axial tensile load and twisting moment, and concise described the effects of rope deformation on the rotate ratio and slip behavior of the hoister. The results of this model were compared with the experiment analyzed, which showed that the inclusion of interfacial forces at the contact locations and their associated effects of internal force of helical wires is importance.
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Yun, Zhao, Yu Gao-Hong, Chen Jian-Neng, and Li Ge. "Mechanism Dynamics Sequence-Solution Method and Its Application." Journal of Computational and Nonlinear Dynamics 2, no. 2 (December 8, 2006): 105–13. http://dx.doi.org/10.1115/1.2447074.
Повний текст джерелаАнотація:
In order to eliminate the interference of reverse-driving and the positive or negative value of normal pressure on the direction of frictional force, in solving mechanism dynamics equations, a dynamics sequence solution (DSS) is proposed. For this purpose a moment equation about joints for links is proposed, and it, together with the traditional mechanics equation of links, forms a dynamic-equation set, to provide a basic equation set of mechanism dynamics. In order to explain DSS, the force at a particular joint is considered in terms of the normal and tangential directions, and the resolution of the problem using a four-bar linkage mechanism as an example, are explained. The solution procedures diagrams for different driving types of reverse-driving force, as well as the solution process for friction force under normal pressure, are described. With a dry-straw-compression mechanism as the example, a dynamic model of the mechanism is established, and the above proposed DSS is used to find unknown forces. Finally, the dynamic characteristics of rotary-transplanting mechanisms (the key component of high-speed rice transplanter) are analyzed, through the proposed DSS, and the results are verified in a test-bed situation. The consistency of the test results with the theoretical ones shows that the proposed DSS is able to effectively solve the dynamics equations of complicated mechanisms. In this part, the authors introduced DSS and discussed the feasibility of its application.
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Jones, Lynette A. "Matching Forces: Constant Errors and Differential Thresholds." Perception 18, no. 5 (October 1989): 681–87. http://dx.doi.org/10.1068/p180681.
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A contralateral limb-matching procedure was used to study the perception of forces generated by the elbow flexor muscles. Subjects were required to generate forces ranging from 15 to 85% of their maximum voluntary contraction (MVC range: 169–482 N), and after achieving the target force to produce a force of the same perceived intensity with their contralateral arm. Under these conditions, subjects consistently overestimated the amplitude of the two lowest forces, and the most accurate matching of forces occurred in the middle of the response range (around 50% MVC). This pattern of constant errors could be explained in terms of an artifact of the starting position, which has been shown to influence the accuracy of judgements of stimulus magnitude. The Weber fraction for force calculated from the matching data was 0.07, which is within the range reported previously for weight. These thresholds are, however, considerably lower than those described for friction and the moment of inertia, the perception of which also involves the proprioceptive system.
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Ettema, Gertjan J. C., Steinar Bråten, and Maarten F. Bobbert. "Dynamics of the In-Run in Ski Jumping: A Simulation Study." Journal of Applied Biomechanics 21, no. 3 (August 2005): 247–59. http://dx.doi.org/10.1123/jab.21.3.247.
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A ski jumper tries to maintain an aerodynamic position in the in-run during changing environmental forces. The purpose of this study was to analyze the mechanical demands on a ski jumper taking the in-run in a static position. We simulated the in-run in ski jumping with a 4-segment forward dynamic model (foot, leg, thigh, and upper body). The curved path of the in-run was used as kinematic constraint, and drag, lift, and snow friction were incorporated. Drag and snow friction created a forward rotating moment that had to be counteracted by a plantar flexion moment and caused the line of action of the normal force to pass anteriorly to the center of mass continuously. The normal force increased from 0.88G on the first straight to 1.65G in the curve. The required knee joint moment increased more because of an altered center of pressure. During the transition from the straight to the curve there was a rapid forward shift of the center of pressure under the foot, reflecting a short but high angular acceleration. Because unrealistically high rates of change of moment are required, an athlete cannot do this without changing body configuration which reduces the required rate of moment changes.
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YOKOSE, Keiji, Seiji KASAGI, Yutaka TAKANO, and Ryuji ARAKI. "A combined effect of frictional and elastic moment against truck turning on forced hunting of a bogie car." Transactions of the Japan Society of Mechanical Engineers Series C 55, no. 519 (1989): 2769–76. http://dx.doi.org/10.1299/kikaic.55.2769.
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Pilipchuk, V. N., R. A. Ibrahim, and P. G. Blaschke. "Disc Brake Ring-Element Modeling Involving Friction-Induced Vibration." Journal of Vibration and Control 8, no. 8 (August 2002): 1085–104. http://dx.doi.org/10.1177/107754602029587.
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This paper presents the analytical modeling and dynamic characteristics of disc brake systems under equal contact loads on both sides of the disc. The friction force acting on the pad is assumed to be concentrated along its trailing edge due to the moment arising from the friction force, and thus results in a redistribution of normal forces. In view of equal contact forces, the disc will not experience transverse motion but only tangential and radial vibrations. The only nonlinearity involved in the model arises mainly from contact forces. The dependence of the friction coefficient between the pad and disc is smoothed at zero relative velocity to avoid the problem of differential inclusion. Some preliminary numerical results of the disc and pad are obtained. The results exhibit the occurrence of stick-slip with a relatively small high frequency component during the sliding regime. The later component is mainly due to higher elastic in-plane modes of the disc, whereas the stick-slip component is a global disc-pad motion involving the lowest pad mode.
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Andreev, A. I., and A. P. Perekrestov. "Analysis on non-stationary gyroscopes and their application in measurement technology." Journal of Physics: Conference Series 2091, no. 1 (November 1, 2021): 012006. http://dx.doi.org/10.1088/1742-6596/2091/1/012006.
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Abstract In this work, the main subjects of research are: 1) analysis of the process of rotation of a Chinese top on a flat surface, 2) analysis of the main dependencies and an explanation of the rise of the center of gravity of the top during rotation due to nonlinear friction and the resulting force of the overturning top on the upper axis. Also, an analytical study of the motion of the top along the plane and the laws of rotation was carried out, the rotation of the top was analyzed from the point of view of asymmetry during rotation. The top-top spinning top is an interesting case of raising the center of gravity during rotation. The simplest model of a Chinese top can be a dynamic symmetric inhomogeneous ball, the center of mass of which lies on the axis of dynamic symmetry, but does not coincide with its geometric center. The precession of the Chinese top is based on dry friction. The occurrence of a gyroscopic deflection moment is based on the frictional force. Considering the simplest top-type top, one can distinguish the main forces acting on this body, as well as its characteristics that determine the precession. Based on this fact, it is possible to propose the use of this body of revolution as a working medium for instruments such as tribometers and gravimeters. In the first case, this makes it possible to increase the accuracy of the device, in the second, to create a new scheme for measuring gravitational fields. The relevance of this work is the analysis of the rotation of the Chinese top and the possibility of its use in measuring instruments.
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Iraqi, Arian, and Kurt E. Beschorner. "Vertical Ground Reaction Forces During Unexpected Human Slips." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 61, no. 1 (September 2017): 924–28. http://dx.doi.org/10.1177/1541931213601713.
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Falls due to slippery conditions are among the primary causes of disabling workplace injuries. Despite the extensive amount of human slip studies in the literature, only a handful of studies have reported ground reaction forces at the instant of slip initiation. The purpose of this study was to quantify the vertical ground reaction forces (VGRF) at slip initiation during unexpected human slips across different footwear-contaminant conditions. Forty-seven healthy subjects were unexpectedly exposed to a liquid–contaminant, while the vertical force was measured at the moment that the foot began to start slipping. The average VGRF were between 100 and 300 N and varied significantly across the footwear. These forces were significantly less than the typical forces (400-700 N) applied during slip-resistance measurements. This finding may suggest that available coefficient of friction (ACOF) measurements should use lower force levels in order to achieve higher relevance to the onset of slipping.
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Gilavdary, I. Z., S. Mekid, and N. N. Riznookaya. "Device and Measuring Method the Moments of Rolling Resistance Forces on the Contact Spot." Devices and Methods of Measurements 10, no. 4 (December 12, 2019): 308–21. http://dx.doi.org/10.21122/2220-9506-2019-10-4-308-321.
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Currently, the study of rolling friction is one of the main directions in the study of the laws of contact interaction of solids. The complexity of solving the problems existing in this area is evidenced by the practically vast number of publications, the list of which is constantly growing.In this paper, attention is paid to studies of the moments of rolling resistance at displacements from the equilibrium position of a ball-shaped body that are substantially smaller than the size of the contact spot. The purpose of the present work is to describe the design of the single-contact pendulum device developed by the authors, in which the physical pendulum, resting on the flat surface of the body under study with only one ball, makes free small stable swings in a vertical plane, as well as in the description of a special measurement technique with high sensitivity and accuracy rolling resistance forces, including adhesion forces and frequency-independent forces of elastic deformations. It is assumed that the adhesion forces can exhibit both dissipative properties and elastic properties, while elastic forces are independent of the strain rate.The originality of the method of measuring rolling resistance in this paper consists in using the method of nonlinear approximation of the dependence of the amplitude and period of swing of the pendulum on time. The approximation is carried out on the basis of the proposed laws of amplitude decay and period variation, which differ from the usual exponential law.It is assumed that this approach allows one to evaluate the surface tension of a solid and evaluate the pressure of adhesion forces between the surfaces of the contacting bodies, as well as to establish an analytical form of the moment of rolling resistance. The curves of the dependence of the rolling resistance moment on the swing amplitude of the pendulum are constructed. Experiments were performed for the following pairs of contacting bodies: steel-steel, steel-glass, steel-electritechnical silicon. It was assumed that the pressure at the contact spot did not exceed the elastic limit.The developed single-ball pendulum device and the proposed measurement procedure open up new wide possibilities for studying the laws of mechanisms of rolling resistance under conditions of microand mesoscale displacements of a rolling body from a state of rest.
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Madhani, A., and S. Dubowsky. "The Force Workspace: A Tool for the Design and Motion Planning of Multi-Limb Robotic Systems." Journal of Mechanical Design 119, no. 2 (June 1, 1997): 218–24. http://dx.doi.org/10.1115/1.2826239.
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The Force Workspace (FW) is a tool for designing mobile robotic systems which apply large forces over large ranges of motion. It can also be used to plan motions that do not violate actuator saturation limits, system-environment force and moment contact constraints such as those due to friction, and kinematic joint limits. The FW is applied to the design analysis and motion planning of a simple robotic climbing machine.
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Chen, Jian Gong, Mei Lin Deng, and Yong Xing Zhang. "Nonlinear Active Earth Pressure Distribution Based on Coulomb's Theory." Applied Mechanics and Materials 90-93 (September 2011): 433–37. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.433.
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On the basis of coulomb’s concept that the active earth pressure against the back of a retaining wall is due to the thrust force exerted by a sliding wedge of soil between the back of the wall and a plane which passes through the bottom edge of the wall and has an inclination of θ, two basis differential equations of first order are set up by considering the equilibrium of the forces and the moments on a partial wedge of soil. The distributing coefficient of active earth pressure is obtained through comparing two basis equations. The unit earth pressure and the application point of the resultant force are deduced. The effects of parameters such as the internal frictional angle of backfill, the frictional angle between the wall back and the backfill, slope angle of filling and dip angle of wall back on distributing coefficient of active earth pressure, the unit earth pressure, the application point of the resultant force, rupture angle are analyzed in detail. Meanwhile the non-linear distributing features are concluded.
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Zhu, Xiao-jun, Kang Fei, and Sheng-wei Wang. "Horizontal Loading Tests on Disconnected Piled Rafts and a Simplified Method to Evaluate the Horizontal Bearing Capacity." Advances in Civil Engineering 2018 (September 16, 2018): 1–12. http://dx.doi.org/10.1155/2018/3956509.
Повний текст джерелаАнотація:
Disconnected piled raft (DPR) foundations have been widely adopted as an effective foundation system where the piles are separated from the raft by a granular layer, which can limit the shear forces and moments transmitted between the raft and the piles. Thus, DPR foundations may avoid the problem of horizontal forces, such as those from an earthquake or dynamic loads, which damage the structural connection between the pile head and raft. A series of static horizontal loading tests were carried out on three types of foundation models, i.e., piled raft, disconnected piled raft, and raft alone models, on fine sand using a geotechnical model in a 1 g field. In this paper, the influences of vertical loading and interposed layer thickness were presented and discussed. The results showed that most of the horizontal force was carried by raft/interposed layer friction in the DPR foundation type, and the shear force and moment of the piles were greatly reduced due to the gap between the raft and the heads of the piles. The tested foundations were simulated using a simplified method with theoretical equations derived by making several approximations and assumptions. The simulated results agreed well with the test results.
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Mokhiamar, Ossama, and Masato Abe. "Simultaneous Optimal Distribution of Lateral and Longitudinal Tire Forces for the Model Following Control." Journal of Dynamic Systems, Measurement, and Control 126, no. 4 (December 1, 2004): 753–63. http://dx.doi.org/10.1115/1.1850533.
Повний текст джерелаАнотація:
This paper presents a proposed optimum tire force distribution method in order to optimize tire usage and find out how the tires should share longitudinal and lateral forces to achieve a target vehicle response under the assumption that all four wheels can be independently steered, driven, and braked. The inputs to the optimization process are the driver’s commands (steering wheel angle, accelerator pedal pressure, and foot brake pressure), while the outputs are lateral and longitudinal forces on all four wheels. Lateral and longitudinal tire forces cannot be chosen arbitrarily, they have to satisfy certain specified equality constraints. The equality constraints are related to the required total longitudinal force, total lateral force, and total yaw moment. The total lateral force and total moment required are introduced using the model responses of side-slip angle and yaw rate while the total longitudinal force is computed according to driver’s command (traction or braking). A computer simulation of a closed-loop driver-vehicle system subjected to evasive lane change with braking is used to prove the significant effects of the proposed optimal tire force distribution method on improving the limit handling performance. The robustness of the vehicle motion with the proposed control against the coefficient of friction variation as well as the effect of steering wheel angle amplitude is discussed.
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Du, Binyang, Mark R. VanLandingham, Qingling Zhang, and Tianbai He. "Direct measurement of plowing friction and wear of a polymer thin film using the atomic force microscope." Journal of Materials Research 16, no. 5 (May 2001): 1487–92. http://dx.doi.org/10.1557/jmr.2001.0207.
Повний текст джерелаАнотація:
Nanometer-scale plowing friction and wear of a polycarbonate thin film were directly measured using an atomic force microscope (AFM) with nanoscratching capabilities. During the nanoscratch tests, lateral forces caused discrepancies between the maximum forces for the initial loading prior to the scratch and the unloading after the scratch. In the case of a nanoscratch test performed parallel to the cantilever probe axis, the plowing friction added another component to the moment acting at the cantilevered end compared to the case of nanoindentation, resulting in an increased deflection of the cantilever. Using free-body diagrams for the cases of nanoindentation and nanoscratch testing, the AFM force curves were analyzed to determine the plowing friction during nanoscratch testing. From the results of this analysis, the plowing friction was found to be proportional to the applied contact force, and the coefficient of plowing friction was measured to be 0.56 ± 0.02. Also, by the combination of nanoscratch and nanoindentation testing, the energetic wear rate of the polycarbonate thin film was measured to be 0.94 ± 0.05 mm3/(N m).
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Shevchenko, A. Yu, A. Yu Popov, I. N. Drozdov, D. A. Blokhin, A. G. Kisel, and E. V. Nekrylov. "Investigation of Cutting Forces for Thin Layers when Planing and Milling." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 4 (139) (December 2021): 66–79. http://dx.doi.org/10.18698/0236-3941-2021-4-66-79.
Повний текст джерелаАнотація:
The problem of machining structural elements with removal of metal layers with thickness less than 0.01 mm by carbide tools, when the conditional radius of the blade rounding is less than or equal to the thickness of the cut layer, is considered. These cutting conditions can be considered constricted which requires research into cutting forces and chip shape. The problem of recording and measuring small cutting forces arising during blade machining of small grooves that serve for gas drainage in the manufacture of rubber products is solved. To measure forces, a lever fixed in a universal dynamometer, which has a supporting support with small friction, is used. Value of force moment measured with dynamometer can be used for optimization of cutting conditions, selection of tool geometry when processing small relief elements. Dependences of lever system cutting forces and displacements on the use of lubricant-cooling liquids, values of front angles during planing and milling with small-size tools are investigated. Experimental discrepancies between theoretical calculations of cutting forces according to classical and modern reference data and fixed results with the use of cutting liquids during cutting with small values of feed for carbide tools are found
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Aramaki, Hirotoshi, Yoshio Shoda, Yuka Morishita, and Takeshi Sawamoto. "The Performance of Ball Bearings With Silicon Nitride Ceramic Balls in High Speed Spindles for Machine Tools." Journal of Tribology 110, no. 4 (October 1, 1988): 693–98. http://dx.doi.org/10.1115/1.3261715.
Повний текст джерелаАнотація:
Two types of angular contact ball bearings for machine tools having steel rings and silicon nitride balls were tested and the temperature rise was compared with that of conventional steel ball bearings with grease lubrication and oil-air lubrication as well. Experimental results indicated that the temperature rise of silicon nitride ball bearings was much lower than that of steel ball bearings at high speeds. Calculations made using a computer demonstrated that the reduction of gyroscopic moments and centrifugal forces acting on balls because of the low density of silicon nitride resulted in about 30 to 50 percent less frictional loss at high speeds even with low-cost lubrication such as grease or oil-air.