A representation for planar point contact joints in the multibody mechanical bond graph library

Author(s):  
W Favre ◽  
S Scavarda

In this paper a bond graph representation of the point contact joint between two bodies with any outline curves and in planar motion is proposed. The body geometry and frames are described, the kinematic constraints attached to the point contact joint are identified and the bond graph junction structure is deduced. The example of an elliptic cam-follower is used to illustrate the bond graph representation. In particular this shows the need for the simulation to add strong damping and very stiff elements to the system.

1999 ◽  
Vol 121 (1) ◽  
pp. 128-135 ◽  
Author(s):  
D. Wang ◽  
C. Conti ◽  
D. Beale

A new computer aided analysis method for frictionless impact problems due to interference between two bodies in a constrained multibody system is presented in this paper. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities and rebounds. The interference surfaces can be described by the joint coordinates of the virtual contact joint, which are very useful for determining the impact time, the types and positions of two impact surfaces and impact initial conditions when an interference happens between two bodies.


Author(s):  
Deming Wang ◽  
David Beale

Abstract A new computer aided analysis method for frictionless interference impact problems between two bodies in a constrained multibody system is presented in the paper, which can be used to perform interference analysis and motion design of multibody systems. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities, rebounds and system motion after the interference impact analysis. The interference surfaces can be any geometric element, such as point, line segment, are and circle described by the joint coordinates of the virtual contact joint. The method are very useful to predict and determine the interference time, the types and positions of two impact surfaces. System motion after the interference can be controlled by changing some dynamic parameters in the multibody system.


2019 ◽  
Vol 20 (4) ◽  
pp. 267-275
Author(s):  
Yury N. Razoumny ◽  
Sergei A. Kupreev

The controlled motion of a body in a central gravitational field without mass flow is considered. The possibility of moving the body in the radial direction from the center of attraction due to changes in the kinetic moment relative to the center of mass of the body is shown. A scheme for moving the body using a system of flywheels located in the same plane in near-circular orbits with different heights is proposed. The use of the spin of elementary particles is considered as flywheels. It is proved that using the spin of elementary particles with a Compton wavelength exceeding the distance to the attracting center is energetically more profitable than using the momentum of these particles to move the body. The calculation of motion using hypothetical particles (gravitons) is presented. A hypothesis has been put forward about the radiation of bodies during accelerated motion, which finds indirect confirmation in stellar dynamics and in an experiment with the fall of two bodies in a vacuum. The results can be used in experiments to search for elementary particles with low energy, explain cosmic phenomena and to develop transport objects on new physical principles.


2015 ◽  
Vol 236 ◽  
pp. 26-30 ◽  
Author(s):  
Michał Batsch ◽  
Tadeusz Markowski ◽  
Wojciech Homik

Paper presents the method for obtaining maximum contact pressure of Novikov gears. Described surface strength calculation method is based on Hertz theory of two bodies being in point contact. What’s more the influence of gear position errors on maximum contact stresses has been presented. Also the comparison of Hertz stresses for Novikov and involute gears has been made.


Author(s):  
H. You ◽  
B. Oesterling ◽  
B. Lowe ◽  
B. J. Gilmore ◽  
A. Freivalds

Abstract Bus operator’s workstations neglecting ergonomic features can cause overall discomfort and injuries to the users. This paper presents use of JACK®, a human work simulation package, in designing and evaluating a bus operator workstation which can provide sufficient visibility, natural reach, and comfortable posture for operators who range from the 5th percentile female to the 95th percentile male as defined by SAE J833 (SAE, 1994). Three human models representing the two extremes and their medium size person were created and performed 15 bus operating tasks on the bus workstation implemented in JACK®. Kinematic constraints were defined between the human models and the workstation to simulate the tasks in a realistic manner. While the human models simulated the tasks, the body joints were monitored to determine if they exceeded their comfort ranges recommended by Diffrient et al. (1981) and the workstation was evaluated in terms of visibility, reach, comfort, and adjustability. After the workstation design was refined by iterative modifications and the required component adjustment ranges were determined, the workstation design was prototyped into an actual working bus. A jury of bus operators evaluated the workstation design by operating the prototype on a test track. The response from the operators indicated that the workstation would accommodate the intended population.


2010 ◽  
Vol 79 (3) ◽  
pp. 531-555 ◽  
Author(s):  
Catherine M. Chin

The late ancient body is a historiographical problem. In the combined lights of feminist, Foucaultian, and post-Foucaultian methodologies, much recent scholarship on bodies in late antiquity has focused on bodies as sites on which power relations are enacted and as discourses through which ideologies are materialized. Contemporary concern with definitions and representations of the posthuman, however—for example, in medical technologies that expand the capacities of particular human bodies, in speculative pursuit of the limits of avatars, or in the technological pursuit of artificial intelligence or artificial life—seem both to underline the fundamental lability of the body, and to require a broadening of scholarly focus beyond the traditional visible boundaries of the human organism. At the same time, scholarship on the posthuman emphasizes contemporaneity and futurity to an extent that may seem to preclude engagement with the premodern. I would like to suggest here that doubt about the boundaries of human embodiment is a useful lens through which to reconsider some very traditional questions in the history of Christianity, and that we may begin to think of bodies in Christian premodernity in terms of what we might call their pre-humanity, that is, as fundamentally open to extension, transformation, and multiple instantiation. The figure on whom I focus is Ambrose, the fourth-century bishop of Milan, who, I argue, defined his own body in such a way that he was able to instantiate physically in dozens of living human bodies, at least two dead human bodies, thousands of angelic bodies, and four church buildings. Ambrose's dynamic conception of his episcopal body was formed within a complex political and theological situation, so questions concerning the political ideology of bodies remain very much at issue. I add to these questions a concern for premodern uncertainty about how to recognize a body, both when it is visible and, perhaps more importantly, when it is not.


Author(s):  
Mohammad J. Izadi

A CFD study of a 3 Dimensional flow field around two bodies (Two Canopies of a Parachutes) as two bluff bodies in an incompressible fluid (Air) is modeled here. Formations of these two bodies are top-to-top (One on the top of the other) with respect to the center of each other. One canopy with a constant cross sectional area with a vent of air at its apex, and the other with a variable cross sectional area with no vent is studied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple radius of the body with a vent on it. The flow condition is considered to be 3-D, unsteady, turbulent, and incompressible. The vertical distances between the bluff bodies, cross sectional area, and also vent ratio of bluff bodies are varied here. The drag forces with static pressures around the two bodies are calculated. From the numerical results, it can be seen that, the drag coefficient is constant on the range of zero to twenty percent of the vent ratio and it decreases for higher vent ratios for when the upper parachute is smaller than the lower one, and it increases for when the upper parachute is larger than the lower one. Both Steady and Unsteady cases gave similar results especially when the distance between the canopies is increased.


Author(s):  
Cody Leeheng Chan ◽  
Kwun-Lon Ting

Abstract According to Camus’ theorem, for a single DOF 3-body system with the three instant centers staying coincident, a point embedded on a body traces a pair of conjugated curves on the other two bodies. This paper discusses a fundamental issue not addressed in Camus’ theorem in the context of higher order curvature theory. Following the Aronhold-Kennedy theorem, in a single degree-of-freedom three-body system, the three instant centers must lie on a straight line. This paper proposes that if the line of the three instant centers is stationary (i.e. slide along itself), on the line of the instant centers a point embedded on a body traces a pair of conjugated curves on the other two bodies. Another case is that if the line of the three instant centers rotate about a stationary point, the stationary point embedded on the body also traces a pair of conjugated curves on the other two bodies. The paper demonstrates the use of instantaneous invariants to synthesize such a three-body system leading to a conjugate curve-pair generation. It is a supplement or extension of the Camus’ theorem. The Camus’ theorem may be regarded as a special singular case, in which all three instant centers are coincident.


Author(s):  
Maria Terushkin ◽  
Offer Shai

This paper introduces a novel way to augment the knowledge and methods of rigidity theory to the topological decomposition and synthesis of gear train systems. A graph of gear trains, widely reported in the literature of machine theory, is treated as a graph representation from rigidity theory—the Body-Bar graph. Once we have this Body-Bar graph, methods and theorems from rigidity theory can be employed for analysis and synthesis. In this paper we employ the pebble-game algorithm, a computational method which allows determination of the topological mobility of mechanisms and the decomposition of gear trains into basic building blocks—Body-Bar Assur Graphs. Once we gain the ability to decompose any gear train into standalone components (Body-Bar Assur Graphs), this paper suggests inverting the process and applying the same method for synthesis. Relying on rigidity theory operations (Body-Bar extension, in this case), it is possible to construct all of the Body-Bar Assur Graphs, meaning the building blocks of gear trains. Once we have these building blocks at hand, it is possible to recombine them in various ways, providing us with a topological synthesis method for constructing gear trains. This paper also introduces a transformation between the Body-Bar graph and other graph representations used in mechanisms, thus leaving room for the application of the proposed synthesis and decomposition method directly to known graph representations already used in machine theory.


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