Wyniki wyszukiwania - Biblioteka Nauki

1

Discrete Traffic Flow

100%

Ostermeyer G. P.

Machine Dynamics Problems

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2004

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tom Vol. 28, No. 2

23-36

EN

Traffic flow is described usually on macro, meso or micro scales. This paper deals with a micro scale description of traffic, where some streets with at least two discrete cars are taken into account. The necessarily of traffic flow management is accepted but often there is to be seen a large gap between the controlled flows in mathematical models and reality. Main reason for this seems to be the effect of self organization in traffic flow. Nearly every control management system model is based on the interaction with drivers only. But the traffic flow is not only the sum of drivers. So self organization effects have to be understand and taken into account. This investigations starts rather long ago in macro traffic models, where car densities are described on street networks. In discrete car model systems these investigations just starts. One result is for instance the introduction of roundabout traffic. Actual questions of interest in such a discrete car traffic system are driver models with individual behavior able to drive cars in complex traffic flows in such a way, that self organization effects are generated by the complex interaction of the drivers. Here a model of driver interaction is presented and illustrated by an experimental realization of micro traffic flow in an down scaled world, where miniature cars in hardware are driven by radio control.

2

Modeling Heat and Pain in Multibody Systems

63%

Ostermeyer G. P. , Neumann M.

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tom Vol. 29, No. 4

127-138

EN

Within the classical dynamics of multi body systems physical effects in boundary layers of contacting bodies can be fundamental. Examples are impact motion or frictional contact. Usually the dynamics in boundary layers is given on other time and length scales than the dynamics of the system itself. This paper deals with a mesoscopic particle discretisation of such contact zones or surfaces. These particles have hidden degrees of freedom from macroscopic point of view, which are separated only on a microscale. To be correct within the thermodynamic properties we have to use different time and length scale dynamics in these particle systems. One single particle for instance could be used as sensor giving a rough measure of pain in multibody systems (MBS). This is of interest in human like models with sportive dynamics or even in walking machines, where the dynamics of ground contact have to be evaluated with respect to human walking behaviour. This measure of pain grows up, when the impacts are repeated in short times and is lowered when there are no hurting motions. So this measure of pain is rather similar to the physical quantity of heat, which is generated by impacts and lowered by convection, radiation or conductional effects. In frictional contact this particle discretisation can be used for detecting the heat generation and even wear properties. The research on frictional effects in boundary layers of contacting bodies was the root of developing the mesoscopic particle method (Ostermeyer, 1996 and 1999).

3

Advances in Fundamental Studies on Partially Filled Tribological Gaps

63%

Mueller M. , Ostermeyer G. P.

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tom Vol. 42, No. 3

5--15

EN

Tribological scenarios with partially ﬁlled gaps can occur when either a lubricated system runs under starved lubrication or a system that usually operates under dry conditions is wetted by a ﬂuid. In order to get a detailed insight into the tribological character of partially ﬁlled gaps, it is necessary to investigate the dynamics of the ﬂuid ﬂow and its interaction with the pressure, velocity, nominal gap height and deformations. Within this problem, the total amount of ﬂuid in the gap plays a crucial role. Recent studies with novel models have shown that particularly near the fully ﬁlled regime the built up pressure is highly dependent on the ﬁlling ratio. Further studies proved that the ﬂuid forms characteristic bow waves in front of asperities thus leading to larger mean pressure values in the contact. This paper extends these ﬁndings by experimental investigations on different length scales. Special focus is on the correlation between the friction coefﬁcient and the supplied ﬂuid volume.

4

The Effect of Non-Fully Filled Gaps in Elastic Tribological Contacts

51%

Mueller M. , Voelpel A. , Ostermeyer G. P.

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tom Vol. 39, No. 4

107-115

EN

In recent papers, the authors of this paper investigated the dynamic behavior in partially fluid-filled tribological gaps with a novel modeling technique. The impact of the fluid amount towards the buildup of hydrodynamic pressures has been demonstrated. It shows high nonlinearities with respect to the correlation of the filling ratio and the mean pressure, in particular near the fully filled regime. So far, this modeling technique neglected deformations caused by the pressures in the gap. This paper is focused on fundamental studies on the impact of elastic deformations in combination with varying filling ratios onto the pressure characteristic. The studies are performed using an example of two ellipsoidal bodies moving relative to one another. The size of the ellipsoids is varied which allows modifying the gap topography. In this paper, the essential effect of elastic deformations at very small gaps is shown. It is discussed that it is very complex to formulate a general rule about parameter sets that give the possibility to neglect elastic deformations.