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Dynamics of Rolling Wheels

Nackenhorst U., Brinkmeier M., Ziefle M.

Machine Dynamics Problems

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2006

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Vol. 30, No. 1

45-60

EN

A finite element approach for the simulation of rolling tire dynamics is presented. As a key for the efficient numerical solution an arbitrary Lagrangian Eulerian kinematics description is introduced. After a short introduction into the general theory one focus is laid onto the computation of stationary rolling contact. Here a novel approach for the treatment of inelastic material properties by a discontinuous Galerkin discretization of the advection problem is presented. In the continuation the analysis of transient dynamic aspects with emphasis to rolling noise prediction is discussed. A modal superposition approach is suggested, where special attention is laid onto the numerical solution of the related non-symmetric and complex valued eigenproblems for the gyroscopic system. Numerical examples on detailed tire-models demonstrate the applicability of the presented theory.

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Visual Costs of the Inhomogeneity of Luminance and Contrast by Viewing LCD-TFT Screens Off-Axis

Ziefle M., Groeger T., Sommer D.

International Journal of Occupational Safety and Ergonomics

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2003

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Vol. 9, No. 4

515--525

EN

In this study the anisotropic of TFT-LCD (Thin-Film-Transistor-Liquid Crystal Display) screens were examined. Anisotropy occurs as the distribution of luminance and contrast changes over the screen surface due to different viewing angles. On the basis of detailed photometric measurements the detection performance in a visual reaction task was measured in different viewing conditions. Viewing angle (0°, front al view; 30°, off-axis; 50°, off-axis) as well as ambient lighting (a dark of illuminated room) were varied. Reaction times and accuracy of detection performance were recorded. Results showed TFT’s anisotropy to be a crucial factor deteriorating performance. With an increasing viewing angle performance decreased. It is concluded that TFT’s anisotropy is a limiting factor for overall suitability and usefulness of this new display technology.

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Sitting Posture, Postural Discomfort, and Visual Performance: A Critical View on the Interdependence of Cognitive and Anthropometric Factors in the VDU Workplace

Ziefle M.

International Journal of Occupational Safety and Ergonomics

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2003

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Vol. 9, No. 4

503--514

EN

The study focuses on individual and standard visual display unit (VDU) workplaces with respect to performance and muscular load. Three different work settings were realized: The workplace was either adjusted to individual preferences or to the European standard. The third condition mirrored exactly the individual setting, however participants were told that it was set according to another standard. Dependent variables were visual performance in a search task, the rated muscular load, and individual preferences. Results show that both individual work settings yielded a superior performance as compared to the standard. However, performance and muscular comfort improved when participants knew they had adjusted the workplace. Apparently, VDU users follow a intuitive rationale adjusting their work setting minimizing muscular load and optimizing performance.