No abstract

The purpose of a damper, or so-called 'shock absorber', is to introduce controlled friction into the suspension system and dissipate the incoming-to-vehicle energy due to external excitations, in order to give dynamic stability to the vehicle. As damping of the incoming-to-vehicle energy is crucial for road handling and passengers comfort and safety, proper shock absorber operation plays α critical role in the proper and safe vehicle operation .In shock absorber operation, it is possible to identify three distinct types of friction: dry solid friction; fluid viscous friction; fluid dynamic friction. In this work, a common twin-tube shock absorber of a typical passenger car was investigated. The shock absorber had operated for about 150000 kilometres in normal every-day drive conditions. In order to investigate the impact of the worn mechanical parts separately from the quality of the hydraulic oil, numerous tests were run for all three conditions of the specific shock absorber: in the state it was delivered (used), after replacing all mechanical parts, and finally after replacing the hydraulic oil. The results were discussed assuming the manufacturer's standards and also comparatively between the three shock absorber refurnishing conditions.

In mechanical engineering design it is common for multiple stress concentration areas to coexist adjacently, where the existing analytical theory cannot be used to assess the effect. The effect of adjacent step and keyway on a DIN CK 45 shaft has been investigated in the present paper. For this purpose, a DIN CK45 steel shaft specimen with a standardized keyway and a diameter-step has been tested under rotating bending in order to investigate the interaction of two distinct stress concentration areas. All fragment specimens have metallographically examined. Analytical and numerical methods have been used to support the conclusions.

Purpose of this study is the study of loading and contact problems encountered at rotating machine elements and especially at tooth gears. Tooth gears are some of the most commonly used mechanical components for rotary motion and power transmission. This fact proves the necessity for improved reliability and enhanced service life, which requires precise and clear knowledge of the stress field at gear tooth. This study investigates three different study cases of the stresses occurring during the single tooth meshing, regarding the gear module, power rating and number of teeth as variable parameters. Using finite elements analysis, the stresses and deflections on discrete points of contact are derived. Finally from the finite elements analysis results calculated the peripherical bending stiffness of the loaded tooth. From FEM analysis and analytical calculation the magnitudes of root stresses, contact displacement and peripherical bending stiffness, during the single tooth contact, are presented with graphs versus the height of the contact to the total tooth height ratio. During the single tooth contact the values of the Equivalent and 1st principal stress at the addendum of the tooth, the bending deflection and the peripherical bending stiffness at the point of contact are proportional to the height of the contact in respect of the total tooth height.