Wyniki wyszukiwania - BazTech

1

Investigation of gas foil bearings with an adaptive and non-linear structure

Żywica Grzegorz, Bagiński Paweł

Acta Mechanica et Automatica

|

2019

|

Vol. 13, no. 1

5--10

EN

The article discusses the results of simulation-based and experimental research carried out on gas foil bearings. Owing to the use of a set of flexible thin foils in such bearings, they exhibit certain beneficial features that cannot be found in other types of bearings. They have nonlinear operational characteristics and allow the dissipation of excess energy, thus reducing the vibration level. Moreover, gas foil bearings can self-adapt themselves to the current operating conditions by changing the shape of the lubrication gap. Therefore, they can be used to improve the dynamic performance of rotors, in particular, those operating at very high rotational speeds. This article explains the mechanisms for changes of stiffness and vibration damping in compliant components of a foil bearing. The results of the analysis of the bearing’s subassemblies using advanced numerical models are presented. They are followed by conclusions that were drawn not only from these results but also from the results of the experimental research. It has been proven that the rotor supported on carefully designed foil bearings is capable of maintaining a low vibration level, even if it operates at a high rotational speed.

2

Computer aided adaptive system design with engineering systematics and manufacturing

İrsel G.

Advances in Science and Technology. Research Journal

|

2017

|

Vol. 11, no 4

83--96

EN

This research practically discusses and presents the stages of design process in product development. Design process was realized through CATIA. The product developed is an agricultural device called as “disc harrow”. Therefore, agricultural details are presented together with machine design. A roller system is added to disc harrow in this study. Thus; the current system and the additional roller system are discussed with the principles of methodological construction and design objectives are defined. Both the current system and the additional roller system are designed in parallel with these objectives. Structural stress analysis is performed at different kinetic positions of the disc harrow connection of the roller system. System design is achieved by considering the feedback from such analyses and design objectives. The hereby design is obtained. The additional roller system is mounted and field survey is carried out. Contribution of the roller to disc harrow process, defined design objectives, ratio of the realization of design objectives and results of stress analyses are evaluated.

3

Experimental analysis of a machining system with adaptive dynamic stiffness

Frangoudis C., Nicolescu C. M., Rashid A.

Journal of Machine Engineering

|

2013

|

Vol. 13, No. 1

49--63

EN

A main consideration in the operation of machine tools is vibrations occurring during the cutting process. Whether they are forced vibrations or self-excited ones, they have pronounced effects on surface quality, tool life and material removal rate. This work is an experimental study of interactions between natural characteristics, control parameters and process parameters of a machining system designed with adaptive dynamic stiffness. In order to comprehend these interactions, the effect of changes in dynamic stiffness on the system's response is examined. The system under study consists of an end-milling tool, a steel workpiece and a work holding device with controllable stiffness. Natural dynamic characteristics of the system components are determined through modal impact testing. Then the behaviour of the whole machining system is examined under both high and low cutting speed conditions by analysing vibration levels using acceleration signals acquired through a tri-axial sensor mounted on the workpiece. Cutting is performed in both directions of the horizontal plane of a CNC milling machine. In both cases the results are presented for two extremes of stiffness and damping in the work holding device. The effect of control parameters on the system's natural characteristics could be identified together with a relation between these parameters and the system's response in high and low cutting speed conditions. The high-damping configuration reduces the vibration amplitudes significantly, while the increase of pre-stress has a different effect depending on the cutting conditions.