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Advantages of using composite alloys for internal combustion engine pistons

Kowalski Mirosław, Jankowski Antoni

Archives of Transport

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2020

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Vol. 55, iss. 3

85--94

EN

Combustion engine pistons are subject to variable mechanical and thermal loads, and to variable deformations. The article presents the possibilities of using novel composite alloys for the construction of pistons for combustion engines. The novel alloys make it possible to meet high demands, especially for highly load designs, which practically cannot be met by conventional alloys used so far. These high requirements relate to the weight of the pistons, high temperature strength, alloy crystalline structure, abrasive wear resistance, dimensional stability. The requirements for pistons have an impact on the durability of the engine's operation, the level of noise emissions; exhaust gas blow-by into the crankcase, the level of emitted toxic exhaust components, mainly hydrocarbons. The research covered metallography (chemical composition, microstructure), material strength, abrasive wear, and thermal expansion. Investigations of the alloy crystallization process during casting were carried out using the Differential Thermal Analysis (DTA) method. The castings were used for metallographic tests. The strength of the samples was tested at room temperature (20°C) and elevated temperature (up to 350°C) on a testing machine equipped with a special climatic chamber. In particular, the article presents Thermal Derivative Analysis curves and representative microstructures of conventional AlSi12 alloy and the novel composite alloy; dependence of the tensile strength versus temperature for the samples of the novel alloy with various nickel content 2% and 4 %; comparison of the tensile strength for conventional alloy and the novel alloy at ambient and 250°C temperature; comparison of abrasive wear of samples, made of novel aluminium alloy and different cast iron; course of the linear expansion coefficient versus temperature for the conventional AlSi12 alloy with incorrect heat treatment; course of the linear expansion coefficient versus temperature for one of tested silumin alloy which expansion coefficient during sample cooling is smaller than during sample heating; course of the linear expansion coefficient versus temperature for the novel composite silumin alloy, after correct heat treatment. The great benefits of using this novel alloy and the introduction of novel alloying elements (in-Situ) have been confirmed in engine research.

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Wavelet transform in vibroacoustic diagnostic of machines

Haller Piotr, Jankowski Antoni, Kaźmierczak Andrzej, Wróbel Radosław

Journal of KONES

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2019

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Vol. 26, No. 1

47--55

EN

This article discusses the use of wavelet decomposition in the diagnostics of vibrometric signals of an engine. Apart from presenting the possibility of using wavelets in diagnostics, the authors take up the subject of the applicability range of processing for stationary signals, which until now has been reserved for non-stationary signals. A unified definition of signal stationarity has been proposed, which is not based on statistics. The authors presented methods of wavelet decomposition of a vibrometric signal of combustion engine vibrations, measured with the use of LDV (Laser Doppler Vibrometry). Laser measurements allows for studying an object without 'touching' its housing. Basing on the relative velocity of engine vibrations, the authors indicate how reliable vibrations are in diagnostics. Despite higher costs, this measurement method gives better results (for specific cases) than acoustic studies. Transform – wavelet decomposition is a solution hardly ever used in machine diagnostics; it is more often applied in medicine and image recognition. The authors presented the differences that can be obtained for different levels of decomposition, and also presented the impact on the engine condition assessment through the use of filtering (windowing) the signal before decomposition.

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Solutions in the vehicle suspension

Niculescu Adrian Ioan, Jankowski Antoni, Kowalski Miroslaw, Sireteanu Tudor

Journal of KONES

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2019

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Vol. 26, No. 4

185--196

EN

The paper presents a review of the suspension solutions used on the street vehicle up to the now a days, finalising with presentation of their damping characteristics and with evaluation of their advantages or disadvantages. Long time the suspension systems have been dominated by the classic passive suspensions realized with metallic springs, shock absorbers with constant damping coefficients and anti-roll bars, excepting some luxury and sport cars using semi-active and active suspensions. There are presented some semi-active suspension solutions with continuous or discontinuous damping characteristics adjustment and the evolution of the Citroen and other active suspensions. All of them improve in some matter the performances but all of them have not ability to recuperate energy and has auxiliary energy consumption so last period the electromagnetically shock absorbers are researched, the paper presenting some of them. The paper also presents magneto rheological MR damper, solutions for adjustable passive shock absorbers and solutions for passive shock absorbers with variable damping coefficient with the stroke, e.g. Monroe Sensa Trac, Citroën Solution and VZN solution, with their damping characteristics and performances.