Wyniki wyszukiwania - BazTech

1

Controlled turning process for the production of friction-reduced cylinder liners with a defined free-form geometry

Denkena Berend, Bergmann Benjamin, Handrup Miriam, Schmidt Christopher

Journal of Machine Engineering

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2021

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Vol. 21, No. 3

47--59

EN

Friction in the piston-cylinder system of combustion engines has a great influence on fuel consumption. To reduce the friction of combustion engines, free-form cylinder liners and microstructured cylinder liners have proven to be advantageous. However, the combination of both processes is not industrially realized today because of an increased manufacturing effort due to a higher number of process steps. To save resources in form of honing oil in the production, the free-form can be machined by a dry turning process instead of form honing. A combination with the microstructuring process in a single manufacturing step would furthermore reduce non-productive time. This paper presents a piezo-actuated hybrid tool that can carry out both processes. The tool wear and the behavior during free-form fine machining of cylinder liners are investigated. A process control system is introduced that controls the cylinder liner geometry by adapting the process parameters during free-form turning.

2

Influence of surface texture parameters on friction characteristics under starved lubrication

Wu Shen, Zhang Pan, Wei Haijun, Chen Lei

Polish Maritime Research

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2020

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nr 2

96--106

EN

A cylinder liner and piston ring running under starved lubrication near the top dead centre (TDC) and bottom dead centre (BDC) cause abnormal friction and wear during operation of a marine diesel engine. The method of laser texturing is proposed to improve the surface friction property under this condition. Spherical crown pits with different parameters were formed on the surface of samples by femtosecond laser processing. The BDC and TDC conditions of oil starvation were simulated in a reciprocating friction and wear experiment, and a numerical model of Surface texture lubrication based on the Reynolds equation was established. The influence of the distribution density, diameter, and depth parameters of the texture on the surface properties was studied. In the BDC condition, compared with the untextured surface, the average coefficient of friction (COF) can be reduced by up to 24% and the average friction force can be reduced by up to 18%. In the TDC condition, the COF can be reduced by up to 19%, and the average friction force can be reduced by up to 18%. Therefore, the textures with various parameters should be arranged in different positions on the cylinder liner; more attention should be paid to the optimisation of diameter in the texture of the cylinder liner near the BDC, whereas more attention should be paid to the optimisation of distribution density in the texture of the cylinder liner near the TDC

3

Hard and superhard nanolaminate and nanocomposite coatings for machine elements based on Ti6Al4V alloy

Wendler B., Moskalewicz T., Progalskiy I., Pawlak W., Makówka M., Włodarczyk K., Nolbrzak P., Czyrska-Filemonowicz A., Rylski A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

455--462

EN

Purpose: Verification of a series of hybrid treatments of Ti6Al4V alloy consisting of primary diffusion hardening of the substrate with subsequent deposition of wear resistant coatings. Design/methodology/approach: Different nanolaminate and nanocomposite coatings were deposited with use of four different methods including a newly developed high density gas pulsed plasma MS technique. After deposition the coatings were investigated using OM, SEM, HRTEM, XRD, XPS, nanoindentation, Daimler-Benz, ball-on-plate and scratch tests. Findings: Besides an important increase of Ti6Al4V alloy hardness much greater further increase of hardness was obtained due to coatings deposition up to 53 GPa in case of a nanolaminate coating and to 47 GPa in case of a nanocomposite nc-TiN/a-SiN coating. At the same time the volume wear coefficient decreases several orders of magnitude for all the coatings. Simultaneously the friction coefficient decreased to a great extent except for the nc-TiN/a-SiN coating. Research limitations/implications: High density gas pulsed plasma magnetron sputtering is an effective method for superhard coatings deposition, however the roughness of the deposited nc-TiN/a-SiN coating was greater than after conventional magnetron sputtering. This finding needs further experimental and theoretical investigation. Practical implications: Greater surface roughness and high resistance to wear of the coatings synthesized using the newly developed gas pulsed plasma magnetron sputtering deposition limits their application to wear protection of cutting tools rather than for friction reduction in tribological couples. Originality/value: Applicability of the broad spectrum of nanolaminate and nanocomposite coatings as well as different CVD and PVD techniques for an improvement of tribological properties of Ti6Al4V alloy was analyzed in the paper including a newly developed original high density gas pulsed plasma magnetron sputtering technique.

4

Reaction mechanisms of alcohols on aluminum surfaces

Wiltord F., Martin J., Le Mogne T., Jarnias F., Querry M., Vergne P.

Tribologia

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2006

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nr 6

7-20

EN

The general aim of this work concerns the study of the lubricant/surface interaction mechanisms, such as those occurring during aluminum cold rolling in the presence of fatty alcohols. To improve the understanding of alcohol tribochemical reactions on an aluminum surface, friction tests followed by SIMS analyses were conducted. Deuterated alcohols were used to investigate the formation of bonds between the aluminum surface and alcohol molecules. The combination of SIMS analysis and the use of deuterated molecules have enabled us to propose a reaction mechanism between alcohols and the initial oxidized aluminum surface. This mechanism later affects the tribological behavior of the interface. In agreement with previous observations, we showed that a low steric size increases the number of acting molecules on the oxidized surface and that the alkyl chain length is of importance to protect the surface and hence reduce friction. These two key points can be easily explained by the proposed reaction pathway.

PL

Celem niniejszej pracy było zbadanie mechanizmów oddziaływań układu środek smarowy/powierzchnia, które między innymi mają miejsce podczas walcowania na zimno aluminium w obecności alkoholi tłuszczowych. Produkty tribochemicznych reakcji alkoholi, zachodzące na powierzchni aluminium, badano za pomocą spektrometrii masowej jonów wtórnych (SIMS). Aby zbadać tworzenie się wiązań pomiędzy powierzchnią aluminiową a cząsteczkami alkoholu, zastosowano deuterowane alkohole. Połączenie techniki SIMS oraz deuterowanych cząsteczek pozwoliło zaproponować mechanizm reakcji alkoholi i utlenionej powierzchni aluminium. Mechanizm ten wyjaśnia wpływ alkoholi na tribologiczne zachowanie się warstw wierzchnich współpracujących elementów. Zgodnie z poczynionymi wcześniej obserwacjami wykazano, że mniejszy rozmiar przeszkody sterycznej zwiększa liczbę oddziałujących cząsteczek z utlenioną powierzchnią, a także, że długość łańcucha alkilowego pełni istotną rolę w ochronie powierzchni i tym samym redukcji tarcia. Te dwa kluczowe aspekty można łatwo wytłumaczyć za pomocą zaproponowanych procesów tribochemicznych.

5

Influence of normal micro-vibrations in contact on sliding motion of solid body

Grudziński K., Kostek R.

Journal of Theoretical and Applied Mechanics

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2005

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Vol. 43 nr 1

37--49

EN

The paper shows results of some simulation studies on: (i) normal contact micro-vibrations in a simple model of a friction system and (ii) the influence of such vibrations upon reduction of friction forces in the system. A model of friction contact with two degrees of freedom is adopted, considering non-linear normal contact flexibility of rough surfaces acting on each other. The mechanisms which cause the reduction of the friction force are investigated and described. It is proved that the main cause of the decrease of the friction force, if normal contact micro-vibrations are present, is due to certain dynamic processes taking place within the contact region. This decrease is not due to lower values of the friction coefficient, nor lower mean values of the normal reaction and real contact area, as it is often quoted in many publications.

PL

W artykule przedstawiono wyniki symulacyjnych badań mikrodrgań w kierunku normalnym w kontakcie ciał stałych o powierzchniach chropowatych oraz ich wpływu na redukcję siły tarcia. Przyjęto model o dwóch stopniach swobody, uwzględniający nieliniową podatność kontaktową normalną oddziaływujących na siebie powierzchni. Zbadano i opisano mechanizm powodujący zmniejszenie oporu tarcia w kontakcie, w przypadku występowania w nim drgań normalnych. Wykazano, że główną przyczyną redukcji oporu tarcia w takim przypadku są pewne procesy dynamiczne występujące w kontakcie, a nie spadki wartości współczynnika tarcia, ani też średniej wartości reakcji normalnej, jak to się podaje w wielu publikacjach.