Name: friction moment in journal bearings
Uploaded: 2023-09-22T11:49:30.000Z
Duration: 1 min 23 s
Channel: JoVE

Łożyska ślizgowe służą do zapewnienia stabilności bocznej obracających się wałów i osi.
Rozważ wciągarkę linową z suchymi lub częściowo nasmarowanymi łożyskami ślizgowymi.
Obrót szpuli zgodnie z ruchem wskazówek zegara powoduje, że wał zwija się po wewnętrznej powierzchni łożyska, aż do poślizgu i stabilnego obrotu.
Rysowany jest schemat wału z dowolnym korpusem. Siły działające na układ obejmują ciężar wału, sprzęg zgodny z ruchem wskazówek zegara oraz siłę reakcji łożyska.
Niewspółliniowa siła reakcji jest równa i przeciwna do ciężaru i działa pod kątem względem normalnej powierzchni. Kąt ten nazywany jest kątem tarcia kinetycznego.
Linia działania siły reakcji jest zawsze styczna do okręgu tarcia.
Warunek równowagi momentu wokół punktu O daje moment wału.
W przypadku małego kąta tarcia kinetycznego składnik sinusoidalny można przybliżyć do stycznej kąta tarcia kinetycznego.
Ponieważ tangens kąta tarcia kinetycznego jest równy współczynnikowi tarcia kinetycznego, uzyskuje się moment wymagany do pokonania oporu tarcia łożyska.

<ol>
	<li>Hibbeler, R.C. (2016). Mechanika inżynierska \u2012 Statyka i dynamika. Hoboken, New Jersey: Pearson Prentice Hall. Str. 450.</li>
	<li>Meriam, J.L.; Kraige, L.G. i Bolton, J.N. (2020). Mechanika inżynierska \u2012 Statyka. Hoboken, New Jersey: John Wiley. Strona 364.</li>
	<li>Piwo, F.P.; Johnston, E.R.; Mazurek, D.F.; Cromwell, PJ i Self, BP (2019). Mechanika wektorowa dla inżynierów \u2012 Statyka i dynamika. Nowy Jork: McGraw-Hill. Strony 459-460.</li>
</ol>

Łożyska ślizgowe

Journal Bearings

Łożyska ślizgowe są mechanicznymi komponentami, które podtrzymują i zapewniają stabilność boczną dla obracających się wałów i osi. Są one niezbędne do redukcji tarcia, zużycia oraz wibracji w maszynach takich jak silniki, turbiny i pompy. Zasada działania tych łożysk polega na utworzeniu cienkiej warstwy smaru pomiędzy powierzchnią łożyska a obracającym się wałem, co minimalizuje bezpośredni kontakt i zmniejsza siły tarcia.

Aby lepiej zrozumieć koncepcję łożysk ślizgowych, rozważmy wciąg linowy z suchymi lub częściowo smarowanymi łożyskami ślizgowymi, które podtrzymują obracający się wał. Gdy szpula obraca się zgodnie z ruchem wskazówek zegara, wał przesuwa się w górę wewnętrznej powierzchni łożyska, dopóki nie zacznie ślizgać się i utrzymuje stabilną rotację.

<img alt="Figure 1" src="/files/ftp_upload/14326/14326_Figure_1v2.svg" style="text-align: center; height: 300px;" />

Możemy narysować diagram swobodnego ciała wału, aby przeanalizować siły działające na system. Siły te obejmują wagę wału, działającą pionowo w dół, moment obrotowy, reprezentujący moment siłowy działający na wał oraz siłę reakcji wywieraną przez łożysko na wał. Siła reakcji, nieliniowa, jest równa i przeciwna wobec wagi wału i działa pod kątem względem normalnej powierzchni. Ten kąt nazywamy kątem kinetycznego tarcia. Linia działania siły reakcji zawsze jest styczna do okręgu tarcia, który przedstawia zbiór wszystkich możliwych punktów kontaktu między wałem a łożyskiem. Poprzez zastosowanie warunku równowagi momentu w punkcie O (środek wału), możemy określić moment wału potrzebny do utrzymania stabilnej rotacji.

<img alt="Equation 1" src="/files/ftp_upload/14326/14326_Equation_1v2.svg" style="text-align: center; height: 13px;" />

Termin sinus w równaniu można przybliżyć do tangensa kąta kinetycznego tarcia dla małego kąta kinetycznego tarcia.

<img alt="Equation 2" src="/files/ftp_upload/14326/14326_Equation_2v2.svg" style="text-align: center; height: 13px;" />

Ponieważ tangens kąta kinetycznego tarcia równa się współczynnika kinetycznego tarcia, możemy obliczyć moment wymagany do pokonania oporu tarcia łożyska. Jest to istotny czynnik w określaniu efektywności i wydajności systemu.

<img alt="Equation 3" src="/files/ftp_upload/14326/14326_Equation_3v2.svg" style="text-align: center; height: 13px;" />

Łożyska ślizgowe to elementy mechaniczne, które wspierają i zapewniają stabilność boczną obracających się wałów i osi. Mają kluczowe znaczenie w zmniejszaniu tarcia, ...

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JoVE Core

Mechanical Engineering

Inżynieria mechaniczna

Unit 1

Jednostka 1

Friction

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KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

friction moment in journal bearings

Journal bearings support rotating shafts and axles while helping keep them stable. They are used in machines such as engines, turbines, and pumps. Their job is to reduce friction, wear, and vibration.

A journal bearing works by keeping a thin film of lubricant between the bearing surface and the rotating shaft. This film limits direct contact and lowers frictional force. The video uses a rope winch with dry or only partly lubricated journal bearings to show the idea.

As the spool turns clockwise, the shaft first rolls up the inner surface of the bearing. It then slips and settles into stable rotation. A free-body diagram of the shaft helps show the forces in the system.

The diagram includes the weight of the shaft, a clockwise couple that represents the applied torque, and the reaction force from the bearing. The reaction force is not collinear with the weight of the shaft. It acts at an angle to the surface normal, and that angle is called the angle of kinetic friction.

The line of action of the reaction force is tangent to the circle of friction. The circle of friction is the set of possible contact points between the shaft and the bearing. By using moment equilibrium about point O, the center of the shaft, the needed shaft moment can be found.

For a small kinetic friction angle, the sine term in the equation can be approximated by the tangent of that angle. Since the tangent of the kinetic friction angle equals the coefficient of kinetic friction, the required moment can be calculated from it. This moment helps describe the bearing’s frictional resistance and its effect on efficiency and performance.

Friction Moment in Journal Bearings

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Journal bearings support rotating shafts and axles while helping keep them stable. They are used in machines such as engines, turbines, and pumps. Their job is to reduce friction, wear, and vibration. A journal bearing works by keeping a thin film of lubricant between the bearing surface and the rotating shaft. This film limits direct contact and lowers frictional force. The video uses a rope winch with dry or only partly lubricated journal bearings to show the idea. As the spool turns...

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key terms and concepts

Learn how journal bearings support rotating shafts, reduce friction, and create the reaction force and moment used to analyze stable rotation.

Friction Moment in Journal Bearings | JoVE K12

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Friction Moment in Journal Bearings

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