Name: square-thread screw mechanics and friction
Uploaded: 2023-09-22T11:49:29.000Z
Duration: 1 min 17 s
Channel: JoVE

Większość charakteryzuje się spiralnym grzbietem i jest powszechnie stosowana jako elementy złączne; z gwintem kwadratowym są często stosowane w maszynach do przenoszenia mocy lub ruchu między częściami.
Weźmy pod uwagę podnośnik ze śrubą z gwintem kwadratowym przenoszącą ładunek. Po przyłożeniu siły do uchwytu śruba obraca się, a ładunek jest podnoszony.
można uznać za cylindryczny wał z nachylonym kwadratowym grzbietem owiniętym na nim.
Odległość między grzbietami dwóch sąsiednich gwintów to skok, a odległość, na jaką śruba się do przodu w jednym obrocie, jest znana jako jej skok.
Gdy nić zostanie odwinięta przez jeden obrót, przypomina nachyloną rampę pod kątem. Kąt nachylenia gwintu nazywany jest kątem przystawienia i jest wyrażony w postaci średniego promienia gwintu i skoku.
Ponieważ siła tarcia między powierzchniami jest niezależna od obszaru styku, śruba jest reprezentowana jako blok nad gwintem podnośnika.
Kąt między siłą reakcji a normalną do gwintu to kąt tarcia.

<ol>
	<li>Hibbeler, R.C. (2016). Mechanika inżynierska: Statyka. Czternasta edycja, New Jersey: Pearson. Strony 432.</li>
	<li>Meriam, J.L., Kraige, L.G. i Bolten, J.N. (2016). Mechanika inżynierska: statyka i dynamika. Ósma edycja, Singapur: John Wiley & Sons. Strony 354-355.</li>
	<li>Beer, F.P., Johnston, E.R., Mazurek, D.F., Cornwell, P.J. i Self, B.P. (2016). Mechanika wektorowa dla inżynierów. Jedenasta edycja, Nowy Jork: McGraw-Hill Education. Strony 450-451.</li>
</ol>

działanie tarcia na śruby

Frictional Forces on Screws

Śruby charakteryzują się spiralnym grzbietem znany jako gwint owinięty wokół cylindrycznego wałka. Są one powszechnie stosowane jako elementy mocujące do trzymania ze sobą obiektów lub do przekazywania energii i ruchu w maszynach. Jednym rodzajem śruby, który jest szczególnie przydatny do przesyłania energii, jest śruba z gwintem kwadratowym.

Podpórka z kwadratowym gwintem to urządzenie mechaniczne używane do podnoszenia ciężkich ładunków poprzez zastosowanie siły na jej uchwyt. Gdy jest stosowana siła, śruba obraca się, podnosząc ładunek. Śruba może być traktowana jako cylindryczny wałek z nachyloną kwadratową granią lub gwintem owiniętym wokół niej. Ten gwint ma specyficzne cechy, które określają jej funkcjonalność.

Odległość między dwoma sąsiednimi gwintami na śrubie nazywa się skokiem. To pomiar jest krytyczny, ponieważ to on określa, jak blisko są do siebie zapakowane gwinty. Inną istotną cechą śruby jest jej prowadzenie, które odnosi się do odległości, na jaką śruba posuwa się podczas jednego pełnego obrotu.

Gdy gwint śruby zostanie odsunięty o jeden obrót, przypomina pochyłą rampę o określonym kącie. Ten kąt pochylenia, znany jako kąt prowadzenia, można wyrazić w odniesieniu do promienia wątku (średnia odległość od środka śruby do środkowej linii wątku) oraz prowadzenia. Kąt prowadzenia jest istotnym parametrem, ponieważ wpływa na efektywność śruby i ilość siły wymaganej do jej obracania.

Aby zrozumieć mechanikę śruby o gwincie kwadratowym, pomocne jest rozważenie sił tarcia, które działają na śrubę. Ponieważ siła tarcia między dwiema powierzchniami jest niezależna od obszaru kontaktu, śruba może być przedstawiona jako blok na gwincie podpórki. Kąt między siłą reakcji (siłą wywieraną przez gwint na blok) a normalną do gwintu (kierunku prostopadłego do powierzchni gwintu) nazywa się kątem tarcia. Ten kąt jest determinowany przez materiały znajdujące się w kontakcie i stosowaną między nimi smarowidłem.

Tarcie między śrubą a ładunkiem, który przenosi, odgrywa kluczową rolę w sprawności i funkcjonalności śruby o gwincie kwadratowym. Siły tarcia muszą zostać pokonane, aby obrócić śrubę i podnieść ładunek. Jednak te siły zapewniają również stabilność, zapobiegając obracaniu się śruby i spadaniu ładunku, nawet gdy siła jest zdejmowana z uchwytu. Ta funkcja samozamykająca jest szczególnie przydatna w zastosowaniach, w których śruba musi utrzymywać ładunek na miejscu bez ciągłego doprowadzenia siły.

Ze względu na swoją wysoką wydajność i zdolność do samozamykania, śruby o gwincie kwadratowym są często stosowane w maszynach do przekazywania energii lub ruchu między częściami. Przykłady takich zastosowań to podpórki, zaciski, imadła i różne prasy. Te śruby zostały zaprojektowane tak, aby wytrzymywały duże obciążenia i zapewniały płynny, kontrolowany ruch.

Działanie tarcia na śruby

charakteryzują się spiralnym grzbietem zwanym gwintem owiniętym wokół cylindrycznego wału. Są powszechnie stosowane jako łączniki do przytrzymywania przedmiotów ...

Education

JoVE Core

Mechanical Engineering

Inżynieria mechaniczna

Unit 1

Jednostka 1

Friction

Tarcie

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

square-thread screw mechanics and friction

Square-threaded screws use a helical thread to turn force into lifting motion. They are common fasteners, but they are also useful for transmitting power and motion in machines. A jack with a square-threaded screw lifts heavy loads when force is applied at the handle and the screw turns.

A screw can be viewed as a cylindrical shaft with an inclined square ridge wrapped around it. The distance between two neighboring threads is called the pitch. The lead is the distance the screw advances in one full revolution, and the lead angle is the angle of that advance when the thread is unwrapped into a ramp.

The lead angle depends on the mean thread radius, which is the average distance from the center of the screw to the centerline of the thread, and on the lead itself. This angle matters because it affects screw efficiency and the force needed to turn the screw. To study a square-threaded screw, the frictional forces acting on it must also be considered.

Because friction does not depend on contact area, the screw can be modeled as a block moving over the thread of the jack. The angle between the reaction force from the thread and the normal to the thread surface is called the angle of friction. It depends on the materials in contact and on any lubrication used between them.

Friction between the screw and the load must be overcome to raise the load. At the same time, that same friction helps keep the screw from turning back when the handle force is removed. This self-locking feature is useful when the load must stay in place without continuous force.

Square-threaded screws are valued for high efficiency and self-locking behavior. They are used in jacks, clamps, vises, and presses. These machines rely on the screw to hold heavy loads and produce smooth, controlled motion.

Square-Thread Screw Mechanics and Friction

square-thread-screw-mechanics-and-friction

dry friction

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frictional forces on screws

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upward impending motion

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self-locking screw

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collar bearings

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key terms and concepts

Learn how square-threaded screws lift heavy loads, use pitch and lead, and stay self-locking through friction in jacks, clamps, vises, and presses.

Square-Thread Screw Mechanics and Friction | JoVE K12

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mechanical engineering

Square-Thread Screw Mechanics and Friction

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