physics

Stick–slip phenomenon

Stick–slip phenomenon is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Stick–slip phenomenon rather than just read about it. In short: The stick–slip phenomenon, also known as the slip–stick phenomenon or simply stick–slip, is a type of motion exhibited by objects in contact sliding over one another. The motion of these objects is usually not perfectly smooth, but rather irregular, with brief accelerations (slips) interrupted by stops (sticks).

Key takeaways

Stick–slip phenomenon belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Stick–slip phenomenon to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Stick–slip phenomenon from memory before moving on to harder problems.

Reference excerpt

The stick–slip phenomenon, also known as the slip–stick phenomenon or simply stick–slip, is a type of motion exhibited by objects in contact sliding over one another. The motion of these objects is usually not perfectly smooth, but rather irregular, with brief accelerations (slips) interrupted by stops (sticks). Stick–slip motion is normally connected to friction, and may generate vibration (noise) or be associated with mechanical wear of the moving objects, and is thus often undesirable in mechanical devices. On the other hand, stick–slip motion can be useful in some situations, such as the movement of a bow across a string to create musical tones in a bowed string instrument.

Details

With stick–slip there is typically a jagged type of behavior for the friction force as a function of time as illustrated in the static kinetic friction figure. Initially there is relatively little movement and the force climbs until it reaches some critical value which is set by the multiplication of the static friction coefficient and the applied load—the retarding force here follows the standard ideas of friction from Amontons' laws. Once this force is exceeded movement starts at a much lower load which is determined by the kinetic friction coefficient which is almost always smaller than the static coefficient. At times the object moving can get 'stuck', with local rises in the force before it starts to move again. There are many causes of this depending upon the size scale, from atomic to processes involving millions of atoms.

Stick–slip can be modeled as a mass coupled by an elastic spring to a constant drive force (see "Model for stick–slip" illustration). The drive system V applies a constant force, loading spring R and increasing the pushing force against load M. This force increases until retarding force from the static friction coefficient between load and floor is exceeded. The load then starts sliding, and the friction coefficient decreases to the value corresponding to load times the dynamic friction. Since this frictional force will be lower than the static value, the load accelerates until the decompressing spring can no longer generate enough force to overcome dynamic friction, and the load stops moving. The pushing force due to the spring builds up again, and the cycle repeats. Stick–slip may be caused by many different phenomena, depending on the types of surfaces in contact and also the scale; it occurs with everything from the sliding of atomic force microscope tips to large tribometers. For rough surfaces, it is known that asperities play a major role in friction. The bumping together of asperities on the surface creates momentary sticks. For dry surfaces with regular microscopic topography, the two surfaces may need to creep at high friction for certain distances (in order for bumps to move past one another), until a smoother, lower-friction contact is formed. On lubricated surfaces, the lubricating fluid may undergo transitions from a solid-like state to a liquid-like state at certain forces, causing a transition from sticking to slipping. On very smooth surfaces, stick–slip behavior may result from coupled phonons (at the interface between the substrate and the slider) that are pinned in an undulating potential well, sticking or slipping with thermal fluctuations. Stick–slip occurs on all types of materials and on enormously varying length scales. The frequency of slips depends on the force applied to the sliding load, with a higher force corresponding to a higher frequency of slip.

Examples Stick–slip motion is ubiquitous in systems with sliding components, such as disk brakes, bearings, electric motors, wheels on roads or railways, and in mechanical joints. Stick–slip also has been observed in articular cartilage in mild loading and sliding conditions, which could result in abrasive wear of the cartilage. Many familiar sounds are caused by stick–slip motion, such as the squeal of chalk on a chalkboard, the squeak of basketball shoes on a basketball court, and the sound made by the spiny lobster. Stick–slip motion is used to generate musical notes in bowed string instruments, the glass harp and the singing bowl. Stick–slip can also be observed on the atomic scale using a friction force microscope. The behaviour of seismically active faults is also explained using a stick–slip model, with earthquakes being generated during the periods of rapid slip.

See also Contact mechanics – Study of the deformation of solids that touch each other Friction – Force resisting sliding motion Lubrication – Presence of a material to reduce friction between two surfaces Nanotribology – Study of friction, wear, adhesion and lubrication phenomena at the nanoscale Tribology – Science of rubbing surfaces Tribometer – Instrument that measures friction and wear between surfaces

References

External links Simulation of stick-slip behaviour in a friction force microscope (movie) Jianguo Wu, Ashlie Martini, "Atomic Stick-Slip," DOI: 10254/nanohub-r7771.1, 2009

Illustrations

Worked examples

Example 1 — a first encounter with Stick–slip phenomenon

Start with the simplest possible case. Write down what Stick–slip phenomenon claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Stick–slip phenomenon before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Stick–slip phenomenon ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Stick–slip phenomenon

In research: Stick–slip phenomenon appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Stick–slip phenomenon in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Stick–slip phenomenon is common in secondary-school and first-year university syllabi. It links to neighbouring topics Friction, Mechanical engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Stick–slip phenomenon outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Stick–slip phenomenon in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Stick–slip phenomenon means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Stick–slip phenomenon out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Stick–slip phenomenon in simple terms?

Why does Stick–slip phenomenon matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Stick–slip phenomenon?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Stick–slip phenomenon.