The stick–slip phenomenon, also known as the slip–stick phenomenon or simply stick–slip, is the spontaneous jerking motion that can occur while two objects are sliding over each other.
Cause
Below is a simple,
heuristic
A heuristic (; ), or heuristic technique, is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediate, ...
description of stick–slip phenomena using
classical mechanics
Classical mechanics is a physical theory describing the motion of macroscopic objects, from projectiles to parts of machinery, and astronomical objects, such as spacecraft, planets, stars, and galaxies. For objects governed by classical ...
that is relevant for engineering descriptions. However, in actuality, there is little consensus in academia regarding the actual physical description of stick–slip which follows the lack of understanding about friction phenomena in general. The generally agreed upon view is that stick–slip behavior results from common
phonon
In physics, a phonon is a collective excitation in a periodic, Elasticity (physics), elastic arrangement of atoms or molecules in condensed matter physics, condensed matter, specifically in solids and some liquids. A type of quasiparticle, a phon ...
modes (at the interface between the substrate and the slider) that are pinned in an undulating potential well landscape that un-pin (slip) and pin (stick) primarily influenced by thermal fluctuations. However, stick–slip frictional behaviour is encountered over a wide range of length scales from the atomic up to the tectonic, and there is no single underlying physical mechanism responsible for all manifestations.
The stiffness of the spring (shown in image below), the
normal Normal(s) or The Normal(s) may refer to:
Film and television
* ''Normal'' (2003 film), starring Jessica Lange and Tom Wilkinson
* ''Normal'' (2007 film), starring Carrie-Anne Moss, Kevin Zegers, Callum Keith Rennie, and Andrew Airlie
* ''Norma ...
load at the interface (the weight of the slider), the duration of time the interface has existed (influencing chemical mass transport and bond formation), the original rate (velocity) of sliding (when the slider is in the slip phase) – all influence the behavior of the system. A description using common phonons (rather than constitutive laws like Coulomb's friction model) provides explanations for noise that generally accompanies stick–slip through surface acoustic waves. The use of complicated constitutive models that lead to discontinuous solutions (see
Painlevé paradox) end up requiring unnecessary mathematical effort (to support non-smooth dynamical systems) and do not represent the true physical description of the system. However, such models are very useful for low fidelity simulations and animation.
Engineering description
Stick–slip can be described as surfaces alternating between sticking to each other and sliding over each other, with a corresponding change in the force of
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
. Typically, the
static friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
coefficient (a heuristic number) between two surfaces is larger than the
kinetic friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
coefficient. If an applied
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
is large enough to overcome the static friction, then the reduction of the friction to the kinetic friction can cause a sudden jump in the velocity of the movement. The attached picture shows symbolically an example of stick–slip.
![Stick-slip](https://upload.wikimedia.org/wikipedia/commons/d/d0/Stick-slip.svg)
V is a drive system, R is the elasticity in the system, and M is the load that is lying on the floor and is being pushed horizontally. When the drive system is started, the Spring R is loaded and its pushing force against load M increases until the static friction coefficient between load M and the floor is not able to hold the load anymore. The load starts sliding and the friction coefficient decreases from its static value to its dynamic value. At this moment the spring can give more power and accelerates M. During M's movement, the force of the spring decreases, until it is insufficient to overcome the dynamic friction. From this point, M decelerates to a stop. The drive system however continues, and the spring is loaded again etc.
Examples
Examples of stick–slip can be heard from
hydraulic cylinders
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment (engineering vehicles), ...
, tractor wet brakes, honing machines etc. Special
dopes can be added to the
hydraulic fluid
A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoe ...
or the cooling fluid to overcome or minimize the stick–slip effect. Stick–slip is also experienced in lathes, mill centres, and other machinery where something slides on a slideway. Slideway oils typically list "prevention of stick–slip" as one of their features. Other examples of the stick–slip phenomenon include the music that comes from
bowed instruments
Bowed string instruments are a subcategory of string instruments that are played by a bow rubbing the strings. The bow rubbing the string causes vibration which the instrument emits as sound.
Despite the numerous specialist studies devoted to t ...
, the noise of
car
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarded as ...
brakes
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
and
tires
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
, and the noise of a stopping
train
In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and Passenger train, transport people or Rail freight transport, freight. Trains are typically pul ...
. Stick–slip also has been observed in articular cartilage in mild loading and sliding conditions, which could result in an abrasive wear of the cartilage.
Another example of the stick–slip phenomenon occurs when musical notes are played with a
glass harp
A glass harp (also called musical glasses, singing glasses, angelic organ, verrillon or ghost fiddle) is a musical instrument made of upright wine glasses.
It is played by running moistened or chalked fingers around the rim of the glasses. Eac ...
by rubbing a wet finger along the rim of a crystal wine glass. One animal that produces sound using stick–slip friction is the
spiny lobster
Spiny lobsters, also known as langustas, langouste, or rock lobsters, are a family (Palinuridae) of about 60 species of achelate crustaceans, in the Decapoda Reptantia. Spiny lobsters are also, especially in Australia, New Zealand, Ireland, So ...
which rubs its antennae over smooth surfaces on its head.
Another, more common example which produces sound using stick–slip friction is the
grasshopper
Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago.
Grasshopp ...
.
Stick–slip can also be observed on the
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, and ...
ic scale using a
friction force microscope
In materials science, chemical force microscopy (CFM) is a variation of atomic force microscopy (AFM) which has become a versatile tool for characterization of materials surfaces. With AFM, structural morphology is probed using simple tapping or ...
. In such case, the phenomenon can be interpreted using the
Tomlinson model
The Tomlinson model, also known as the Prandtl–Tomlinson Model, is one of the most popular models in nanotribology widely used as the basis for many investigations of frictional mechanisms on the atomic scale. Essentially, a nanotip is dragged b ...
.
The behaviour of seismically-active
faults is also explained using a stick–slip model, with
earthquakes
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
being generated during the periods of rapid slip.
The characteristic sound of
basketball
Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appr ...
shoe
A shoe is an item of footwear intended to protect and comfort the human foot. They are often worn with a sock. Shoes are also used as an item of decoration and fashion. The design of shoes has varied enormously through time and from culture t ...
s squeaking on a
court
A court is any person or institution, often as a government institution, with the authority to adjudicate legal disputes between parties and carry out the administration of justice in civil, criminal, and administrative matters in accordance ...
is produced by stick–slip contact between the
rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
soles and the
hardwood
Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
floor.
Stick–slip is the basic physical mechanism for the active control of friction by applying vibrations.
Researchers at
University of California, San Diego
The University of California, San Diego (UC San Diego or colloquially, UCSD) is a public university, public Land-grant university, land-grant research university in San Diego, California. Established in 1960 near the pre-existing Scripps Insti ...
developed a swarm of self-folding
origami
) is the Japanese paper art, art of paper folding. In modern usage, the word "origami" is often used as an inclusive term for all folding practices, regardless of their culture of origin. The goal is to transform a flat square sheet of pape ...
robots that use the stick–slip phenomenon for locomotion. Another robot that relies on stick–slip is the
Kilobot
The Kilobot is a 3.3 cm tall low-cost swarm robot developed by Radhika Nagpal and Michael Rubenstein at Harvard University. They can act in groups, up to a thousand, to execute commands programmed by users that could not be executed by indivi ...
.
Apparent stick–slip can even be observed in a system having no static friction force ("dynamic stiction")
References
* {{citation, title=Evidence of self-organized criticality in dry sliding friction, journal=Journal of Physics: Condensed Matter, volume=15, issue=12, pages=L191, year=2003, last1=Zypman, first1=F. R., last2=Ferrante, first2=J., last3=Jansen, first3=M., last4=Scanlon, first4=K., last5=Abel, first5=P., doi=10.1088/0953-8984/15/12/101, s2cid=250780286
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, 2009Weston-Dawkes W., et al., "Designing Customizable Self-Folding Swarm Robots," 2017
Mechanical engineering
Friction