A material is brittle if, when subjected to stress, it breaks without significant deformation (strain). Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses (which do not deform plastically) and some polymers, such as PMMA and polystyrene. Many steels become brittle at low temperatures (see ductile-brittle transition temperature), depending on their composition and processing.
When used in materials science, it is generally applied to materials that fail when there is little or no evidence of plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred.
When a material has reached the limit of its strength, it usually has the option of either deformation or fracture. A naturally malleable metal can be made stronger by impeding the mechanisms of plastic deformation (reducing grain size, precipitation hardening, work hardening, etc.), but if this is taken to an extreme, fracture becomes the more likely outcome, and the material can become brittle. Improving material toughness is therefore a balancing act.
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Toughening [link]
This principle generalizes to other classes of material. Naturally brittle materials, such as glass, are not difficult to toughen effectively. Most such techniques involve one of two mechanisms: to deflect or absorb the tip of a propagating crack, or to create carefully controlled residual stresses so that cracks from certain predictable sources will be forced closed. The first principle is used in laminated glass where two sheets of glass are separated by an interlayer of polyvinyl butyral, which as a viscoelastic polymer absorbs the growing crack. The second method is used in toughened glass and pre-stressed concrete. A demonstration of glass toughening is provided by Prince Rupert's Drop. Brittle polymers can be toughened by using rubber particles to initiate crazes when a sample is stressed, a good example being high impact polystyrene or HIPS. The least brittle structural ceramics are silicon carbide (mainly by virtue of its high strength) and transformation-toughened zirconia.
A different philosophy is used in composite materials, where brittle glass fibres, for example, are embedded in a ductile matrix such as polyester resin. When strained, cracks are formed at the glass-matrix interface, but so many are formed that much energy is absorbed and the material is thereby toughened. The same principle is used in creating metal matrix composites.
Effect of pressure [link]
Generally, the brittle strength of a material can be increased by pressure. This happens as an example in the brittle-ductile transition zone at an approximate depth of 10 kilometres (6.2 mi) in the Earth's crust, at which rock becomes less likely to fracture, and more likely to deform ductilely.
Crack growth [link]
Supersonic fracture is crack motion faster than the speed of sound in a brittle material. This phenomenon was first discovered[citation needed] by scientists from the Max Planck Institute for Metals Research in Stuttgart (Markus J. Buehler and Huajian Gao) and IBM Almaden Research Center in San Jose, California (Farid F. Abraham).
See also [link]
- Izod impact strength test
- Charpy impact test
- Fractography
- Forensic engineering
- Ductility
- Strengthening mechanisms of materials
References [link]
- Lewis, Peter Rhys; Reynolds, K; Gagg, C (2004). Forensic Materials Engineering: Case studies. CRC Press. ISBN 978-0-8493-1182-6.
- Rösler, Joachim; Harders, Harald; Bäker, Martin (2007). Mechanical behaviour of engineering materials: metals, ceramics, polymers, and composites. Springer. ISBN 978-3-642-09252-7.
https://wn.com/Brittleness
Software brittleness
In computer programming and software engineering, software brittleness is the increased difficulty in fixing older software that may appear reliable, but fails badly when presented with unusual data or altered in a seemingly minor way. The phrase is derived from analogies to brittleness in metalworking.
Causes
When software is new, it is very malleable; it can be formed to be whatever is wanted by the implementers. But as the software in a given project grows larger and larger, and develops a larger base of users with long experience with the software, it becomes less and less malleable. Like a metal that has been work-hardened, the software becomes a legacy system, brittle and unable to be easily maintained without fracturing the entire system.
Brittleness in software can be caused by algorithms that do not work well for the full range of input data. A good example is an algorithm that allows a divide by zero to occur, or a curve-fitting equation that is used to extrapolate beyond the data that it was fitted to. Another cause of brittleness is the use of data structures that restrict values. This was commonly seen in the late 1990s as people realized that their software only had room for a 2 digit year entry; this led to the sudden updating of tremendous quantities of brittle software before the year 2000. Another more commonly encountered form of brittleness is in graphical user interfaces that make invalid assumptions. For example, a user may be running on a low resolution display, and the software will open a window too large to fit the display. Another common problem is expressed when a user uses a color scheme other than the default, causing text to be rendered in the same color as the background, or a user uses a font other than the default, which won't fit in the allowed space and cuts off instructions and labels.
Brittle (food)
Brittle is a type of confection consisting of flat broken pieces of hard sugar candy embedded with nuts such as pecans, almonds, or peanuts. It has many variations around the world, such as pasteli in Greece,croquant in France,gozinaki in Georgia, chikki in India and kotkoti in Bangladesh. In parts of the Middle East, brittle is made with pistachios, while many Asian countries use sesame seeds and peanuts. Peanut brittle is the most popular brittle recipe in the US. The term brittle first appears in print in 1892, though the candy itself has been around for much longer.
Traditionally, a mixture of sugar and water is heated to the hard crack stage corresponding to a temperature of approximately 300 °F (149 °C), although some recipes also call for ingredients such as corn syrup and salt in the first step. Nuts are mixed with the caramelized sugar. At this point spices, leavening agents, and often peanut butter or butter are added. The hot candy is poured out onto a flat surface for cooling, traditionally a granite or marble slab. The hot candy may be troweled to uniform thickness. When the brittle cools, it is broken into pieces.
Scanner
Scanner may refer to:
Technology
For invisible radiation
For (near) light
- 3D scanner, which digitizes the three-dimensional shape of a real object
Computer software
Scanner (band)
Scanner is a German power metal band that was formed in 1986. Three of the band members had previously taken part in an album release by the band Lions Breed, Damn The Night (Earthshaker 1985). The band changed its name to Scanner, adopting a science fiction image for their lyrics, album covers and live performances. They released their first album, Hypertrace, in 1988 through Noise Records. They have reformed twice, releasing their latest album on January 23rd, 2015, The Judgement (Massacre Records).
Members
Discography
Albums
Demos
References
External links
List of G.I. Joe: A Real American Hero characters (S–Z)
This is an alphabetical List of G.I. Joe: A Real American Hero characters whose code names start with the letters S-Z.
Salvo
Salvo is the G.I. Joe Team's Anti-Armor Trooper. His real name is David K. Hasle, and he was born in Arlington, Virginia. Salvo was first released as an action figure in 1990, and again in 2005. Both versions have the T-shirt slogan 'The Right of Might'.
Salvo's primary military specialty is anti-armor trooper. He also specializes in repairing "TOW/Dragon" missiles. Salvo expresses a deep distrust of advanced electronic weaponry. He prefers to use mass quantities of conventional explosives to overwhelm enemy forces.
In the Marvel Comics G.I. Joe series, he first appeared in issue #114. There, he fights as part of a large scale operation against Cobra forces in the fictional country of Benzheen. Steeler, Dusty, Salvo, Rock'N'Roll and Hot Seat get into vehicular based combat against the missile expert Metal-Head He is later part of the Joe team on-site who defends G.I. Joe headquarters in Utah against a Cobra assault.
