digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress can exceed the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.

Failure due to thermal shock can be prevented by;

  1. Reducing the thermal gradient seen by the object, by
    1. changing its temperature more slowly
    2. increasing the material's thermal conductivity
  2. Reducing the material's coefficient of thermal expansion
  3. Increasing its strength
  4. Introducing built-in compressive stress, as for example in tempered glass
  5. Decreasing its Young's modulus
  6. Increasing its toughness, by
    1. crack tip blunting, i.e., plasticity or phase transformation
    2. crack deflection

Effect on materials[edit]

Borosilicate glass is made to withstand thermal shock better than most other glass through a combination of reduced expansion coefficient and greater strength, though fused quartz outperforms it in both these respects. Some glass-ceramic materials (mostly in LAS system[1]) include a controlled proportion of material with a negative expansion coefficient, so that the overall coefficient can be reduced to almost exactly zero over a reasonably wide range of temperatures.

Reinforced carbon-carbon is extremely resistant to thermal shock, due to graphite's extremely high thermal conductivity and low expansion coefficient, the high strength of carbon fiber, and a reasonable ability to deflect cracks within the structure.

To measure thermal shock the impulse excitation technique proved to be a useful tool. It can be used to measure Young's modulus, Shear modulus, Poisson's ratio and damping coefficient in a non destructive way. The same test-piece can be measured after different thermal shock cycles and this way the deterioration in physical properties can be mapped out.

Relative robustness of materials[edit]

The robustness of a material to thermal shock, or thermal shock resistance[2] is characterized with the thermal shock parameter:[3]

R_{\mathrm{T}} = \frac{k\sigma_{\mathrm{T}}(1-\nu)}{\alpha E}\,,

where

Thermal shock parameter in the physics of solid-state lasers[edit]

The laser gain medium generates heat. This heat is drained through the heat sink. The transfer of heat occurs at a certain temperature gradient. The non-uniform thermal expansion of a bulk material causes the stress and tension, which may break the device even at a slow change of temperature. (for example, continuous-wave operation). This phenomenon is also called thermal shock. The robustness of a laser material to the thermal shock is characterized by the thermal shock parameter. [3] (see above)

Roughly, at the efficient operation of laser, the power P_{\mathrm{h}} of heat generated in the gain medium is proportional to the output power P_{\mathrm{s}} of the laser, and the coefficient q of proportionality can be interpreted as heat generation parameter; then, P_{\mathrm{h}}=q P_{\mathrm{s}}. The heat generation parameter is basically determined by the quantum defect of the laser action, and one can estimate q=1-\omega_{\mathrm{s}}/\omega_{\mathrm{p}}, where \omega_{\mathrm{p}} and \omega_{\mathrm{s}} are frequency of the pump and that of the lasing.

Then, for the layer of the gain medium placed at the heat sink, the maximal power can be estimated as

P_{\mathrm{s, max}} = 3 \frac{R_{\mathrm{T}}}{q} \frac{L^2}{h},\,

where h is thickness of the layer and L is the transversal size. This estimate assumes the unilateral heat drain, as it takes place in the active mirrors. For the double-side sink, the coefficient 4 should be applied.

Thermal loading[edit]

The estimate above is not the only parameter which determines the limit of overheating of a gain medium. The maximal raise \Delta T of temperature, at which the medium still can efficiently lase, is also important property of the laser material. This overheating limits the maximal power with estimate

P_{\mathrm{s, max}} = 2 \frac {k \Delta T}{q} \frac{L^2}{h}\,

Combination of the two estimates above of the maximal power gives the estimate

P_{\mathrm{s, max}} = R \frac{L^2}{h}\,

where


R= \textrm{min}
\left\{
\begin{array}{c}
  3 R_{\mathrm{T}}/q\\
  2 k\Delta T/q
\end{array}
\right.
Estimates [4] of maximal value of loss \beta, at which desirable output power P is still available in a single disk laser, versus normalized power s=\frac{\omega_{\rm p}}{\omega_{\rm s}}\frac{P Q}{R^2}, and experimental data (circles)

is thermal loading; parameter, which is important property of the laser material. The thermal loading, saturation intensity Q and the loss \beta determine the limit of power scaling of the disk lasers .[5] Roughly, the maximal power at the optimised sizes L and h, is of order of P=\frac{R^2}{Q\beta^3}. This estimate is very sensitive to the loss \beta. However, the same expression can be interpreted as a robust estimate of the upper bound of the loss ~\beta~ required for the desirable output power P:

~\beta_{\mathrm{max}}=\left(\frac{R^2}{PQ}\right)^{\frac{1}{3}}.

All the disk lasers reported work at the round-trip loss below this estimate.[4] The thermal shock parameter and the loading depend of the temperature of the heat sink. Certain hopes are related with a laser, operating at cryogenic temperatures. The corresponding Increase of the thermal shock parameter would allow to softer requirements for the round-trip loss of the disk laser at the power scaling.

Examples of thermal shock failure[edit]

  • Hard rocks containing ore veins such as quartzite were formerly broken down using fire-setting, which involved heating the rock face with a wood fire, then quenching with water to induce crack growth. It is described by Diodorus Siculus in Egyptian gold mines, Pliny the Elder and Georg Agricola.
  • Ice cubes placed in a glass of warm water crack by thermal shock as the exterior surface increases in temperature much faster than the interior. As ice has a larger volume than the water that created it, the outer layer shrinks as it warms and begins to melt, whilst the interior remains largely unchanged. This rapid change in volume between different layers creates stresses in the ice that build until the force exceeds the strength of the ice, and a crack forms, sometimes with enough force to shoot ice shards out of the container.
  • Incandescent bulbs that have been running for a while have a very hot surface. Splashing cold water on them can cause the glass to shatter due to thermal shock, and the bulb to implode.
  • An antique cast iron cookstove is basically an iron box on legs, that has a cast iron top. One builds a wood or coal fire inside the box and cooks on the top outer surface of the box, like a griddle. If one builds too hot a fire, and then tries to cool the stove by pouring water on the top surface, it will crack and perhaps fail by thermal shock.
  • The causes of three aircraft incidents in the 1990s (United Airlines Flight 585, USAir Flight 427 and Eastwind Airlines Flight 517). Thermal shock caused their power control unit in the tail to jam and cause rudder hardover, forcing the planes in the direction the rudder turns.
  • It is widely hypothesized[by whom?] that following the casting of the Liberty Bell, it was allowed to cool too quickly which weakened the integrity of the bell and resulted in a large crack along the side of it the first time it was rung. Similarly, the strong gradient of temperature (due to the fire) is believed to cause the crash of the Tsar Bell.
  • Thermal shock is a primary contributor to head gasket failure in internal combustion engines.

See also[edit]

References[edit]

  1. ^ Scott L. Swartz, Ceramics having negative coefficient of thermal expansion, method of making such ceramics, and parts made from such ceramics, United States Patent 6066585
  2. ^ T. J. Lue; N. A. Fleck (1998). "The Thermal Shock Resistance of Solids". Acta Materialia 46 (13): 4755–4768. 
  3. ^ a b W.F.Krupke; M.D. Shinn, J.E. Marion, J.A. Caird, and S.E. Stokowski (1986). "Spectroscopic, optical, and thermomechanical properties of neodymium- and chromium-doped gadolinium scandium gallium garnet" (abstract). JOSAB 3 (1): 102–114. Bibcode:1986JOSAB...3..102K. doi:10.1364/JOSAB.3.000102. 
  4. ^ a b D.Kouznetsov; J.-F.Bisson (2008). "Role of the undoped cap in the scaling of a thin disk laser". JOSA B 25 (3): 338–345. Bibcode:2008JOSAB..25..338K. doi:10.1364/JOSAB.25.000338. 
  5. ^ D. Kouznetsov; J.F. Bisson, J. Dong, and K. Ueda (2006). "Surface loss limit of the power scaling of a thin-disk laser" (abstract). JOSAB 23 (6): 1074–1082. Bibcode:2006JOSAB..23.1074K. doi:10.1364/JOSAB.23.001074. Retrieved 2007-01-26.  ; [1]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Thermal_shock — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
157791 videos foundNext > 

Ultra High Alumina Thermal Shock Testing

Thermal Shock Vacuum Tube Implosion

WITNESS THE AWESOME POWER OF THERMAL SHOCK! This is another long lost friend found buried and forgotten. I can't remember if this got moved to bluesmokeprodu...

Cutting glass bottles into rings easily with thermal stress

In this video I cut jars and bottles into rings and cylinders, by using controlled thermal stress a bottle can be cut with a beatify clean/smooth finish that...

Riptide Music / Cliff Lin - Thermal Shock ("Tomb Raider - Crossroads" Trailer Music)

Please Read Description thank you. Track which is featured on the latest Game trailer of "Tomb Raider - Crossroads 2012 trailer" Subscribe if you like for mo...

Thermal Shock in a Steam Boiler

This video by Clarity Water Technologies, LLC shows the result of thermal shock in a boiler. This happens when the heated water inside the vessel is suddenly...

Cellucor D4 Thermal Shock Reviews - eSupplements.com

Cellucor D4 Thermal Shock Reviews - eSupplements.com http://www.eSupplements.com Like Us: https://www.facebook.com/eSupplements Tweet Us: https://twitter.com...

Cracking Glass (thermal Shock)

Cellucor D4 Thermal Shock Fat Burner

Supplement review on Cellucor's D4 Thermal Shock. Great Fat Burner and i liked it a lot. enjoy. :)

Flooting Grooves - Thermal Shock

Flooting Grooves is Pearce Van Der Merwe. Born in Cape Town in 1975, he grew up in South Africa and Italy, surrounded by music. Having a varied background ra...

RipTide Music - Thermal Shock

Album: This Is War Composed By: Cliff Lin Official: http://riptidemusic.com/ Purchase: http://www.amazon.com/This-Is-War/dp/B007G4M5TM/ Composer's Official: ...

157791 videos foundNext > 

1415 news items

Hellenic Shipping News Worldwide

Hellenic Shipping News Worldwide
Tue, 25 Nov 2014 13:56:15 -0800

California became one of the first places to rigorously regulate the sulphur content of marine fuels used in its ports and up to 24 nm off its shores. Being a pioneer in the field of the mandated use of 0.10 % sulphur content fuel as of January 2014, a ...

Azom.com

Azom.com
Wed, 26 Nov 2014 06:15:00 -0800

Syalon 101, a specific grade of silicon nitride (Figure 1), has excellent mechanical, thermal, and wear resistant properties, which means it is not affected by thermal shock and thermal cycling stresses produced during the welding process. Syalon 101 ...

Ship & Bunker

Ship & Bunker
Wed, 26 Nov 2014 19:56:15 -0800

The cause of the incidents is reportedly due to the differences in temperature between hot HFO and cooler MGO, which sent ship engines into "thermal shock." Ott also speculated that the lower viscosity of MGO may have led to more engine wear and tear.

Daily Mail

Daily Mail
Wed, 26 Nov 2014 07:03:45 -0800

A 12-year-old boy had a lucky escape after a glass table close to his bed spontaneously exploded. Adam Hodges had just left his bedroom in Basildon in Essex to go for breakfast when the table exploded, leaving thousands of sharp shards of glass ...

The Maritime Executive

Energy Global
Wed, 26 Nov 2014 04:22:30 -0800

As the operating temperatures of HFO and MGO differ by approximately 100 °C, the change over can cause a rapid fall in temperature and increase the danger of thermal shock to the equipment. Fuel systems also have to account for their difference in ...

The Motorship

The Motorship
Wed, 26 Nov 2014 08:52:30 -0800

AS HFO's and MGO's operating temperature differs by around 100 degrees Celsius, the company says the change-over may cause a rapid fall in temperature and increase the danger of thermal shock to the equipment. Fuel systems also have to account for ...

Photonics.com

Photonics.com
Wed, 19 Nov 2014 08:52:30 -0800

Skin irradiation with high-power pulsed laser light induces a thermal shock, which stimulates fibroblasts to produce new collagen and reduce wrinkles. Microablative fractional laser resurfacing enables faster healing than earlier techniques by ablating ...

Daily Mail

Daily Mail
Mon, 17 Nov 2014 09:35:31 -0800

The green turtles 'appeared in winter with thermal shock, the low water temperature made them to go to the coast,' Karumbé Director Andres Estrade told Ruptly. Veronica Larrosa, director of the school which took part, told El Siglo that the program had ...
Loading

Oops, we seem to be having trouble contacting Twitter

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!

Searchlight Group

Digplanet also receives support from Searchlight Group. Visit Searchlight