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.
174665 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...

Cracking Glass (thermal Shock)

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...

Cellucor D4 Thermal Shock Fat Burner

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

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...

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...

Touch panel Demostration- Thermal shock test

Alternate our touch panel twice between - 4 0℃ and +90℃ environment. After that, the panel still works well.These panels are made by Abon Touchsystems Inc. i...

174665 videos foundNext > 

81 news items

 
The Guardian
Wed, 29 Oct 2014 06:00:52 -0700

In extreme temperatures, they can even go into a kind of thermal shock that can severely alter flavor. On the bright side, the grapes also retain more sugar in these circumstances, making the final product higher in alcohol, so the casual sipper won't ...
 
Android Headlines - Android News
Wed, 29 Oct 2014 17:45:00 -0700

The baby of the two is the B100 although in spite of being the baby, it is the more durable of the two meeting military standard MIL SPEC 810G for salt spray, thermal shock and vibration. It also comes with a dual-core MediaTek processor and 512MB RAM.
 
Hallels
Tue, 28 Oct 2014 04:33:44 -0700

The European version of the Samsung Galaxy S5 Active will go on sale from November. The retailer from Dutch online Central point indicated the probable launching schedule of the smartphone. The significant release date is Nov. 16, 2014 as listed by the ...

Boston Globe

Boston Globe
Sun, 19 Oct 2014 21:15:31 -0700

Engineers say that could lead to a condition called “pressurized thermal shock,” in which a reactor vessel would crack open. To measure embrittlement, the plants use extra samples of the metal from which their reactor vessels were made, called coupons, ...
 
ACHR NEWS
Mon, 27 Oct 2014 04:26:15 -0700

According to Matthew Freeman, boilers product manager, Bosch Thermotechnology Corp., “With a conventional boiler, the installer wants to be sure to protect the cast iron heat exchanger from thermal shock, which occurs when cold return water enters the ...
 
PR Web (press release)
Mon, 27 Oct 2014 12:16:09 -0700

100% electrically tested and visually inspected to MIL-STD-883, these silicon resistor chips feature resistance to thermal shock and high-temperature exposure. They are specified for an operating temperature range of –55°C to +125°C. Samples of all ...
 
Lewiston Sun Journal
Thu, 23 Oct 2014 19:37:30 -0700

This is the second time the vintage Burnham boilers have had cracked sections because of thermal shock, Colpitts said. The brand has a reputation for it, he said. Facilities Director Nelson Baillargeon said Thursday that the unit will most likely be ...
 
DigitalJournal.com
Thu, 23 Oct 2014 08:00:00 -0700

The capacitor combines its high capacitance and established reliability with excellent reverse voltage, vibration, and thermal shock performance. Optimized for timing, filtering, energy hold-up, and pulse power applications in power supplies for space ...
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