Name: how temperature changes create stress
Uploaded: 2023-04-30T12:29:32.000Z
Duration: 1 min 9 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.13

CHEM.13.D

Thermal Stress

A body experiences stress when it undergoes temperature variations; this stress is known as thermal stress, which can even permanently deform the body.
For example, a space is intentionally maintained between two joints of a rod on the railway track to prevent the deformation or bending of rods.
To calculate the thermal stress in an object, first, determine the thermal expansion or contraction, then calculate the stress.
Consider a rod of length L0.. When heat is applied, the rod will expand in length by delta &#39;L,&#39;&#160;and the fractional change in the length of the rod can be evaluated.
Now, the same rod is fixed to both ends. When the heat is applied, the rod experiences strain as it cannot expand. To restore the original length of the rod, the stress can be calculated.
Recalling the definition of Young&#39;s modulus, it is the ratio of stress to strain.
Therefore, the thermal stress can be determined by combining the equations and rearranging the terms.

thermische spanning

Als de temperatuur van een object wordt gewijzigd terwijl het niet kan uitzetten of samentrekken, wordt het object onderworpen aan spanning. De spanning is drukgevend als het object uitzet zonder dat er beperkingen zijn, en trekspanning als het samentrekt. Deze spanning als gevolg van temperatuurverandering staat bekend als thermische spanning. Het kan behoorlijk groot zijn en schade veroorzaken. Om deze stress te vermijden, kunnen ingenieurs componenten zo ontwerpen dat ze vrij kunnen uitzetten en inkrimpen. Op snelwegen worden bijvoorbeeld opzettelijk gaten tussen de blokken gelaten om te voorkomen dat er thermische spanning ontstaat. Als er geen gaten meer kunnen worden overgelaten, moeten ingenieurs bij hun ontwerpen rekening houden met thermische spanning. De wapeningsstaven in beton zijn dus gemaakt van staal, omdat de lineaire uitzettingscoëfficiënt van staal vrijwel gelijk is aan die van beton. Thermische stress kan veel verschijnselen verklaren, zoals de verwering van rotsen en trottoirs door de uitzetting van ijs als het vriest. Spoorwegen en wegen kunnen op warme dagen knikken als er niet voldoende dilatatievoegen zijn, en hoogspanningsleidingen zakken in de zomer meer door dan in de winter en breken bij koud weer als er onvoldoende speling is. Scheuren gaan open en dicht in gipsmuren terwijl een huis opwarmt en afkoelt. Glazen kookpannen zullen barsten als ze snel of ongelijkmatig worden gekoeld als gevolg van verschillende contracties en de daaruit voortvloeiende spanningen.

Thermische spanning

If the temperature of an object is changed while it is prevented from expanding or contracting, the object is subjected to stress. The stress is ...

Education

JoVE Core

Physics

Natuurkunde

Unit 1

Onderdeel 1

Temperature and Heat

Temperatuur en Warmte

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

how temperature changes create stress

Thermal stress is the stress that builds up when an object changes temperature but cannot expand or contract freely. If the object would expand without restraint, the stress is compressive. If it would contract, the stress is tensile.

This stress from heating or cooling can become large enough to cause damage. Engineers often reduce it by designing parts so they can move as temperature changes. Highway blocks, for example, are separated by gaps so thermal stress does not build up.

When gaps are not possible, thermal stress must be part of the design. In concrete, the reinforcing rods are made of steel because steel and concrete have nearly the same coefficient of linear expansion. That similarity helps the materials change length at nearly the same rate.

Thermal stress also explains many everyday and natural effects. Ice can weather rocks and pavements as it freezes and expands. Railroad tracks and roadways may buckle on hot days if they do not have enough expansion joints, and power lines can sag more in summer and snap in cold weather if they lack slack.

The same idea helps explain cracks that open and close in plaster walls as a house warms and cools. Glass cooking pans can crack if they cool too fast or unevenly. In each case, different contraction or expansion creates stress in the material.

How Temperature Changes Create Stress

temperature and thermal equilibrium

Heat, Temperature, and Everyday Energy

Heat and temperature are key ideas in thermodynamics and in everyday life. People often connect temperature with hot and cold, but science gives it a more precise meaning. Temperature is the quantity measured with a thermometer. It is also linked to the average translational kinetic energy of particles. Heat is different from temperature. Heat is energy that moves from one place or material to another because there is a difference in temperature. That difference in temperature keeps heat...

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thermal expansion

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thermal stress

Thermal stress is the stress that builds up when an object changes temperature but cannot expand or contract freely. If the object would expand without restraint, the stress is compressive. If it would contract, the stress is tensile. This stress from heating or cooling can become large enough to cause damage. Engineers often reduce it by designing parts so they can move as temperature changes. Highway blocks, for example, are separated by gaps so thermal stress does not build up. When gaps...

thermal expansion and thermal stress: problem solving

thermal-expansion-and-thermal-stress-problem-solving

Golden Gate Bridge Thermal Expansion

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heat flow and specific heat

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phase changes

Heat and Phase Change Energy

Heat and phase change energy explain why substances melt, freeze, boil, and condense. A solid turns into a liquid during melting, also called fusion. The reverse process is freezing. A liquid turns into a gas during evaporation. The reverse process is condensation. Each substance changes phase at specific temperatures. The melting point is the temperature where a substance melts or freezes. The boiling point is the temperature where a substance boils or condenses. These temperatures depend on...

calorimetry

Heat Exchange in an Insulated System

Calorimetry studies heat exchange in an insulated system. A calorimeter is a container that prevents heat transfer in or out. Scientists use calorimetry to measure heat and specific heat capacity. A calorimetry problem is any situation where the objects are thermally isolated from their surroundings. The key idea comes from conservation of energy. During heat transfer, the heat gained by the colder object must equal the heat lost by the hotter object. A simple example is water poured into a...

mechanisms of heat transfer i

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mechanisms of heat transfer ii

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conduction, convection and radiation: problem solving

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Heat Transfer Calculations with Conduction, Convection

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radiation: applications

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absorption of radiation

Radiation Heat Transfer and Thermographs

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key terms and concepts

Learn how heating and cooling create compressive or tensile stress, why expansion joints matter, and how thermal stress affects roads, wires, walls, and glass.

How Temperature Changes Create Stress | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

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First Law of Thermodynamics

Energy Conservation

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Internal Energy

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Enthalpy

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Thermochemical Equations

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Standard Enthalpy of Formation

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Spontaneity

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Entropy

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Standard Entropy Change for a Reaction

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CHEM.13.A

Constant Pressure Calorimetry

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Constant Volume Calorimetry

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CHEM.13.B

CHEM.13.C

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Science concepts. The student understands the energy changes that occur in chemical reactions. The student is expected to:

How Temperature Changes Create Stress

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