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

신체는 온도 변화를 겪을 때 스트레스를 경험합니다. 이 스트레스는 열 스트레스로 알려져 있으며, 이는 신체를 영구적으로 변형시킬 수도 있습니다.
예를 들어, 철로에 있는 막대의 두 관절 사이에 막대의 변형 또는 굽힘을 방지하기 위해 의도적으로 공간을 유지합니다.
물체의 열 응력을 계산하려면 먼저 열 팽창 또는 수축을 결정한 다음 응력을 계산합니다.
길이가 L0인 막대를 고려하십시오.입니다. 열이 가해지면 로드의 길이가 델타 'L'만큼 확장되고 로드 길이의 분수 변화를 평가할 수 있습니다.
이제 동일한 막대가 양쪽 끝에 고정됩니다. 열이 가해지면 막대가 팽창할 수 없기 때문에 변형이 발생합니다. 막대의 원래 길이를 복원하기 위해 응력을 계산할 수 있습니다.
Young의 계수의 정의를 상기하면 응력에 대한 변형률의 비율입니다.
따라서 열 응력은 방정식을 결합하고 항을 재배열하여 결정할 수 있습니다.

<ol>
	<li>오픈스택스. (2019). 대학 물리학 Vol. 2. [웹 버전]. 원본 주소 <a href="https://openstax.org/details/books/university-physics-volume-2">https://openstax.org/details/books/university-physics-volume-2</a>; 18–19쪽.</li>
</ol>

열 응력

물체의 팽창이나 수축이 억제된 상태에서 온도가 변하면 물체는 응력을 받게 됩니다. 물체가 구속 없이 팽창하면 응력은 압축성이고 수축하면 인장력이 됩니다. 온도 변화로 인해 발생하는 이러한 응력을 열 응력이라고 합니다. 크기가 꽤 커서 손상을 일으킬 수 있습니다. 이러한 스트레스를 피하기 위해 엔지니어는 구성 요소가 자유롭게 확장 및 축소될 수 있도록 설계할 수 있습니다. 예를 들어, 고속도로에서는 열 응력이 발생하는 것을 방지하기 위해 의도적으로 블록 사이에 틈을 남겨 둡니다. 간격을 둘 수 없는 경우 엔지니어는 설계 시 열 응력을 고려해야 합니다. 따라서 콘크리트의 철근은 강철의 선팽창계수가 콘크리트의 선팽창계수와 거의 동일하기 때문에 강철로 만들어집니다.

열 스트레스는 얼음이 얼 때 얼음이 팽창하여 암석이나 포장 도로가 풍화되는 것과 같은 많은 현상을 설명할 수 있습니다. 철로와 도로는 신축 이음 장치가 충분하지 않으면 더운 날에 휘어질 수 있고, 느슨함이 부족하면 전력선이 겨울보다 여름에 더 처지고 추운 날씨에 끊어질 수 있습니다. 집이 따뜻해지고 식으면서 석고 벽에 균열이 생겼다가 닫힙니다. 유리 요리 팬은 수축 차이와 그에 따른 응력으로 인해 급격하게 또는 고르지 않게 냉각되면 깨질 수 있습니다.

물체가 팽창하거나 수축하지 않는 동안 물체의 온도가 변하면 물체에 응력이 가해집니다. 스트레스는 ...

Education

교육

JoVE Core

Physics

물리학

Unit 1

제1단원

Temperature and Heat

온도와 열

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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...

zeroth law of thermodynamics

Thermal Equilibrium and the Zeroth Law

The zeroth law of thermodynamics explains thermal equilibrium between objects. If object A is in equilibrium with object B, and object B is in equilibrium with object C, then object A is also in equilibrium with object C. This transitive relationship is the key idea behind the law. A simple example uses metal blocks and a metal plate at room temperature. A cold metal block and a hot metal block are both placed on the plate. Over time, the cold block and the plate reach thermal equilibrium, and...

thermometers and temperature scales

How Thermometers Measure Heat

Thermometers measure temperature by using physical properties that change in a predictable way. One common example is volume. For most substances, volume increases as temperature rises. That idea is used in alcohol thermometers and in the original mercury thermometers. Other thermometer designs use different temperature-sensitive properties. Some measure electrical resistance, color, or the emission of infrared radiation. The alcohol thermometer is a common example. It contains red-dyed...

gas thermometers and the kelvin scale

Kelvin Temperature and Gas Thermometer Standards

Kelvin temperature is the absolute scale used in science, and it starts at absolute zero. That zero point matches the lowest possible temperature, where molecular motion reaches zero or the minimum allowed by quantum mechanics. Scientists use this scale because some physical quantities, such as the volume of an ideal gas, depend directly on absolute temperature. The Kelvin scale is part of the SI system of units, so its definition is more precise than simply using water’s freezing and boiling...

thermal expansion

Thermal Expansion in Air, Water, and Solids

Thermal expansion is the change in size or volume of a material as its temperature changes. A common example is the alcohol inside a thermometer. As the temperature rises, the alcohol expands and shows the change. Heated air also expands. It becomes less dense than the cooler air around it, so the surrounding air pushes it upward. This is why steam and smoke rise and why hot air balloons float. The same effect happens in liquids and gases, and it helps move heat upward in homes, oceans, and...

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

Thermal expansion and thermal stress are shown through the Golden Gate Bridge. The bridge faces temperatures from -15 °C to 40 °C. At its coldest, the main span is 1275 m long. Assuming the bridge is made entirely of steel, the example asks for the change in its length across this temperature range. To solve the problem, the known values must be identified first. The initial length is 1275 m. The coefficient of linear expansion for steel is 12 x 10 -6 /°C, and the change in temperature is 55...

heat flow and specific heat

Heat Units and Specific Heat

Heat is energy transferred because of a temperature difference, and it can change an object’s temperature. Since heat is energy, its SI unit is the joule (J). Heat transfer is the movement of energy from one place or material to another, and it plays a role in home heating, cooking, and many industrial processes. Two common units for heat are the calorie and the kilocalorie. A calorie (cal) is the energy needed to change the temperature of 1 g of water by 1 °C, specifically between 14.5 °C and...

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

Three Ways Heat Moves Between Objects

Heat transfer happens when there is a temperature difference. It can move fast, like through a cooking pan, or slowly, like through the walls of a picnic ice box. Heat transfer appears in many everyday situations, so it is hard to find a place where it does not occur. There are only three ways heat is transferred: conduction, convection, and radiation. A fireplace shows all three at once. Radiation carries most of the heat into the room. Conduction also moves heat into the room, but much more...

mechanisms of heat transfer ii

Convection and Radiation in Heat Transfer

Convection and radiation are two major ways heat moves. In convection, thermal energy is carried by the large-scale flow of matter. Warm air and water rise because they are less dense, so ocean currents and large-scale atmospheric circulation move heat from the tropics toward the poles and move cold air from the poles toward the tropics. Earth’s rotation changes these moving air currents. It interacts with the flow and helps produce the eastward movement of air in the temperate zones.

conduction, convection and radiation: problem solving

conduction-convection-and-radiation-problem-solving

Heat Transfer Calculations with Conduction, Convection

Heat transfer calculations with conduction and convection use the temperature difference to find the rate of heat flow. Radiation can also be part of the process. The main idea is that heat moves only because one area is hotter than another, and a larger temperature difference leads to faster transfer. To solve a heat transfer problem, first identify the type of transfer involved. It may be conduction, convection, radiation, or a combination of all three. Next, write down the unknown...

radiation: applications

Earth’s Energy Balance and Greenhouse Effect

Earth’s energy balance and the greenhouse effect help explain its average temperature. Earth is in radiative contact with both the Sun and dark space. It receives almost all of its energy from solar radiation, and it reflects some of that energy back into outer space. Dark space is very cold, about 3 K, so Earth also radiates energy into it. Heat can move quickly from soil and grasses, and frost can form on clear summer evenings, even in warm latitudes. In a first approximation, Earth’s...

absorption of radiation

Radiation Heat Transfer and Thermographs

Radiation heat transfer depends on temperature, surface area, and emissivity. The Stefan-Boltzmann law describes the rate of heat transfer by emitted radiation. In this law, σ is the Stefan-Boltzmann constant, A is the object’s surface area, and T is its temperature in kelvins. The fourth-power dependence on absolute temperature makes radiation highly sensitive to small temperature changes. Even a slight rise in temperature can change the emitted heat a lot. That sensitivity is why radiation...

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.

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CHEM.13.A

Constant Pressure Calorimetry

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CHEM.13.B

CHEM.13.C

Temperature and Thermal Equilibrium

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Heat is a type of energy transfer that is caused by a temperature difference, and it can change the temperature of an object. Since heat is a form of ...

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The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. ...

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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