Thermal properties-ceramics-refractory and abrasive material, Mechanical Engineering

Thermal Properties

Each solid expand on heating and convention on cooling. The thermal expansion of solids is due to basic structure whether atoms occupy mean position on a fixed distance from each other. In actual fact atoms are not stationary but vibrate about mean location or positions which changes along with temperature. The distance in between mean positions rises along with increasing temperature and reduces along with temperature. Such changes in the mean distance in between the atoms result in contraction or expansion. Coefficient of linear expansion is explained as the raise in length per till length per degree rise in temperature. For reduces in temperature similar property is regarded as -ive . The linear changes in three mutually perpendicular directions will constitute volume expansion coefficient. If the linear expansion coefficients in three orthogonal directions are equivalent then the solid is thermally isotropic. The thermal expansion is zero on absolute zero temperature and is usually related to exact heat and melting point of a substance.

This is interesting to notice that experiments express that total volume change on heating among absolute zero and melting point is same for each element. This implies that thermal expansion coefficient is low for high melting point solids. Most solids that are utilized for high temperature applications that are refractory materials have linearly varying thermal coefficients. The exception is silica as SiO2 and zirconia ZrO2 which due to polymorphic transformation implies irregular behaviour.

The coefficient of thermal expansion is significant consideration though designing structure to operate at high temperature. The limited deformations will reason forces to act upon the part and hence induce stresses. Further throughout moulding procedure proper care require to be exercised for volume's due consideration and linear changes after solidification hence dimensional accuracy and tolerances might be maintained. Apparently this consideration supposes greater significance in case of such materials that are not easy to machine. Ceramics and further refractory materials are illustrations.

                                   1809_Thermal properties.png

Figure: Thermal Expansion of Refractory Oxides as Function of Temperature

The coefficient of plastics of expansion might be controlled by addition of filler material; usually increasing filler material would reduce the coefficient. Expansion in instance of reinforced plastics tends to arise in the direction of reinforcement. There are a lot of plastics utilized in conjunction along with metals of common employ and it might be noted that employ of fillers enable material engineer to control the coefficient such plastic and metal expand equally. Unequal expansion will initiate undesirable deformation and stresses.

Posted Date: 2/27/2013 1:34:09 AM | Location : United States

Related Discussions:- Thermal properties-ceramics-refractory and abrasive material, Assignment Help, Ask Question on Thermal properties-ceramics-refractory and abrasive material, Get Answer, Expert's Help, Thermal properties-ceramics-refractory and abrasive material Discussions

Write discussion on Thermal properties-ceramics-refractory and abrasive material
Your posts are moderated
Related Questions
What are wall footings? Explain in short. Generally wall footings are required to support direct concentric loads. However, an exception is the wall footings for retaining wall

What is drilling machine The machine used for drilling is called drilling machine. The drilling operation can also be accomplished in lathe, in which the drill is held in ta

Part Contact States The loading, movement and unloading of parts via the manufacturing system should be scheduled through supervisory computer. In contrast along with classical

Total decrease in length: Q: A hollow cast iron cylinder 4 m long, 300 mm is the outer diameter, and thickness of metal 50 mm is subjected to central load on top when standin

Tensile strength: What will be its ultimate tensile strength? Solution The condition for necking is = n = 0.3077 Hence using this value of , the true stress at ne

this is a problem for designing wrecking crane. there are 2 scenarios, one is when ball is held and one where its at maximum. i calculated the loads and now need to find the follow

Specifi c Heat: The specific Heat of a solid or liquid can be usually defined as heat required for raising unit mass through one degree temperature rise. That is,   dQ = m

Bucket conveyors are used to moves the granular powdered or liquid materials. The buckets may be mounted on a chain or a belt. The movement may be vertical or flat. The ver