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
Motion of two bodies - rough surface and rough pulley: THE HORIZONTAL SURFACE IS ROUGH AND THE STRING IS PASSING OVER ROUGH PULLEY. Figure shows two weights W 1 and W 2 c

The total resistance of the system between the electrodes consists of (i) The resistance of the work piece R 1 (ii) The contact resistance between the electrodes and the wo

The layout of a transmission shaft carrying two pulley C and B and supported on bearings A and D is shown in figure. Power is supplied to the shaft by means of vertical belt on pul

CO 2 Gas Supply The CO 2 shielding gas is supplied cylinders at high pressure (140 kg / cm 2 ). Therefore pressure regulator and flow meter are connected to reduce the pressu

Clausiu s statement: It is impossible to construct this type of H.P. which operates on cyclic process and allows transfer of heat from colder body to a hotter body without th

Performance of Heat engine: Performanc e of HP:   It is measured by thermal efficiency that is the degree of useful conversion of heat received into work.

I need a symbol for push and turn

Paved Dips: Paved dips, also known as bed level causeways, are structures consisting of gentle and shallow depressions in the road where the water is allowed to flow over the

A helical compression spring prepared of oil tempered carbon steel, is subjected to a load which goes from 600 N to 1600 N. The spring index is 6 and the design factor of safety is

Define stress: Sol.: When body is acted upon by load or external force, it undergoes deformation (that is, change in shape or dimension) which increases gradually. At the ti