The thermal properties of an engineering material primarily refer to the characteristic behaviors of the material under thermal load. For example, thermal conductivity is a measure of the ability of material to conduct heat and is expressed as W.K-1.m-1 in SI unit. The specific heat refers to the measure of energy that is required to change the temperature for a unit mass and is expressed as J.kg-1.K-1. The product of density and specific heat is often referred to the heat capacity of a unit mass of material. The thermal diffusivity refers to the ratio of thermal conductivity and heat capacity of a material and provides a measure the rate of heat conduction. The thermal diffusivity is expressed in terms of m2.s-1.
When a material is subjected to both thermal and mechanical loading, two more characteristics of materials - coefficient of thermal expansion and thermal shock resistance - become significant.
The coefficient of thermal expansion provides a measure of unit change in strain of a material for unit change in temperature and is expressed in terms of K-1 in SI unit. The thermal strain in material is considered to be isotropic in nature. The thermal shock resistance provides a measure to which a material can withstand an impact load which is either thermal or thermo-mechanical in nature. The thermal shock resistance is expressed as  , where K is the thermal conductivity, σT maximal tension the material can resist, α the thermal expansion coefficient, E the Young’s modulus and ν the Poisson’s ratio. |
