Coefficients of best-fit polynomial approximation of thermal strain for various materials, approximated as ɛ = a4T4 +a3T3 +a2T2 +a1T, where R2 is the coefficient of determination. The zero-order term of thermal strain is omitted, since it represents a shift in strain, and is the only term dependent on the initial condition of the experiment. Furthermore, this term is typically not taken into account in solid mechanics analyses. Following Eq. (2), the thermal expansion coefficient is: β = 4a4T3 +3a3T2 +2a2T +a1