セラミックスの合成と評価 反力測定を利用した急速加熱熱破壊試験法における温度分布の相関式と熱応力の算出

Abstract

In the thermal fracture testing technique proposed previously by the present authors, a one-side heated slab specimen is held by three points and the repulsive load appearing during heating is measured by the load cell placed at the upper point of the heated side. By this way, the thermal fracture stress of a ceramic specimen can be estimated from the repulsive load without knowing the heat transfer coefficient unlike the water quenching thermal shock test. However, it needs numerical calculation for every specimen at each experimental condition.In this paper, the numerical calculation of non-steady-state temperature distribution in an infinite plate, heated from one side with a constant heat flux were conducted in order to calculate the magnitude of thermal stress from the repulsive load data in the above-mentioned thermal fracture test. The temperature dependences of thermal conductivity, λ*=eAT and thermal diffusivity κ*=eBT were introduced in the calculation to realize a practical heat conductive condition. The time dependent temperature distributions were unified into a correlative equation that includes the coefficients of temperature dependence of material properties A, B, supplied heat flux Qi and Fourier's number ηi=κit/h2. By using this equation, the repulsive load and thermal stress at fracture were calculated for several ceramics, and the influences of material properties were discussed. The correlative equation is also useful to define the experimental conditions in thermal fracture tests.