Two-D Analysis of the Thermo-Mechanical Properties of ZrO2-Based Composites

Two-D Analysis of the Thermo-Mechanical Properties of ZrO2-Based Composites

Sedigheh Salehi (Katholieke Universiteit Leuven, Belgium), Vasyl Ryukhtin (Helmholtz-Zentrum Berlin for Materials and Energy, Germany), Petr Lukas (Nuclear Physics Institute, Czech Republic), Omer Van der Biest (Katholieke Universiteit Leuven, Belgium) and Jef Vleugels (Katholieke Universiteit Leuven, Belgium)
DOI: 10.4018/ijcce.2012010103
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Abstract

In this paper, a fast and efficient tool for predicting a set of physical and mechanical composite properties such as thermal expansion coefficients, thermal and electrical conductivity, stiffness, and thermal residual stress is developed based on the analysis of a representative volume of ZrO2-based composite. Such an analysis allows an engineer to assess the mechanical and physical properties to design an optimum composite composition in terms of advantageous mechanical properties and at the same time a good electrical discharge machining performance. Thermal residual stresses in the constituent phases and thermal and electrical conductivity of ZrO2-based composites are assessed by a Finite Element (FE) model using 2 dimensional SEM micrographs. The FE models are verified by comparing numerically calculated results with experimentally measured data.
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2. Experimental Procedure

The density of the samples was measured in ethanol, according to the Archimedes method. The electrical resistivity of the samples was measured according to the 4-point contact method. The elastic modulus, E and Poisson ratio, υ, of the ceramics was measured using the resonance frequency method (ASTM, 1994). The resonance frequency was measured by the impulse excitation technique.

The thermal expansion coefficient of the samples was determined with commercial thermomechanical analyser equipment (model Q400, TA Instruments, USA). Experiments were conducted in a temperature range from 25 to 900°C with a heating and cooling rate of 2°C/min on rectangular shaped samples of about 2024 mm3 with ground parallel lateral surfaces. The TA instrument was calibrated with a pure aluminium test sample from room temperature up to 500°C.

Thermal residual stresses through the thickness of the ceramic discs (434 mm) were measured by neutron diffraction. The neutron diffraction experiments were performed on the high-resolution SPN100 neutron stress scanner available at the medium-power reactor LVR-15 at NPI in Řež (Czech Republic).The measurement method is based on an experimental examination of the two components of the lattice strain tensor and conversion of the measured lattice strains to stresses (Lukáš, 2005). Expansion or contraction of the lattice constant compared to measured lattice constant on pure phases is translated to residual thermal stresses due to mismatch between thermal expansion coefficients of constituents in the composite.

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