Simulación numérica de ensayos de compresión diametral para la evaluación de discos cerámicos porosos

Abstract

Se estudió el comportamiento mecánico de materiales porosos de cordierita mediante ensayos en compresión diametral. La solución analítica que permite la medición indirecta de la resistencia mecánica a tracción en compresión diametral se formula bajo ciertas condiciones que no suelen satisfacerse en la práctica. Con el objetivo de analizar desviaciones de las condiciones ideales se simuló el ensayo con técnicas computacionales. Los discos porosos de cordierita se obtuvieron por calcinación (650 °C, 2h) y reacción-sinterización (1330 °C, 4h) de cuerpos en verde preparados por consolidación térmica (85 °C, 4h) de suspensiones acuosas de una mezcla precursora de cordierita (caolín, talco y alúmina) con almidón nativo de papa. Los ensayos mecánicos se realizaron en una máquina servohidráulica en control por desplazamiento (0,2 mm/min). A partir de la relación aparente tensión-deformación se determinaron los parámetros mecánicos: módulo de Young aparente, resistencia mecánica y límite elástico. Sobre los discos ensayados se analizaron las características de la fractura. La influencia de las desviaciones geométricas más frecuentes identificadas en la práctica (desviación de la circularidad y no paralelismo entre las caras del disco) sobre la distribución de tensiones se estudió mediante la simulación por elementos finitos, tomando como referencia la ecuación de Hertz para problemas de contacto. Palabras claves: Compresión diametral, Simulación numérica, Cerámicos porosos, Cordierita. Numerical simulation of diametral compression tests for the evaluation of porous ceramic disksThe mechanical behavior of porous cordierite materials was studied by diametral compression tests. The analytical solution allowing the indirect measuring of the tensile mechanical strength in this load configuration is formulated under certain assumption which may be not satisfied in practice. With the aim to analyze deviations of the ideal conditions, the test was simulated using computational techniques. Porous cordierite disks were prepared by firing (650 °C, 2h) and reaction-sintering (1330 °C, 4h) of green disks shaped by thermogelling the aqueous suspensions of a cordierite precursor mixture (kaolin, talc and alumina) with native potato starch as a consolidator/binder of ceramic particles and a pore former by burn-out at high temperature. The mechanical tests were carried out in displacement control (0.2 mm/min) using a servohydraulic testing machine. From the apparent stress-strain ratio, the following parameters were determined: mechanical strength, apparent Young modulus and yield stress. Fracture features of tested disks were also analyzed. The influence of the geometrical deviations more usually identified in practice (deviation of the circularity and no parallelism between the plane surfaces of the disk) on the stress distribution was studied by means of the simulation by finite element method, considering the Hertz´s equation for contact problems as reference.

Starch Consolidation Casting of Cordierite Precursor Mixtures—Rheological Behavior and Green Body Properties

“…Also clay‐based materials, and, very recently, porcelain foams have been prepared using starch consolidation casting. At the same time, processing details as well as process optimization and material characterization issues of starch consolidation casting were further investigated for alumina and cordierite . While in the first applications of starch consolidation casting to cordierite modified potato starch (modified by hydroxypropylation and crosslinking) has been used, the aforementioned later research was primarily focused on the use of native potato starch and native and modified cassava (tapioca) starches.…”

“…At the same time, processing details as well as process optimization and material characterization issues of starch consolidation casting were further investigated for alumina [15][16][17][18][19][20][21][22][23][24] and cordierite. [25][26][27][28][29] While in the first applications of starch consolidation casting to cordierite 2 modified potato starch (modified by hydroxypropylation and crosslinking) has been used, the aforementioned later research [25][26][27][28][29] was primarily focused on the use of native potato starch and native and modified cassava (tapioca) starches. It is one of the aims of this study to fill this gap and to provide a complex comparison of the performance of native corn starch for this purpose with that of native potato starch.…”