Effect of porosity on the crack pattern and residual strength of ceramics after quenching

Abstract

The effect of porosity on the crack characteristics of ceramics after water-quenching is studied by measuring the cracks in ceramic sheets. The result reveals that the pore volume fraction has a slight effect on the enhancement of thermal shock resistance of ceramics when the porosity ranges from 0 to 20 %, because the length and density of the long crack in porous alumina are always slightly less than that in dense alumina. This result is in agreement with the prediction based on the minimum potential energy principle using experimentally measured data. Moreover, the proportion of the strength reduction in the third regime decreases significantly with increasing porosity, because the strength of unquenched specimens decreases more rapidly than that of quenched specimens with increasing porosity. The results of this study may help to further understand the thermal shock behavior of ceramics.

Fractal characterization of ceramic crack patterns after thermal shocks

“…Inspired by Bahr's research works, in the last decade, many researchers studied crack patterns after thermal shocks, in order to reveal mechanisms between residual strength and crack characteristics . For thin ceramic specimens, Shao conducted thermal shock testing in the temperature range higher than the critical thermal shock temperature difference (Δ T c ) and showed that the depth of long crack was gradually increased in regime III, which supported the standpoint of Davidge and Bahr, although Hasselman had opposite results.…”

Influence of ZrO2 Content on the Performances of BN‐ZrO2‐SiC Composites for Application in the Steel Industry

“…However, the pore volume fraction has a slight effect on the enhancement of thermal shock resistance, especially when the porosity of ceramic composite is <10%. 26 Secondly, the changing trends of mechanical properties also have an efficient influence on the thermal shock resistance. In theory, models of thermal shock behavior usually fall into two categories: one is thermal stress fracture resistance parameter, R, and the other one is the thermal stress damage resistance parameter, R IV .…”

“…It is attributed that the cracks must spread out around pores and do not simply cut through them when some pores exist in the composite, the crack propagation requires more fracture energy due to stress field relaxation and crack‐tip deflection. However, the pore volume fraction has a slight effect on the enhancement of thermal shock resistance, especially when the porosity of ceramic composite is <10% …”

Influence of silver nanoparticle addition, porosity, and processing technique on the mechanical properties of Ba0.3Co4Sb12 skutterudites

“…Note that fracture toughness was not measured for specimens PM-HP-673 (P = 0.30) or PM-HP-673-Ag (P = 0.27) since these specimens were too fragile to be polished. In the literature, it has been noted that K C can increase, decrease, or remain unchanged with increasing P [59,68].…”