Crack patterns corresponding to the residual strength plateau of ceramics subjected to thermal shock

Abstract

The formation mechanism of the residual strength plateau of ceramics subjected to thermal shock is addressed.A set of thermal shock experiments of 99Al 2 O 3 are conducted, where the thin specimens of 1 mm × 10 mm × 50 mm exhibit parallel through edge cracks, and thus permit quantitative measurements of the crack patterns. The cracks evolve with the severity of thermal shock. It is found that there is a correlation between the length and density of the thermal shock cracks. The increase of crack length weakens the residual strength, whereas the increase of crack density improves it. In a considerably wide temperature range, the two contrary effects just counteract each other; consequently a plateau appears in the variation curve of the residual strength. A comparison between the numerical and experimental results of the residual strength is made, and they are found in good agreement. This work is helpful to a deep understanding of the thermal shock failure of ceramics.

Fast heating thermal shock test for β-SiAlON with molten metals as heating medium

“…According to the thermal transient types, existing thermal shock resistance test methods can be divided into two categories: a sharp decline of temperature for quenching tests and an increase of temperature for fast heating methods. In the quenching test, a specimen is first heated to a certain temperature in a furnace, and then the temperature is decreased quickly by (1) putting the specimen into a quenching medium [1][2][3][4][5][6][7][8][9][10], (2) blowing high velocity cold air onto the specimen [10,11], (3) cooling down in air spontaneously [12] and (4) contacting the specimen with a cold metal rod [13], or other quenching methods. In the fast heating test, a specimen is quickly heated by a heating source [14][15][16][17][18][19][20][21][22].…”

“…The temperature of the components will increase instantaneously and the components will be damaged by the temperature increase [23]. However, a quenching thermal shock test (QTST) with room temperature water is typically performed to evaluate the thermal shock resistance of ceramics due to the simple equipment and operation [4][5][6]. Obviously, a QTST may not evaluate thermal shock resistance appropriately for the differences between the working and simulated conditions.…”

Coupled Thermomechanical Multiscale Modeling of Alumina Ceramics to Predict Thermally Induced Fractures Under Laser Heating

“…Due to their high‐temperature resistance, alumina ceramics are highly desired for components of engineering structures and systems in a wide spectrum of applications. Such materials are often exposed to extreme conditions with severe thermal loading with a rapid change in temperature, that is, thermal shock . Moreover, the fabrication processes of alumina ceramics like laser machining or laser‐assisted machining always cause great thermal gradients within the alumina workpieces.…”

“…Such materials are often exposed to extreme conditions with severe thermal loading with a rapid change in temperature, that is, thermal shock. 1,2 Moreover, the fabrication processes of alumina ceramics like laser machining or laser-assisted machining always cause great thermal gradients within the alumina workpieces. The induced thermal stresses could exceed the strength of alumina ceramics, causing cracks to form and might further lead to catastrophic failure.…”

Refratários magnesianos de panela de aciaria: redução da oxidação inicial, formação da fase espinélio MgAl₂O₄ e resistência ao dano por choque térmico

“…Os parâmetros de resistência ao choque térmico e ao dano por choque térmico (R''' e R'''') e a relação entre ϒ wof /ϒ i são os melhores indicadores sobre a resistência a propagação de trincas e podem ser usados para prever ou comparar desempenhos de refratários, após os ensaios de choque térmico (YURKOV et al, 1997;BRADT, 2003) A literatura reporta que para os refratários MC e AMC a quantidade, distribuição e o tamanho das partículas de espinélio presentes no refratário alteram de maneira decisiva o comportamento frente ao choque térmico, bem como à formação distribuída e continua desta fase no interior do volume do refratário (HASSELMAN, 1969(HASSELMAN, , 1985HOU et al, 2012 …”