Alumina disks with different surface finish: thermal shock behavior

Indentation crack profiles of cordierite materials under mechanical and thermal biaxial stresses

“…1,13,14 The specimen mounted horizontally on a refractory material with the indented upper surface, was heated in an electric furnace up to a predetermined temperature (T i ) and allowed to equilibrate for 90 min. Then, it was subjected to a sudden cooling using a high velocity air jet at room temperature (T 0 = 26-27 • C) channelled by a silica tube (inner diameter: 3.58 ± 0.02 mm, 90 • and 3 mm above the surface) for 20 s. After quenching, the specimen was cooled up to room temperature and examined for crack extension from the original indentation crack.…”

Fracture Analyses of Alumina Subjected to Mechanical and Thermal Shock Biaxial Stresses

“…Both C and F materials were tested in specific mechanical and thermal shock conditions, which produced similar equibiaxial stress distributions on the surface of the disk. [5][6][7] Namely, the fracture strength was evaluated in biaxial flexure, employing a ball on discontinuous ring fixture (ball diameter, 8.04 Ϯ 0.02 mm; ring diameter, 19.50 Ϯ 0.1 mm) in a servohydraulic testing machine (Model 8502, Instron Corp., Danvers, MA) at a displacement rate of 0.05 mm/min. The fracture strengths ( F ) were higher for the C specimens (296 Ϯ 59 MPa (fifteen specimens)) than for the F specimens (220 Ϯ 66 MPa (twenty specimens)).…”

“…In thermal shock condition, each specimen was suddenly cooled using a high-velocity air jet at room temperature (20 s) until cracking was detected. 7 The air was channeled onto the center of the machined surface of the disk using a silica tube (tube diameter/disk diameter ϭ 0.1). The thermal shock resistance ⌬T C 7 determined was higher for the F disks (916 Ϯ 90°C (20 specimens)) than for the C disks (765 Ϯ 88°C (eleven specimens)).…”

“…Disks with C machining showed a better mechanical response than F specimens, but the opposite occurred when they were tested under thermal shock conditions. 7 The influence of the machined surface features (microstructure, surface roughness, and residual stresses) on these properties was analyzed elsewhere. [5][6][7]…”

New Method to Measure Thermal Shock Resistance in Ceramics Using a Piezo‐Spectroscopic Technique

“…Several methods have been proposed [1][2][3][4][5][6] and the results are directly related to the method used. In order to overcome this inconvenience, an international agreement has established a conventional standardized method.…”