Quality Control and Thermal Shock Damage Characterization of High‐Temperature Ceramics by Ultrasonic Pulse Velocity Testing

Abstract

Ultrasonic pulse velocity testing was carried out to perform nondestructive quality control of refractory plates used as substrates in fast firing of porcelain whiteware. Two cordierite‐mullite refractory compositions characterized by different microstructure morphologies and crack propagation behavior were investigated after a number of industrial thermal cycles. Ultrasonic velocity measurements were used to determine the presence of internal voids/cracks in the samples, originating from the manufacturing procedure. A brief discussion about the correlation between microstructure, crack propagation behavior, and thermal shock resistance is presented. Empirical models were developed to predict the service life of refractory plates from measured values of ultrasonic velocities on as‐received samples.

Assessment of viscoelastic crack bridging toughening in refractory materials

“…Longer cracks will propagate at higher crack-growth rates, as demonstrated in Ref. 12 In many of the investigated samples, cracks are already visible after approximately 100 cycles, with crack lengths higher than 1 mm. 11 The retained strength after 110 cycles is approximately 90% for BRT material while RSE material retains only 70%.…”

Experimental analysis of the evolution of thermal shock damage using transit time measurement of ultrasonic waves

“…by (microscopic) examination of the crack pattern, 18,28,31,[33][34][35]45 recording the number of test cycles or the quenching temperature difference to reach material failure, 1,2,32 by determination of the residual mechanical properties 1, [3][4][5][8][9][10]25,[36][37][38][39]42 and of the weight loss after layer-wise spalling. 43 Other characterization techniques rely on the measurement of acoustic emission during thermal shock 11,22,24,26,44,46,47 and the determination of the change in sound velocity, 40,48,49 attenuation 48 and resonance frequency 6,16,20,29 due to thermal shock. The described methods characterize the material state of an entire test sample and thus only allow for a qualitative ranking of materials.…”

“…36 For this purpose also electrical induction, 37 resistance 38 and discharge 39 have been used on refractories containing carbon. Milder up-quenching was achieved using a hot furnace atmosphere, [40][41][42][43] infrared heaters 44 and hot compressed gas. 45 Due to the poor reproducibility of the heat transfer conditions most of the aforementioned test methods do not qualify for the use in a model parameter estimation process.…”

Ultrasonic characterization of defective porcelain tiles

“…Measurement procedures initially developed for metals have been extended to engineered materials, such as composites, where anisotropy and homogeneity have become important issues (4). The determination of ultrasonic velocities can be used to measure the modulus of elasticity or Young's modulus of materials, monitor the development of thermal shock damage, characterize indirectly fracture toughness, R-curve behavior, hardness depending on heat treatment, volume fraction porosity and density (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Recently, the ultrasonic test has also been used to detect internal flaws in ceramics and other materials (22).…”