Thermal shock, test methods

Olbrich, M., Fully automated thermal shock test method for testing fired refractory brick , Radex-Rundschau, 1990 (2/3) 268-74. 

Absi, J., Glandus, J.C. (2004), Improved method for severe thermal shocks testing of ceramics by water quenching , J. Eur. Ceram. Soc., 24(9), 2835-2838. 

We proposed a new test method to evaluate the thermal shock resistance of epoxy resin (7). This test method uses a notched-disk specimen, and the thermal shock resistance can be evaluated analytically on the basis of linear fracture mechanics (8). In our previous studies, we reported on the use of our proposed thermal shock test and evaluation methods (8, 11) to determine the thermal shock resistance of toughened epoxy with a soft second phase (9, 10), and also with hard particulates (11). 

Evaluation of Thermal Shock Resistance. The results of the thermal shock tests are evaluated by the method based on fracture mechanics. Thermal shock resistance (ATc)cai, can be calculated as follows (8,10) ... 

Find et al. [25] developed a nickel-based catalyst for methane steam reforming. As material for the microstructured plates, AluchromY steel, which is an FeCrAl alloy, was applied. This alloy forms a thin layer of alumina on its surface, which is less than 1 tm thick. This layer was used as an adhesion interface for the catalyst, a method which is also used in automotive exhaust systems based on metallic monoliths. Its formation was achieved by thermal treatment of microstructured plates for 4h at 1000 °C. The catalyst itself was based on a nickel spinel (NiAl204), which stabUizes the catalyst structure. The sol-gel technique was then used to coat the plates with the catalyst slurry. Good catalyst adhesion was proven by mechanical stress and thermal shock tests. Catalyst testing was performed in packed beds at a S/C ratio of 3 and reaction temperatures between 527 and 750 °C. The feed was composed of 12.5 vol.% methane and 37.5 vol.% steam balance argon. At a reaction temperature of 700°C and 32 h space velocity, conversion dose to the thermodynamic equilibrium could be achieved. During 96 h of operation the catalyst showed no detectable deactivation, which was not the case for a commercial nickel catalyst serving as a base for comparison. 

Quendi Tests. See thermal shock tests. Quenching of Frit. Molten glaze-frit or enamel-frit is quenched to break it up, thus making it easier to grind. The simplest method is to allow the stream of molten frit to fall into water, but this does not give uniform quenching and fracture. Better methods are to expose the stream of molten frit to a blast of air and water, or to pass the stream between water-cooled rolls the latter process gives a flaky product. 

There are many methods to measure thermal shock resistance. The most cmivenient are quenching heated material - water and heated material — air. In order to simulate the specific service conditions of refractories, several other methods of thermal shock testing have been investigated. 

There are two standard methods for determining the thermal shock resistance of refractory materials. For brick shapes, thermal shock resistance is measured by Ribbon Thermal Shock Testing (ASTM C-1100), and for monolithic refractories the standard method is ASTM C-1171. These tests clearly differentiate among refractory materials about their resistance to thermal shocks. 

Data for thermal movement of various bitumens and felts and for composite membranes have been given (1). These describe the development of a thermal shock factor based on strength factors and the linear thermal expansion coefficient. Tensile and flexural fatigue tests on roofing membranes were taken at 21 and 18°C, and performance criteria were recommended. A study of four types of fluid-appHed roofing membranes under cycHc conditions showed that they could not withstand movements of <1.0 mm over joiats. The limitations of present test methods for new roofing materials, such as prefabricated polymeric and elastomeric sheets and Hquid-appHed membranes, have also been described (1). For evaluation, both laboratory and field work are needed. 

The impact of thermal shock on the properties of a ceramic or a CMC is assessed by means of both destructive and non-destructive testing methods. Flexural or tensile (mainly for CMCs) tests of suitably-sized thermally shocked specimens are usually employed to measure retained mechanical properties as a function of the temperature difference. The temperature differential for which a significant drop in property values is observed is the A A- For monolithic ceramics and particle- or whisker-reinforced CMCs the property under investigation is usually strength, whereas in fibre-reinforced CMCs a drop in Young s modulus is usually a better indication of the onset of damage. 

There is no evidence of delamination, corrosion, or other visual changes for TFML structures subjected to MIL-STD-883C tests for temperature cycling (-65°C to 150 C, 100 cycles), thermal shock (-55°C to 125°C, 15 cycles), moisture resistance (Method 1004.5), and accelerated aging at 85 C/85 percent r.h. for 1000 hours (unpublished results) ... 

C1525-02 Test Method for Determination of Thermal Shock Resistance for Advanced Ceramics by Water Quenching... 

Kubouchi et al [17] have devised a test method to assess thermal shock resistance, in which a sharply notched disk 60mm in diameter and 10mm thick is transferred from a hot oven to a cooling bath, while thermally insulated on both flat sides. A thermal shock fracture toughness term, A l.., is obtained for the fllled resin. 

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