Shock test

Mechanical Properties. Most of electronic IC devices are very fragile. They need strong mechanical protection from the encapsulant to retain their long-term reUabiUty. Encapsulant must provide mechanical protection but still maintain good temperature-cycle and thermal-shock testing, which are part of the routine reUabiUty testing of the embedding electronics. 

The shocks that measuring devices are subjected to are. generally cliaracterized by art acceleration (or deceleration), and a time span. For example, a device is said to withstand 500 g (5,000 m/s ) for lb ms. This refers to a half-sine. Shock testing machines produce a deceleration impulse having the form shown in Figure 4. 2.S7..., , , ... 

Rhovanil fine mesh vanillin, 25 550, 552 Rhovanil free flow vanillin, 25 550 Ribbon silicon, 23 40-41 Ribbon Thermal Shock Test, 21 513 Ribbon-type mixers, 16 719-720 in bar soap manufacture, 22 751 Riboflavin, 25 796-797 Ribonucleic acid probes, 14 153 Ribonucleic acids (RNAs), 12 449 ... 

Condensed Phases, Testing. In the test described by Erikson (Ref), Lead Azide samples were exposed to the reflected shock region produced in an ordinary shock tube Ref T.A. Erikson, Pure Environmental Shock Testing of Condensed Phases , 3rd-ONRSynpDeton (I960), pp 24-41... 

Epreuve au choc de mouton (Shock Test by a Ram). The test with a light weight (such as 2kg) is known as essai au petit mouton , while test with a heavy weight (such.as 30kg) is known as "essai au gros mouton". These tests are listed under Impact (or Shock) Sensitivity Tests in Ref 20, p XVII. See also Ref 24, p E110-L Ref 9, p 560... 

Thermal Shock Test 113 is briefly described in Vol 4, p D1097-R... 

Some kind of thermal shock loading is inevitable during service of FMs. In addition, most FMs have anisotropic thermal-expansion coefficients due to their unique architectures. In 2004, Koh and co-workers investigated the thermal shock resistance of Si3N4/BN FMs [29], They observed their excellent thermal shock resistance by measuring the retention of the flexural strength after thermal shock test, as shown in Fig. 1.17. The monolithic Si3N4 exhibited... 

Flexural response of (a) monolithic Si3N4 and (b) Si3N4/BN FM after thermal shock test. Monolithic Si3N4 showed brittle fracture, while fibrous monolith showed graceful fracture due to its unique architecture (adapted from ref. [29]). 

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

Alternative approaches, termed indentation thermal shock tests , with pre-cracks of known sizes have been used by several authors to assess thermal shock damage in monolithic ceramics. Knoop (Hasselmann et al., 1978 Faber etal, 1981) or Vickers (Gong etal., 1992 Osterstock, 1993 Andersson and Rowcliffe, 1996 Tancret and Osterstock, 1997 Collin and Rowcliffe, 1999, 2000 Lee et al., 2002) indentations were made on rectangular bars, which were then heated to pre-determined temperatures and quenched into water. Crack extensions from the indentations were measured as a function of quench temperature differential, and the critical temperature for spontaneous crack growth (failure) was determined for the material. Fracture mechanics analyses, which took into account measured resistance-curve (7 -curve) functions, were then used to account for the data trends. 

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. 

Morrel, R. (1993), Thermal shock testing and the problem of standardisation , in Schneider, G.A. and Petzow, G. (editors), Thermal Shock and Thermal Fatigue Behavior of Advanced Ceramics, Dordrecht Kluwer Academic, 27-33. 

The catalyst itself was based on a nickel spinel (NiAl204) for stabilization. The active nickel was introduced as surplus of the stoichiometric content of the spinel to the catalyst slurry. The content of active nickel in the final catalyst could be adjusted via the pH during the precipitation. By XRD, a-alumina was identified as an additional phase in case the nickel was incompletely incorporated into the spinel. The sol-gel technique was then used to coat the plates with the catalyst slurry. Good catalyst adhesion was proved by mechanical stress and thermal shock tests. 

Thermal shock testing of an alumina/20 vol.% SiC whisker composite showed no decrease in flexural strength with temperature transients up to 900°C.33 Monolithic alumina, on the other hand, shows significant decreases in flexural strength with temperature changes of >400°C. The improvement is a result of interaction between the SiC whiskers and thermal-shock induced cracks in the matrix, which prevents coalescence of the cracks into critical flaws. 

Figure 22 plots the failure temperature, measured in a cyclic thermal shock test [29], for ceramic catalyst supports as a function of their axial TSP values, which were controlled by modifying either the substrate, the washcoat, or the substrate/washcoat interaction. There is an excellent correlation between the failure temperature and the TSP value. Most automakers call for a failure temperature in excess of 750 C, although this may depend on the size of the catalyst and inlet pipe. Thus, a TSP value of more than 0.4 is required for the coated substrate. Finally, Fig. 22 shows that the washcoat may reduce the failure temperature of the catalyst support by 100-200 C, a trade-off the automakers are well aware of. 

Figure 22 Correlation between axial TSP and failure temperature in a cyclic thermal shock test. (From Ref. 29, courtesy of SAE.)...

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