Thermal shock resistance calculation

Estimate the thermal shock resistance AT for the ceramics listed in Table 15.7. Use the data for Young s modulus E, modulus of rupture c, and thermal expansion coefficient a given in Table 15.7. How well do your calculated estimates of AT agree with the values given for AT in Table 15.7 ... 

This chapter discusses the behavior, under thermal shock conditions, of epoxy resins toughened with ceramic particulates. Alumina Al203 and silica Si02, which are usually used as filler for insulation materials, and the new ceramic materials silicon carbide SiC and silicon nitride Si3N4 are employed. For these toughened epoxy resins, the thermal shock resistance is evaluated by using fracture mechanics. The difference between experimental and calculated values of the thermal shock resistance is discussed from a fractographic point of view. 

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) ... 

Table 2.9 Properties, thermomechanical strains at preheating and startup, and calculated values of first Hasselman criterion of thermal shock resistance in carbon cathode blocks of different producers [63, 64]... 

In yet another method of determining thermal shock resistance, material properties are established first. Thermal shock resistance is calculated from the values of these properties, which are called R values. The higher the R value, the greater the thermal shock resistance. Hasselman [4] derived a series of parameters to rank materials according to their thermal shock resistance. 

The expected relative thermal shock resistance of materials, as mentioned above, can be calculated from measurement of a range of material properties. Hasselman (11) derived a series of parameters in an attempt to rank materials in order quantitatively. High calculated values of R are indicative of good thermal shock resistance. 

A failure of a thermal-structural component is not only governed by the transient macro-scale thermal stress field induced by a transient temperature field, but also by its micro-scale stress field if the component material consists of several phases (such as a composite component, which often contains a reinforcement and a matrix). The experimental investigation of the nticrostmctural factors, which control the thermal shock resistance of a composite component, is very difficult. Some theoretical calculation of the thermal stress of various components upon heating/ cooling has been well documented, but these works mainly focus on the macro-scale... 

Spinel composites should be more useful than pure MgO in terms of resistance to thermal shock damage and further loss of strength, because the relative strengths of all composite materials after shocking remain much higher than those of MgO (Fig. 14.13). These results show clearly that the resistances to thermal shock damage for all these materials have the trends expected on the basis of the calculated R" and R" parameters.74,103... 

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