Failure/degradation

Describe the difference between catastrophic failure, degraded failures, incipient failure. 

Let us consider a system made up of C components. The -th component is affected by M, degradation processes, which may be influenced by the failure/degradation behavior of the other C-1 components of the system. The generic y-th degradation process impacts on a number Nj of failure modes whose stochastic occurrence in time is described by Nj different failure rates Xj., k = 1,2,..., NJ. 

For each tram, the following five states (one working state and four different failure/degraded states) were considered ... 

Since there are many kinds of SOFC stacks which are fabricated by different fabrication methods in different sequences, it looks rather hard to describe the failure/degradation modes of stacks in a proper manner. Even so, it seems possible to extract some common features out of various failure/degradation modes. 

In order to determine the failure degradation of pyrotechnics in the storage process, the sensitive parameters is chosen as degradation parameters. A certain pyrotechnics has two sensitive parameters at most, usually one. When the sensitive parameters can t meet the design requirement, the degradation failure occurs. Thus the sensitive parameters must have following properties ... 

Vehicle failure, degradation, towing, and repair rates are constant. 

The use is described of differential scanning spectroscopy (DSC) as an analytical tool in the diagnosis of part failure. Degradation of the polymer during processing is examined, and the example is investigated of a 30% glass reinforced PPO which showed brittleness and for which the causes of failure were revealed by means of DSC analysis. 

In applying the definition of rehabihty, the concept of adequate performance must be estabhshed clearly. Products usually do not fail suddenly, but degrade over time. Gasket leaks on equipment, for example, may start as a slow weep and increase in volume over time. The point at which this undesirable occurrence is called a failure must be clear before rehabihty can be measured objectively. Changing the failure definition for a product changes its rehabihty level, although the product itself has not changed. 

Because pure aluminum is n picaUy too soft to be drawn into a fine wine, it is often alloyed with 1° o sihcon or 1° o magnesium to provide a sofid solution-strengthening mechanism. The resistance of Al-1° o Mg wine to fatigue failure and to degradation of ultimate strength after exposure to elevated temperatures is superior to that of Al—1° o Si wine. 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the soHd state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the soHd state it is possible to observe the free radicals formed as a result of polymer chains breaking under the appHed stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embrittlement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

The presence of errors within the underlying database fudher degrades the accuracy and precision of the parameter e.stimate. If the database contains bias, this will translate into bias in the parameter estimates. In the flash example referenced above, including reasonable database uncertainty in the phase equilibria increases me 95 percent confidence interval to 14. As the database uncertainty increases, the uncertainty in the resultant parameter estimate increases as shown by the trend line represented in Fig. 30-24. Failure to account for the database uncertainty results in poor extrapolations to other operating conditions. 

Fig.l. The more important metabolites of tryptorhan Degradation of the tryptophan accompanied with increasing in 10 times of kynurenine level in the case of renal failure. As the result of 3-hydroxy-kynurenine s ability of easy oxidize neurotoxin compounds form. 

Strength degradation - ereep failure, fatigue, wear, eorrosion. 

Modern equipment is frequently eomposed of thousands of eomponents, all of whieh interaet within various toleranees. Failures often arise from a eombination of drift eonditions rather than the failure of a speeifie eomponent (Smith, 1993). For example, typieally an assembly toleranee exists only to limit the degradation of the assembly performanee. Being off target may involve later warranty eosts beeause the produet is more likely to break down than one whieh has a performanee eloser to the target value (Vasseur et al., 1992). This again is related to manufaeturing variation problems, and is more diffieult to prediet, and therefore less likely to be foreseen by the designer (Smith, 1993). 

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