Reliability indicators

This paper examines the cause of 'knees' or 'freaks' in the life-failure patterns resulting from some fatigue processes. A theory is developed which takes into account the extra fatigue damage associated with the non-elastic behaviour of the material. It appears to account for the knee and agrees well qualitatively with test results, though quantitative comparisons are not possible because the stochastic data required for the calculation are not available. It is shown that 'S'-shaped curves sometimes experienced at higher loading roughness are also due to the same mechanism. The theory suggests that the undesirable features of the failure patterns, whose origin has not hitherto been fully investigated, can be eliminated by a design which is intrinsically reliable with respect to the elastic limit (or with respect to the yield strength if a small loss of reliability is acceptable). Because the knees or freaks appear to be a consequence of the fatigue process and arise with conventionally distributed mechanical properties it is suggested that this design action would be more effective than eliminating the items by quality control.

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Synthesis and characterization of silicon nitride powders produced in a d.c. thermal plasma reactor

Allaire

Dallaire

1991

J Mater Sci

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Ultra-fine silicon nitride powder was synthesized from the SiCI4-NHa-H2-Ar system using a d.c. plasma torch reactor (production rate 150-400 g h-l). The powder produced is pure white, fluffy and amorphous. The particles are spheroidal in shape with a mean diameter between 30-60 nm forming aggregates of 0.1-0.4 I.tm depending on the operationalconditions. Chemical analysis on the crude powder handled at ambient atmosphere revealed: N(-NH4CI) :37-39%, 0:3-5% and C1:2-3%. The amorphous powder can be crystallized around 1500 ~ under nitrogen to give an m-phase content in excess of 90%. Infrared spectra can be used to semi-quantitatively determine the NH4CI content of the crude powder. That proportion is between 2.5 and 4%. The influence of some process parameters e.g. (N/Si and H2/N molar ratios, internal pressure) on powder properties was also investigated. The N/Si molar ratio was found to be the most important parameter for the powder composition whereas the internal pressure plays a major role on the powder morphology.

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Reliability indicators

Cited by 10 publications

References 12 publications

Zuverlässigkeitsphysik – ein wichtiger Forschungsbereich zur Minimierung von Ausfällen in technischen Systemen

Zuverlässigkeitsphysik – ein wichtiger Forschungsbereich zur Minimierung von Ausfällen in technischen Systemen

Reliability and failure patterns arising from fatigue

Synthesis and characterization of silicon nitride powders produced in a d.c. thermal plasma reactor

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