HIGH-FREQUENCY ULTRASOUND DETECTION OF SMALL DEFECTS IN Si<sub>3</sub>N<sub>4</sub>CERAMIC

Shi, Y.; Hennickec, J.; Netzelmann, U.

doi:10.1080/10589759708953025

Cited by 3 publications

(1 citation statement)

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“…Ultrasonics can be highly sensitive to the surface/near‐surface region through the use of surface waves. Ultrasonic surface wave was reported to be capable of detecting simulated surface flaws as small as 20 μm; however, it could not resolve the flaw size because it is already much smaller than the ultrasonic wavelength 32–35 . In addition, ultrasonic methods are difficult to be used for components with a complex geometry such as an engine valve.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Silicon‐Nitride Ceramic Valves

Sun

Zhang

Andrews

et al. 2008

Int J Applied Ceramic Tech

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Silicon‐nitride ceramic valves can improve the performance of both light‐ and heavy‐duty automotive engines because of the superior material properties of silicon nitrides over current metal alloys. However, ceramics are brittle materials that may introduce uncertainties in the reliability and durability of ceramic valves. As a result, the lifetime of ceramic valves are difficult to predict theoretically due to wide variations in the type and distribution of microstructural flaws in the material. Nondestructive evaluation (NDE) methods are therefore required to assess the quality and reliability of these valves. Because ceramic materials are optically translucent and the strength‐limiting flaws are normally located near the valve surface, a laser‐scatter method can be used for NDE evaluation of ceramic valves. This paper reviews the progress in the development of this NDE method and its application to inspect silicon‐nitride ceramic valves at various stages of manufacturing and bench and engine tests.

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Section: Introductionmentioning

confidence: 99%