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Device and Method for Quick and Accurate Determination of Local Elastic Properties in Solids

IP.com Disclosure Number: IPCOM000047924D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Coufal, H: AUTHOR [+4]

Abstract

An apparatus and a method are described for quick and accurate determination of local elastic properties in solids by focussing a pulsed laser on the solid and measuring the acoustic emissions from the solid over a period of time. Ceramics and other types of porous materials are used in numerous branches of manufacturing. Some of these applications involve high precision multi-step manufacturing processes which require close control over certain properties, such as elasticity and density of the starting ceramic material.

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Device and Method for Quick and Accurate Determination of Local Elastic Properties in Solids

An apparatus and a method are described for quick and accurate determination of local elastic properties in solids by focussing a pulsed laser on the solid and measuring the acoustic emissions from the solid over a period of time. Ceramics and other types of porous materials are used in numerous branches of manufacturing. Some of these applications involve high precision multi-step manufacturing processes which require close control over certain properties, such as elasticity and density of the starting ceramic material. A method to insure that the starting ceramic material meets the specification for elasticity and density prior to the start of the manufacturing process comprises the use of a pulse 1 of rectangular cross-section from a suitable laser, such as a nitrogen laser, focussed by spherical lens 2 onto the back side of the ceramic wafer 3. The laser pulse of 10 nanoseconds duration, for example, is totally absorbed on the surface of ceramic substrate 3, thereby generating sharp acoustic pulses (designated by arrows 4) that can be detected by a suitably-positioned acoustic detector 5 of the fast rise-time and no ringing type. One suitable detector is a small piece of polyvinylidene fluoride touching the edge of substrate 3, and its output is coupled to suitable electronic detection circuits 6. The observed acoustic emission signal includes many sharp acoustic spik...