Laser-ultrasonic measurement of a thin sheet

Highlights

Laser-ultrasonics uses lasers to generate ultrasonic waves to detect objects and measure distances. As a non-contact and non-destructive technique, it can be used on parts of a complex shape and at elevated temperatures. Taking papermaking as an example, previous measurement techniques require removing a sheet of paper from the papermaking machine, bringing it to a lab that contains various measurement instruments, measuring the paper’s density, consistency, etc. recording & analysing the results then using results to adjust production. This innovation is a more compact and a simpler measurement system which is both accurate and cost effective, because it uses laser ultrasonics to take the same measurements but at the assembly line and records the results directly online.

Technology transfer

This technology is available for licensing, or for further development through a collaborative research agreement with NRC. The business opportunity may be referred to by its NRC ID # 10946.

Market applications

Proven to be applicable to real industrial applications of any industry that requires instant results, this innovation is particularly useful for papermaking and printing, aluminum foil rolling and plastic sheet fabrication. It relates to the determination of the elastic properties of a thin sheet and to the measurement by laser-ultrasonics of the tension applied to a thin sheet.

How it works

A method and an apparatus for non-contact and non-invasive characterization of a moving thin sheet and in particular of a paper web on a production line. The method uses a laser for the generation of sonic and ultrasonic waves in the thin sheet and a speckle insensitive interferometric device for the detection of these waves. The generation is performed in conditions to avoid damage impeding further use of the sheet. When the generation and detection spots overlap, the method provides a measurement of the compression modulus. When the generation and detection spots are separated by a known distance and plate waves (Lamb waves) are generated and detected, the method provides a measurement of the in-plane modulus and of the tension applied to the sheet. By detecting waves propagating in various directions, either by rotating the detection sensor head or multiplexing the signals provided by several detection or generation locations, the anisotropy of the in-plane modulus is determined.

Benefits

There is great interest in industry to measure the elastic properties of thin sheets, either on the manufacturing line or off-line and to evaluate the tension applied to these thin sheets during processing in order to avoid breakages and insure optimal runnability.

Patents

NRC file 10946: https://www.google.com/patents/US6543288

Patent granted in USA.

Contact

Dann Chow, Business Advisor
Telephone:  204-221-3157
EmailDann.Chow@nrc-cnrc.gc.ca

Express Licensing

NRC makes research & development licenses for this technology available under its Express Licensing program. To purchase such a license, please complete the Express Licensing order form.

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