Use of x-ray for detection of internal log features

• To have knowledge about internal features in saw logs have always been a very important wish among people working in the sawmill industry. The reason for that wish is that with this knowledge it is possible to disintegrate logs in an optimal way.X-ray linear attenuation depends mainly on density and size of the object that is hit by the X-ray beam. This makes X-ray technology suitable for detection of different features in saw logs as there is a density difference between clear wood and many important internal features such as different kind of knots.Medical computer tomography (CT) utilise X-ray to detect internal features in human bodies but is also a very good tool for detection of features in saw logs. However, medical CT-scanners are only used for research purposes in the wood sector as they are far to slow for use in the industry.In order to be able to detect internal log features in industrial speed Log-Scanners with one to four fixed X-ray sources have been developed. With these scanners, that now are used at many sawmills, it is possible to detect and measure features such as: diameter under bark, log type, species, knot parameters, annual ring width, density, heartwood, strength etc. These scanners with fixed sources have a much lower information density than medical CT-scanners but are much faster. The time for scanning a log has been reduced from about two hours to 1.5 seconds. The big draw-back with the scanners with fixed sources is that they give very little information about how defects are located in the rotational direction. However, in order to overcome this drawback, an industrial CT-scanner is now under development. This scanner will operate in industrial speed and will at the same time have an information density that is comparable with a medical CT-scanner.The aim of this presentation is to summarize the current knowledge on X-ray scanning of wood and to propose some suitable applications and strategies for using a fast CT scanner in the wood industry.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Annan maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Other Mechanical Engineering (hsv//eng)

Nyckelord

Träteknik

Wood Technology

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