VOLUME 47, ISSUE 6/2006

Stress wave impulse tomography is a relatively new procedure for the non-destructive diagnosis of trees. The objective of the investigation was to depict influencing variables on the quality of the tomographic display. The ARBOTOM ® Impulse-Tomograph was used to conduct diverse tests on eight different species of deciduous trees. Anisotropy of the wood, wood temperature and direction of the sonic induction cause differences in the speed of the impulse. A conical propagation of the stress waves is assumed. In addition to the wood density, the MOE also influences the speed of the impulse. Even relatively small defects are detected, but they are depicted less precisely in the tomograms than larger damage is. This is particularly evident in species with low wood density. A broad colour spectrum of the tomograms provided better results in such cases. Applications using stress wave impulse tomography for large-dimensioned laminated wood are conceivable and represent a future field of the procedure use.

This article presented the main areas of laser utilisation, the theoretical background, the properties of laser light and an analysis of the operation principles and characteristics of the cutting mechanism. The author discusses the challenges of using lasers for cutting wood, and describes the experimental work done on solid wood. Laser cutting compared favourably to traditional and high-pressure pneumatic cutting in terms of surface roughness and kerf width. Carbonisation of the surfaces and the high costs of the method are the most important drawbacks of the method.

The agricultural by-products such as cereals straw, hemp and flax shives as well as Miscanthus were milled with an extruder or the combinations extruder/extruder or extruder/refiner (dry). The pre-treatment of the raw materials and the adjusted machine parameters were varied and the fibres quality was evaluated. Using the best fibres different panels/boards (MDF, HDF, insulating materials and cement fibreboards) were produced and tested. The process with the combination extruder/extruder or extruder/refiner is very suitable for the milling of cereals straw to produce composite materials which fulfil EN-standards for boards. The extruder-fibres made from grain straw and their products are similar to the TMP-ones. For other investigated raw materials it is better to choose the TMP-process because of fibre and product quality.

In DIN EN 622-5 there are tiuo options to test the moisture resistance of bonds in fibreboards, namely the Vl00-test and the V3l3-test. Similar options apply also for particleboards. Results of research iuork conducted on medium density fibreboards reveal that vacuum-pretreatment of the samples prior the Vl00-test increases the transverse tensile strength. On the contrary, vacuum-pretreatment reduces the transverse tensile strength measured according to the V3l3-test. The reasons for such a behaviour are discussed.

A critical element during the assembling of prefabricated structural elements with solid wood panels is the tightness of the Joints. The air tightness is usually proven by a blower door test. Thus a convection of humid and warm air can be excluded. Nevertheless it is possible that the Joint at the room side is not completely closed, for instance due to residual stress. The presented paper investigates the effect of water vapour diffusion through an open Joint in the connecting area of two elements on the moisture behaviour of the building part.

Rack furniture testing as currently practised is time-cansuming due ta high cycle numbers and law test frequencies, as well as material-intensive and thus generally expensive because af the examinatian af camplete praducts. The develapment af a test engineering salutian is described, with which the physical praperties as well as the fatigue behaviaur af canstructian cannectians can be farecasted with the help af dynamic examinatians and selected sensar technalagy. The article is particularly cancerned with glued salid waad Jaints at rack furniture, whereby the initial strength and the temparal pracess af the strength reductian receive special attentian in the cantext af dynamic laad tests. The knawledge gained by the investigatians was united in a check madule, which makes passible a sufficient descriptian af the mechanical stability and the lang-term behaviaur (changes af farm, elasticity and strength) af glued salid waad Jaints and alsa canstructians with substantially reduced time and cast.

Although decorative finish foils have only gained conside- rable importance for the furniture industry and other wood-processing industries during the past twenty years, the manufacturing history of decorative finish foils started already more than 75 years ago. In a brief historical overview, the development stages of this product group are outlined before addressing the subject of the more than 40 years of history of decorative printing at the site Leipzig. The individual manufacturing processes of decorative finish foils are outlined. Resulting from the particular structure of decorative finish foils, the characteristics of this product group, its areas of use in the wood-processing industry and the general quality requirements for these areas of use are described.

Since 1989, the "Tree of the Year" board of trustees has drawn attention to 18 tree species that are of importance for various fields. The overview briefly outlines the reasons for the selection by the Board of Trustees as well as some tree and wood characteristics. Part 2 presents the trees from 1998 to 2006: Wild pear (Pyrus communis L., var. pyraster L.), white willow (Salix alba L.), sand birch (Betula pendula Roth.), ash (Fraxinus excelsior L.), juniper (Juniperus communis L. ), black alder (Alnus glutinosa Gaertn.), silver fir (Abies alba Mill.), horse chestnut (Aesculus hippocastanum L.), black poplar (Populus nigra L.), ginkgo (Ginko biloba L.).