Timber Defects Research Articles

AUTOMATED VISION INSPECTION OF TIMBER SURFACE DEFECT: A REVIEW

Automated inspection has proven to be of great importance in increasing the quality of timber products, optimising raw material resources, increasing productivity as well as reducing error related to human labour. This paper reviews automated inspection of timber surface defects with a special focus on vision inspection. Previous works on sensors utilised are presented and can be used as a reference for future researchers. General approaches to solving the problem of wood surface defect detection can be categorised into segmentation and non-segmenting approaches. The weaknesses and strengths of each approach are discussed along with feature extraction techniques and classifiers implemented in timber surface defect detection. Furthermore, insights into the practicality of implementing automated vision inspection of timber defects were also discussed. This paper shall benefit researchers and practitioners in understanding different approaches, sensors, feature extraction techniques as well as classifiers that have been implemented in automated inspection of timber surface defects, thus providing some direction for future research.

Experimental Assessment of the Glued Laminated Timber Beams in 4-Point Bending Tests and Photoelastic Coating Technique

The paper presents the results of investigation on seven glued laminated timber (GL24h class) bending beams. Bending strength and modulus of elasticity were determined. The beams were tested for four-point bending by loading them at a constant speed deflection. The strain gauge method and photoelastic coating technique were applied for strain distributions determination in selected cross-sections of the beams. Good agreement of the measurement results was obtained with both techniques. Application of the photoelastic coating technique enabled more detailed analysis of the beams failure mode, including timber defects influence on the strain distributions.

The segmentation of timber defects based on color and the mathematical morphology

Wood has the texture of natural beauty and elegant color so that it can be widely used in the construction and furniture. So people put the special focus on the texture of wood and they are nearly particular about its color. According to the conventional segmentation method, the characteristics of the wood and the actual production process in a short time of the request, this paper presents a segmentation method of wood panel based on color difference and mathematical morphology. In the HSI space, it firstly focus on select morphological edge detection of H component and I component. Instead of considering the small pixel blocks, it uses median filter to clear it to retain accurate edge image. So edge detection is characterized by the H-component of the color model, then region growing is based on edge information, in order to overcome defects of pseudo edge. In this paper, it uses the boundary information to select seed points automatically, then it takes a regional model of the regional boundary for the region growing, and finally it splits out a defective portion of the timber well.

An estimate of timber degrade in Sitka spruce due to bark stripping by deer in a Scottish plantation

Summary Trees monitored for bark stripping over the previous 20 years were examined for timber defects by felling, then observing stain and rot in the split butt logs and strength testing wood samples. Logs (52 bark stripped, 28 controls) came from eight sites that had tree crops 28 – 39 years old; the logs were stratifi ed for wound size ( 180 cm 2 ), large wounds being rare. Many wounded logs had no stain or rot, but six of the 33 better-quality sawlogs were judged to be usable only for pulp. Modulus of elasticity and modulus of rupture were affected only at wounds and only in the sapwood there; at this position, mean stiffness and strength were both signifi cantly reduced compared with control logs, with lowest means for logs with large wounds. Large wounds suffered a much greater incidence of stain and rot than small wounds, but their rarity meant that the calculated fi nancial loss caused by the bark stripping estimated to be incurred over the whole rotation up to felling was only 3 per cent of the crop value.

Costs of protable sawmilling timbers from the acacia woodlands of western Queensland, Australia

Portable sawmilling trials with Acacia aneura (mulga) and A. cambagei (gidgee) have been undertaken to estimate the private landholder costs associated with small-scale timber production from woodlands in western Queensland, Australia. A time study of harvesting and milling operations facilitated estimation of landholder labour input requirements. The scarcity and small size of millable logs, coupled with the prevalence of timber defects, make harvesting and portable sawmilling of western Queensland acacias an expensive undertaking for landholders. The cost of producing sawn timber that meets the High Feature (HF) grade of Australian Standard AS2796 is estimated at between A$3,000/m3 and A$3,400/m3 of HF timber.

Incidence of bullseye borer (Phoracantha acanthocera, (Macleay) Cerambycidae)in 20–35 year old regrowth karri in the south west of Western Australia

Summary A destructive sampling technique and an incidence survey were used to investigate the presence of bullseye borer (Phoracantha acanthocera (Macleay)) in regenerated karri (Eucalyptus diversicolor F. Muell) forest. In the destructive sampling survey, bullseye borer in marri (Corymbia calophylla (Lindl.) K.D. Hill and L.A.S. Johnson) was also examined. The incidence survey was done across a rainfall gradient and investigated the influence of site characters on borer attack levels. Over both surveys, a total of 945 trees and 5285 billets were inspected. Association with timber defects such as incipient rot (brown wood) and internal kino was also studied. In the destructive survey, the poor quality karri site had more borer attack than the high quality karri site, with 17.3 mean insect gallery intercepts per tree, and 43.1% of billets and 100% of trees attacked. Marri hada lower borer incidence than karri, with 2.4 mean insect gallery intercepts per tree, 14.6% of billets and 82% of trees attacked. Despite higher infestation rates in the poorer quality site, borers, incipient rot and internal kino were more prevalent in larger trees. Incipient rot and internal kino were correlated with borer attack. In the incidence survey, borer infestation ranged from 24% to 78% of trees with significant differences between sites (p <0.001). Infestation rates could be grouped into four categories. Low, moderate, high and very high, which corresponded to < 2. 2–4,4–6 and >6 external borer symptoms per tree respectively. However correlations of tree and site parameters were weak. Dry sites in close proximity to jarrah/marri forest and in small coupes were more prone to borer attack. These findings confirm the results from earlier studies.

Notice to Contributors

Bark stripping by red deer has been monitored at 40 sites in Glenbranter Forest, Argyll, since 1978, and the state of the 1173 wounds incurred has been recorded yearly. Despite deaths of trunks and felling, 70 per cent of the wounds are still extant. Xylem was exposed and resin produced in the great majority of wounds. After 2 years new bark was developing on most wounds and after 8 years many wounds were completely healed. Large wounds greater than 180 cm in area had xylem exposed longer and healed more slowly than smaller wounds. Trees 20 or more years old at wounding had slower healing than younger trees, and about 10 per cent of the damaged trunks died. Many fraying and thrashing wounds occurred on trunks or trees that later died, but wounds of this origin which began to heal quickly became completely healed. Rots developed in only 1 per cent of the wounds, most of them greater than 180 cm in area. Although damage from bark stripping seems less serious than feared, timber defects may exist below apparently healed wounds.

Do Women Like Beetles?

One in three claims against surveyors arising out of surveys involves allegations relating to damp, rot or some other timber defect. There is a tendency for surveyors to be reluctant to make statements in reports regarding the active nature of such conditions, as this could prejudice the chances of a property transaction proceeding. Considers recent cases where surveyors′ liability for commenting on such defects has been the matter at issue. In particular, considers a very recent judgment, given in the Official Referees Courts in London. An Essex‐based surveyor was found to have been negligent in failing to warn clients in a survey report as to the severe structural damage that the death‐watch beetle was capable of causing to a timber‐framed farmhouse. The surveyor referred to this as woodworm infestation. Damages in excess of £100,000 inclusive of interest were awarded together with costs. Concludes by making clear the importance of distinguishing between common furniture beetle and death‐watch beetle.

Forest Cover and Snow: Implications for Deer Habitat in Southeast Alaska

Relationships between snow depth and overstory characteristics were studied on 19 0.4-ha oldgrowth plots and 1 60-year-old 0.4-ha 2nd-growth plot near Juneau during winter, 1983-84. Mean tree diameter at breast height (dbh), number of stems/ha, percent Sitka spruce (Picea sitchensis), mean tree height, percent timber defect, basal area, and net timber volume were measured using variable plot and point-centered quarter techniques. Canopy cover was measured from photographs of the overstory taken at each snow measurement point. Snow depth in a high-volume plot (>100,000 board feet/ha) averaged 29% of that in an adjacent forest opening. Snow depth was correlated with net timber volume (r, = -0.90), tree height (r, = -0.85), basal area (r, = -0.79), percent canopy cover (r, = -0.76), percent spruce (r, = -0.66), and mean tree diameter (r, = -0.65). Old-growth plots with high net timber volume had the lowest snow depths. The low snow depths observed in high-volume, old-growth stands are attributed to the large-diameter limbs and deep crowns of older, dominant trees. J. WILDL. MANAGE. 51(1):28-33 Snow is an important component of the winter and early spring environment of Sitka blacktailed deer (Odocoileus hemionus sitkensis) in southeast Alaska. Snowfall reduces the availability of forage, increases the energetic costs of locomotion, and influences deer habitat selection and survival (Edwards 1956, Klein and Olson 1960, Parker et al. 1984). Correlations between overstory characteristics and snow depth beneath the canopy can aid wildlife managers in identification of valuable oldgrowth winter range for deer and may suggest silvicultural treatments to enhance the snowinterception qualities of even-aged, 2nd-growth stands. Our objectives were to develop relationships between snow depth and forest stand characteristics across a broad range of oldgrowth types in southeast Alaska and to compare snow depth in the open to snow depth in the forest, and in old-growth vs. 2nd-growth stands. This study was conducted in the winter of 1983-84 by the Alaska Dep. Fish and Game, as part of Fed. Aid Wildl. Restor. Proj. W-22. We thank R. W. Flynn, J. W. Matthews, and M. H. Thomas for field assistance during this project. P. B. Alaback, A. S. Harestad, D. E. McKnight, R. S. McNay, and S. R. Peterson provided helpful review comments on the manuscript.

Tree Breeding in Support of Vegetative Propagation ofEucalyptus grandis(Hill) Maiden

SYNOPSIS Eucalyptus grandis is the most important species supplying timber to the market in South Africa. However, serious timber defects, especially high growth stresses resulting in log end-splitting, reduce the percentage recovery in converting logs to solid wood products. Breeding trials have indicated that substantial genetic improvement is possible in growth rate, stem straightness, splitting of logs, penetration of preservatives and even in rootability of cuttings. Moreover, recent success in clonal forestry brought renewed enthusiasm for obtaining large gains through vegetative propagation. However, while gains from vegetative propagation may far exceed gains from sexual breeding the former is “one-off” in nature. Unless new genotypes with superior characteristics are created the gains obtained from clonal forestry will become stagnant. This paper emphasises the need for the maintenance of genetic diversity and continued breeding. It shows that genetic information from family trials will aid in ef...

Moth pocket, a timber defect inEucalyptus regnans

It is proposed that “bird's eye”, a common timber defect of Eucalyptus regnans, be renamed “moth pocket” because of its origin and appearance. The defect is formed by an unidentified Lepidoptera la...

Selection of Forest Tree Species in Rhodesia

SUMMARY Productivity of forest plantations in Southern Africa could be increased considerably by careful matching of species to locality and site. This becomes increasingly apparent as the consequences of off-site plantings are exhibited in commercial stands. Susceptibility to disease and insect attack, wind damage, losses through drought and frost, and defective stem form and timber are among the more serious effects. In addition there are instances of severe timber defects developing in some species under site conditions which otherwise support good volume growth and physiological health. In Rhodesia, observations made over a number of years have indicated the basic site and climatic requirements for the main commercial tree species and these are given in summarized form. It is suggested that, to improve productivity of plantations in Southern Africa, greater scope exists in extending the adaptability of accepted species by breeding and manipulation through management than in seeking new species. Countr...

Einige Pilzschäden an alten Eichen

Every year a great many valuable veneer oaks are damaged by fungal diseases as a result of their great age. The most important oakwood destroying fungi were isolated and identified and their decay activity was tested in the laboratory. White rots in oak are mostly caused byStereum frustulosum, Stereum gausapatum, Hymenochaete rubiginosa, Polyporus dryophilus orFomes robustus. The brown rot fungusPolyporus sulphureus is responsible for the so-called red rot.Fistulina hepatica produces in the heartwood of oaks an intensive redbrown discolouration, but does not injure the density and strength properties of the wood considerably; this timber defect is designated asbrown oak. In contrast toFistulina hepatica some of the other abovementioned species (for examplePolyporus dryophilus, Fomes robustus andPolyporus sulphureus) decay the infected wood rather quickly. The microscopical feature of the attacked wood nearly always shows an accumulative appearance of dark inclusions in the parenchymatous tissue as well as in the fibres and tracheids. The enzyme activity of the different species varies somewhat, in the early stage of attack an influence can sometimes be observed only immediately around the hyphae and in other cases it quickly spreads over the whole cellwall diameter. The decomposition of the lignin component in the cellwalls begins soon after infection as can be shown by staining slides with astrablue. However the early stage of fungal attack, which can generally be observed in red rotten or red striped softwood after fluorochromation with acridin-orange, is scarcely or not at all developed in oakwood.

Schnittholzqualität und Furniereignung von Douglasien aus linksrheinischen Anbaugebieten

Douglas fir sample trees from 9 various stands were cut in sawmills. Every board of the converted timber was graded; all defects in timber were analysed, especially all black and sound knots on the surface of the boards were measured. The percentage of good boards prooved to be comparatively low. From fertile sites the sawn timber quality seems to be inferior compared with wood from poorer and dryer sites. Douglas firs grown single between broadleaved stands showed the lowest timber quality. Throughout the quantity and thickness of black knots were responsible for poor quality. Experiments with production of veneer yielded useful carved veneers when sliced of quartered and clear logs. Branchless logs from 80 years old Douglas firs could be worked up to carved veneers, but are too young for peeled veneers. For full veneer logs diameters of 70 cm and structure of small annual rings is essential.

Radiation monitoring of macrodefects in timber used in the mining industry

1. The scintillation radiation method is very effective in detecting hidden defects in timber supports for mine workings. 2. The best gamma quantum energies for irradiating pit props are those from 100–400 keV sources. 3. By means of radiation “defectoscopes,” which are described above, we can carry out industrial control. The speed of this operation is higher if we use low-inertia recording devices, such as oscillographs.

Defects in timber caused by insects may be largely prevented : U. S. Department of Agriculture, Press Service

We study the model-independent traversable wormholes from cosmological reconstruction based on Gaussian processes (GP). Using a combination of Union 2.1 SNe Ia data, the latest observational Hubble parameter data and recent Planck’s shift parameter, we find that our GP method can give a tighter constraint on the normalized comoving distance, its derivatives and the dark energy equation of state than the previous work (Seikel et al., 2012). Subsequently, two specific traversable wormhole solutions are obtained, i.e., the cases of a constant redshift function and a linear shape function. We find that, with decreasing cosmic acceleration, the traversal velocity v of the former case increases and the amounts of exotic matter IV of the latter case decreases.

Some Common Defects in Timber and their Causes

Some Common Defects in Timber and their Causes