To fully optimize the value of material produced from a log requires information about the log's internal defects prior to log breakdown. Studies have shown that a 7 to 21 percent improvement in log value recovery can be achieved if the location and identity of internal defects are known. Recent developments in advanced nondestructive testing methods such as CT and MRI offer, for the first time, the possibility of finding internal defects in logs prior to breakdown. Our ability to detect and recognize defects using this data depends Critically on our understanding of wood structure and our ability to devise reliable method for automated image interpretation. While a lot of work has gone into demonstrating that certain types of defects manifest themselves in such sensor imagery, there has not been a systematic approach toward making the automatic inspection of logs a practical reality. This dissertation describes work aimed at creating a viable automated technology for locating and identifying log defects. The imaging modality used in this dissertation is CT. An important first step is to establish a data base of imagery and the ground truth information to determine how the various defects manifest themselves in this imagery. The second step is to study defect characterization and determine exactly which defects are detectable. The final step is to develop a basic method of approach to automated image analysis. A data base has been created from two hardwood species. It is representative of hardwood logs in the sense that it contains almost all the major defects. Visual inspection and analysis of these CT images have shown that most defects manifest themselves in CT imagery. These defects can be detected by features such as intensity, 3-d shape, and texture. As a means of automated image analysis, a knowledge-based vision system has been developed. It consists of three components: a data acquisition unit, an image segmentation module, and scene analysis module. A 3-d adaptive LS filter has been developed in the segmentation module that is efficient in removing annual rings while preserving other needed high frequency detail. Images are segmented using a multiple threshold scheme and regions are grouped using a 3-d connected volume growing algorithm. To represent the 3-d nature of wood defects, a set of basic features have been defined and used to design a set of hypothesis tests. These features seem to be adequate for defect recognition. To cope with imprecision and ambiguity the Dempster-Shaffer model for knowledge representation is used in the vision system. As a viable alternative to Bayesian-based theory, the Dempster's method of evidential reasoning is employed that uses previously unavailable information such as the amount of ignorance and ambiguity a hypothesis exhibits. As such, the proposed vision system seems to be able to recognize a number of hardwood defects. This dissertation also explores wood texture as an additional feature in defect recognition, and contributes the first application of robust Spatial AutoRegressive modeling to wood texture analysis. Based on a correlation measure, two simple but efficient texture discrimination schemes are proposed. Incorporating a texture test in the scene analysis should improve the vision system's recognition power. As a pilot research, this dissertation has explored a number of important issues in creating a vision system for automated log inspection. Clearly, more work is needed to make the system more robust with additional species. Nevertheless, preliminary results seem to indicate that a machine vision system for automated hardwood log inspection can be developed. / Ph. D.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study aimed to classify wood from trees that were exposed to forest fires with regards to their end use. Exposure to high temperatures over time is known to degrade wood in various ways. This degradation could limit the end use by altering mechanical, chemical and physical properties, leading to difficulty in processing or failing to meet required specifications for various grades. In this study wood from Pinus radiata trees that were exposed to forest fires of different levels of heat intensity was analysed with regards to its anatomical and physical changes. Trees were visually classified into three classes of burn severity. Moisture content measurements were taken from 135 standing trees, divided among the three classes. 30 trees, 10 from each of the three classes, were sampled and used for CT analysis. Samples were taken to include growth from before and after the fire. Two samples were taken from each tree, one from the charred and one from the uncharred side. The CT data was analysed and used to measure properties like growth ring width, cell wall thickness, lumen diameter and cell wall density. The data was used to compare properties from the charred and uncharred sides within a given year, as well as compare properties between years. The study showed that there were significant differences in the MC between the burnt and unburnt sides of trees from classes 2 and 3. The difference between the MC measurements on the burnt sides of three classes differed significantly from each other. Lightness measurements were taken on samples from classes 2 and 3. These samples showed no significant difference between the burnt and unburnt sides for either of the two classes. The samples from the less exposed class were lighter, but not significantly so. The macroscopic wood density was determined using core samples. A decrease in wood density was observed with an increase in fire exposure. The mean densities for all three classes however still fulfilled the requirements for structural timber set by the SABS. Growth ring width, cell wall thickness and lumen diameter analysis gave varied results, with some cases showing a decline in properties while others were seemingly unaffected. For many of the outcomes of this study, results found by previous studies could not be reproduced. / AFRIKAANSE OPSOMMING: Hierdie studie het gepoog om bome wat aan plantasiebrande blootgestel is volgens hul eindgebruik te klassifiseer. Dit is bekend dat blootstelling aan hoë tempreature hout in vele maniere afbreuk. Hierdie afbreuking kan die eindgebruik van die hout beperk deur die meganiese, fisiese en chemiese eienskappe sodanig te verander dat dit kan lei tot probleme met verwerking of ongeskiktheid vir sterktegrade. In hierdie studie is Pinus radiata bome wat aan plantasiebrande van verskillende grade blootgestel is ondersoek in terme van hul fisiese en anatomiese veranderinge. Bome is visueel in drie klasse van verskillende brandskade gegroepeer. Voglesings is op 135 staande bome, verdeel tussen die drie klasse, geneem. Monsters is van 30 bome, 10 uit elke klas, geneem vir CT analiese. Monsters is so geneem dat dit groei van voor en na die brand ingesluit het. Daar is twee monsters van elke boom geneem, een van die gebrande en een van die ongebrande kant. Die CT data is geanalieseer en gebruik om eienskappe soos jaarringwydte, selwanddikte, lumendiameter en selwand digtheid te meet. Die data is gebruik om eienskappe tussen die gebrande en ongebrande kante, sowel as tussen jare te vergelyk. Die studie het gewys dat daar noemenswaardige verskille is tussen die voginhoud van die gebrande en ongebrande kante van bome uit klasse 2 en 3. Die voginhoud van die gebrande kante van al drie klasse verkil ook noemenswaardig van mekaar. Ligtheidmetings is gedoen op monsters van klasse 2 en 3. Die monsters het nie ‘n noemenswaardige verskil tussen die gebrande en ongebrande kante getoon nie. Alhoewel die klas 2 monsters ligter vertoon het as die klas 3 monsters, was die verskil nie betekenisvol nie. Houtdigtheid is bepaal deur fisiese metings op die monsters wat vir die CT skandering gebruik is te doen. ‘n Daling in digtheid met ‘n toename in blootstelling aan die brand het duidelik na vore gekom. Die digtheid is egter nog hoog genoeg om aan die vereistes vir strukturele hout te voldoen, soos die die SABS bepaal. Jaarringwydte, selwanddikte en lumen diameter het wisselende resultate opgelewer, met sommige gevalle wat ‘n afname in eienskappe wys en ander wat ooglopend onveranderd was. Vir vele van hierdie uitkoms kon die resultate van vorige studies nie bevestig word nie.

Recycling felled urban trees that are hazardous or unhealthy is increasingly viewed as a viable practice to control disposal costs, promote environmental practices, and support local commerce. Wide spread waste wood utilization is encumbered by numerous presumptions about wood quantity, quality, accessibility, and presence of foreign objects; yet there is almost no scientific literature about these presumptions. Without this knowledge, informed decisions cannot be made about the viability of waste wood utilization. In this study, we assessed the quality and quantity of timber in street trees scheduled for routine removal by the District of Columbia (the District) using a modified timber grading protocol adapted from the United States Forest Service. We developed a second protocol to assess the feasibility of timber salvage by identifying physical barriers commonly encountered in urban areas (e.g., high volume traffic, utilities around the tree, and infrastructure). The randomized sampling scheme was stratified by land-use zones and focused on the six most abundant tree species: Acer platanoides, Acer rubrum, Acer saccharum, Quercus palustris, Quercus phellos, Quercus rubra. Our findings suggest the majority of condemned street trees are of too poor quality to contain timber (58% cull rate); however, trees that contain merchantable logs are likely to be easily removed. A notable discovery that could prove problematic for wood salvage was that the majority of trees (88%) contained superficial metal items embedded in the trunk surface. Furthermore, presence or absence of a merchantable-sized log (p=0.0445) depended on the tree's species, as did the average volume observed (p<0.0001). Additionally, land-use zones had an effect on the removal feasibility scores (p=0.0257) but had no effect on log presence or log volume. Throughout the District, we estimated that 36,500 board feet of merchantable logs are generated from routine removals of our top six species annually. These findings provide empirical data pertaining to urban timber salvage, which might aid decisions on the investment worthiness of utilizing urban street trees. / Master of Science

A classificação estrutural de peças de madeira possibilita melhor utilização do material, separando as peças de acordo com a sua resistência estimada. Nesse processo é feita a classificação visual, de grande importância no caso de madeiras do gênero pinus, e a classificação mecânica por meio de testes não destrutivos com objetivo de estimar o módulo de elasticidade. Com esse objetivo, além de ensaios de flexão estática, podem ser aplicados métodos dinâmicos baseados em medições das frequências naturais e densidade do material para a determinação do módulo de elasticidade da madeira. Nesse sentido o objetivo deste trabalho foi avaliar a eficiência do aparelho portátil Brookhuis Micro Timber Grader (MTG) na estimativa do módulo de elasticidade por meio de ensaios não-destrutivos de vibração longitudinal. Para tanto, foi utilizado um lote de peças estruturais de madeira da espécie Pinus elliottii classificado visualmente. Os resultados obtidos por esse aparelho foram comparados com os resultados de módulo de elasticidade obtidos em ensaio de flexão estática. Tendo em vista a sua praticidade, é recomendável a utilização deste método para a classificação estrutural de peças serradas de madeira. A classificação visual agregada a classificação mecânica são essenciais para a utilização do Pinus em vigas laminadas coladas, construções industrializadas de madeira e do sistema construtivo em woodframe. / The structural grading of wood allows better use of the material, sorting the specimen according to their estimated strength. In this process the visual grading is a fundamental matter in use of the structural Pinus elliottii and also the mechanical grading obtained by non-destructive methods in order to estimate the modulus of elasticity. For this purpose, in addition to the static bending tests, dynamic methods based on measurement of the natural frequencies and density of the material to determining the modulus of elasticity (MOE) of timber can be applied. The objective of this study was to evaluate the efficiency of portable device Brookhuis Micro Timber Grader (MTG) in estimating the modulus of elasticity by non-destructive testing of longitudinal vibration. It was used structural pieces of wood species Pinus elliottii rated visually. The results obtained by this device was compared with the modulus of elasticity results obtained in static bending tests. Given its convenience and low cost, it is recommended to use this method for structural grading of timber sawn pieces. The visual and stress grading are essencial for the use of Pines in glued laminated timber, industrilization timber constructions and woodframe constructions.

Dans le cas du bois massif, les résistances en flexion et en traction peuvent être altérées par la présence de défauts. Les nœuds et la distorsion du fil qui en découle, sont les causes de la diminution du rendement mécanique des sections de poutres de structure. A ce jour, l’effet de ces défauts sur la perte de résistance de l’élément de structure ne peut être quantifié avec exactitude. Le classement mécanique du bois de structure n’est alors pas optimal et ne permet pas de valoriser les éléments de fortes résistances. La présente étude a pour objectif d’étudier l’influence de la nodosité sur le rendement mécanique de poutres en Pin Maritime dans le but d’en améliorer son classement mécanique. Cette étude s’appuie sur une base de données recensant les propriétés mécaniques et physiques de poutres de grandes dimensions ainsi que les propriétés géométriques des nœuds présents sur ces éléments. Différents outils statistiques sont utilisés afin de définir les variables explicatives et leurs pouvoirs prédictifs sur la résistance mécanique de ces composants structurels. De ces analyses, il ressort que certaines caractéristiques propres aux nœuds sont significatives et permettent d’améliorer la prédiction de la résistance. Des modélisations éléments finis de tronçons de poutres présentant un nœud sont proposées pour justifier la présence de ces paramètres dans les modèles prédictifs et afin de compléter cette base de données par des propriétés mécaniques. Ces modélisations numériques, accompagnées d’un critère de ruine, permettent d’établir des courbes de performances mécaniques en présence d’un nœud. Ces données numériques sont comparées aux résultats expérimentaux afin de vérifier la fiabilité de l’approche proposée. / The bending and tensile strengths of timber can be reduced by the presence of heterogeneities. The knots and the local slope of grain in the surrounding area are the most relevant. Nowadays, the effect of knots reduces the stiffness and the strength of structural elements. The Timber grading is not optimized and does not promote the strongest beams for a timber engineering use. The goal of this study is to evaluate the influence of knots on the bending strength of beams in Maritime Pine, order to improve their timber grading. This work is focused on a database, which takes into account the mechanical and the physical properties of beams and specific geometrical parameters relative to knots detected in elements. Several statistical tools like neural networks are used to define the explanatory variables and their predictive powers of the bending strength. From these analyses, it is shown that some variables characterizing the knots are pertinent and allow the improvement of the prediction of the strength. To justify the presence of these variables in the predictive equations, finite element simulations of single knot are proposed. These numerical computations associated to a fracture criterion allow the establishment of strength performance curves due to the presence of knot in an elementary loaded volume (tension and bending configurations). These numerical data are compared to the experimental results in the aim to verify the reliability of the finite element approach.

A classificação estrutural de peças de madeira possibilita melhor utilização do material, separando as peças de acordo com a sua resistência estimada. Nesse processo é feita a classificação visual, de grande importância no caso de madeiras do gênero pinus, e a classificação mecânica por meio de testes não destrutivos com objetivo de estimar o módulo de elasticidade. Com esse objetivo, além de ensaios de flexão estática, podem ser aplicados métodos dinâmicos baseados em medições das frequências naturais e densidade do material para a determinação do módulo de elasticidade da madeira. Nesse sentido o objetivo deste trabalho foi avaliar a eficiência do aparelho portátil Brookhuis Micro Timber Grader (MTG) na estimativa do módulo de elasticidade por meio de ensaios não-destrutivos de vibração longitudinal. Para tanto, foi utilizado um lote de peças estruturais de madeira da espécie Pinus elliottii classificado visualmente. Os resultados obtidos por esse aparelho foram comparados com os resultados de módulo de elasticidade obtidos em ensaio de flexão estática. Tendo em vista a sua praticidade, é recomendável a utilização deste método para a classificação estrutural de peças serradas de madeira. A classificação visual agregada a classificação mecânica são essenciais para a utilização do Pinus em vigas laminadas coladas, construções industrializadas de madeira e do sistema construtivo em woodframe. / The structural grading of wood allows better use of the material, sorting the specimen according to their estimated strength. In this process the visual grading is a fundamental matter in use of the structural Pinus elliottii and also the mechanical grading obtained by non-destructive methods in order to estimate the modulus of elasticity. For this purpose, in addition to the static bending tests, dynamic methods based on measurement of the natural frequencies and density of the material to determining the modulus of elasticity (MOE) of timber can be applied. The objective of this study was to evaluate the efficiency of portable device Brookhuis Micro Timber Grader (MTG) in estimating the modulus of elasticity by non-destructive testing of longitudinal vibration. It was used structural pieces of wood species Pinus elliottii rated visually. The results obtained by this device was compared with the modulus of elasticity results obtained in static bending tests. Given its convenience and low cost, it is recommended to use this method for structural grading of timber sawn pieces. The visual and stress grading are essencial for the use of Pines in glued laminated timber, industrilization timber constructions and woodframe constructions.