Anisotropy Characterization of Structural Flakeboards with Ultrasonic Methods

The aim of this research was to study the anisotropic behavior of structural flakeboards using ultrasonic velocity and acoustic emission methods. One full-size board (3,050 x 1,850 x 19 mm) was analyzed for which the orthotropic model was assumed. Ultrasonic velocities of longitudinal and transversal bulk waves were used to estimate the nine stiffnesses. The measurements were performed on specimens of standard size cut from the board. Surface wave velocities were measured on the full-size board along and across the flake alignment direction. Furthermore an acoustic emission technique of breaking 0.5 mm pencil lead on the surface of the specimens was employed. Several parameters of acoustic emission were measured (duration, count number, energy, peak amplitude, rise time) on specimens cut parallel and perpendicular to the direction of flake alignment. The anisotropy was estimated as the ratio of velocities of bulk and surface waves and of acoustic invariants, as well as the ratio of acoustic emission parameters

Handbook of materials for wind musical instruments

This book addresses key questions about the materials used for the wind instruments of classical symphony orchestra such as flutes, clarinets, saxophones, oboes, bassoons and pipe organs. The content of this book is structured into four parts. Part 1- Description of materials for wind instruments deals with wood species and materials for reeds used for making clarinet, oboe and bassoon- and, with metallic materials and alloys for - horn, trumpet, trombone, etc. Auxiliary materials associated with the manufacturing of wind instruments are felt, cork, leather and parchment. Part 2- Basic acoustics of wind instruments, in which are presented succinctly, some pertinent aspects related to the physics of the resonant air column. An important aspect discussed is related to the effect of wall material on the vibration modes of the walls of wind instruments. The methods for measuring the acoustical properties of wind instruments are presented. Part 3- Manufacturing of wind instruments, describes the technology used in manufacturing metallic tubes and pipes made of wood. Part 4 - The durability and degradation of materials addresses data about methods for cleaning wind instruments, studies factors producing degradation of organ pipes, describes methods of conservation and restoration of brass instruments and of historical pipe organs. Finally, the properties of marble are described, being the only one nondegradable and sustainable material used for pipes for organs

Détermination du module d'Young du bois par une méthode dynamique sur carottes de sondage

International audienc

The effect of hydrostatic pressure on physical properties and microstructure of spruce and cherry

International audienceThe effect of hydrostatic pressure on the density, the ultrasonic velocities and the microstructure of spruce and cherry wood has been studied. Generally speaking, under hydrostatic pressure wood becomes less heterogeneous and less anisotropic than natural wood. In spruce, crushing and buckling of the thin-walled cells in the earlywood takes place. This also has the effect of disrupting the medullary rays, which assume a zig-zag path through the structure. Cherry has a much more homogeneous structure, and the main effect of the hydrostatic pressure is compaction of the vessels by buckling of the walls. The fibres are scarcely affected by the treatment. The width of the earlywood zone decreased after the application of pressure by 26% in spruce, and by 11% in cherry. The average density was increased by the hydrostatic pressure by 26% for spruce and by 46% for cherry. The densitometric profile of spruce demonstrates significant changes following the pressure treatment, with the minimum density DMin increasing and the maximum density DMax decreasing. For cherry, the densitometric profile is shifted rather uniformly towards higher densities, and the annual ring profile is spatially slightly compacted but otherwise similar to that of untreated wood. The anisotropy of wood (expressed by the ratio of acoustic invariants) decreased by 56% for spruce and by 33% for cherry. The structural damage in spruce is predominantly found in the radial (R) direction, and this corresponds to a reduction of 73% in the velocity of the longitudinal ultrasonic waves in the radial direction, VRR. In cherry, the structural damage is mainly in the transverse, T direction. The velocity of the longitudinal ultrasonic waves in the transverse direction, VTT is reduced by 44%. The medullary rays in cherry seem to be the most important anatomical feature influencing the propagation of ultrasonic wave

Détermination indirecte des coefficients de diffusion de la vapeur d'eau dans les directions tangentielle et radiale du bois de hêtre

Indirect determination of tangential and radial steam diffusitivity of beech. In order to characterize the diffusion process of water in the hygroscopic range of wood, we propose to evaluate initially the diffusion coefficients of water vapour in the three orthotropic directions of wood. The diffusion coefficients of water vapour are deduced from the diffusion coefficients of an inert solute (helium) measured in a diffusion cell, type Wicke and Kallenbach, being in an unsteady state. The diffusion coefficients in the radial and tangential directions measured at 30 °C are independent of absolute moisture content of wood. The values we find agree with ranges of variations given in the literature. The diffusion coefficient in the radial direction is roughly higher than the diffusion coefficient in the tangential direction, probably due to the rays in the radial direction.Afin de caractériser le transport diffusionnel de l'eau dans le domaine hygroscopique du bois, nous proposons d'estimer initialement les coefficients de diffusion de la vapeur d'eau dans les trois directions orthotropiques du bois. Les coefficients de diffusion de la vapeur d'eau sont déduits des coefficients de diffusion d'un soluté inerte (hélium) mesurés dans une cellule de Wicke et Kallenbach évoluant en système transitoire. Les coefficients de diffusion dans les directions radiales et tangentielles mesurés à 30 °C sont indépendants de l'humidité absolue du bois. Les valeurs trouvées sont compatibles avec les intervalles de variations donnés dans la littérature, le coefficient de diffusion radial du bois de hêtre étant sensiblement plus élevé que le coefficient de diffusion tangentiel, probablement par la présence de rayons ligneux en direction radiale

Tomographie ultrasonore pour les arbres sur pied

Ultrasonic tomography on standing trees. Ultrasonic tomography was used for the detection of degradation of transversal section of a beech, attacked by white decay. The image reconstruction of the transversal section of the tree in 2D was obtained with a software, which used the values of ultrasonic velocities measured at different heights from the ground. The attacked wood is characterised by low velocities. The measurements were performed with special transducers of 1 MHz, without damaging the bark of the tree. To improve the readings of the signals, a frequency analysis was performed. The ultrasonic tomographies were compared with the corresponding photographic images and with data obtained with a “Resistograph”. A good agreement between ultrasonic tomographies and photographs was observed. The image resolution is between 4 and 5 cm. Presently, this is the best resolution ever obtained with an acoustic nondestructive method on a standing tree.La tomographie par ultrasons a été utilisée pour détecter l’état de dégradation de la section transversale d’un tronc de hêtre, attaqué par une pourriture blanche. La reconstitution de l’image du tronc en 2D a été faite à partir d’un logiciel qui utilise les valeurs de vitesses de propagation des ultrasons à travers la section de l’arbre. Le bois dégradé est caractérisé par des valeurs faibles des vitesses. Les mesures ont été effectuées à travers l’écorce de l’arbre, à trois hauteurs du sol, avec des transducteurs spéciaux de fréquence d’émission de 1 MHz. Dans le cas d’un signal trop entaché par le bruit, une analyse en fréquence a été effectuée. Les tomogrammes ultrasonores ainsi obtenus ont été comparés avec les photographies des sections correspondantes et avec les données obtenues par mesure de résistance à la pénétration d’une aiguille, avec un « Résistograph ». Aux faibles valeurs de la résistance à la pénétration correspondent des valeurs faibles de vitesses. Une bonne correspondance entre les tomogrammes et les photographies a été constatée. La résolution de l’image tomographique est comprise entre 4 et 5 cm. À l’état actuel du développement des techniques de détection non destructives acoustiques des défauts sur les arbres sur pied, cette résolution est la meilleure jamais obtenue

Dynamic Analysis of the Musical Triangles—Experimental and Numerical Approaches

This paper addresses the experimental and numerical dynamic analysis of curved bars used as percussion musical instruments. These structures are known as triangles, being made of various metal materials. The study was based on the experimental analysis of the dynamic response over time and the frequency of three types of triangles, different in material and size. Subsequently, finite element analysis of the same structures modeled with the SimCenter 12 program was performed. The results were compared, highlighting the contribution of material type and geometry in obtaining vibration modes, frequency spectrum, and structural damping coefficient. Between the experimental and the numerical analysis, the obtained errors were below 2.2% in terms of their natural frequencies. The study also highlights the complementarity of the two methods in understanding the vibration modes of triangles