Voichita Bucur

RMIT University | RMIT · Department of Physics

The study investigates the effect of the type of varnish and the number of layers on some acoustic properties of the resonance spruce in combination with the changes produced in some physical, morphological, and chemical properties of wood. In addition to color changes and surface chemistry, the surface roughness and morphology are modified by the...

The mechanics, dynamics and acoustics of musical instruments concern scientists from different fields, such as physics, mechanics, acoustics, psychology, and music, as well as musical instrument manufacturers, who use these factors to not only understand and explain the phenomena that take place inside and outside of musical instruments as a result...

Acoustics is a field with significant application in wood science and technology for the classification and grading, through non-destructive tests, of a large variety of products from standing trees to building structural elements and musical instruments. In this review article the following aspects are treated: (1) The theoretical background relat...

The paper deals with dynamic analysis of a two types of musical triangles, one made from stainless steel and other from alloy. The experimental method applied in this study consisted in exciting the structure with the impact hammer and recording the acoustic signals with the help of the microphone located near the sample, the acquired signals being...

The aim of this paper is to highlight the correlations between the anatomical quality of the resonant wood (spruce and maple) and the dynamic response of the violins. In this study were analyzed 28 violins, seven from each structural quality class of wood (A, B, C, D), according to the classification made by manufacturers. The violins were analyzed...

Numerous studies are dedicated to the dynamics of the guitar, the challenge of interdisciplinary researchers being to find a better approach to the design and construction of the classical guitar in correlation with the development of mathematical models of dynamic and acoustic behavior. The aim of this paper is to present a comparative study on dy...

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 mat...

From a constructive and functional point of view, the violin body is a structure with thin walls having the role of amplifying the musical sounds and consists of an arched top and back plates, the ribs and the linings with thicknesses about 100 times smaller than the overall dimensions of violin body. The present research proposes to investigate: (...

The paper deals with numerical modal analysis of a kinked bars similar with an open triangle, with different sizes, angles and diameters of bar. Using SIMCENTER software, the first step was to design the geometry of each type of structure, then discretization of model in finite elements and assigning properties of material (in this case, Al alloy)....

Identifying high-grade valuable wood resources by the visible individual traits of trees is a challenge for foresters and a requirement for sustainable resource management. The aim of this study was to identify the most relevant phenotypic descriptors of the acoustic quality of Norway spruce standing timber. Two highly valuable Norway spruce (Picea...

The aim of this article is to correlate the experimental modal analysis (EMA) with finite element analysis (FEA) to study the effect of wood species on vibration modes of violin plates made of spruce and maple. For EMA, five violin plates each made of spruce and maple were tested (curly maple, quilted maple, common maple with regular and irregular...

Classical guitar necks were submitted to 40, 65 and 80% relative humidity (RH) during time periods ranging from 24 h to several months, and moisture-induced deformations were observed. Different types of classical guitar necks were investigated in terms of structure and reinforcement. The influences of the wood species and the neck reinforcements o...

The aim of this paper is to use dynamic mechanical analysis to examine the modifications of the elasto-dynamical properties of a composite made of small waste oak particles of various sizes (0.04 and 1 mm) and a polyester resin (440-M888 POLYLITE), subjected to photo-degradation by UV radiation and thermal degradations induced by temperature variat...

Natural ageing of wood has a critical influence on ageing of musical instruments. Several possible factors can affect natural wood ageing. These include the combined effects of thermal oxidation by air oxygen, acid hydrolysis of bound water contained in cell walls, together with other acids contained in the wood. Ageing of structural parts of music...

Restoration interventions on historical musical instruments need a deep understanding of physical phenomena at the origin of the damages to be repaired and of the physical, mechanical and chemical properties of the materials composing the system. Loss of original material can be produced as a result of structural modifications during restoration. T...

The development of composite materials as substitutes for wood in musical instruments was motivated by numerous factors, such as the fragility of instruments during handling and transportation, their sensitivity to temperature and humidity variations, the scarcity of wood resources (resonance spruce and tropical hardwoods), the high variability of...

The plates are the main constitutive elements of string instruments. A string musical instrument is a complex structure enclosing an air cavity, which is part of the system. Different modes of vibrations of plates and of string instruments can be studied with optical methods. The most popular method for the study of plates’ vibrations is with Chlad...

Strings of musical instruments can be excited by plucking, bowing or striking and can vibrate in several modes. The main parameters which characterize the strings are the diameter, the length, the mass per unit length, the stiffness, the normal playing tension and the inharmonicity of the overtones. Inharmonocity is favoured by short, thick and hig...

Old Italian violins and other period musical instruments are significant cultural and art objects invested with passion and a wide range of other musical and historical meanings. The quality of these instruments is considered superior to that of the new instruments. Sometimes this judgment may be biased by the extraordinary legends of these instrum...

Varnish is used to give a shiny transparent finish to the surface of the musical instrument having an aesthetic and protective role. The varnish used by the Italian masters of the 16th and 17th century was credited with “extraordinary acoustic” properties. Varnishes of Old Italian instruments have three basic characteristics: transparency, quality...

The science of string musical instrument is greatly dependent on materials science. Mathematics and physics make an excellent tool for teaching the science of string instruments at different levels ranging from non-scientists to students trained at the highest academic level. Materials science and engineering, and on the other hand, arts programs i...

A concert harp soundboard is made from 15 small planks of spruce resonance wood with regular annual ring width of 2-3 mm. The thickness of the soundboard varies from 12 mm (bass) at the bottom to 2.5 mm at the top (treble). The outer surface of the soundboard is covered with a sheet of veneer (1 mm thickness) in spruce or in a precious species, to...

A large variety of materials are used traditionally for constructing string musical instruments in the Western cultural tradition. Since the last decades of the XIX th century it has been recognised that mechanical and acoustical properties of materials are the most relevant for these instruments. Wood is the predominant material. Other materials s...

The bridge, the soundpost and the bass bar of the violin and of all instruments from the violin family have complementary acoustical and mechanical functions for transmitting strings' vibration to the body of the instruments. The chief function of a violin’s bridge is to transform the motion of the vibrating string into periodic driving forces whic...

Dendrochronological analysis is a relatively new tool for dating old historical musical instruments. The process of dating musical instruments is based on the comparison between the ring width series seen on the top of the string instrument and compared to the existing master chronology. Norway spruce (Picea abies) used for the top of string instru...

The pieces used for fitting the strings for the instruments from the violin family are the tailpiece, the neck, the fingerboard, the nut, the pegs and the endpin. These pieces are made in hardwood spieces – ebony, boxwood, rosewood, pernambuco or curly maple. New materials (graphite composites, plastics) has been used to provide proper weight requi...

In a musicians view “good” or “bad”, “old” or “new” descriptions of violins can be related to their perceived tone quality and their acoustic properties. For more than two centuries the Stradivari and other Cremonese violins fascinated the imagination of musicians, scientists and craftsmen. Today, numerous recordings exist allowing subjective and o...

The structural elements of the modern bow used for the stringed instruments from the violin family are the bow stick, the hair, the frog, the button or the screw and the pad. The parameters which define the bow are the length, the weight, the balance, the playability and the potential for giving power to the sound and the aesthetics. The stick of t...

Traditional wood species used for violins and other instruments of this family are spruce resonance wood, also called Norway spruce, or spruce tonewood known under the scientific name of Picea abies that are used for the top, and curly maple (Acer pseudoplatanus) for the belly, ribs and neck. Macroscopically, resonance spruce for violins has a very...

Musical instruments are cultural objects. Their study is as much a cultural study as it is about the physics, the acoustics and the materials used for their construction. The manufacturing of musical instruments, their shape, their decoration and their iconography is characteristic of the aesthetics of the musicians they serve and of the society in...

The soundboard of the modern piano is a thin plate made in resonance spruce of about 7-9.5 mm thickness that underpins the strings and the cast iron plate and rests on the rim braces. The ribs support the soundboard on the underside and on the opposite side the soundboard has two bridges over which the strings are stretched. The soundboard is made...

The potential of materials derived from natural or sustainable forest resources for musical instruments has been discussed. The quality of wood species from natural forest resources, having acoustical properties unsuitable for the production of musical instruments can be improved by biological, chemical or physical treatments. The biological treatm...

Musical instruments which are part of our rich cultural heritage are unique and therefore strict rules of preservative conservation must be applied. Preservative conservation is understood as any measure that prevents damage or reduces the potential of it. Conservative preservation is characterized by three stages: revelation, investigation and pre...

This book addresses core questions about the role of materials in general and of wood in particular in the construction of string instruments used in the modern symphony orchestra – violins, violas, cellos and basses. Further attention is given to materials for classical guitars, harps, harpsichords and pianos. While some of the approaches discusse...

This article reviews Delamination in Wood, Wood Products and Wood-Based Composites by Voichita Bucur , New York, 2011. 401 pp. Price: $209 (hardcover) ISBN: 9789048195497

Delamination phenomena in manmade composites (Tay 2003, Sridharan 2008) as well as in wood and wood-based composites have received much attention from scientists and practitioners due to serious technological implications and obvious scientific curiosity for this subject.

In this chapter we shall describe the aspects related to delamination in composites revealed by a vibration-based approach and related to the local and global damage detection. The local damage detection is performed with an ultrasonic technique, with Lamb waves, while the global damage detection is based on a model – based method using low frequen...

In Material Science, delamination is defined as a sub critical damage to the interfaces between the plies in a laminate composite that causes a reduction in the load carrying capacity of composite (Morris 1992). The terms which describe delamination in wood and wood- based composites are numerous and often confusing for multiple reasons (the use of...

The damage evolution related to fracture phenomena in wood can be expressed at several internal length scales such as atomic, micro, meso and macro scales. Damage initiates on the atomic scale and reaches relevance for larger scales while it propagates, leading to failure when reaching the macro scale. In this section we focus our attention on aspe...

Wood – based composite panel products (WBCP) are manufactured from veneer, wood particles, strands or fibres bind together with different types of adhesives such as urea-formaldehyde resin, phenol-formaldehyde resin, melamine formaldehyde resin, methylene diphenyl diisocyanate or polyurethane resins. The nature and the quality of the raw material a...

Fracture Mechanics concept has been applied to wood material as reported during more than fourthly years, by numerous references, review articles and books. Some of them are cited below. (Attack et al. 1961; Porter 1964; Schniewind and Centeno 1973; Schniewind and Lyon 1971, 1973; Schniewind and Pozniak 1971; Leicester 1971, 1973, 1974; Pearson 197...

The term “weathering” (Feist 1982) defines any of the physical, mechanical or chemical process by which wood or wood based products undergo slow degradation induced by the weather (sunlight, wind, precipitations, diurnal and seasonal changes in relative humidity, atmospheric pollution, etc). Knowledge about weathering durability comes from practica...

The last two decades of the 20th century have been characterized by an extraordinary development of different methodologies for nondestructive evaluation of wood products, which has succeeded in the imaging of the internal structure of wood at both macroscopic and microscopic levels. The efforts devoted towards the development of nondestructive tec...

In the last quarter century, delamination has come to mean more than just a failure in adhesion between layers of bonded composite plies that might affect their load-bearing capacity. Ever-increasing computer power has meant that we can now detect and analyze delamination between, for example, cell walls in solid wood. This fast-moving and critical...

The occurrence and distribution of tension wood in trees can result in major defects in manufactured wood products. The nondestructive detection and location of tension wood in trees and logs is a major interest for hardwood industry in Australia. This paper proposes a combined acoustic method using ultrasonic waves and stress waves for 2D imaging...

One of the most common biological composites is wood material. This natural orthotropic like material is characterized by a high anisotropy determined by the special disposition of the microstructure elements. The anisotropy of wood can be described in various ways using the values of ultrasonic velocities of bulk waves (longitudinal and shear) obs...

Trees can reduce noise by sound reflection and absorption and this is the first book bringing together the widely scattered literature on noise abatement by urban trees. The book covers topics including the dendrological characteristics of trees, factors affecting sound propagation in forest belts, protection against traffic noise from highways, ra...

The design of a comfortable environment must pay attention to the “sound-scape” which should complete the “landscape” design. The meanings of sound-scape are social, historical, cultural and environmental. A positive impression on the urban soundscape is produced by large vegetation areas, belts of trees, public gardens and parks. In urban resident...

From the reviews of the 1st edition: "It will surely remain the most comprehensive work in this field for a long time to come. It belongs on the bookshelf of every material scientist and structural engineer." CAS Journal, USA "...[T]he author has done an admirable job, collecting, organizing, and reviewing the disparate literature on most aspects o...

Ultrasonic technique was used for the mechanical characterization of two types of commercial particleboards. The elastic constants were calculated in the hypothesis of orthotropic symmetry. The specimens were prepared in parallel (direction 1) and perpendicular (direction 2) versus the technological direction of the board production and 45° in plan...

The aim of this study is to assess wood quality of standing trees with ultrasonic velocity methods. The ultrasonic techniques currently used are: scattering based techniques that use travel time and other wave parameters for measuring the elastic constants of wood, and ultrasonic tomographic imaging techniques which seek to provide a high resolutio...

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 characteris...

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...

High resolution imaging of wood requires the development of measurement techniques for nondestructive characterization of this material. The techniques, ranging from ionizing radiation to thermal techniques, microwaves, ultrasonics and nuclear magnetic resonance, provide excellent means of obtaining information about the internal structure of wood....

The aim of this article is to study the ultrasonic propagation phenomena in Eucalyptus lumber taking into consideration the dispersion of ultrasonic waves induced by the size of boards. Two types of waves were selected: surface waves and longitudinal waves of 45kHz frequency. The boards of 2m length in air dry condition were selected to have well d...

Nuclear magnetic resonance imaging was first developed for medical applications. However, since 1980, an increasing number of researchers have reported applications of this technique to materials science using standard NMR spectrometers, in which modifications had been made, and computing facilities had been adapted to produce images. Every measure...

The microwave scanning technique is a relatively new tool for the characterization of wood materials. During the last 15 years, considerable progress has been achieved in the design of scanning probes and in image interpretation (Martin et al. 1987; Filippini et al. 1990; Chazelas 1991; Yokoyama and Norimoto 1996; Golosovsky et al. 2000; Kaestner a...

Neutron radiography is a nuclear method for wood structure imaging. Relevant aspects about the physics of neutron scattering and about materials science-oriented neutron scattering studies have been published in reference books and articles such as: Guinn and Lukens (1965), Bacon (1975), Garret and Berger (1977), Kostorz and Lovesey (1979), Nicklow...

Ultrasonic imaging is a technique widely used to reconstruct the properties of the materials under inspection from global wave propagation data. Acoustic tomograms provide an excellent noninvasive means of obtaining information about inhomogeneous media as noted by many investigators (Kak 1979; Herman 1980; Greenleaf 1981; Crawford and Kak 1982; De...

Computed tomography scanning with ionizing radiation provides three dimensional information about the internal inhomogeneous structure of the specimen under test in a nondestructive, noninvasive and rapid manner. This technique is a “cornerstone of materials characterization” (Kinney et al. 1988). The aim of computed tomography is to create a preci...

Thermography is a generic term for a variety of techniques used to visualize the temperature at the surface of objects and refers to imaging of a full-field temperature distribution. Active heating or passive heating procedures can be used for thermographic imaging of solids (Liezers et al. 1985; Puttick 1987; Vavilov 1992). Thermography provides a...

1 Introduction.- 2 Ionizing Radiation Computed Tomography.- 3 Thermal Imaging.- 4 Microwave Imaging.- 5 Ultrasonic Imaging.- 6 Nuclear Magnetic Resonance.- 7 Neutron Imaging.- References.- List of Notations.- Color Plates.

Mechanical behaviour of wood considered as an orthotropic solid can be determined with ultrasonic technique. The propagation phenomena in wood are complex and theoretically are regulated by Christoffel's equation. Three type of waves can propagate in wood. During the propagation phenomena three slowness sheets are observed, corresponding to a fast...

Wood is a natural, inhomogeneous, anisotropic composite material whose elastic behavior can successfully be described as that of an orthotropic continuum. Christoffel's equation relates ultrasonic propagation velocities to the elastic constants. Six of the nine independent constants can readily be determined from velocity measurements in the direct...

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 t...

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...

The 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....

Three methods (weight loss, ultrasonic and compression strength) were used for the evaluation of degradation of wood treated with actinomycetes.

The aim of this research is to study the ultrasonic waves birefringence in three wood‐based composite panels, chipboards, oriented strandboards, and medium‐density fiberboards, for the characterization of their global elastic and structural properties. Shear waves of 1 MHz were used to study the ultrasonic birefringence and to determine the shear t...

Acoustic properties of spruce resonance wood can be thoroughly measured by the ultrasonic technique. It is possible to measure six ultrasonic velocities and to deduce the corresponding elastic constants on a small cubic specimen. However, as previously stated (Bucur 1995), spruce resonance wood has a very high ultrasonic velocity in fiber direction...

Juvenile wood characteristics of multiseriate and uniseriate rays of five species of the genus Acer were studied on young trees from France and Canada. Ray height, width, number in width of cells and proportion/mm2 were determined for the earlywood. Variance analysis was used to discriminate the variability of the characteristics of rays. Simple re...

Ultrasonic techniques are used to characterize the anisotropic and nonlinear elastic behavior of wood and rock and to interrogate the structural properties of these materials. For elastic anisotropy two types of experiments are performed, namely qP-wave velocity measurements on spherical samples in about 100 directions of propagation rather regular...

Dynamic thermomechanical analysis was used to control and investigate the viscoelastic behaviour, as expressed by the dynamic storage modulus and by tanδ, of wood joints bonded with crosslinking thermosetting adhesives. Phenol formaldehyde (PF), melamine–urea–formaldehyde (MUF), resorcinol–formaldehyde (RF), tannin–formaldehyde (TF) and tannin–hexa...

Physical methods have been used to compare the mechanical properties of wood based panel products in relation to their microstructure. Three types of composites were considered:medium density fiberboard (MDF), oriented strandboard (OSB) and chipboard (CB). The overall elastic properties of panels were assumed to be orthotropic. The diagonal terms o...

X-ray microdensitometric analysis was employed for the detection of fungi attack in wood of pine and beech in comparison with the studies of specimen weight loss tests. Two species of fungi were used: Gloeophyllum trabeum (Pers.:Fr. Murrill) and Trametes versicolor (L.:FU. Pilat). We select these species to induce typical decay attack mainly on cel...

This article presents several acoustic methods effective for examining physical properties of wood , as a living material. Three main aspects are commented : "Environmental acoustics " associated with the propagation of acoustic waves in urban forest "Material characterization " related to anisotropy, global and local mechanical properties of solid...

The main interest in acoustic microscopy arises from the direct interaction between the wave and the elastic properties of the material through which it propagates. Acoustic waves permit the exploration of the region of specimen beneath the surface.

Programme pluriannuel de recherches financé par la Région Rhône-Alpes. Rapport final des recherches effectuées par l'INRA*INRA, Centre de Nancy Diffusion du document : INRA, Centre de Nancy

The basis of the ultrasonic evaluation of the viscoelastic behaviour of wood is associated with measurements of velocities and of attenuation coefficients. The dispersion equation for anisotropic solids relates the complex elastic constants, the velocities and attenuations. The numerical significance of attenuation coefficients depends on the speci...

X-ray microdensitometry and ultrasonic velocity were used to study radial variation of selected physical properties in wood of Pinus taeda. The analysed physical properties were earlywood and latewood density and stiff­ nesses in longitudin al and tangential aniso­ tropic directions. calcula ted as the square of velocity multiplied by density. X-ra...

It is an understatement to say that wood is an unique material used in the art of musical craftmanship. Under the generic name of "resonance wood" are admitted all species used for musical instruments. In this note our comments are limited to spruce and curly maple for violins. The violin makers traditionally select their boards according to the si...

A method of evaluating the attenuation of ultrasound in wood over a range of frequencies and angle of incidence with respect to the three principal elastic directions of the material is described. The influence was considered on velocity. A continuous wave transmission technique was used to measure ultrasonic velocities and attenuation coefficients...

Acoustic emission and acoustic stimulation techniques were used in wood science and technology [1] as a control tool on trees, solid wood under stress, wood based composites or as a monitoring system of different technological processes (kiln drying, structural defects detection, wood machining).