This project report attached here to, entitle “VIBRATION PROPERTIES OF WOOD” was prepared and submitted by Rani Anak Kaba as partial fulfilment of the requirement for the degree of Bachelor of Engineering with Honours in Mechanical Engineering and Manufacturing System is hereby read and approve by:

_________________________ __________________

Assoc. Prof. Dr. Sinin Bin Hamdan Date

Supervisor

Faculty of Engineering

University Malaysia Sarawak

(6)

ACKNOWLEDGEMENTS

First and foremost, the author would like to give thanks to God for the blessing in making this project successful. A sincere gratitude and appreciations to the project supervisor, Associate Professor Dr. Sinin Hamdan for his guidance and expert advices in conducting the experiment and writing the report.

The author also would like to express thanks to Dr. Mohd. Shahril Osman for his assistance in the experiment hardware as well as be the coordinator for the Final Year Project. Additionally, thanks also to Mr. Yahya Sedik for his opinion and recommendations in the project. Not forgetting to the laboratory assistants and other technical staffs who kindly sacrificing their time and their aid during the experiment.

Throughout the project, the author received an endless support and encouragement from her beloved family, Kenny Adams Ajang, and colleagues that always have faith on her for the best outcomes for this project. Nothing words can be expressed for appreciation to all the people who have involved direct or indirectly in the project. Lastly, thank you everyone.

(7)

ABSTRACT

The potential of local wood such as Alan Bunga, Selangan Batu, Belian, Damar Minyak, and White Meranti for musical instruments were investigated. Their physical and mechanical properties were determined in order to obtain their characteristics. The density ρ, specific gravity γ, Modulus of Elasticity E, and internal friction tan δ of each wood were attained from the Free-free Beams Forced Vibration Method. Furthermore, the correlation between E/γ and γ as well as between tan δ and E/γ were plotted to verify the suitability of wood for the musical instruments. Damar Minyak has proved its usage as a guitar where the wood showed the highest E/γ and the lowest tan δ. Alan Bunga and White Meranti resulted in a moderate E/γ and tan δ values that had a potential as a new species for musical instruments. The usage of Belian and Selangan Batu as a material used in construction is undeniable because the outcomes showed the woods had the lowest E/γ and the highest tan δcompared to other woods.

(8)

ABSTRAK

Potensi kayu tempatan seperti Alan Bunga, Selangan Batu, Belian, Damar Minyak, dan Meranti Putih untuk alat muzik dikaji. Sifat-sifat fizikal dan mekanikal dikenalpasti untuk memperolehi ciri-ciri setiap kayu tersebut. Ketumpatan ρ, graviti specifik γ, modulus elastik E, dan geseran dalaman tan δ untuk setiap kayu diperolehi daripada eksperimen “Free-free Beams Forced Vibration Method”. Selain daripada itu, kaitan di antara tan δ dengan E/γ dan E/γ dengan γ diplotkan bagi memastikan kesesuaian kayu untuk membuat alat muzik. Damar Minyak dibuktikan penggunaannya sesuai sebagai gitar di mana kayu tersebut menunjukkan E/γ yang paling tinggi dan tan δ yang paling rendah. Alan Bunga dan Meranti Putih menunjukkan nilai E/γ dan tan δ yang sederhana yang boleh diambil kira sebagai spesis baru untuk alat muzik. Penggunaan Belian dan Selangan Batu sebagai bahan di dalam pembinaan memang tidak dapat dinafikan kerana hasil experimen menunjukkan kayu-kayu tersebut mempunyai E/γ yang paling rendah dan tan δ yang paling tinggi berbanding dengan kayu-kayu yang lain.

(9)

LIST OF FIGURES

Figure 1.1 : Types of Color and Grain Pattern of the Wood 3 Figure1.1.2 : Bending Process of the Shape Side of the Guitar 5

Figure 1.2.1a : Periodic Vibration 10

Figure 1.2.1b : Random Vibration 10

Figure 2.1 : Response Curve 15

Figure 2.2 : The Three Principal Axes of Wood with Respect

to Grain Direction and Growth Rings 16

Figure 2.3 : Modes of vibration: (a) first mode, (b) second mode,

(c) third mode 17

Figure 2.4.2 : Response Curve of the Amplitude-Frequency Relationship 23

Figure 3.1a : Schematic Diagram of Free- free Beams Forced

Vibration Method 26

(13)

Figure 3.1c : Function Generator 27

Figure 3.1d : Fine Tuning 27

Figure 3.1e : Amplifier 28

Figure 3.1f : Sound Level Meter 28

Figure 3.1g : Oscilloscope (Type ADC 216) 29

Figure 3.1h : Free-free Beams Forced Vibration Method Set-up 29

Figure 3.2.1a : Real Voltage and Time Display 33

Figure 3.2.1b : Two Channels of the Real Voltage and Time Display 33

Figure 3.2.2a : Frequency Spectrum Display 34

Figure 3.2.2b : Two Channels of the Frequency Spectrum Display 34

Figure 4.2.1 : The Density of the Five Experimented Woods

and Their Standard Value 39

Figure 4.2.2 : The Specific Gravity of the Five Experimented Woods 41 Figure 4.2.3 : The Modulus of Elasticity of Five Experimented Woods 43 Figure 4.2.4 : The Internal Friction of Five Experimented Woods 45 Figure 4.3a : Relationship between E/γ and Specific Gravity, γ 49

Figure 4.3b : Relationship between tan δ and E/γ 50

(14)

LIST OF TABLES

Table 1.1.2 : Several Types of Imported Woods Used for Making

Musical Instruments 6

Table 2.4.1 : The Density of Several Wood Species 19

Table 2.5.1 : Elastic Ratios for Various Wood Species 21 Table 2.5.2 : The Internal Friction of Several Wood Species 24

Table 3.3 : List of Wood Specimens 36

Table 4.2.1 : The Density of the Five Experimented Woods 38 Table 4.2.2 : The Specific Gravity of the Five Experimented Woods 40 Table 4.2.3 : The Modulus of Elasticity and Frequency Resonance

of Five Experimented Woods 42

(15)

LIST OF APPENDICES

APPENDIX A : Frequency Spectrum of Alan Bunga 58 APPENDIX B : Frequency Spectrum of Selangan Batu 62 APPENDIX C : Frequency Spectrum of Belian 66 APPENDIX D : Frequency Spectrum of Damar Minyak 70 APPENDIX E : Frequency Spectrum of White Meranti 74

(16)

CHAPTER 1 INTRODUCTION

1.1 WOOD

Wood is much known as a preference for making musical instruments. Musical instruments such as guitar, piano, and violin are mainly made from wood. Apart from its attractive color and the beautiful texture of the wood itself, wood is a suitable material to transmit sound when vibrations or resonance occur in the wood.

In order to obtain the essential mechanical properties of the wood for producing the musical instrument, the wood specimen should undergo the vibration test. The vibration test to be used is Free-free Beams Forced Vibration Method, a type of nondestructive testing (NDT) techniques as an alternative method to measure the wave

(17)

Wood is a natural material that had been used in most structures through ages even before the era of metals. Wood product is greatly established in the furniture, flooring, tools, vehicles, decorative objects, and musical instruments. Generally, the main factor for selecting wood in producing a product is the pleasant in appearance in term of its grain pattern and color (see Figure 1.1). Some of the wood also has a pleasant odor for a long time after it is removed from the forest.

Wood can be categorized into hardwoods and softwoods. Hardwoods are the deciduous trees that have broad leaves and usually shedding in the fall. Meanwhile, the conifers are called softwoods that have needles and cones containing seeds.

Hardwoods are commonly harder than softwoods however some hardwoods are softer than softwoods. For example, from the United States, the softwoods such as longleaf pine and Douglas-fir produce wood that is typically harder than the hardwoods basswoods and aspen [1]. Hardwoods are majority used in construction for flooring, architectural woodwork, trim, furniture, pallets, containers, and paneling. Softwoods on the other hands are used in constructions for framing, cabinets, scaffoldings, doors, and musical instruments.

(18)

Figure 1.1: Types of color and grain pattern of the wood [22]

1.1.1 ACOUSTICAL PROPERTIES OF WOOD

Wood has good insulating properties against sound. The cellular structure of wood turns sound energy into heat energy due to frictional resistance of the minute interlocking pores. Wood has a higher damping capacity than most materials because of this feature; wood is a preferred material for building structures when sound damping is required. Wood also reduces the magnitude of resonant vibrations, so wood is used extensively where good acoustics are required, for example concert venues, music suites, halls, and meeting rooms.

(19)

Although wood has a good sound attenuation propertywhich tends to absorb and dissipate vibrations, yet wood is still an incomparable material for such musical instruments such as violins, guitars, and pianos.

1.1.2 WOOD FOR MUSICAL INSTRUMENTS

In musical instrument, low damping due to internal friction and high damping due to sound radiation is desirable. For such cases, wood meet the requirement which provides high damping due to sound radiation and low internal friction.

Moreover, wood is easier to bend according to the shapes rather than the metal, whereas the bending process of the wood do not require such a technology like the bending process of the metal (see Figure 1.1.2). However, each type of wood bends differently. They have unique responses to water, heat and the severity of the curve being bent. The easiest woods to be bent are Plain Indian Rosewood and Plain Maple.

Rosewood has resins that make it pliable, and maple is tough. On the other hand, Plain Mahogany and Walnut are quite difficult to be bent. These woods are brittle and resist bending if the conditions are not right. The hardest woods to bend are Figured woods.

Figured Curly Koa is particularly tricky to bend. Curly Maple and Figured Rosewood (particularly Brazilian rosewood) bend just a little bit easier than Curly Koa [2].

(20)

Diverse species of wood have different reactions to sound and it is a vital consideration while selecting species for musical instruments [3]. Local wood such as Bintangor or its scientific name Calophyllum spp., Kayu Hitam or Diospyros celebica Bakh., and Merbau or Intsia bijuga are among the woods selected for making musical instruments.

Unfortunately, most of the musical instruments are made from the imported woods such as Eastern spruce and Sitka spruce (see Table 1.1.2). This project aims to identify for a new source from the local woods as to replace the role of imported woods.

The important characteristics in the woods for making the musical instruments are used for a guideline to decide the new suitable woods.

Figure 1.1.2: Bending Process of the Shape Side of the Guitar [2]

(21)

Table 1.1.2: Several Types of Imported Woods Used for Making Musical Instruments

Ref: [1], [23], and [24]

Common

Name Scientific Name Origin Uses Asanfona

Ref: [23]

Aningeria spp.

Africa Musical instruments, heavy construction, marine, furniture,

flooring Beech

ibid

Fagus spp. UK, Europe, North America

Furniture, flooring, musical instruments

Blackwood, African

ibid

Dalbergia

melanoxylon Africa Musical instruments, craft products

Boxwood, European

ibid

Buxus

sempervirens Europe Turnery, craftwork, sports goods, musical instruments Cherry,

European ibid

Prunus spp. UK, Europe, North America

Specialized crafted furniture and decorative work, musical

instruments Ebony

ibid

Diospyros spp. Africa, Asia Cutlery handles, musical instruments, craftwork.

Hornbeam ibid

Carpinus betulus UK, Europe Minor items, musical instruments Jacareuba

ibid

Calophyllum spp.

South America

General purpose timber, musical instruments

Maple ibid

Acer spp. North America Flooring, musical instruments Persimmon

ibid

Diospyros virginiana

North America

Decorative ware, musical instruments, turnery Rosewood

Dalbergia spp. Africa, South America, India

Furniture, musical instruments

(22)

Common Name

Scientific

Name Origin Uses

Sitka spruce [1]

Picea sitchensis

North America, Alaska

Furniture, millworks, sash, doors, blinds, boats, sounding boards for

pianos Eastern

spruce

ibid

Picea Rubens (red) Picea Glauca

(white) Picea Mariana (

black)

New England Lake States Lake States

Framing material, general millwork, boxes and crates, piano sounding boards

Spanish- cedar

Ref: [24]

Cedrela spp.

Mexico and Argentina

Millwork, cabinets, fine furniture, musical instruments, boat building, patterns, sliced- and rotary-cut veneer,

decorative and utility plywood, cigar wrappers, and cigar boxes Brazilian

Rosewood

ibid

Dalbergia

nigra South America (Brazil)

Decorative veneers, fine furniture and cabinets, parts of musical instruments, brush backs, knife and other handles, fancy turnery, piano cases, marquetry Cocobolo

ibid

Dalbergia retusa

Central America (Mexico)

Highly favored in the cutlery trade for handles, inlay work, brush backs, musical and scientific instruments, jewelry boxes, chessmen, and other

specialty items Honduras

Rosewood

ibid

Dalbergia

stevensonii Belize(British Honduras)

Parts of musical instruments including percussion bars of xylophones, veneers

for fine furniture and cabinets, brush backs, knife handles, fine turnery, many

specialty items

(23)

1.2 VIBRATION

Vibration is the study of the repetitive motion of objects relative to a stationary frame of reference or nominal position where usually at equilibrium state [4]. The swinging of a pendulum or playing a guitar is typical example of vibration applications.

The applications of vibration effect tremendously in the engineering field. To prevent devastation by the vibration problems in most mechanical works, the engineer tries to design the machine or engines to minimize the unbalance caused by the vibration.

Common Name

Scientific

Name Origin Uses

Alerce

[24]

Fitzroya

cupressoides Central part of Chile, Province of Chubut in

Southern Argentina

Shakes and shingles, general construction, pencil slats, musical instruments, vats and

tanks, lumber cores, and furniture components Trebol

Macawood

ibid

Platymiscium spp.

Continental tropical America from Southern Mexico to the Brazilian Amazon

region, and Trinidad

Fine furniture and cabinet work, decorative veneers, musical instruments, turnery, joinery, specialty items (violin bows,

billiard cues) Honduras

Mahogany

ibid

Swietenia

macrophylla Southern Mexico southward to Colombia, Venezuela

Fine furniture and cabinetmaking, interior trim,

paneling, fancy veneers, musical instruments, boat

building, patternmaking, turnery, and carving

(24)

The vibration that occurs in the wood specimen can provide information about mechanical properties of the wood including the elastic properties, damping properties, and energy dissipation from the wood. Elasticity implies that deformations produced by low stress are completely recoverable after loads are removed [5]. Plastic deformation or failure occurs when the specimen are being loaded to a higher stress levels. Damping properties occurs when the driving force is removed; the successive amplitudes of vibration will decrease. The energy dissipation is defined as energy dissipated partly by radiation of sound and partly in the form of heat by internal friction [6]. The internal friction is a complex function of temperature and moisture content.

Vibration can be destructive and should be avoided, or else it also can be greatly useful and desired. In this paper, the usage of vibration principles is extremely applicable as to achieve the desirable outcome.

1.2.1 FUNDAMENTAL OF VIBRATION

Basically vibration occurs in two categories that are periodic vibration and random vibration. Periodic vibration is a motion occurring at equal intervals of time.

Harmonic motion is an example of periodic vibration (see Figure 1.2.1a). The motion is represented by force functions where the time variation is a sine or cosine function.

Random vibration on the other hand is a nondeterministic vibration (see Figure

TABLE OF CONTENTS

APPROVAL SHEET

ACKNOWLEDGEMENTS

ABSTRACT

ABSTRAK