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P. 48
ectric guitar neck from densified poplar? Experimental and numerical
analysis
Václav Sebera 1, Marica Mikuljan 1, Michael Mrissa 1,2, Andreja Kutnar 1,2, Rok Prislan 1,2, Jaka
Gaspar Pečnik 1,2
1. InnoRenew CoE, Livade 6, 6310 Izola, Slovenia, vaclav.sebera@innorenew.eu
2. University of Primorska, Titov trg 4, 6000 Koper, Slovenia
Electric guitar necks (EGNs) are usually made of hardwoods (i.e., maple, ash, etc.), including protected
exotic species coming from overseas (mahogany, etc.), due to their aesthetics, high stiffness and density.
Additionally, EGNs typically include a truss rod – a metal bar stiffening the neck against bending caused
by string tension. In order to reduce the environmental impact of guitar production, we believe that EGNs
can be made from local and fast grown plantation wood modified using a thermo-hydro-mechanical
(THM) process. This approach for EGN production may be (i) more convenient due to higher mechanical
properties of densified wood while preserving similar vibrational performance; (ii) more economical due
to using local and cheap resources and absence of a truss rod; (iii) more environmentally friendly due
to reduced logistics and energy costs. To analyze the hypothesis resulting from (i), we performed both
experimental tests and numerical analyses. Experiments consist of poplar wood densification (dens. ratio
1.5) to obtain the elastic orthotropic material model of densified poplar suitable for finite element analyses
(FEA). We aim to perform compression tests accompanied with digital image correlation, which will
provide a set of elastic material coefficients – 3x normal elastic moduli (EL, ER, ET) and 3x Poisson’s ratios
(μLR, μRT, μLT); shear elastic moduli (GLR, GRT, GLT) were calculated theoretically. Developed material
models were employed in FEA of (i) guitar neck deflection induced by string tension and (ii) modal analysis
of a neck including sensitivity study for the role of density and elastic moduli on eigenfrequencies. FEA
will use the following material scenarios: poplar, densified poplar, and maple. Preliminary results of the
FEA with maple properties are shown in Figure 1. Figure 1a shows how deflection and PS1 changes with
change of EL – deflection decreased 40 % and PS1 increased ~ 11 % as EL increased from 12.4 GPa to 22
GPa. Figure 1b shows the eigenfrequencies decrease with density but increase as EL increases (1st freq
17.4 %, 2nd freq. 21.4 % and 3rd about 27 %).
Keywords: densified poplar, orthotropic material model, finite element analysis, electric guitar, acoustics
Acknowledgement
The authors acknowledge the European Commission for funding the InnoRenew project (grant agreement
739574) under the Horizon2020Widespread-2-Teaming program and the Republic of Slovenia (investment
funding from the Republic of Slovenia and the European Regional Development Fund).
INNORENEW COE INTERNATIONAL CONFERENCE 2021
48
analysis
Václav Sebera 1, Marica Mikuljan 1, Michael Mrissa 1,2, Andreja Kutnar 1,2, Rok Prislan 1,2, Jaka
Gaspar Pečnik 1,2
1. InnoRenew CoE, Livade 6, 6310 Izola, Slovenia, vaclav.sebera@innorenew.eu
2. University of Primorska, Titov trg 4, 6000 Koper, Slovenia
Electric guitar necks (EGNs) are usually made of hardwoods (i.e., maple, ash, etc.), including protected
exotic species coming from overseas (mahogany, etc.), due to their aesthetics, high stiffness and density.
Additionally, EGNs typically include a truss rod – a metal bar stiffening the neck against bending caused
by string tension. In order to reduce the environmental impact of guitar production, we believe that EGNs
can be made from local and fast grown plantation wood modified using a thermo-hydro-mechanical
(THM) process. This approach for EGN production may be (i) more convenient due to higher mechanical
properties of densified wood while preserving similar vibrational performance; (ii) more economical due
to using local and cheap resources and absence of a truss rod; (iii) more environmentally friendly due
to reduced logistics and energy costs. To analyze the hypothesis resulting from (i), we performed both
experimental tests and numerical analyses. Experiments consist of poplar wood densification (dens. ratio
1.5) to obtain the elastic orthotropic material model of densified poplar suitable for finite element analyses
(FEA). We aim to perform compression tests accompanied with digital image correlation, which will
provide a set of elastic material coefficients – 3x normal elastic moduli (EL, ER, ET) and 3x Poisson’s ratios
(μLR, μRT, μLT); shear elastic moduli (GLR, GRT, GLT) were calculated theoretically. Developed material
models were employed in FEA of (i) guitar neck deflection induced by string tension and (ii) modal analysis
of a neck including sensitivity study for the role of density and elastic moduli on eigenfrequencies. FEA
will use the following material scenarios: poplar, densified poplar, and maple. Preliminary results of the
FEA with maple properties are shown in Figure 1. Figure 1a shows how deflection and PS1 changes with
change of EL – deflection decreased 40 % and PS1 increased ~ 11 % as EL increased from 12.4 GPa to 22
GPa. Figure 1b shows the eigenfrequencies decrease with density but increase as EL increases (1st freq
17.4 %, 2nd freq. 21.4 % and 3rd about 27 %).
Keywords: densified poplar, orthotropic material model, finite element analysis, electric guitar, acoustics
Acknowledgement
The authors acknowledge the European Commission for funding the InnoRenew project (grant agreement
739574) under the Horizon2020Widespread-2-Teaming program and the Republic of Slovenia (investment
funding from the Republic of Slovenia and the European Regional Development Fund).
INNORENEW COE INTERNATIONAL CONFERENCE 2021
48
