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EXPERIMENTAL CHARACTERIZATION AND COMPUTATIONAL DYNAMIC MODELLING OF A VIOLIN Analysing the effects of creep and string tension

Värelä, Joel LU and Tunlid, Erik LU (2020) In TVSM-5000 VSMM01 20201
Structural Mechanics
Department of Construction Sciences
Abstract
During the 17th and early 18th century Antonio Stradivari built around 900 violins, that still
today are considered some of the best instruments ever created. The theories of how it was
possible for a luthier active 300 years ago to create instruments of this quality are many,
including unique wood properties and secret building techniques.
The sound of a violin is produced by vibrations from the strings that are transmitted to the top
plate and bottom plate through the bridge. The plates and the air in the cavity reverberate
within the hollow body, producing the tone characteristic of the violin. Dynamic properties
are therefore directly connected to the quality of the instrument.
A top and back plate was provided by luthier... (More)
During the 17th and early 18th century Antonio Stradivari built around 900 violins, that still
today are considered some of the best instruments ever created. The theories of how it was
possible for a luthier active 300 years ago to create instruments of this quality are many,
including unique wood properties and secret building techniques.
The sound of a violin is produced by vibrations from the strings that are transmitted to the top
plate and bottom plate through the bridge. The plates and the air in the cavity reverberate
within the hollow body, producing the tone characteristic of the violin. Dynamic properties
are therefore directly connected to the quality of the instrument.
A top and back plate was provided by luthier Robert Zuger. Experimental modal analysis
(EMA) was carried out on the plates using the roving excitation technique to determine their
modal parameters. Based on the geometries of the plates FE-models of the plates were
created. By studying the results of the EMA, material parameters of the plates could be
determined in such a way that the modal contents of the FE-plates matched those of the real
plates. The natural frequencies for the first 5 modes, extracted from the FE-model, matched
those of the real plates within 7 % and the same mode shapes were prevalent in both the FEanalysis
and the EMA.
Based on violin drawings and input from Robert Zuger a FE-model of a complete violin was
created which was tuned by tensioning the strings. The model uses non-linear geometry to
handle the effects of string tension. A time-hardening creep model is implemented which can
be used to study the aging process of violins.
The steady-state response to excitations of the strings were preformed to determine the
response of the violin up to 1000 Hz. The mean displacements of the plates were calculated to
indicate at which frequencies volume changes of the violin cavity occurred. Each string
excitation revealed frequency spans in which the volume change appeared particularly large. (Less)
Please use this url to cite or link to this publication:
author
Värelä, Joel LU and Tunlid, Erik LU
supervisor
organization
course
VSMM01 20201
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Violin, experimental modal analysis, modal analysis, EMA, finite element method, FEM, FE, wood
publication/series
TVSM-5000
report number
TVSM-5247
ISSN
0281-6679
language
English
id
9024959
alternative location
http://www.byggmek.lth.se/fileadmin/byggnadsmekanik/publications/tvsm5000/web5247.pdf
date added to LUP
2020-08-06 15:33:39
date last changed
2020-08-06 15:33:39
@misc{9024959,
  abstract     = {During the 17th and early 18th century Antonio Stradivari built around 900 violins, that still
today are considered some of the best instruments ever created. The theories of how it was
possible for a luthier active 300 years ago to create instruments of this quality are many,
including unique wood properties and secret building techniques.
The sound of a violin is produced by vibrations from the strings that are transmitted to the top
plate and bottom plate through the bridge. The plates and the air in the cavity reverberate
within the hollow body, producing the tone characteristic of the violin. Dynamic properties
are therefore directly connected to the quality of the instrument.
A top and back plate was provided by luthier Robert Zuger. Experimental modal analysis
(EMA) was carried out on the plates using the roving excitation technique to determine their
modal parameters. Based on the geometries of the plates FE-models of the plates were
created. By studying the results of the EMA, material parameters of the plates could be
determined in such a way that the modal contents of the FE-plates matched those of the real
plates. The natural frequencies for the first 5 modes, extracted from the FE-model, matched
those of the real plates within 7 % and the same mode shapes were prevalent in both the FEanalysis
and the EMA.
Based on violin drawings and input from Robert Zuger a FE-model of a complete violin was
created which was tuned by tensioning the strings. The model uses non-linear geometry to
handle the effects of string tension. A time-hardening creep model is implemented which can
be used to study the aging process of violins.
The steady-state response to excitations of the strings were preformed to determine the
response of the violin up to 1000 Hz. The mean displacements of the plates were calculated to
indicate at which frequencies volume changes of the violin cavity occurred. Each string
excitation revealed frequency spans in which the volume change appeared particularly large.},
  author       = {Värelä, Joel and Tunlid, Erik},
  issn         = {0281-6679},
  keyword      = {Violin,experimental modal analysis,modal analysis,EMA,finite element method,FEM,FE,wood},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM-5000},
  title        = {EXPERIMENTAL CHARACTERIZATION AND COMPUTATIONAL DYNAMIC MODELLING OF A VIOLIN Analysing the effects of creep and string tension},
  year         = {2020},
}