Dionysios T. G. Katerelos | TEI of Ionian Islands (original) (raw)

Uploads

Papers by Dionysios T. G. Katerelos

Journal of Applied Physics

In this work, a phononic metamaterial that could be a reliable solution for several sound attenua... more In this work, a phononic metamaterial that could be a reliable solution for several sound attenuation applications is examined numerically and experimentally. The proposed structure consists of a spherical shell connected with cylindrical conduits in a simple cubic arrangement. Numerical calculations, using the finite element method, and experimental measurements of the sound transmission loss were performed, providing significant evidence of the applicability of the proposed metamaterial in sound attenuation applications. For the validation of the complete acoustic bandgaps by the structure, the research was expanded to the examination of all high symmetry spatial directions. The results for all the examined spatial directions provided wide acoustic bandgaps, thus validating the evidence of complete acoustic bandgaps by the structure over a wide frequency range of the audio spectrum. Furthermore, the contribution of each part of the structure was separately analyzed, providing the ...

The structural and acoustical characteristics of two Kefalonian traditional wind musical instrume... more The structural and acoustical characteristics of two Kefalonian traditional wind musical instruments are investigated. The first one is a bagpipe called 'skortsámpouno' which is, from a constructional perspective, alike the Greek 'tsampoúna' (alike to gaida). The second one is another wind instrument called 'anakarí', which is alike the well-known 'zournás'. Tensile testing, dynamic mechanical testing (DMA), water absorption experiments and mechanical modeling were carried out for the purposes of this paper. The degradation of the properties of different construction materials was evaluated. Three different materials were used for the construction of parts of the two instruments (wood, plastic, metal), which in turn were subjected to acoustic and structural analysis in order to evaluate the production of (non-) differential sound quality. Acoustical experiments were carried out using BIAS software and studio recording processing of 'skortsámpouno' and 'anakarí', in order to compare the acoustical behavior depending on the construction material. The conducted analysis revealed small divergence of the sound quality in correlation with the different materials used for the construction of the tube. On the contrary, the use of different materials for the construction of the bell resulted in significant divergence in the sound quality of both instruments.

Damage developing within laminated composites during their service life is a result of complex co... more Damage developing within laminated composites during their service life is a result of complex combinations of thermo-mechanical and environmental loads. Since the transverse strain to failure of unidirectional plies is lower than other strength components, intralaminar (transverse) cracking in layers of laminates, caused by combined action of transverse tensile

Musical instruments consist a significant part of the global cultural heritage. Everywhere in the... more Musical instruments consist a significant part of the global cultural heritage. Everywhere in the world such important artefacts can be traced and preserved for future generations as an important part of human heritage. A century old acoustical guitar was found in the Kefalonia Island, Greece, that was survived from time wear and earthquakes attacks. In this paper the procedure followed for the restoration of this guitar is presented. Old musical instruments, even the restored ones, should be treated carefully and stored appropriately, in order to be protected. Thus, the idea is to construct exact possible copies that could present publically their performance that is the sound they produce. Such a copy was designed and constructed for the above mentioned guitar and the two instruments were evaluated for their mechanical and acoustical characteristics.

Plastics Rubber and Composites

The design and construction is described of a vehicle bridge made of glass-reinforced polyester p... more The design and construction is described of a vehicle bridge made of glass-reinforced polyester pultruded box beams. The bridge has a simply supported span 11·6 m long and 4 m wide. It has been designed as a Class 30 (300 kN load capacity) according to DIN 1072 and represents a single traffic lane. The composite bridge consists of a 3-D truss structure made of thick-wall fibre-reinforced plastic longitudinal box elements of hollow square cross-section. The bridge design proposed allows for fast construction as it consists of pre-fabricated, ready to assemble elements. The total of the composite bridge does not exceed 135 kN.

Stress state in the vicinity of transverse crack tip is investigated using an analytical variatio... more Stress state in the vicinity of transverse crack tip is investigated using an analytical variational model based on principle of minimum complementary energy. Knowing the stress concentration factor’s (SCF) values at the tip of the crack, the possibility of new damage modes initiation is examined. SCF is recalculated taking into account the possible local stiffness reduction due to new modes of damage.

Three analytical models with increasing complexity, all based on minimization of complementary en... more Three analytical models with increasing complexity, all based on minimization of complementary energy, are compared in their ability to predict shear modulus reduction of laminates with intralaminar cracks in 90-layer. The very elegant and simple (and the less accurate) model by Hashin assumes linear out-of-plane shear stress distribution across the ply in all layers. The second model assumes exponential shape of these stresses in the constraint layer keeping linear assumption in the cracked layer. The model developed in the present paper accounts for nonlinear out-of-plane shear stress thickness distribution in all layers described by shape functions determined in the procedure of minimization. Increasing the complexity of the model the predicted shear modulus of the damaged laminate increases approaching to value obtained using finite elements (FE). Results show that for laminates with relatively thick cracked layers the stress state description in the cracked layer should be refi...

International Journal of Damage Mechanics, 2012

Proceedings of the 6th National Conference "Acoustics 2012"

The use of reflectors for the optimal sound diffusion is a major issue in Room Acoustics. Up to n... more The use of reflectors for the optimal sound diffusion is a major issue in Room Acoustics. Up to now, the applied reflectors are stable, with certain shape and made by conventional materials. In the present is studied the possibility to replace the conventional reflectors by new, manufactured by composite materials. The aim is to design flexible “intelligent” reflectors that will adapt their shape depending on the certain acoustical needs of a room. This change is planned to be actuated using embedded shape memory alloy (SMA) wires. The adaptation process will be controlled automatically by an electronic system. In order to control damage initiation and growth within the composite panel, an optical fibres network will be applied.

Proceedings of the 134th Audio Engineering Society Convention

Modern audio mastering procedures include selectively equalisation of specific frequency bands fo... more Modern audio mastering procedures include selectively equalisation of specific frequency bands for the tonal enhancement of the unmastered material. This process is mostly based on music scores' or listening information, like the musical key or the mode of the audio material. Based on these, mastering engineers apply enhancement or attenuation at specific frequency bands, relative to the frequencies that correspond to the musical's key notes. In this work, we present an adaptive and automated equalisation system for the aforementioned mastering procedure based on a novel method for fundamental frequency estimation. Moreover, PEAQ analysis and listening tests were implemented to evaluate the system's performance.

Journal of Applied Physics

In this work, a phononic metamaterial that could be a reliable solution for several sound attenua... more In this work, a phononic metamaterial that could be a reliable solution for several sound attenuation applications is examined numerically and experimentally. The proposed structure consists of a spherical shell connected with cylindrical conduits in a simple cubic arrangement. Numerical calculations, using the finite element method, and experimental measurements of the sound transmission loss were performed, providing significant evidence of the applicability of the proposed metamaterial in sound attenuation applications. For the validation of the complete acoustic bandgaps by the structure, the research was expanded to the examination of all high symmetry spatial directions. The results for all the examined spatial directions provided wide acoustic bandgaps, thus validating the evidence of complete acoustic bandgaps by the structure over a wide frequency range of the audio spectrum. Furthermore, the contribution of each part of the structure was separately analyzed, providing the ...

The structural and acoustical characteristics of two Kefalonian traditional wind musical instrume... more The structural and acoustical characteristics of two Kefalonian traditional wind musical instruments are investigated. The first one is a bagpipe called 'skortsámpouno' which is, from a constructional perspective, alike the Greek 'tsampoúna' (alike to gaida). The second one is another wind instrument called 'anakarí', which is alike the well-known 'zournás'. Tensile testing, dynamic mechanical testing (DMA), water absorption experiments and mechanical modeling were carried out for the purposes of this paper. The degradation of the properties of different construction materials was evaluated. Three different materials were used for the construction of parts of the two instruments (wood, plastic, metal), which in turn were subjected to acoustic and structural analysis in order to evaluate the production of (non-) differential sound quality. Acoustical experiments were carried out using BIAS software and studio recording processing of 'skortsámpouno' and 'anakarí', in order to compare the acoustical behavior depending on the construction material. The conducted analysis revealed small divergence of the sound quality in correlation with the different materials used for the construction of the tube. On the contrary, the use of different materials for the construction of the bell resulted in significant divergence in the sound quality of both instruments.

Damage developing within laminated composites during their service life is a result of complex co... more Damage developing within laminated composites during their service life is a result of complex combinations of thermo-mechanical and environmental loads. Since the transverse strain to failure of unidirectional plies is lower than other strength components, intralaminar (transverse) cracking in layers of laminates, caused by combined action of transverse tensile

Musical instruments consist a significant part of the global cultural heritage. Everywhere in the... more Musical instruments consist a significant part of the global cultural heritage. Everywhere in the world such important artefacts can be traced and preserved for future generations as an important part of human heritage. A century old acoustical guitar was found in the Kefalonia Island, Greece, that was survived from time wear and earthquakes attacks. In this paper the procedure followed for the restoration of this guitar is presented. Old musical instruments, even the restored ones, should be treated carefully and stored appropriately, in order to be protected. Thus, the idea is to construct exact possible copies that could present publically their performance that is the sound they produce. Such a copy was designed and constructed for the above mentioned guitar and the two instruments were evaluated for their mechanical and acoustical characteristics.

Plastics Rubber and Composites

The design and construction is described of a vehicle bridge made of glass-reinforced polyester p... more The design and construction is described of a vehicle bridge made of glass-reinforced polyester pultruded box beams. The bridge has a simply supported span 11·6 m long and 4 m wide. It has been designed as a Class 30 (300 kN load capacity) according to DIN 1072 and represents a single traffic lane. The composite bridge consists of a 3-D truss structure made of thick-wall fibre-reinforced plastic longitudinal box elements of hollow square cross-section. The bridge design proposed allows for fast construction as it consists of pre-fabricated, ready to assemble elements. The total of the composite bridge does not exceed 135 kN.

Stress state in the vicinity of transverse crack tip is investigated using an analytical variatio... more Stress state in the vicinity of transverse crack tip is investigated using an analytical variational model based on principle of minimum complementary energy. Knowing the stress concentration factor’s (SCF) values at the tip of the crack, the possibility of new damage modes initiation is examined. SCF is recalculated taking into account the possible local stiffness reduction due to new modes of damage.

Three analytical models with increasing complexity, all based on minimization of complementary en... more Three analytical models with increasing complexity, all based on minimization of complementary energy, are compared in their ability to predict shear modulus reduction of laminates with intralaminar cracks in 90-layer. The very elegant and simple (and the less accurate) model by Hashin assumes linear out-of-plane shear stress distribution across the ply in all layers. The second model assumes exponential shape of these stresses in the constraint layer keeping linear assumption in the cracked layer. The model developed in the present paper accounts for nonlinear out-of-plane shear stress thickness distribution in all layers described by shape functions determined in the procedure of minimization. Increasing the complexity of the model the predicted shear modulus of the damaged laminate increases approaching to value obtained using finite elements (FE). Results show that for laminates with relatively thick cracked layers the stress state description in the cracked layer should be refi...

International Journal of Damage Mechanics, 2012

Proceedings of the 6th National Conference "Acoustics 2012"

The use of reflectors for the optimal sound diffusion is a major issue in Room Acoustics. Up to n... more The use of reflectors for the optimal sound diffusion is a major issue in Room Acoustics. Up to now, the applied reflectors are stable, with certain shape and made by conventional materials. In the present is studied the possibility to replace the conventional reflectors by new, manufactured by composite materials. The aim is to design flexible “intelligent” reflectors that will adapt their shape depending on the certain acoustical needs of a room. This change is planned to be actuated using embedded shape memory alloy (SMA) wires. The adaptation process will be controlled automatically by an electronic system. In order to control damage initiation and growth within the composite panel, an optical fibres network will be applied.

Proceedings of the 134th Audio Engineering Society Convention

Modern audio mastering procedures include selectively equalisation of specific frequency bands fo... more Modern audio mastering procedures include selectively equalisation of specific frequency bands for the tonal enhancement of the unmastered material. This process is mostly based on music scores' or listening information, like the musical key or the mode of the audio material. Based on these, mastering engineers apply enhancement or attenuation at specific frequency bands, relative to the frequencies that correspond to the musical's key notes. In this work, we present an adaptive and automated equalisation system for the aforementioned mastering procedure based on a novel method for fundamental frequency estimation. Moreover, PEAQ analysis and listening tests were implemented to evaluate the system's performance.