Please visit my Google Scholar page for more recent results.
8.
Osman Sayginer; Erica Iacob; Stefano Varas; Anna Szczurek; Maurizio Ferrari; Anna Lukowiak; Giancarlo C Righini; Oreste S Bursi; Alessandro Chiasera
Design, fabrication and assessment of an optomechanical sensor for pressure and vibration detection using flexible glass multilayers Journal Article
In: Optical Materials, vol. 115, pp. 111023, 2021, ISSN: 0925-3467.
Abstract | Links | BibTeX | Tags: Journal Article, Scopus Indexed
@article{SAYGINER2021111023,
title = {Design, fabrication and assessment of an optomechanical sensor for pressure and vibration detection using flexible glass multilayers},
author = {Osman Sayginer and Erica Iacob and Stefano Varas and Anna Szczurek and Maurizio Ferrari and Anna Lukowiak and Giancarlo C Righini and Oreste S Bursi and Alessandro Chiasera},
url = {https://www.sciencedirect.com/science/article/pii/S092534672100224X},
doi = {https://doi.org/10.1016/j.optmat.2021.111023},
issn = {0925-3467},
year = {2021},
date = {2021-01-01},
journal = {Optical Materials},
volume = {115},
pages = {111023},
abstract = {We introduce an easily implementable optomechanical device for pressure and vibration sensing using a multilayer structure on a flexible substrate. We present the design, fabrication and evaluation steps for a proof-of-concept device as well as optical glass components. The design steps include optical, mechanical, and optomechanical correlation simulations using the transfer matrix method, finite element analysis, geometric optics and analytical calculations. The fabrication part focuses on the deposition of multilayers on polymeric flexible substrates using the radio frequency sputtering technique. To investigate the quality of the glass coatings on polymeric substrates, atomic force microscopy and optical microscopy are also performed. Optical measurements reveal that, even after bending, there are no differences between multilayer samples deposited on the polymeric and SiO2 substrates. The performance assessment of the proof-of-concept device shows that the sensor resonance frequency is around 515 Hz and the sensor static response is capable of sensing from 50 Pa to 235 Pa.},
keywords = {Journal Article, Scopus Indexed},
pubstate = {published},
tppubtype = {article}
}
We introduce an easily implementable optomechanical device for pressure and vibration sensing using a multilayer structure on a flexible substrate. We present the design, fabrication and evaluation steps for a proof-of-concept device as well as optical glass components. The design steps include optical, mechanical, and optomechanical correlation simulations using the transfer matrix method, finite element analysis, geometric optics and analytical calculations. The fabrication part focuses on the deposition of multilayers on polymeric flexible substrates using the radio frequency sputtering technique. To investigate the quality of the glass coatings on polymeric substrates, atomic force microscopy and optical microscopy are also performed. Optical measurements reveal that, even after bending, there are no differences between multilayer samples deposited on the polymeric and SiO2 substrates. The performance assessment of the proof-of-concept device shows that the sensor resonance frequency is around 515 Hz and the sensor static response is capable of sensing from 50 Pa to 235 Pa.
7.
Hao Chen; Alessandro Chiasera; Stefano Varas; Osman Sayginer; Cristina Armellini; Giorgio Speranza; Raffaella Suriano; Maurizio Ferrari; Silvia Maria Pietralunga
Tungsten oxide films by radio-frequency magnetron sputtering for near-infrared photonics Journal Article
In: Optical Materials: X, vol. 12, pp. 100093, 2021, ISSN: 2590-1478.
Abstract | Links | BibTeX | Tags: Journal Article, Scopus Indexed
@article{CHEN2021100093,
title = {Tungsten oxide films by radio-frequency magnetron sputtering for near-infrared photonics},
author = {Hao Chen and Alessandro Chiasera and Stefano Varas and Osman Sayginer and Cristina Armellini and Giorgio Speranza and Raffaella Suriano and Maurizio Ferrari and Silvia Maria Pietralunga},
url = {https://www.sciencedirect.com/science/article/pii/S2590147821000231},
doi = {https://doi.org/10.1016/j.omx.2021.100093},
issn = {2590-1478},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Optical Materials: X},
volume = {12},
pages = {100093},
abstract = {Tungsten oxide WO3-x is a transition metal oxide and a wide bandgap semiconductor, with a wide range of possible optical and photonic applications. In dependence on the fabrication techniques different stoichiometric ratios (x) and crystalline phases are obtained, which end up with an overall polymorph and extremely versatile material, characterized by tailorable dielectric properties. In particular, WO3-x thin film deposition by Radio-Frequency (RF) sputtering techniques provides a precise control of thickness, composition and nanostructure. In this work we introduce and discuss a specific process of deposition, that is magnetron RF-sputtering as a suitable way to grow WO3-x thin films with selected properties. Possibility of integrating WO3-x thin film on to one-dimensional (1D) photonic crystal structures is also explored. Films are transparent in the near and short-wavelength infrared optical spectral range. Their quality is assessed by morphological, structural and compositional characterizations. Dielectric properties are characterized by optical spectroscopy and ellipsometry, the latter also evaluates the degree of optical anisotropy of thin films in their crystalline phase. An 1D photonics bandgap structure is designed, formed by a SiO2–TiO2 multilayer and capped with a 450 nm-thick transparent WO3-x film, so that surface confinement and local enhancement of the optical field at 1416 nm in the topmost WO3-x layer is obtained.},
keywords = {Journal Article, Scopus Indexed},
pubstate = {published},
tppubtype = {article}
}
Tungsten oxide WO3-x is a transition metal oxide and a wide bandgap semiconductor, with a wide range of possible optical and photonic applications. In dependence on the fabrication techniques different stoichiometric ratios (x) and crystalline phases are obtained, which end up with an overall polymorph and extremely versatile material, characterized by tailorable dielectric properties. In particular, WO3-x thin film deposition by Radio-Frequency (RF) sputtering techniques provides a precise control of thickness, composition and nanostructure. In this work we introduce and discuss a specific process of deposition, that is magnetron RF-sputtering as a suitable way to grow WO3-x thin films with selected properties. Possibility of integrating WO3-x thin film on to one-dimensional (1D) photonic crystal structures is also explored. Films are transparent in the near and short-wavelength infrared optical spectral range. Their quality is assessed by morphological, structural and compositional characterizations. Dielectric properties are characterized by optical spectroscopy and ellipsometry, the latter also evaluates the degree of optical anisotropy of thin films in their crystalline phase. An 1D photonics bandgap structure is designed, formed by a SiO2–TiO2 multilayer and capped with a 450 nm-thick transparent WO3-x film, so that surface confinement and local enhancement of the optical field at 1416 nm in the topmost WO3-x layer is obtained.
6.
Osman Sayginer; Rocco di Filippo; Aurelien Lecoq; Alessandra Marino; Oreste S Bursi
Seismic Vulnerability Analysis of a Coupled Tank-Piping System by Means of Hybrid Simulation and Acoustic Emission Journal Article
In: Experimental Techniques, 2020, ISSN: 1747-1567.
Abstract | Links | BibTeX | Tags: Journal Article, Scopus Indexed
@article{Sayginer2020c,
title = {Seismic Vulnerability Analysis of a Coupled Tank-Piping System by Means of Hybrid Simulation and Acoustic Emission},
author = {Osman Sayginer and Rocco di Filippo and Aurelien Lecoq and Alessandra Marino and Oreste S Bursi },
url = {https://doi.org/10.1007/s40799-020-00396-3},
doi = {10.1007/s40799-020-00396-3},
issn = {1747-1567},
year = {2020},
date = {2020-09-01},
journal = {Experimental Techniques},
abstract = {In order to shed light on the seismic response of complex industrial plants, advanced finite element models should take into account both multicomponents and relevant coupling effects. These models are usually computationally expensive and rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, which requires a solid background of experimental data. Vulnerability and reliability analyses both depend on the adoption of a significant number of seismic waveforms that are generally not available when seismic risk evaluation is strictly site-specific. In addition, detection of most vulnerable components, i.e., pipe bends and welding points, is an important step to prevent leakage events. In order to handle these issues, a methodology based on a stochastic seismic ground motion model, hybrid simulation and acoustic emission is presented in this paper. The seismic model is able to generate synthetic ground motions coherent with site-specific analysis. In greater detail, the system is composed of a steel slender tank, i.e., the numerical substructure, and a piping network connected through a bolted flange joint, i.e., the physical substructure. Moreover, to monitor the seismic performance of the pipeline and harness the use of sensor technology, acoustic emission sensors are placed through the pipeline. Thus, real-time acoustic emission signals of the system under study are acquired using acoustic emission sensors. Moreover, in addition to seismic events, also a severe monotonic loading is exerted on the physical substructure. As a result, deformation levels of each critical component were investigated; and the processing of acoustic emission signals provided a more in-depth view of the damage of the analysed components.},
keywords = {Journal Article, Scopus Indexed},
pubstate = {published},
tppubtype = {article}
}
In order to shed light on the seismic response of complex industrial plants, advanced finite element models should take into account both multicomponents and relevant coupling effects. These models are usually computationally expensive and rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, which requires a solid background of experimental data. Vulnerability and reliability analyses both depend on the adoption of a significant number of seismic waveforms that are generally not available when seismic risk evaluation is strictly site-specific. In addition, detection of most vulnerable components, i.e., pipe bends and welding points, is an important step to prevent leakage events. In order to handle these issues, a methodology based on a stochastic seismic ground motion model, hybrid simulation and acoustic emission is presented in this paper. The seismic model is able to generate synthetic ground motions coherent with site-specific analysis. In greater detail, the system is composed of a steel slender tank, i.e., the numerical substructure, and a piping network connected through a bolted flange joint, i.e., the physical substructure. Moreover, to monitor the seismic performance of the pipeline and harness the use of sensor technology, acoustic emission sensors are placed through the pipeline. Thus, real-time acoustic emission signals of the system under study are acquired using acoustic emission sensors. Moreover, in addition to seismic events, also a severe monotonic loading is exerted on the physical substructure. As a result, deformation levels of each critical component were investigated; and the processing of acoustic emission signals provided a more in-depth view of the damage of the analysed components.
5.
Alessandro Chiasera; Osman Sayginer; Erica Iacob; Anna Szczurek; Stefano Varas; Justyna Krzak; Oreste S Bursi; Daniele Zonta; Anna Lukowiak; Giancarlo C Righini; Maurizio Ferrari
International Society for Optics and Photonics SPIE, vol. 11357, 2020.
Abstract | Links | BibTeX | Tags: Conference, Proceeding, Scopus Indexed
@proceedings{Chiasera2020b,
title = {Flexible photonics: RF-sputtering fabrication of glass-based systems operating under mechanical deformation conditions},
author = {Alessandro Chiasera and Osman Sayginer and Erica Iacob and Anna Szczurek and Stefano Varas and Justyna Krzak and Oreste S Bursi and Daniele Zonta and Anna Lukowiak and Giancarlo C Righini and Maurizio Ferrari},
doi = {10.1117/12.2551472},
year = {2020},
date = {2020-01-01},
booktitle = {Fiber Lasers and Glass Photonics: Materials through Applications II},
volume = {11357},
pages = {1 -- 11},
publisher = {SPIE},
organization = {International Society for Optics and Photonics},
abstract = {We present the radio frequency sputtering fabrication protocols for the fabrication on flexible polymeric substrates of glass-based 1D photonic crystals and erbium activated planar waveguides. Various characterization techniques, such as atomic force microscopy and optical microscopy, are employed to put in evidence the good adhesion of the glass coating on the polymeric substrates. Transmittance measurements are performed on the multilayer structure and indicate that there are no differences between the samples deposited on the polymeric and SiO_{2} substrates, even after bending. Prism coupling technique is used to measure the optical parameter of the planar waveguide fabricated on flexible substrates. The ^{4}I_{13/2} → ^{4}I_{15/2} emission band, detected upon TE_{0} mode excitation at 514.5 nm, exhibits the spectral shape characteristic of Er^{3+} ions embedded in a crystalline environment.},
keywords = {Conference, Proceeding, Scopus Indexed},
pubstate = {published},
tppubtype = {proceedings}
}
We present the radio frequency sputtering fabrication protocols for the fabrication on flexible polymeric substrates of glass-based 1D photonic crystals and erbium activated planar waveguides. Various characterization techniques, such as atomic force microscopy and optical microscopy, are employed to put in evidence the good adhesion of the glass coating on the polymeric substrates. Transmittance measurements are performed on the multilayer structure and indicate that there are no differences between the samples deposited on the polymeric and SiO2 substrates, even after bending. Prism coupling technique is used to measure the optical parameter of the planar waveguide fabricated on flexible substrates. The 4I13/2 → 4I15/2 emission band, detected upon TE0 mode excitation at 514.5 nm, exhibits the spectral shape characteristic of Er3+ ions embedded in a crystalline environment.
4.
Osman Sayginer; Alessandro Chiasera; Stefano Varas; Anna Lukowiak; Maurizio Ferrari; Oreste S Bursi
Design and fabrication of multilayer-driven optomechanical device for force and vibration sensing Proceedings
International Society for Optics and Photonics SPIE, vol. 11357, 2020.
Abstract | Links | BibTeX | Tags: Conference, Proceeding, Scopus Indexed
@proceedings{Sayginer2020a,
title = {Design and fabrication of multilayer-driven optomechanical device for force and vibration sensing},
author = {Osman Sayginer and Alessandro Chiasera and Stefano Varas and Anna Lukowiak and Maurizio Ferrari and Oreste S Bursi},
doi = {10.1117/12.2555347},
year = {2020},
date = {2020-01-01},
booktitle = {Fiber Lasers and Glass Photonics: Materials through Applications II},
volume = {11357},
pages = {255 -- 264},
publisher = {SPIE},
organization = {International Society for Optics and Photonics},
abstract = {Multilayer structures are commonly used components in optics and photonics due to their unique properties to manipulate the spectral response of light. Multilayer-driven components for sensing purposes can bring some advantages such as high sensitivity, fast signal response, electromagnetic interference immunity, and low power consumption. Thus, a mechanically coupled optical system can be the right candidate for force and vibration detection. In this work, we propose and demonstrate an optomechanical sensing system for pressure and vibration detection using two multilayer structures, a circular membrane, a light source, and a photodiode. The design of this proposed system consists of two parts, which are optical design and mechanical design. In the optical design, we modeled the optical response of the multilayer structures in the visible spectra using the Transfer Matrix Method. The mechanical response, on the other hand, is calculated using finite element simulations via the COMSOL Multiphysics software. The multilayer structures are fabricated by RF-Sputtering technique and then integrated through a 3D printed mechanical housing. The sensor characteristics (sensitivity and resonance frequency) are experimentally investigated by a static loading test and a transient response analysis. Results are shown that the sensor frequency around 510 Hz and the sensitivity of the sensor about 50 Pa.},
keywords = {Conference, Proceeding, Scopus Indexed},
pubstate = {published},
tppubtype = {proceedings}
}
Multilayer structures are commonly used components in optics and photonics due to their unique properties to manipulate the spectral response of light. Multilayer-driven components for sensing purposes can bring some advantages such as high sensitivity, fast signal response, electromagnetic interference immunity, and low power consumption. Thus, a mechanically coupled optical system can be the right candidate for force and vibration detection. In this work, we propose and demonstrate an optomechanical sensing system for pressure and vibration detection using two multilayer structures, a circular membrane, a light source, and a photodiode. The design of this proposed system consists of two parts, which are optical design and mechanical design. In the optical design, we modeled the optical response of the multilayer structures in the visible spectra using the Transfer Matrix Method. The mechanical response, on the other hand, is calculated using finite element simulations via the COMSOL Multiphysics software. The multilayer structures are fabricated by RF-Sputtering technique and then integrated through a 3D printed mechanical housing. The sensor characteristics (sensitivity and resonance frequency) are experimentally investigated by a static loading test and a transient response analysis. Results are shown that the sensor frequency around 510 Hz and the sensitivity of the sensor about 50 Pa.
3.
Osman Sayginer; Alessandro Chiasera; Lidia Zur; Stefano Varas; Lam Thi Ngoc Tran; Cristina Armellini; Maurizio Ferrari; Oreste S Bursi
Fabrication, modelling and assessment of hybrid 1-D elastic Fabry Perot microcavity for mechanical sensing applications Journal Article
In: Ceramics International, vol. 45, no. 6, pp. 7785–7788, 2019, ISSN: 0272-8842.
Abstract | Links | BibTeX | Tags: Journal Article, Scopus Indexed
@article{Sayginer2019b,
title = {Fabrication, modelling and assessment of hybrid 1-D elastic Fabry Perot microcavity for mechanical sensing applications},
author = {Osman Sayginer and Alessandro Chiasera and Lidia Zur and Stefano Varas and Lam Thi Ngoc Tran and Cristina Armellini and Maurizio Ferrari and Oreste S Bursi},
doi = {10.1016/j.ceramint.2019.01.083},
issn = {0272-8842},
year = {2019},
date = {2019-04-15},
journal = {Ceramics International},
volume = {45},
number = {6},
pages = {7785--7788},
publisher = {Elsevier},
abstract = {1-D multilayer dielectric films consisting of seven pairs of SiO2 and TiO2 alternating layers are deposited on a SiO2 substrate using the radio frequency sputtering technique. The thicknesses of the film layers are chosen to reflect the visible radiation around 650 nm. An elastic microcavity layer made of Polydimethylsiloxane was sandwiched between two Bragg reflectors. A fabrication process was then developed for elastic microcavity in order to tailor the thickness, establish the surface planarity and to increase reproducibility of the samples. Optical transmittance of the single Bragg reflector and the microcavity were both simulated and measured. A comparison between measurement data and Transfer Matrix Method calculations shows a favourable correlation. Furthermore, in order to assess the suitability of the microcavity as a force sensor, transmittance measurements were carried out as a function of the applied forces. The change in the elastic microcavity thickness due to applied forces resulted in cavity resonance peak shifts proportional to the applied forces.},
keywords = {Journal Article, Scopus Indexed},
pubstate = {published},
tppubtype = {article}
}
1-D multilayer dielectric films consisting of seven pairs of SiO2 and TiO2 alternating layers are deposited on a SiO2 substrate using the radio frequency sputtering technique. The thicknesses of the film layers are chosen to reflect the visible radiation around 650 nm. An elastic microcavity layer made of Polydimethylsiloxane was sandwiched between two Bragg reflectors. A fabrication process was then developed for elastic microcavity in order to tailor the thickness, establish the surface planarity and to increase reproducibility of the samples. Optical transmittance of the single Bragg reflector and the microcavity were both simulated and measured. A comparison between measurement data and Transfer Matrix Method calculations shows a favourable correlation. Furthermore, in order to assess the suitability of the microcavity as a force sensor, transmittance measurements were carried out as a function of the applied forces. The change in the elastic microcavity thickness due to applied forces resulted in cavity resonance peak shifts proportional to the applied forces.
2.
Rocco di Filippo; Giuseppe Abbiati; Osman Sayginer; Patrick Covi; Oreste S Bursi; Fabrizio Paolacci
vol. Volume 8: Seismic Engineering, 2019, (V008T08A029).
Abstract | Links | BibTeX | Tags: Conference, Proceeding, Scopus Indexed
@proceedings{10.1115/PVP2019-93685,
title = {Numerical Surrogate Model of a Coupled Tank-Piping System for Seismic Fragility Analysis With Synthetic Ground Motions},
author = {Rocco di Filippo and Giuseppe Abbiati and Osman Sayginer and Patrick Covi and Oreste S Bursi and Fabrizio Paolacci},
doi = {10.1115/PVP2019-93685},
year = {2019},
date = {2019-01-01},
volume = {Volume 8: Seismic Engineering},
series = {Pressure Vessels and Piping Conference},
abstract = {Seismic risk evaluation of coupled systems of industrial plants often needs the implementation of complex finite element models to consider their multicomponent nature. These models typically rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, thus requiring a solid background of experimental data. Furthermore, fragility analyses depend on the adoption of a significant number of seismic waveforms generally not available when the analysis is site-specific. To propose a methodology able to manage these issues, we present a possible approach for a seismic reliability analysis of a coupled tank-piping system. The novelty of this approach lies in the adoption of artificial accelerograms, FE models and experimental hybrid simulations to evaluate a surrogate meta-model of our system. First, to obtain the necessary input for a stochastic ground motion model able to generate synthetic ground motions, a disaggregation analysis of the seismic hazard is performed. Hereafter, we reduce the space of parameters of the stochastic ground motion model by means of a global sensitivity analysis upon the seismic response of our system. Hence, we generate a large set of synthetic ground motions and select, among them, a few signals for experimental hybrid simulations. In detail, the hybrid simulator is composed by a numerical substructure to predict the sliding response of a steel tank, and a physical substructure made of a realistic piping network. Furthermore, we use these experimental results to calibrate a refined ANSYS FEM. More precisely, we focus on tensile hoop strains in elbow pipes as a leading cause for leakage, monitoring them with strain gauges. Thus, we present the procedure to evaluate a numerical Kriging meta-model of the coupled system based on both experimental and finite element model results. This model will be adopted in a future development to carry out a seismic fragility analysis.},
note = {V008T08A029},
keywords = {Conference, Proceeding, Scopus Indexed},
pubstate = {published},
tppubtype = {proceedings}
}
Seismic risk evaluation of coupled systems of industrial plants often needs the implementation of complex finite element models to consider their multicomponent nature. These models typically rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, thus requiring a solid background of experimental data. Furthermore, fragility analyses depend on the adoption of a significant number of seismic waveforms generally not available when the analysis is site-specific. To propose a methodology able to manage these issues, we present a possible approach for a seismic reliability analysis of a coupled tank-piping system. The novelty of this approach lies in the adoption of artificial accelerograms, FE models and experimental hybrid simulations to evaluate a surrogate meta-model of our system. First, to obtain the necessary input for a stochastic ground motion model able to generate synthetic ground motions, a disaggregation analysis of the seismic hazard is performed. Hereafter, we reduce the space of parameters of the stochastic ground motion model by means of a global sensitivity analysis upon the seismic response of our system. Hence, we generate a large set of synthetic ground motions and select, among them, a few signals for experimental hybrid simulations. In detail, the hybrid simulator is composed by a numerical substructure to predict the sliding response of a steel tank, and a physical substructure made of a realistic piping network. Furthermore, we use these experimental results to calibrate a refined ANSYS FEM. More precisely, we focus on tensile hoop strains in elbow pipes as a leading cause for leakage, monitoring them with strain gauges. Thus, we present the procedure to evaluate a numerical Kriging meta-model of the coupled system based on both experimental and finite element model results. This model will be adopted in a future development to carry out a seismic fragility analysis.
1.
N Moharrami; DJ Langton; O Sayginer; SJ Bull
Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study? Journal Article
In: Thin Solid Films, vol. 549, pp. 79–86, 2013, ISSN: 0040-6090.
Abstract | Links | BibTeX | Tags: Journal Article, Scopus Indexed
@article{moharrami2013does,
title = {Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study?},
author = {N Moharrami and DJ Langton and O Sayginer and SJ Bull},
doi = {10.1016/j.tsf.2013.06.020},
issn = {0040-6090},
year = {2013},
date = {2013-01-01},
journal = {Thin Solid Films},
volume = {549},
pages = {79--86},
publisher = {Elsevier},
abstract = {Titanium-based and cobalt-chrome alloys have been widely used in orthopaedic applications as these materials can significantly enhance the quality of human life as implant materials. The longevity of these materials is highly influenced by their mechanical properties. In some devices cobalt chrome components articulate with titanium alloy counter faces (e.g. in the taper connections of stems and femoral heads in modern modular designs) and damage has been reported of the harder cobalt chrome by the softer titanium alloy component. This study attempts to understand why this might occur by investigating bulk and surface mechanical properties (such as hardness and Young's modulus) of a number of hip implants and test samples using a Hysitron Triboindenter. AFM images were also obtained to determine the contact area and hence, pile-up correction factors.
The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.},
keywords = {Journal Article, Scopus Indexed},
pubstate = {published},
tppubtype = {article}
}
Titanium-based and cobalt-chrome alloys have been widely used in orthopaedic applications as these materials can significantly enhance the quality of human life as implant materials. The longevity of these materials is highly influenced by their mechanical properties. In some devices cobalt chrome components articulate with titanium alloy counter faces (e.g. in the taper connections of stems and femoral heads in modern modular designs) and damage has been reported of the harder cobalt chrome by the softer titanium alloy component. This study attempts to understand why this might occur by investigating bulk and surface mechanical properties (such as hardness and Young's modulus) of a number of hip implants and test samples using a Hysitron Triboindenter. AFM images were also obtained to determine the contact area and hence, pile-up correction factors.
The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.
The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.
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