elisabetta zanetti - Profile on Academia.edu (original) (raw)
Papers by elisabetta zanetti
Bladder tissue biomechanical behavior: Experimental tests and constitutive formulation
Journal of Biomechanics, Sep 1, 2015
A procedure for the constitutive analysis of bladder tissues mechanical behavior is provided, by ... more A procedure for the constitutive analysis of bladder tissues mechanical behavior is provided, by using a coupled experimental and computational approach. The first step pertains to the design and development of mechanical tests on specimens from porcine bladders. The bladders have been harvested, and the specimens have been subjected to uniaxial cyclic tests at different strain rates along preferential directions, considering the distribution of tissue fibrous components. Experimental results showed the anisotropic, non-linear and time-dependent stress-strain behavior, due to tissue conformation with fibers distributed along preferential directions and their interaction phenomena with ground substance. In detail, experimental data showed a greater tissue stiffness along transversal direction. Viscous behavior was assessed by strain rate dependence of stress-strain curves and hysteretic phenomena. The second step pertains the development of a specific fiber-reinforced visco-hyperelastic constitutive model, in the light of bladder tissues structural conformation and experimental results. Constitutive parameters have been identified by minimizing the discrepancy between model and experimental data. The agreement between experimental and model results represent a term for evaluating the reliability of the constitutive models by means of the proposed operational procedure.
Driver-Handlebar Injury in Scooter-Car Collision
Journal of Biomechanics, Jul 1, 2012
In bicycle and scooter accidents, direct impact with the handlebar can cause serious abdominal in... more In bicycle and scooter accidents, direct impact with the handlebar can cause serious abdominal injuries, even in low-speed crashes (Nadler et al, 2005). Most abdominal injuries occur in automobile accidents (Stalnaker, 1985); therefore injury criteria have been developed with reference to car accident with frontal or lateral impact. In frontal impact; driver-steering wheel collision can be readily assimilated to scooter-driver handlebar collision. A thorough review of the abdominal injury criteria has been recently introduced inside a European project APROSYS (Advanced Protective Systems), focused on scientific and technology development in the field of passive safety. According to this review, peak force injury criteria is one of the most suitable criteria for the analysis of driver-handlebar collision.
Progetto e costruzione di un sistema di carico per il bacino umano
Metodi numerici e sperimentali per la valutazione pre-clinica di ricostruzioni complesse
Stress pattern in a prosthetic stem: FE comparison between the standardised experimental fatigue test (ISO 7206) and actual stresses on an implanted stem
Frontal Vehicle-End Optimization in Relation to Pedestrian-Car Impact
Journal of Biomechanics, Jul 1, 2012
Bioengineering, Feb 29, 2024
Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various field... more Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.
Ex vivo biomechanical evaluation of polyester and polyblend suture techniques to perform equine laryngoplasty
Veterinary Surgery, Feb 7, 2022
ObjectiveTo validate the use of a polyblend tape suture in equine laryngoplasty (PL).Study design... more ObjectiveTo validate the use of a polyblend tape suture in equine laryngoplasty (PL).Study designExperimental study.AnimalsThirty‐two cadaveric larynges.MethodsEach larynx was randomly assigned to 1 of 4 groups: PL with polyblend tape suture (TigerTape), without (TT) or with a cannula (TTC) in the muscular process of the arytenoid cartilage, and PL with polyester suture (Ethibond), without (EB) or with a cannula (EBC). Construct stiffness, total migration, creep, and drift values were measured after 3000 cycles. The specimens were then loaded to failure to assess their residual properties: load at failure, total energy, displacement, and 2 stiffness coefficients.ResultsAfter cyclic testing, the total migration and creep were lower in TTC (6.36 ± 1.20 mm; 1.35 ± 0.38 mm/s) than in EB (11.12 ± 4.20 mm; 3.39 ± 2.68 mm/s) and in the TT constructs (11.26 ± 1.49 mm; 3.20 ± 0.54 mm/s); however, no difference was found with EBC (9.19 ± 3.18 mm; 2.14 ± 0.99). A correlation was found between total migration and creep (R = .85). The TTC constructs failed at higher loads (129.51 ± 33.84 N) than EB (93.16 ± 18.21 N) and EBC (81.72 ± 13.26 N) whereas the EB and EBC constructs were less stiff than TT and TTC (P < .001).ConclusionBiomechanical properties were generally superior for the TTC constructs tested under cyclical loading. The TT and TTC constructs failed at a higher load than EB and EBC constructs. The cannula in TTC and EBC reduced the failure at the muscular process.Clinical significanceThese results provide evidence to support the in vivo evaluation of the polyblend tape suture with or without a cannula in the muscular process for laryngoplasty in horses.
Applied sciences, Jun 3, 2021
Principal components analysis is a powerful technique which can be used to reduce data dimensiona... more Principal components analysis is a powerful technique which can be used to reduce data dimensionality. With reference to three-dimensional bone shape models, it can be used to generate an unlimited number of models, defined by thousands of nodes, from a limited (less than twenty) number of scalars. The full procedure has been here described in detail and tested. Two databases were used as input data: the first database comprised 40 mandibles, while the second one comprised 98 proximal femurs. The "average shape" and principal components that were required to cover at least 90% of the whole variance were identified for both bones, as well as the statistical distributions of the respective principal components weights. Fifteen principal components sufficed to describe the mandibular shape, while nine components sufficed to describe the proximal femur morphology. A routine has been set up to generate any number of mandible or proximal femur geometries, according to the actual statistical shape distributions. The set-up procedure can be generalized to any bone shape given a sufficiently large database of the respective 3D shapes.
International Journal On Interactive Design And Manufacturing (ijidem), Jul 25, 2023
Human computer models represent a useful tool for investigating the human body response to extern... more Human computer models represent a useful tool for investigating the human body response to external static/dynamic loads or for human-centred design. Articulated Total Body (ATB) models are the simplest human multibody models, where body segments are represented by ellipsoids joined at skeletal articulations. Over the years, regression models on both living subjects' and cadavers' data have been developed to predict body segments properties. These models are affected by two main limitations: the only inputs are the subject's weight and height, not considering that for the same combination different morphologies can exist; secondly, regression analyses were performed over a specific population not including peculiar morphologies (under-weight or obese). A novel methodology for developing anthropomorphic ATB models is here presented: a statistical shape model able to predict the external geometry of the human body from a limited set of anthropometric measurements was implemented and body segments were obtained by segmentation; the respective inertial properties were computed from volumes, assuming a constant density value. The properties of this new anthropomorphic ATB model were compared to those calculated by GEBOD (Generator of Body Data), a well-known programme for ATB data calculation. A virtual population of twenty subjects was analysed: with reference to the inertial properties the most relevant differences occurred at the abdomen and the thighs segments (60% relative error), while the trunk, the shoulder and the calves represent the most critical areas for the geometry reconstruction (50 mm average error). The significance of these outcomes was investigated performing multibody simulations with various scenarios. Multibody modelling • Articulated total body model • Principal component analysis • Accident • Forensic biomechanics • CAESAR database B G. Pascoletti
Design of a Snap-Fit Joint Through a Multibody Model
Springer eBooks, Sep 25, 2022
A Benchmark of Traditional Visual Descriptors and Convolutional Networks ‘Off-the-Shelf’ for Anomaly Detection
Springer eBooks, Sep 25, 2022
Journal of Biomedical Graphics and Computing, Sep 17, 2012
Background: computerised image analysis and the building of electronic archives require the digit... more Background: computerised image analysis and the building of electronic archives require the digitisation of x-ray films performed in the past, when direct digitisation was not yet available. Different techniques can be used, based on laser scanning or camera acquisition; both can be heavily impaired by the non-uniformity of the backlighting source. This work wants to develop a methodology, able to reduce this noise source. The introduced algorithm is a step beyond the common compensation of backlighting non-uniformity through subtraction; in fact, each grey level is corrected taking into account not only its position on the back-lighting system and its raw value, but also the interaction between these two parameters. Results: Given a certain acquisition system, the introduced algorithm has allowed to reduce the maximum grey level standard deviation, read on uniform grey level films, from 9.15 to 2.00 (on a scale from 0 to 255) against traditional subtraction techniques that achieved a minimum standard deviation equal to 5.39. The employed algorithm has proved to be effective in order to obtain same measured grey levels, almost independent from the position of the radiograph on the back-lighting system, and therefore makes x ray image digitisation more accurate.
Biorheology, 2012
The fundamental passive mechanical properties of the bladder need to be known in order to design ... more The fundamental passive mechanical properties of the bladder need to be known in order to design the most appropriate long-term surgical repair procedures and develop materials for bladder reconstruction. This study has focused on the bladder tissue viscoelastic behavior, providing a comprehensive analysis of the effects of fibers orientation, strain rate and loading history. Whole bladders harvested from one year old fat pigs (160 kg approximate weight) were dissected along the apex-to-base direction and samples were isolated from the lateral region of the wall, as well as along apex-to-base and transverse directions. Uniaxial monotonic (stress relaxation) and cyclic tests at different frequencies have been performed with the Bose Electroforce ® 3200. Normalized stress relaxation functions have been interpolated using a second order exponential series and loading and unloading stress-strain curves have been interpolated with a non-linear elastic model. The passive mechanical behavior of bladder tissue was shown to be heavily influenced by frequency and loading history, both in monotonic and cyclic tests. The anisotropy of the tissue was evident in monotonic and in cyclic tests as well, especially in tests performed on an exercised tissue and at high frequencies. In contrast, transverse and apex-to-base samples demonstrated an analogous relaxation behavior.
A 3D printed conversion device for the equi-biaxial mechanical characterization of human acellular dermal matrix
WIT transactions on engineering sciences, Jun 21, 2017
Human Acellular Dermal Matrices (HADMs) have recently been employed in reconstructive surgeries w... more Human Acellular Dermal Matrices (HADMs) have recently been employed in reconstructive surgeries which involve high mechanical resistance prerequisites (e.g. rotator cuff tears repair, Achilles tendon augmentation, breast reconstruction procedure, hernia repair), having proved its non-immunogenic response and promising mechanical properties. Nevertheless, a thorough mechanical characterization is needed in order to test HADMs response when subjected to stress levels comparable to those experienced in vivo, to confirm its applicability to the above mentioned surgical fields and to provide precise indications to surgeons. HADMs specimens have undergone biaxial tests through a custom made biaxial fixture interfaced with a uniaxial universal testing machine. Stress-strain curves were evaluated from biaxial loads measured by two load cells, and the optical measure of the displacement of four markers located in central area of specimens. Comparisons among the native human reticular dermis and HADMs demonstrated the loss of mechanical strength caused by the decellularization process. Moreover, the specimens resulted, on average, less extensible in the medio-lateral direction (namely, along the Langer lines) than in the cranio-caudal direction, confirming the correlation of dermis mechanical response with collagen fibers orientation.
Femoral implants comparison by means of thermoelastic stress analysis
Journal of Biomechanics, 2006
Journal of Biomechanics, Volume 39, Issue null, Pages S515-S516, 2006, Authors:EM Zanetti; SS Mus... more Journal of Biomechanics, Volume 39, Issue null, Pages S515-S516, 2006, Authors:EM Zanetti; SS Musso; AL Audenino.
Medical Engineering & Physics, Jul 1, 1996
Vide&ensitom&ric analysis has proved useful in the study of bone remodelling; however, for more e... more Vide&ensitom&ric analysis has proved useful in the study of bone remodelling; however, for more efJicient results, an investigation procedure that enables the comparison of X-rays is needed. In the present research an automated method has been developed which considerably speeds up the entire procedure through the implementation of specially designed C++ software. At present, a sequence of six X-rays can be analysed in about 1 h irrespective of the number of areas to be investigated, which can be arbitrarily increased (200 or more), Analysis is fast as well as more reliable and accurate. In clinical practice, the results off er an effective support to observations on the biomechanical behaviour of bone implant systems. Copyright
Correlation between thermography and internal damping in metals
International Journal of Fatigue, Apr 1, 2003
The object of this paper is an investigation of the relationship existing between two experimenta... more The object of this paper is an investigation of the relationship existing between two experimental techniques, both aimed at the assessment of micro-plastic phenomena and micro-friction inside a material: thermographic analysis and specific damping measurement. A model has been developed here considering the main thermal effects during fatigue tests, and a theoretical relationship between temperature increment and specific damping has been proposed. Successively, an extensive experimentation has been carried on groups ...
WIT transactions on engineering sciences, Jun 21, 2017
Finite element models, in conjunction with adequate constitutive relations of the materials invol... more Finite element models, in conjunction with adequate constitutive relations of the materials involved, have proved to be crucial in many medical applications, such as in surgical planning. Nevertheless, a thorough numerical analysis of dermis' mechanical response is a challenging research area because of dermis' highly anisotropic and nonlinear behaviour. The aim of this work has been to assess the performance of two orthotropic and one isotropic hyper-elastic constitutive laws, providing an experimental-computational framework for the definition of reliable constitutive models of dermis tissue. Experimental, equi-biaxial stress-strain data obtained on human reticular dermis specimens have been exploited in order to extract, through a stochastic optimization procedure, constitutive parameters of three widely used constitutive laws: the Ogden, Holzapfel and Gasser-Ogden-Holzapfel (GOH) models. A set of specimen specific parameters and a set of best matching parameters, determined by simultaneously fitting all experimental stress-strain curves, have been obtained. The goodness of the selected laws has been assessed by means of FEM simulations performed in Abaqus (Simulia, Dessault Systèmes Inc.) which reproduce the actual specimen boundary conditions and geometry, rebuilt through an image segmentation process implemented in MATLAB (The MathWorks, Inc.). Models have been validated comparing experimental and numerical outcomes related to reference points on the specimen surface. In the preliminary fitting phase, Normalized Root Mean Square Error values were above 0.9 for the specimen-specific and above 0.54 for the best matching models. The comparison between numerical and experimental outcomes has highlighted the inadequacy of the isotropic constitutive law in reproducing the dermis behaviour, particularly at higher stretch levels. Errors obtained in the horizontal loading direction are lower than 40% for Holzapfel and GOH models, while the Ogden model reaches the 80%. Lower and more uniform errors occur in the orthogonal direction, which settles below 30% for the orthotropic laws, while it increases up to 40% in the isotropic case.
Bladder tissue biomechanical behavior: Experimental tests and constitutive formulation
Journal of Biomechanics, Sep 1, 2015
A procedure for the constitutive analysis of bladder tissues mechanical behavior is provided, by ... more A procedure for the constitutive analysis of bladder tissues mechanical behavior is provided, by using a coupled experimental and computational approach. The first step pertains to the design and development of mechanical tests on specimens from porcine bladders. The bladders have been harvested, and the specimens have been subjected to uniaxial cyclic tests at different strain rates along preferential directions, considering the distribution of tissue fibrous components. Experimental results showed the anisotropic, non-linear and time-dependent stress-strain behavior, due to tissue conformation with fibers distributed along preferential directions and their interaction phenomena with ground substance. In detail, experimental data showed a greater tissue stiffness along transversal direction. Viscous behavior was assessed by strain rate dependence of stress-strain curves and hysteretic phenomena. The second step pertains the development of a specific fiber-reinforced visco-hyperelastic constitutive model, in the light of bladder tissues structural conformation and experimental results. Constitutive parameters have been identified by minimizing the discrepancy between model and experimental data. The agreement between experimental and model results represent a term for evaluating the reliability of the constitutive models by means of the proposed operational procedure.
Driver-Handlebar Injury in Scooter-Car Collision
Journal of Biomechanics, Jul 1, 2012
In bicycle and scooter accidents, direct impact with the handlebar can cause serious abdominal in... more In bicycle and scooter accidents, direct impact with the handlebar can cause serious abdominal injuries, even in low-speed crashes (Nadler et al, 2005). Most abdominal injuries occur in automobile accidents (Stalnaker, 1985); therefore injury criteria have been developed with reference to car accident with frontal or lateral impact. In frontal impact; driver-steering wheel collision can be readily assimilated to scooter-driver handlebar collision. A thorough review of the abdominal injury criteria has been recently introduced inside a European project APROSYS (Advanced Protective Systems), focused on scientific and technology development in the field of passive safety. According to this review, peak force injury criteria is one of the most suitable criteria for the analysis of driver-handlebar collision.
Progetto e costruzione di un sistema di carico per il bacino umano
Metodi numerici e sperimentali per la valutazione pre-clinica di ricostruzioni complesse
Stress pattern in a prosthetic stem: FE comparison between the standardised experimental fatigue test (ISO 7206) and actual stresses on an implanted stem
Frontal Vehicle-End Optimization in Relation to Pedestrian-Car Impact
Journal of Biomechanics, Jul 1, 2012
Bioengineering, Feb 29, 2024
Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various field... more Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.
Ex vivo biomechanical evaluation of polyester and polyblend suture techniques to perform equine laryngoplasty
Veterinary Surgery, Feb 7, 2022
ObjectiveTo validate the use of a polyblend tape suture in equine laryngoplasty (PL).Study design... more ObjectiveTo validate the use of a polyblend tape suture in equine laryngoplasty (PL).Study designExperimental study.AnimalsThirty‐two cadaveric larynges.MethodsEach larynx was randomly assigned to 1 of 4 groups: PL with polyblend tape suture (TigerTape), without (TT) or with a cannula (TTC) in the muscular process of the arytenoid cartilage, and PL with polyester suture (Ethibond), without (EB) or with a cannula (EBC). Construct stiffness, total migration, creep, and drift values were measured after 3000 cycles. The specimens were then loaded to failure to assess their residual properties: load at failure, total energy, displacement, and 2 stiffness coefficients.ResultsAfter cyclic testing, the total migration and creep were lower in TTC (6.36 ± 1.20 mm; 1.35 ± 0.38 mm/s) than in EB (11.12 ± 4.20 mm; 3.39 ± 2.68 mm/s) and in the TT constructs (11.26 ± 1.49 mm; 3.20 ± 0.54 mm/s); however, no difference was found with EBC (9.19 ± 3.18 mm; 2.14 ± 0.99). A correlation was found between total migration and creep (R = .85). The TTC constructs failed at higher loads (129.51 ± 33.84 N) than EB (93.16 ± 18.21 N) and EBC (81.72 ± 13.26 N) whereas the EB and EBC constructs were less stiff than TT and TTC (P < .001).ConclusionBiomechanical properties were generally superior for the TTC constructs tested under cyclical loading. The TT and TTC constructs failed at a higher load than EB and EBC constructs. The cannula in TTC and EBC reduced the failure at the muscular process.Clinical significanceThese results provide evidence to support the in vivo evaluation of the polyblend tape suture with or without a cannula in the muscular process for laryngoplasty in horses.
Applied sciences, Jun 3, 2021
Principal components analysis is a powerful technique which can be used to reduce data dimensiona... more Principal components analysis is a powerful technique which can be used to reduce data dimensionality. With reference to three-dimensional bone shape models, it can be used to generate an unlimited number of models, defined by thousands of nodes, from a limited (less than twenty) number of scalars. The full procedure has been here described in detail and tested. Two databases were used as input data: the first database comprised 40 mandibles, while the second one comprised 98 proximal femurs. The "average shape" and principal components that were required to cover at least 90% of the whole variance were identified for both bones, as well as the statistical distributions of the respective principal components weights. Fifteen principal components sufficed to describe the mandibular shape, while nine components sufficed to describe the proximal femur morphology. A routine has been set up to generate any number of mandible or proximal femur geometries, according to the actual statistical shape distributions. The set-up procedure can be generalized to any bone shape given a sufficiently large database of the respective 3D shapes.
International Journal On Interactive Design And Manufacturing (ijidem), Jul 25, 2023
Human computer models represent a useful tool for investigating the human body response to extern... more Human computer models represent a useful tool for investigating the human body response to external static/dynamic loads or for human-centred design. Articulated Total Body (ATB) models are the simplest human multibody models, where body segments are represented by ellipsoids joined at skeletal articulations. Over the years, regression models on both living subjects' and cadavers' data have been developed to predict body segments properties. These models are affected by two main limitations: the only inputs are the subject's weight and height, not considering that for the same combination different morphologies can exist; secondly, regression analyses were performed over a specific population not including peculiar morphologies (under-weight or obese). A novel methodology for developing anthropomorphic ATB models is here presented: a statistical shape model able to predict the external geometry of the human body from a limited set of anthropometric measurements was implemented and body segments were obtained by segmentation; the respective inertial properties were computed from volumes, assuming a constant density value. The properties of this new anthropomorphic ATB model were compared to those calculated by GEBOD (Generator of Body Data), a well-known programme for ATB data calculation. A virtual population of twenty subjects was analysed: with reference to the inertial properties the most relevant differences occurred at the abdomen and the thighs segments (60% relative error), while the trunk, the shoulder and the calves represent the most critical areas for the geometry reconstruction (50 mm average error). The significance of these outcomes was investigated performing multibody simulations with various scenarios. Multibody modelling • Articulated total body model • Principal component analysis • Accident • Forensic biomechanics • CAESAR database B G. Pascoletti
Design of a Snap-Fit Joint Through a Multibody Model
Springer eBooks, Sep 25, 2022
A Benchmark of Traditional Visual Descriptors and Convolutional Networks ‘Off-the-Shelf’ for Anomaly Detection
Springer eBooks, Sep 25, 2022
Journal of Biomedical Graphics and Computing, Sep 17, 2012
Background: computerised image analysis and the building of electronic archives require the digit... more Background: computerised image analysis and the building of electronic archives require the digitisation of x-ray films performed in the past, when direct digitisation was not yet available. Different techniques can be used, based on laser scanning or camera acquisition; both can be heavily impaired by the non-uniformity of the backlighting source. This work wants to develop a methodology, able to reduce this noise source. The introduced algorithm is a step beyond the common compensation of backlighting non-uniformity through subtraction; in fact, each grey level is corrected taking into account not only its position on the back-lighting system and its raw value, but also the interaction between these two parameters. Results: Given a certain acquisition system, the introduced algorithm has allowed to reduce the maximum grey level standard deviation, read on uniform grey level films, from 9.15 to 2.00 (on a scale from 0 to 255) against traditional subtraction techniques that achieved a minimum standard deviation equal to 5.39. The employed algorithm has proved to be effective in order to obtain same measured grey levels, almost independent from the position of the radiograph on the back-lighting system, and therefore makes x ray image digitisation more accurate.
Biorheology, 2012
The fundamental passive mechanical properties of the bladder need to be known in order to design ... more The fundamental passive mechanical properties of the bladder need to be known in order to design the most appropriate long-term surgical repair procedures and develop materials for bladder reconstruction. This study has focused on the bladder tissue viscoelastic behavior, providing a comprehensive analysis of the effects of fibers orientation, strain rate and loading history. Whole bladders harvested from one year old fat pigs (160 kg approximate weight) were dissected along the apex-to-base direction and samples were isolated from the lateral region of the wall, as well as along apex-to-base and transverse directions. Uniaxial monotonic (stress relaxation) and cyclic tests at different frequencies have been performed with the Bose Electroforce ® 3200. Normalized stress relaxation functions have been interpolated using a second order exponential series and loading and unloading stress-strain curves have been interpolated with a non-linear elastic model. The passive mechanical behavior of bladder tissue was shown to be heavily influenced by frequency and loading history, both in monotonic and cyclic tests. The anisotropy of the tissue was evident in monotonic and in cyclic tests as well, especially in tests performed on an exercised tissue and at high frequencies. In contrast, transverse and apex-to-base samples demonstrated an analogous relaxation behavior.
A 3D printed conversion device for the equi-biaxial mechanical characterization of human acellular dermal matrix
WIT transactions on engineering sciences, Jun 21, 2017
Human Acellular Dermal Matrices (HADMs) have recently been employed in reconstructive surgeries w... more Human Acellular Dermal Matrices (HADMs) have recently been employed in reconstructive surgeries which involve high mechanical resistance prerequisites (e.g. rotator cuff tears repair, Achilles tendon augmentation, breast reconstruction procedure, hernia repair), having proved its non-immunogenic response and promising mechanical properties. Nevertheless, a thorough mechanical characterization is needed in order to test HADMs response when subjected to stress levels comparable to those experienced in vivo, to confirm its applicability to the above mentioned surgical fields and to provide precise indications to surgeons. HADMs specimens have undergone biaxial tests through a custom made biaxial fixture interfaced with a uniaxial universal testing machine. Stress-strain curves were evaluated from biaxial loads measured by two load cells, and the optical measure of the displacement of four markers located in central area of specimens. Comparisons among the native human reticular dermis and HADMs demonstrated the loss of mechanical strength caused by the decellularization process. Moreover, the specimens resulted, on average, less extensible in the medio-lateral direction (namely, along the Langer lines) than in the cranio-caudal direction, confirming the correlation of dermis mechanical response with collagen fibers orientation.
Femoral implants comparison by means of thermoelastic stress analysis
Journal of Biomechanics, 2006
Journal of Biomechanics, Volume 39, Issue null, Pages S515-S516, 2006, Authors:EM Zanetti; SS Mus... more Journal of Biomechanics, Volume 39, Issue null, Pages S515-S516, 2006, Authors:EM Zanetti; SS Musso; AL Audenino.
Medical Engineering & Physics, Jul 1, 1996
Vide&ensitom&ric analysis has proved useful in the study of bone remodelling; however, for more e... more Vide&ensitom&ric analysis has proved useful in the study of bone remodelling; however, for more efJicient results, an investigation procedure that enables the comparison of X-rays is needed. In the present research an automated method has been developed which considerably speeds up the entire procedure through the implementation of specially designed C++ software. At present, a sequence of six X-rays can be analysed in about 1 h irrespective of the number of areas to be investigated, which can be arbitrarily increased (200 or more), Analysis is fast as well as more reliable and accurate. In clinical practice, the results off er an effective support to observations on the biomechanical behaviour of bone implant systems. Copyright
Correlation between thermography and internal damping in metals
International Journal of Fatigue, Apr 1, 2003
The object of this paper is an investigation of the relationship existing between two experimenta... more The object of this paper is an investigation of the relationship existing between two experimental techniques, both aimed at the assessment of micro-plastic phenomena and micro-friction inside a material: thermographic analysis and specific damping measurement. A model has been developed here considering the main thermal effects during fatigue tests, and a theoretical relationship between temperature increment and specific damping has been proposed. Successively, an extensive experimentation has been carried on groups ...
WIT transactions on engineering sciences, Jun 21, 2017
Finite element models, in conjunction with adequate constitutive relations of the materials invol... more Finite element models, in conjunction with adequate constitutive relations of the materials involved, have proved to be crucial in many medical applications, such as in surgical planning. Nevertheless, a thorough numerical analysis of dermis' mechanical response is a challenging research area because of dermis' highly anisotropic and nonlinear behaviour. The aim of this work has been to assess the performance of two orthotropic and one isotropic hyper-elastic constitutive laws, providing an experimental-computational framework for the definition of reliable constitutive models of dermis tissue. Experimental, equi-biaxial stress-strain data obtained on human reticular dermis specimens have been exploited in order to extract, through a stochastic optimization procedure, constitutive parameters of three widely used constitutive laws: the Ogden, Holzapfel and Gasser-Ogden-Holzapfel (GOH) models. A set of specimen specific parameters and a set of best matching parameters, determined by simultaneously fitting all experimental stress-strain curves, have been obtained. The goodness of the selected laws has been assessed by means of FEM simulations performed in Abaqus (Simulia, Dessault Systèmes Inc.) which reproduce the actual specimen boundary conditions and geometry, rebuilt through an image segmentation process implemented in MATLAB (The MathWorks, Inc.). Models have been validated comparing experimental and numerical outcomes related to reference points on the specimen surface. In the preliminary fitting phase, Normalized Root Mean Square Error values were above 0.9 for the specimen-specific and above 0.54 for the best matching models. The comparison between numerical and experimental outcomes has highlighted the inadequacy of the isotropic constitutive law in reproducing the dermis behaviour, particularly at higher stretch levels. Errors obtained in the horizontal loading direction are lower than 40% for Holzapfel and GOH models, while the Ogden model reaches the 80%. Lower and more uniform errors occur in the orthogonal direction, which settles below 30% for the orthotropic laws, while it increases up to 40% in the isotropic case.