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Biomechanical model of human thorax
Track 5. Occupational and Impact Injury Biomechanics
examined. Attention was given to the testing protocol for compression, dealing with the presence of a fluid layer on the surface of the sample. This fluid layer was found to affect the test results due to surface tension. Based on these experiments, a new differential constitutive model was developed to describe the non-linear behaviour. This model was fitted to the loading and relaxation parts of stress relaxation test in both deformation modes. The performance in other deformation modes, such as tension, remains to be validated. The constitutive equation was implemented in the explicit finite element code MADYMO and it was used in finite element simulations with a numerical head model. 5237 We, 09:15-09:30 (P28) Comparison of intracranial pressure response to cadaver head kinematics W.N. Hardy, M.J. Mason, C.D. Foster, K.H. Yang, A.I. King. Bioengineering Center, Wayne State University, Detroit, Michigan, USA The focus of this study is the investigation of head injury mechanisms, specifically the measurement of the pressures developed within brain tissue during various impact conditions, and the comparison of these pressures to generalized head kinematics. Controlled impacts of inverted, artificial CSF perfused, human cadaver head preparations were conducted. These combined linear and angular acceleration impacts generated rotation in the sagittal, coronal, or horizontal plane. The specimens were stopped against a rigid surface from steady-state motion. The impacts were conducted in either the AP or lateral direction. Impact locations included the frontal, temporoparietal, and occipitoparietal regions, with and without a helmet. Two cranial pressure transducers (Entran EPBB02-500P) were implanted in the brain tissue near the coup and contrecoup sites. Pressures within the brain were compared to the kinematics of the skull, which were measured using a nine-accelerometer array. Twenty-three impacts were performed using seven cadavers. Typically, the coup pressure responses were positive, and the contrecoup pressure responses were negative. The peak pressures obtained during frontal impact were comparable to those observed by Nahum et al. (1977) for similar tests. The coup pressures ranged from 34 to 145 kPa, and the contrecoup pressures ranged from -2 to -48 kPa. The duration of the initial pressure pulses ranged from 3.0 to 10.5 ms, averaging 4.6 ms. Peak coup pressure was found to be linearly related to peak resultant linear acceleration at the center of gravity (c.g.) of the head with correlation coefficient R=0.92. Correlation between coup pressure time histories and resultant linear acceleration at the c.g. showed the pressure response to lag acceleration by approximately 0.25 ms. No relationship between pressure and angular acceleration or angular speed was found. Helmet use was shown to decrease peak intracranial pressure. References Nahum, AM; Smith R; Ward, CC (1977) Intracranial pressure dynamics during head impact. Proc. 21st Stapp Car Crash Conf.
5499 We, 09:30-09:45 (P28) The indentation of brain tissues S. Cheng 1,2, K. Leung 2, L. Bilston 1. 1Prince ef Wales Medical Research Institute, UNSW, Sydney, Australia, 2Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia The mechanical properties of brain tissue have been previously measured using conventional mechanical test protocols such as shear, unconfined compression, indentation and tension. In the previous experimental work on indentation, the whole brain was indented. The brain is composed of various types of tissues with varying ultrastructural arrangements that suggested their differences in mechanical behavior. However, isolating and excising these tissues from their surroundings is very difficult and may affect mechanical properties. Indentation is therefore advantageous since this method allows us to measure the regional properties of the brain. In addition, previous constitutive models of the brain have assumed the tissue as a single phase material. However, ultrastructural studies of the brain have clearly demonstrated that the brain is a two-phase material with the neurological tissues bathed in interstitial fluid. Stress relaxation and creep experiments were performed on the cortical gray mantle, the periventricular white matter and the spinal cord. Finite element models of both the indenter and tissues were constructed. The soils consolidation procedure in Abaqus was used in this study. By using a single set of mechanical parameters, the experimental results were adequately described using the theory of poroviscoelasticity. The white matter that is adjacent to the spinal cord was found to be stiffer than those in the periventricular regions.
5.5. Thorax Injury Biomechanics
$155
5.5. Thorax Injury Biomechanics 5044 We, 11:00-11:15 (P30) Enhanced method and tools for child thoracic and abdominal compliance assessment by clinical treatments observation F. Bermond 1, J. Bergeau2, F. Alonzo 1, C. Goube113, K. Bruy~re 1, P. Joffrin 1, B. Cossalter2, J.-P. Verriest 1. IlNRETS - LBMC, Bren, France, 2Universit6 Joseph Fourier Grenoble 1, Ecole de Kin~sith~rapie du Centre Hospitalier Universitaire de Grenoble, Echirelles, France, 3New at LIER S.A., Lyon Saint Exup6ry A~roport, France The aim of our study is to obtain realistic values of child thoracic and abdominal compliance. The thoracic and abdominal compliance represents the capacity of deformation under the effect of mechanical solicitation. The dynamic response of the thoracic and abdominal segment is essential because it is one of the main parameters of the whole restraint mechanism in a car child restrain device. We propose to quantify the thoracic and abdominal compliance in observing thoracic and abdominal manipulations carried out within the framework of usual physiotherapic treatments. All the measurements will be done without any contact with the children. Only the displacement of the upper face of the practitioner's hand and the applied load will be recorded. A three dimensional analysis will be performed to reconstruct the displacement. Furthermore the value distribution as a function of several variables such as age, sex and anthropometrics will be taken into account. This research will be used to improve the bio-fidelity of the chest and abdomen of child dummies in order to better evaluate the thoracic and abdominal injury risk for children involved in road accidents. This more realistic prediction of the child injury severity in the case of a collision may have a positive effect on road safety. Indeed, those new data will allow a better evaluation of the current and future restraint systems, for example in the frame of vehicle homologation test procedures as the EuroNCAP. 5574 We, 11 : 15-11:30 (P30) Biomechanical model of human thorax L. Cihalov& Department of mechanics, Faculty of Applied Sciences, University of West Bohemia, Plzeh, Czech Republic The area of biomechanical simulation has been rapidly advancing in several last year. The reason for this growth is saving of costs and time. The FEM has been considered to be the best tool for modeling of objects with complex geometry, multiple material compositions and complicated loading conditions, such as the human organs are. Spatial arrangements and material properties of individual organs are very important for generation and consequent validation of individual organs. The aim of this biomechanical study has been addressed to thoracic parts. Therefore the parts such as sternum, ribs, vertebrae with intervertebral discs, costicartilages connecting sternum with ribs, lungs and heart with great rhexis have been modeled. The thoracic cavity has been separated from the abdominal cavity by diaphragm. The abdominal cavity has been represented by the biobag with incompressible fluid inside. The photographs of Visible Human Project have been fundamental for the creation of organ's geometry. These reduced photographs have been loaded into Amira software, where the boundaries of individual organs have been marked with respect to anatomical facts and where the geometry created by tetrahedral grids of thoracic parts has been established. These grids have been exported to Hypermesh software, where the organs have been embedded into themselves and tetrahedral grids have been replaced by hexahedral. The organs have been described by the material types offered by PAM-CRASHTM/SAFE TM software. The material properties, which completed the model, have been obtained from internet site. The whole model has been validated by frontal impactor Kroell test in PAM-CRASHTM/SAFE TM. The impact speed 4.gm/s, 6.7m/s and 9.gm/s, respectively have been applied. During the testing the injury criterion such as chest deflection has been investigated. Validated model will be embedded into the model of the whole human body. The thoracic model is of great scientific importance and serves not only for the safety simulations including studies of thoracic injury criteria, but also for simulation of given impact scenarios. 6593 We, 11:30-11:45 (P30) Material and structure characterization of human ribs E. Charpail 1,2, S. Laporte 1, X. Trosseille 2, G. Valancien3, F. Lavaste1. 1LBM, ENSAM, Paris, France, 2LAB, GIE Renault PSA Peugeot-Citroen, Nanterre, France, 3Universit~ Ren~ Descartes, Paris, France Complex finite element models are used to simulate mechanical thorax behaviour in automotive crashes., A better knowledge of rib material properties and structure is necessary to improve biofidelity. The purpose of this study was
examined. Attention was given to the testing protocol for compression, dealing with the presence of a fluid layer on the surface of the sample. This fluid layer was found to affect the test results due to surface tension. Based on these experiments, a new differential constitutive model was developed to describe the non-linear behaviour. This model was fitted to the loading and relaxation parts of stress relaxation test in both deformation modes. The performance in other deformation modes, such as tension, remains to be validated. The constitutive equation was implemented in the explicit finite element code MADYMO and it was used in finite element simulations with a numerical head model. 5237 We, 09:15-09:30 (P28) Comparison of intracranial pressure response to cadaver head kinematics W.N. Hardy, M.J. Mason, C.D. Foster, K.H. Yang, A.I. King. Bioengineering Center, Wayne State University, Detroit, Michigan, USA The focus of this study is the investigation of head injury mechanisms, specifically the measurement of the pressures developed within brain tissue during various impact conditions, and the comparison of these pressures to generalized head kinematics. Controlled impacts of inverted, artificial CSF perfused, human cadaver head preparations were conducted. These combined linear and angular acceleration impacts generated rotation in the sagittal, coronal, or horizontal plane. The specimens were stopped against a rigid surface from steady-state motion. The impacts were conducted in either the AP or lateral direction. Impact locations included the frontal, temporoparietal, and occipitoparietal regions, with and without a helmet. Two cranial pressure transducers (Entran EPBB02-500P) were implanted in the brain tissue near the coup and contrecoup sites. Pressures within the brain were compared to the kinematics of the skull, which were measured using a nine-accelerometer array. Twenty-three impacts were performed using seven cadavers. Typically, the coup pressure responses were positive, and the contrecoup pressure responses were negative. The peak pressures obtained during frontal impact were comparable to those observed by Nahum et al. (1977) for similar tests. The coup pressures ranged from 34 to 145 kPa, and the contrecoup pressures ranged from -2 to -48 kPa. The duration of the initial pressure pulses ranged from 3.0 to 10.5 ms, averaging 4.6 ms. Peak coup pressure was found to be linearly related to peak resultant linear acceleration at the center of gravity (c.g.) of the head with correlation coefficient R=0.92. Correlation between coup pressure time histories and resultant linear acceleration at the c.g. showed the pressure response to lag acceleration by approximately 0.25 ms. No relationship between pressure and angular acceleration or angular speed was found. Helmet use was shown to decrease peak intracranial pressure. References Nahum, AM; Smith R; Ward, CC (1977) Intracranial pressure dynamics during head impact. Proc. 21st Stapp Car Crash Conf.
5499 We, 09:30-09:45 (P28) The indentation of brain tissues S. Cheng 1,2, K. Leung 2, L. Bilston 1. 1Prince ef Wales Medical Research Institute, UNSW, Sydney, Australia, 2Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia The mechanical properties of brain tissue have been previously measured using conventional mechanical test protocols such as shear, unconfined compression, indentation and tension. In the previous experimental work on indentation, the whole brain was indented. The brain is composed of various types of tissues with varying ultrastructural arrangements that suggested their differences in mechanical behavior. However, isolating and excising these tissues from their surroundings is very difficult and may affect mechanical properties. Indentation is therefore advantageous since this method allows us to measure the regional properties of the brain. In addition, previous constitutive models of the brain have assumed the tissue as a single phase material. However, ultrastructural studies of the brain have clearly demonstrated that the brain is a two-phase material with the neurological tissues bathed in interstitial fluid. Stress relaxation and creep experiments were performed on the cortical gray mantle, the periventricular white matter and the spinal cord. Finite element models of both the indenter and tissues were constructed. The soils consolidation procedure in Abaqus was used in this study. By using a single set of mechanical parameters, the experimental results were adequately described using the theory of poroviscoelasticity. The white matter that is adjacent to the spinal cord was found to be stiffer than those in the periventricular regions.
5.5. Thorax Injury Biomechanics
$155
5.5. Thorax Injury Biomechanics 5044 We, 11:00-11:15 (P30) Enhanced method and tools for child thoracic and abdominal compliance assessment by clinical treatments observation F. Bermond 1, J. Bergeau2, F. Alonzo 1, C. Goube113, K. Bruy~re 1, P. Joffrin 1, B. Cossalter2, J.-P. Verriest 1. IlNRETS - LBMC, Bren, France, 2Universit6 Joseph Fourier Grenoble 1, Ecole de Kin~sith~rapie du Centre Hospitalier Universitaire de Grenoble, Echirelles, France, 3New at LIER S.A., Lyon Saint Exup6ry A~roport, France The aim of our study is to obtain realistic values of child thoracic and abdominal compliance. The thoracic and abdominal compliance represents the capacity of deformation under the effect of mechanical solicitation. The dynamic response of the thoracic and abdominal segment is essential because it is one of the main parameters of the whole restraint mechanism in a car child restrain device. We propose to quantify the thoracic and abdominal compliance in observing thoracic and abdominal manipulations carried out within the framework of usual physiotherapic treatments. All the measurements will be done without any contact with the children. Only the displacement of the upper face of the practitioner's hand and the applied load will be recorded. A three dimensional analysis will be performed to reconstruct the displacement. Furthermore the value distribution as a function of several variables such as age, sex and anthropometrics will be taken into account. This research will be used to improve the bio-fidelity of the chest and abdomen of child dummies in order to better evaluate the thoracic and abdominal injury risk for children involved in road accidents. This more realistic prediction of the child injury severity in the case of a collision may have a positive effect on road safety. Indeed, those new data will allow a better evaluation of the current and future restraint systems, for example in the frame of vehicle homologation test procedures as the EuroNCAP. 5574 We, 11 : 15-11:30 (P30) Biomechanical model of human thorax L. Cihalov& Department of mechanics, Faculty of Applied Sciences, University of West Bohemia, Plzeh, Czech Republic The area of biomechanical simulation has been rapidly advancing in several last year. The reason for this growth is saving of costs and time. The FEM has been considered to be the best tool for modeling of objects with complex geometry, multiple material compositions and complicated loading conditions, such as the human organs are. Spatial arrangements and material properties of individual organs are very important for generation and consequent validation of individual organs. The aim of this biomechanical study has been addressed to thoracic parts. Therefore the parts such as sternum, ribs, vertebrae with intervertebral discs, costicartilages connecting sternum with ribs, lungs and heart with great rhexis have been modeled. The thoracic cavity has been separated from the abdominal cavity by diaphragm. The abdominal cavity has been represented by the biobag with incompressible fluid inside. The photographs of Visible Human Project have been fundamental for the creation of organ's geometry. These reduced photographs have been loaded into Amira software, where the boundaries of individual organs have been marked with respect to anatomical facts and where the geometry created by tetrahedral grids of thoracic parts has been established. These grids have been exported to Hypermesh software, where the organs have been embedded into themselves and tetrahedral grids have been replaced by hexahedral. The organs have been described by the material types offered by PAM-CRASHTM/SAFE TM software. The material properties, which completed the model, have been obtained from internet site. The whole model has been validated by frontal impactor Kroell test in PAM-CRASHTM/SAFE TM. The impact speed 4.gm/s, 6.7m/s and 9.gm/s, respectively have been applied. During the testing the injury criterion such as chest deflection has been investigated. Validated model will be embedded into the model of the whole human body. The thoracic model is of great scientific importance and serves not only for the safety simulations including studies of thoracic injury criteria, but also for simulation of given impact scenarios. 6593 We, 11:30-11:45 (P30) Material and structure characterization of human ribs E. Charpail 1,2, S. Laporte 1, X. Trosseille 2, G. Valancien3, F. Lavaste1. 1LBM, ENSAM, Paris, France, 2LAB, GIE Renault PSA Peugeot-Citroen, Nanterre, France, 3Universit~ Ren~ Descartes, Paris, France Complex finite element models are used to simulate mechanical thorax behaviour in automotive crashes., A better knowledge of rib material properties and structure is necessary to improve biofidelity. The purpose of this study was