Caroline DECK

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Infant Eye Finite‐Element Model for Injury Analysis

Motorradschutzhelme. Identifizierung ihres Verbesserungspotenzials unter Beruecksichtigung des Motorradunfallgeschehens

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Protection performance of bicycle helmets

Journal of Safety Research, 2019

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial| 4.0 International License

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Brain injury tolerance limit based on computation of axonal strain

Accident Analysis & Prevention, 2016

Traumatic brain injury (TBI) is the leading cause of death and permanent impairment over the last... more Traumatic brain injury (TBI) is the leading cause of death and permanent impairment over the last decades. In both the severe and mild TBIs, diffuse axonal injury (DAI) is the most common pathology and leads to axonal degeneration. Computation of axonal strain by using finite element head model in numerical simulation can enlighten the DAI mechanism and help to establish advanced head injury criteria. The main objective of this study is to develop a brain injury criterion based on computation of axonal strain. To achieve the objective a state-of-the-art finite element head model with enhanced brain and skull material laws, was used for numerical computation of real world head trauma. The implementation of new medical imaging data such as, fractional anisotropy and axonal fiber orientation from Diffusion Tensor Imaging (DTI) of 12 healthy patients into the finite element brain model was performed to improve the brain constitutive material law with more efficient heterogeneous anisotropic visco hyper-elastic material law. The brain behavior has been validated in terms of brain deformation against Hardy et al. (2001), Hardy et al. (2007), and in terms of brain pressure against Nahum et al. (1977) and Trosseille et al. (1992) experiments. Verification of model stability has been conducted as well. Further, 109 well-documented TBI cases were simulated and axonal strain computed to derive brain injury tolerance curve. Based on an in-depth statistical analysis of different intra-cerebral parameters (brain axonal strain rate, axonal strain, first principal strain, Von Mises strain, first principal stress, Von Mises stress, CSDM (0.10), CSDM (0.15) and CSDM (0.25)), it was shown that axonal strain was the most appropriate candidate parameter to predict DAI. The proposed brain injury tolerance limit for a 50% risk of DAI has been established at 14.65% of axonal strain. This study provides a key step for a realistic novel injury metric for DAI.

A critical literature review on primary blast thorax injury and their outcomes

Journal of Trauma and Acute Care Surgery, 2016

Since World War II, researchers have been interested in exploring the injury mechanisms involved ... more Since World War II, researchers have been interested in exploring the injury mechanisms involved in primary blast on the thorax by using animal model surrogates. These studies were mostly concerned with the finding of the lung injury threshold, the relationship between the physical components of the air blast wave, and the biological response. Studies have also been conducted to investigate the effect of repeated blast exposures on the injury outcome threshold. This has led to several injury criteria, such as the Bowen curves based on pressure history&#39;s characteristics or the Axelsson Chest Wall Velocity Predictor that used measurement from the mammals&#39; chest wall. This article aims at doing a critical literature review of this specific topic.

Modeling and Validation of the Human Liver and Kidney Models

Influence of head boundary conditions in pedestrian real world head trauma simulations

The aim of this work is to study the influence of head boundary conditions during real-world pede... more The aim of this work is to study the influence of head boundary conditions during real-world pedestrian head trauma simulation. Both Multi-Body System (MBS) and Finite Element (FE) models are used for pedestrian-versus-vehicle accident reconstructions. Four head boundary conditions are studied (from an isolated head to a head attached to the whole body). The effect of each configuration on head mechanical response parameters is computed. The responses include rigid-body kinematics responses as well as the intra-cerebral responses of a head FE model. It appears that head boundary conditions at neck level are significant, especially in terms of intra-cerebral response.

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$Research paper thumbnail of Development of skull fracture criterion based on real-world head trauma simulations using finite element head model$

Development of skull fracture criterion based on real-world head trauma simulations using finite element head model

Journal of the Mechanical Behavior of Biomedical Materials, 2016

The objective of this study was to enhance an existing finite element (FE) head model with compos... more The objective of this study was to enhance an existing finite element (FE) head model with composite modeling and a new constitutive law for the skull. The response of the state-ofthe-art FE head model was validated in the time domain using data from 15 temporoparietal impact experiments, conducted with postmortem human surrogates. The new model predicted skull fractures observed in these tests. Further, 70 well-documented head trauma cases were reconstructed. The 15 experiments and 70 real-world head trauma cases were combined to derive skull fracture injury risk curves. The skull internal energy was found to be the best candidate to predict skull failure based on an in depth statistical analysis of different mechanical parameters (force, skull internal energy), head kinematicbased parameter, the head injury criterion (HIC), and skull fracture correlate (SFC). The proposed tolerance limit for 50% risk of skull fracture was associated with 453 mJ of internal energy. Statistical analyses were extended for individual impact locations (frontal, occipital and temporo-parietal) and separate injury risk curves were obtained. The 50% risk of skull fracture for each location: frontal: 481 mJ, occipital: 457 mJ, temporo-parietal: 456 mJ of skull internal energy.

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Experimental and finite element analysis for prediction of kidney injury under blunt impact

Journal of Biomechanics, 2017

Kidneys are third most injured organs in abdominal trauma after liver and spleen; this study ther... more Kidneys are third most injured organs in abdominal trauma after liver and spleen; this study therefore is an attempt to understand the behaviour of kidneys under blunt trauma. Dynamic impact tests were performed on 20 fresh porcine kidneys to study the injury propagation in the organ, and the acceleration of the impactor was measured. A kidney model was developed with structural details like capsule and cortex. The kidney cortex was modelled with solid hexahedral elements and the capsule was modelled with quadratic shell elements. The material models for the capsule and cortex were used from the experimental data reported in our previous study. The developed model was calibrated using previous and current experimental results to reproduce the injuries of the organ in terms of acceleration of the impactor, and the injuries sustained by the organ during the experiments. The developed kidney model is observed to be robust and can be integrated with the available human body finite element models to simulate accidents and to predict or simulate injuries.

Towards advanced bicycle helmet test methods

This paper exposes a critical analysis of current bicycle helmet standard tests and proposes an a... more This paper exposes a critical analysis of current bicycle helmet standard tests and proposes an advanced test method. Different key aspects are considered consecutively, i.e. the bicyclist's head impact conditions in terms of velocity vector, head form boundary conditions, the headform itself with its instrumentation, the geometry of the impacted surface, the head impact location and finally the head injury criteria. Based on in deep analysis of bicycle accidents it has been shown that a significant component of the head velocity vector at the time of impact is the tangential velocity. On the other hand it has been shown that the head boundary condition at neck level does not play a significant role in the head response following to impact. Therefore it is suggested to consider tangential impacts against a helmeted Hybrid III dummy head, eventually connected to a Hybrid III neck. A critical analysis of the geometry of the impacted surface and the temperature at the time of accid...

$Research paper thumbnail of Composite FE human skull model validation and development of skull fracture criteria$

Composite FE human skull model validation and development of skull fracture criteria

An existing finite element head model is enhanced in terms of composite modeling and new constitu... more An existing finite element head model is enhanced in terms of composite modeling and new constitutive law for the skull. The advanced FE head model is validated against the entire time domain response obtained from 15 side impact experiments conducted with postmortem human surrogates. The new skull model is capable of reproducing skull fracture in a realistic way. Further, 70 well‐documented head trauma cases are reconstructed. The 15 experimental cases plus the 70 real‐world head trauma cases are finally put together to derive a skull fracture injury risk curve. Based on the statistical analysis of different mechanical parameters, the skull internal energy was the best candidate parameter to predict the skull failure. The proposed tolerance limit for 50% risk of skull fracture is 448mJ of skull internal energy.

Head Injury Assessment Based on Real-world Accidents Using FE Head Model

Head injury is one of the most frequent causes of death and impairment sustained by pedestrians, ... more Head injury is one of the most frequent causes of death and impairment sustained by pedestrians, cyclists, motorcyclists, vehicle occupants in road accidents and accounts for approximately half of the road fatalities in the European Union. Improved head injury assessment is now necessary to predict the potential head injury risk under different impact conditions. In the context of head trauma biomechanics, computational modeling of head proved as an efficient and very promising tool to study the head trauma and to better predict head injury. At present 15 well-documented car-pedestrian accidents (Age=35±17Yrs, weight=59±9kg, height=165±6 cm) were selected from Investigation of Vehicle Accidents in Changsha (IVAC) database for simulation with Strasbourg University Finite Element Head Model (SUFEHM), which is a full validated 50th percentile FE model under LS-DYNA with improved head injury criteria in terms of DAI, SDH and skull fracture. Kinematics of victims espescially head impact ...

New methodology for improvement of helmet performances during impacts with regards to biomechanical criteria

Materials & Design, 2012

In this study a new method for enhancing helmet performances during an impact is considered. In a... more In this study a new method for enhancing helmet performances during an impact is considered. In a first step an approved composite helmet finite element model is coupled with an anatomical head finite element model and is evaluated in terms of injury risks (risks of neurological injuries or subdural haematoma) under normative impact conditions (ECE 22.05 standard). Results show that the risk of head injuries is very high even if the considered helmet passes the standard. Thus a second step consists in proposing a new method for improving the helmet behaviour in case of impact by focusing on the outer shell characteristics and by assessing the head injury risk with the human head finite element model. A modal analysis of the entire helmet model is performed and makes it possible to define areas of the outer shell to be modified. Under standard impact conditions this new virtual helmet model conduces to a huge decrease of the head injury risk, both in terms of neurological injuries as well as in terms of subdural haematoma.

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Influence of pedestrian head surrogate and boundary conditions on head injury risk prediction

International Journal of Crashworthiness, 2009

The objective of the present work is to investigate the influence of head models and boundary con... more The objective of the present work is to investigate the influence of head models and boundary conditions on the head response in the case of pedestrian accidents. Simulations have been carried out, regarding results both in terms of global parameters and more detailed intracerebral mechanical parameters. Three head models have been used (ISO headform, Hybrid III head and ULP head

$Research paper thumbnail of Influence of stiffness and shape of contact surface on skull fractures and biomechanical metrics of the human head of different population underlateral impacts$

Influence of stiffness and shape of contact surface on skull fractures and biomechanical metrics of the human head of different population underlateral impacts

Accident; analysis and prevention, Jan 16, 2015

The objective of this study was to determine the responses of 5th-percentile female, and 50th- an... more The objective of this study was to determine the responses of 5th-percentile female, and 50th- and 95th-percentile male human heads during lateral impacts at different velocities and determine the role of the stiffness and shape of the impacting surface on peak forces and derived skull fracture metrics. A state-of-the-art validated finite element (FE) head model was used to study the influence of different population human heads on skull fracture for lateral impacts. The mass of the FE head model was altered to match the adult size dummies. Numerical simulations of lateral head impacts for 45 cases (15 experiments×3 different population human heads) were performed at velocities ranging from 2.4 to 6.5m/s and three impacting conditions (flat and cylindrical 90D; and flat 40D padding). The entire force-time signals from simulations were compared with experimental mean and upper/lower corridors at each velocity, stiffness (40 and 90 durometer) and shapes (flat and cylindrical) of the i...

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[Fatal head trauma of an infant. Part II: Biomechanical reconstruction]

Archiv für Kriminologie

An 18-month-old child was hit on the head by a falling wooden sculpture (c 60 kg) and sustained a... more An 18-month-old child was hit on the head by a falling wooden sculpture (c 60 kg) and sustained a fatal craniocerebral trauma. The kinetics of the trauma could be accurately reconstructed. The child's skull was then modelled using the finite-element-method. The material parameters known from the literature were assigned to the elements. The dynamic reconstruction performed on the basis of the kinetics calculated before was able to reproduce the destruction of the skull and the brain by simulating the impact-related topographical distribution of the intracranial pressure and the von Mises stress field.

Development of head injury risk functions based on real-world accident reconstruction

International Journal of Crashworthiness, 2013

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Development of numerical models for the investigation of motorcyclists accidents

The Finite Element (FE) method was employed to develop and enhance numerical models that can be u... more The Finite Element (FE) method was employed to develop and enhance numerical models that can be used for simulating accidents involving motorcyclists. They are the FE models of a commercial helmet, the human head and the Hybrid III dummy. The composite shell and foam liner of the helmet, which are the most important components in terms of energy absorption, were generated using the Ls-Dyna preprocessing software. The FE model of the human head, which was developed in the Radioss environment, was converted to the Ls-Dyna format. In order to validate the head model with respect to the skull force-deflection response and intracranial pressures, two cadaveric tests reported in literature were simulated. The model of the head was coupled, through the neck, with the body of the Hybrid III dummy. This new dummy was capable of predicting the skull fracture as well as intracranial injuries such as the diffuse axonal injury. As an application of the models, the Hybrid III dummy and the new dummy were equipped with the helmet and dropped onto a flat anvil at the 7.5 m/s impact speed. The protective capability of the helmet was assessed with respect to kinematic injury predictors, such as the maximum linear acceleration of the head, and tissue level injury predictors, such as Von Mises stress in the brain.

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Three-year-old child neck finite element modelization

European Journal of Orthopaedic Surgery & Traumatology, 2006

Despite the recent progresses in occupant safety, protection of children is not still optimal. To... more Despite the recent progresses in occupant safety, protection of children is not still optimal. To offer a better understanding of child injury mechanisms, the present study proposes a human-like finite element model of a 3year-old child neck. The subject underwent scanning. The images were first segmented semi-automatically in order to extract the soft tissues and the bones. In the second step, we separated the different bones slice by slice on the geometry previously reconstructed. The anatomic structures were identified and each vertebra was reconstructed independently with special attention to the articular process. In the third step, we generated an original meshing on the previous geometry to obtain a finite element model of the child's neck. The modelled anatomical structures are the head, the seven cervical vertebrae (C1-C7), the first thoracic vertebra (T1), the intervertebral discs and the principal ligaments which were modelled using non-linear shock-absorbing spring elements. The stiffness values used were taken from the literature, and scaled down using scale factors from Irwin. This model incorporates 7,340 shell elements to model the 8 vertebrae, the head and 1,068 solid 8-node elements to model the intervertebral discs. Contact between the articular surfaces is represented by interfaces permitting frictionless movement. Since this study does not aim to reproduce bone fractures, we have modelled the cervical vertebrae as rigid bodies. Given that validation data was not available, the model validation was conduced against crash test dummy component sled tests. The accelerometric responses of the head model were similar with those recorded experimentally with a Q3 dummy neck in backward, frontal and lateral impact direction.

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A Study of Adult Pedestrian Head Impact Conditions and Injury Risks in Passenger Car Collisions Based on Real-World Accident Data

Traffic Injury Prevention, 2013

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Caroline DECK

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