P. Drazetic

Experimental study of the bone behaviour of the human skull bone for the development of a physical head model

Abstract The first part of this work aims to develop an experimental protocol in order to identify the monolayer behaviour of the skull (cortical and spongy bones in the model are represented by a single homogeneous layer). Experimental tests on 20 skulls from unembalmed cadavers have been performed by the LAMIH and the CEESAR. Nineteen specimens were taken from each of the human skulls following a very precise cartography (five frontal, eight parietal, two temporal, one occipital, two on the coronal suture and one on the sagittal suture). Three hundred and eighty specimens were tested in three-point bending test. In the second part, a physical head model was developed. A reference model was realized by using stereolithography method. The main point was to find a resin whose characteristics are similar to human skull bone. Then, this prototype was validated by means of experimental tests similar to Nahum et al. (test in 6 m/s by means of a cylindrical impactor of 6-kg mass).

Analysis of train driver protection in rail collisions: Part I. Evaluation of injury outcome for train driver in desk impact

This two-part paper described the results of the research programme PROCAB for train driver protection during rail collisions. In Part I, a methodology was proposed to analyse driver survivability in train crash. Appropriate experimental devices and associated numerical models were developed which were able to reproduce the loads and accelerations imparted to the train driver and on the interior elements of the drivers cabin. A full validation programme was realised involving correlation between experimental methods and computer model outputs. Experiments and computer results indicated that during a collision, the driver was likely to strike the desk at the lower chest. Since actual desk was extremely rigid due to maintenance requirements, chest deflection exceeded human tolerance. Part II deals with the development of an interior driver protection.

Analysis of train driver protection in rail collisions: Part II. Design of a desk with improved crashworthiness performance

This two-part paper described the results of the research programme PROCAB (French acronym for PROtection CABine) for train driver protection in rail collisions. In the part I, virtual and physical testing were developed to predict the train driver dynamics and related injuries due to secondary impact with cabin furniture. The conclusion was that the desk represented a hostile secondary impact environment for the locomotive engineer by inducing severe thoracic injuries. Part II included the design, fabrication and testing of an improved command desk. The concept selected was a movable rigid desk with energy-absorbing aluminium honeycomb to slow the desk motion, coupled with knee bolsters. A prototype of the protection device was fabricated and evaluated in a dynamical sled test under a 5 g, 0.1 s deceleration pulse. Preliminary results demonstrated the effectiveness of this concept in reducing the thoracic injury risk without increasing risk in another area (head, neck, chest, femurs and tibias).

Experimental and numerical studies of fluid-structure interaction phenomena inside the head when subjected to a dynamical loading

Brain injury constitutes one of the major causes of death in road accidents. Finite element (FE) models are commonly used to investigate the biomechanics of head impact since they enable an enhance...

Multiscale modelling of the mechanical behaviour of human humerus under impact

Density, structural anisotropy and mechanical strength are important features when evaluating and describing bone tissues. Many theories on bone material have attempted to predict the quasi-static failure of bones, but very few have attempted to study the fracture behaviour of long bones under impact. To estimate fracture and plan a preventive intervention, the strength of the humerus must be precisely quantified (Duprey et al. 2007a, 2007b). To this end, micromechanical approaches combined with CT-based finite element (FE) models have been proved to be more appropriate when the robustness of computation and accuracy of results are of interest. The aim of this study was to propose a consistent multiscale approach for the accurate characterisation and modelling of mechanical behaviour of the human humerus under impact. The present micromechanical model (Rahmoun et al. 2009) is based on the combination of the Mori–Tanaka homogenisation scheme (Mori and Tanaka 1973) for the estimation of elastic properties of the humerus bone and a 3D hexahedral FE model at the macro-level for the prediction of the global response of the humerus.

Multi-scale modelling of the trabecular bone elastoplastic behaviour under compression loading

We propose a new elastoplastic damage coupled model for the modelling of trabecular bone behaviour. The damage is carried out thanks to the limit analysis based on the MCK criterion. We first present the methodology allowing the estimation of elastic anisotropic properties of porous media by means of Mori–Tanaka homogenisation scheme. Then, we present the formulation of the integrated yield criterion derived by considering trial velocity field inspired from the Eshelby inhomogeneous inclusion solution. The obtained micromechanical model is implemented via a UMAT routine within the explicit dynamic code LS-DYNA. The proposed micromechanical model has been applied successfully for the modelling of some biomechanics applications to estimate the mechanical properties of the bovine trabecular bone.

Epidemiological study applied to the design of wrist guard

The number of sports injuries was estimated at more than 900,000 in France in 2004 (Réseau Epac, Ricard 2004– 2005). A comparative study of injuries in sports led us to focus on wrist injury in rollerblading and snowboarding (Calle and Eaton 1993; Schieber 1996). Around 31,000 snowboarders were hurt in France in 2010–2011, and 55% of injured teenagers had a wrist fracture (Association des médecins de montagne 2011). Studies described kinematics of snowboarders’ falls (Idzikowski and Janes 2000). The efficiency of wrist guards was investigated by several studies (Ronning et al. 2001; Fulham O’Neill 2003; Hagel and Barry Pless, n.d.); the conclusions of these studies were controversial. There is neither recent information about the use of wrist guard in France nor description of wrist guard. The objectives of this study were to complete and update statistical data of snowboarders and rollerbladers injuries: association of injury with the protective equipement worn, description of the kinematics of falls and protective equipment. Another objective was to define whether injuries lead to stop the practice.

Analysis of train driver protection in rail collisions.

The goal of the PROCAB research program is the reduction of the number of fatalities and serious injuries suffered by train drivers in railway accidents through improved design of cabin structures. In this paper, the authors perform a biomechanical study of the train driver in a current driving cab design configuration, with the goal of optimizing the cab interior for driver protection in a frontal rail collision. They conducted virtual and physical tests to determine train driver dynamics and related injuries due to secondary impact with the cabin’s furniture. After results showed that sudden deceleration of the cab car caused the driver to launch towards the desk, an improved desk was developed. This improved desk resulted in fewer thoracic injuries.

Evaluation of wrist guard effectiveness for snowboarders.

Snowboarding is one of the sports with the highest rate of wrist injuries. In this context, this study focused on wrist protection for snowboarders in 2011–2012 in France (Thoraval et al. 2012). It revealed that around 16% of snowboarders who were surveyed in front of the ski-lift in 2011–2012 wore a wrist guard. Furthermore, an important variety of wrist guard designs were observed. Actually, no standard impact test was required for snowboarder wrist guards. In contrast, a standard performance test existed for roller protective gear (NF EN14120). It consisted of a drop test on the protection with impact energy ranging from 3 to 5 J (performance level suitable for roller sports except acrobatic practice). The protection was maintained on a spherical-shape anvil. For each protection, six impacts were performed on the palm area. For each impact, the maximum force transmitted through the protection was analysed. A protection complied with the standard if the mean value of the six recorded force peaks did not exceed 3000N. Nevertheless, this standard test for roller wrist guard presented some limitations for snowboard. First, the impact energy was not representative of snowboarder falls. Simulated falls revealed an impact energy ranging from 13.5 to 22.5 J for snowboarders (Schmitt et al. 2009). Second, the transmitted load corresponded to a global deformation of the protection. As wrist injuries depend on the distribution of force to the palm surface and underlying bones (Choi et al. 2011), it was important to access realistic local stress repartition data on the palm through the protection. The objective of this study was to propose a new test to evaluate snowboarder protection performance. This was completed in two steps. First, drop testswere conducted on a wrist protection fitted on an anthropomorphic physical forearm model. The maximum load transmitted was compared to the roller standard test. Second, physical tests were simulated within pamcrashw, and correlation between experiments and numerical simulations was realised. 2. Methods

Comparison of geometrical models of cranial bone samples for the identification of an apparent elastic modulus

of an apparent elastic modulus F. Vandenbulcke*, K. Bruyere, C. Masson, R. Delille, D. Lesueur and P. Drazetic LAMIH University of Lille Nord de France, Lille, France; UVHC-LAMIH CNRS-UMR 8201, F-59313 Valenciennes, France; Université de Lyon, F-69622 Lyon, France; IFSTTAR, LBMC, UMR_T9406, F-69675 Bron, France; Université Lyon 1, Villeurbanne, France; Aix-Marseille Université, IFSTTAR, LBA, F-13916 Marseille, France; Université de la Méditerranée-Aix-Marseille, LBA, F-13916 Marseille, France