Dynamic verification of a multi-body computational model of human head and neck for frontal, lateral, and rear impacts

A multi-body computational model of the human head and neck was previously shown to be in good agreement with experimental findings from actual human cervical spine specimens. The model segments were tested in three directions of loading showing main and coupled motions to be accurate and realistic. The model’s ability to predict the dynamic response of the head and neck, when subjected to acceleration pulses representing frontal, lateral, and rear-end impacts, is verified using experimental data derived from sled acceleration tests with human volunteers for 15 g frontal and 7 g lateral impacts and from isolated cervical spine specimen tests for rear-end impacts. Response corridors based on sled acceleration tests with human volunteers for frontal and lateral impacts are used to evaluate the model and investigate the effect of muscle activation on the head– neck motion. Firstly, the impacts are simulated with both passive and active muscle behaviour. Secondly, the local loads in the soft-tissue elements during the frontal impact are analysed. For rear-end impact simulation experiments using ligamentous isolated cervical spine specimens are used to evaluate the model performance before investigating the effects of muscle tensioning. Good agreement with human volunteer response corridors resulting from frontal and lateral impacts, and isolated cervical spine specimen sled test rear-end impact experiments is demonstrated for the model, highlighting the important role the muscles of the neck play in the head–neck response to acceleration impacts. The model is shown to be able to predict the loads and deformations of the cervical spine components making it suitable for injury analysis

A computational model of the human head and neck system for the analysis of whiplash motion

This paper presents the development and validation of a three-dimensional multi-body model of the human head and neck for the study of whiplash motion. The model has been validated against experimental data for small and large static loading conditions. The resulting main and coupled displacements of the individual motion segments have been shown to be accurate and the moment generating capacity of the neck muscle elements realistic. The model has been used for the dynamic simulation of impacts in frontal, lateral and rear-end directions. For rear-end impacts the characteristics of ‘whiplash’ motion have been accurately reproduced in terms of head and vertebral kinematics The model results with active musculature suggest that, for rear-end impact, the influence of active muscle response is unable to significantly alter the head and neck kinematics of an initially unaware occupant but will affect the forces developed in the cervical soft-tissues

Computational pregnant occupant model, 'Expecting', for crash simulations

A computational model of the pregnant occupant, which is capable of simulating the dynamic response to acceleration impacts, is introduced. The occupant model represents a 5th percentile female at around the 38th week of pregnancy. A finite element uterus and multi-body fetus is integrated into an existing female model to incorporate pregnant female anthropometry. The complete model, ‘Expecting’, is used to simulate a range of frontal impacts of increasing severity from 15 km/h to 45 km/h. Three levels of occupant restraint, completely unrestrained, three-point seat belt, and three-point seat belt with an airbag, are investigated. The strains developed in the uterus because of loading from the seat belt and steering-wheel unit are presented, together with an analysis of stress distribution due to inertial loading of the fetus on the uterus. The unrestrained cases are shown to be the most dangerous to the fetus, owing to the large interaction with the vehicle steering wheel at the level of the placenta. The use of a three-point seat belt together with a driver airbag appears to offer the greatest protection to the fetus

Modelling the foetus for pregnant occupant safety

Annual foetus mortality rates due to road traffic accidents are much higher than the infant mortality rates in motor vehicle crashes. The goal of this study is to generate a computational model of the unborn occupant (foetus) for crash protection research. The multibody foetus model is accommodated in the finite element uterus model of 'Expecting', the computational pregnant occupant model which tackles the complexity of a pregnant women's anatomy and incorporates pregnant female anthropometry. In particular, 38 weeks gestation level is focused upon since at this stage of pregnancy the foetus is at greatest risk during a crash due to the size increase of the abdomen resulting in a close proximity to the vehicle steering wheel and awkward routing of the seatbelt. This article explains in detail all stages of modelling the unborn occupant and the links to its environment, the uterus with a placenta and the computational female model

Development of a multi-body computational model of human head and neck

Experimental studies using human volunteers are limited to low acceleration impacts while whole cadavers, isolated cervical spine specimens, and impact dummies do not normally reflect the true human response. Computational modelling offers a cost effective and useful alternative to experimental methods to study the behaviour of the human head and neck and their response to impacts to gain insight into injury mechanisms. This article reports the approach used in the development of a detailed multi-body computational model that reproduces the head and cervical spine of an adult in the upright posture representing the natural lordosis of the neck with mid-sagittal symmetry. The model comprises simplified but accurate representations of the nine rigid bodies representing the head, seven cervical vertebrae of the neck, and the first thoracic vertebra, as well as the soft tissues, i.e. muscles, ligaments, and intervertebral discs. The rigid bodies are interconnected by non-linear viscoelastic intervertebral discs elements in flexion and extension, non-linear viscoelastic ligaments and supported through frictionless facet joints. Eighteen muscle groups and 69 individual muscle segments of the head and neck on each side of the body are also included in the model. Curving the muscle around the vertebrae and soft tissues of the neck during the motion of the neck is also modelled. Simulation is handled by the multi-body dynamic software MSC.visuaNastran4D. Muscle mechanics is handled by an external application, Virtual Muscle, in conjunction with MSC.visuaNastran4D that provides realistic muscle properties. Intervertebral discs are modelled as non-linear viscoelastic material in flexion and extension but represented by‘bushing elements’ inVisualNastran 4D, which allows stiffness and damping properties to be assigned to a joint with required number of degrees of freedom of the motion. Ligaments are modelled as non-linear viscoelastic spring–damper elements. As the model is constructed, the cervical spine motion segments are validated by comparing the segment response to published experimental data on the load–displacement behaviour for both small and large static loads. The response of the entire ligamentous cervical spine model to quasi-static flexion and extension loading is also compared to experimental data to validate the model before the effect of muscle stiffening is included. Moreover the moment-generating capacity of the neck muscle elements has been compared against in vivo experimental data. The main and coupled motions of the model segments are shown to be accurate and realistic, and the whole model is in good agreement with experimental findings fromactualhumancervical spine specimens. It has been shown that the model can predict the loads and deformations of the individual soft-tissue elements making the model suitable for injury analysis. The validation of the muscle elements shows the morphometric values, origins, and insertions selected to be reasonable. The muscles can be activated as required, providing a more realistic representation of the human head and neck. The curved musculature results in a more realistic representation of the change in muscle length during the head and neck motion

ESDA2004-58521 A COMPUTATIONAL MODEL OF THE HUMAN HEAD AND NECK FOR FRONTAL AND LATERAL IMPACTS

ABSTRACT This paper presents the development and validation of a threedimensional computational model of the human head and neck

'Expecting': occupant model incorporating anthropometric details of pregnant women

This study reports the research for a design tool related to pregnant women’s safety during car travel. Anthropometric measurements are taken to generate an occupant model incorporating pregnancy related changes. These anthropometric changes mean that a pregnant occupant may be excluded by the designs, based upon non-pregnant female anthropometry. The paper explains the generation of a comprehensive parametric computer aided model of a pregnant occupant, ‘Expecting’. The model can represent different size pregnant occupants as well as the size differences occurring in standing and seated postures. This model can be used as a design tool for automotive designers to help ensure that vehicle designs can accommodate the anthropometric needs of pregnant occupants