Projects / Programmes
Modelling of anatomical structures for analysis of occupant loads and injuries in traffic accidents
| Code |
Science |
Field |
Subfield |
| 2.11.02 |
Engineering sciences and technologies |
Mechanical design |
Special constructions know-how |
| Code |
Science |
Field |
| B115 |
Biomedical sciences |
Biomechanics, cybernetics |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
biomechanics, mechanical engineering, medicine, modelling, traffic accident analysis, injury, tissue, simulation, multibody system dynamics, finite element method, sled test, tesnile test
Researchers (13)
Organisations (3)
Abstract
The proposed project is a continuation of a previous project entitled »Modelling of anatomic structures for the analysis of loads and injuries to traffic accident participants (code ARRS: J2-9536)«.
The research team has thus far successfully developed a human-body model based on the multibody dynamics theory (MBS), whereby all modelling procedures were effectively included.
For detailed analyses of traffic loads and injuries, the research group has developed a finite element (FEM) model of the neck for coupled FEM-multibody analyses. The FEM model provides a localized description of the stress-strain state of tissues for various load cases which occur upon impact.
A review of the literature and the research team’s own research findings proved inconsistency and unreliability of the available data on mechanical properties of soft tissues. There is a lack of research on the effects of the tissue strain rate and preparation of tissue samples on measured mechanical properties. Furthermore, there are no standard procedures to help determine them. There are significant discrepancies among studies related to the isolation and storage of samples, the size of samples, preconditioning and measuring technique.
The project focuses on the modelling of anatomical structures which affect motion and loads, especially those of the neck, and may be subject to injuries under impact conditions.
Tensile tests of the cervical spine soft tissues shall be performed to determine the parameters of material properties based on the measured stress-strain curve. The analysis shall also include the impact of the strain rate and donor’s age on the behaviour of soft tissues. The tests shall be performed on a purpose-built test device and under physiological conditions.
For the selected soft tissues, a constitutive model for the description of the injury occurrence and damage shall be developed. The methods and knowledge from similar technical research which the group has thus far performed shall be implemented in the development. The determined mechanical properties of the selected soft tissues shall be included in the own-developed FEM model of the neck. The neck model with the upper torso and the head shall enable the scaling of the tissue geometry and material properties, which shall further serve for the model adaptation to individual human properties, such as the body type, age and gender.
For the verification of the FEM model of the neck, sled tests shall be performed on the sled test device. Sled tests shall be performed for representative types of body constitution with direction and impact intensity variations.
An upgrade shall be made of the independent application for analysis of the occurrence and unfolding of traffic accidents with the purpose of improving the integration of the human body model. Up-to-date research results show that the simulation environment efficiently supports fundamental research as part of the research activities while taking account of specific requirements occurring during the modelling of anatomical structures.
The research group consists of experts in various technical and medicine fields from the University of Ljubljana, Institute of Metals and Technology and Vehicle Safety Institute (TU Graz). The partners are closely connected to industry and have extensive experience in basic and applied projects.
By the research team’s estimation, realization of the proposed contents of the project shall contribute to the enhancement and also spreading of knowledge on traffic and other accident injuries. The cost to society of those killed or injured in traffic accidents is extremely high, as traffic accidents are by far the most frequent cause of death and disability among the young and active population. High costs are additionally generated by the long-lasting rehabilitation of injured people, slow judicial procedures and high insurance claims.
Significance for science
The project remarkedly contributed to improvement of the knowledge and understanding of soft tissue mechanical properties. The research was focused on experimental characterisation, as well as numerical modelling of anatomical structures exposed to mechanical loading, in particular under vehicle collision conditions. Cervical spine ligaments have an important role in providing spinal cord stability and restricting excessive movements of the head-neck complex. The cervical ligaments are likely to be injured in rear impacts even at low velocity, as well as frontal and side impacts. Our study is among ten existing where isolated specimens of cervical ligaments were used. Human cervical spine ligaments have a non-linear, strain rate, temperature and an age-dependent response. Since no standardized experimental procedure is available, the existing studies provided data that is difficult to compare with respect to the ligament mechanical properties under various loading conditions. Our study complements the available experimental data on three main cervical stabilizing ligaments (ALL, PLL, LF). Uni-axial tensile tests on a total of 46 specimens were performed on a custom designed test device, under physiological conditions. The mean failure load and linear stiffness increased with the loading rate in ALL and PLL. However, no significant effect of strain rate was found for LF, which has the highest elastin-to-collagen ratio. Compared to other studies, failure forces were up to 2 times smaller for LF and PLL. Most of the existing studies used specimens acquired from elders, despite proven age-related changes of the soft tissue mechanical response. Within the theory of hyperelasticity, recent improvements incorporate damage region of the soft tissue response, along with the well modelled toe and linear regions. In addition, our study provided experimental data for the tissue model parameters and assessed the proposed damage models for modelling cervical the spine ligaments response. Based on analysis of three age groups ((40, 40–60,)60), an age-related decrease in the failure load, failure elongation, and stiffness was observed for all three ligaments. Our study estimated a similar age effect as reported previously for ALL, while the failure properties decreased significantly less for LF. Due to the highly controlled specimen testing, considering the relevant factors, our study gives a better insight into mechanical properties of the cervical spine ligaments. It provides valuable data for tissue level modelling of cervical spine dynamics and injury and opens the possibility for subject-specific modelling. Cervical spine ligament stiffnessand passive muscle response affect the head-neck complex motion and injury probability, particlarly in low-severety rear impacts. Within the framework of the project, the detailed FE neck model of a 50-percentile male was developed, which includes anatomical structures that affect the dynamic response (16 neck muscle pairs, 4 groups of neck ligaments, intervertebral discs, cartilage and facet joints).The model was validated against post mortem sled tests for EuroNCAP whiplash pulse (low, medium, high). Our research provided experimental data on whiplash kinematics of the cervical spine for occupant out-of-position postures. The stress-strain analysis included ALL, PLL, LF, CL between vertebrae with respect to the S-curvature level of the neck. The CL strain observed was within the sub-failure region, indicating an increased injury risk for the head-torso lean position. The analysis confirmed clinical findings and hypothesis that the CL injury is a potential source of whiplash associated disorders. Our research enables an experimentally validated insight into stress and strain of the affected neck anatomical structures in vehicle collision conditions. The results of numerical analyses and experimental testing represent valuable data for improvements of vehicle active and passive safety systems.
Significance for the country
The project forms part of the extensive and long-term efforts aimed at a gradual improvement of traffic safety. Efforts at EU level are reflected in significant reduction in road fatalities from 70.000 (in 1992) to 26.000 (in 2015). However, negative effects to society are still substantial and are estimated at €100 billion. In Slovenia, traffic safety is slightly below average. In 2015, there were 58 fatalities per million population, while in EU the number was 51.5, with comparable social and economic burden of traffic accidents. High-level fundamental knowledge in the field of numerical modelling enables the research team to cooperate with industrial companies (SMM, Gorenje, ST Ravne). We attach great importance to cooperation with small-scale innovative high-tech companies with high growth potential (TMG-BMC). The project content is closely linked to the safety of road infrastructure and its use. The research team activity is also aimed at providing support to DRSC and DARS initiatives in the field of traffic safety as well as improvement of safety barriers and development of tunnel niches. The proposed project is good promotion of Slovenia. The FME team members and the members of the Austrian TU Graz were invited to join the international consortium for a project within the Horizon 2020 funding programme (MG-3.2-2017, Protection of all road users) which consists of 11 partners from 6 European countries and is under the guidance of a prominent institute VTI (Sweden). This is great recognition for the project team researchers and acknowledgement of the topicality of the research as well as the correctness of the decision made by ARRS and the Austrian FWF to support the project. The project results and obtained equipment have further enhanced international cooperation with the University of Rijeka (Cro) and enabled achievement of Partner status in bilateral project Development of evolutionary procedures for characterization of biological tissues behavior (BIOMAT, project No. - IP-2014-09-4982 Croatian Science Foundation). The objectives of the bilateral project include expanding the use of the material characterization methodology applied in engineering sciences to the field of soft tissue and biomaterials for use in medicine. For the duration of the project, the first round of students has already concluded the Master's interdisciplinary study programme Traffic Safety Systems of the FEM, University of Ljubljana. The study programme covers the fields of biomechanics, forensic medicine, complex numerical simulations, vehicle safety and traffic accident analysis. It is our estimate that the project content has significantly contributed to the study programme quality since some of the project promoters are also members of the research team. The project is of great importance to the education of staff in development departments of the automotive industry and its suppliers, logistics, insurance business, companies for road infrastructure design and management as well as relevant state administrations. The project findings enable more efficient and reliable analysis of traffic accidents in which the project team members also actively participate as court-appointed experts in the fields of road traffic and medicine. Their assistance in the investigation of the most severe cases of traffic accidents is regularly requested by the Slovenian Police and the Slovenian Traffic Safety Agency. Presentation of their results to the professional public contributes to the development of the insurance business and improves the judicial system efficiency. It is our estimate that the project will enable quality and technological advancement in the field of traffic safety in Slovenia and promote integration of the Slovenian expert public into current global affairs.
Most important scientific results
Annual report
2013,
2014,
2015,
final report
Most important socioeconomically and culturally relevant results
Annual report
2013,
2014,
2015,
final report
