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Objective To predict and assess biomechanical responses and injury mechanisms of the thorax and abdomen for small-sized females in vehicle collisions. Methods The accurate geometric model of the thorax and abdomen was constructed based on CT images of Chinese 5th percentile female volunteers. A thoracic-abdominal finite element model of Chinese 5th percentile female with detailed anatomical structure was developed by using the corresponding software. The model was validated by reconstructing three groups of cadaver experiments (namely, test of blunt anteroposterior impact on the thorax, test of bar anteroposterior impact on the abdomen, test of blunt lateral impact on the chest and abdomen). Results The force-deformation curves and injury biomechanical responses of the organs from the simulations were consistent with the cadaver experiment results, which validated effectiveness of the model. Conclusions The model can be used for studying injury mechanisms of the thorax and abdomen for small-sized female, as well as developing small-sized occupant restraint systems and analyzing the forensic cases, which lays foundation for developing the whole body finite element model of Chinese 5th percentile female.
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Objective To explore the influence of child head injury under different impact angles by applying the finite element model of six-year-old child pedestrian as specified in the European New Car Assessment Programme (Euro NCAP). Methods Based on the finite element model of 6-year-old pedestrian with detailed anatomical structure as specified by the Euro NCAP (TB024), four groups of simulation experiments were set up to explore the mechanism of head injury in children under different impact angles. The initial position for head mass center was on the longitudinal center line of the car. The initial speed of the car was 40 km/h. The car contacted with the model from the direction of the right (0°), the front (90°), the left (180°) and the back (270°). The kinematics differences and head impact responses were compared, and injuries of the facial bone and skull were analyzed. Results Through the analysis of head contact force, acceleration of head mass center, resultant velocity of head mass center with the vehicle, head injury criterion (HIC15), facial bone fracture and skull stress distribution, it was found that the risk of head fracture and brain contusion under back impact and front impact was higher than that under side impact. The risk of head fracture and brain contusion was highest under back impact, while the lowest under side impact. Conclusions Child pedestrian head injury was the largest under back impact. The results have important application values for the assessment and development of car-pedestrian collision protection device.
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Objective To study the influence of skull thickness on intracranial biomechanical parameters by finite element method. Methods The female head at 5th percentile was selected for CT scanning to construct finite element model of the head with high biofidelity,and the model was verified by reconstructed cadaver test. The finite element model of the head with different skull thickness was established, and multiple groups of tests were carried out to compare the intracranial mechanical parameters. Results The negative value of intracranial pressure was significantly affected by the decrease in skull thickness under the same head size, while the negative value of intracranial pressure was slightly affected, with an increasing trend. The shear stress and von Mises stress of brain tissues were significantly increased with skull thickness increasing. Conclusions Under the same head size, the skull thickness will affect head injury to a certain extent, and people with small skull thickness are more likely to be injured than those with large skull thickness.
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Objective To explore the effect of restraint system misuse on head-neck injuries for rear occupant of 6-year-old children in frontal impact crashes. Methods Based on the previously validated 6-year-old child occupant finite element model, in terms of ECE R44 testing regulations, the impact crash under right and wrong use of restraint system was simulated in Pam-Crash software. Results The force and moment of the neck were the minimum by merely using booster seat, but the maximum intracranial pressure, the maximum stress and the maximum principal strain were larger than their damage threshold and would cause fatal brain damage in child head. The only use of adult safety belt would cause more serious damage in child neck with larger force and moment. Conclusions Two ways of misusing the restraint system would aggravate head-neck injuries of the 6-year-old child. The proper use of the restraint system can provide the best protective effect for head and neck of the 6-year-old child occupant.
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Objective To study the effect of neck restrain on traumatic brain injury during airbag inflation in traffic accidents. Methods Based on the previously validated 3-year-old child head finite element (FE) model, the impact on out-of-position (OOP) child occupant during airbag inflation was simulated by FE method, so as to investigate the effects of neck restraint on intracranial response and injury mechanism in traffic accidents. Results The head kinematics with neck restrain was different from that without neck restrain under the impact of airbag inflation. The neck restraint would obviously decrease the maximum Von Mises stress of pediatric brain. When airbag-head distance was 20 cm or 25 cm, the neck restraint would obviously decrease the maximum intracranial pressure. Conclusions Neck restraint had a relatively large influence on pediatric intracranial response. When the FE method is used to predict pediatric craniocerebral injury, consideration of neck restrain on child brain response is necessary.
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Objective To explore the effects of different skull-brain interfaces and mesh density of the cerebrospinal fluid (CSF) on dynamic responses of the brain. Methods The impact kinematics on cadaver head under rotation and translation impacts were reconstructed based on the 50th percentile adult head finite element model. The interfaces between skull and CSF, CSF and brain were modeled with different types of interfaces, which were set as sharing nodes, tied, frictionless sliding, so as to investigate the effect of different interface types on dynamic responses of the brain. Then, the interfaces between CSF, skull and brain were set as sharing nodes, while CSF was divided into single-layer and tri-layer of hexahedral element with the constant thickness of CSF, to study influences of CSF with different mesh density layers on dynamic responses of the brain. Results The intracranial pressure was highly sensitive to the interface types, while the brain response seemed to be relatively insensitive to the variation in CSF layers. Conclusions The research findings provide theoretical references for the construction of CSF and the selection of skull-brain contact interface of the head finite element model.
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Modern vehicle safety design and safety regulations are mostly based on 50th percentile populations. However, with the increase of obese populations, it is very important to investigate the injury mechanism and protection of obese occupant. Methods such as traffic accidents statistics, cadaver experiments, multi-body modeling and finite element modeling, are currently used to study the injury mechanism of obese occupants. Different hypotheses including cushion effect, body geometrical effect and mass increasing effect have been put forward to explain the effect of obesity on occupant injury mechanism, which means that its mechanism is still uncertain. The impact injury mechanisms of obese occupant were comprehensively summarized. Furthermore, the problems confronted by the research of current obese occupant impact injury and future investigations were proposed in this study.
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Objective To compare and analyze the effect of membrane element and spring element on biomechanical responses of cervical ligaments. Methods Based on the existing 6-year-old pediatric neck finite element model, the ligaments were simulated by membrane element and spring element, respectively. Then dynamic tensile test of C4-5 vertebrae and tensile test of full cervical spine were conducted. The membrane element model was also used to simulate the bending test, and the simulation results were analyzed. Results In dynamic tensile test of C4-5 vertebral segment, the final failure force of membrane element simulation test and spring element simulation test was 1 207 N and 842 N, respectively, and their difference from the cadaver experiment was 0.6% and 30.6%, respectively. In full cervical tensile test, the difference of peak force from membrane element simulation test and cadaver experiment was 1.8%. The peak force of spring element simulation test was 484 N, and the difference from simulation test and cadaver experiment was large. The simulation result of membrane element bending test was good. Conclusions The spring element had some limitations in force simulation. The membrane element had higher biofidelity and could reflect the biomechanical response of the ligaments.
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The pediatric cadaver impact experiments were reconstructed using the validated finite element(FE) models of the 3-year-old and 6-year-old children. The effect of parameters, such as hammer size, material parameters and thorax anatomical structure characteristics, on the impact mechanical responses of 3-year-old and 6-year-old pediatric thorax was discussed by designing reasonable finite element simulation experiments. The research results showed that the variation of thorax contact peak force for 3-year-old group was far larger than that of 6-year-old group when the child was impacted by hammers with different size, which meant that 3-year-old child was more sensitive to hammer size. The mechanical properties of thoracic organs had little influence on the thorax injury because of the small difference between 3-year-old and 6-year-old child in this research. During the impact, rib deformation led to different impact location and deformation of internal organs because the 3-year-old and 6-year-old children had different geometrical anatomical structures, such as different size of internal organs. Therefore, the injury of internal organs in the two groups was obviously different. It is of great significance to develop children finite element models with high biofidelity according to its real anatomical structures.
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Objective To develop the finite element model of six-year-old child occupant lower extremity with higher biofidelity and validate the model of knee joints,as well as analyze the biomechanical responses of growth plate under frontal impact load and injury mechanisms of the knee joint by using this model.Methods The sixyear-old child occupant lower extremity with growth plate was modeled based on children's anatomy and CT images,and corresponding material properties of the lower extremity model were assigned.The model was validated according to biomechanical experiments by Kerrigan et aL and Haut et aL and then was used to analyze the injury results of growth plate with different material properties.Results The model validation was qualified by comparing the curves from the experimental and simulation results.The growth plates at knee regions could change injury patterns of the child occupant lower extremity fracture.The material properties of growth plate could affect threshold of axial damage of the femur as well as relative position of the fracture.Conclusions The validated model can be used for related study and application on biomechanical responses and injury mechanisms of sixyear-old child occupant lower extremities.
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The pelvis is one of the most likely affected areas of the human body in case of side impact, especially while people suffer from motor vehicle crashes. With the investigation of pelvis injury on side impact, the injury biomechanical behavior of pelvis can be found, and the data can help design the vehicle security devices to keep the safety of the occupants. In this study, a finite element (FE) model of an isolated human pelvis was used to study the pelvic dynamic response under different side impact conditions. Fracture threshold was established by applying lateral loads of 1000, 2000, 3000, 4000 and 5000 N, respectively, to the articular surface of the right acetabulum. It was observed that the smaller the lateral loads were, the smaller the von Mises stress and the displacement in the direction of impact were. It was also found that the failure threshold load was near 3000 N, based on the fact that the peak stress would not exceed the average compressive strength of the cortical bone. It could well be concluded that with better design of car-door and hip-pad so that the side impact force was brought down to 3000 N or lower, the pelvis would not be injured.
Subject(s)
Humans , Accidents, Traffic , Biomechanical Phenomena , Computer Simulation , Finite Element Analysis , Fractures, Bone , Pelvis , Wounds and Injuries , Stress, MechanicalABSTRACT
BACKGROUND:Mechanical experiment of finite element numerical simulation is the effective method to research the biomechanical structure of human body. OBJECTIVE:To establish the three-dimensional finite element model of a normal 6-year-old child’s humerus. METHODS:CT images of a 6-year-old child volunteer were imported to the Mimics 10.01 software. The threshold segmentation method was used to rebuild the humerus three-dimensional model. The surface optimization treatment and surface patches dicision were performed on the surface of the model with Geomagic Studio 12.0 software. Then the mesh generation was completed in the software TrueGrid. Final y, the material properties were set and the finite element model was completed. The boundary conditions and constrains were exerted to simulate the three-point-bending test of humeurs. After the simulation, the results were outputted. RESULTS AND CONCLUSION:The humerus finite element model included 3 024 nodes and 18 758 nodes-hexahedron elements. The 0.01 m/s and 3 m/s dynamic loads were loaded respectively, then the central humerus fracture occurred and the load-displacement curve was close to the cadaver test results. The simulation results show that the simulation results of children humerus finite element model are close to the cadaver’s test, and the finite element simulation method can simulate the physical properties of the human skeleton very wel .
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A validated 5th and 95th percentile Chinese head model was used to investigate the influence of head dimensions on the biomechanical responses by comparing acceleration, intracranial pressure and shear stress of the heads with different dimensions under the same impact energy. Moreover, the reasonability of scaling method used in the research considering head dimensions was discussed by respectively scaling the small head to a big one and scaling the big head to a small one. It therefore more scientifically provides a newer and more scientific reference for the assessment of head injury.
Subject(s)
Humans , Anthropometry , Asian People , Biomechanical Phenomena , Brain Injuries , Craniocerebral Trauma , Finite Element Analysis , Head , Models, AnatomicABSTRACT
Based on the biomechanical response of human knee joint to a front impact in occupants accidents, a finite element (FE) model of human knee joint was developed by using computer simulation technique for impacting. The model consists of human anatomical structure, including femoral condyle, tibia condyle, fibular small head, patellar, cartilage, meniscus and primary ligament. By comparing the results of the FE model with experiments of the knee joint in axial load conditions, the validation of the model was verified. Furthermore, this study provides data for the mechanical of human knee joint injury, and is helpful for the design and optimization of the vehicle protective devices.
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Humans , Biomechanical Phenomena , Finite Element Analysis , Knee Injuries , Knee Joint , Physiology , Models, Anatomic , Models, BiologicalABSTRACT
Two kinds of algorithm have been set forth to estimate the symmetry characteristic of live human skull on CT image. These CT images were treated with a series of processes such as coding into programs, formatting originals, binary coding, rectifying image deviation, detecting boundary edge, and quantitatively measuring the skull symmetry. The statistical analyses of measuring 3000 live human skull images have worked out the ratio and the distribution of the skull symmetry, so that dependable data are provided for establishing the human head injury biomechanics model. The results are of great practical value in the fields of anatomy, clinical medicine, biomechanies study, head injury analysis, etc.
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Female , Humans , Male , Biomechanical Phenomena , Cephalometry , Methods , Image Processing, Computer-Assisted , Methods , Reference Values , Skull , Diagnostic Imaging , Tomography, X-Ray ComputedABSTRACT
Head injury criterion (HIC) is a widely accepted injury criterion in assessing the injury potential of the human head under external loads. It has been used in vehicle safety regulations worldwide and helmet design. However, controversy about its applicability exists. In this study, two human head models of different size and mass were created to explore the applicability of HIC. Under three different impact loadings, the principal stresses of the two brains of the two different head models were calculated and compared with the corresponding HIC values. The influences on the application of HIC in head injury assessment were investigated. This study provides some new insights and leads new conclusions towards human head injury assessment.
Subject(s)
Humans , Accidents, Traffic , Craniocerebral Trauma , Diagnosis , Finite Element Analysis , Injury Severity Score , Models, Biological , Reference StandardsABSTRACT
This study sought to measure accurately the thickness of the frontal, parietal and occipital bones of the alive human skull based on CT images. The images were treated with a series of processes by coding into a program: image segmentation and binary coding; eliminating edge interference; rectifying image deviation and clarifying boundary edge; redrawing the boundary and reference point fixing; and finally thickness measurement. The new method can measure not only the different points in one CT image but also the same point in massive CT images. The measurement results are of great practical value in the fields of anatomy, clinical medicine, biomechanics study, head injury analysis, etc.