Human FE Model Research Articles

A novel dynamic mechanical analysis device to measure the in-vivo material properties of plantar soft tissue and primary finite elementary analysis results

We have designed a series of dynamic mechanical analysis (DMA)-like device to directly measure the material properties of living human plantar soft tissue. Various mechanical tests of plantar soft tissue such as vertical, horizontal shear and torsion can be carried out on the newly invented instruments, and periodic strain-stress outputs are obtained to analyse the viscoelasticity of the tissue. Pioneering finite element analysis has been done by coupling the machine and human foot FE model from different simulation environments, and the simulation tests show good engineering verification of the device design, and consistent theoretical results of the material properties of plantar soft tissue as expected.

Correlation between kinematics and biomechanics of helmeted head under different impact conditions

Helmet is the most common and effective means to avoid severe injuries of human head in accidents. Nonetheless, the helmet may not completely protect the head and head injuries can still happen under impacts. To improve the protectability of helmets, this study aims to systematically investigate the impact characteristics (e.g., helmet structural behaviours, head kinematics and biomechanical responses) of a helmeted head under different impact conditions (e.g., anvil shape, impact site, impact velocity and impact angle). The helmeted head model was developed by a representative motorcycle helmet model coupled with a human head FE model, then validated through four helmet experiments under standard drop impact tests. Based upon the validated models, virtual drop impacts were performed on the helmeted head models to explore the helmet impact characteristics and head responses. A parametric study was carried out to investigate the effects of impact conditions on helmeted head responses; correlation analysis was also conducted to understand the relationships between head kinematics and biomechanical responses. It is shown that the impact conditions can significantly influence the helmet protectability and head responses; and the protectability of helmet can be improved by prolonging the compression stage to weaken head impact responses. According to the strong linear relationships between head kinematics and biomechanical responses established, three correlation equations were proposed to predict the head biomechanical responses through the given impact kinematics. This study is anticipated to advance the knowledge on the helmeted head responses under different impact conditions, thereby gaining new insight into the correlation between head impact kinematics and biomechanics, thereby providing technical guidance to the design for helmet protection.

Validation of a finite element model of the thoracolumbar spine to study instrumentation level variations in early onset scoliosis correction

Growth-guidance constructs are an alternative to growing rods for the surgical treatment of early onset scoliosis (EOS). Constructs containing ultra-high molecular weight polyethylene (UHMWPE) sublaminar tape have been proposed as an improvement to the traditional Luque trolley. Ideally, a certain minimum number of levels is instrumented, thus offering the best balance between providing adequate spinal fixation and minimizing surgical exposure and spinal mobility reduction. The objective of the current study was to validate a parametric FE model of the thoracolumbar spine including its ability to predict the biomechanical effects of varying the number of levels instrumented with UHMWPE sublaminar tape in a growth-guidance construct for EOS correction.In a first step, the material properties of the L4-L5 segment in the model were calibrated relative to literature data. Next, whole thoracolumbar spine behavior was verified relative to literature data as well. Subsequently, rods, screws, and sublaminar tape were implemented in the model and a simulation of a previously performed in vitro experiment, in which the range of motion (ROM) of porcine spine segments was measured for different tape configurations, was performed.Good agreement between in vitro and FE-results was found for the changes in ROM before and after instrumentation. Good agreement for changes in ROM was obtained when varying the number of instrumented levels as well, indicating that the model can be a useful tool to evaluate the effects of construct composition variations. The present study was limited by the fact that only normal spine curvatures were analyzed and the fact that results of porcine spine experiments were compared to results of human FE models. Nevertheless, the good agreement in results, even at a detailed level, supports the idea that the model can ultimately be used as a pre-operative planning tool to evaluate different construct designs. The FE model of the thoracolumbar spine was successfully validated and was able to capture the biomechanical effect of construct component variations.

Evaluation of Brain Injury for Child Pedestrian Using 6YO Human FE Model and Dummy

Evaluation of Brain Injury for Child Pedestrian Using 6YO Human FE Model and Dummy

Investigation of dynamic deformation of the midbrain in rear-end collision using human brain FE model

Mild traumatic brain injury (TBI), including concussions, can cause symptoms affecting physical or cognitive domains in the acute and chronic phases. In this study, we investigated the dynamic deformation of the brain stem, which might be important for these symptoms, using a human brain finite element model through reconstruction simulations of rear-end collisions in three different velocities. In all simulations, high maximum principal strain values were observed at the midbrain that were higher than those in the corpus callosum. These findings could provide some mechanical insights into brain disorders associated with mild TBI.

Experimental and Numerical Studies on Vibration Modes and Transcranial Attenuation Characteristics in Unilateral Bone Conduction Hearing

Bone conduction (BC) hearing devices have been used to improve hearing in patients with unilateral conductive hearing loss; however, the clinical results of improvement in the sound localization ability are still controversial. Transcranial transmission in BC may be an important factor affecting sound localization abilities. Transcranial or interaural attenuation, derived from energy attenuation during the BC process, is determined by the different transfer functions of multiple pathways and affected by the whole-head vibration modes. The purpose of this study is to analyze the frequency dependence of BC vibration modes of the whole head, the contribution of middle and inner ear pathways to BC hearing, and the relationship between transcranial attenuation results by dynamics measurement and hearing thresholds. Experimental studies of vibration modes and transcranial attenuation characteristics in BC are performed using scanning laser Doppler vibrometry (LDV) measurements on human cadaver heads. Differences in vibration modes between the excitation and contralateral sides are observed. Additionally, a multiscale human whole-head FE model, including the skull, bony outer ear, ossicular chains, and bony inner ear structures, is proposed to study the mechanism of BC in the human hearing system. After verifying the rationality of the FE model using mechanical impedance and frequency response data, the transcranial attenuation on the temporal bone surfaces and the middle ear structure is calculated in the FE model. Moreover, the vibration characteristics of bilateral ossicular chains and the cochlear bony wall are observed in the whole-head FM model to study their contributions to BC hearing. By analyzing the experimental and numerical results of the vibration modes and the frequency response of the whole head incorporating the ossicular chain and cochlear bony wall, the intrinsic relationship between the results of transcranial attenuation by 1D LDV, 3D LDV, and hearing threshold measurements is further investigated.

Could an isolated human body lower limb model predict leg biomechanical response of Chinese pedestrians in vehicle collisions?

The purpose of the current study was to investigate whether an isolated human body lower limb FE model could predict leg kinematics and biomechanical response of a full body Chinese pedestrian model in vehicle collisions. A human body lower limb FE model representing midsize Chinese adult male anthropometry was employed with different upper body weight attachments being evaluated by comparing the predictions to those of a full body pedestrian model in vehicle-to-pedestrian collisions considering different front-end shapes. The results indicate that upper body mass has a significant influence on pedestrian lower limb injury risk, the effect varies from vehicle front-end shape and is more remarkable to the femur and knee ligaments than to the tibia. In particular, the upper body mass can generally increase femur and knee ligaments injury risk, but has no obvious effect on the injury risk of tibia. The results also show that a higher attached buttock mass is needed for isolated pedestrian lower limb model for impacts with vehicles of higher bonnet leading edge. The findings of this study may suggest that it is necessary to consider vehicle shape variation in assessment of vehicle pedestrian protection performance and leg-form impactors with adaptive upper body mass should be used for vehicles with different front-end shapes, and the use of regional leg-form impactor modeling the local anthropometry to evaluate the actual lower limb injury of pedestrians in different countries and regions.

Improvement in determining the risk of damage to the human lumbar functional spinal unit considering age, height, weight and sex using a combination of FEM and RSM.

Human functional spinal unit (FSU) is comprised of two adjacent vertebrae, the intervertebral disc (IVD), the cartilage endplates and the connecting ligamentous tissues. As humans age, trabecular, cortical bone and IVD change in mechanical properties. These changes influence the movement of the FSU (displacements, rotations and disc bulges). This paper proposes a method to determine the influence of sex, age, weight and height on the movements of the FSU using a combination of the FEM and RSM. The work concentrates on the medium-sized human FSU (L3-L4 lumbar level with standard dimensions of IVD: width = 50mm, depth = 35mm and height = 11mm). Also, the proposed method could be an improvement to the determination of risk of damage based on body mass index (BMI), as well as an alternative method of searching for a healthy weight. The method was developed as follows: First, a three-dimensional parameterized human healthy FSU FE model was generated based on the standard test (for compression, flexion, extension, lateral bending, torsion and shear). The movements of the FSU FE model based on the aforementioned standardized test when the sex, age, weight and height varies in a range for each individual (30-80 years; 70-120 kg; 160-190 cm) were simulated. Quadratic regression models were generated for each standardized test using RSM. An ANOVA test showed that all of the tests have a significant influence on weight and age, whereas height influences only those tests that involve rotation of the FSU (flexion, extension and lateral bending). Normal weight, overweight and obesity BMI classifications were considered in determining the healthy weight with the following constraints: the limit angles of flexion and lateral bending, as well as the maximum posterior bulge limit of the IVD, could not exceed of one-third of the spinal canal. The proposed method concluded that: (1) normal BMI values do not cause damage to the FSU, (2) some overweight BMI values may cause damage to the FSU for a certain range of ages and heights and (3) for BMI obesity values, the risk of damage to the FSU may be imminent.

Rib fractures prediction method for kinetic energy projectile impact: from blunt ballistic experiments on SEBS gel to impact modeling on a human torso FE model

The present paper aims to assess the risk of rib fractures caused by any rigid less-lethal kinetic energy projectiles. To that end, a coupled experimental and numerical approach is proposed to relate ballistic experiments with the risk of blunt trauma. A polymer gel block is employed as ballistic testing medium to interpret ballistic impacts through the measurement of the dynamic gel wall displacement. Moreover, a biofidelic 50th percentile human torso finite element model created in the code Hypermesh (Altair HyperWorks ©) is used to replicate experiments and real world accidents. Then, the probability curve of rib fractures is a function of the viscous criterion and derives from a study on human cadaver mid-sternum available in the literature. Twelve impact conditions of rigid projectiles are applied to a SEBS gel block and are replicated on the human torso model mid-sternum. A statistical analysis is performed by virtue of a Spearman's correlation matrix in order to identify relations between experimental measurements and the viscous criterion evaluated numerically. The determination of both statistical significances and correlation coefficients results in several strong correlations between experimental measurements and the viscous criterion evaluated numerically. These relations imply the establishment of transfer functions between experimental metrics on the gel block (the maximum gel wall displacement and a gel wall displacement – rate of displacement based metric) and the probability of rib fractures. Finally, these correlations constitute a primary and an up-and-coming predicting tool for the risk of rib fractures.

Study of Occupant Head Injuries Using Human FE Models in Side Collisions

Study of Occupant Head Injuries Using Human FE Models in Side Collisions

Occupant Injury Predictions during Side Collisions Using Human Body FE Models Containing Muscle Controllers

Occupant Injury Predictions during Side Collisions Using Human Body FE Models Containing Muscle Controllers

Analysis of different modeling approaches of the cochlea impedance in FE models of the human middle ear

Finite element models of the human middle ear are important tools in the development of implantable hearing aids or to study the impact of surgeries on middle ear dynamics. Thus, the cochlea impedance seen by the middle ear is a very important parameter when modeling the middle ear dynamic behavior. The cochlea impedance can be seen as the load effect provide by cochlea fluid over the stapes footplate. Although several papers describe human middle ear FE models, there is no consensus about how to better include the cochlea impedance at FE model. In this work, a review of the different modeling approaches found in the literature is presented. Each approach was implemented, and the results for the middle ear frequency response (stapes velocity versus tympanic membrane pressure) were compared. The results are also compared with experimental data for the middle ear frequency response. An alternative model is also proposed that includes measured data for the cochlea impedance. From the results, it was observed significantly difference between methods in frequencies above 900 [Hz]. It was concluded that using the experimental data, it is added more damping at high frequencies.

Modeling of human model for static pressure distribution prediction

Vehicle comfort, the key factor that influences the purchase of automobile products, is becoming increasingly important. However, the processes of traditional empirical and experimental approaches to design a new, more comfortable seat is complicated, time consuming and costly. The finite element method could facilitate, accelerate and economize this process. In the present work, a complete human FE model is established based on the Hybrid III dummy, the appropriate element size of 10 mm was ascertained. The body segment mass was verified by comparing segment mass percentages obtained from this model with previous data. The further validation study of the human model was achieved via the human pressure distribution experiments over human-rigid seat interaction under three postures, the validation reveals that the simulation results agree well with the experimental data. On this basis, the human model was applied to predict the interactions between human body and an automobile seat, then the contact pressure distribution, additional information about the contact shear stresses distribution and stress distribution within the soft tissue were obtained through simulation. The human model presented in this paper can reflect the interaction between human body and automobile seat precisely. Relevance to industryThe results deduced that the model is capable of realistically predicting pressure distribution, the present model allows the evaluation of seating comforts in a virtual phase of seat development, and the study can be taken as reference for vehicle seat design and biomechanical evaluation.

A Simple Dynamic Model Based on Human FE Model in Side Impact Crash

A Simple Dynamic Model Based on Human FE Model in Side Impact Crash

Development of a Human Body FE Model Including Discrete Internal Organs

Development of a Human Body FE Model Including Discrete Internal Organs

Kinematics and Thoracic Deformation of an Elderly Size Human FE Model in Front Impact Sled Analysis

Kinematics and Thoracic Deformation of an Elderly Size Human FE Model in Front Impact Sled Analysis

Development and validation of an advanced anisotropic visco-hyperelastic human brain FE model

This paper proposes the implementation of fractional anisotropy and axonal fiber orientation from diffusion tensor imaging (DTI) of 12 healthy patients into an existing human FE head model to develop a more realistic brain model with advanced constitutive laws. Further, the brain behavior was validated in terms of brain strain against experimental data published by Hardy et al. (2001, 2007) and for brain pressure against Nahum et al. (1977) experimental impacts. A reasonable agreement was observed between the simulation and experimental data. Results showed the feasibility of integrating axonal direction information into FE analysis and established the context of computation of axonal elongation in case of head trauma.

Validation of Age-specific Human FE Models against Side Impact

Validation of Age-specific Human FE Models against Side Impact

Repositioning the Knee Joint in Human Body FE Models Using a Graphics-Based Technique

Objective: Human body finite element models (FE-HBMs) are available in standard occupant or pedestrian postures. There is a need to have FE-HBMs in the same posture as a crash victim or to be configured in varying postures. Developing FE models for all possible positions is not practically viable. The current work aims at obtaining a posture-specific human lower extremity model by reconfiguring an existing one. Methodology: A graphics-based technique was developed to reposition the lower extremity of an FE-HBM by specifying the flexion–extension angle. Elements of the model were segregated into rigid (bones) and deformable components (soft tissues). The bones were rotated about the flexion–extension axis followed by rotation about the longitudinal axis to capture the twisting of the tibia. The desired knee joint movement was thus achieved. Geometric heuristics were then used to reposition the skin. A mapping defined over the space between bones and the skin was used to regenerate the soft tissues. Mesh smoothing was then done to augment mesh quality. Results: The developed method permits control over the kinematics of the joint and maintains the initial mesh quality of the model. For some critical areas (in the joint vicinity) where element distortion is large, mesh smoothing is done to improve mesh quality. Conclusions: A method to reposition the knee joint of a human body FE model was developed. Repositions of a model from 9 degrees of flexion to 90 degrees of flexion in just a few seconds without subjective interventions was demonstrated. Because the mesh quality of the repositioned model was maintained to a predefined level (typically to the level of a well-made model in the initial configuration), the model was suitable for subsequent simulations.

Different Factors Influencing Post-crash Pedestrian Kinematics

Pedestrian crashes are the most frequent cause of traffic-related fatalities worldwide. The high number of pedestrian accidents justifies more active research work on passive and active safety technology intended to mitigate pedestrian injuries. Post-impact pedestrian kinematics is complex and depends on various factors such as impact speed, height of the pedestrian, front-end profile of the striking vehicle and pedestrian posture, among others. The aim of this study is to investigate the main factors that determine post-crash pedestrian kinematics. The injury mechanism is also discussed. A detailed study of NASS-PCDS (National Automotive Sampling System - Pedestrian Crash Data Study, US, 1994-1998), showed that the vehicle-pedestrian interaction in frontal crashes can be categorized into four types: Thrown forward, Wrapped position, Slid to windshield and Passed over vehicle. A Principal Component Analysis (PCA) was performed and 11 independent factors were identified for study from a set of 26 variables, as defined in NASS-PCDS. Pedestrian-vehicle size ratio and the impact speed are the two most influential factors that determine post crash pedestrian kinematics. However, the standing posture of a taller pedestrian can also cause rotational movement around the local Z axis, leading to a face-up/down mode of head-face impact before falling on the hood. The findings from the NASS-PCDS study were also confirmed and verified with the help of numerical simulations performed using two modified JAMA human FE models. An adult model (male, 175cm and 72kg) and a properly scaled child model (6 years old, 120cm and 21kg) were effectively utilized to investigate the post-crash kinematics in different conditions. Language: en