Occupant Dynamic Responses for Evaluation of Compliance Characteristics of Aircraft Bulkheads

1992 ◽  
Author(s):  
Hamid M. Lankarani ◽  
Deren Ma ◽  
Rajiv Menon
Keyword(s):  
Head Injury ◽  
Contact Force ◽  
Head Injuries ◽  
Element Model ◽  
Dynamic Responses ◽  
Instrument Panel ◽  
Force Model ◽  
Sled Test ◽  
Contact Force Model ◽  
Head Injury Criteria

Abstract One important aspect of aircraft crashworthiness studies is to reduce head injuries to an aircraft occupant in case of a head contact with its surroundings. In view of the significance of this problem, studies of post-crash dynamic behavior of victims and the compliance characteristics of the aircraft bulkhead are necessary in order to reduce severe head injuries. Crash dynamics program SOM-LA/TA, incorporating a dynamic model of the human body with a finite element model of the seat structure was used. Modifications including development of more accurate contact force models and an occupant/seat envelope were performed in SOM-LA/TA. It was then used as an analytical tool for determination of the occupant response and the compliance characteristics of the bulkhead in various crash environments. Correlated studies of analytical simulations with impact sled test results were accomplished. It was observed that the code reasonably predicted the Head-Injury-Criteria (HIC) for the triangular-shaped pulses. A parametric study of the coefficients in the contact force model was then performed in order to obtain a correlation between the HIC and the coefficients in the contact force model. A measure of optimal values for the bulkhead compliances and displacement requirements was thus achieved in order to keep the possibility of head injury as little as possible. This information could in turn be used in the selection of suitable materials for the bulkhead, instrument panel, or interior walls of an aircraft.

Dynamics Analysis of Truss Deployment Mechanism With Imperfect Joint Considering Input Fluctuation

2020 ◽  
Author(s):  
Zhengfeng Bai ◽  
Jijun Zhao ◽  
Xin Shi
Keyword(s):  
Contact Force ◽  
Dynamic Performance ◽  
Mathematic Model ◽  
Friction Model ◽  
Dynamic Responses ◽  
Force Model ◽  
Normal Contact ◽  
Clearance Joint ◽  
Contact Force Model ◽  
Dynamic Performance Analysis

Abstract Modern spacecraft usually has large deployment structure, which consisting of plenty of joints could produce undesirable dynamic responses when considering clearances in joints and driving input fluctuation. However, in the dynamic performance analysis of space deployment mechanism, the clearances and input fluctuation are always ignored. In this study, the dynamic responses of a flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are investigated using computational methodology. First, the mathematic model of clearance joint is established. The revolute clearance joint is considered as force constraint and the joint components of an imperfect joint with clearance are modeled as contact bodies. The normal contact force model of clearance joint is established using a continuous contact force model considering energy loss. The friction effect is considered using a modified Coulomb friction model. Then, the dynamics performances of the flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are presented and discussed. Different case studies for the scissor-like truss deployment mechanism with clearance are investigated considering driving input fluctuation. The simulation results show that the dynamic characteristics of the mechanism with clearance joint are changed more obviously when considering driving input fluctuation. Therefore, investigation implies that dynamics responses of the truss deployment mechanism are much worse when considering clearance joint and input fluctuation, which indicates that driving input fluctuation leads to more obvious degradation of the dynamic performance of the truss deployment mechanism with imperfect joint.

scholarly journals Finite Element Analysis of the Motorcycle Helmet Material against Impact Velocity

2021 ◽  
Vol 9 (9) ◽  
pp. 979-995
Author(s):  
Arnav Gupta
Keyword(s):  
Finite Element ◽  
Head Injury ◽  
Impact Velocity ◽  
Head Injuries ◽  
Dynamic Responses ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Injury Criteria ◽  
Motorcycle Helmet ◽  
Head Injury Criteria

Abstract: A motorcycle helmet is the best protective headgear for the prevention of head injuries due to direct cranial impact. A finite element model based on realistic geometric features of a motorcycle helmet is established, and explicit finite element code is employed to simulate dynamic responses at different impact velocities. Peak acceleration and Head injury criterion values derived from the head form are used to assess the protective performance of the helmet. We have concluded that the dynamic responses of the helmet dramatically vary with impact velocity, as well as the mechanical properties of the outer shell and energy- absorbing liner. At low velocities e.g. 8.3 m/s, the shell stiffness and liner density should be relatively low to diminish head- contact force. At high velocity e.g. 11m/s, a stiffer shell and denser liner offer superior protection against head injuries. Different tests were performed in ansys explicit dynamics solver by taking different materials and calculating PLA, Head Injury Criteria, K.E, P.E, contact energy etc. The results obtained for different materials were then compared with easy other to draw the necessary conclusion’s. Keywords: Peak Linear Acceleration (PLA), Head Injury Criteria.

scholarly journals Dynamics of Multibody Systems With Spherical Clearance Joints

2005 ◽  
Author(s):  
P. Flores ◽  
J. Ambro´sio ◽  
J. C. P. Claro ◽  
H. M. Lankarani
Keyword(s):  
Contact Force ◽  
Multibody Systems ◽  
Contact Forces ◽  
Force Model ◽  
Clearance Joints ◽  
Continuous Contact ◽  
Clearance Joint ◽  
Contact Force Model ◽  
Dynamics Of Multibody Systems ◽  
The Impact

This work deals with a methodology to assess the influence of the spherical clearance joints in spatial multibody systems. The methodology is based on the Cartesian coordinates, being the dynamics of the joint elements modeled as impacting bodies and controlled by contact forces. The impacts and contacts are described by a continuous contact force model that accounts for geometric and mechanical characteristics of the contacting surfaces. The contact force is evaluated as function of the elastic pseudo-penetration between the impacting bodies, coupled with a nonlinear viscous-elastic factor representing the energy dissipation during the impact process. A spatial four bar mechanism is used as an illustrative example and some numerical results are presented, being the efficiency of the developed methodology discussed in the process of their presentation. The results obtained show that the inclusion of clearance joints in the modelization of spatial multibody systems significantly influences the prediction of components’ position and drastically increases the peaks in acceleration and reaction moments at the joints. Moreover, the system’s response clearly tends to be nonperiodic when a clearance joint is included in the simulation.

Hertz Contact Force Model With Permanent Indentation in Impact Analysis of Solids

1992 ◽  
Author(s):  
Hamid M. Lankarani ◽  
Parviz E. Nikravesh
Keyword(s):  
Contact Force ◽  
Impact Analysis ◽  
Equations Of Motion ◽  
Solid Particles ◽  
Hertzian Contact ◽  
Contact Period ◽  
Force Model ◽  
Unknown Parameters ◽  
Contact Force Model ◽  
Energy And Momentum

Abstract A continuous analysis method for the direct-central impact of two solid particles is presented. Based on the assumption that local plasticity effects are the sole factor accounting for the dissipation of energy in impact, a Hertzian contact force model with permanent indentation is constructed. Utilizing energy and momentum considerations, the unknown parameters in the model are analytically evaluated in terms of a given coefficient of restitution and velocities before impact. The equations of motion of the two solids may then be integrated forward in time knowing the variation of the contact force during the contact period. For Illustration, an impact of two soft metallic particles is studied.

Experimental Validation of a Volumetric Planetary Rover Wheel/Soil Interaction Model

2013 ◽  
Author(s):  
Willem Petersen ◽  
John McPhee
Keyword(s):  
Contact Force ◽  
Interaction Model ◽  
Contact Model ◽  
Soil Parameters ◽  
Model Parameters ◽  
Force Model ◽  
Normal Contact ◽  
Planetary Rover ◽  
Normal Contact Force ◽  
Contact Force Model

For the multibody simulation of planetary rover operations, a wheel-soil contact model is necessary to represent the forces and moments between the tire and the soft soil. A novel nonlinear contact modelling approach based on the properties of the hypervolume of interpenetration is validated in this paper. This normal contact force model is based on the Winkler foundation model with nonlinear spring properties. To fully define the proposed normal contact force model for this application, seven parameters are required. Besides the geometry parameters that can be easily measured, three soil parameters representing the hyperelastic and plastic properties of the soil have to be identified. Since it is very difficult to directly measure the latter set of soil parameters, they are identified by comparing computer simulations with experimental results of drawbar pull tests performed under different slip conditions on the Juno rover of the Canadian Space Agency (CSA). A multibody dynamics model of the Juno rover including the new wheel/soil interaction model was developed and simulated in MapleSim. To identify the wheel/soil contact model parameters, the cost function of the model residuals of the kinematic data is minimized. The volumetric contact model is then tested by using the identified contact model parameters in a forward dynamics simulation of the rover on an irregular 3-dimensional terrain and compared against experiments.

scholarly journals Evaluation of Head Injury Criteria for Injury Prediction Effectiveness: Computational Reconstruction of Real-World Vulnerable Road User Impact Accidents

2021 ◽  
Vol 9 ◽  
Author(s):  
Fang Wang ◽  
Zhen Wang ◽  
Lin Hu ◽  
Hongzhen Xu ◽  
Chao Yu ◽  
...  
Keyword(s):  
Head Injury ◽  
Real World ◽  
Head Injuries ◽  
Axonal Injury ◽  
Diffuse Axonal Injury ◽  
Road User ◽  
Injury Criteria ◽  
Brain Deformation ◽  
Vulnerable Road User ◽  
Head Injury Criteria

This study evaluates the effectiveness of various widely used head injury criteria (HICs) in predicting vulnerable road user (VRU) head injuries due to road traffic accidents. Thirty-one real-world car-to-VRU impact accident cases with detailed head injury records were collected and replicated through the computational biomechanics method; head injuries observed in the analyzed accidents were reconstructed by using a finite element (FE)-multibody (MB) coupled pedestrian model [including the Total Human Model for Safety (THUMS) head–neck FE model and the remaining body segments of TNO MB pedestrian model], which was developed and validated in our previous study. Various typical HICs were used to predict head injuries in all accident cases. Pearson’s correlation coefficient analysis method was adopted to investigate the correlation between head kinematics-based injury criteria and the actual head injury of VRU; the effectiveness of brain deformation-based injury criteria in predicting typical brain injuries [such as diffuse axonal injury diffuse axonal injury (DAI) and contusion] was assessed by using head injury risk curves reported in the literature. Results showed that for head kinematics-based injury criteria, the most widely used HICs and head impact power (HIP) can accurately and effectively predict head injury, whereas for brain deformation-based injury criteria, the maximum principal strain (MPS) behaves better than cumulative strain damage measure (CSDM0.15 and CSDM0.25) in predicting the possibility of DAI. In comparison with the dilatation damage measure (DDM), MPS seems to better predict the risk of brain contusion.

scholarly journals An Investigation of Dynamic Responses and Head Injuries of Standing Subway Passengers during Collisions

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yong Peng ◽  
Tuo Xu ◽  
Lin Hou ◽  
Chaojie Fan ◽  
Wei Zhou
Keyword(s):  
Numerical Simulation ◽  
Head Injury ◽  
Head Injuries ◽  
Dynamic Responses ◽  
Passive Safety ◽  
Friction Coefficients ◽  
Safety Design ◽  
Parametric Studies ◽  
Simulation Results ◽  
Set Up

With the development of the subway and the pressing demand of environmentally friendly transportation, more and more people travel by subway. In recent decades, the issues about passenger passive safety on the train have received extensive attention. In this research, the head injury of a standing passenger in the subway is investigated. Three MADYMO models of the different standing passenger postures, defined as baseline scenarios, are numerically set up. HIC15values of passengers with different postures are gained by systematic parametric studies. The injury numerical simulation results of various scenarios with different friction coefficients, collision acceleration, standing angle, horizontal handrail height, and ring handrail height are analyzed. Results show that the horizontal handrail provides better protection in the three different standing passenger postures. Different friction coefficients and the standing angle have great impact on the head injuries of passengers in three different scenarios. The handrail height also has some effects on head injury of passengers with different standing postures, so it is necessary to be considered when designing the interior layout of the subway. This study may provide guidance for the safety design of the subway and some advices for standing subway passengers.

A continuous contact force model for impact analysis

2022 ◽  
Vol 168 ◽  
pp. 108739
Author(s):  
Jie Zhang ◽  
Xu Liang ◽  
Zhonghai Zhang ◽  
Guanhua Feng ◽  
Quanliang Zhao ◽  
...  
Keyword(s):  
Contact Force ◽  
Impact Analysis ◽  
Force Model ◽  
Continuous Contact ◽  
Contact Force Model
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