Development and verification of the hottest MADYMO

MADYMO frontal impact model development and verification

Abstract

virtual test or numerical simulation using MADYMO model is an important tool in the development process of occupant restraint system. In order to obtain reliable models and calculation results, it is necessary to follow the standard modeling and verification process. In this paper, the modeling and verification methods of MADYMO frontal impact model and the matters needing attention are introduced in detail through an example. The response of the model is in good agreement with the US NCAP test results, including the belt and shoulder belt force, thigh force, and the acceleration response of the hip, chest and head. The results of the quality evaluation of the advisor objective model show that the overall score of the model quality reaches 86.5%, so it can be used for further DOE and random analysis to optimize and realize the robust design of the constraint system

introduction

in the development of occupant restraint system, MADYMO simulation is an important analysis and design means, which can be used to predict the protection effect of different design schemes, significantly reduce the number of physical tests, and improve the robustness of restraint system under different load cases. However, the predictive ability of the MADYMO model depends on whether the model can truly reflect the physical collision process of the interaction between the dummy and the vehicle interior components and the current beam system

this paper introduces in detail the modeling and verification methods of MADYMO frontal impact model and matters needing attention through an example of us NCAP, and evaluates the model quality with advisor

frontal collision modeling

as shown in Figure 1, the MADYMO frontal collision model consists of vehicle, occupant and constraints

the system framework modeled in Figure 1

vehicle system is added to the concrete central system

vehicle body system, including: floor, firewall, windshield, ceiling, instrument panel, steering wheel and seat. The instrument panel, steering wheel and seat can also be used as independent subsystems to establish models, which can facilitate the management and replacement of module databases using madymo/exchange

the origin of the vehicle body system is set at the center point of the front axle, and other components can be accurately positioned according to this origin. Generally, the CAD design drawing or FE model of the interior layout can be used for accurate modeling. The FE model of the whole vehicle is used in this paper

according to the collision test results or engineering experience, define the moving hinge at the parts where the vehicle body structure may be deformed to simulate the relevant structural deformation. For example: the connection between floor and firewall or footwell. If the structural deformation intrusion does not need to be considered in the simulation, the initial state of the hinge can be set to lock

restraint system

restraint system includes safety belt and airbag. The safety belt fabric can be modeled by multi-body or multi-body Fe. If the safety belt has obvious sliding on the body surface of the dummy, the multi-body Fe hybrid safety belt shall be used for modeling. The model in this paper adopts multi-body safety belt. The definition of safety belt also includes retractor, force limiter and pretensioner. The size of the force limiter and the pretensioning time of the pretensioner are defined according to the actual situation

DAB airbag grids can be easily generated and folded by using the madymo/folder tool. The influence of different vent hole sizes on airbag performance can be simulated by adjusting the CDEX coefficient without changing the mesh. For the passengers in the normal sitting position, the uniform pressure algorithm can meet the requirements; For out of position passengers, gasflow algorithm is required to accurately simulate the interaction with passengers during airbag deployment. The uniform pressure algorithm is used in this paper

seat model

the contact characteristics of the seat model directly affect the motion response of the dummy's hip. Generally, it is necessary to obtain the stiffness and friction coefficient of the cushion, the stiffness of the seat pan and the anti submergence structure according to the component test. The seat characteristics in this model are obtained through experiments

steering system model

the energy absorption characteristics of steering wheel and steering column can be obtained through component tests. In this test, due to the cushion protection effect of airbag, the steering wheel and steering column were not significantly deformed. Therefore, the model was not specially tested for parts of this model, and the generic steering system model was directly used

dummy model and positioning

madymo provides a rich dummy model library, which can be easily called directly through the include statement. Accurate positioning of the dummy to avoid personal injury caused by short circuit of the machine is very important to the simulation results, which can be realized according to the measured values or preimulation before the test [2]

definition of contact

in frontal collision, the main contacts are: dummy shoes and floor/firewall, dummy hips and seats, knees and knee pads, dummy and airbag, etc. If a finite element seat belt is used, the contact between the seat belt and the dummy is defined

acceleration field

apply the acceleration signal and gravity field at the lower end of column B measured in the test to the MADYMO model, and the complete model is shown in Figure 2

Figure 2 frontal impact model

model validation

madymo model validation follows the principle of "from bottom to top", that is, lower limbs, hips, chest, and finally head response; The force and acceleration signals shall meet the basic characteristics of "starting time, shape, peak value, peak time and pulse width", as shown in Figure 3:

Figure 3 model verification process

verification results

figure shows the comparison between MADYMO model response and US NCAP crash test results

advisor evaluation results

using the advisor tool [3,4], we can get the objective and quantitative evaluation scores of model quality, as shown in Table 1. Table 1 advisor model quality evaluation results

discussion

a good MADYMO model should truthfully reflect the physical process of the whole collision. During the collision, all parts of the dummy's body gradually contact with the vehicle body/restraint system from bottom to top. The starting time of force and acceleration signals is a direct reflection of the collision process. In order to ensure the correct contact time, the positioning of the interior layout and the dummy is the key, otherwise the actual collision process cannot be accurately reflected. Therefore, the positioning parameters of the dummy before impact shall be recorded in detail and accurately. It can be seen from the verification results (Figure) of the model that the physical process of actual collision has been basically reflected in the simulation process

secondly, it is necessary to ensure the force on the thigh and the acceleration in the X-and z-directions of the hip. By ensuring the correctness of the hip acceleration, the basic motion of the dummy can be determined to ensure the correct response of the chest and head. The X-and Z-direction accelerations of hip are affected by thigh force, belt force, seat cushion stiffness and friction. The test results of knee bolster, seat and safety belt components can improve the accuracy of hip response

the chest X-direction acceleration is mainly affected by the shoulder belt force and airbag, and the chest Z-direction acceleration is greatly affected by the cushion and airbag. The acceleration of the head is mainly affected by the airbag. When doing verification, pay attention to the influence relationship between various factors, so as to establish a better model

since the multi-body safety belt model is used in this model, the sliding of the safety belt on the dummy's body surface cannot be simulated, resulting in obvious differences between the shoulder belt stress rising edge and the measured results. This problem can be solved by using the face Q dummy model and the finite element safety belt

in addition, the test vehicle has obvious pitch motion after 100ms, but this factor is not considered in this model, resulting in differences in the responses of hips, chest and head after 100ms. The validated MADYMO model can be used for parameter sensitivity analysis, constraint system optimization, collision waveform optimization, ride down efficiency analysis, etc

references

1 MADYMO Theory Manual.

2. MADYMO Applications Manual.

3. ADVISER Reference Guide.

4. Ad continues to extend the industrial chain

contact information

Author: zhuhangbin

address: 14/F, No. 1090, Century Avenue, Pudong New Area, Shanghai

postal code: 200120

:86 2158358036

email:u@ (end)