MADYMO model

Finite-Element (FE) Models. The detailed response of selected parts of the body and the environment being simulated (e.g., head and neck, spine, and vehicle seating) have been modeled by using finite elements (FEs). In the MADYMO model, the FEs can interact with the multibody model elements. Examples of human body subsystems that have been modeled with FEs include the spine, to predict the injury potential of vertebrd compression and torsional loads, and the head and neck, to predict rotation of the head and neck loads during rapid horizontal deceleration (see Fig. 10.12) (RTO-MP-22, 1999). 

FIGURE 10,12 Response of human volunteers and the 3D MADYMO model of the head and neck to spineward decelerations. The range of responses from human subjects is shown by the dotted lines, and the response of the model with passive and active muscles is shown by the dashed and continuous lines, respectively (see text for explanation of the motions plotted). (RTO-MP-20,1999.)... 

An example of the use of the MADYMO model to simulate air bag inflation and occupant response to the frontal collision of an automobile is shown in Fig. 10.13. In this diagram, the response of a person wearing a shoulder and lap seat belt has been calculated at 25-ms time intervals following the initiation of air bag inflation. The forward rotation of the head is clearly visible and is arrested before it impacts the chest. Also, the flailing of the arms can be seen. 

While the Hybrid III manikin can reproduce some human responses, the head and neck system does not introduce appropriate head rotation lag (see neck angle versus head angle in Fig, 10.11c) or torque at the occipital condyles joint (see moment of force OC joint versus time (Fig. 10.11c)]. Note, however, that the linear acceleration of the center of gravity of the head is well reproduced by the manikin, except for the peak acceleration at 100 ms [see response of head acceleration versus time (Fig. 10.11/)]. In contrast, the three-dimensional head and neck model for MADYMO can be seen to reproduce most human responses when active muscle behavior is included (the continuous lines in Fig. 10.12). In this computer model, the neck muscles are represented by simple cords between anatomical attachment points on the head and the base of the neck. 

FIGURE 10.13 MADYMO simulation of the response of a person wearing a shoulder and lap seat belt to the inflation of an air bag in a frontal motor vehicle collision. The model predicts the body position every 25 ms after the collision. Note the time for the air bag to inflate (between 25 and 50 ms), the rotation of the head, the flailing of the arms, and the bending of the floor. (AGARD-Aft-330,1996.)... 

Intrinsic parameters. Dummy data with Madymo, the model was almost ready to be used. A database for the dummy we employed for the sled test, namely the Part 572 dummy, was provided with the code. It contains all the validated dynamic properties of the dummy. We found useful to modify the ellipsoids and the location of the accelerometers proposed in the previous database. 

Belt route another problem is to find the routes of the shoulder and lap belts on the dummy, with the evidence that these routes may often change during a crash, corresponding to transverse slip not modelled in Madymo. Another reason to treat this problem analytically is that we wanted to simulate earlier tests, where the connecting points of the strap on the dummy were not known. Therefore, we chose to model the route and calculate geometrical characteristics of the belt with a pre-processor, in the initial position of the dummy. It is explained below how to control this parameter. 

H. J. Petit, A. Hirth, B. Pletschen (1992), "Validation of Simulation Models for Different Restraint-System Conceptions", 3rd International Madymo Users Meeting, Detroit, USA. 

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