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Dear Forum, for a project I want to simulate the effect on a person who is driving a car with 13.88 m/s (50 km/h) and crashes into an obstacle with a 90° angle towards the obstacle (straight front crash). The person is represented by a dummy (50% Male), the seat structure was modeled by altair, as well as the dummy. I created two seatbelts with the Hypercrash tool Belt Generator (Hypercrash --> Safety --> Belt Generator) and deformed the seat with the seat deformer (old) (Hypercrash --> Safety --> Seat Deformer --> Geometrical displacement (old)). Due to simplification I removed the complete lower sector of the seat group and replaced it with a rigid body, which is linked to the floor and the seat. I built the model as follows: Loadcases: -Initial velocity: applied to all parts of the model (13.88 m/s) -Imposed velocity: A function, which decreases the speed from 13.88m/s to 0 within 30 ms. Applied to all parts but the dummy itself. -Gravity load: To maintain physical correctness of the dummys motion. -Added Mass: Applied to all nodes of the dummy to be representative for the human weight. Boundary Conditions: -BC for the seat: All degrees of freedom are locked except for the translation in X-axis (which is the direction of motion). This is applied only for the floor and the ground part of the seat. Contact Interfaces: -Interior contact: Contact between the two seat layers (was set by altair when I imported the model, I did not change any values) -Seat to floor: Contact seat to floor (TYPE7) -Feet to floor: Contact feet to floor (TYPE10) -Seatbelt to dummy: Contact upper/lower seatbelt to dummy/seat (TYPE7) -Dummy to seat: Contact Dummy to seat (TYPE7) The problems I am facing now are: -The Runtime for a single simulation is about 9500 seconds. Can this be regarded as normal, considering the model complexicity? -Results of the simulation differ too much from expactations/reality -->Normally I would have expected the backrest to at least do a little motion, but it remains in its position. -Because of the constraints of the seatbelts, the head of the dummy experiences a very high acceleration. -->Is there any chance, that the Belts ease a little bit (in the beginning) and afterwards tension up, just like in reality? -All elements of the part "LINK", ID:6 delete on the beginning of every simulation. I could not figure out the reason for that, neither in the starter file, nor in the engine file. -During the Simulation it reaches one Point, where all the masses go into one single point/node but I can not figure out, why (see attached Video) Please correct me if I am rootedly wrong with my assumptions. Attached you can find my model files. PS: I am aware of the initial penetrations within the seat. Thanks in advance. Greetings. Modell_Dummy_Sitzgruppe_0001.rad Modell_Dummy_Sitzgruppe_0000.rad Modell_Dummy_Sitzgruppe_0000.M00 Simulation_Video.avi