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Moka89

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About Moka89

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  1. Hi George, thank you very much for your immedeate answer. Everything worked fine! Now there are other problems, that occur, namely: The dummy just does not move Forward into the direction of Motion. The upper Body does not rotate and thus does not really dive into the Airbag. I have already checked following Points: -Center of gravity of the dummy. It is identical with the COG of the root model, which I got from the Altair Folder --> Can this dummy even be used for this Kind of Crash Simulation or do I Need to take another one? The Name of the Dummy is: "HYBRID III 50% DUMMY FINE MESH V_1.2" -The inertia of the dummy's rigid Bodys. Same here -The torque and Tension stiffnesses of the spring Elements, which refer as Joints within the dummy -The belt force limiter function aswell as the belt pretensioner -I simulated the whole model without an upper belt attached to the dummy --> still no Rotation of the upper body -The contact Interfaces were updated as advised by you, so there are no frozen contacts at all. Attached you can find the latest Video of the Simulation results. Note: The contact Interfaces between the Airbag and the steering wheel Need to be refined, I am Aware of that. Greetings, Mohammad Dummy_Simulation.avi
  2. Hello, thank you very much for your hints. There are still some unanswered questions: I have a Simulation, where the Dummy and the airbag are merged. The airbag ignition and inflation did work very well, when they were not merged. When the models are merged into one model and get an initial velocity and a decceleration via an imposed velocity, the airbag can not infalte well. There are not any contact problems, I did check out on this. Within another simulation I just placed the airbag into the final Dummy position and it did ignite and inflate well, so I assume, that the problem is with the velocity and decceleration (see video) Is there a solution, that I can solve this problem, that the airbag can ignite and inflate normally, while moving and decellerating? Also I noticed, that the dummy does not "lean" forward enough, when deccelerated. Thus he can not fall deep enough into the inflated airbag. I also checked the belt force limiter and also simulated once without an upper belt, but the dummy just does not lean forward (see video) Attached you can find videos of the simulation and the model itself. Thanks in advance. Greetings, Mohammad Video_AIRBAG_Fail.avi Video_Steering_positionl.avi Modell_komplett_0000.rad Modell_komplett_0001.rad dummy_without_upper_belt[1].avi
  3. 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
  4. Hello, first of all thank you for your quick answer. Unfortunately the example you sent me does not solve my problem, because the kind of problem I wanted to simulate is a multi chamber simulation of an airbag, whereas you sent me an example of a single chamber airbag. The Image Card I use is AirBagWithCommunication1, the Card Image in the webinar you sent me is another one. From my point of view the problem lies in the communication surfaces, which lie in between two chambers. They need to communicate to each other but the normal tangents exist in outward directions, so that the communication does not work properly, because one of the chambers does not communicate with the neighbouring chambers in both ways, but only in one way. Maybe you can answer me another question: How can I define two normal tangents for one element? Is that even possible? Many thanks and kind regards.
  5. Hello everyone, I am about to simulate an Airbag deploying and I have got following problem: I would like to get this airbag as a system with several chambers by using the Cardimage "Airbagwithcommunication1" the way i can simulate it with Communication surface. The following example shows how it should be built. RBPLI_UP_0000.rad While simulating comes out this error message In general that system has got 4 chambers, for every single chamber appears the same error message. All chambers volume are closed and the mesh elements are normal outward-orientated. By using the Cardimage "Airbag", the simulation runs without any problems. My question is: How can I create the Surface Communication? Knowing that this Surface Communication has been created manual as Shell Elements 3-4 nodes with HyperMesh. Could it be the right element or not? It will be very kind from your side if you tell me what do you mean about the Errors ID 473 and 902. I have attached the Model and OUTPUT-file. Model_1_0000.outModel_1_0001.radModel_1_0000.rad Thank you so much in advance and wish you a wonderful day. Kind regards MisterKarimi
  6. First of all thanks for your tips, gentlemen. Mr. Pagadala could you please specify what you mean by "changing the order of property". Another general question: Is there a way to create SPH elements directly on a surface instead of a volume?
  7. Hello everybody, Is anyone well informed about SPH Inlets/Outlets Conditions? I´m a beginner and have little knowledge, here is my situation: I´m making a simulation of a pipe. The fluid is air. The SPH that are defined at the Inlet should flow through the pipe and be eliminated at the Outlet. First problem is that only a part of the SPH are eliminated at the Outlet. Second problem is that my calculation time is very long even for simple simulations. Some data on the simulation: My units are: kg, mm, ms, kN Formula used to calculate particle mass: c^3x density I selected Simple Cubic for SPH creation, so the Smoothing Length was set automatically. But on the help section of the homepage of Altair there are several formulas for calculating mp and h. Is it correct the way I´ve done it? SPH-Property: qa=1e-20 and qb=1e-20 For the air I chose material law LAW6 and I entered the following values: Air # RHO_I 1.22E-9 0 # Knu .015 # C0 C1 C2 C3 0 0 0 0 # Pmin Psh 0 1.0132E-4 # C4 C5 E0 .4 .4 2.533E-4 I changed the orientation of the surface segments in a way that their normal vectors point towards the interior of the domain. I defined DIST-inlet = 2xh Density function defined: time: 0, 1e30 ; density: 1, 1 For Fscale I entered my actual air density. I defined the velocity function: Time: 0, 500 ; Velosity: 50, 50 DIST-outlet = 2xh Pressure function: Time: 0, 1e30; Pressure: 1, 1 ; For Fscale I entered 0.005. I set for SPH the „SPH Particle Reserve“ Does SPHGLO-control card has an impact on my results and calculation time? i've also attached the files. Thank you. S-pipe_0000.rad S-pipe_0001.rad
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