Eine durchgängige Prozesskette für die virtuelle Sitzentwicklung vor dem Bau des ersten Hardware-Prototypen wurde entwickelt. Alle notwendigen Schritte von Interaktion zu Designvorgabe durch die Softwarelösung PADMAKER, über den Aufbau eines FEModells des belegten Sitzes bis zur statischen und dynamischen Komfort-Simulation werden aufgezeigt. Durch die geschlossene Vorgehensweise können alle Kriterien der Sitzentwicklung miteinander gekoppelt werden. Die Verwendung des anatomischen FEMenschmodells CASIMIR erlaubt dabei in einer frühen Phase die Optimierung von Sitzeigenschaften sowohl statisch als auch unter dem Aspekt Humanschwingungen. Die berechneten Simulations-Resultate von komfortrelevanten Größen wie Sitzdruckverteilung und Sitzübertragungsfunktion zeigen eine gute Korrelation mit entsprechenden Messergebnissen.

In the field of human whole-body-vibrations the loads out of driving with passenger cars respectively trucks and out of operating construction vehicles represent significant factor. On the one side a standard working-day of e.g. a taxi driver causes a permanent exposure of the human body. On the other side within the operation of construction vehicles impacts occur very often and inducing high peak loads. Avoiding the related discomfort and the damage of the driver's health especially the lower lumbar spine area, the static and dynamic comfort must be considered within the seating development. At the moment the OEM of the automobiles and construction vehicles carry out an appropriate evaluation by the measurements in the vehicle or on the test rig. As this is executed on the basis of hardware-prototypes, an optimisation due to static and dynamic comfort criterias is very time consuming and costly. The presented paper describes a continuous process chain for virtual seat development considering all aspects from the design to an evaluation by the comfort quantities as the seat pressure distribution and the seat transfer function. The input for the process is the A-surface from the Design, the material properties of the applied foam and trim and final a FE-model of the seat structure. The model can be derived from crash-models, but must be adjusted to the requirements of the comfort simulation. The first step is then the simulation of the trimming process by the software PADMAKER. Considering the material properties the trimming process the stress strain condition of trim and foam is identified, representing partly an input for the final comfort simulation. Beside this PADMAKER gives as a result the pre-cut-part of the trim and the out-of-the-tool geometry of the foam, which can directly be used by the manufacturer. The next step is the model setup of the occupied seat. Therefore an anatomical model of the human with a predictive character must be used to fulfil the requirements of the comfort simulation. The applied FE-model CASIMIR satisfies this by the following model parts: Model geometry derived from human anatomy, Masses, stiffness and damping properties defined via physiological data, Detailed model of lumbar spine, Model of the compliant tissue in the interaction to the seat, Consideration of static and dynamic muscle activation. Furthermore CASIMIR reproduces measurements of the dynamic mass of the passenger, which is essential for the computation of the seat-transfer-function. The simulation is carried out in two steps. In the first step the static seating process is computed applying a gravity load vector onto CASIMIR. The computation considers due finite displacements the nonlinearities out of material and geometry. The most important results are the seat-pressure-distribution and the position of the hip joint, where the simulation correlates well with measurements. The dynamic simulation is based on the operation point of the static simulation. There the model properties are linearised. The computation is carried out by the excitation of the seat rail. The dynamic comfort is then evaluated by the seat-transfer-functions, where the results of the simulation match the measurements. According the results of the seating comfort the users has then the possibility to optimise the seat by a change of the structure or the material. Correspondingly the input must be varied and the user can start up the process at the point of the change. Through the application of a continuous virtual process chain the OEM or Tier-1-supplier has the following advantages according whole-body-vibrations: Avoidance of expensive late modifications at the seat or construction vehicle, Allowance for a possible optimisation of weight of the seat structure, Noticeable reduction of the test expenditure in case of unwanted vibrations, Increased information flow between different parts of the seat development, as one tool is used for different applications.