Paris - French car maker Renault has successfully completed the first 'fully virtual' preliminary design of a new car seat, using software for virtual seat prototyping from ESI Group.
"Using PAM-COMFORT, within a short period of time, and with few resources, we were able to deliver a new seat design meeting our objectives," said Jérôme Makala, head of Renault's Comfort and Safety Research Department, in a 3 Nov ESI announcement.
ESI, which claims to be a leading supplier of digital simulation software for prototyping and manufacturing processes, said its PAM-COMFORT software offers 'a scalable, innovative and customised solution dedicated to virtual manufacturing and virtual testing (static and dynamic) of the soft parts of a seat."
According to ESI, Virtual Seat Prototyping involves several chained simulated steps ranging from seat manufacturing, occupant static seating, to occupied seat NVH (noise, vibration, harshness), where the stresses resulting from each step are needed for the next one.
The chaining is necessary to accurately predict seat behaviour under numerous loading conditions (trimming, dummy loading, various human shapes and sizes, and vibrations) and for various design changes (materials and shape), the software group pointed out.
ESI said that Renault is deploying the full Virtual Seat Prototyping methodology, in which an important step after the preliminary design of a new seat model is virtual testing for dynamic comfort performance using PAM-COMFORT.
This involves three steps.
* To predict seat comfort accurately, Renault runs a dynamic test of seat transmissibility, using a static weight. This helps evaluate the seat frequency response, telling Renault how the seat contributes to the car's vertical acceleration filtering of the car. This is of crucial importance to dynamic seat comfort, ESI stresses. This test is used improve and validate the seat design.
* Next comes seat and vibration modelling, a procedure simulated with a finite element calculation using PAM-COMFORT. When seat manufacturing simulations are complete, a dummy is imported into the model to launch the computation. This calculation is divided in two phases: a static one where the dummy is seated and equilibrium is computed to know the stress and strain states of the various parts of the seat precisely. In a second dynamic phase a vertical acceleration signal is applied to the seat rail to obtain the seat dynamic transmissibility at the interface with the dummy.
* Finally, the seat dynamic transmissibility is assessed. Here the computed results" showed a very good level of correlation with physical tests," confirming the validity and predictability of Renault's simulation modelling andof the methodology applied, ESI commented.
"This simulation input can truly be considered as an 'ultra realistic' model, since it allows the simulation of the whole complex mechanical phenomena of the seat, the non-linearity of the materials, the large displacements of the cushion foam and springs, as well as the effect of the cover trimming", said Renault's Makala. "The developed models and methodology enable the computation of predictive results, using only physical parameters and without any tuning of filtering. This good correlation between simulation and test results confirms the ability to assess the riding seat comfort in a full virtual process."
Finally, since Renault is satisfied with the results of this first 'fully virtual' process with PAM-COMFORT, it has started to transfer this methodology to its seat providers and to Nissan, ESI said.