"At our Research and Technologies departments, we use Altair software every day to evaluate the structure of our seats under static and dynamic loads and to assess the feasibility to use thermal molding and stamping within the manufacturing of the seat
components. In the future, we will also employ Altair software for the optimization of foam thickness, characteristics, and weight to further optimize the seat architecture while still keeping the comfort criteria in mind."
– Jeremy Cailleteau, RD Engineer, Safran Seats
Improving Seat Ergonomics to Reduce Passenger Discomfort
A major concern for the company is the optimization of the comfort of aircraft passengers. In addition, the airplane seat market is highly competitive and new; high-quality seats have to be brought to market as quickly as possible. To assess the ergonomic
quality of a seat, the engineers needed a tool with which they could simulate all biomechanical discomfort sources for factors such as internal thighs soft tissue compression for a seated passenger.
Evaluating the Seat Design with Biomechanical Models
Numerical simulation to evaluate seat designs is a good approach to introduce a fast and efficient optimization process for factors such as internal thighs soft tissue compression for a seated passenger. Designers relied on the Altair HyperWorks suite
to simulate the biomechanical factors. Soft tissue compression, the factor under investigation, can be estimated by applying two parameters: the external contact pressure and the direct tissue strain. To handle this simulation engineers created two
kinds of models with which they could estimate each of the discomfort factors. By employing the Altair solutions and incorporating the relation between simulation outputs and the several discomfort factors, the tool was able to deliver a quantification
of the ergonomic quality. With these results and insights, the engineers were able to optimize the seat design and material, hence the potential discomfort of the passengers sitting in these seats could be reduced. In summary, the models created with
the Altair HyperWorks suite enabled the engineers to evaluate the structural behavior and gain valuable insights for the following topics:
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Creation of a general model to estimate the contact pressure
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A parametric model of a human, containing the bones and soft tissue structure of the pelvic-thigh area was developed from statistical shape analysis.
The database of the model was created using scan data of 36 people. Thanks to this approach, any anthropometry can be simulated to receive the seat contact pressure and make a first assessment of the seat’s ergonomics. such as internal thighs soft
tissue compression for a seated passenger.
Detailed Model for Internal Strain Estimation
A detailed model of a 50th percentile male has been built from MRI images. This model contains the accurate anatomy of all muscular and fat tissues. With this model, the internal strain in the different tissue layers can be approximated giving an estimation
of loads applied to the tissue. such as internal thighs soft tissue compression for a seated passenger.
Contact Pressure Validation
The parametric model has been validated by comparing seat pressure and experimentally measured seat pressure on a set of 12 people. This was simulated with Altair Radioss™ solver. With this model, it was possible to predict the contact pressure
with a mean error of the estimated maximal pressure of 16% over the 12 subjects. such as internal thighs soft tissue compression for a seated passenger.
Strain Validation with MRI
The detailed model has been validated by comparing the soft tissue strain simulated and measured with MRI. The strain has been measured for different load cases and several locations. The model provided a good approach to simulate the strain when sitting,
with error rates lower than 19%. such as internal thighs soft tissue compression for a seated passenger.
Faster Development Thanks to Deeper Insights
Using the Altair HyperWorks Suite of products, Safran was able to gain deep insight into various fields of interest, such as contact pressure or structural strain. In particular, Altair software enabled the design team to evaluate the overall behavior
of the seat structure under static and dynamic stress as well as thermal molding and stamping feasibility. Furthermore, by developing biomechanical models with Altair HyperWorks, they were able to achieve a mean error of the estimated maximal pressure
of 16% and an internal strain estimated with an error lower than 19%. In addition to providing deeper insights, numerical simulation helped the engineers to resolve development issues quickly and efficiently. Due to their highlevel of satisfaction
with the results, Safran Seats will continue to employ Altair tools in the future to optimize foam thickness, characteristics, and weight to further improve the comfort of aircraft passenger seats. Increasing the use of simulation, in particular,
the Altair HyperWorks Suite, will lead their engineers to faster development and hence to a shorter time to market.
