NVH Simulations for Car Seat Increasing requirements for the car seat structures drive Faurecia Automotive Seating to increase FEA predictability regarding vibration tests. In scope of interest there is not only value of first resonance frequency but also higher frequency range or amplitude level for defined excitations. Article will describe the methodology setup at Faurecia to extend the use of LS-Dyna to NVH Domain. Focusing efficiency in projects, approach is to derive NVH model from nonlinear “crash” model in order to give quick answer to design office for optimization based on Modal Analysis. Each typical mechanism for car seat like: tracks, recliners or high adjuster, fasteners (screws, bolts, welds or other kinematic connections) have been “modified” to reach linear behavior. To validate NVH FEA models, several correlations with real tests have been performed following classical system engineering approach : small sub-systems like backrest, cushion, tracks and then complete assemblies like : seat frame, frame with headrest, trimmed complete seat. Modes shapes correlations between Real and Virtual Tests were done by calculating MAC (Modal Assurance Criterion) between modes calculated by LS-Dyna (d3eigv files) and modes extracted from Experimental Modal Analysis (Universal Files). Frequency Responses Functions (FRF) from hammer tests were also compared with Ls-dyna models using *FREQUENCY_DOMAIN_FRF cards. Some OEM require also to respect some amplitudes level on seat frames while excited by ground signal (from theoretical acceleration spectrum to real life road signals). Using *FREQUENCY_DOMAIN_RANDOM_VIBRATION card, several shaker tests have been successfully correlated. The presentation will show issues encountered during correlations focusing specifically on management of damping. https://www.dynamore.de/de/download/papers/2016-ls-dyna-forum/Papers%202016/dienstag-11.10.16/noise-vibration-and-harshness/the-toughened-adhesive-polymer-tapo-material-model-is-available-in-ls-dyna-with-keyword-mat_252.-the-model-describes-the-mechanical-behaviour-of-crash-optimised-high-strength-adhesives-under-crash-conditions-and-takes-elasticity-viscoplasticity-and-da/view https://www.dynamore.de/@@site-logo/DYNAmore_Logo_Ansys.svg

NVH Simulations for Car Seat

Increasing requirements for the car seat structures drive Faurecia Automotive Seating to increase FEA predictability regarding vibration tests. In scope of interest there is not only value of first resonance frequency but also higher frequency range or amplitude level for defined excitations. Article will describe the methodology setup at Faurecia to extend the use of LS-Dyna to NVH Domain. Focusing efficiency in projects, approach is to derive NVH model from nonlinear “crash” model in order to give quick answer to design office for optimization based on Modal Analysis. Each typical mechanism for car seat like: tracks, recliners or high adjuster, fasteners (screws, bolts, welds or other kinematic connections) have been “modified” to reach linear behavior. To validate NVH FEA models, several correlations with real tests have been performed following classical system engineering approach : small sub-systems like backrest, cushion, tracks and then complete assemblies like : seat frame, frame with headrest, trimmed complete seat. Modes shapes correlations between Real and Virtual Tests were done by calculating MAC (Modal Assurance Criterion) between modes calculated by LS-Dyna (d3eigv files) and modes extracted from Experimental Modal Analysis (Universal Files). Frequency Responses Functions (FRF) from hammer tests were also compared with Ls-dyna models using *FREQUENCY_DOMAIN_FRF cards. Some OEM require also to respect some amplitudes level on seat frames while excited by ground signal (from theoretical acceleration spectrum to real life road signals). Using *FREQUENCY_DOMAIN_RANDOM_VIBRATION card, several shaker tests have been successfully correlated. The presentation will show issues encountered during correlations focusing specifically on management of damping.

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Increasing requirements for the car seat structures drive Faurecia Automotive Seating to increase FEA predictability regarding vibration tests. In scope of interest there is not only value of first resonance frequency but also higher frequency range or amplitude level for defined excitations.
Article will describe the methodology setup at Faurecia to extend the use of LS-Dyna to NVH Domain. Focusing efficiency in projects, approach is to derive NVH model from nonlinear crash model in order to give quick answer to design office for optimization based on Modal Analysis. Each typical mechanism for car seat like: tracks, recliners or high adjuster, fasteners (screws, bolts, welds or other kinematic connections) have been modified to reach linear behavior.
To validate NVH FEA models, several correlations with real tests have been performed following classical system engineering approach : small sub-systems like backrest, cushion, tracks and then complete assemblies like : seat frame, frame with headrest, trimmed complete seat. Modes shapes correlations between Real and Virtual Tests were done by calculating MAC (Modal Assurance Criterion) between modes calculated by LS-Dyna (d3eigv files) and modes extracted from Experimental Modal Analysis (Universal Files). Frequency Responses Functions (FRF) from hammer tests were also compared with Ls-dyna models using *FREQUENCY_DOMAIN_FRF cards.
Some OEM require also to respect some amplitudes level on seat frames while excited by ground signal (from theoretical acceleration spectrum to real life road signals). Using *FREQUENCY_DOMAIN_RANDOM_VIBRATION card, several shaker tests have been successfully correlated. The presentation will show issues encountered during correlations focusing specifically on management of damping.