A Simulation Approach for Identification and Design Optimization to Prevent Headrest Rattle

Squeak and rattle concerns account for approximately 10% of overall vehicle Things Gone Wrong (TGW) and are a major quality concern for automotive OEM’s. Seat is one of the major contributors of squeak and rattle issues observed in customer verbatim. Seat head rest rod and bezel are designed concentric to each other with a gap that allows free movement and a locking pin to position at different levels. Due to the design gap and weight of the head rest there is always tendency for relative displacement leading to rattle issues. Seat headrest, is close to the customer ear and any rattles at headrest will create annoying driving experience. Also, the contradictory requirements between efforts and rattle makes the scenario more difficult to fine tune the bezel specifications. The root cause for head rest rattle issues can also be related to free play between bezel and seat frame, free play between bezel and cap, looseness between locking pin and headrest rod etc. Identification of issue at physical testing is common practice subject to availability of test sample and road load data. Also, source identification and modification comes at the later part of the project. This paper establishes a process to perform the head rest rattle analysis by utilizing existing FE techniques. The FE analysis is performed using SNRD software available in hyper works platform. An older program seat FE model is built and validated with experimental results. Also, relative displacement measured between the headrest rod and bezel are correlated well with the simulation results. The occurrence and severity of rattle can be understood when the relative displacement is more than the design gap. Also, root cause analysis is performed by modal contribution analysis which gives an option for design sensitivity studies and compare relative displacements of different designs. The proposed methodology using FE techniques can help in identifying head rest rattle issues at early design stage.