자동차용 시트 폼의 시간 의존적 거동 예측을 위한 수치해석

초록

Generally, numerical approaches of evaluation for vehicle seat comfort have been studied withoutconsidering time-dependent characteristics and the only seating moment have been considered in seat design. However,the comfort not only at the seating moment but also in the long-term should be evaluated because the passengers aresitting repeatedly on the seat to drive the vehicle for hours. So, the aim of this paper is to carry out a quantitative evaluationof the time-dependent mechanical characteristics of seat foams and to suggest a process for predicting theviscoelastic deformation of seat foam in response to long-term driving. To characterize the seat materials, uniaxialcompression and tension tests were carried out for the seat foam and stress relaxation tests were performed forevaluating the viscoelastic behavior of the seat foam. A unit solid element model was used to verify the reliability of thematerial model with respect to the compression behavior of the seat foam. It is not straightforward to evaluate thetime-dependent compression of foams using the explicit solver because the viscoelastic material model is limited. Touse the explicit solver, the material model must be modified using stress-degradation data. Normalized stress relaxationmoduli were added to the stress-strain curves obtained under static conditions to achieve a time-dependent set ofstress-strain relations that were compatible with the implicit solver. There was good agreement between the analysisresults and experimental data.

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