Research of Contact Stresses between Seat Cushion and Human Body

Design optimization of seat cushions is associated with the need to investigate their softness using, for this purpose, various kinds of loading pads. The aim of the investigation was: to determine seat cushion stiffness of a chair selected from a set of dining-room furniture, to determine values and distributions of contact strains on the seat surface caused by loading pad of different hardness, numerical calculation of contact strains between the seat cushion and the loading pad and to verify the results of these calculations with the results of laboratory experiments. The performed tests showed that the assessment of the seat cushion stiffness and the evaluation of contact stresses on their surface should be carried out using an equally stiff loading pad. In numerical calculations, polyurethane foams should be modeled as hyperfoam bodies of σ=f(ε) characteristics determined in an axial compression test. Contact stresses between the seat cushion and the user’s body should be reduced as a result of application of a frictionless connection of thin layers of polyurethane foams with foam forming the proper elastic layer of the seat.