Study On Compression Creep Characteristics Of Soft Cushion And Its Equivalent Prediction Method

Flexible polyurethane foam(also known as sponge)is comfortable in feeling and soft in texture,and because of its excellent mechanical processing performance,it's widely used in the production of all kinds of sofa cushions with a variety of wrapping material collocation.As the preferred material for the sofa cushion,its direct contact with human body,but creep and other viscoelastic behaviors will happen in a long period of time under static loading,and then results in performance failure.In this paper,the soft cushion mats made of sponge and cladding material were used as the object of study.Through a series of experiments,the compression creep characteristics of soft sand cushion mats were studied,then a mechanical model was developed to simulate the creep performance of soft cushions..And the time-stress equivalent model is used to predict the creep tendency of the specimens,which can help to evaluate the mechanical properties of cushion specimens.This paper has drawed the following conclusions:(1)To test the static compression deformation of different types of sponges,and the sponge load-displacement curves of different layers and hardness were recorded.Through the comparative analysis,the relationship between the deformation of sponge and the hardness,deformation and the number of layers were obtained under the weight of human body;(2)Different kinds of surface and different types of specimen sponge has carried on the short-term room temperature compression creep test,and the results show that the compressive creep curves of each specimen reflect the stress dependence,and both contain two stages: rapid growth and steady-state growth.The creep compliance curve was drawing further by the creep curve.And through the comparative analysis of various physical models,it is found that the six-element model based on Burgers model can better simulate the creep compliance curve and reflect compression creep properties.(3)Using the times-tress equivalence principle and put 7.89 Kpa as the reference stress,the main curve of the creep compliance under the stress is successfully translated.However,the translated curve can only show its trend of growth.(4)Drawing the stress-creep compliance curve at different time points,it can be seen that there is a linear relationship between the stress and creep compliance.By means of linear fitting,the creep compliance of any stress can be obtained at this point in time,and then the creep compliance curve under arbitrary stress is predicted.(5)Derived six-element model,the creep growth rates of different specimens can be acquire.Since the fluctuations of the experiment values has great influence on the parameters of the six component model,there is a great deviation between predicted growth rate and actual one.