| Due to the influence of modern office forms,more and more workers have become one of the "sitting people".From the perspective of "ergonomics",sitting posture for a long time will lead to soft tissue deformation of human buttocks due to too long stress,which will lead to a series of diseases,such as bedsore and lumbar muscle strain.Combined with the posture that most people choose to sit or lie down at rest,it is an inevitable trend to design elastic cushion products that meet human comfort.It is understood that the contact between human buttocks and elastic cushions made of different materials in sitting posture will be subjected to different degrees of pressure,and the soft tissues will be deformed to different degrees.The design of cushion materials and structures will directly affect the comfort of human buttocks.Therefore,this paper will aim at relieving human body pressure and improving comfort,and design products from two aspects: material selection and thickness dimension of elastic cushion.By using the research method of finite element simulation,the suitable design scheme of elastic cushion is provided to groups with different contact requirements for elastic cushion products.This paper mainly explores from four aspects:Select the suitable elastic filling materials for the seat cushion,and analyze the mechanical properties of each elastic material and its related simulation experiments.Firstly,based on the research bac kground,research status at home and abroad and the investigation and analysis of the existing elastic cushion products in the market,six kinds of elastic filling materials-three traditional elastic materials: 28 kg/cm3 medium density sponge,50 kg/cm3 high-density foam and latex,and three new elastic materials-TPEE,warp-knitted spacer fabric and POE are selected.Then,the mechanical properties of six kinds of elastic materials were tested.After the test data were obtained,the compression experiment process of six kinds of elastic materials was simulated by finite element technology.The simulated stress-strain data under different constitutive models such as YEOH,LOW DENSTIY and OGDEN were co MPared with the actual compression experiment data,and the constitutive model with the highest fitting degree of each elastic material was selected as LOW DENSTIY.Finally,the micro-element deformation simulation experiment of each elastic material is studied,and the mathematical model between the deformation of each elastic material and the thickness of the material and the applied pressure is obtained.(1)Analyze and co MPare the distribution of body pressure on the cushion surface after the buttocks contact with each single elastic material cushion,so as to provide help for the subsequent distribution design of elastic combined cushion at all levels.Firstly,a composite model of hip soft tissue and bones and an elastic cushion model are established in the sitting state of human body.The size of human hip model is based on the 500 percentile data of Chinese men,and the size of cushion model is 600 mm×600 mm;The mesh of each model is divided by HYPERMESH software,and the material properties,boundary conditions and loads of the finite element model are set after being imported into ABAQUS.Then the contact process between the hip model and a single cushion model filled with 28 kg/cm3 medium density sponge,50 kg/cm3 high-density foam,latex,TPEE,warp-knitted spacer fabric and POE was simulated.By co MParing the distribution of human body pressure on each cushion surface,it is found that the stress on the cushion surface of 28 kg/cm medium density sponge and latex is small,the stress on the cushion surface of TPEE and warp knitted spacer fabric is moderate and uniform,the stress on the cushion surface of 50 kg/cm high-density foam is large,and the stress on the cushion surface of POE is the largest.In order to verify the validity of the simulation results,a pressure tester is used to verify the data.The tester shows that the relative error of the peak pressure data of each cushion surface is less than 5 %,which proves that the simulation experiment method is feasible.Finally,in order to provide more favorable data support before design,subjective evaluation is essential;The subjective evaluation results show that the contact feeling of medium density sponge and latex elastic cushion is soft,TPEE elastic cushion and warp-knitted spacer fabric elastic cushion are moderate,while the contact feeling of high-density foam elastic cushion is hard at 50 kg/cm3,and the contact feeling of POE elastic cushion is very hard,among which TPEE,warp-knitted spacer fabric and POE have better support and air permeability.However,considering the economic applicability of elastic materials,the final elastic material with soft contact feeling is 28 kg/cm medium density sponge,the elastic material with moderate contact feeling is warp knitted spacer fabric,the elastic material with hard contact feeling is 50kg/cm high-density foam,and the elastic material with very hard contact feeling is POE.The subjective evaluation is consistent with the objective data,so this part of the conclusion can provide reference for the subsequent design scheme of the combination pad.(2)Six kinds of combined cushion schemes with different levels are designed based on the different requirements of docking tactile sensation,and the pressure distribution on the cushion surface after the buttocks contact with the combined cushion under the six schemes is analyzed.Firstly,a market survey was conducted on the demand of combined cushion products.The results showed that most users needed good air permeability and versatility for cushion performance.In terms of contact softness and hardness of cushions,different users have great differences,which are mainly divided into four types: soft,moderate,hard and very hard.Therefore,the scheme design of the combined cushion is mainly based on the four needs of contact feeling.Combined with the characteristics of four elastic materials,six kinds of combined cushion schemes with different levels were designed.Then,the contact process between the buttocks and the elastic combined cushion under the six schemes was simulated and the results were analyzed.Finally,four kinds of combined elastic cushion schemes with different contact feelings were designed according to the air permeability of the materials.In order to maximize the economic applicability of the product,the thickness of each layer of the combined cushion under four schemes is designed;The deformation of each layer of the combined cushion under the four schemes is analyzed,and finally the minimum thickness size of each layer in the combined cushion suitable for the special group of China male 50 percentile when using the four schemes is obtained.(3)Optimize the product design of the multi-purpose elastic combination pad.In order to realize the versatility of the products,based on the different usage scenarios,three kinds of elastic combination cushion products are designed: tea ceremony futon combination cushion,"infinite Rubik’s cube" ever-changing combination cushion and folding combination mattress.The process of using three kinds of products by 50 percent male users in China was simulated respectively,and the distribution of body pressure on the cushion surface was analyzed.In the product design part of folding combined mattress,the reco mmended pillow height suitable for China 50 percentile men with different head and neck shapes is provided,which provides reference for future pillow product design.To sum up,this topic uses finite element technology,analyzes the distribution of human body pressure on the surface of elastic cushion,and provides a comprehensive and targeted design scheme of multi-purpose elastic combination cushion that meets the different needs of 500 percentile men in China based on contact degree,so as to provide help for the future design of elastic combination cushion products. |
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