【作者】 刘欣；

【导师】 任金东；

【作者基本信息】 吉林大学 ， 车身工程， 2024， 硕士

【摘要】 在科技与汽车行业蓬勃发展的今天,人们日益增长的高质量出行需求使得汽车座椅舒适性成为评价汽车乘坐体验好坏的关键性指标。采用物理测试评价样椅舒适性并进行迭代优化,耗费大量时间成本,因此需要一种更经济更高效的基于数字仿真的优化方法。将座椅开发与仿真技术相结合,通过精度较高的有限元模型进行仿真分析来降本增效成为了当代座椅开发的一大研究方向。为了提高仿真结果的精确度,本文建立基于中国中等身材男子人体尺寸的精细有限元模型,用于仿真人体入座和计算体压分布;采用结合简易座椅进行仿真计算和试验的方式验证了人体有限元模型的有效性和计算结果的准确性;通过实验统计研究了中等身材男子人体落座的胯点位置和坐姿规律,用于体压分布仿真中准确设置人体姿态和位置,提高体压分布计算的准确性。为了建立精准的人体有限元模型,基于中国最新第50百分位身高男性人体尺寸数据,建立了包含皮肤、软组织、骨骼、胸腹腔等部分的人体有限元模型。在Hyper Mesh软件中对人体软组织部分进行有限元网格划分时,采用分块划分的方式以得到尽可能多的高质量六面体网格。依据人体生物力学特性及人体节段质量数据,利用ABAQUS软件对人体各部分赋予相应的材料属性、定义装配。落座仿真结果与人的体重密切相关,因此对影响人体压力分布结果的体节质量进行了验证。基于简易座椅对模型装配后进行人-椅界面压力仿真,并开展验证试验。在验证中,作为承载人体有限元模型压力的座椅模型,其准确性对仿真结果的准确性影响重大。为了减少座椅模型精度带来的误差,本文选取简易座椅进行验证试验,并对其海绵材料建立了本构模型。由于海绵材料具有非线性、高回弹性、应力迟滞等力学特性,为了更好地描述其在受力与变形过程中的行为,在ABAQUS软件中采用Hyperfoam本构模型与Mullins效应对其进行定义。根据现行试验标准,对海绵材料进行了密度试验、单向压缩试验等,以准确获取本构模型所需的参数。通过对比仿真结果与试验结果验证了该人体模型用于体压分布计算的准确性。为了确保体压分布仿真计算过程中人体落座位置和姿态的准确性,开展了胯点位置和人体姿态统计实验。实验统计了在不同汽车布置参数时,驾驶员以舒适姿态落座后其胯点位置坐标及其相对于座椅H点的偏移量规律,并基于实验数据建立了胯点坐标偏移量的预测模型。同时,对定义姿态线的关键点及姿态参数进行计算,分析了姿态参数与车辆布置参数间的关联性。通过上述规律及数据分析,得到舒适落座姿态预测模型。最后,分析了测得的体压分布与实验参数的关联;对体压分布进行了分区计算,将分区处理后的压力分布参数与座椅设计参数、人体姿态参数进行分析,得到压力分布参数与座椅设计参数间的相关性结论,得出了姿态对压力分布参数的影响规律。更多还原

【Abstract】 With the booming development in general technology and automobile industry,people’s increasing demand for high-quality travel makes car seat comfort become a key index in evaluating the driving and seating quality of vehicle product.The traditional seat development mode of evaluation and optimization after prototype production indeed ensures the quality,but causes disadvantages of heavy consumes of time and cost.For this reason,it becomes a major research direction of contemporary seat development to combine the seat development and simulation technology in order to reduce cost and increase efficiency through using the high precision finite element model to conduct simulation and analysis.In order to improve the accuracy of the simulation results,in this paper a fine finite element model was established based on the body dimensions of an middle-sized Chinese male for simulating the human seating and the calculation of body pressure distribution.The effectiveness and accuracy of the human finite element model and its simulation results were validated through a combination of simulation calculations and experiments with a simplified seat.The hip point position and sitting posture patterns of an middle-sized Chinese male were studied through the experiment and statistical analyzed,which aiming to accurately set body postures and positions for simulating body pressure distribution and to improve the accuracy of pressure distribution calculations.In order to establish an accurate finite element model of human body,based on the latest human body anthropometry data of Chinese 50 th percentile male stature,a finite element model of human body including skin,soft tissue,bone,the cavity of chest and abdomen was established.To obtain as many high-quality hexahedral mesh as possible,the method of block partition was adopted in the finite element meshing of human soft tissue in Hyper Mesh software.The material properties of each body part were assigned and the whole model was assembled in ABAQUS,based on their biomechanical characteristics and human body segment mass data.Since the results of the seating simulation are closely related to human body mass,the segment mass that affects the results of human pressure distribution was verified.The assembled human body model was simulated for human-chair interface pressure based on the simple seat,and validation tests were carried out.In the validation test,the accuracy of the seat model,which carries the stress of the finite element model of the human body,has a great influence on the accuracy of the simulation results.In order to reduce the error caused by the accuracy of the seat model,a simple seat was selected for validation test,and the sponge materials constitutive model of the seat were established.The mechanical properties of sponge materials are nonlinear,high resilience and stress hysteresis.The Hyperfoam constitutive model and Mullins effect were used to define the sponges in ABAQUS in order to better describe their behavior during stress and deformation.According to the current test standards,density test and unidirectional compression test were carried out to obtain the parameters required by the constitutive model accurately.The accuracy of the human body model for calculating the body pressure distribution were verified by comparing the simulation results with the test results.To ensure the accuracy of human sitting position and posture during the simulation of body pressure distribution,a statistical experiment of hip point position and posture were carried out.In the experiment,the hip point position coordinate and its offset relative to H-point of the seat after the driver sat in a comfortable position under different car layout parameters were calculated,and a prediction model of hip-point coordinate offset was established based on these test data.Meanwhile,the key points of defining body pose line and body pose parameters were calculated,and the correlation between pose parameters and vehicle layout parameters were analyzed.Based on the above rules and data analysis,the comfortable sitting posture prediction model was established.Finally,the correlation between the measured body pressure distribution and the experimental parameters was analyzed.The body pressure distribution was calculated by partition,and the correlation between the pressure distribution parameters,seat design parameters and human posture parameters were analyzed,and the law of influence of posture on pressure distribution parameters was obtained.更多还原