Development/global validation of a 6-month-old pediatric head finite element model and application in investigation of drop-induced infant head injury

Drop is a frequent cause for infant head injury. To date, finite element (FE) modeling was gradually used to investigate child head dynamic response under drop impact conditions, however, two shortages still exist on this topic: (1) due to ethical reasons, none of developed 6-month-old (6MO) head FE model was found to be quantitatively validated against child cadaver tests at similar age group; (2) drop height and impact surface stiffness effects on infant head responses were not comprehensively investigated. In this study, motivated by the recently published material properties of soft tissues (skull and suture, etc.) and reported pediatric head global cadaver tests, a 6MO child head FE model was developed and simulated results compared with the child cadaver experimental data under compression and drop conditions. Comparison of results indicated that the FE model showed a fairly good biofidelic behavior in most dynamic responses. The validated FE model was further used to investigate effects of different drop heights and impact surface stiffness on the head dynamic responses. Numerical results show that the pediatric head mechanical parameters (peak acceleration, HIC, maximal vonMises stress and maximal first principal strain of skull) keep increasing with the increase in drop height, and exhibit “logarithmic function” shapes at “fast–slow” trends with increase in impact surface stiffness. Based on above analysis, the regressions were conducted to describe the relationship between drop height and impact surface stiffness and head global injury predictors (head peak acceleration, HIC, etc.). This paper provides a fundamental study of child head injury mechanism and protection under drop conditions.     

Using three-dimensional finite element analysis in time domain to model railway-induced ground vibrations

For the prediction of ground vibrations generated by railway traffic, finite element analysis (FEA) appears as a competitive alternative to simulation tools based on the boundary element method: it is largely used in industry and does not suffer any limitation regarding soil geometry or material properties. However, boundary conditions must be properly defined along the domain border so as to mimic the effect of infinity for ground wave propagation. This paper presents a full three-dimensional FEA for the prediction of railway ground-borne vibrations. Non-reflecting boundaries are compared to fixed and free boundary conditions, especially concerning their ability to model the soil wave propagation and reflection. Investigations with commercial FEA software ABAQUS are presented also, with the development of an external meshing tool, so as to automatically define the infinite elements at the model boundary. Considering that ground wave propagation is a transient problem, the problem is formulated in the time domain. The influence of the domain dimension and of the element size is analysed and rules are established to optimise accuracy and computational burden. As an example, the structural response of a building is simulated, considering homogeneous or layered soil, during the passage of a tram at constant speed.     

基于接触模型的球头挂环仿真分析与优化方法研究

球头挂环作为输电线路的关键部件,起到保证输电线路安全运行的作用。为了对 球头挂环进行优化研究,在顺风向水平力作用下,基于Abaqus 有限元软件对球头挂环进行了 非线性静力仿真分析,通过建立2 种不同型号的球头挂环接触模型,设置不同的网格密度、接 触面宽度,接触类型采用面-面接触,讨论了球头挂环尺寸、网格密度和接触面宽度对最大应力 的影响规律。计算结果表明,2 种型号球头挂环在不同网格密度下的接触宽度与最大应力变化 规律基本相同,最大应力值随着接触面宽度的增大而逐渐减小,可分为急速下降区、缓慢下降 区、平稳区3 个阶段。平稳区的最大应力及波动幅度均较小,可作为理想的球头挂环接触面宽 度,其可为今后球头挂环的优化设计提供理论指导依据。