Numerical Study On The Mechanical Response Of Brain Under The Impact Loading Based On Elastic-viscoelastic Model

As Chinese economic strength has been improved,the standards of living of our country people have greatly improved.In recent years,with the increasing of car ownership per capital,the increasingly multifarious traffic accidents still cause heavy casualties and numerous enormous losses.Head injury is the most common injury in traffic accidents.It has attracted the attention of all countries in the world,because of its high mortality and high disability.Brain injury has two common mechanisms.First,the impact load directly acted on the head,which caused brain damage.Second,the relative displacement between the skull and the brain tissues caused brain injury.We have been set up two kinds of mechanical models of the human brain under the impact loading.One is the hard material on the soft substrate,which is like the human brain.The other is two dimensional human brain model during in the impact process,which is based on Maxwell model.In this thesis,these two kinds of brain injury mechanisms have been studied by the method of the mechanical model.The mechanical response to brain on the impact process,and the relationship of brain injury and load are investigated relatively rarely due to the complexity of brain.This paper represents a mechanical model for analyzing the brain impact injury.From the perspective of biomechanics,the model being considered is that the skull of hard material is based on the brain tissue of soft substrates.The impact loading is treated as the concentrated force on the hard material.The elastic-viscoelastic correspondence principle is used to obtain analytic solutions for the case when the brain tissue is considered as viscoelastic solid.In this thesis,the mechanical response of brain injury is determined,as well as the relationship between brain injury and impact load.This mechanical model can be applied to simulate and analyze the skull damage,and in a good agreement with experimental results.The derived formulas can be used to obtain the value of stress under the impact on the brain and estimate the extent of brain injury.Based on the interesting and rational mechanical model,it can be applied in designing the reasonable equipment for protecting brain structure and evaluating the degree of brain injury by analyzing the stress area.In this thesis,we have established two-dimensional mechanical model of brain impact system,which is based on the Maxwell model,to study the relative displacement between the skull and the brain tissues.This model can be used to analyze the relative motion between the skull and the brain tissues,and can get the expression of relative displacement with the impact time.On the one hand,this paper analyzes and discusses the maximum value of relative displacement under the different natural frequencies of human head.On the other hand,this paper also analyzes how to improve the impact resistance of human head.This mechanical model is presented to illustrate the feasibility and validity,which is compared with the previous model based on the Kelvin model.The research of this paper has provided a theoretical reference for the analysis of relative displacement of skull and brain tissues.