Neural Network Based Constitutive Model Of Brain Tissue Considering Intravascular Pressure

Brain is one of the most complex and important tissues in human body.It has been shown that the stress state of brain tissues has a significant impact on the function of brain tissues,so it is important to study the mechanical behavior of brain tissues and further develop the constitutive model of brain tissues for the study of brain injury.However,the mechanical behavior of living brain tissue differs greatly from that of dead brain tissue.The main reason is that the introvascular pressure in brain tissue affects the mechanical behavior of brain tissue,and the introvascular pressure of blood vessels in the brain after brain death is different from that in living brain tissue.Artificial intelligence techniques and data science have made great progress in recent years and have penetrated to other fields.Several data-based constitutive modeling methods have been developed,and these methods have solved the problem of difficult constitutive modeling of some materials to a certain extent.In this paper,an artificial neural network based constitutive model for brain tissue considering introvascular pressure has been developed.In addition to building the constitutive model of brain tissue,the method can also be used to build the constitutive model of other anisotropic hyperelastic materials.The method can also be used to build the equivalent constitutive model of composite materials.First step is to generate the stress-strain data of the material using the representative volumn element method and homogenization method.A neural network is then trained with this data to obtain the mapping function from strain to stress.After that,the trained neural network replaces the conventional material constitutive model for finite element calculations.For the brain tissue,the representative volumn element models are built to obtain the brain white matter/gray matter with introvascular pressure.The artificial neural based brain tissue constitutive structure model can be obtained by measuring the mechanical behavior of the brain white matter/gray matter,overcoming the difficulty that the mechanical behavior of the living brain tissue hard to be measured.The method establishes an constitutive model with an analytic consistent tangential modulus matrix that can be embedded into commercial FEM software(user-defined material of ABAQUS)with high computational efficiency.The relationship between intravascular pressure and the mechanical behavior of brain tissue is investigated with the proposed model,which can be implied for the prediction of brain tissue damage and the investigation of the mechanism.