BIOMECHANICAL MODELLING OF THE HUMAN SKULL STRESS STATE UNDER IMPACT BY CYLINDRICAL SOLID

Abstract

Skull fractures are quite often observed in victims of falls, traffic accidents, attacks with the use of bats and rods. The aim of the study is to assess the stress-strain state of the human head under impact on the basis of finite element modelling. The impact is applied to the frontal region of the frontal bone by the middle part and the end of a cylindrical solid (a rod). The solid is differently oriented with respect to the in relation to the Frankfurt plane. The head model includes the epidermis (skin), bone structures of the skull, bone structures of the lower jaw, eyeballs, teeth, meninges (dura, arachnoid and pia mater), cerebrum (white and gray matter), cerebellum, brain stem, muscles and ligaments. The elements of the human head model are described by the models of a linearly elastic material, a viscoelastic incompressible material, an elastic-plastic material considering fracture, and a hyper-elastic material. The eyeballs are assumed as absolutely rigid. The finite element analysis was carried out for different values of the initial velocity of a rod, corresponding to the moment of its contact with the skin of the head. It was found out that the maximum equivalent stresses and deformations of the skull bone structures occur under impact by the middle part of the rod compared to impact by its end. The impact action of the rod leads to the maximum equivalent stresses if the rod is located at an angle of 60° to the vertical. The region of the maximum stresses is located at the intersection of the sagittal and coronal sutures, and to a greater extent, significant stresses are observed along the coronal suture. The results obtained can be used by experts in the field of forensic science to evaluate various scenarios for the occurrence of traumatic brain injury and substantiate further forensic investigations.