Abstract
The purpose of this study is to find the design tool to create a soft tissue 3D model able to be used for finite element analysis to simulate the facial soft tissue deformation under g-loading and the helmet and mask/tissue interaction. Such a model will be of value in the design of new helmets and oxygen mask system, to reduce the effects of inertia, to provide improved fit, to minimise oxygen leakage especially when deformed under high g-loading. This work is concerned with the creation of a 3D geometric model. Further work may involve the measurement of mechanical properties of the facial soft tissue, finite element analysis and validation of the model. Using high frequency A-scan ultrasound allows the superficial tissue to be measured on volunteers without risk. The investigation covers 112 points on half of the face, linked to 11 defined morphological zones. The zonal boundaries are based on previous research and are initially identified by inspection and palpation of the face. There is large thickness range difference (30%) over the face in most zones defined in an individual. The iso-thickness zone hypothesis is not valid if the 'constant' thickness criterion is set to be 10% for all zones. Software algorithm for automatically detecting the facial soft tissue thickness is developed and validated to be effective (5% fail rate). Thickness data is acquired from European white males, females and Chinese males. The data collected in this study is also useful in forensic science for facial reconstruction purpose. Laser scanning method has been used to obtain the facial surface profile to create a surface model into which the soft tissue layer thickness distribution around the face can be incorporated. The surface model is exported in IGES format and can be imported in CAD software. Electromagnetic space locating method is used to acquire the ultrasound probe position so as to find the position of the tissue thickness. Point-based registration method is used to integrate the ultrasound thickness data into the laser scanned surface model to create a soft tissue shell solid model. The model is exported in IGES data format so that it can be imported into a finite element analysis package for further processing.