A Nonlinear Viscoelastic Model for Adipose Tissue Representing Tissue Response at a Wide Range of Strain Rates and High Strain Levels

Abstract

Finite element human body models (FEHBMs) are nowadays commonly used to simulate pre- and in-crash occupant response in order to develop advanced safety systems. In this study, a biofidelic model for adipose tissue is developed for this application. It is a nonlinear viscoelastic model based on the Reese et al.'s formulation. The model is formulated in a large strain framework and applied for finite element (FE) simulation of two types of experiments: rheological experiments and ramped-displacement experiments. The adipose tissue behavior in both experiments is represented well by this model. It indicates the capability of the model to be used in large deformation and wide range of strain rates for application in human body models.

A numerical study on the safety belt‐to‐pelvis interaction

“…The material properties of adipose tissue are among parameters to be investigated in the lap belt‐to‐pelvis interaction. The previously developed material model 23 was used for adipose tissue and briefly introduced in this section. The rheological model is based on the generalised Maxwell viscoelastic model which consists of one elastic chain for equilibrium response (EQ) in parallel with N chains of Maxwell type (NEQ) for non‐equilibrium behaviour.…”

“…However, according to a previous study, 20 and were the most important parameters which have been selected for this study. Therefore, for brevity, the details of the evolution of viscous strain have been omitted here, readers are referred to References 20,23 for further information.…”

“…20 Therefore, the FE pelvis submodel which has been inspired by preliminary simulations using the SAFER HBM v9, 21,22 features only soft tissue (skin and subcutaneous adipose tissue), abdomen and the iliac crest of the pelvis as well as the interaction with the lap belt, Figure 1. The same material models and material parameters as for SAFER HBM v9 were selected for the FE pelvis submodel, except for adipose tissue that the material model developed in a previous work 23 was selected. The effect of disregarded neighbouring parts has been accounted for in boundary conditions as follows.…”

“…This region is between the lines X 1 and X 3 in Figure 2. Hence, regardless of parameter values, the slide of the belt does not occur anterior-inferior to the line X 1 while superior-posterior to the line X 3 it is T A B L E 1 The material parameters for adipose tissue 23…”

Experimental characterisation of porcine subcutaneous adipose tissue under blunt impact up to irreversible deformation

“…Despite these extensive studies on adipose tissue mechanics, some physical effects and the corresponding material characteristics still require further investigations. Proposing a computational model, Naseri et al identified a lack of experimental data in a testing regime combining large deformation and high testing velocities [ 44 ]. Comley and Fleck examined the uniaxial compressive behaviour of subcutaneous adipose tissue for different strain rates between 0.002 and 5700 s −1 and Grigoriadis investigated the material response of the heel fat pad for different strain rates up to 150 s −1 using a drop rig [ 27 , 33 ].…”