Biomedical Engineering Reference
In-Depth Information
Chapter 6
Mechanical Interactions
Abstract Interaction simulations of body support devices generated in Chap. 4
and human B
OSS
-Models as introduced in Chap. 5 are presented. The effects of
body supports on tissue, in terms of internal tissue stress and strain, are evaluated.
After the pressure sore problem is discussed, finite element model verifications are
presented based on the interaction simulation of a human buttocks model and a
soft foam support (Sect. 6.2). Finite element analysis of elastic and viscoelastic
interaction between human B
OSS
-Models and comfort and anti-pressure sore
supports as well as automotive and aircraft seats (Sect. 6.3) are described. Tissue
stress and strain distribution at various contact body sites at the skin level and the
fat-muscle interface and at the bone surface are evaluated and compared. Simu-
lation results are compared to findings provided in the literature (Sect. 6.4).
6.1 Introduction
Numerical methods, for instance the finite element method (FEM), not only pro-
vide insight into the stress-strain state of tissue under mechanical loading, but also
allow evaluation of the effects of different support designs on the incumbent body.
Thus, by quantifying mechanical tissue stress, predictions about the adequacy of
the particular support can be made, as has previously been performed by others
Todd and Thacker (1994) or Oomens et al. (2001). Using the FE-method, from a
mechanical point of view, the stress-strain state within the loaded tissue mainly
depends on (a) the choice of soft tissue material parameters, (b) the body support
material and design, as well as (c) the modelling of the anatomical structures. Soft
tissue material parameters used here represent in vivo human gluteal skin/fat and
in vivo human passive (and transversally loaded) muscle tissue properties. They
have been derived via a combined iterative numerical-experimental approach
based on in vivo non-invasive testing on human subjects, as described in detail in
