Now showing 1 - 4 of 4
  • Publication
    Dynamic Tensile Properties of Human Skin
    (International Research Council on the Biomechanics of Injury, 2012) ; ; ;
    The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. Studies have shown that the anisotropic effects of skin have been linked to sample orientation with respect to contour lines of tension, i.e. the Langer’s lines. There have been numerous studies undertaken to calculate the influence of Langer’s lines on the mechanical properties of human skin at quasistatic strain rates; however, it is relatively unknown what occurs at dynamic speeds. This study conducts a number of dynamic mechanical tensile tests to investigate the influence dynamic speeds have on the mechanical properties of human skin. The testing protocol involves uniaxial tensile tests at three different dynamic speeds, 1m/s, 1.5m/s and 2m/s, performed using an Instron tensile test machine. A total of 33 tests were conducted on 3 human cadavers aged 85, 77 and 82. Samples were excised at specific locations and orientations with respect to the Langer’s lines. The purpose for this was to recognise the significance that location and orientation have on the mechanical properties of human skin. The mean ultimate tensile strength (UTS) was 27.2±9.3MPa, the mean strain energy was 4.9±1.5MJ/m3, the mean elastic modulus was 98.97±97MPa and the mean failure strain was 25.45±5.07%. This new material data for human skin can be applied to constitutive models in areas such as impact biomechanics, forensic science and computer‐assisted surgery.
      2787
  • Publication
    Characterization of the anisotropic mechanical properties of excised human skin
    The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. In this study, we have investigated the influence of location and orientation on the deformation characteristics of 56 samples of excised human skin. Uniaxial tensile tests were carried out at a strain rate of 0.012 s−1 on skin from the back. Digital Image Correlation was used for 2D strain measurement and a histological examination of the dermis was also performed. The mean ultimate tensile strength (UTS) was 21.6±8.4 MPa, the mean failure strain 54%±17%, the mean initial slope 1.18±0.88 MPa, the mean elastic modulus 83.3±34.9 MPa and the mean strain energy was 3.6±1.6 MJ/m3. A multivariate analysis of variance has shown that these mechanical properties of skin are dependent upon the orientation of the Langer lines (P<0.0001−P=0.046). The location of specimens on the back was also found to have a significant effect on the UTS (P=0.0002), the elastic modulus (P=0.001) and the strain energy (P=0.0052). The histological investigation concluded that there is a definite correlation between the orientation of the Langer lines and the preferred orientation of collagen fibres in the dermis (P<0.001). The data obtained in this study will provide essential information for those wishing to model the skin using a structural constitutive model.
      306Scopus© Citations 422
  • Publication
    Automated Estimation of Collagen Fibre Dispersion in the Dermis and its Contribution to the Anisotropic Behaviour of Skin
    Collagen fibres play an important role in the mechanical behaviour of many soft tissues. Modelling of such tissues now often incorporates a collagen fibre distribution. However, the availability of accurate structural data has so far lagged behind the progress of anisotropic constitutive modelling. Here, an automated process is developed to identify the orientation of collagen fibres using inexpensive and relatively simple techniques. The method uses established histological techniques and an algorithm implemented in the MATLAB image processing toolbox. It takes an average of 15 s to evaluate one image, compared to several hours if assessed visually. The technique was applied to histological sections of human skin with different Langer line orientations and a definite correlation between the orientation of Langer lines and the preferred orientation of collagen fibres in the dermis (p<0.001,R2=0.95) was observed. The structural parameters of the Gasser–Ogden–Holzapfel (GOH) model were all successfully evaluated. The mean dispersion factor for the dermis was κ=0.1404±0.0028. The constitutive parameters μ, k 1 and k 2 were evaluated through physically-based, least squares curve-fitting of experimental test data. The values found for μ, k 1 and k 2 were 0.2014 MPa, 243.6 and 0.1327, respectively. Finally, the above model was implemented in ABAQUS/Standard and a finite element (FE) computation was performed of uniaxial extension tests on human skin. It is expected that the results of this study will assist those wishing to model skin, and that the algorithm described will be of benefit to those who wish to evaluate the collagen dispersion of other soft tissues.
      289Scopus© Citations 131
  • Publication
    Automated Estimation of Collagen Fibre Dispersion in the Dermis and its Contribution to the Anisotropic Behaviour of Skin
    Collagen fibres play an important role in the mechanical behaviour of many soft tissues. Modelling of such tissues now often incorporates a collagen fibre distribution. However, the availability of accurate structural data has so far lagged behind the progress of anisotropic constitutive modelling. Here, an automated process is developed to identify the orientation of collagen fibres using inexpensive and relatively simple techniques. The method uses established histological techniques and an algorithm implemented in the MATLAB image processing toolbox. It takes an average of 15 s to evaluate one image, compared to several hours if assessed visually. The technique was applied to histological sections of human skin with different Langer line orientations and a definite correlation between the orientation of Langer lines and the preferred orientation of collagen fibres in the dermis (p<0.001,R 2 =0.95) was observed. The structural parameters of the Gasser–Ogden–Holzapfel (GOH) model were all successfully evaluated. The mean dispersion factor for the dermis was κ=0.1404±0.0028. The constitutive parameters μ, k 1 and k 2 were evaluated through physically-based, least squares curve-fitting of experimental test data. The values found for μ, k 1 and k 2 were 0.2014 MPa, 243.6 and 0.1327, respectively. Finally, the above model was implemented in ABAQUS/Standard and a finite element (FE) computation was performed of uniaxial extension tests on human skin. It is expected that the results of this study will assist those wishing to model skin, and that the algorithm described will be of benefit to those who wish to evaluate the collagen dispersion of other soft tissues.
      551Scopus© Citations 131