An Innovative Tool to Measure Human Skin Strain Distribution in Vivo using Motion Capture and Delaunay Mesh

2012 ◽  
Vol 28 (2) ◽  
pp. 309-317 ◽  
Author(s):  
J. Mahmud ◽  
S. L. Evans ◽  
C. A. Holt
Keyword(s):  
Finite Elements ◽  
Human Skin ◽  
Motion Capture ◽  
Strain Distribution ◽  
Field Strain ◽  
Full Field ◽  
Skin Deformation ◽  
Deformation Mechanics ◽  
Delaunay Mesh

AbstractSkin has a complex structure and its deformation mechanics is still not well defined. In the study of skin biomechanics, the stretch ratio, λ, is an important property, which is determined using strain data. This paper attempts to develop a novel tool by integrating experimental-numerical approach to measure full-field strain distribution of human skin in vivo. Skin deformation in vivo was measured using motion capture system, (which is not a full-field measuring tool) and then by constructing finite elements, its full-field strain contour is produced. The experimental procedure starts by attaching a set of reflective markers onto the skin at the forearm of healthy volunteers. Skin deformation is induced by pulling a nylon filament attached with a loading tab. Three infrared cameras are used to capture the movement of markers during load application. QTM (Qualisys, Sweden) software is used to track markers trajectories and generate data consisting of 3-dimensional markers coordinate. The initial capture is set as the reference marker positions (undeformed skin) and the subsequent images represent the deformed skin relative to the initial. Representing markers as nodes, finite elements are constructed by adjoining three adjacent markers using Delaunay mesh. Strains were deduced from the strain displacement matrix and measured for three subjects at three loading directions. The results are in fair agreement with those obtained by others. The method and output provide a useful addition to understanding skin deformation.

scholarly journals Material parameter identification using finite elements with time-adaptive higher-order time integration and experimental full-field strain information

2021 ◽  
Author(s):  
Stefan Hartmann ◽  
Rose Rogin Gilbert
Keyword(s):  
Experimental Data ◽  
Finite Elements ◽  
Parameter Identification ◽  
Material Parameter ◽  
Measurement Data ◽  
Least Square ◽  
Image Correlation ◽  
Field Strain ◽  
Material Parameter Identification ◽  
Full Field

AbstractIn this article, we follow a thorough matrix presentation of material parameter identification using a least-square approach, where the model is given by non-linear finite elements, and the experimental data is provided by both force data as well as full-field strain measurement data based on digital image correlation. First, the rigorous concept of semi-discretization for the direct problem is chosen, where—in the first step—the spatial discretization yields a large system of differential-algebraic equation (DAE-system). This is solved using a time-adaptive, high-order, singly diagonally-implicit Runge–Kutta method. Second, to study the fully analytical versus fully numerical determination of the sensitivities, required in a gradient-based optimization scheme, the force determination using the Lagrange-multiplier method and the strain computation must be provided explicitly. The consideration of the strains is necessary to circumvent the influence of rigid body motions occurring in the experimental data. This is done by applying an external strain determination tool which is based on the nodal displacements of the finite element program. Third, we apply the concept of local identifiability on the entire parameter identification procedure and show its influence on the choice of the parameters of the rate-type constitutive model. As a test example, a finite strain viscoelasticity model and biaxial tensile tests applied to a rubber-like material are chosen.

scholarly journals Exploratory Full-Field Strain Analysis of Regenerated Bone Tissue from Osteoinductive Biomaterials

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 168 ◽  
Author(s):  
Marta Peña Fernández ◽  
Cameron Black ◽  
Jon Dawson ◽  
David Gibbs ◽  
Janos Kanczler ◽  
...  
Keyword(s):  
Bone Regeneration ◽  
Bone Tissue ◽  
Bone Structure ◽  
Strain Analysis ◽  
Local Strain ◽  
Field Strain ◽  
Micro Computed Tomography ◽  
Promising Alternative ◽  
Full Field

Biomaterials for bone regeneration are constantly under development, and their application in critical-sized defects represents a promising alternative to bone grafting techniques. However, the ability of all these materials to produce bone mechanically comparable with the native tissue remains unclear. This study aims to explore the full-field strain evolution in newly formed bone tissue produced in vivo by different osteoinductive strategies, including delivery systems for BMP-2 release. In situ high-resolution X-ray micro-computed tomography (microCT) and digital volume correlation (DVC) were used to qualitatively assess the micromechanics of regenerated bone tissue. Local strain in the tissue was evaluated in relation to the different bone morphometry and mineralization for specimens (n = 2 p/treatment) retrieved at a single time point (10 weeks in vivo). Results indicated a variety of load-transfer ability for the different treatments, highlighting the mechanical adaptation of bone structure in the early stages of bone healing. Although exploratory due to the limited sample size, the findings and analysis reported herein suggest how the combination of microCT and DVC can provide enhanced understanding of the micromechanics of newly formed bone produced in vivo, with the potential to inform further development of novel bone regeneration approaches.

An optimized dynamic method for in vivo investigation through aspiration of the relaxation of human skin deformation

1985 ◽  
Vol 18 (7) ◽  
pp. 524
Author(s):  
P. Goliiski ◽  
D. Dimitrov ◽  
P. Stoyanov ◽  
N. Botev ◽  
A. Durmishev
Keyword(s):  
Human Skin ◽  
Dynamic Method ◽  
Skin Deformation

The Effect of the Loading Rate on the Full-Field Strain Distribution on the Surface on the Intervertebral Discs

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Ruspi Maria Luisa ◽  
Cristofolini Luca
Keyword(s):  
Strain Distribution ◽  
Loading Rate ◽  
Statistical Significance ◽  
Intervertebral Discs ◽  
Image Correlation ◽  
Field Strain ◽  
Strain Rates ◽  
Rate Dependency ◽  
Full Field ◽  
Loading Rates

Abstract Contrasting results are reported when the spine is tested at different strain rates. Tissue specimens from the ligaments or the intervertebral discs (IVD, including annulus fibrosus and nucleus pulposus) exhibit higher stiffness and lower dissipation at high strain rates. Counterintuitively, when spine segments are tested at high rates, the hysteresis area and loop width increase. It is unclear how the load is shared between the different structures at different loading rates. The hypotheses of this study were: (i) As the IVD stiffens at higher loading rates, the strain distribution around the disc would be different depending on the loading rate; (ii) Preconditioning attenuates the strain-rate dependency of the IVD, thus making differences in strain distribution smaller at the different rates. Six segments of three vertebrae (L4–L6) were extracted from porcine spines and tested in presso-flexion at different loading rates (reaching full load in 0.67, 6.7, and 67 s). The full-field strain maps were measured using digital image correlation on the surface of the IVDs from lateral. The posterior-to-anterior trends of the strain were computed in detail for each IVD, and compared between loading rates. The values and the direction of principal strain on the surface of the IVDs, vertebrae, and endplates remained unchanged at different rates. In the transition zone between IVD and vertebra, only slight differences due to the loading rate appeared but with no statistical significance. These findings will allow better understanding of the rate-dependent behavior and failure of the IVD.

Modeling the Anisotropic Properties of Human Skin Tissues

2012 ◽  
Author(s):  
Theresa M. Koys ◽  
Thao D. Nguyen
Keyword(s):  
Human Skin ◽  
Mechanical Response ◽  
Full Field ◽  
Anisotropic Properties ◽  
Biaxial Deformation ◽  
Field Displacement ◽  
Deformation State ◽  
Interface Modeling ◽  
Displacement Measurements

The anisotropic properties of human skin tissues are important for many applications, such as medical device/patient interface modeling. Typically, uniaxial [1] and biaxial [2] tests are used for mechanical testing of skin. The inflation method, less commonly used for skin, presents the advantages of imposing a biaxial deformation state more similar to that found in vivo. For methods that incorporate full-field displacement measurements, the material directions can be determined from the test rather than pre-selected prior to testing [3]. Furthermore, the mechanical response measured by the inflation method has been shown to be insensitive to preconditioning [4].

The full-field strain distribution and the evolution behavior during additive manufacturing through in-situ observation

2018 ◽  
Vol 150 ◽  
pp. 49-54 ◽  
Author(s):  
Ruishan Xie ◽  
Yue Zhao ◽  
Gaoqiang Chen ◽  
Xin Lin ◽  
Shuai Zhang ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Strain Distribution ◽  
Field Strain ◽  
In Situ Observation ◽  
Full Field ◽  
Evolution Behavior
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