Constitutive modeling of stress softening and permanent set in a porcine skin tissue: Impact of the storage preservation

Skin is a multilayered composite material and composed principally of the proteins collagen, elastic fibers and fibroblasts. The direction-dependent material properties of skin tissue is important for physiological functions like skin expansion. The current study has developed methods to characterize the directional biomechanical properties of porcine skin tissues as studies have shown that pigs represent a useful animal model due to similarities between porcine and human skin. It is observed that skin tissue has a nonlinear anisotropy biomechanical behavior, where the parameters of material modulus is 378 ± 160 kPa in the preferred-fiber direction and 65.96 ± 40.49 kPa in the cross-fiber direction when stretching above 30% strain equibiaxially. The result from the study provides methods of characterizing biaxial mechanical properties of skin tissue, as the collagen fiber direction appears to be one of the primary determinants of tissue anisotropy.

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Modeling of long-term fatigue damage of soft tissue with stress softening and permanent set effects

Biomechanics and Modeling in Mechanobiology ◽

10.1007/s10237-012-0431-6 ◽

2012 ◽

Vol 12 (4) ◽

pp. 645-655 ◽

Cited By ~ 14

Author(s):

Caitlin Martin ◽

Wei Sun

Keyword(s):

Soft Tissue ◽

Fatigue Damage ◽

Stress Softening ◽

Permanent Set

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A non-monotonous damage function to characterize stress-softening effects with permanent set during inflation and deflation of rubber balloons

International Journal of Engineering Science ◽

10.1016/j.ijengsci.2010.06.011 ◽

2010 ◽

Vol 48 (12) ◽

pp. 1937-1943 ◽

Cited By ~ 10

Author(s):

A. Elías-Zúñiga ◽

C.A. Rodríguez

Keyword(s):

Damage Function ◽

Stress Softening ◽

Permanent Set

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Local complex permittivity measurements of porcine skin tissue in the frequency range from 1 GHz to 15 GHz by evanescent microscopy

Physics in Medicine and Biology ◽

10.1088/0031-9155/54/3/015 ◽

2009 ◽

Vol 54 (3) ◽

pp. 699-713 ◽

Cited By ~ 9

Author(s):

Richard A Kleismit ◽

Gregory Kozlowski ◽

Brent D Foy ◽

Barbara E Hull ◽

Marian Kazimierczuk

Keyword(s):

Complex Permittivity ◽

Skin Tissue ◽

Frequency Range ◽

Porcine Skin ◽

Local Complex ◽

Permittivity Measurements

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Stress softening, strain localization and permanent set in the circumferential shear of an incompressible elastomeric cylinder

IMA Journal of Applied Mathematics ◽

10.1093/imamat/59.3.309 ◽

1997 ◽

Vol 59 (3) ◽

pp. 309-338 ◽

Cited By ~ 21

Author(s):

H. Huntley

Keyword(s):

Strain Localization ◽

Stress Softening ◽

Permanent Set

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Stress Softening in Natural Rubber Vulcanizates III. Carbon Black Filled Vulcanizates

Rubber Chemistry and Technology ◽

10.5254/1.3547069 ◽

1966 ◽

Vol 39 (5) ◽

pp. 1544-1552 ◽

Cited By ~ 3

Author(s):

J. A. C. Harwood ◽

A. R. Payne

Keyword(s):

Carbon Black ◽

Amplification Factor ◽

Mullins Effect ◽

Factor X ◽

Stress Strain ◽

Stress Softening ◽

Permanent Set ◽

Different Types ◽

Hydrodynamic Effects ◽

Natural Rubber Vulcanizates

Abstract This paper has confirmed the conclusions of the previous paper that the stress softening (Mullins effect) of a black-loaded vulcanizate is similar in magnitude to the stress softening of a gum rubber if the two vulcanizates are stretched initially to the same stress. The initial stress used in the present work was 180 kg/cm2, which is very near to the breaking stress of these vulcanizates. The similarity of the normalized stress-strain curves for all the vulcanizates, both gum and loaded with 60 phr of different types of black, suggests that the main difference between the stress-strain characteristics of a filled and a pure gum rubber, after the initial stressing cycle, can be accounted for by the strain amplification factor X. The more reinforcing blacks possess the higher X factors, i.e., they stiffen the rubber more than, for example, a fine thermal black. It is concluded that the black is acting mainly in a stiffening capacity due to the hydrodynamic effects of the degenerate carbon black networks. For sulfur crosslinked pure gum vulcanizates, in which the crosslinks are polysulfidic, the stress softening is partly associated with the breakage of polysulfide linkages. These reform in the extended condition and produce a real permanent set, but the major stress softening is attributed to the incomplete recovery of the crosslinked network to its initial random state due to network junctions or similar associations being displaced in a nonaffine way during extension. For example, junctions at the ends of chains which become fully extended at relatively low extensions will be displaced in this way. Thus when the rubber is subsequently strained, the network is already in a preferred disposition.

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Inflation of a Thick-Walled Shell Which Exhibits Stress Softening

Journal of Applied Mechanics ◽

10.1115/1.2789044 ◽

1998 ◽

Vol 65 (1) ◽

pp. 46-50 ◽

Cited By ~ 1

Author(s):

J. B. Haddow ◽

J. L. Wegner

Keyword(s):

Internal Pressure ◽

Strain Softening ◽

Complete Removal ◽

Mullins Effect ◽

Stress Softening ◽

Permanent Set ◽

Virgin State ◽

Rubberlike Material ◽

As Stress

The Mullins effect (Mullins, 1947), also known as stress softening, is exhibited by certain rubberlike materials and refers to changes of the mechanical properties, due to prior deformation. Johnson and Beatty (1995) have investigated the Mullins effect in equibiaxial tension by performing cycles of static inflation and deflation experiments on latex balloons. These experiments show that stress softening results in a decrease in the pressure necessary to inflate a balloon, and in addition, indicate inelastic effects of hysteresis and permanent set. The objective of this paper is to investigate the finite deformation static inflation from the virgin state, followed by quasi-static removal of the internal pressure, of a thick-walled homogeneous spherical shell composed of an incompressible isotropic rubberlike material which exhibits stress softening and permanent set. Since the initial inflation of the shell, due to application of an internal pressure, does not result in a homogeneous deformation, a state of residual stress is present after complete removal of the internal pressure. A procedure is presented for the determination of the response of the shell for the first cycle of inflation and deflation from the virgin state, and the analysis includes strain softening and the inelastic effects of hysteresis and permanent set. It is assumed that, for the initial static inflation of the shell from the virgin state, the internal pressure and stress distribution for a monotonically increasing internal or external radius are the same as for a hyperelastic shell, and also that the magnitude of the permanent set of an element of the material is related monotonically to the deformation at the end of the inflation.

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