A limitation in virtually all planar biaxial studies of soft tissues has been the inability to include the effects of in-plane shear. This is due to the inability of current mechanical testing devices to induce a state of in-plane shear, due to the added cost and complexity. In the current study, a straightforward method is presented for planar biaxial testing that induces a combined state of in-plane shear and normal strains. The method relies on rotation of the test specimen’s material axes with respect to the device axes and on rotating carriages to allow the specimen to undergo in-plane shear freely. To demonstrate the method, five glutaraldehyde treated bovine pericardium specimens were prepared with their preferred fiber directions (defining the material axes) oriented at 45 deg to the device axes to induce a maximum shear state. The test protocol included a wide range of biaxial strain states, and the resulting biaxial data re-expressed in material axes coordinate system. The resulting biaxial data was then fit to the following strain energy function W:  
W=c/2[exp(A1E112+A2E222+2A3E11E22+A4E122+2A5E11E12+2A6E22E12)1]
where E′ij is the Green’s strain tensor in the material axes coordinate system and c and Ai are constants. While W was able to fit the data very well, the constants A5 and A6 were found not to contribute significantly to the fit and were considered unnecessary to model the shear strain response. In conclusion, while not able to control the amount of shear strain independently or induce a state of pure shear, the method presented readily produces a state of simultaneous in-plane shear and normal strains. Further, the method is very general and can be applied to any anisotropic planar tissue that has identifiable material axes.
1.
Billiar
K.
, and
Sacks
M.
,
1997
, “
A method to quantify the fiber kinematics of planar tissues under biaxial stretch
,”
Journal of Biomechanics
,
30
(
7)
:
753
756
.
2.
Billiar, K., and Sacks, M., 1998, “Biaxial mechanics of fresh and glutaraldehyde treated porcine aortic valve cusps,” ASME JOURNAL OF BIOMECHANICAL ENGINEERING, submitted.
3.
Brossollet
L. J.
, and
Vito
R. P.
,
1996
, “
A new approach to mechanical testing and modeling of biological tissues, with application to blood vessels
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
118
:
433
439
.
4.
Chew
P. H.
,
Yin
F. C. P.
, and
Zeger
S. L.
,
1986
, “
Biaxial Stress-Strain Properties of Canine Pericardium
,”
Journal of Molecular and Cell Cardiology
,
18
:
567
578
.
5.
Choi
H. S.
, and
Vito
R. P.
,
1990
, “
Two Dimensional Stress-Strain Relationship for Canine Pericardium
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
112
:
153
159
.
6.
Flynn
D.
,
Peura
G.
,
Grigg
P.
, and
Hoffman
A.
,
1998
, “
A finite element based method to determine the properties of planar soft tissue
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
120
:
202
210
.
7.
Fung, Y., 1965, Foundations of Solid Mechanics, Prentice-Hall, Englewood Cliffs, NJ.
8.
Fung, Y. C., 1993, Biomechanics: Mechanical Properties of Living Tissues, Springer-Verlag, New York.
9.
Humphrey
J.
,
Kang
T.
,
Sakarda
P.
, and
Anjanappa
M.
,
1993
, “
Computer-Aided Vascular Experimentation: A New Electromechanical Test System
,”
Annals of Biomedical Engineering
,
21
:
33
43
.
10.
Humphrey, J., Strumpf, D., and Yin, F. C. P., 1989, “Biaxial experimental data on excised ventricular epicardium,” ASME 1989 Advances in Bioengineering, 197–198.
11.
Humphrey
J. D.
,
Strumpf
R. K.
, and
Yin
F. C. P.
,
1990
, “
Determination of a Constitutive Relation for Passive Myocardium: II—Parameter Estimation
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
112
:
340
346
.
12.
Humphrey
J. D.
,
Strumpf
R. K.
, and
Yin
F. C. P.
,
1992
, “
A Constitutive Theory for Biomembranes: Application to Epicardial Mechanics
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
114
:
461
466
.
13.
Khalsa
P.
,
Hoffman
A.
, and
Grigg
P.
,
1996
, “
Mechanical states encoded by stretch-sensitive neurons in feline joint capsule
,”
Journal of Neurophyslology
,
76
(
1)
:
175
187
.
14.
Lanir
Y.
, and
Fung
Y. C.
,
1974
, “
Two-Dimensional Mechanical Properties of Rabbit Skin—I. Experimental System
,”
Journal of Biomechanics
,
7
:
29
34
.
15.
Lee
J. M.
, and
Boughner
D. R.
,
1981
, “
Tissue Mechanics of Canine Pericardium in Different Test Environments
,”
Circulation Research
,
49
:
533
544
.
16.
Lee
M.
,
LeWinter
C.
,
Freeman
G.
,
Shabetai
R.
, and
Fung
Y. C.
,
1985
, “
Biaxial Mechanical Properties of the Pericardium in Normal and Volume Overload Dogs
,”
American Journal of Physiology
,
249
:
H222–H230
H222–H230
.
17.
Nielsen
P. M. F.
,
Hunter
P. J.
, and
Smaill
B. H.
,
1991
, “
Biaxial Testing of Membrane Biomaterials: Testing Equipment and Procedures
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
113
:
295
300
.
18.
Press, W. H., Flannery, B. P., Teukolsky, S. A., and Vetterling, W. T., 1988, Numerical Recipes in C, Cambridge University Press, Cambridge.
19.
Sacks
M. S.
, and
Chuong
C. J.
,
1993
, “
Biaxial mechanical properties of passive right ventricular free wall myocardium
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
115
:
202
205
.
20.
Sacks
M. S.
,
Smith
D. B.
, and
Hiester
E. D.
,
1997
, “
A SALS device for planar connective tissue microstructural analysis
,”
Annals of Biomedical Engineering
,
25
(
4)
:
678
689
.
21.
Sacks, M., 1998, “A structural model for natural and chemically treated bovine pericardium,” in: Modeling and Simulation Based Engineering, Atlanta, GA, Tech Science Press, 1574–1579.
22.
Sacks, M., and Billiar, K., 1998, “Biaxial Mechanical Behavior of Bioprosthetic Heart Cusps Subjected to Accelerated Testing,” Advances in Anticalcific and Antidegenerative Treatment of Heart Valve Bioprostheses, Chap. 3, S. Gabbay and R. Frater, eds., Silent Partners, Austin.
23.
Sacks, M., and Chuong, C., 1998, “Orthotropic mechanical properties of chemically treated bovine pericardium,” Annals of Biomedical Engineering, 26(5).
24.
Sacks, M., Gloeckner, D., Chancellor, M., deGroat, W., and Schneck, F., 1999, “Biaxial mechanical properties of the urinary bladder wall,” presented at the ASME Summer Bioengineering Conference, Big Sky, MN.
25.
Yin
F. C. P.
,
Chew
P. H.
, and
Zeger
S. L.
,
1986
, “
An Approach to Quantification of Biaxial Tissue Stress-Strain Data
,”
Journal of Biomechanics
,
19
:
27
37
.
26.
Yin
F. C. P.
,
Strumpf
R. K.
,
Chew
P. H.
, and
Zeger
S. L.
,
1987
, “
Quantification of the Mechanical Properties of Noncontracting Canine Myocardium Under Simultaneous Biaxial Loading
,”
Journal of Biomechanics
,
20
:
577
589
.
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