This paper presents a method to determine the contact force and pressure on the surface of viscoelastic objects grasped by an endoscopic grasper, used in Minimally Invasive Surgery (MIS). Normally, an endoscopic grasper is corrugated (teeth-like) in order to grasp slippery tissues. It is highly important to avoid damage to the tissues during grasping and manipulation in endoscopic surgery. Therefore, it is essential to determine the exact contact force on the surface of the tissue. To this end, initially a comprehensive closed form analysis of grasping contact force and pressure on elastic and particularly viscoelastic materials which have similar behavior as that of biological tissues is studied. The behavior of a rigid grasper with wedge-like teeth, when pressed into a delayed elasticity material is being examined. Initially, a single wedge penetrating into a solid is studied and then is extended to the grasper. The elastic wedge indentation is the basis of this study and the effects of time are included in the equations by considering the corresponding integral operator from viscoelastic stress-stain relations. Under the action of a constant normal load, the penetration of the indenter and the contact area will change. In this research, the variation of the contact area with time and the grasping contact force is studied. The results of this study which provides a closed form expression for grasping contact force and contact area are compared with those from elastic analysis.

1.
Dong-Soo, K., and Ki, Y.W., 1998, “Microsurgical Telerobot System,” Proc. Of the IEEE/RSJ International Conference on Intelligent Robotics and Systems; 945–950.
2.
Read
W. H.
,
1950
, “
Stress Analysis for Compressible Viscoelastic Materials
,”
Journal of Applied Physics
,
21
, pp.
671
674
.
3.
Lee
E. H.
,
1955
, “
Stress analysis in visco-elastic bodies
,”
Quarterly of Applied Mathematics
,
13
, pp.
183
190
.
4.
Radok
J. R. M.
,
1957
, “
Visco-elastic stress analysis
,”
Quarterly of Applied Mathematics
,
5
, pp.
198
202
.
5.
Lee
E. H.
, and
Radok
J. R. M.
,
1960
, “
The contact problem for viscoelastic bodies
,”
Journal of Applied Mechanics
,
27
, pp.
438
444
.
6.
Hunter
S. C.
,
1960
, “
The Hertz problem for a rigid spherical indenter and a viscoelastic half-space
,”
Journal of the Mechanics and Physics of Solids
,
8
, pp.
219
234
.
7.
Graham
G. A. C.
,
1965
, “
The contact problem in the linear theory of viscoelasticity
,”
International Journal of Engineering Science
,
3
, pp.
27
46
.
8.
Graham
G. A. C.
,
1967
, “
The contact problem in the linear theory of viscoelasticity when the time dependent contact area has any number of maxima and minima
,”
International Journal of Engineering Science
,
5
, pp.
495
514
.
9.
Ting
T. C. T.
,
1966
, “
The contact stresses between a rigid indenter and a viscoelastic half-space
,”
Journal of Applied Mechanics
,
33
, pp.
845
854
.
10.
Ting
T. C. T.
,
1968
, “
Contact problems in the linear theory of viscoelasticity
,”
Journal of Applied Mechanics
,
35
, pp.
248
254
.
11.
Cheng
L.
,
Xia
X.
,
Yum
W.
,
Scriven
L. E.
, and
Gerberich
W. W.
,
2001
, “
Flat - punch indentation of viscoelastic material
,”
Journal of Polymer Science: Part B: Polymer Physics
,
38
, pp.
10
22
.
12.
Larrson
P. L.
, and
Carlsson
S.
,
1998
, “
Data interpretation on microindentation of viscoelastic polymer
,”
Polymer Testing
,
17
, pp.
49
75
.
13.
Shimizu
S.
,
Yanagimoto
Y.
, and
Sakai
M.
,
1999
, “
Pyramidal indentation load-depth curve of viscoelastic material
,”
Journal of Materials Research
,
14
, pp.
4075
4086
.
14.
Sakai
M.
, and
Shimizu
S.
,
2001
, “
Indentation rheometry for glass-forming materials
,”
Journal of Non-crystalline Solids
,
28
, pp.
236
247
.
15.
Sakai
M.
,
2002
, “
Time-dependent viscoelastic relation between load and penetration for an axisymmteric indenter
,”
Philosophical Magazine A
,
A82
, pp.
1841
1849
.
16.
Oyen
M. L.
, and
Cook
R. F.
,
2003
, “
Load-displacement behavior during sharp indentation of viscous-elasticplastic materials
,”
Journal of Materials Research
,
18
, pp.
139
150
.
17.
Oliver
W. C.
, and
Pharr
G. M.
,
1992
, “
An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments
,”
Journal of Materials Research
,
7
, pp.
1564
1580
.
18.
Johnson, K.L., 1985 “Contact Mechanics,” Cambridge University press, Cambridge, UK.
19.
Mase, G.T., and Mase, G.E., 1999 “Continuum Mechanics for Engineers (2nd edn),” CRC: Boca Raton.
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