The study of the inelastic deformation behavior of six amorphous and semicrystalline polymers was performed to develop and verify the capabilities of a constitutive material model. The test conditions consisted of piecewise constant strain rates for loading and unloading. Immediate control mode switching capability permitted using load control for creep and recovery tests. Positive, nonlinear rate sensitivity was observed in all cases for monotonic loading and the prior loading rate was found to have a strong influence on creep, relaxation and strain recovery (emulating creep at zero stress) tests. In particular, a fast prior rate engenders a larger change in the output variable: strain in conditions of creep and stress drop in relaxation. Based on the absence of any distinctive deformation traits, the preponderance of data collected in the experimentation program suggests that both categories of polymers can be modeled using the same phenomenological approach. Modeling of the experimental data is introduced with a uniaxial form of the Viscoplasticity Theory Based on Overstress for Polymers (VBOP). Simulations and model predictions are provided for various loading histories. Additional modifications necessary to extend the theory to finite deformation and inelastic compressibility are then presented. An objective formulation is obtained in the Eulerian framework together with the recently proposed logarithmic spin by Xiao [Xiao, H., Bruhns, O., and Meyers, A., 1997, “Hypoelesticity Model Based Upon the Logarithmic Stress Rate,” J. Elast., 47, pp. 51–68].

1.
Krempl
,
E.
, 1998, “
Some General Properties of Solid Polymer Inelstic Deformation Behavior and Their Application to a Class of Clock Models
,”
J. Rheol.
0148-6055,
42
, pp.
713
725
.
2.
Kuroda
,
M.
, 2004, “
A Phenomenological Plasticity Model Accounting for Hydrostatic Stress-Sensitivity and Vertex-Type of Effect
,”
Mech. Mater.
0167-6636,
36
, pp.
285
297
.
3.
Khan
,
A.
, and
Zhang
,
H.
, 2001, “
Finite Deformation of a Polymer: Experiments and Modeling
,”
Int. J. Plast.
0749-6419,
17
, pp.
1167
1188
.
4.
Nikolov
,
S.
, and
Doghri
,
I.
, 2000, “
A Micro/Macro Constitutive Model for the Small-Deformation Behavior of Polyethylene
,”
Polymer
0032-3861,
41
, pp.
1883
1935
.
5.
Zhang
,
C.
, and
Moore
,
I.
, 1997, “
Nonlinear Mechanical Response of High Density Polyethylene. Part 1
,”
Polym. Eng. Sci.
0032-3888,
37
(
2
), pp.
404
413
.
6.
Bordonaro
,
C. M.
, and
Krempl
,
E.
, 1992, “
The Effect of Strain Rate on the Deformation and Relaxation Behavior of 6∕6 Nylon at Room Temperature
,”
Polym. Eng. Sci.
0032-3888,
32
, pp.
1066
1072
.
7.
Bordonaro
,
C. M.
, and
Krempl
,
E.
, 1993, “
The Rate Dependent Mechanical Behavior of Plastics: A Comparison Between 6∕6 Nylon, Polyetherimide, and Poly(etheretherketone)
,”
Use of Plastics Composites: Materials and Mechanics Issues, ASME
,
46
, pp.
43
55
.
8.
Ariyama
,
T.
, and
Kaneko
,
K.
, 1995, “
A Constitutive Theory for Polypropylene in Cyclic Deformation
,”
Polym. Eng. Sci.
0032-3888,
35
, pp.
1461
1467
.
9.
Krempl
,
E.
, and
Khan
,
F.
, 2003, “
Rate (Time)-Dependent Deformation Behavior: An Overview of Some Properties of Metals and Solid Polymers
,”
Int. J. Plast.
0749-6419,
19
, pp.
1069
1095
.
10.
Colak
,
O.
, and
Krempl
,
E.
, 2003, “
Modeling of Uniaxial and Biaxial Ratcheting Behavior of 1026 Carbon Steel Using the Simplified Viscoplasticity Theory Based on Overstress (VBO)
,”
Acta Mech.
0001-5970,
160
, pp.
27
44
.
11.
Krempl
,
E.
, 1996, “
A Small Strain Viscoplasticity Theory Based on Overstress
,”
Unified Constitutive Laws of Plastic Deformation
,
A.
Krausz
, and
K.
Krausz
, eds., Academic, San Diego, pp.
281
318
.
12.
Ho
,
K.
, 2001, “
Modeling of Nonlinear Rate Sensitivity by Using an Overstress Model
,”
CMES
,
2
, pp.
351
364
.
13.
Krempl
,
E.
, and
Ho
,
K.
, 2001, “
An Overstress Model for Solid Polymer Deformation Behavior Applied to Nylon 66
,”
ASTM STP 1357
.
14.
Krempl
,
E.
, and
Ho
,
K.
, 2001, “
Inelastic Compressible and Incompressible, Isotropic Small Strain Viscoplasticity Theory Based on Overstress (VBO)
,”
Handbook of Materials Behavior Models
,
Jean
Lemaitre
, ed., San Diego, Vol.
1
.
15.
Maciucescu
,
L.
, 2002, “
A Simplified Viscoplasticity Theory Based on Overstress for Low to High Homologous Temperature and Quasi-Static to Dynamic Applications
,” Doctoral thesis, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnic Institute, Troy, NY.
16.
Krempl
,
E.
, and
Maciucescu
,
L.
, 2001, “
Modeling of Rate Dependence and Creep Using VBO with a Minimum Number of Constants
,” in
Proceedings of CREEP 7
, Japan Society of Mechanical Engineering, Tsukuba, Japan, pp.
617
.
17.
Bordonaro
,
C. M.
, 1995, “
A State Variable Model for High Strength Polymers
,”
Polym. Eng. Sci.
0032-3888,
35
, pp.
310
316
.
18.
Xiao
,
H.
,
Bruhns
,
O.
, and
Meyers
,
A.
, 1997, “
Hypo-elasticity Model Based Upon the Logarithmic Stress Rate
,”
J. Elast.
0374-3535,
47
, pp.
51
68
.
19.
Gomaa
,
S.
,
Sham
,
T. L.
, and
Krempl
,
E.
, 2004, “
Finite Element Formulation for Finite Deformation, Isotropic Viscoplasticity Based on Overstress (FVBO)
,”
Int. J. Solids Struct.
0020-7683,
41
, pp.
3607
3624
.
20.
Gomaa
,
S.
, 2000, “
Computational Procedures for Finite Deformation, Rate Independent Plasticity and Viscoplasticity Based on Overstress
,” Doctoral thesis, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnic Institute, Troy, NY.
21.
Cernocky
,
E. P.
, and
Krempl
,
E.
, 1979, “
A Nonlinear Integral Constitutive Equation Incorporating Rate Effects, Creep and Relaxation
,”
Int. J. Non-Linear Mech.
0020-7462,
14
, pp.
183
203
.
22.
Ho
,
K.
, 1998, “
Application of the Viscoplasticity Theory Based on Overstress to the Modeling of Dynamic Strain Aging of Metals and to Solid Polymers, Specifically Nylon 66
,” PhD thesis, Department of Mechanical Engineering, Aeronautical Engineering and Mechanics, Rensselaer Polytechnic Institute, Troy, NY.
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