scholarly journals Viscoplastic Model Development With an Eye Toward Characterization

1995 ◽  
Vol 117 (1) ◽  
pp. 8-13 ◽  
Author(s):  
Alan D. Freed ◽  
Kevin P. Walker
Keyword(s):  
Steady State ◽  
Copper Alloy ◽  
Model Development ◽  
Hysteresis Loops ◽  
Steady State Creep ◽  
Creep Data ◽  
Stress Strain ◽  
Creep Theory ◽  
Viscoplastic Model ◽  
Material Functions

A viscoplastic theory is developed that reduces analytically to creep theory under steady-state conditions. A viscoplastic model is constructed within this theoretical framework by defining material functions that have close ties to the physics of inelasticity. As a consequence, this model is easily characterized—only steady-state creep data, monotonic stress-strain curves, and saturated stress-strain hysteresis loops are required. The model is applied to the copper alloy NARloy Z.

Extending the Theory of Creep to Viscoplasticity

1994 ◽  
Vol 116 (1) ◽  
pp. 67-75 ◽  
Author(s):  
A. D. Freed ◽  
K. P. Walker ◽  
M. J. Verrilli
Keyword(s):  
Steady State ◽  
Simple Model ◽  
Power Law ◽  
Copper Alloy ◽  
Theoretical Framework ◽  
Kinetics Equation ◽  
Creep Theory ◽  
Material Functions

A viscoplastic theory is developed that reduces to creep theory analytically under steady-state conditions. A fairly simple model is constructed from this theoretical framework by defining material functions that have close ties to the physics of inelasticity; consequently, the model is characterized easily. The computational characteristics of the model are enhanced, in general, by converting the kinetics equation from a hyperbolic relationship to a power-law relationship. The resulting model is applied to copper and to the copper alloy, NARloy Z.

A Theoretical Approach to Creep Deformation During Intermittent Load

1971 ◽  
Vol 93 (2) ◽  
pp. 205-210 ◽  
Author(s):  
R. Lagneborg
Keyword(s):  
Steady State ◽  
Applied Stress ◽  
Creep Deformation ◽  
Theoretical Approach ◽  
Steady State Creep ◽  
Numerical Computations ◽  
Stress Cycle ◽  
Creep Theory ◽  
Cyclic Stresses ◽  
Intermittent Loading

The influence of intermittent loading on creep deformation has been examined in terms of the recovery creep theory. It has been shown that according to this theory a material exposed to cyclic stresses of the same sign always creeps at a rate that is larger than the average of the steady state creep rates at the various stresses. Numerical computations have been performed in order to show how this accelerated strain depends on the applied stress and the time of the stress cycle.

Creep Contributes to the Fatigue Behavior of Bovine Trabecular Bone

1998 ◽  
Vol 120 (5) ◽  
pp. 647-654 ◽  
Author(s):  
S. M. Bowman ◽  
X. E. Guo ◽  
D. W. Cheng ◽  
T. M. Keaveny ◽  
L. J. Gibson ◽  
...  
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Trabecular Bone ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Hysteresis Loops ◽  
Steady State Creep ◽  
Time To Failure ◽  
Steady State Creep Rate ◽  
Creep Tests

Repetitive, low-intensity loading from normal daily activities can generate fatigue damage in trabecular bone, a potential cause of spontaneous fractures of the hip and spine. Finite element models of trabecular bone (Guo et al., 1994) suggest that both creep and slow crack growth contribute to fatigue failure. In an effort to characterize these damage mechanisms experimentally, we conducted fatigue and creep tests on 85 waisted specimens of trabecular bone obtained from 76 bovine proximal tibiae. All applied stresses were normalized by the previously measured specimen modulus. Fatigue tests were conducted at room temperature; creep tests were conducted at 4, 15, 25, 37, 45, and 53°C in a custom-designed apparatus. The fatigue behavior was characterized by decreasing modulus and increasing hysteresis prior to failure. The hysteresis loops progressively displaced along the strain axis, indicating that creep was also involved in the fatigue process. The creep behavior was characterized by the three classical stages of decreasing, constant, and increasing creep rates. Strong and highly significant power-law relationships were found between cycles-to-failure, time-to-failure, steady-state creep rate, and the applied loads. Creep analyses of the fatigue hysteresis loops also generated strong and highly significant power law relationships for time-to-failure and steady-state creep rate. Lastly, the products of creep rate and time-to-failure were constant for both the fatigue and creep tests and were equal to the measured failure strains, suggesting that creep plays a fundamental role in the fatigue behavior of trabecular bone. Additional analysis of the fatigue strain data suggests that creep and slow crack growth are not separate processes that dominate at high and low loads, respectively, but are present throughout all stages of fatigue.

Deformation Behavior of SiC Whisker Reinforced Si3N4

1986 ◽  
Vol 78 ◽  
Author(s):  
R. D. Nixon ◽  
S. Chevacharoenkul ◽  
M. L. Huckabee ◽  
S. T. Buljan ◽  
R. F. Davis
Keyword(s):  
Electron Microscopy ◽  
Steady State ◽  
Deformation Behavior ◽  
Steady State Creep ◽  
Boundary Phase ◽  
Creep Data ◽  
Steady State Creep Rate ◽  
Sic Whiskers ◽  
Principal Factors ◽  
Prepared Composite

ABSTRACTConstant compressive stress creep exp∼riments in jhe temperature and stress ranges of 1420K – 1570K and 50 MN/m2 –350 MN/m2 have been conducted on hot pressed unreinforced Si3N4 containing the densification aids of 6 wt% Y2O3 and 1.5 wt% Al2O3 and on a similarly prepared composite material reinforced with 20 vol% SiC whiskers. Steady-state creep data obtained on these materials in a N2 atmosphere gave stress exponent values of 1.2 – 1.6 and 0.4 – 1.6 for the unreinforced Si3N4 and the composite, respectively. A break in the steady-state creep rate vs. log stress observed only in the composite occurred at approximately 250 MN/m2 at the temperatures of 1520K and 1570K. This information coupled with the results of electron microscopy indicate that the temperature as well as the extensive crystallization (or lack of it) of the amorphous grain boundary phase are the principal factors controlling the deformation rate at a given stress within the limits of the small total strains achieved in this research.

Analysis of Steady State Creep Behaviour in Spherical Vessels Made of Composite Material

2019 ◽  
Vol 18 ◽  
pp. 3401-3408 ◽  
Author(s):  
Sukhjinder Singh Sandhu ◽  
Tejeet Singh ◽  
V.K. Gupta
Keyword(s):  
Composite Material ◽  
Steady State ◽  
Creep Behaviour ◽  
Steady State Creep
Sign in / Sign up

Export Citation Format

Share Document