A constitutive model for entangled polydisperse linear flexible polymers with entanglement dynamics and a configuration dependent friction coefficient. Part II. Modeling “shear modification” following cessation of fast shear flows

2018 ◽  
Vol 62 (1) ◽  
pp. 135-147 ◽  
Author(s):  
D. W. Mead ◽  
S. Monjezi ◽  
J. Park
Keyword(s):  
Friction Coefficient ◽  
Constitutive Model ◽  
Shear Flows ◽  
Entanglement Dynamics ◽  
Flexible Polymers ◽  
Shear Modification

scholarly journals Sensitivity Analysis of Johnson-Cook Material Constants and Friction Coefficient Influence on Finite Element Simulation of Turning Inconel 718

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3121 ◽  
Author(s):  
Xiaoli Qiu ◽  
Xianqiang Cheng ◽  
Penghao Dong ◽  
Huachen Peng ◽  
Yan Xing ◽  
...  
Keyword(s):  
Residual Stress ◽  
Sensitivity Analysis ◽  
Finite Element ◽  
Friction Coefficient ◽  
Constitutive Model ◽  
Cutting Force ◽  
Inconel 718 ◽  
Coulomb Friction ◽  
Cutting Conditions ◽  
Simulation Results

The Johnson-Cook (J-C) constitutive model, including five material constants (A, B, n, C, m), and the Coulomb friction coefficient (μ) are critical preprocessed data in machining simulations. Before they become reliable preprocessed data, investigating these parameters’ effect on simulation results benefits parameter-selecting. This paper aims to investigate the different influence of five settings of the J-C constitutive equation and Coulomb friction coefficient on the turning simulation results of Inconel 718 under low-high cutting conditions, including residual stress, chip morphology, cutting force and temperature. A three-dimensional (3-D) finite element model was built, meanwhile, the reliability of the model was verified by comparing the experiment with the simulation. Sensitivity analysis of J-C parameters and friction coefficient on simulation results at low-high cutting conditions was carried out by the hybrid orthogonal test. The results demonstrate that the simulation accuracy of Inconel 718 is more susceptible to strain hardening and thermal softening in the J-C constitutive model. The friction coefficient only has significant effects on axial and radial forces in the high cutting condition. The influences of the coefficient A, n, and m on the residual stress, chip thickness, cutting force and temperature are especially significant. As the cutting parameters increase, the effect of the three coefficients will change visibly. This paper provides direction for controlling simulation results through the adjustment of the J-C constitutive model of Inconel 718 and the friction coefficient.

scholarly journals A constitutive model with microstructure evolution for flow of rate-independent granular materials

2011 ◽  
Vol 682 ◽  
pp. 590-616 ◽  
Author(s):  
JIN SUN ◽  
SANKARAN SUNDARESAN
Keyword(s):  
Friction Coefficient ◽  
Constitutive Model ◽  
Granular Materials ◽  
Simple Shear ◽  
Evolution Equations ◽  
Complex Loading ◽  
Dem Simulations ◽  
Particle Level ◽  
Complex Rheology ◽  
Using Data

A constitutive model is developed for the complex rheology of rate-independent granular materials. The closures for the pressure and the macroscopic friction coefficient are linked to microstructure through evolution equations for coordination number and fabric. The material constants in the model are functions of particle-level properties and are calibrated using data generated through simulations of steady and unsteady simple shear using the discrete element method (DEM). This model is verified against DEM simulations at complex loading conditions.

scholarly journals Purely elastic linear instabilities in parallel shear flows with free-slip boundary conditions

2021 ◽  
Vol 928 ◽  
Author(s):  
Martin Lellep ◽  
Moritz Linkmann ◽  
Bruno Eckhardt ◽  
Alexander Morozov
Keyword(s):  
Boundary Condition ◽  
Stability Analysis ◽  
Constitutive Model ◽  
Spatial Structure ◽  
Boundary Conditions ◽  
Shear Flows ◽  
Body Force ◽  
Slip Boundary Conditions ◽  
Slip Boundary ◽  
Parallel Shear Flows

We perform a linear stability analysis of viscoelastic plane Couette and plane Poiseuille flows with free-slip boundary conditions. The fluid is described by the Oldroyd-B constitutive model, and the flows are driven by a suitable body force. We find that both types of flow become linearly unstable, and we characterise the spatial structure of the unstable modes. By performing a boundary condition homotopy from the free-slip to no-slip boundaries, we demonstrate that the unstable modes are directly related to the least stable modes of the no-slip problem, destabilised under the free-slip situation. We discuss how our observations can be used to study recently discovered purely elastic turbulence in parallel shear flows.

Oscillatory and simple shear flows of a flour-water dough: a constitutive model

1997 ◽  
Vol 36 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Nhan Phan-Thien ◽  
Mohsen Safari-Ardi ◽  
Alexandro Morales-Pati�o
Keyword(s):  
Constitutive Model ◽  
Simple Shear ◽  
Shear Flows

scholarly journals A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaohui Cheng ◽  
Shize Xiao ◽  
Alex Sixie Cao ◽  
Meiying Hou
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Shear Flow ◽  
Constitutive Model ◽  
Earthquake Engineering ◽  
Shear Flows ◽  
Low Pressure ◽  
Flow State ◽  
Granular Shear ◽  
Flow Transitions

AbstractGranular shear flows exhibit complex transitional regimes that are dramatically affected by the pressure level and shear stress state. New advances in granular shear tests at low pressure have enlightened the understanding of the two granular shear flow transitions: between quasi-static and moderate shear flows, and between steady-state and transient shear flows. However, a unified constitutive model to describe these two transitions is yet to develop. In this work, a simplified and unified model is proposed based on innovative triaxial shear flow tests, using two dimensionless physical variables. Model results validated against experimental data suggest that the shear flow transition between a quasi-static to a moderate Isotach type flow state is highly pressure-dependent. At extremely low pressure, the granular viscosity becomes the primary mechanism, suppressing the quasi-static mechanism even under “quasi-static” shear rates. In transient to steady state granular flow transitions, a mobilized shear stress ratio or mobilized friction coefficient between zero and the critical state ratio for consolidated granular packings is taken into consideration. This is coupled with the mechanism of granular viscosity. These findings have not been discussed before and are of great relevance to granular mechanics as well as space and earthquake engineering.

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