A Finite Deformation Theory of Viscoplasticity Based on Overstress: Part II—Finite Element Implementation and Numerical Experiments

1990 ◽  
Vol 57 (3) ◽  
pp. 553-561 ◽  
Author(s):  
I. Nishiguchi ◽  
T.-L. Sham ◽  
E. Krempl
Keyword(s):  
Finite Element ◽  
Finite Deformation ◽  
Numerical Experiments ◽  
Deformation Theory ◽  
Integration Method ◽  
Time Integration ◽  
Second Order ◽  
Time Integration Method ◽  
Finite Element Implementation ◽  
Finite Deformation Theory

A one-step time integration method is developed for the finite deformation theory of viscoplasticity based on overstress (FVBO) described in Part I. This time integration method is based on a forward gradient approximation and it leads to explicit expressions of the tangent operators suitable for finite element implementation. Numerical experiments and closed-form solutions for a hypoelastic material in homogeneous deformation states are presented. The FVBO is applied to the modeling of second-order effects in torsion. The numerical results show that a modification of the Jaumann rate and second-order terms of the inelastic rate of deformation are necessary to model the observed effects.

scholarly journals Impact of difference between explicit and implicit second-order time integration schemes on isotropic/anisotropic steady incompressible turbulence field

2021 ◽  
Vol 2090 (1) ◽  
pp. 012145
Author(s):  
Ryuma Honda ◽  
Hiroki Suzuki ◽  
Shinsuke Mochizuki
Keyword(s):  
Kinetic Energy ◽  
Energy Conservation ◽  
Integration Method ◽  
Time Integration ◽  
Second Order ◽  
Implicit Time ◽  
Explicit Time Integration ◽  
Time Integration Method ◽  
Implicit Time Integration ◽  
Time Integration Methods

Abstract This study presents the impact of the difference between the implicit and explicit time integration methods on a steady turbulent flow field. In contrast to the explicit time integration method, the implicit time integration method may produce significant kinetic energy conservation error because the widely used spatial difference method for discretizing the governing equations is explicit with respect to time. In this study, the second-order Crank-Nicolson method is used as the implicit time integration method, and the fourth-order Runge-Kutta, second-order Runge-Kutta and second-order Adams-Bashforth methods are used as explicit time integration methods. In the present study, both isotropic and anisotropic steady turbulent fields are analyzed with two values of the Reynolds number. The turbulent kinetic energy in the steady turbulent field is hardly affected by the kinetic energy conservation error. The rms values of static pressure fluctuation are significantly sensitive to the kinetic energy conservation error. These results are examined by varying the time increment value. These results are also discussed by visualizing the large scale turbulent vortex structure.

A Finite Deformation Theory of Viscoplasticity Based on Overstress: Part I—Constitutive Equations

1990 ◽  
Vol 57 (3) ◽  
pp. 548-552 ◽  
Author(s):  
I. Nishiguchi ◽  
T.-L. Sham ◽  
E. Krempl
Keyword(s):  
Finite Deformation ◽  
Constitutive Equations ◽  
Deformation Theory ◽  
Rate Sensitivity ◽  
Second Order ◽  
Stress Rate ◽  
Order Effects ◽  
Additive Decomposition ◽  
Elastic Part ◽  
Finite Deformation Theory

The viscoplasticity theory based on overstress (VBO) is extended to finite deformation (FVBO). Yield surfaces and loading/unloading conditions are not part of this theory which represents creep, relaxation, and rate sensitivity in a “unified” way. Additive decomposition of the rate of deformation into the elastic and the inelastic parts is assumed. For the elastic part, the hypoelastic relation is used. For the inelastic part, the flow law of VBO is augmented by a term quadratic in the overstress together with a modified Jaumann stress rate which jointly or separately allow the modeling of second-order effects.

scholarly journals A novel explicit three-sub-step time integration method for wave propagation problems

2022 ◽  
Author(s):  
Huimin Zhang ◽  
Runsen Zhang ◽  
Andrea Zanoni ◽  
Yufeng Xing ◽  
Pierangelo Masarati
Keyword(s):  
Wave Propagation ◽  
Integration Method ◽  
Time Integration ◽  
Second Order ◽  
New Method ◽  
Explicit Methods ◽  
Time Integration Method ◽  
Numerical Performance ◽  
The Stability ◽  
Better Than

AbstractA novel explicit three-sub-step time integration method is proposed. From linear analysis, it is designed to have at least second-order accuracy, tunable stability interval, tunable algorithmic dissipation and no overshooting behaviour. A distinctive feature is that the size of its stability interval can be adjusted to control the properties of the method. With the largest stability interval, the new method has better amplitude accuracy and smaller dispersion error for wave propagation problems, compared with some existing second-order explicit methods, and as the stability interval narrows, it shows improved period accuracy and stronger algorithmic dissipation. By selecting an appropriate stability interval, the proposed method can achieve properties better than or close to existing second-order methods, and by increasing or reducing the stability interval, it can be used with higher efficiency or stronger dissipation. The new method is applied to solve some illustrative wave propagation examples, and its numerical performance is compared with those of several widely used explicit methods.

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