An Integrated Approach for Virtual Microstructure Generation and Micro-Mechanics Modelling for Micro-Forming Simulation

To aid FE simulation for forming micro-components, an integrated approach is proposed to generate virtual microstructure for micro-mechanics modelling. Based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micro-materials. The input data of the system are physical parameters of a material, including average, minimum and maximum grain sizes. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation and a method has been developed to solve the probability equation. These are the basis for the development of the VGRAIN system, which can be used to generate different grain structures and shapes that follow a certain pattern according to the probability theory. Statistical analyses have been carried out to investigate the distribution of generated virtual grains. The generated virtual microstructure is then implemented in the commercial FE code, ABAQUS, for mesh generation and micro-mechanics analysis using crystal plasticity equations for FCC materials. The crystal plasticity model is implemented in the commercial FE code, ABAQUS, through the used-defined subroutine, UMAT. FE analyses have been carried out to investigate size effects and localised necking encountered in micro-forming processes.

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AN INTEGRATED CRYSTAL PLASTICITY FE SYSTEM FOR MICROFORMING SIMULATION

Journal of Multiscale Modelling ◽

10.1142/s1756973709000037 ◽

2009 ◽

Vol 01 (01) ◽

pp. 107-124 ◽

Cited By ~ 23

Author(s):

J. CAO ◽

W. ZHUANG ◽

S. WANG ◽

K. C. HO ◽

N. ZHANG ◽

...

Keyword(s):

Probability Theory ◽

Crystal Plasticity ◽

Voronoi Tessellation ◽

Control Variable ◽

Integrated System ◽

Physical Parameters ◽

Face Centered Cubic ◽

Grain Structures ◽

Face Centered ◽

Fcc Materials

Based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micromaterials. This system requires physical parameters obtained from microstructures of materials, such as the average, minimum and maximum grain sizes. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation and a method has been developed to solve the probability equation. These are the basis for the development of the VGRAIN system, which can be used to generate different grain structures and shapes that follow a certain pattern according to the probability theory. Statistical analyses have been carried out to investigate the distribution of generated virtual grains. The generated virtual microstructure is then implemented in the commercial FE code, ABAQUS, for mesh generation and micromechanics analysis using crystal plasticity (CP) equations for face-centered cubic (FCC) materials, which are implemented in the commercial FE solver, ABAQUS, through the user-defined subroutines, VUMAT/UMAT. FE analyses have been carried out to demonstrate the effectiveness of the integrated system for the investigation of localized straining and necking, encountered in microforming processes, such as extrusion of micropins, deformation of microfilms and hydroforming of microtubes.

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AN INTEGRATED MICROMECHANICS MODELLING APPROACH FOR MICRO-FORMING SIMULATION

International Journal of Modern Physics B ◽

10.1142/s0217979208051352 ◽

2008 ◽

Vol 22 (31n32) ◽

pp. 5907-5912 ◽

Cited By ~ 3

Author(s):

W. ZHUANG ◽

J. LIN

Keyword(s):

Voronoi Tessellation ◽

Control Variable ◽

Integrated System ◽

Physical Parameters ◽

Micro Forming ◽

Forming Process ◽

Forming Simulation ◽

Localized Necking ◽

Micro Parts ◽

Microstructure Of The Material

An effort has been made to create an integrated Crystal Plasticity FE (CPFE) system. This enables micro-forming process simulation to be carried out easily and the important features in forming micro-parts can be captured. Firstly, based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micro-materials. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation. An interface has been created, so that the generated virtual microstructure of the material can be inputted in the commercial FE code, ABAQUS, for mesh generation. Secondly, FE analyses have been carried out to demonstrate the effectiveness of the integrated system for the investigation of uncontrollable curvature and localized necking in extrusion of micro-pins and hydro-forming of micro-tubes.

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Integrated Approach to Coastal Zone Management in Puerto Galera, Oriental Mindoro, Philippines

Water Science & Technology ◽

10.2166/wst.1984.0075 ◽

1984 ◽

Vol 16 (3-4) ◽

pp. 433-440

Author(s):

O C A Iriberri

Keyword(s):

Coastal Zone ◽

Coastal Zone Management ◽

Integrated Approach ◽

Physical Parameters ◽

Ecological Studies ◽

Continuous Increase ◽

Zone Management ◽

Single Fragment ◽

Human Attitude ◽

And Migration

Coastal zone management requires an understanding of the complex milieu of interactions and activities taking place in an environmental system. Man is beginning to recognize that the old method of dealing with individual issues and problems as single fragment of a whole ecosystem is not enough. This paper tries to deal with the integrated manner in carrying out effectively the management of the coastal zone in Puerto Galera, Oriental Mindoro by the Man and the Biosphere Interagency Committee on Ecological Studies. To attain the objective of the project, the different agencies monitor, identify, observe, investigate various natural and physical parameters contributing to the ecological balance and study the rational use of the resources along the coastal zone. Result of the study showed that although such factors as land use practices of shifting cultivation (kaingin), human attitude towards forest and its resources, and continuous increase in population and migration of people were observed, such pressure on lands has not greatly affected the Puerto Galera coastal zone resources.

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Evolution of Crystal Orientations in Plastically Deformed Steels: Role of Constitutive Models Used in Finite Element Simulations

Volume 1: Plant Operations, Maintenance, Engineering, Modifications, Life Cycle and Balance of Plant; Nuclear Fuel and Materials; Radiation Protection and Nuclear Technology Applications ◽

10.1115/icone21-16767 ◽

2013 ◽

Author(s):

Samir El Shawish ◽

Leon Cizelj ◽

Igor Simonovski

Keyword(s):

Finite Element ◽

Stainless Steel ◽

Plastic Strain ◽

Crystal Plasticity ◽

Power Plants ◽

Voronoi Tessellation ◽

Finite Element Simulations ◽

Plasticity Model ◽

Crystal Orientations ◽

Individual Grains

Stainless steel is a commonly used material in safety-important components of nuclear power plants. In order to study degradation mechanisms in stainless steels, like crack initiation and propagation, it is important to characterize the degree of plastic strain on microstructural level. One way to estimate local plastic strain is by measuring local crystal orientations of the scanned surfaces: the electron backscatter diffraction (EBSD) measurements on stainless steel revealed a strong correlation between the spread of crystal orientations within the individual grains and the imposed macroscopic plastic strain. Similar behavior was also reproduced by finite element simulations where stainless steel was modeled by an anisotropic elasto-plastic constitutive model. In that model the anisotropic Hill’s plasticity function for yield criteria was used and calibrated against the EBSD measurements and macroscopic tensile curve. In this work the Hill’s phenomenological model is upgraded to a more sophisticated crystal plasticity model where plastic deformation is assumed to be a sum of crystalline slips in all activated slip systems. The hardening laws of Peirce, Asaro and Needleman and of Bassani and Wu are applied in crystal plasticity theory and implemented numerically within the user subroutine in ABAQUS. The corresponding material parameters are taken from literature for 316L stainless steel. Finite element simulations are conducted on the analytical Voronoi tessellation with 100 grains and initial random crystallographic orientations. From the simulations, crystal and modified crystal deformation parameters are calculated, which quantify mean and median spread of crystal orientations within individual grains with respect to central grain orientation. The results are compared to EBSD measurements and previous simulations performed with Hill’s plasticity model.

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Simulation of Thermally Activated Metal Forming Process With Meso-Scale Crystal Plasticity

Applied Mechanics and Biomedical Technology ◽

10.1115/imece2003-43624 ◽

2003 ◽

Author(s):

Suhui Wang ◽

Chunlei Xie ◽

Le Ye ◽

Xin Wu

Keyword(s):

Strain Rate ◽

Crystal Plasticity ◽

Metal Forming ◽

High Strain ◽

Material Behavior ◽

Slip Systems ◽

Forming Process ◽

Forming Simulation ◽

Thermally Activated ◽

Von Mises

Under thermally activated deformation conditions many engineering metals (steels, aluminum and magnesium alloys) exhibit much enhanced formability; thus, thermal forming has received increasing interests by automotive industries. The thermally activated material constitutive behaviors are not only strain dependent, but also strain rate and temperature dependent, and it is sensitive to in-situ microstructure evolution. In addition, non-steady-state deformation at a high strain rate (in the order of 10−2s−1 or above) introduces additional challenges in forming simulation. In this case, von Mises based macroscopic plasticity are often not sufficient to describe material behaviors with complex thermomechanical history. In this paper, the rate-dependent crystal plasticity model [1] was applied to the high temperature and high strain rate deformation that is dominated by dislocation creep. A user material subroutine was developed and used for FEA metal forming simulation using commercial ABAQUS/Dynamic code. In the simulation, material behavior was computed based on crystal plasticity at each strain increment without using von-Mises equation or a look-up table of material testing data. By inputting different slip systems or their combinations, and by matching the predicted crystallographic textures with experimentally obtained ones, the active slip systems responsible for the deformation was identified. Then, the material parameters were best fitted to the tensile curves obtained at various strain rates and temperatures. The model was applied for more complex multi-axial metal forming processes. The material behavior, along with its crystallographic texture development, was obtained and validated. As a demonstration, this paper also provides an analysis of a newly developed thrmal forming process [2] with this meso-scale crystal plasticity approach. This forming process involves diameter expansion of a tubular workpiece under combined internal pressure and axial loading and at elevated temperatures.

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Crystal Plasticity Simulation of the Bauschinger Effect of Polycrystalline AA7075 through a Texture-Based Representative Volume Element Model

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.553.22 ◽

2014 ◽

Vol 553 ◽

pp. 22-27

Author(s):

Ling Li ◽

Lu Ming Shen ◽

Gwénaëlle Proust

Keyword(s):

Finite Element ◽

Representative Volume Element ◽

Crystal Plasticity ◽

Bauschinger Effect ◽

Voronoi Tessellation ◽

Strain Curve ◽

Element Model ◽

Volume Element ◽

Model Parameters ◽

Representative Volume

A texture-based representative volume element (TBRVE) model is developed for the three-dimensional crystal plasticity (CP) finite element simulations of the Bauschinger effect (BE) of polycrystalline aluminium alloy 7075 (AA7075). In the simulations, the grain morphology is created using the Voronoi tessellation method with the material texture systematically discretised from experiment. A modified CP constitutive model, which takes into account the backstress, is used to simulate the BE during cyclic loading. The model parameters are calibrated using the first cycle stress-strain curve and used to predict the mechanical response to the cyclic saturation of AA7075. The results indicate that the proposed TBRVE CP finite element model can effectively capture the BE at the grain level.

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