Analysis of the Micro/Meso Scale Sheet Forming by Strain Gradient Plasticity and its Characterization of Tool Feature Size Effects

2014 ◽  
Author(s):  
Linfa Peng ◽  
Peiyun Yi ◽  
Peng Hu ◽  
Xinmin Lai ◽  
Jun Ni
Keyword(s):  
Finite Element ◽  
Strain Gradient ◽  
Size Effects ◽  
Reaction Force ◽  
Equivalent Strain ◽  
Sheet Forming ◽  
Geometrical Parameters ◽  
Forming Process ◽  
Feature Size ◽  
Meso Scale

For conventional metal forming, finite element (FE) method becomes a powerful tool in process design. However, conventional material models cannot describe material behaviors precisely in micro/meso scale due to the size/scale effects. As a result, know-how obtained in traditional macro-forming is not suitable for the micro-forming process. In micro/meso scale forming process, the reaction force, localized stress concentration and formability are not only dependent on the strain distribution and strain path but also the strain gradient and strain gradient path caused by decreased scale. This study presented a model based on conventional mechanism based strain gradient (CMSG) plasticity. A user-defined material (UMAT) subroutine incorporating the CMSG plasticity in the ABAQUS finite element (FE) program was established. Based on the subroutine, FE simulations were performed to analyze the effects of the channel width in sheet forming process of micro-channel features. Die sets were fabricated according to the scale law and Micro/meso scale sheet forming experiments were conducted to study the effect of channel width in the die. Experimental results indicated that the CMSG plastic theory achieved better agreements compared to the conventional plastic theory. It found that the influence of the strain gradient to the forming process increased with the decrease of the geometrical parameters of the tools. Furthermore, various tool geometrical parameters were designed by Taguchi Method to explore the feature size effects caused by the decrease of tool geometrical dimensions. According the scale law, similarity difference and the similarity accuracy were calculated to evaluate the size effects. Greater equivalent strain gradient was found with the decrease of the tool geometric dimension, which lead larger maximum reaction force error due to increasing size effects. The main effect plots for equivalent strain gradient and reaction force indicated that the influence of the tools clearance was larger than punch radius, die radius and die width.

Analysis of Micro/Mesoscale Sheet Forming Process by Strain Gradient Plasticity and Its Characterization of Tool Feature Size Effects

2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Linfa Peng ◽  
Peiyun Yi ◽  
Peng Hu ◽  
Xinmin Lai ◽  
Jun Ni
Keyword(s):  
Strain Gradient ◽  
Size Effects ◽  
Scale Effects ◽  
Reaction Force ◽  
Equivalent Strain ◽  
Sheet Forming ◽  
Geometrical Parameters ◽  
Forming Process ◽  
Feature Size ◽  
Plastic Theory

Conventional material models cannot describe material behaviors precisely in micro/mesoscale due to the size/scale effects. In micro/mesoscale forming process, the reaction force, localized stress concentration, and formability are not only dependent on the strain distribution and strain path but also on the strain gradient and strain gradient path caused by decreased scale. This study presented an analytical model based on the conventional mechanism of strain gradient (CMSG) plasticity. Finite element (FE) simulations were performed to study the effects of the width of microchannel features. Die sets were fabricated and micro/mesoscale sheet forming experiments were conducted. The results indicated that the CMSG plastic theory achieves better agreements compared to the conventional plastic theory. It was also found that the influence of strain gradient on the forming process increases with the decrease of the geometrical parameters of tools. Furthermore, the feature size effects in the forming process were evaluated and quantitated by the similarity difference and the similarity accuracy. Various tool geometrical parameters were designed based on the Taguchi method to explore the influence of the strain gradient caused by the decrease of tool dimension. According to the scale law, the difference and accuracy of similarity were calculated. Greater equivalent strain gradient was revealed with the decrease of tool dimension, which led to the greater maximum reaction force error due to the increasing size effects. The main effect plots for equivalent strain gradient and reaction force indicated that the influence of tools clearance is greater than those of punch radius, die radius, and die width.

Micro/Meso Scale Metallic Sheet Forming Process Analysis Based on the Strain Gradient Plasticity Theory

2011 ◽  
Vol 675-677 ◽  
pp. 991-994
Author(s):  
Peng Hu ◽  
Lin Fa Peng ◽  
Xin Min Lai ◽  
Wei Gang Zhang
Keyword(s):  
Strain Gradient ◽  
Process Analysis ◽  
Simulation Method ◽  
Sheet Forming ◽  
Plasticity Theory ◽  
Gradient Plasticity ◽  
Forming Process ◽  
Metallic Parts ◽  
Metallic Sheet ◽  
Meso Scale

Increasing demands for miniature metallic parts have driven the application of micro/meso forming process in various industries. The present study focuses on the size effect which appears in the micro/meso scale sheet forming process. Micro/meso scale stamping experiments and finite element simulations incorporating the CMSG plasticity theory are conducted, respectively. It is found that the numerical simulation results, with strain gradient and strain gradient path taken into account, match the experimental results better than those of conventional simulation method.

Concurrent Engineering Design of Sheet Stamping by Using an Inverse FE Approach

1997 ◽  
Author(s):  
Shiyong Yang ◽  
Kikuo Nezu
Keyword(s):  
Finite Element ◽  
Concurrent Engineering ◽  
Process Simulation ◽  
Three Dimensional ◽  
Sheet Forming ◽  
Design Stage ◽  
Forming Process ◽  
Element Analysis ◽  
Preliminary Design Stage ◽  
Product And Process

Abstract An inverse finite element (FE) algorithm is proposed for sheet forming process simulation. With the inverse finite element analysis (FEA) program developed, a new method for concurrent engineering (CE) design for sheet metal forming product and process is proposed. After the product geometry is defined by using parametric patches, the input models for process simulation can be created without the necessity to define the initial blank and the geometry of tools, thus simplifying the design process and facilitating the designer to look into the formability and quality of the product being designed at preliminary design stage. With resort to a commercially available software, P3/PATRAN, arbitrarily three-dimensional product can be designed for manufacturability for sheet forming process by following the procedures given.

STRAIN GRADIENT POLYCRYSTAL PLASTICITY ANALYSIS: FE MODELING AND SYNCHROTRON X-RAY DIFFRACTION

2010 ◽  
Vol 24 (01n02) ◽  
pp. 10-17 ◽  
Author(s):  
XU SONG ◽  
SHU YAN ZHANG ◽  
ALEXANDER M. KORSUNSKY
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Strain Gradient ◽  
Deformation Behaviour ◽  
Element Model ◽  
Model Parameters ◽  
Multiple Peaks ◽  
X Ray ◽  
Polycrystal Plasticity ◽  
Meso Scale

The results of a strain gradient finite element model of polycrystalline plastic deformation in an HCP alloy were analysed in terms of orientation-related meso-scale grain groups. The predictions for meso-scale elastic strains were post-processed to construct energy dispersive diffraction peak patterns. Synchrotron X-ray polycrystalline diffraction was thereafter employed to record experimentally multiple peaks from deformed samples of Ti -6 Al -4 V alloy. Model parameters were adjusted to provide the best simultaneous match to multiple peaks in terms of intensity, position and shape. The framework provides a rigorous means of validating polycrystal plasticity finite element model. The study represents an example of the parallel development of modelling and experimental tools that is useful for the study of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) effects on the deformation behaviour of (poly)crystals.

Effect of Variable Geometry on Springback of High Strength Steel Materials

2015 ◽  
Vol 1134 ◽  
pp. 154-159
Author(s):  
Muhamad Sani Buang ◽  
Shahrul Azam Abdullah ◽  
Juri Saedon ◽  
Yupiter H.P. Manurung ◽  
Mohd Shahir Mohd Hairuni ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
High Strength Steel ◽  
High Strength ◽  
Bending Test ◽  
Geometrical Parameters ◽  
Forming Process ◽  
Element Simulation ◽  
Punch Radius ◽  
Prevention Method

Springback is the phenomenon in which the material strip unbends itself after forming process. It is caused by the geometrical, mechanical properties or other process parameters. This paper focused on finite element simulation investigation on effects of geometrical parameters on the springback amount of the High Strength Steel (HSS). Two geometrical parameters, punch radius (Rp) and die opening (Wo) were selected and their effect on springback studied. Finite element simulation of U-bending test was performed using Simufact.formingTM with material database (MatILDa) and the level of the springback was measured. The result of the simulation shows that different values of punch radius (Rp) and die opening (Wo) are significant to the springback effect. 3 variable values of (Rp) and (Wo) selected in this studied are (2mm, 4mm, 6mm) and (30mm, 36mm, 48mm) respectively. The findings of the simulation could be used to accurately and reliably predict springback behavior of the tested material. The value of the springback increases, as the value of the die opening (Wo) increases. Meanwhile, the increasing value of the punch radius (Rp) will lead to decreasing springback value. From this finding, a proper prevention method can be taken to eliminate springback, achieve improvement in the forming process as well as reduce processing time and cost.

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