Numerical Simulation of Collision Effect on Damage Evolution in Electromagnetic Forming of Aluminum Alloy Sheet

2018 ◽  
Vol 765 ◽  
pp. 216-221
Author(s):  
Xi Fan Zou ◽  
Shang Yu Huang ◽  
Wei Liu ◽  
Yu Lei ◽  
Jie Zhu
Keyword(s):  
Numerical Simulation ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Alloy Sheet ◽  
Void Volume Fraction ◽  
Electromagnetic Forming ◽  
Void Volume ◽  
Free Form ◽  
Al Alloy ◽  
Form Model

A numerical simulation study of collision effect on damage evolution in electromagnetic forming (EMF) was presented. EMF technology can greatly improve the forming limit of metal sheet duo to the high rate. However, collision behavior is also an important factor for the formability of sheet. Free form model and conical die model were carried out to study the effect of collision behavior on mechanical properties of Al alloy sheet. The EMF process of 1050 Al alloy sheet was analyzed and discussed by numerical analysis software LS-DYNA. The combined strategy of boundary element method and finite element method was adopted to realize the coupling calculation of electromagnetic field and structural field. Based on the GTN material model, the evolution of void volume fraction of 1050 Al sheet were calculated and analyzed. Comparing the free form model results and the die form model results, showed that the collision behavior could reduce the void volume fraction of sheet, but excessively high collision speed lead to the sheet rebound, which aggravated the damage of material and reduce the accuracy of the product. Therefore, the appropriate discharge voltage in this work was found to improve mechanical property of sheet on the premise of forming precision.

The Effect of Tool–Sheet Interaction on Damage Evolution in Electromagnetic Forming of Aluminum Alloy Sheet

2005 ◽  
Vol 127 (1) ◽  
pp. 145-153 ◽  
Author(s):  
J. M. Imbert ◽  
S. L. Winkler ◽  
M. J. Worswick ◽  
D. A. Oliveira ◽  
S. Golovashchenko
Keyword(s):  
Damage Evolution ◽  
Numerical Study ◽  
Forming Limit Diagram ◽  
Alloy Sheet ◽  
Electromagnetic Forming ◽  
Free Form ◽  
Forming Limit ◽  
Metallographic Analysis ◽  
Narrow Region ◽  
Conical Die

A study of the effect of tool–sheet interaction on damage evolution in electromagnetic forming is presented. Free form and conical die experiments were carried out on 1 mm AA5754 sheet. Safe strains beyond the conventional forming limit diagram (FLD) were observed in a narrow region in the free form experiments, and over a significant region of the part in the conical die experiments. A parametric numerical study was undertaken, that showed that tool–sheet interaction had a significant effect on damage evolution. Metallographic analysis was carried out to quantify damage in the parts and to confirm the numerical results.

scholarly journals Critical Void Volume Fraction Identification Based on Mesoscopic Damage Model for NVA Shipbuilding Steel

2019 ◽  
Vol 18 (4) ◽  
pp. 444-456
Author(s):  
Zijie Song ◽  
Zhiqiang Hu ◽  
Jonas W. Ringsberg
Keyword(s):  
Numerical Simulation ◽  
Mild Steel ◽  
Ductile Fracture ◽  
Volume Fraction ◽  
Fracture Behaviour ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Simulation Results ◽  
Ship Collision ◽  
Critical Void

Abstract NVA mild steel is a commonly used material in the shipbuilding industry. An accurate model for description of this material’s ductile fracture behaviour in numerical simulation is still a challenging task. In this paper, a new method for predicting the critical void volume fraction fc in the Guson-Tvergaard-Needleman (GTN) model is introduced to describe the ductile fracture behaviour of NVA shipbuilding mild steel during ship collision and grounding scenarios. Most of the previous methods for determination of the parameter fc use a converse method, which determines the values of the parameters through comparisons between experimental results and numerical simulation results but with high uncertainty. A new method is proposed based on the Hill, Bressan, and Williams hypothesis, which reduces the uncertainty to a satisfying extent. To accurately describe the stress-strain relationship of materials before and after necking, a combination of the Voce and Swift models is used to describe the material properties of NVA mild steel. A user-defined material subroutine has been developed to enable the application of the new parameter determination method and its implementation in the finite element software LS-DYNA. It is observed that the model can accurately describe structural damage by comparing the numerical simulation results with those of experiments; thus, the results demonstrate the model’s capacity for structural response prediction in ship collision and grounding scenario simulations

scholarly journals Forming Limit Stress Diagram Prediction of Pure Titanium Sheet Based on GTN Model

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1783 ◽  
Author(s):  
Tao Huang ◽  
Mei Zhan ◽  
Kun Wang ◽  
Fuxiao Chen ◽  
Junqing Guo ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Pure Titanium ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Forming Limit ◽  
Stress And Strain ◽  
Gtn Model ◽  
Stress Diagram ◽  
Limit Stress ◽  
Hemispherical Punch

In this paper, the initial values of damage parameters in the Gurson–Tvergaard–Needleman (GTN) model are determined by a microscopic test combined with empirical formulas, and the final accurate values are determined by finite element reverse calibration. The original void volume fraction (f0), the volume fraction of potential nucleated voids (fN), the critical void volume fraction (fc), the void volume fraction at the final failure (fF) of material are assigned as 0.006, 0.001, 0.03, 0.06 according to the simulation results, respectively. The hemispherical punch stretching test of commercially pure titanium (TA1) sheet is simulated by a plastic constitutive formula derived from the GTN model. The stress and strain are obtained at the last loading step before crack. The forming limit diagram (FLD) and the forming limit stress diagram (FLSD) of the TA1 sheet under plastic forming conditions are plotted, which are in good agreement with the FLD obtained by the hemispherical punch stretching test and the FLSD obtained by the conversion between stress and strain during the sheet forming process. The results show that the GTN model determined by the finite element reverse calibration method can be used to predict the forming limit of the TA1 sheet metal.

Determination of mechanical properties of FFF 3D printed material by assessing void volume fraction, cooling rate and residual thermal stresses

2019 ◽  
Vol 25 (10) ◽  
pp. 1661-1683 ◽  
Author(s):  
Rafael Quelho de Macedo ◽  
Rafael Thiago Luiz Ferreira ◽  
Kuzhichalil Jayachandran
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Young’S Modulus ◽  
Thermal Stresses ◽  
Volume Fraction ◽  
Young's Modulus ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Temperature Fields ◽  
Content Type

Purpose This paper aims to present experimental and numerical analyses of fused filament fabrication (FFF) printed parts and show how mechanical characteristics of printed ABS-MG94 (acrylonitrile butadiene styrene) are influenced by the void volume fraction, cooling rate and residual thermal stresses. Design/methodology/approach Printed specimens were experimentally tested to evaluate the mechanical properties for different printing speeds, and micrographs were taken. A thermo-mechanical finite element model, able to simulate the FFF process, was developed to calculate the temperature fields in time, cooling rate and residual thermal stresses. Finally, the experimental mechanical properties and the microstructure distribution could be explained by the temperature fields in time, cooling rate and residual thermal stresses. Findings Micrographs revealed the increase of void volume fraction with the printing speed. The variations on voids were associated to the temperature fields in time: when the temperatures remained high for longer periods, less voids were generated. The Young's Modulus of the deposited filament varied according to the cooling rate: it decreased when the cooling rate increased. The influence of the residual thermal stresses and void volume fraction on the printed parts failure was also investigated: in the worst scenarios evaluated, the void volume fraction reduced the strength in 9 per cent, while the residual thermal stresses reduced it in 3.8 per cent. Originality/value This work explains how the temperature fields can affect the void volume fraction, Young's Modulus and failure of printed parts. Experimental and numerical results are shown. The presented research can be used to choose printing parameters to achieve desired mechanical properties of FFF printed parts.

scholarly journals Experimental determination of the void volume fraction for S235JR steel at failure in the range of high stress triaxialities

2017 ◽  
Vol 62 (1) ◽  
pp. 167-172 ◽  
Author(s):  
P. G. Kossakowski
Keyword(s):  
Volume Fraction ◽  
High Stress ◽  
Material Model ◽  
Tensile Tests ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Advanced Technique ◽  
Quantitative Image ◽  
Critical Void

Abstract This paper is concerned with the critical void volume fraction fF representing the size of microdefects in a material at the time of failure. The parameter is one of the constants of the Gurson-Tvergaard-Needleman (GTN) material model that need to be determined while modelling material failure processes. In this paper, an original experimental method is proposed to determine the values of fF. The material studied was S235JR steel. After tensile tests, the void volume fraction was measured at the fracture surface using an advanced technique of quantitative image analysis The material was subjected to high initial stress triaxialities T0 ranging from 0.556 to 1.345. The failure processes in S235JR steel were analysed taking into account the influence of the state of stress.

Sign in / Sign up

Export Citation Format

Share Document