Springback Evaluation of 304 Stainless Steel in an Electrically Assisted Air Bending Operation

2016 ◽  
Author(s):  
Abdelrahim Khal ◽  
Brandt J. Ruszkiewicz ◽  
Laine Mears
Keyword(s):  
Electric Current ◽  
General Term ◽  
Bending Test ◽  
304 Stainless Steel ◽  
Forming Process ◽  
Cross Sectional ◽  
Air Bending ◽  
Research Fields ◽  
Electrically Assisted ◽  
Microstructural Evaluation

Driven by the automotive industry’s drive towards lightweighting, electrically assisted forming (EAF) is one of the most rapidly growing research fields in bulk deformation, and is classified under the general term “Electrically-Assisted Manufacturing (EAM)”. In EAF electric current (continuous or intermittent) is applied to a metallic sheet during the forming process, leading to numerous advantageous effects that have been studied and proven by several research groups and for different structural metals, such as reduced forming load and flow stress, increased formability, and reduction (or even elimination) of springback. Electrically-assisted bending (EAB) is a recent evolution of EAF technique, with the aim of capitalizing on the aforementioned advantages of EAF technique. In this work the effects of the EAB process on the final springback in an air bending test are identified, with the metal sheet being bent under different electrical field conditions. In addition, a comparison between the effects of applying the current during forming versus post forming are investigated. It was found that in general, higher current density (amount of current through cross sectional area of specimen (A/mm2), more frequent pulse period, and longer pulse duration all resulted in a greater degree of springback reduction. A microstructural evaluation showed no change in grain size in the presence of electric current.

Alternative Control of an Electrically Assisted Tensile Forming Process Using Current Modulation

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Joshua J. Jones ◽  
Laine Mears
Keyword(s):  
Electric Current ◽  
Current Flow ◽  
Current Level ◽  
Temperature Gradients ◽  
Material Strength ◽  
Alternative Control ◽  
Forming Process ◽  
Control Material ◽  
Model Based Control ◽  
Electrically Assisted

Electrically assisted forming is a technique whereby metal is deformed while simultaneously undergoing electric current flow. Using this process, electric current level becomes a new degree of freedom for process control. In this work, we present some alternative control architectures allowing for new avenues of control using such a process. The primary findings are architectures to allow for forming at constant force and forming at constant stress levels by modulating electric current to directly control material strength. These are demonstrated in a tensile forming operation, and found to produce the desired results. Combining these control approaches with previous and contemporary efforts in modeling of the process physics will allow for system identification of material response properties and model-based control of difficult-to-observe process parameters such as real time temperature gradients.

Evaluation of Uniaxial Tensile Behavior under Pulsed Current for Electrically Assisted Warm Forming of Light Weight Alloys

2017 ◽  
Vol 744 ◽  
pp. 254-258
Author(s):  
Jung Han Song ◽  
Injea Jang ◽  
Suh Yun Gwak ◽  
Jun Ho Bang ◽  
Yong Bae Kim ◽  
...  
Keyword(s):  
Electric Current ◽  
Test System ◽  
Warm Forming ◽  
Uniaxial Tensile ◽  
Light Weight ◽  
Test Results ◽  
Forming Process ◽  
Uniaxial Test ◽  
Electrically Assisted ◽  
Deep Drawing Test

In this study, the electric current effects in the deformation of light weight alloys are investigated to improve the formability. To begin with, a test system is built up to carry out the tensile test with heavy electric current flowing through the specimen. The evolutions of the flow stresses and failure elongations were obtained using this test system. The thermal and athermal effect such as electro-plastic effect of metallic materials induced by high density current make significant reduction of the flow stress, which is beneficial to the forming process of less formable metal. From the uniaxial test results, pulse current-assisted deep drawing test were conducted. The experimental results demonstrate that electrically assisted warm forming provides lower energy consumption and higher efficiency.

Investigation of Deformation Behavior of SS304 and Pure Copper Subjected to Electrically Assisted Forming Process

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Tianhao Jiang ◽  
Linfa Peng ◽  
Peiyun Yi ◽  
Xinmin Lai
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Constitutive Model ◽  
Electric Current ◽  
Deformation Behavior ◽  
Pure Copper ◽  
Annihilation Process ◽  
Forming Process ◽  
Electrically Assisted ◽  
Dislocation Movement

Both electrically assisted tension (EAT) and thermally assisted tension (TAT) tests were performed on SS304 and pure copper to decouple the influence of elevated temperature from electric current on flow stress and ductility. It is found that the reduction on flow stress and ductility of SS304 are more dependent on the elevated temperature than electric current, but electric current has a stronger effect by 10% on reducing flow stress and ductility of pure copper than the elevated temperature does. As the flow stress and ductility of two metals are related to the dislocation evolution, a constitutive model considering both storage and annihilation process of dislocation was established to describe the effect of electric current and temperature on dislocation movement. It is found that electric current accelerated the annihilation process of dislocation in pure copper up to 20% in EAT compared with that in TAT, but such phenomenon was rarely observed in SS304. Furthermore, attempts have also been made to distinguish the influence of elevated temperature with that of electric current on microstructure evolution and it is also found that the formation of [111] crystals in pure copper is nearly 10% less in EAT than that in TAT.

Alternative Control of an Electrically-Assisted Tensile Forming Process Using Current Modulation

2013 ◽  
Author(s):  
Joshua J. Jones ◽  
Laine Mears
Keyword(s):  
Electric Current ◽  
Current Flow ◽  
Current Level ◽  
Temperature Gradients ◽  
Material Strength ◽  
Alternative Control ◽  
Forming Process ◽  
Control Material ◽  
Model Based Control ◽  
Electrically Assisted

Electrically-assisted forming is a technique whereby metal is deformed while simultaneously undergoing electric current flow. Using this process, electric current level becomes a new degree of freedom for process control. In this work we present some alternative control architectures allowing for new avenues of control using such a process. The primary findings are architectures to allow for forming at constant force and forming at constant stress levels by modulating electric current to directly control material strength. These are demonstrated in a tensile forming operation, and found to produce the desired results. Combining these control approaches with previous and contemporary efforts in modeling of the process physics will allow for system identification of material response properties and model-based control of difficult-to-observe process parameters such as real time temperature gradients.

Analysis of the Electric and Thermal Effects on Mechanical Behavior of SS304 Subjected to Electrically Assisted Forming Process

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Tianhao Jiang ◽  
Linfa Peng ◽  
Peiyun Yi ◽  
Xinmin Lai
Keyword(s):  
Thermal Effect ◽  
Electric Current ◽  
Yield Stress ◽  
Additional Stress ◽  
Forming Process ◽  
Activation Effect ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Electrically Assisted ◽  
Tension Tests

Significant improvements in deformation resistance and ductility of metals are observed in the electrically assisted forming (EAF) process. Both electroplastic effect (EPE) induced by electric current and thermal effect associated with Joule heating have been proposed to explain the phenomenon. However, there are still arguments in the contribution of the EPE in EAF process. In this paper, both electrically assisted tension tests (EAT) and thermally assisted tension tests (TAT) were conducted on SS304 specimens at the same temperature. The existence of EPE is investigated, and the contribution of EPE is also distinguished with thermal effect numerically by considering the initial yield stress, dislocation hardening, and martensite phase transformation. It is shown when the temperature is around 34 °C, the electric current of 50 A/mm2 in EAT induces additional stress reduction of 16% in the short-range internal stress (effective stress) involved in the initial yield stress and volume reduction of 45.2% in martensite formation compared with results in TAT. However, the effect is not obvious for the cases of 100 A/mm2 and 150 A/mm2 when the temperature is above 100 °C. By comparing the storage coefficient and recovery coefficient of dislocation in EAT and TAT, it indicates that electric current has no additional activation effect on dislocation movement of SS304.

scholarly journals Feasibility of a Two-Stage Forming Process of 316L Austenitic Stainless Steels with Rapid Electrically Assisted Annealing

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 815 ◽  
Author(s):  
Viet Luu ◽  
Thi Nguyen ◽  
Sung-Tae Hong ◽  
Hye-Jin Jeong ◽  
Heung Han
Keyword(s):  
Mechanical Behavior ◽  
Electric Current ◽  
Strain Curve ◽  
Single Pulse ◽  
Stress Strain Curve ◽  
Forming Process ◽  
Stress Strain ◽  
Two Stage ◽  
Post Annealing ◽  
Electrically Assisted

The post-annealing mechanical behavior of 316L austenitic stainless steel (SUS316L) after electrically assisted (EA) annealing with a single pulse of electric current is experimentally investigated to evaluate the feasibility of a two-stage forming process of the selected SUS316L with rapid EA annealing. A tensile specimen is deformed to a specific prestrain and then annealed by applying a single pulse of electric current with a short duration less than 1 s. Finally, the specimen is reloaded until fracture. The stress-strain curve during reloading shows that the flow stress of the SUS316L significantly decreases, which indicates the occurrence of EA annealing. The electric current also increases the maximum achievable elongation of the SUS316L during reloading. The stress-strain curve during reloading and the microstructural observation suggest that the effects of EA annealing on the post-annealing mechanical behavior and microstructure strongly depend on both the applied electric current density (electric current per unit cross-sectional area) and the given prestrain. The results of the present study suggest that the EA annealing technique could be effectively used to improve the formability of SUS316L when manufacturing complex parts.

scholarly journals Research on the Cross Section Forming Quality of Three-Dimensional Multipoint Stretch Forming Parts

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jiaqi Yu ◽  
Yi Li ◽  
Fei Teng ◽  
Jicai Liang ◽  
Xiangfeng Lin ◽  
...  
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Bending Test ◽  
Stretch Forming ◽  
Forming Process ◽  
Cross Sectional ◽  
Forming Quality ◽  
Factors Affecting ◽  
Forming Parameters ◽  
The Cross

This paper introduced the basic principle and main influencing factors of the three-dimensional multipoint stretch forming process and investigated the optimized scheme of the cross section forming quality. The main factors affecting the stretch forming process were studied by the orthogonal test through the numerical simulation technique. In the case of a good target shape, the best combination of forming parameters was established by using the range method. The cross-sectional distortion of the formed profile is the smallest when the prestretching amount is 1% of the profile length, the poststretching amount is 0.8% of the profile length, the number of the die heads is 12, and the friction coefficient is 0.15. The optimal combination of forming parameters was verified by the multipoint bending test.

Several Factors Affecting the Electroplastic Effect During an Electrically-Assisted Forming Process

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Wesley A. Salandro ◽  
Cristina J. Bunget ◽  
Laine Mears
Keyword(s):  
Electric Current ◽  
Cold Work ◽  
Electrical Power ◽  
Forming Process ◽  
Electroplastic Effect ◽  
Factors Affecting ◽  
Forming Load ◽  
Electrically Assisted ◽  
Grade 5 ◽  
Electrically Assisted Manufacturing

Recent development of electrically-assisted manufacturing (EAM) processes proved the advantages of using the electric current, mainly related with the decrease in the mechanical forming load and improvement in the formability. From EAM experiments, it has been determined that a portion of the applied electrical power contributes toward these forming benefits and the rest is dissipated into heat, defined as the electroplastic effect. The objective of this work is to experimentally investigate several factors that affect the electroplastic effect and the efficiency of the applied electricity. Specifically, the effects of various levels of cold work and contact force are explored on both Grade 2 and Grade 5 Titanium alloys. Thermal and mechanical data prove that these factors notably affect the efficiency of the applied electricity during an electrically-assisted forming (EAF) process.

Determination of the metal toughness components in impact-bending test

2018 ◽  
Vol 84 (12) ◽  
pp. 68-72
Author(s):  
A. B. Maksimov ◽  
I. P. Shevchenko ◽  
I. S. Erokhina
Keyword(s):  
Crack Growth ◽  
Specific Energy ◽  
Crack Formation ◽  
Crack Nucleation ◽  
Scale Effects ◽  
Linear Equations ◽  
Bending Test ◽  
Cross Sectional ◽  
Two Samples ◽  
Sample Width

A method for separating the work of impact into two parts - the work of the crack nucleation and that of crack growth - which consists in testing two samples with the same stress concentrators and different cross-sectional dimensions at the notch site is developed. It is assumed that the work of crack nucleation is proportional to the width of the sample face on which the crack originates and the specific energy of crack formation, whereas the work of the crack growth is proportional to the length of crack development and the specific crack growth energy. In case of the sample fracture upon testing, the crack growth length is assumed equal to the sample width. Data on the work of fracture of two samples and their geometrical dimensions at the site of the notch are used to form a system of two linear equations in two unknowns, i.e., the specific energy of crack formation and specific energy of crack growth. The determined specific energy values are then used to calculate the work of crack nucleation and work of crack growth. The use of the analytical method improves the accuracy compared to graphical - extrapolative procedures. The novelty of the method consists in using one and the same form of the notch in test samples, thus providing the same conditions of the stress-strain state for crack nucleation and growth. Moreover, specimens with different cross-section dimensions are used to eliminate the scale effects. Since the specific energy of the crack nu-cleation and specific energy of the crack growth are independent of the scale factor, they are determined only by the properties of the metal. Introduction the specific energy of crack formation and growth makes possible to assign a specific physical meaning to the fracture energy.

scholarly journals Instability analysis of a filament-wound composite tube subjected to compression/bending

2019 ◽  
Vol 28 ◽  
pp. 096369351987741
Author(s):  
Gyula Szabó ◽  
Károly Váradi
Keyword(s):  
Failure Modes ◽  
Slenderness Ratio ◽  
Equivalent Stress ◽  
Bending Test ◽  
Test Machine ◽  
Fe Model ◽  
Rubber Tube ◽  
Nonlinear Buckling ◽  
Cross Sectional ◽  
Composite Tube

The aim of this study is to investigate the global buckling of a relatively long composite cord–rubber tube subjected to axial compression and its cross-sectional instability due to bending by a macromechanical nonlinear finite element (FE) model (nonlinear buckling analysis). Composite reinforcement layers are modelled as transversely isotropic ones, while elastomer liners are described by a hyperelastic material model that assumes incompressibility. Force–displacement, equivalent strain, equivalent stress results along with oblateness and curvature results for the complete process have been presented. It is justified that bending leads to ovalization of the cross section and results in a loss of the load-carrying capacity of the tube. Strain states in reinforcement layers have been presented, which imply that the probable failure modes of the reinforcement layers are both delamination and yarn-matrix debonding. There is a significant increase in strains due to cross-sectional instability, which proves that the effect of cross-sectional instability on material behaviour of the tube is crucial. A parametric analysis has been performed to investigate the effect of the member slenderness ratio on cross-sectional instability of the composite tube. It shows that Brazier force is inversely proportional to the slenderness ratio. It further shows that higher oblateness parameters occur in case of a lower slenderness ratio and that cross-sectional instability takes place at a lower dimensionless displacement in case of a lower slenderness ratio. FE results have been validated by a compression/bending test experiment conducted on a tensile test machine.

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