Finite Element Analysis on Experimental Stretch Forming Process of AA2014 Alloy at 423 to 623K Temperatures

. Sheet metal forming processes are extremely important in the production of many different items. However, the issue of plastic instability, which frequently results in damaged goods, still exists in this industry. To solve this problem during production, it is crucial to take into account a number of factors, limiting diagram of forming. Present case, the Aluminum Alloy (AA2014) has been used to examine its formability at various temperatures (423,523 and 623K) and at strain rates (0.1 mm/s). Stretch forming was used to acquire the study's findings, and the Nakajima test was used. The findings were evaluated using fractography investigations carried out with SEM. The outcomes demonstrated that as the temperature rose, the material's limiting stresses became more favorable. Utilizing LS-dyna software, the simulations were carried out. The experimental findings are within the acceptability limit according to this study.


Introduction
Several industries employ aluminum alloys because of their special qualities, which include light weight, excellent thermal conductivity, and outstanding formability.Aluminum alloys are useful for generating extreme performance, lightweight parts of industries like aero and automobile due to these characteristics.Due to its unique properties, aluminum has been widely used in structural applications for many years.This substance has excellent corrosion resistance, is lightweight but strong, and has superior thermal conductivity.These alloys are excellent for usage in the automotive and aerospace industries thanks to their minimum density and exceptional capacity preventing from corrosion [1][2][3][4][5][6].Aluminum alloys have been widely employed in the aircraft sector ever since the first commercial airplanes were produced.The first alloy used in the creation of airplanes.The initial stage of aluminum alloys is precipitation hardening [7].The main component of the 2xxx class of aluminum alloys is copper with trace amounts of magnesium and manganese also present.Due to its composition, the alloy has a high strength, great shapeability, and good machinability.The reaction between copper and magnesium, which results in precipitation hardening, gives the material its strength.These alloys have a well-deserved reputation for exhibiting high corrosion resistance in both acidic and alkaline conditions.They are suitable for use in aeronautical constructions and other parts that are susceptible to corrosion because of this characteristic.Therefore, the alloys are ideal for use in systems like hydraulic hoses [8][9].
The Al-4.5%Cu alloy (AA2014), an aluminum alloy with 4.5% copper that offers a high strength-to-weight ratio and exceptional machinability, The effects of alloying elements on the precipitation behavior of aluminum alloys and changes to their performance, behavior, and features under fatigue and creep conditions have been the subject of several research.[10][11].The best solutionizing temperature, according to Abass Ali Saleh's research on the effects of treatment of heat on the AA2014 alloy [12], the hardness tended to increase as the soaking time was extended.Hot tensile tests were carried out at six different temperatures, ranging from ambient temperature to 300°C, in a research by Ashok et al. [13] on the mechanical characteristics of the AA2014 alloy.The outcomes demonstrated that found at lower temperatures were the consequence of sub-grain development throughout the deformation process.The mechanical behavior of the AA2014-T6 alloy under tension and compression loads in quasi-static and dynamic conditions was studied by Anoop Kumar Pandouria and colleagues [14].They studied the effects of strain rates ranging from 10-4 to 2 103 s-1 and temperatures ranging from 25 to 250 °C, and they discovered that under both forms of loading, the material's plastic flow stress displayed positive strain rate.Sheet metal formability is the ability of a metal be shaped in a certain without breaking, form or excessively thinning down.The amount of deformation that can occur is nonetheless constrained by the forming limit curve (FLC) of each individual sheet of metal.The FLC frequently Possible localized necking that might result in a ductile fracture.The forming limit diagram (FLD), which is a graph, shows the FLC as the main strain (1) at the start of localized necking for all minor strain values (2).In FLC is divided into two branches, the "left branch" and the "right branch."Only proportional strain routes, which are created utilizing a range of major and minor strain ratios, are subject to the FLC.The "right branch" has strain ratios that go from complete biaxial stretching to plane strain, whereas the "left side" has strain ratios that go from uniaxial tension to plane strain [15][16].The FLD was plotted at various temperatures in the current study, together with a clear analysis of fracture determination.

Experimental details 2.1 Requirements of a material
A metal sheet of AA 2014, measuring 1.0 millimeter in thickness, was selected for testing.Examining the AA 2014 sheet metal's chemical composition and the outcomes are presented in Table 1.This alloy, characterized by a copper content of 4.5%, enhances the strength, hardness, wear resistance, and corrosion resistance of the AA 2014 aluminum alloy.Furthermore, it boosts the alloy's electrical conductivity and its ability to withstand elevated temperatures. ,

Stretch forming Nakazima Test (Hemispherical Dome test)
Utilizing a 20-ton hydraulic press, a 2-zone split furnace, and a temperature controllerand servo-controlled force and displacement mechanisms, the AA2014 material was stretched as part of the experiment.The equipment can work at speeds between 0.00001 mm/min and 250 mm/min.The stretching setup had a 50 mm-hemispherical dome-shaped punch with a diameter, while the blank holding plate included grove bead to prevent material from flowing in the cavity.In Figure 1, several specimens of various lengths are shown.

Forming limit diagram (FLD)
A forming limit diagram (FLD) showing actual major and minor stresses at three different temperatures is shown in Figure 2. Solid lines were used to improve clarity and make it simple to distinguish between the many experimental FLDs.Within the FLD, this delineation aids in separating areas of failure from safe zones.The FLDs include analyses of plane strain, tension-tension (T-T), and tension-compression (T-C) situations.Notably, a difference in slope between the T-T and T-C sectors may be seen.Strain patterns show a buildup and subsequent decrease in the T-C domain, however in the T-T area, this tendency changes with rising process temperature.The forming limit strain shows an improvement of around 18% with a steady increase to 623k.The temperature throughout the time period has a significant impact on the amount of material limiting strains.

Limiting dome height.
Formability is significantly influenced by the phenomenon known as Limiting Dome Height (LDH).As depicted in Figure 3, the LDH is showcased at different temperatures, both through experimental data and predictive analysis.As the material undergoes a softening process, its formability demonstrates an increase, leading to a heightened LDH.Across all designs, the variance between the projected and actual LDH under all temperature conditions remains well within a 5% threshold.

Finite element Analysis of AA2014
The LS dyna software system was used to simulate the stretching procedure using a flat bottom punch.Software called LS Dyna was used to produce the CAD model.The blank holder, the die, the punch, and the blank are all separate parts of the CAD file for the stretch forming process.To streamline the analysis, the punch, die, and blank holder were assigned fixed properties, without the necessity for explicit results or observations.These components were defined with specific fixed attributes within LS dynasoftware.The simulation assumes a uniform friction coefficient of 0.12 between all the components.The simulation depicted in Figure 4 depicts the process under investigation, conducted at a temperature of 623 K.

Conclusion
With the use of FE Simulations and experimental data, the ongoing project on AA 2014 seeks for determine being formed limitations at multiple temperatures.The study came up with a number of important findings, which are listed below.
• Using the Nakajima test technique, the forming behavior of the AA2014 alloy has been studied from 423 to 623K.• Forming Limit Diagram (FLD) and limiting dome height (LDH) determined that the temperature increases from 423,523 and 623K,decreases the stress required and also increases in limiting strain value.• The comparison of Experimental FLD and theoretical FLD of LS dyna simulation are within the acceptance limit.

Fig. 2 .
Fig.2.Forming limit diagram for (323,423 and 623K) temperatures at 0.1/s strain rate and few failure nakazema samples at 323K temperature

Table 1 .
Shows the chemical percentage of elements