**5. Aluminum alloy behavior during hydroforming process**

The metal forming process in which a pressurized fluid either plastically deforms or aids in deforming a given blank material (sheet or tube) into a desired shape as depicted is a hydroforming process. **Figure 4** indicates the complete process. Using this process, more complex shapes with more strength and low cost can be manufactured as compared with stamping, forging, or casting processes [54].

Tube hydroforming process on different aluminum alloys is discussed in the following sections. At different temperatures, tube hydroforming analysis of aluminum alloy AA1050 was studied and the effect of temperature on thickness distribution of the final product was investigated. Also, for evaluating numerical results, a warm hydroforming set-up had been designed and manufactured. Conferring to numerical and experimental results in the case of free bulging, increase of the process temperature causes more uniform thickness distribution which leads to better material formability. A viscoplastic model was developed to consider the influence of microscopic evolution and macroscopic deformation to represent the deformation behavior of aluminum alloy sheet AA7075-O in the warm hydroforming process. By using the pressure rate, the evolution of dislocation density and kinematic isotropic hardening on a hydroforming environment, a set of rate dependent constitutive equations was constructed and proposed to predict stress-strain response of the material. The hydraulic bulge experiments on aluminum alloy at warm temperature indicated that the deformation behavior of the material was more sensitive to pressure rate. To determine the optimum values of a set of free material constants associated with the proposed constitutive model, the genetic algorithm optimization technique was used. The computed data were in good agreement with the test data on the basis of the optimized material constants [55, 56].

Friction stir welding (FSW) tube of 2024-O aluminum alloy rolled plates was coiled and produced by processing sequence. The plastic deformation characteristics were investigated experimentally and numerically during hydroforming with two types of end conditions. The performance of the FSW tubes was investigated by diebulge forming with fixed ends. The wrinkling behavior during hydroforming was analyzed by employing axial feed on the tube ends. Severe thinning was observed at one quarter of the expansion zone from symmetry plane. Along the hoop direction, the base material near the weld observed a severe thinning. The thickness distribution greatly depends on the sequence of the contacting die and the variations of the curvature radius of the tube during hydroforming. Moreover, the weld shows an inhibitory effect for the generation of the wrinkles and decreases the number of the wrinkles as compared to the seamless tube during hydroforming [57].

An experimental and numerical simulation was studied on 6063-T4 aluminum alloy cross member through the hydroforming process. Severe thinning and

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*Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

the requirement of energy conservation [58–60].

flow and raises the plastic deformation [61, 62].

bursting were avoided during hydroforming, composite design method was carried out, and the significance of pre-form structural parameters was discussed on thinning. An experimental research was conducted on thickness distribution of typical sectional profiles and dimension accuracy as per the optimum pre-form shape.

FEM simulations and experiments were conducted on the formability of aluminum alloy AA2024-O. The effects of strain rate on the formability during the active hydroforming process were investigated. Results indicated that aluminum alloy AA2024-O is not sensitive to pressure rate at room temperature. Furthermore, the deformation capacity of aluminum alloys can be improved effectively, and more uniform distribution of wall thickness can be obtained. The wrinkling behavior and thickness distribution of 5A06 aluminum alloy sheets in an annealed state was investigated numerically and experimentally under different hydraulic pressures in the hydroforming of single-layer and double-layer sheets. The upper, thicker sheet synchronously deforms with the lower, thinner sheet during hydroforming. When the double-layer sheets were separated, a thinner curved sheet part will be manufactured. From the simulation and experimental results, the upper, thicker sheet was effectively suppressing the wrinkles of the lower, thinner sheet and improved the thickness distribution. This was due to the increasing anti-wrinkle ability of the formed sheet and the interfacial friction between the double-layer sheets. In addition, the maximum hydraulic pressure was decreased via hydroforming of doublelayer sheets. This method reduced the drawing force for large sheet parts and meets

A specialized hydroforming process set-up was designed for 2A12 aluminum alloy curved shell double-sided sheet. The influence of double-sided liquid pressure on the thickness distribution was evaluated. The thickness distribution of the formed shells was measured and compared under different loading paths. Using simulation analysis, the deformation mode and the stress state were analyzed to understand the mechanism of the thickness variation. It was shown that the forward pressure plays a negative role in the thickness distribution of the formed parts. The deformation mode of the shells varies slightly when forward pressures are added. The Von Mises stress and the effective strain of the components were improved when conducting the double-sided hydroforming process. The larger thinning phenomenon was noted by adding forward pressure and by increasing reduced third principle stress on the blank. Through a steam hydroforming process, an experimental formability study was carried out on aluminum sheet 2017A. The steam hydroforming process takes advantage of the coupling between the thermal and mechanical loads applied. The variation of the supplied electrical power on the hydroforming temperature and steam pressure effects was studied. The evolution of strains and stresses in metal sheets was analyzed. The experimental results showed that the supplied electrical power increases the heating rate and has no effect on bursting temperature or pressure. Furthermore, the evolution of the vapor pressure as a function of temperature was independent of the supplied electrical power and the deformation in the thin sheets under the steam pressure decreases the stress

Using elliptical bulging dies under various temperatures and pressure rates, warm/hot sheet bulging tests were conducted on 2A16-O aluminum alloy. The macroscopic and microscopic influence of the pressure rate on the formability and microstructural evolution of hydrobulging parts during warm/hot sheet hydroforming was investigated. The results revealed that the forming limit of the aluminum alloy was influenced by the pressure rate as the temperature rose, wherein a lower pressure rate resulted in a higher forming limit. This study demonstrated that warm/hot sheet hydroforming of aluminum alloy may lead to an improved forming limit and inhibit microstructural degradation during processing [63]. A

**Figure 4.** *Steps in a typical hydroforming process shown on a small tubular part [54].*

#### *Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

*Aluminium Alloys and Composites*

**5. Aluminum alloy behavior during hydroforming process**

on the basis of the optimized material constants [55, 56].

wrinkles as compared to the seamless tube during hydroforming [57].

*Steps in a typical hydroforming process shown on a small tubular part [54].*

An experimental and numerical simulation was studied on 6063-T4 aluminum alloy cross member through the hydroforming process. Severe thinning and

Friction stir welding (FSW) tube of 2024-O aluminum alloy rolled plates was coiled and produced by processing sequence. The plastic deformation characteristics were investigated experimentally and numerically during hydroforming with two types of end conditions. The performance of the FSW tubes was investigated by diebulge forming with fixed ends. The wrinkling behavior during hydroforming was analyzed by employing axial feed on the tube ends. Severe thinning was observed at one quarter of the expansion zone from symmetry plane. Along the hoop direction, the base material near the weld observed a severe thinning. The thickness distribution greatly depends on the sequence of the contacting die and the variations of the curvature radius of the tube during hydroforming. Moreover, the weld shows an inhibitory effect for the generation of the wrinkles and decreases the number of the

The metal forming process in which a pressurized fluid either plastically deforms or aids in deforming a given blank material (sheet or tube) into a desired shape as depicted is a hydroforming process. **Figure 4** indicates the complete process. Using this process, more complex shapes with more strength and low cost can be manufactured as compared with stamping, forging, or casting processes [54]. Tube hydroforming process on different aluminum alloys is discussed in the following sections. At different temperatures, tube hydroforming analysis of aluminum alloy AA1050 was studied and the effect of temperature on thickness distribution of the final product was investigated. Also, for evaluating numerical results, a warm hydroforming set-up had been designed and manufactured. Conferring to numerical and experimental results in the case of free bulging, increase of the process temperature causes more uniform thickness distribution which leads to better material formability. A viscoplastic model was developed to consider the influence of microscopic evolution and macroscopic deformation to represent the deformation behavior of aluminum alloy sheet AA7075-O in the warm hydroforming process. By using the pressure rate, the evolution of dislocation density and kinematic isotropic hardening on a hydroforming environment, a set of rate dependent constitutive equations was constructed and proposed to predict stress-strain response of the material. The hydraulic bulge experiments on aluminum alloy at warm temperature indicated that the deformation behavior of the material was more sensitive to pressure rate. To determine the optimum values of a set of free material constants associated with the proposed constitutive model, the genetic algorithm optimization technique was used. The computed data were in good agreement with the test data

**160**

**Figure 4.**

bursting were avoided during hydroforming, composite design method was carried out, and the significance of pre-form structural parameters was discussed on thinning. An experimental research was conducted on thickness distribution of typical sectional profiles and dimension accuracy as per the optimum pre-form shape.

FEM simulations and experiments were conducted on the formability of aluminum alloy AA2024-O. The effects of strain rate on the formability during the active hydroforming process were investigated. Results indicated that aluminum alloy AA2024-O is not sensitive to pressure rate at room temperature. Furthermore, the deformation capacity of aluminum alloys can be improved effectively, and more uniform distribution of wall thickness can be obtained. The wrinkling behavior and thickness distribution of 5A06 aluminum alloy sheets in an annealed state was investigated numerically and experimentally under different hydraulic pressures in the hydroforming of single-layer and double-layer sheets. The upper, thicker sheet synchronously deforms with the lower, thinner sheet during hydroforming. When the double-layer sheets were separated, a thinner curved sheet part will be manufactured. From the simulation and experimental results, the upper, thicker sheet was effectively suppressing the wrinkles of the lower, thinner sheet and improved the thickness distribution. This was due to the increasing anti-wrinkle ability of the formed sheet and the interfacial friction between the double-layer sheets. In addition, the maximum hydraulic pressure was decreased via hydroforming of doublelayer sheets. This method reduced the drawing force for large sheet parts and meets the requirement of energy conservation [58–60].

A specialized hydroforming process set-up was designed for 2A12 aluminum alloy curved shell double-sided sheet. The influence of double-sided liquid pressure on the thickness distribution was evaluated. The thickness distribution of the formed shells was measured and compared under different loading paths. Using simulation analysis, the deformation mode and the stress state were analyzed to understand the mechanism of the thickness variation. It was shown that the forward pressure plays a negative role in the thickness distribution of the formed parts. The deformation mode of the shells varies slightly when forward pressures are added. The Von Mises stress and the effective strain of the components were improved when conducting the double-sided hydroforming process. The larger thinning phenomenon was noted by adding forward pressure and by increasing reduced third principle stress on the blank. Through a steam hydroforming process, an experimental formability study was carried out on aluminum sheet 2017A. The steam hydroforming process takes advantage of the coupling between the thermal and mechanical loads applied. The variation of the supplied electrical power on the hydroforming temperature and steam pressure effects was studied. The evolution of strains and stresses in metal sheets was analyzed. The experimental results showed that the supplied electrical power increases the heating rate and has no effect on bursting temperature or pressure. Furthermore, the evolution of the vapor pressure as a function of temperature was independent of the supplied electrical power and the deformation in the thin sheets under the steam pressure decreases the stress flow and raises the plastic deformation [61, 62].

Using elliptical bulging dies under various temperatures and pressure rates, warm/hot sheet bulging tests were conducted on 2A16-O aluminum alloy. The macroscopic and microscopic influence of the pressure rate on the formability and microstructural evolution of hydrobulging parts during warm/hot sheet hydroforming was investigated. The results revealed that the forming limit of the aluminum alloy was influenced by the pressure rate as the temperature rose, wherein a lower pressure rate resulted in a higher forming limit. This study demonstrated that warm/hot sheet hydroforming of aluminum alloy may lead to an improved forming limit and inhibit microstructural degradation during processing [63]. A

hydroforming analysis was made on extruded aluminum tubular specimen made up of AA 6063 alloy bulged from the diameter of 38–54 mm. The thickness distribution at bulging the region along lateral and longitudinal directions was analyzed. The parameters considered are axial feed, tube thickness, fluid pressure, and die semi-cone angle. The forming characteristics such as thickness distribution and bulged diameter were studied using toolmaker microscope and coordinate measuring machine. Maximum shear thinning is observed in the largest diameter of the bulged portion of the tube [64].

### **6. Aluminum alloy behavior during bi-axial forming**

Here, some of the recent discussions are made based on the bi-axial forming process. It is also treated as a stretching process in which sheet material experiences the tensile load along plane direction in the same time.

Biaxial warm forming behavior in the temperature range 200–350°C was investigated for three aluminum sheet alloys: Al 5754, Al 5182, and Al 6111-T4. The formability for all the three alloys improved at elevated temperatures; the strain hardened alloys Al 5754 and Al 5182 showed considerably greater improvement than the precipitation hardened alloy Al 6111-T4. Formability was studied by forming rectangular parts at a rapid rate using internally heated punch and die in both isothermal and nonisothermal conditions. The temperature effect on drawing of the sheet was found to have a large effect on formability. FLD under warm forming conditions was also determined, which showed results that are consistent with the evaluation of part depth. Biaxial forming behavior was investigated for three aluminum sheet alloys of Al 5182, Al 5754, and 6111-T4 using a heated die and punch in the warm forming temperature range of 200–350°C. It was found that all three alloys exhibited significant improvement in the formability compared with that at room temperature. The nonheat-treatable alloys of AA 5182 and AA 5754 showed a higher part depth than that of heat-treatable 6111-T4. The formidability characteristic was dependent on the blank holding pressure (BHP). When the BHP decreased, the formability increased, but increasing the forming temperature and/ or BHP minimizes the wrinkling tendency and improves the forming performance. By increasing temperature and BHP, the stretchability of the sheet alloys was increased. Through setting the temperature 50°C higher than the punch temperature to enhance the drawing component, the optimum formability was achieved. Strain distribution was also improved with setting the die temperature higher than the punch temperature in a part in such a manner that postpones necking and fracture by altering the location of the greatest thinning [65].

The Gurson-Tvergaard-Needleman (GTN) damage model combined with the finite element method was used to investigate the influence of double-sided pressure on the deformation behavior of biaxially stretched AA6111-T4 sheet metal. The Marciniak-Kuczynski (M-K) localized necking model was used to predict the right-hand side of the forming limit diagram (FLD) of sheet metal under superimposed double-sided pressure. The forming limit curve (FLC) of the biaxially stretched AA6111-T4 sheet metal under the superimposed double-sided pressure had improved and the fracture locus shifts to the left. Besides, the formability increase value is sensitive to the strain path [66].

Through the numerical biaxial tensile tests of the sheet, the biaxial tensile deformation behavior of 5182 aluminum alloy sheet was predicted. From the numerical simulations, the stress-strain curves and the shapes of the contours of plastic work were calculated and were quantitatively verified by the experimental biaxial tensile test using the cruciform specimen. Using the results of experimental and numerical

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**Author details**

**7. Summary**

Perumalla Janaki Ramulu

alloys can help the industries.

University, Adama, Ethiopia

provided the original work is properly cited.

Program of Mechanical Design and Manufacturing Engineering, School of

\*Address all correspondence to: perumalla.janaki@astu.edu.et

Mechanical, Chemical and Materials Engineering, Adama Science and Technology

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Forming behavior of different aluminum alloys is discussed in the above sections. The forming processes considered included the hot forming process, deep drawing process, incremental process, hydroforming process, and bi-axial forming. The effect of their parameters on aluminum alloys is realized. From each forming process and test, the forming limit strain is determined to quantify the formidability of each aluminum alloy. Moreover, the quantification of the formability of Al

biaxial tensile tests, parameters of the Yld2000-2d yield function were identified. Von Mises's and Hill's yield functions were identified using the experimental data and were compared. The simulation results confirmed that the forming simulation using the Yld2000-2d yield function identified by the numerical biaxial tensile tests was better than that of the Mises's and Hill's yield functions and was comparable to

The forming limit strains at fracture for aluminum alloy 5086 were determined using an in-plane biaxial tensile test with a cruciform specimen. To identify the onset of fracture and the forming limit strains, a method based on the evolution of strain in the central area of the specimen and the observation of the macroscopic image of specimen surface was proposed. The forming limit strains at fracture were determined under different strain paths provided by the two independent axes of the experimental device. Finite element simulations were performed to determine and compare numerical forming limit strains with three ductile fracture criteria [68]. Warm temperature biaxial tension test apparatus was developed to achieve stress ratio and strain rate controls simultaneously. The warm temperature biaxial tension tests were conducted on AA5182-O aluminum alloy sheet with the thickness of 1 mm. The obtained results showed that the shapes of equi-plastic work loci did

that of the Yld2000-2d yield function calibrated experimentally [67].

*Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

not have strong temperature dependency [69].

#### *Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

biaxial tensile tests, parameters of the Yld2000-2d yield function were identified. Von Mises's and Hill's yield functions were identified using the experimental data and were compared. The simulation results confirmed that the forming simulation using the Yld2000-2d yield function identified by the numerical biaxial tensile tests was better than that of the Mises's and Hill's yield functions and was comparable to that of the Yld2000-2d yield function calibrated experimentally [67].

The forming limit strains at fracture for aluminum alloy 5086 were determined using an in-plane biaxial tensile test with a cruciform specimen. To identify the onset of fracture and the forming limit strains, a method based on the evolution of strain in the central area of the specimen and the observation of the macroscopic image of specimen surface was proposed. The forming limit strains at fracture were determined under different strain paths provided by the two independent axes of the experimental device. Finite element simulations were performed to determine and compare numerical forming limit strains with three ductile fracture criteria [68]. Warm temperature biaxial tension test apparatus was developed to achieve stress ratio and strain rate controls simultaneously. The warm temperature biaxial tension tests were conducted on AA5182-O aluminum alloy sheet with the thickness of 1 mm. The obtained results showed that the shapes of equi-plastic work loci did not have strong temperature dependency [69].
