• Transactions of Materials Processing
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• v.20 no.8
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• pp.568-574
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• 2011

The combination of tailor welded blank (TWB) and hot stamping often offers improved crash-worthiness and reduced mass of stamped parts in the automobile body. To investigate the formability of laser TWB and the reliability of weld line, the present study used 22MnB5 boron steel sheet of the same thickness and used the Erichsen cupping test at elevated temperatures. The effects of laser direction, die temperature, weld line positions and forming speed on formability(the limiting dome height) were studied and the results were compared with the formability of the base material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.429-431
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• 2009

Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND // <111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study, The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND // <111> texture components through asymmetric rolling in Al sheet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.234-237
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• 2007

Deep drawing of magnesium alloy sheet is conducted at elevated temperatures($200{\sim}300^{\circ}C$) to improve the press formability because of low formability at room temperature. Then magnesium alloy sheet formability is known to be very sensitive to the strain rate. In this paper, we conducted warm deep drawing tests of magnesium alloy AZ31 sheet for various punch velocities. We examined the forming velocity effect on the deep drawing formability and the correlation with the tensile test result.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.250-253
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• 2007

Since Mg alloy has many attractive advantages among the practically used metals, many researchers have been studied to develop useful process and material. The crystal structure of Magnesium was hexagonal close-packed, so its formability was poor at room temperature. But formability was improved in high temperature with increasing of slip planes, twins, dynamic recrystallization. In this study The formability of AZ31B magnesium sheet is estimated according to the variable temperatures, forming speed, thickness, blank holding force. The results of deep drawing experiences show that the formability is well at the range from 200 to $250^{\circ}C$, 20 to 60 mm/min forming speed and 2.5 to 3KN blank holding force.

• Transactions of Materials Processing
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• v.7 no.6
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• pp.539-544
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• 1998

Hemi-spheroidal punch stretching test was developed to evaluate the press formability of sheet materials. In the plane strain stretching tests our specially designed hemi-spheroidal head punch were used. In the experiment the circular sheet blanks with parallel edge sides are uniformly stretched up to fracture by raising these punches to assure plane strain stretching deformation along the longitudinal direction of the specimens. The press formability was evaluated by limit punch height(LPH) and minor strain mea-surement around the fracture area. Compared with the hemi-spherical punch and the hemi-cylindrical one our hemi-spheroidal punch was more useful in the experimental reproduction and reliance for press formability test.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.64-72
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• 2022

Since aluminum alloys experience both tensile and compression deformation modes during forming process, it is important to understand the role of deformation mode on the hot formability of metallic alloys. In the present work, the hot formability of Al7050 alloy was investigated by conducting both tensile and Gleeble tests at various temperatures and strain rates. Processing maps representing low efficiency regions were observed at low temperature and high strain rate in both tensile and compressive deformation modes while the maximum efficiency regions depended on different deformation modes. Moreover, samples tested at stable processing conditions presented a smaller pore fraction than those at instable conditions that resulted in crack initiation during plastic deformation. This result shows that different deformation modes during plastic forming can affect formability changes of metallic alloys. Understanding of tension-compression behaviors will help us solve this problem.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.364-369
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• 2003

Non-heat treated steels are attractive in the steel-wire industry since the spheroidization and quenching-tempering treatment are not involved during the processing. However, non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, three different steels such as dual phase steel, low-Si steel, and ultra low carbon bainitic steel were used to study their mechanical properties and the cold formability. The cold formability of three steels was investigated by estimating the deformation resistance and the forming limit. The deformation resistance was estimated by calculating the deformation energy, and the forming limit was evaluated by measuring the critical strain revealing crack initiation at the notch tip of the specimens. The results showed that deformation resistance was the lowest in the low-Si steel, and the forming limit strains of ultra low carbon bainitic steel and low-Si steel were higher than that of commercial SWRCH45F steel.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.175-181
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• 2007

The objective of this study was to develop formability evaluation techniques in order to apply aluminum sandwich panel for automotive body parts. For this purpose, newly adopting formability evaluation (using limit dome height and plane strain test) was carried out in order to secure the fundamental data for the measurement of sheet metal forming and the establishment of optimum forming conditions of the aluminum sandwich panel. The results showed that there were good agreements between the old formability evaluation method and the new method which was more simplified than that of old one. From the results of these formability evaluation, the formability of sandwich panel was higher than that of aluminum alloy sheet alone which was the skin component for the sandwich panel. Also, it was found that sandwich panel could reduce the weight and could have the same flexural rigidity simultaneously when it was compared to the automotive steel sheet.

• Journal of Korea Foundry Society
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• v.26 no.5
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• pp.227-231
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• 2006

Liquid formability of bulk amorphous alloys is known to be very poor due to their high viscosity comparing with conventional metallic materials. It is important to have the fabricating technology of bulk amorphous alloys in order to make the components with complicated shape. Liquid formability includes the mold cavity filling ability and the hot tear(crack) resistance during solidification. A mold made of a commercial tool steel for the formability test was designed. Melting was performed by the arc melting furnace with melting capacity of 200 g in an argon atmosphere. Liquid formability and glass forming ability of Cu base and Ni base bulk amorphous alloys were measured and evaluated. Mold filling ability of Ni-Zr-Ti-Si-Sn alloy was better than that of Cu-Ni-Zr-Ti alloy, however the reverse is the hot tear resistance. Bulk amorphous alloy is very susceptible to crack if partial crystallization occurs during solidification. Crack resistance was thought to be closely related with the glass forming ability.

• Transactions of Materials Processing
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• v.17 no.1
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• pp.52-58
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• 2008

Tube hydroforming process is generally consisted with pre-bending, preforming and hydroforming processes. Among forming defects which may occur in tube hydroforming such as buckling, wrinkling and bursting, the wrinkling and bursting by local instability under excessive tensile stress mode were mainly caused by thinning phenomenon in the manufacturing process. Thus the accurate prediction and suitable evaluation of the thinning phenomenon play an important role in designing and producing the successfully hydroformed parts without any failures. In this work, the formability on hydroformed part for automobile, i.e. engine cradle, was evaluated using finite element analysis. The initial tube radius, loading path with axial feeding force and internal pressure, and preformed configuration after preforming process were considered as the dominant process parameters in total tube hydroforming process. The effects on these process parameters could be confirmed through the numerical experiments with respect to several kinds of finite element simulation conditions. The degree of enhancement on formability with each process parameters such as initial tube radius, loading path and preform configuration were also compared. Therefore, it is noted that the evaluation approach of the formability on hydroformed parts for lots of industrial fields proposed in this study will provide one of feasible methods to satisfy the increasing practical demands for the improvement of the formability in tube hydroforming processes.