Study on Explosive Forming of a Light Alloy Plate

Author(s):  
Hirofumi Iyama ◽  
Shigeru Itoh

The explosive forming is one of the forming methods of metal plates has been performed since 1950. This method is different from usual static press forming. The metal plate is accelerated by underwater shock wave, which is generated by underwater explosion of an explosive. We have tried the experiment of aluminum alloy forming using this method. In this research, a forming limit for aluminum alloy has been clarified from the experimental results. Then, we have tried the numerical simulation for this method using finite difference method. In this research, two methods for forming aluminum plates using closed metal vessel and paper vessel are introduced and the results of numerical simulations corresponding to those experimental conditions are shown.

2019 ◽  
Vol 803 ◽  
pp. 50-54
Author(s):  
Takahiro Ohashi ◽  
Kento Okuda ◽  
Hamed Mofidi Tabatabaei ◽  
Tadashi Nishihara

This paper provides a framework for the transcription of the surface of a mirror-finished die onto a metal plate by friction stir forming (FSF). In FSF, a material is put on a die, then friction stirring was conducted on its back surface for the transcription of the profile of the die onto the material. In this paper, a mirror-polished die of JIS SUS304 stainless steel with surface roughness Sz 0.014 mm and a probe-less friction-stirring tool in 18 mm shoulder diameter were employed for the experiment. A5083P-O aluminum plates, 3 mm thick, were utilized as base metals for the transcription. The authors varied tool spindle speed and tool feed rate to evaluate the forming results. Consequently, a mirror-finished surface under the friction-stirring tool was successfully transferred from the die to the aluminum alloy plate. The roughness of the base metal before processing was Sz 0.022 mm and that of the processed metal was Sz 0.012–0.016 mm. Higher spindle speed and faster feed rate resulted in a smoother surface; it is thought that high spindle speed and faster feed rate should be effective for higher contact pressure between a die and a material.


Author(s):  
Hirofumi Iyama ◽  
Masatoshi Nishi ◽  
Yoshikazu Higa

The explosive forming is a characteristic forming method. This technique is a metal forming using an underwater shock wave. The underwater shock wave is generated by underwater explosion of the explosive. The metal plate is formed with involving the high strain rate on this technique. In generally, the pressure vessel is used in this method due to the effective utilization of the explosion energy. The underwater shock wave is propagated in water and reflected on inside wall of the pressure vessel. This reflected shock wave is affected on the deformation shape of a metal plate. Therefore, the inside shape of pressure vessel is often changed. In other words, the shape of pressure vessel is changed, the shock pressure distribution on the metal plate and it is possible that final deformation shape of the metal plate is changed. Some numerical simulations and experiments have been carried out to clear the influence of the inside shape of pressure vessel in the explosive forming. This paper is included the results and discussions on the numerical simulation and experiment used those conditions.


Author(s):  
Hirofumi Iyama ◽  
Takeshi Hinata ◽  
Shigeru Itoh

The explosive forming is one of the forming methods of a metal plate performed since the 1950s. This method is different from usual static press forming. The metal plate is accelerated by underwater shock wave, which is generated by underwater explosion of an explosive. In order to deform a metal plate in predetermined form with sufficient accuracy using this forming method, it is important to grasp the mechanism. At first, it is necessary to grasp that an underwater shock wave spreads and it collides with the metal plate. And it is also necessary to show clearly what deformation of the metal plate with high-speed. Then, we investigated about the mechanism in the numerical simulation. In this research, LS-DYNA, which is the software for shock analysis was used. Moreover, the experiment was also conducted in order to confirm whether this numerical simulation is exact.


2013 ◽  
Vol 767 ◽  
pp. 132-137
Author(s):  
Hirofumi Iyama ◽  
Yoshikazu Higa ◽  
Shigeru Itoh

Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the effects of the configuration of the pressure vessel on the deformation of a metal plate, numerical simulation was performed. This paper reports those results.


Author(s):  
Hirofumi Iyama ◽  
Shigeru Itoh

Explosive forming is one of the effective metal forming methods using underwater shock wave generated by the detonation of an explosive. The experiment of eccentric spherical free metal forming by this method was carried out. This free metal forming process does not use require expensive metal die. We used simple metal die with only circular edges and considered the metal plate formed to required shape using this method. It was possible to change the pressure distribution applied on the metal plate by changing the set-up position of the explosive and the shape of the device. We have considered this method to cause lessen cost in the small production by various types of metal forming process. In this paper, we introduce the method of eccentric spherical free metal forming using underwater shock wave and present the experimental results. The numerical simulation on this method by FDM (Finite Difference Method) was carried out. In this paper, those results are discussed.


Author(s):  
Hirofumi Iyama ◽  
Masatoshi Nishi ◽  
Yoshikazu Higa ◽  
Ken Shimojima ◽  
Osamu Higa ◽  
...  

The explosive forming is a characteristic forming method. An underwater shock wave is generated by underwater explosion of the explosive. A metal plate is affected high strain rate by the shock loading and is formed along a metal die. Although this method has the advantage of mirroring the shape of the die, a free forming was used in this paper. An expensive metal die is not necessary for this free forming. It is possible that a metal plate is formed with simple supporting parts. However, the forming shape is depend on the shock pressure distribution act on the metal plate. This pressure distribution is able to change by the shape of explosive, a mass of explosive and a shape of pressure vessel. On the other hand, we need the pressure vessel for food processing by the underwater shock wave. Therefore, we propose making the pressure vessel by the explosive forming. One design suggestion of pressure vessel made of stainless steel was considered. However, we cannot decide suitable conditions, the mass of the explosive and the distance between the explosive and the metal plate to make the pressure vessel. In order to decide these conditions, we have tried the numerical simulation of this explosive forming. The basic simulation method was ALE (Arbitrary Laglangian Eulerian) method. Mie-Grümeisen EOS (equation of state), JWL EOS, Johnson-Cook constitutive equation for a material model were applied in the numerical simulation. In this paper, the underwater pressure contours to clear the propagations of the underwater shock wave, forming processes and deformation velocity of the metal plate is shown and it will be discussed about those results.


Author(s):  
Hirofumi Iyama ◽  
K. Raghukandan ◽  
Shiro Nagano ◽  
Shigeru Itoh

Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the influence of the configuration of the pressure vessel on the deformation of a metal plate, numerical analysis was performed. This paper reports those results.


Author(s):  
Hirofumi Iyama ◽  
Shigeru Itoh

Explosive forming is one particular forming technique, in which, most commonly, water is used as the pressure transmission medium. An explosive is set at the top of the pressure vessel filled with water and is exploded by an electric detonator. An underwater shock wave propagates through the water medium and impinges on the metal plate causing it deformation. If a metal die is used, the metal plate deforms to a specified form. Generally, explosive forming has little spring back of the metal plate, because sufficient plastic deformation is obtained. There are two pressure actions to the metal plate on explosive forming. The first pressure pulse is from the shock loading and the second pressure pulse is caused by the expansion gas generated by the detonation of the explosive. The secondary pressure pulse duration is longer, but the peak pressure is lower than the primary shock pressure. The intensity of the pressure pulse is based on the conditions of the pressure vessel. We have also been using the metal die for explosive forming. The deformation shape of the metal plate is effected by a distribution shape of shock loading. In this technique, the pressure vessel has a desired internal shape. The pressure vessel has an internal shape of a parabola. In order to understand the deformation mechanism of the metal plate, some experiments and numerical analysis were carried out.


Author(s):  
Hirofumi Iyama ◽  
Takeshi Hinata ◽  
Shigeru Itoh

In recent years, aluminum alloy is being used to fabricate car bodies. #5000’s or 6000’s aluminum alloy series is widely employed. However, the sheet metal forming of these materials by the static method, such as the hydro bulge forming and general punching, is very difficult, because the formability characteristics are limited when compared to majority of automobile steels. Hence, the choice of explosive forming is considered for forming these aluminum alloys. Te elongation of aluminum alloy by explosive forming is compared with that obtained by punching. The amount of deformation of aluminum alloy by the explosive forming is found to be larger. In addition, a theoretical elucidation is also done. FDM scheme was employed to solve the numerical simulation. In this simulation the detonation process of the explosive, propagation process and deformation process of aluminum alloy were conducted.


2014 ◽  
Vol 496-500 ◽  
pp. 133-136 ◽  
Author(s):  
Lei Chen ◽  
Yong Xiang Hu ◽  
Gang Fang ◽  
Zhen Qiang Yao ◽  
Xing Wei Zheng

Laser peen forming, is a purely mechanical forming method achieved through the use of laser energy to form metal plate with small curvatures. Experiments were performed to investigate the effect of pre-bending on the plate bending deformation induced by laser peen forming. The pre-bending of plate was accomplished by a fixture with the cambered top surface. The pre-bending curvature radius is calculated and is used to design cambered surface. The LPF experiments are performed with Nd: YAG laser with overlapping laser spots. It is found that the convex deformation can be induced after laser shocks. And its curvature radius in the elastically elongated direction can be greatly increased by applying pre-bending, while in the perpendicular direction, the curvature radius is decreased.


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