Explosion, Shock Wave and Hypervelocity Phenomena in Materials II

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Authors: Toshiaki Watanabe, Hironori Maehara, Shigeru Itoh
Abstract: The aim of this study is to confirm a new technique that can crush ice by underwater shock wave generated by underwater explosion of explosive. Damage caused by ice occurs in the cold regions at different circumstances. For example, the problems such as accretion of ice on the drainage of snow melting system, on the ship and on farm lands. The solution for such problems is to use a method of heating. As the necessary quantity of heat is enormous and the problem of global warming exists, the dynamic way of solving is desirable. At first, we carried out experiments using detonating cord and ice block. The process of propagation of shock wave in ice was observed by using the high-speed camera.
Authors: Sang Sik Lee, Choong Ho Lee, Young Tae Cho
Abstract: Si-Mn spring steel (JIS SUP 9) is primarily employed in the construction of coil springs, particularly those used in soil cultivators deployed in harsh environments. This is due to its specific properties, which allow it to resist permanent deformation, and also provide rapid and effective vibration relief. Si-Mn spring steel (JIS SUP 9) for use in such projects is normally subjected to oil quenching and heat treatment, in order to strengthen its resistance to both impact and fatigue. Unfortunately, oil quenching is associated with environmental issues, most notably pollution and the contamination of wastewater with oil. Therefore, the objective of this study was to describe an alternative aqua quenching for use with this heat treatment. However, aqua quenching has traditionally conferred a lower tensile laod than does oil quenching. This problem of lesser tensile load was solved by properly controlling the density and temperature of the aqua quenching liquid, as well as careful mixing. As a result, it has proven possible to achieve results with aqua similar to those conferred by oil quenching, with regard to chemical components, tensile load, and surface hardness. The tensile load results achieved by oil quenching were 13,145 Pa and 17,177 Pa, and the tensile loads achieved with aqua quenching were 15,392 Pa, 16,804 Pa, 17,923 Pa, and 18,668 Pa. Therefore, the results of our experiments demonstrated the appropriacy and efficacy of this aqua quenching technique as a component of heat treatment for Si-Mn spring steel (JIS SUP 9).
Authors: Tadashi Hasebe, Yutaka Imaida
Abstract: This paper proposes new impact testing methods applicable to sheet metals both under tension and compression based on widely used split Hopkinson pressure bar (SHPB) technique. Explicit dynamic finite element simulations by using LS-DYNA 3D are systematically conducted for several specimen clamping conditions to seek the appropriate methodologies to realize the two tests. For the tensile test, a method which can reduce stress oscillations that usually appear in the measured stress-strain curves is proposed and is devised to be used with SHPB technique. For the compression test, a candidate which can restrict buckling of the specimen is proposed. The method uses a special die-set sandwiching the sheet metal specimen which is simultaneously compressed without disturbing the planar stress wave to be propagated.
Authors: In Young Yang, Yong Jun Yang, Kil Sung Lee, David K. Hsu, Kwang Hee Im
Abstract: Owing to the advantages associated with their very large strength-to-weight and stiffnessto- weight ratios, composite materials are attractive for a wide range of applications. Increasingly, high performance engineering structures are being built with critical structural components made from composite materials. In particular, the importance of carbon-fiber reinforced plastics (CFRP) has been generally recognized in both space and civil aircraft industries, and CFRP composite laminates are widely used. It is very important to detect fiber orientation error in orthotropic composite laminates because the layup of a CFRP composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. In this study, a new approach was investigated on detection of fiber orientation with using two longitudinal and a shear wave ultrasonic transducers for the orthotropic composite laminates. During testing, the most significant problem is that the couplant conditions do not remain the same because of changing the viscosity of the couplant. Therefore, making a design for generating shear wave with longitudinal transducers would greatly aid in alleviating the couplant problem. A pyramid with an isosceles triangle was made of aluminum in order to generate shear waves using two longitudinal transducers based on ultrasonic-polarized mechanism. It is found that the shear wave was very sensitive to fiber of CFRP composite. Finally, a CFRP composite material was nondestructively characterized in order to measure fiber orientation error area using automated data acquisition C-scan system.
Authors: Je Woong Park, In Young Yang, Kwang Hee Im, David K. Hsu, Sung Jin Song, Hak Joon Kim, Young Tae Cho
Abstract: In particular, CFRP (carbon fiber reinforced plastics) composite materials have found wide applicability because of their inherent design flexibility and improved material properties. CFRP composites were manufactured from uni-direction prepreg sheet in this paper. However, impacted composite structures have 50-75% less strength than undamaged structures. It is desirable to perform nondestructive evaluation to assess material properties and part defect in order to ensure product quality and structural integrity of CFRP. In this work, a CFRP composite material was nondestructively characterized and a pitch-catch technique was developed to measure impacteddamaged area using an automated-data acquisition system. Also one-sided mode was performed to scan defect both manual contact measurement and an immersion tank. It is found a pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite, including fiber orientation, low level porosity, ply waviness, and cracks. The paper describes the depth of the sampling volume with the head-to-head miniature Rayleigh probes and also ultrasonic C-scan images are acquired experimentally using one-sided measurement and a conventional scanner.
Authors: P. Manikandan, Kazuyuki Hokamoto, Seyed Hadi Ghaderi, Naresh N. Thadhani
Abstract: The jet formed from the high velocity collision of metal plates have proven both scientifically unique and of potential interest, although the underlying deformation mechanism remains less firmly established. In this study, oblique collision of titanium and stainless steel observed by high-speed camera is discussed. The nature of jet, its velocity and its existence at low velocity are all discussed and theoretical developments are connected. Microstructural studies are done on the sample welded using gas gun and a comparison with explosive welded sample is made.
Authors: P. Tamilchelvan, Krishnamorthy Raghukandan, N. Meikandan, K. Sivakumar
Abstract: The paper deals with detailed studies on the bond zone morphology of Cu / Ss, Br / Ss, Al / Ss weld combinations of explosive welds. The study becomes significant in view of the importance and wide applicability of these materials in bimetal industry. Explosive welding is a high-energy rate fabrication technique and is increasingly employed to provide sound metallurgical bonding between similar and dissimilar metals with widely varied properties. In this study for the same explosive loading conditions, the different types of bonds obtainable at the interface for three combinations of materials have been investigated. The bond zones showed characteristic features, typical of the explosive welding process. Complex patterns of plastic flow and formation of solidified melt areas were revealed at the interface.
Authors: Krishnamorthy Raghukandan, P. Tamilchelvan, N. Meikandan
Abstract: Explosive cladding is a non-conventional, solid-phase bonding technique in which bonding between two plates is produced by their high velocity collision induced by the use of explosives. Attempts were made to explosive clad Titanium-Stainless steel (SS 304 L) plates (3.5 and 3.0 mm thick respectively). The experiments were designed to analyze the bonding interface parallel to the detonation direction. The presence of intermetallics, caused by the melting at the interface due to kinetic energy dissipation, was observed in some locations. The process parameters of the explosive welding of Titanium-Stainless steel combination are defined using the microstructural observations, microhardness at the interface, the results of X-ray diffraction study. A weldability window is also constructed for explosive welding of Ti /Ss.
Authors: Seyed Hadi Ghaderi, Akihisa Mori, Kazuyuki Hokamoto
Abstract: Explosion welding has produced a large number of dissimilar joints. But the explosion welding of materials of low impact toughness and brittle nature is considered to be difficult. Magnesium, with its HCP structure, has a low capacity for plastic deformation at room temperature and moreover it has a high chemical reactivity. Therefore, successful explosion welding of magnesium alloys, demands careful attention to be paid to prevent failure or formation of brittle reacted zones at the weld interface. Explosive welding of the wrought Mg-Al-Zn alloy and commercially pure aluminum is performed. The welds are analyzed through metallographic characterization and shear tests. High quality welds of the two materials possessing shear strength higher than the softer layer has been obtained.
Authors: Peter Nesvadba, Stanislav Rolc
Abstract: The technology of explosive welding (EXW) was used for development of metallic multilayer ballistic resistant materials. Explosive cladded two or multilayer materials serve as final product or as semi-finished product for further processing, e.g. rolling. The objective is to create material with sufficient ballistic resistance at relatively small thickness of the resulting multilayer structure. Under retaining the weight of armoured vehicle its ballistic resistance can be increased or, under retaining its existing ballistic resistance the weight can be reduced. Resulting material should be producible of commercially available metallic materials using common technologies, especially the technology of roll welding (ROW). For the primary tests it is possible to model the resulting structure by means of EXW and some its properties can be verified in the initial stage of research of the multilayer structure (e.g. tests of heat processing, verification of diffusion processes, behaviour under various types of load, verification of ballistic resistance and other technological tests). Subsequently, production can start of large semi-finished products by means of ROW technology. Effective preparation is possible of the samples of multilayer materials by means of EXW technology in various material combinations - armour steel, tool steel and interlayer based on nickel, nickel alloys etc.

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