Explosive Forming Research Articles

Investigation on Zonal Characteristics in Soil of Synchronous Explosion Forming

Synchronous explosion forming, which takes advantage of the thixotropy of concrete or cement mortar and the condensability of soil under blasting concussion, is a newly developed method to construct underground cavities. In this paper, the mechanism of the new method is elucidated first, and then the zonal characteristics in soil are investigated emphatically. In order to accomplish comparative analysis, both synchronous explosion forming and conventional compression blasting experiments are conducted under same soil and explosive conditions. Experimental results indicate that the zonal characteristics in soil by synchronous explosion forming differ from that of by conventional compression blasting. When the new method is applied, formation and growth of cracks in soil during blasting is restrained, and the crannied region, which is usually produced in conventional compression blasting can be substituted by a soil- cement mortar occlusive region. Additional, the compaction range in soil is large when the new method is used. The zonal characteristics of synchronous explosion forming are more advantageous to the bearing capacity of soil and secular stability of cavity.

2815 爆発成形中の金属板の挙動に関する数値シミュレーション(S36-1 高エネルギー加工(1),S36 高エネルギー加工)

2815 爆発成形中の金属板の挙動に関する数値シミュレーション(S36-1 高エネルギー加工(1),S36 高エネルギー加工)

2813 マグネシウム合金の高温爆発成形に関する研究(S36-1 高エネルギー加工(1),S36 高エネルギー加工)

In recent years, demand of a Magnesium alloy is increasing as a lightweight material. However, forming of Magnesium alloy in room temperature is difficult. Therefore, development of new Mg alloys and new forming methods are under investigation. In this research, the explosive forming method is used for the forming AZ31 Magnesium alloy. The explosive forming method is one of the high velocity forming methods, which enables achieving a high plastic deformation for some alloys. The purpose of this research is development of a device that can safely do the high temperature explosive forming.

Experimental evaluation and finite element simulation of explosive forming of a square cup from a brass plate assisted by a lead plug

A FE model is developed to simulate the experimental tests for the impulsive deep drawing of a brass square cup with the presence of a lead plug. The loading of the assembly is achieved by the detonation of a high explosive, underwater. The formability of the brass plate in the absence of the lead plug gives rise to material instability and uneven material thickness over the formed region causing rupture. The presence of lead plug initially slows down the forming process by acting as a reservoir for the kinetic energy. As the deformation progresses, kinetic energy in the plug is transferred to the plate and the increased time scale of the operation enables the system to be treated as a quasi static forming process. In addition to postponing the onset of material instability, the presence of the lead plug enables a higher ratio of drawability and a better uniformity in thickness of the formed dome. The experimental investigations have indicated that the optimum shape of the plate specimen is a square blank with circular cut-off segments. The effects of the medium impedance, wave reflection and refraction are considered to be negligible in order to improve the simplicity of the modelling procedure. Finally, the computed results are compared with those obtained from experimental tests.

Fast exothermic processes in porous silicon

It is found that rapid oxidation of porous Si (por-Si) layers in air may occur in the form of combustion or explosion. Combustion occurs in por-Si layers thinner than 60 μm and impregnated with potassium nitrate, while explosion is observed in thicker porous layers. It is suggested that explosion develops by a thermal mechanism resulting from an exponential increase in the reaction rate with temperature.

A method for symbolic analysis of security protocols

In security protocols, message exchange between the intruder and honest participants induces a form of state explosion which makes protocol models infinite. We propose a general method for automatic analysis of security protocols based on the notion of frame, essentially a rewrite system plus a set of distinguished terms called messages. Frames are intended to model generic crypto-systems. Based on frames, we introduce a process language akin to Abadi and Fournet's applied pi. For this language, we define a symbolic operational semantics that relies on unification and provides finite and effective protocol models. Next, we give a method to carry out trace analysis directly on the symbolic model. We spell out a regularity condition on the underlying frame, which guarantees completeness of our method for the considered class of properties, including secrecy and various forms of authentication. We show how to instantiate our method to some of the most common crypto-systems, including shared- and public-key encryption, hashing and Diffie–Hellman key exchange.

Some considerations for 3D EFP computations

This article identifies some issues, options and results associated with 3D Explosively Formed Penetrator (EFP) computations. The three broad categories of interest (for Lagrangian computations) are the sliding/contact interfaces, the type and arrangement of elements, and the generation of the grid. The sliding/contact algorithm uses a virtual particle approach that is very robust, and it is described in detail. Tetrahedral elements are considered for both symmetric and non-symmetric arrangement, each with some advantages and disadvantages. A mixed element algorithm is also considered for the non-symmetric arrangement, in an effort to eliminate some of the locking that occurs for the non-symmetric arrangement. Hexahedral (brick) elements are not considered herein, but some of the effects (for tetrahedral elements) also apply to hexahedral elements. For axisymmetric EFPs there are also some trade-offs (symmetric grid vs. equally sized elements) associated with the generation of the grid. Computational results are provided to illustrate each of the issues and effects. The virtual particle algorithm is also well suited for high-velocity impact computations, and an example is included to demonstrate this capability for a complex problem.

Evolutionary design of generalized polynomial neural networks for modelling and prediction of explosive forming process

Some aspects of explosive forming process have been investigated experimentally and modelled using generalized GMDH-type (group method of data handling) neural networks. In this approach, genetic algorithm (GA) and singular value decomposition (SVD) are deployed simultaneously for optimal design of both connectivity configuration and the values of coefficients, respectively, involved in GMDH-type neural networks which are used for modelling of centre deflection, hoop strain and thickness strain of explosive forming process. In particular, the aim of such modelling is to show how these characteristics, namely, the centre deflection, the hoop strain and the thickness strain change with the variation of important parameters involved in the explosive forming of plates. In this way, a new encoding scheme is presented to genetically design the generalized GMDH-type neural networks in which the connectivity configuration in such networks is not limited to adjacent layers. Such generalization of network's topology provides optimal networks in terms of hidden layers and/or number of neurons so that a polynomial expression for dependent variable of the process can be achieved consequently. It is also demonstrated that singular value decomposition (SVD) can be effectively used to find the vector of coefficients of quadratic sub-expressions embodied in such GMDH-type networks.

Study on the Effect of Underwater Shock Wave and Gas Expansion in Explosive Forming

Study on the Effect of Underwater Shock Wave and Gas Expansion in Explosive Forming

WS-3 衝撃波の発生制御とその応用(WS(1), 衝撃エネルギー科学の深化と応用)

When an explosive is detonated a shock wave with a very high impulsive pressure is generated and propagated in a medium contacts with the explosive. Such a pressure action on material produces a response of the material different with the common processes. This report deals with material processing such as explosive forming, welding and the generation of very high shock pressure which the author has investigated with researchers in Sojo Univ. and Kumamoto Univ.. These processes are discussed here on how an effective action of shock pressure useful for each processing must be created by controlling the action.

Ultrahigh-strain-rate plastic deformation of a stainless-steel sheet with TiN coatings driven by laser shock waves

In this paper, a novel dynamic ultrahigh-strain-rate forming method driven by laser impact is reported. The technique is based on a mechanical, not thermal, effect. It is found that the ultrahigh-strain-rate is the most important feature for laser shock forming. Usually it is about 107–109 s-1, two or more orders of magnitude higher than that of explosive forming, a method with the largest strain rate previously. Studies on the hardness and residual stress of the surfaces indicate that laser shock forming has some peculiarities other forming methods lack. It introduces strain hardening and compressive residual stresses on both surfaces of the metal sheet, resulting in an obvious improvement in fatigue and corrosion resistance. We also discover some non-linear plastic deformation characteristics in laser shock forming.

816 爆発成形法における圧力容器の影響

816 爆発成形法における圧力容器の影響

Experimental investigation of the thermal properties of carbon at high temperatures and moderate pressures

A consistent procedure for plotting the carbon melting and boiling coexistence curves based on published data and the authors' experimental results is proposed. The parameters of a triple point are predicted to differ markedly from the currently accepted values: pt ≈1 bar and Tt ≈ 4000 K. Two types of experimental facilities were used, with laser heating of samples in one and direct ohmic heating in the other. The existence of a carbyne region (a stable linear polymer consisting of carbon atoms) in the carbon phase diagram is discussed. Results on the direct solid-phase graphite – carbyne transition are presented, and this is shown to occur under certain conditions in the form of a thermal explosion.

Applications and capabilities of explosive forming

All processes, after sufficient time, are visited by a new generation of workers that contemplates process merits and demerits for specific applications. The process that is presently being revisited by academics and industry together is explosive forming. For over 100 years, it has been recognised that explosives can be used in a controlled way in the manufacture of profiled metal components. The required profile results from the explosive force that directly or indirectly deforms the metal. Explosive forming is a broad term covering many process variations. Early patents relating to explosive forming appeared at the end of the 19th and at the beginning of the 20th century. An increasing number of economically successful applications were being seen in the early 1970s, with the manufacture of large aluminium and high strength steel parts. The work presented in this paper results from a global review of activities undertaken in the area of explosive forming, explains the reason for the work, examines explosive forming applications, the associated metallurgy and reviews manufacturing requirements.

New trials for free metal forming using underwater shock wave cylindrical free forming

Explosive forming is a metal forming method using underwater shock wave generated by underwater explosion of explosive. This technique is superior to static forming techniques on the duplication of the shape of the die, because the metal plate can obtain a great work-hardening. It is not necessary upper die used for static forming techniques such us the press forming. We have researched this method and developed the equipment for lower costs of metal forming obtained appointed shape using underwater explosive forming technique. As a new method, we have considered the free metal forming. Before proceeding with this research, we must cover a fundamental problem. Therefore, we have done experimental and analytic investigation for free metal forming using underwater shock wave. In this paper, we present experimental and numerical simulation results.

501 爆発成形法によるパイプの加工に関する研究

501 爆発成形法によるパイプの加工に関する研究

Reply to the discussion by S. Chatterji of the paper “Mercury porosimetry—an inappropriate method for the measurement of pore size distributions in cement-based materials”

This work discusses the impact consequences of Explosively Formed Projectiles (EFP) on the process of armor penetration. Based on the example of piercing shields made of armor steel ARMOX 370T with anti-vehicle mine of MPB type to verify the effectiveness of EFP charge. The influence of the projectile on the armor wall was analyzed on the basis of metallographic examination of the material from the armor, its plastic deformation and the change in the structure of the material within the shock influence area. As a result of the slug projectile impact on the armor surface a crater as a hole was formed with a diameter of approx. 105–120 mm, with noticeable traces of dynamic plastic deformation which occur at high speeds and high temperatures. In addition, microstructure analysis of the mines liner was performed, as in before and after piercing based on the analysis of EDS for phase precipitates identification.

Hyperthermie maligne anesthésique et syndrome de défaillance multiviscérale

The typical explosive form of malignant hyperthermia caused by following isoflurane anaesthesia is a well-known phenomenon. Nevertheless, since dantrolene is used, its evolution toward a multiple organ failure has been rarely described. We report a case of typical explosive malignant hyperthermia caused by an isoflurane anaesthesia complicated by a cardiovascular failure, a disseminated intravascular coagulation, an acute liver failure and an acute renal failure. Afterwards, muscle weakness of the right calf was the only aftermath.

Industrial Applications of the Superplastic Explosive Forming

The impulsive forming is widely used in the modern industry. The superplastic impulsive forming isn't well known, though could have useful applications. Applied aspects of the superplastic impulsive forming problem, including both control external stress and heat influence parameters are stated in the present research. The problem is reproduced in the vector representation of optimizing functions. In the case of the limited number of measurements the task leads to well known scal. r representations with similar physical characteristics. In the technological processes considered here forming pressures are generated by the impulsive energy sources on the base of high explosives. Preheating of the deformed workpiece is performed from the autonomous heat power source or workpieces are heated during forming process.

Explosive forming of thin-wall semi-spherical parts

This paper discusses the special forming method of thin-wall semi-spherical parts, introducing the basic fundamentals of explosive forming, design principles of shell-structures and related technological parameters. Investigation shows that non-die explosive forming is the most effective manufacturing method of such parts (G. Changji, T. Zheng, L. Zhengsheng, Non-Die Explosive Forming of Spherical Containers, Journal of Pressure Vessels, May, 1991.) having the advantages of good forming results, high dimensional accuracy and simplicity of the process and thus may be used as a new forming method for the spherical parts.