Compact and Integrated High-Power Pulse Generation and Forming System

This paper presents comprehensive analytical, numerical and experimental research of the compact and integrated high-power pulse generation and forming system based on the flux compression generator and the electro-explosive forming fuse. The paper includes the analysis of the presented solution, starting from the individual components studies, i.e., the separate flux compression generator tests in field conditions and the forming fuse laboratory test, through the formulation of the extended quasi-empirical components models aimed at enabling their optimal parameters determination at the early design stage and ending with the description of the integrated system studies in field conditions. Based on detailed research, it was possible to achieve very high parameters of the generated pulses, i.e., overvoltages of up to 340 kV with the available source power reaching 25 GW. A very high convergence of the simulation and the results of experimental research has been obtained. The parameters of the presented system have been compared with other literature solutions and the selected topology of the high power pulse generation and forming system has been distinguished against other available ones, e.g., based on Marx generators and forming lines.

Application of intelligently controlled technologies in designing of technological processes for explosive forming of shell parts

The object of research is the processes of pulse metalworking (hydroexplosive, magnetic pulse, electrohydraulic, gas detonation forming, etc.). Among these methods of forming for the production of aircrafts engines parts from cylindrical and conical blanks, the most efficient in terms of its energy capabilities and overall dimensions is explosive. The modern level of theory and practice of metal forming processes allows, on the basis of a systematic approach and control theory, to determine the optimal parameters of plastic forming processes, select the best technical solutions, and create a precondition for the transition to complex automation. The most difficult task of metals forming methods optimizing is to find the best solution among many potentially possible ones, considering the introduced restrictions and efficiency criteria, environmental, economic, technical, ergonomic, and other requirements. The most problematic is that it is impossible to optimize the process of forming post-factum (finishing works, elimination of defects in shape and size, welding of cracks, etc. are required), therefore, when solving optimization problems, the implementation of the feedback principle is required - comparison of the value of the controlled variable, determined by the control program, with the desired value. In general, the processes of metal forming by pressure are characterized by a variety of problems of the theory of optimal control, the solution of which is carried out by methods of mathematical programming. And, although the equipment for pulse processing can have a different design, it necessarily includes structural elements that make it possible to convert the energy of the source and with its help (through the action of a solid body, transmitting medium, or field) to deform the metal of the workpiece. Due to this, in this work, it is proposed to control the quality of the obtained parts by varying the degree of deformation of the workpiece in the process of forming. The result of the work is the development of an integrated intelligent system, with the help of which it is possible to carry out the computer-aided design of almost all pulse-action processes based on the intelligent selection of suitable forming parameters.

The influence of strain rate on the cavitation time and deformation of an underwater impulsively rectangular plate

The effect of strain rate on the cavitation time and elastoplastic deformation of steel rectangular plate subjected to underwater explosion load is analytically and numerically investigated in this study. At the cavitation time, the total pressure of the explosion is eliminated so that the cavitation time plays a significant role in the elastoplastic deformation of underwater explosive forming of plate. Taking into account the strain rate effect, the Cowper-Symond constitutive equation of mild steel is employed. Exact linear solution using the Eigen function and numerical linear and nonlinear solution using finite difference method (FDM) of dynamic response of impulsively plate is obtained. Implementing the linear work hardening, the stress, strain, displacement, and velocity in any steps of loading are calculated. The time of cavitation can be recognized in elastic or plastic regimes by applying the Cowper-Symond constitutive equation. Considering the strain rate influence, the effects of charge mass and standoff are investigated to occur of cavitation and time dependent deflection and velocity of a rectangular plate.

Investigation of the explosive type on the high strain forming of OFHC copper tube

The paper computationally investigates the explosive forming of the oxygen-free high thermal conductivity (OFHC) copper tube subjected to five different explosives. To investigate the effect of explosive type on the formability of OFHC copper tube, commonly used explosives, including C-4, TNT, HMX, Comp-B, and PBXN, was compared by using the finite element method. To verify the developed finite element model (FEM), the explosive forming experiments were carried out by using C-4. In the simulations, Coupled-Eulerian-Lagrangian (CEL) method to model the large deformations, Jones-Wilkins-Lee (JWL) equations of state (EOS) to define the explosive properties and Johnson-Cook (J-C) strength and damage models to specify the metal’s mechanical behavior were utilized. Besides, Hillerborg’s fracture energy was calculated with the Charpy impact test results and given as input to the FEM. The results of FEM were compared and verified using the results of explosive forming tests considering the mesh density and friction coefficient. The simulations revealed that the explosive type affected both the final shape and also the strain rate of the copper tube. When the simulation results for C-4 was taken as reference, HMX and PBX-N increased the strain rate as 110%, roughly. However, Comp-B and TNT reduced the strain rate by nearly 10% and 22%, respectively. Also, the explosive type changed the final hardness of the metal. OFHC Copper had the lowest hardness (112.7 HV) when the simulations were conducted with TNT. In contrast, the highest hardness value (129.5 HV) was reached when HMX was used in the simulations. In addition, simulations put forth that Hillerborg’s fracture energy criteria could be used in the explosive simulations to predict the damage on the metals.

Physically-based modelling for sheet metal cone parts forming under blast loading

Forming sheet metals under blast loading or the explosive forming technique has many advantages for productions, but it is restricted due to its accuracy. This paper introduces a novel theoretical-empirical study for explosive sheet metal forming based on the simple plasticity principles. It provides a method of producing the sheet metal cone parts forming under blast loading, including an analytical model and experimental validation. Firstly, a theoretical-empirical model for cone forming based on underwater explosion employing the impulse method is developed. The model on the whole revealed the relationships among the geometrical parameters of forming a process that is very useful to predict the certain explosive mass for complete forming a cone part. Afterward, a series of experiments are conducted to validate the developed model and also for the required modification in the solution. Comparing the theoretical-empirical solution and experimental results, the ability of the presented model for estimation of the explosive mass is demonstrated. Experimental results show that the theoretical model matched the experiments well.

The Most Sustainable Niche Principles of Social Media Education in A Higher Education Contracting Era

In view of recent higher education contracting because of a declining birth rate and an explosive forming of technology, this research systematically cross-employed a technology acceptance model (TAM) and rational decision-making model (RDM) methodology to discuss from an interdisciplinary perspective the co-relationships between the assessed criteria and evaluated weights of four famous and accredited World University Rankings, the most promising features of massive open online courses (MOOCs), and the sustainable development goals (SDGs) of university social responsibility (USR) principles based on students’, faculties’ and government officers’ interviewee appraised perspectives. Statistically, the weight-questionnaires of random students and professional experts were cross-measured by a factor analysis (FA) of quantitative analysis and an analytical network process (ANP) method of qualitative analysis. As a result, the aggregation technology function (ATF) is the most sustainable niche principle of social media education, not only fulfilling the Making Education More Equitable (MEME), Diminishing Poverty (DP), and Making Gender More Equality (MGME) initiatives of the institution’s USR principles but also increasing the Industry Income (II) of the Times Higher Education (THE) World University Rankings in order to attract, trigger, and drive the students to make a decision to sincerely register in institutions in a higher education contracting era.