The linear shaped charge is a type of shaped charge. After the linear forming charge is detonated, the metal cover forms a high-speed flat metal jet cutting knife under the action of the detonation product to realize the cutting of the target, so it is also called a shaped energy cutter. The directional cutting ability of linear shaped charge is widely used in engineering blasting, for example: cutting steel plates and steel beams in the field; cutting components under water, such as cutting hulls when salvaging shipwrecks. In this paper, a semi-square hood-type cutter different from the above-mentioned linear cutter structure is designed, and the linear cutter has a semi-square cross section. The LSDYNA software was used to simulate the jet forming process of the semi-square hood line cutter. The influence of the forming process and the thickness of the hood on the jet forming was analyzed. 1 Half-square hood line cutter structure and geometric model 11 Semi-square medicinal hood structure Semi-square hood linear cutter structure scheme diagram as shown, its main structural parameters are seven, that is, the hood length, width a high B-type cover thickness d charge length L width A high B semi-square shape cover can also be seen as two wedge angle 90 wedge-shaped hoods arranged together to evolve into a linear shaped charge structure. When the explosive is detonated from the midpoint of the top edge of the charge, two spherical detonation waves are formed. The detonation wave propagates in the direction of the cross section and propagates in the direction of the rib. In the cross-sectional direction, the detonation causes the upper top surface of the semi-square blister to gradually press from the ends to the middle, while the two sides gradually press from the top to the bottom, causing the hood to be on the two diagonal planes. Two 1-piece initial jets are formed separately. When the two initial jets reach the center plane of the liner, the two initial jets begin to converge secondary along the center plane of the liner, and in the direction of the edges, the liner is gradually compressed from the center to the ends. As a result, a sheet-shaped fan shaped shaped energy cutting knife was formed. According to the structural diagram of the line cutter, a geometric model of the linear cutter structure as shown and a geometric model of the overall structure shown are established. The structural parameters used in this paper are: medicinal mask length 1500 width a=500mm high b=250 pan, drug cover thickness d=20mm charge length L=1500mm width A=1300mm high B=67.5mm considering engineering application Conveniently, the structure is detonated by the center point of the top edge of the charge. 2 Numerical simulation 21 calculation model Engineering research on shaped charge is carried out by a combination of theoretical analysis, numerical simulation and experimental research. For the semi-square linear cutter described above, since the molding mechanism is still unclear, research by numerical simulation method can reduce cost and save design time. Therefore, the LSDYNA three-dimensional dynamics simulation software was used to simulate the process of forming a jet by a semi-square linear cutter. The TugSd pre-processing software was used for meshing to create a finite element model of the semi-square hood-type cutter as shown. Since the structure is a plane symmetrical structure, the finite element model uses a 1/4 structure to divide the grid to reduce the number of model units and reduce the calculation time. In order to simplify the calculation, the influence of the shell is not considered in the model, only the liner, explosive and air are considered. The multi-material flow Euler algorithm is used to simulate the formation process of the semi-square copper coating jet. The grid unit uses the Sl64 eight-node hexahedral element, and the finite element model includes 648,720 nodes and 624,416 units. The hood is made of MATOHNSNCDOK material model and GRUNEISEN-like BURN material model, WL equation of state, air material using MATNUL material model and HSLNEARPOLYNCMI AL dog equation. See the value of the formula cover, explosive, and air material. The unit system used is: mmms-kgGPa finite element model 22 Numerical simulation results and analysis The semi-square shaped hood forms a jet process as shown. It can be seen from the calculation results that the drug cover starts to be compressed, the initial jet is formed, the initial jet secondary convergence and the converging jet are elongated, and finally the jet shape when the collapse is broken. It can be seen that the jet forming process of the semi-square linear cutter under the action of explosive load can be divided into explosive detonation, the blister is gradually compressed along two diagonal planes to form an initial jet, and the initial jet is along the central plane. Several stages are carried out, such as secondary convergence, convergence of the jet after the convergence, and finally breaking. From the velocity profile (a) at the center profile and the overall jet velocity map (b), it is known that the t=6S inch detonation wave reaches the hood and begins to compress the hood. When tz=i4s, the top surface and the two sides of the top cover are pressed in the direction of the two diagonal planes, and the initial jet begins to form. The 18 S-inch two initial jets are converged along the central plane, and the linear shaped jet begins to form. The t=24S inch converging jet is elongated and the sheet-shaped fan-shaped cutting blade is formed. 38 pairs of jets began to break. Due to the surface symmetry feature of the linear shaped energy structure, two spherical detonation waves act simultaneously on the medicinal mask under the initiation condition of the center point of the two edges of the charge. Since the detonation wave first reaches the symmetry center of the drug hood, an initial jet is first formed on the symmetrical center section of the medicated hood, and the second converge is first performed, and then the fan-shaped dicing blade is gradually developed toward both ends. Through the above analysis, it can be known that under the structural parameters of the present invention, the semi-square hood-type cutter can form a linear shaped energy jet, and the linear jet process is different from the ordinary wedge-shaped cover and the circular-shaped linear cutter. Yes, there is a process in which the initial process of the initial jet is concentrated. At the same time, the simulation results also show that the thickness of the liner has a great influence on the velocity of the initial jet and the secondary convergence to form the jet, as shown in Table 1. Table 1 Different wall thickness of the paint cover to form the velocity of the jet wall thickness d / mm initial jet velocity v "m.s1 converging jet velocity v (m.si can be known from Table 1, the formation of initial jet and secondary convergence to form a linear poly The speed of the jet can be reduced with the increase of the wall thickness of the liner. The jet velocity formed by the secondary convergence is increased by more than 33% compared with the velocity of the primary converging jet. At the same time, the speed of the fan-shaped sheet is formed as compared with the ordinary line cutter (the speed is improved significantly compared to about 500 m/S121). 3 Conclusions Numerical simulation results show that the semi-square hood line cutter can form a linear shaped energy jet cutter as expected. The semi-square hood-line cutter forms a jet process that differs from the conventional wedge-type and round-type linear cutters in forming a jet process in that there is a process of secondary condensation of the initial jet. The jet velocity through the secondary convergence is significantly improved, and the jet velocity formed by the secondary convergence is increased by more than 33% compared with the velocity of the primary converging jet. Moreover, the semi-square hood type cutters have a jet velocity that is significantly higher than that of a conventional wire cutter. The thickness of the drug cover has a great influence on the secondary converging jet velocity. As the thickness of the drug cover is increased, the jet velocity of the linear cutter is reduced. Due to the limitations of the conditions, this article does not carry out numerical simulation of the charging characteristics, detonation mode, presence or absence of the shell, etc., and does not test to verify, these need to be further research in the future. T Bolt Black Hebei Qianmu Fastener Manufacturing Co., Ltd , https://www.qmjgjfasteners.com