Study On Forming Mechanism Of Circumferential Annular LEFP

Linear explosively formed penetrators are widely used in the field of air defense and antimissile defense due to their efficient damage ability and interception characteristics that intersect with incoming projectiles in a linear fashion.However,a single linear explosively formed penetrator can only intercept incoming targets in a single direction.In order to study a new type of LEFP air defense and antimissile warhead that can effectively respond to multidirectional incoming targets,a circumferential annular LEFP warhead was designed based on the characteristics of linear explosively formed penetrators.After the charge is detonated,it can generate an entire annular LEFP along the circumferential direction of the warhead,providing efficient damage performance while intercepting and striking targets from any direction within the flight plane of the LEFP,greatly improving the interception efficiency.The research in this paper has important guiding significance for the design of a new type of air defense and antimissile warhead.In order to achieve the goal of achieving the farthest flight distance,excellent fragment shape,and fastest flight speed for a circumferential annular LEFP,theoretical analysis and numerical simulation are used in this paper to study the three types of factors that affect the performance of the warhead,namely,the number of detonation points,the structural parameters of the liner and the parameters of the semi preformed groove.The main research contents of this article include:(1)Study on the forming process of circumferential annular LEFP.The material parameters used in the numerical calculation have been verified through existing experimental results,ensuring that the simulation results are consistent with the experiments.The circumferential annular LEFP warhead with a rotational diameter of 500 mm,a diameter of 60 mm,a height of 50 mm,and a uniform wall thickness spherical shaped cover has a maximum flight distance of 290 mm and a stable flight speed of 1200 m/s.However,the fragments produced after complete rupture have different qualities,irregular shapes,and poor performance.(2)Study on the influencing factors of circumferential annular LEFP molding.Firstly,the performance changes of the circumferential annular LEFP with different number of initiation points were studied,and the variation rules of the surface pressure of the liner with different number of initiation points were obtained.The molding process of the circumferential annular LEFP warhead was analyzed,and the optimal initiation spacing of the circumferential annular LEFP with a 500 mm charge rotation diameter was determined to be 34.89mm;Then,the influence of the structural parameters of the liner on the performance of the circumferential annular LEFP warhead was investigated,and the variation rules of the performance of the circumferential annular LEFP with different wall thicknesses and radius of curvature were obtained.When the liner wall thickness was between 5.5 mm and 6 mm,and the radius of curvature was 34 mm,the circumferential annular LEFP could maintain its complete shape and fly for a relatively long distance,but its broken fragment morphology was still not ideal.(3)Study on the influence of semi preformed grooves on the molding of circumferential annular LEFP.The natural state of the next week’s annular LEFP warhead is still unable to achieve the goal of excellent fragment morphology after complete rupture.Therefore,the fragment shape is controlled by adding a semi prefabricated groove on the surface of a spherical shaped charge liner with a wall thickness of 4.5 mm and a radius of curvature of 30 mm.Compared to the external groove,the fracture pattern of the circumferential annular LEFP with the internal groove is more regular,which makes the fragment shape generated under the internal groove superior to the external groove.When the number of grooves is small,the projectile will also break in the non-grooved area.Through research on the impact of the number of grooves,it is finally determined that the requirement for forming a good fragment shape can be met when the number of grooves is 24.Finally,in order to minimize the impact of semi preformed grooves on the farthest flight distance of a circumferential annular LEFP warhead,the effects of groove depth and angle on the shaping characteristics of the warhead were studied for V-shaped grooves.Finally,it is concluded that when the groove depth is 22.2%of the wall thickness of the liner and the groove angle is 30 °,the circumferential annular LEFP can form well shaped fragments while ensuring a descent rate of only 6.9% for the longest flight distance.