Study On Solidification And Cooling Mechanism Of Melt-cast Explosive Under Pressurization

Melt-casting explosive is a type of mixed explosive that is widely used in conventional ammunition such as High-Explosive Anti-Tank and missiles.It occupy an important position in military mixed explosive.In the process of charging,melt-casting explosive is prone to forming shrinkage,shrinkage,bubbles,cracks and other ills inside the explosive,which deteriorates the safety of explosive.The pressure of casting vessel can effectively reduce or eliminate the ills of the melt-casting explosive,and improve the solidification and cooling rate of the explosive.However,the mechanism of these phenomena,especially the mechanism of the increase of solidification and cooling rate of melt-casting explosive by increasing the pressure of the casting vessel,needs to be further revealed.In this paper,the mechanism of the increase of solidification and cooling rate of meltcasting explosive by increasing the pressure of the casting vessel is studied by the onedimensional thermal conductivity experiment,numerical inversion method and computer numerical simulation.The main research contents and achievements are as follows:(1)The measured temperature data under the pressure of 0.1MPa and 0.5MPa was obtained by conducting a one-demensional thermal conductivity experiment with a reasonable temperature measurement device.The experimental result shows the higher the applied pressure,the higher the solidification and cooling rate is.(2)The conjugate gradient method is used to solve the interface heat transfer coefficient(IHTC)between the explosive and the mold.This method transforms the inverse problem of heat conduction into three sub-problems(positive problem,sensitivity problem,concomitant problem)and a gradient equation,thus establishes a numerical inversion model of IHTC between explosive and mold.This numerical inversion model avoids the calculation of a very time-consuming sensitivity matrix and greatly improves the computational efficiency.The result of the solution shows that the change law of IHTC with time is: the value of IHTC reaches the maximum value at the initial moment,with the continuous solidification of explosives,the vlaue of IHTC decreases rapidly;when the explosive is completely solidified,the IHTC remains at a small value;the change law of IHTC with pressure is: the higher the applied pressure,the greater the value of IHTC.(3)The IHTC is confirmed to be resonable by calculating the positive problem of Onedimensional heat conduction.By comparing the numerically calculated temperature field obtained by applying the IHTC under two different pressure 0.1 MPa and 0.5 MPa,the mechanism of the increase of solidification and cooling rate of melt-casting explosive by increasing the pressure of the casting vessel is obtained :the value of IHTC increases as a result of the increases of applied pressure,it leads to the solidification and cooling rate of the melt-casting explosive increases.