Theoretical And Numerical Study On Generalized Heat Transfer And Thermal Contact Of Gun Barrels Under Transient Launching Load

With higher requirement of weapon striking accuracy and speed in modern warfare,higher energy propellent or higher charge density is needed to meet these operational requirements.However,as the gunpowder energy and packing density increase,the velocity and temperature of the gunpowder gas and the velocity of the projectile also increase dramatically,and the internal ballistic duration become shorter and shorter as well.This is in such a way,the erosion of gun barrel appears to be more and more severer and significantly affects the service life of the weapon systems.Studying the heat transfer inside the gun barrel is a key issue for improving the life of the gun tube and the insight physics of erosion.In this dissertation,the heat transfer within the gun barrel of a large caliber gun during launching process is studied.Under the interior ballistics thermal load,the generalized heat conduction(non-Fourier),generalized thermal contact with perfect/imperfect thermal interface,and thermal response of the gun barrel involving cracks and/or plating layer are carefully investigated.With the objective of providing a general theoretical guideline for the design of the barrel from the perspective of thermal aspect,this thesis mainly focus on the followings:(1)Within the framework of Generalized Single Step Single Solve(GSSSS)time integration,a consistent evaluation technique of time consistency is proposed for the strongly coupled multi-physic problem.With a fusion of finite difference method,the proposed method is utilized to analyze the coupled multiple time dependent systems existing in interior ballistic process,including the coupled subsystems within the interior ballistic process and the coupling between the entire interior ballistic system and heat conduction in the gun barrel.Numerical results indicate that the physics can preserve second-order accuracy only if the coupled system is evaluated via the proposed consistent time level evaluation,otherwise the accuracy will be reduced to first order in time.A preliminary theory is provided for the study of the heat transfer of the gun barrel.The consistent time level evaluation for the coupled system and its application on the interior ballistic model are distributed in Chapter 2 and Chapter 4.(2)The thermal load due to interior ballistic process is conducted at the time scale of millisecond such that it is more reasonable to consider the non-Fourier heat conduction within the gun barrel;meanwhile,an instantaneous thin layer due to non-Fourier effcct has a spatial scale of ≤μm.This is in such a way,the mathematical modeling of the gun barrel is necessary to consider the effect of non-locality and non-Fourier effect.In the present thesis,the corrected moving particle method(CMPS)is first proposed based on the traditional moving particle semi-implicit method(MPS);in the fusion with the generalized heat transfer constitutive law,a thermal Lagrangian is constructed to formulate the generalized dissipate Euler-Lagrangian scale equation,which results in a generalized local and non-local heat conduction theory for solids.Based on this model,the non-Fourier heat transfer with respect to thermal response is investigated in the gun barrel.The numerical simulations indicate that there occurs a significant non-Fourier instantaneous layer near the inner wall of the gun barrel while the dominated thermal physics appears to be more Fourier-type characteristic.Besides,the numerical examples also indicate that the proposed non-local heat conduction model has the ability to capture the thermal response of the system involving cracks;the result shows that there are temperature concentrations at the crack tips.The relevant theory regarding the generalized non-local heat conduction theory and its application on the gun tube can be found in Chapter 3 and 5.(3)Due to the non-Fourier instantaneous thin layer has a very close spatial scale with respect to the thickness of the plating layer attached to the inner wall of the gun barrel,it is more reasonable to describe the thermal conduction in the plating layer via the non-Fourier model.This is in such a way,the fundamental physics of the thermal contact within the plating gun barrel is between the non-Fourier domain and the Fourier domain.In the present thesis,a generalized thermal contact model is formulated in the pattern of differential-algebraic equations(DAE),in which the thermal interface conditions are treated as algebraic equations.The GSSSS-i Integration is extended to solve differential-algebraic systems and ends up with a generalized second-order accurate GSSSS-i DAE Index3 time integration algorithm.The proposed time integration is successfully exploited to achieve the numerical simulation of the complex thermal contact problem within the plating gun barrel as well as the cracked plating gun barrel.The numerical results indicate that the existence of cracks and imperfect thermal interface blocks the propagation of heat energy and leads to a high temperature domain in the chromium-plating layer.The relevant theory regarding GSSSS-i DAE Index 3 time integration and thermal contact in plating gun barrel are given in Chapter 2 and 6.