Design And Optimization For Structure Of TiB₂/Ti FGM Armor

Tanks and other military vehicles require more and more high quality armors in the future,for the advance of anti-armor technology with the transition of the mode of war.The confliction between defense level and defense weight of the military vehicles becomes more and more severe.The widely used layered ceramic/metal armor almost impossible meets the requirements of the possible war in the future for difficult overcoming bottleneck of development.Therefore,new high quality armors are urgently demand.Functional gradient material?FGM?armor is a possible choice for the above problem from the literatures.Because of the design ability of the properties e.g.wave impedance,elastic modulus and thermal expansion coefficient along the gradient direction,continuous or discrete changing from ceramic to metal,FGM armor can greatly inhibit the untimely tensile failure of ceramics that usually occurs in the layered ceramic/metal armor for impacting wave reflecting at the interface.The anti-penetrating performance of FGM thus is greatly improved.However,the basic research on FGM is not systematic and in-depth presently.Meanwhile,proper methods of preparation and design for FGM have not been established.Accordingly,theoretical analysis results guide efficiently structural design and optimization of the FGM armor.As a result,the application of the FGM is restricted severely.For optimizing the structure of TiB₂/Ti FGM armor,numerical simulation based on experimental works was firstly used in this thesis.The main researches and achievements are listed as the following.?1?A new multi-step fabricating way of the Ti B₂/Ti FGM armor material was developed.It is found that the eleven layers TiB₂/Ti FGM could be fabricated by sintering as three sections and then welding in turn for the overlapping sintering temperatures of neighboring layers.Furthermore,the TiB₂/Ti composite with the same composition sintered individual or in the FGM own almost the same structure and mechanical properties for very small residual stress in the interface of FGM,which provides a feasible way to investigate the relationship between the composition and mechanical properties in FGM.?2?A modified H-T model was presented to simulate the relationship between the composition and performance of TiB/Ti composite in FGM.Based on the microstructure evolution and the microstructural failure characters,we found the widely used H-T model could predict not only the modulus but also the strength of TiB/x%Ti composites by a modified condition.Combining the experimental properties of the TiB ceramic,Ti and TiB/Ti composite,a series of material parameters of J-C or J-H model that need in the impact simulation were determined.?3?Based on the propagation dynamics equation of FGM,the influence of gradient characteristics on propagating characteristics of shock wave is studied.The effects of FGM layers characteristics properties and Ti volume fraction on propagating characteristics of stress wave in the interface are studied mainly.Results show that the max tensile stress will overcome the max strength of the TiB/Ti composites,which will cause the untimely tensile failure.For this,Ti concentration gradient difference between neighboring layers in TiB/Ti FGM should not be more than 20%.?4?Based on the above material model and FGM gradient limit between layers,the penetration processes of FGM were simulated and an optimized gradient of FGM was achieved by the conjugate gradient method.Numerical simulations show that the anti-penetration performance of the FGM structure is better than the traditional ceramic/metal composite armor as that observed experimental results.At the same time,distribution law and thickness of the gradient layer have important influence on anti-penetration performance of projectile,which will provide theoretical support for the design and optimization of TiB/Ti FGM armor structure in the future.