Comparison of Numerical Simulation Techniques of Ballistic Ceramics under Projectile Impact Conditions

This article presents an analysis of the effectiveness of available numerical techniques in mapping the characteristic behavior of ballistic ceramics under projectile impact conditions. As part of the work, the ballistic tests were performed on the layered ceramic/steel composite armor and tested with the 7.62 × 39 mm, armor-piercing incendiary (API) BZ projectile. The experimental tests were then mapped using computer simulations. In numerical analyses, four different techniques were used to describe cubic ceramic tiles Al2O3 placed on the ARMOX 500T steel backing plate, i.e.,: the Finite Element Method without Erosion (FEM), Finite Element with erosion (FEM + Erosion), Smoothed Particles Hydrodynamics (SPH) and a hybrid method that converts finite elements to SPH particles after exceeding the defined failure criteria (FEM to SPH conversion). The effectiveness of the individual methods was compared in terms of quality (mapping of characteristic phenomena occurring during the penetration process), quantity (bulge height of the backing plate) and time needed to complete the calculations. On the basis of the results of the experiments and numerical simulations, it was noticed that the most accurate reproduction of the phenomenon of ballistic impact of AP projectiles on ceramic/steel composite armor can be obtained by using a hybrid method, incorporating the conversion of finite elements into SPH particles. This method should be used in cases where accuracy of the results is more important than the time required to complete the calculations. In other situations where the purpose of the calculation is not to determine, for example, the exact value of penetration depth but only to observe a certain trend, the FEM method with defined erosion criteria (variant 2), which is more than 10 times faster, can be successfully used.

Investigation of Advanced Robotized Polymer Sheet Incremental Forming Process

The aim of this work is to evaluate the possibility of inexpensively producing small-batch polymer sheet components using robotized single point incremental forming (SPIF) without backing plate support. An innovative method of thermal and ultrasound assisted deformation of a polymer sheet is proposed using a tool with a sphere mounted in a ring-shaped magnetic holder, the friction of which with the tool holder is reduced by ultrasound, and the heating is performed by a laser. The heated tool moving on the sheet surface locally increases the plasticity of the polyvinyl chloride (PVC) polymer in the contact zone with less deforming force does not reducing the stiffness of the polymer around the tool contact area and eliminating the need for a backing plate. The free 3D rotating ball also changes the slip of the tool on the surface of the polymer sheet by the rolling, thereby improving the surface quality of the product. The finite element method (FEM) allowed the virtual evaluation of the deformation parameters of the SPIF. Significant process parameters were found, and the behavior of the heated polymer sheet was determined.

NUMERICAL AND EXPERIMENTAL STUDY OF CERAMIC/STEEL COMPOSITE FOR STRUCTURAL APPLICATIONS

The Terminal ballistics is the study of science that deals with the interaction involved in two impacting bodies. This research focused on the high-impact resistance of layered composite comprising of alumina ceramic and armour steel. The composite was designed to have ceramic as the facial plate with armour steel as its backing plate. For the numerical study, the ceramic thickness was varied (6, 8, 10, 12 mm) while keeping the thickness of backing steel constant (7 mm). The projectile, 7.62 mm armour-piercing (AP), was set with a velocity of 838 m/s and made to impact the different ceramic–steel composite target configurations at zero obliquity. The study captured fracture processes of the ceramic, the deformation of projectile, and backing steel. An effective optimum thickness ratio of 1.4 (ceramic:steel; 10/7) for the ceramic/steel components with less deformation of the backing steel is found. Thereafter, the result of the numerical study was validated by experimental ballistic investigation of the determined optimum ceramic/steel ratio. The experiment corroborated the simulation results as the alumina ceramic provided efficient protection to armour steel component after a severe interaction with the impacting projectile.

Effect of backing plate on mechanical and microstructural properties of tungsten inert gas welded AA 6063 butt joints

In the present scenario, ship building industries are frequently associated with welding process to explore the benefits of improved strength over the parent material. Development of new techniques to enhance the processes is of a part of the usual practice in industries. In the present work, as a supportive measure, backing plate was introduced to develop the weldments with enhanced properties. The central composite design array specimens, a widely used aluminum alloy in marine application AA 6063 were prepared by TIG welding process with the help of backing plates of different materials. Effect of backing plate material on the properties such as ultimate tensile strength and microhardness of the weld joints were investigated. A detailed study of microstructure and macrostructure on the weldment was also done. Results exhibit a considerable improvement for the recommendation of using copper backing plates in the welding processes.

Development and tribological characterization of fly ash reinforced iron based functionally gradient friction materials

The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Therefore, the need of the hour is to develop friction materials with functional gradients that have high wear resistance (contact area) and high bond strength (interface). In this study, an attempt is made to fabricate and characterize a friction material with gradient profile of composition along the cross section to provide functional gradient property. The functional gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders which is then compacted and sintered. The prepared functional gradient friction material was characterized in terms of microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads using pin-on disc apparatus. The results show that as the load increases, the wear rate decreases and at the same time the COF tends to increase at higher loads. The predominant wear mechanism was deduced from the morphology of the worn surface.

Ballistic Performance of Sandwich Composite Armor System

This study focused on the design, modelling and the analysis of the dynamic response of composite armor system, constructed with Kevlar 29 as front skin, Alumina-ceramic filled in x shaped corrugated structure as core and bottom skin Kevlar 29 and T800S, in terms of residual velocity, energy absorption capacity and limiting velocity. The core cell size, height, thickness, skin thickness, etc., will be varied to get their influence on the impact resistance. The design parameter will be investigated for the sandwich composite armor with various configurations and stacking sequence of Alumina Ceramics, Kevlar 29 and T800S. The sandwich typically consists of front plate, core and backing plate, which will be impacted at different velocities starting at 100m/s till significant armor penetration. The ballistic limit velocity (V50) will be determined from the analysis. The non-linear explicit dynamic analysis and simulation results computed using the software ABAQUS will be validated by experiment. From the data obtained it can be suggested which composite armor has improved impact resistance and performance.