V. Madhu

An experimental study of normal and oblique impact of hard-core projectile on single and layered plates

An experimental study of the normal and oblique impact of armour-piercing projectiles on single and layered plates of mild steel, RHA steel and aluminium is presented. The projectiles were fired at an impact velocity of ∼800–880 m s−1. The plate thickness varied in the range 4.7–40 mm and the ratio of the plate thickness to the diameter of the projectile varied in the range 0.75 – 6.5 for single plates and up to 13 for layered plates. Observations on target damage and measurements of incident and residual velocities and the angles in normal and oblique impact are presented. Determination of plate thickness t∗, for which the incident velocity is the ballistic limit, is considered and influences of various parameters, like plate material and its thickness, on t∗ and the residual velocity are discussed. Relations are developed to determine the residual velocity for a plate of thickness less than t∗, and to relate t∗ with the hardness of the material. Results for the residual velocity obtained from these relations are compared with those from the experiments.

Normal and oblique impact of a kinetic energy projectile on mild steel plates

Summary A series of experiments was carried out wherein spinning armour piercing projectiles of core diameter 6.2 mm were fired on mild steel plates of thicknesses varying from 10 to 25 mm. The projectile velocity in all the tests was about 820 ms−1 in both normal and oblique impacts. In successive tests on plates of each thickness, the angle of obliquity was increased from 0° (normal impact) until richochet occurred. The impact velocities in all tests and the residual velocities in tests wherein the plates were perforated, were measured. Velocity drop versus angle of obliquity curves are presented for plates of different thicknesses. The target damage is examined and the conditions at ballistic limit and ricochet are discussed.

Effect of Wire-EDM Machining Parameters on Surface Roughness and Material Removal Rate of High Strength Armor Steel

This work presents the influence of machining parameters on surface roughness (SR) and material removal rate (MRR) of high strength armor steel using wire cut electrical discharge machining (WEDM). Tests have been carried out with six process parameters: pulse-on time, pulse-off time, wire feed, flushing pressure, spark voltage, and wire tension. Taguchis technique has been employed for experimental investigation. Results show that pulse-on time, pulse-off time, and spark voltage are significant variables to MRR and surface roughness (SR). The confirmation experiments have also been conducted to validate the results obtained by the Taguchi technique.

Dynamic recrystallization behavior of a biomedical Ti-13Nb-13Zr alloy.

The dynamic recrystallization (DRX) behavior of a biomedical titanium Ti-13Nb-13Zr alloy has been investigated using the high temperature compression tests under wide range of strain rates (0.001-1/s) and temperatures 900-1050°C. A constitutive equation represented as a function of temperature, strain rate and true strain is developed and the hot deformation apparent activation energy is calculated about 534kJ/mol. By considering the exponential relationship between work-hardening rate (θ) and stress, a new mathematical model was proposed for predicting flow stress up to the critical strain during hot deformation. The mathematical model for predicting flow stress up to the critical strain exhibits better consistency and accuracy. The DRX kinetic equation of Ti-13Nb-13Zr alloy is described as XDRX=1-exp[-0.32(Ɛ-ƐcƐ(*))(2.3)] . The DRX kinetic model was validated by microstructure observation. It was also found that the process of DRX was promoted by decreasing strain rate and increasing deformation temperature. Eventually, the continuous dynamic recrystallization (CDRX) was identified to be the DRX mechanism using transmission electron microscope (TEM).