This paper deals with the numerical simulation of segmented projectiles. A segmented projectile is a subset of kinetic energy projectiles. The segmented projectile is made of tungsten and the target is semi-infinite and is made of 4340 steels. Due to the disadvantages of segmented projectiles with, the simulation of segmented projectile with is discussed. Projectiles with aspect ratio greater than one are known as short-rod projectiles. This aspect ratio range forms both the primary and secondary phase of penetration. Numerical simulation was performed by AUTODYN software with Smoothed Particle Hydrodynamic (SPH) method. The use of SPH approach is most consistent with the experimental results. In order to have effective segmented projectiles, greater speeds were used in the simulations. In this range of velocity, due to the hydrodynamic penetration and complete erosion of the rods, the maximum penetration depth is obtained. After a relatively good correlation between the simulation results and the experimental and Hydrocode results, the numerical analysis of the segmented projectiles is performed. The results show an increase in the penetration depth of segmented projectile relative to the continuous type. In the following, the relationship between velocity increase and penetration depth and crater diameter of this type of projectile is investigated. An increase in penetration depth of 40 to 60% has been observed in this type of projectile compared to the continuous projectiles. An increase in penetration depth and crater diameter is observed with increasing impact velocity. پرونده مقاله

Parallel Tubular Channel Angular Pressing (PTCAP), as a process of Severe Plastic Deformation (SPD), was employed for improving the strength of commercially pure Titanium (Grade 2). In the present research, the tubular samples of pure titanium were severely deformed by one and two passes of PTCAP at the temperature of 450°C. It was found by the results of tensile tests that the yield and ultimate strengths increased by 24% and 29% after applying the second pass of PTCAP, respectively. It was also showed that the Vickers microhardness increased by 46%. Moreover, the micrographs illustrated that the average grain size decreased from ∼21 μm in the unprocessed condition to ∼143 nm after applying two PTCAP passes. Therefore, applying the technique of PTCAP was successful to produce the nano-structured titanium. پرونده مقاله

Recent advances in technology have increased the necessity of using components with Micro and Nano dimensions. In recent years, the use of bacteria as a renewable tool has hopeful applications in producing different work-pieces. In this study, the effect of Acidithiobacillus Ferrooxidans (A.F) on Vt20 (Titanium alloy) and Cu were investigated. The results illustrated that in the medium of the Aerobic bacteria A.F, the layer of TiO2 on the surface of Vt20 is formed and this oxide layer impedes Vt20 corrosion. Furthermore, it was observed that Cu in a medium of A.F is corroded in the same condition. According to these results, biomachining by A.F is considered as a new approach that is used for Micro-Bio grooving on Cu, but this method has different effects on Vt20. So that due to improving the hardness of Vt20 and high resistance of this alloy against abrasion, this method can be used for coating space traveling equipment, automotive industries and home appliance. On the other hand the effect of pH and temperature on Vt20 were studied and it was observed that the increase in pH and temperature improve the resistance of Vt20 against the surface corrosion. پرونده مقاله

Magnesium alloys are important materials in industries because of their low densities. But the problem with these alloys is their lack of creep resistance at high temperatures. In this research, the creep behavior of cast ZE63 and ZE41 magnesium alloys were studied by using the impression creep method. The tests of impression creep were carried out at a temperature of 473 Kelvin and constant punching stress range of 175MPa to 500MPa. Microstructural investigation of magnesium alloys was performed using an optical microscope and X-ray diffraction (XRD). The results of XRD analysis indicated that the structures of both alloys were composed of α-Mg matrix phase accompanied by Mg7Zn3, Mg12RE, and Mg17RE2 intermetallic compounds. Besides, the analysis of the microstructure of deformation zones showed that the creep resistance of ZE63 was higher than ZE41. The higher creep resistance of ZE63 was attributed to the existence of more continuous phases of Mg7Zn3, Mg12RE, and Mg17RE2. پرونده مقاله

The increase in materials with high mechanical capabilities has increased the number of advanced production methods. One of these methods is the merging of ultrasonic vibrations with conventional machining methods. The milling process is flexible in making different geometric shapes of the workpiece. In this paper, the longitudinal vibrations assisted milling process is studied. The main problem with this process is the transmission of ultrasonic vibrations to the cutting area. Therefore, different transfer methods were studied and analyzed and the most efficient method was presented. Longitudinal vibration equations for the horn were analyzed and different types of horns were designed. The best horn was identified and fabricated in terms of increased vibration amplitude and less stress. It was shown that the 5-element horn is the best option for vibration transmission. In order to transfer electrical energy to the rotary ultrasonic converter, a new tool was designed and manufactured. By machining thin-walled parts, it was shown that the fabricated tool can create appropriate dimensional accuracy in the workpiece. پرونده مقاله

Ionic polymer material composites (IPMCs) are a group of polymeric material which deform by applying voltage and the movement of cations of polymer; it should be mentioned that the finite element method using electromechanics equations can be used to analyze these types of problem and measure the deformation. This phenomenon can causes bending and internal stress. This research, it is tried to investigate the displacement and stress of IPMC by modeling and finite element method analysis. Firstly, a 2D IPMC is designed; then the materials are applied which are cooper for the electrodes and Nafion for the polymeric core. After applying boundary conditions and meshing, the results have been analyzed by the finite element method. It is found that the relation between voltage and its effect on the bending displacement of IPMC is direct. The conclusions include the maximum displacement of IPMC membrane under the voltage of 5V is 0.42 mm and the maximum Von Mises stress on the electrode is gained 3.29×1016 (N/m2). پرونده مقاله