A note on the cavitation phenomenon in metallic plates perforated by sharp-nosed rigid projectiles

We explore the perforation process of metallic plates impacted by rigid sharp-nosed projectiles at high velocities. In particular, we are looking at the diameters of the penetration hole in the plates through a series of 2D numerical simulations, in order to check for the occurrence of cavitation in finite-thickness plates. This phenomenon has not been observed by previous workers and we were looking for its effect on the perforation process. Our simulations show that for every projectile/plate pair there is a certain impact velocity which marks the onset of cavitation. These threshold velocities depend on the normalized thickness of the plates, as well as on their effective strength. Our simulations are supported by the results from perforation tests on plates made of a low strength lead-antimony alloy. The main conclusion from our work is that analytical models for plate perforation should take into account the cavitation phenomenon, especially for high velocity impacts.

Experimental and numerical investigation of Armox 500T armor steel perforation process

This paper presents the results of an experimental and numerical study of the perforation of Armox 500T armoured steel. The plate perforation was performed with a pneumatic gun using three types of penetrators. Sharp, spherical and blunt penetrators were used. The use of different geometries of penetrators causes the process of perforation and destruction of plates in a different state of stress and strain, which leads to the appearance of three basic modes of failure. Numerical analyses of the perforation process have been carried out using the Ls-Dyna computational code with an advanced constitutive model of the material and the integrated failure model. The obtained experimental and numerical results were analysed and compared. The failure shape, the level of plastic deformation and the parameters of stress and strain state were analysed.

Experimental analysis of the state of stress in a steel – titanium perforated plate loaded with concentrated force

The paper presents an experimental analysis of the state of stress, free supported on the edge of a steel – titanium circular perforated plate loaded with a centrally concentrated force, created in the technological process of explosion welding. For this purpose, a special test stand was designed and a methodology for testing the perforated plate was developed. Resistance strain gauges were used to measure the state of strain. The load was applied in the center of the plate to a pressure stamp. As a result of the research, the values of radial, circumferential and equivalent von Mises stress were obtained as a function of the radius of the plate perforation circle and its load. The stress distribution topography revealed the zones of maximum stress of the steel – titanium perforated plate. The proposed method of experimental research can be used by engineers to verify the state of stress, e.g. in the designed tube sheet walls of reactors for ammonia synthesis.

A Predictive Non-Dimensional Scaling Law for the Plate Perforation of Several Aluminum Alloys by Fragment-Simulating Projectiles

An equation was previously-presented to predict the ballistic-limit velocity for the perforation of aluminum armor plates by fragment-simulating projectiles (FSP). The ballistic-limit equation was presented in terms of dimensionless parameters so that the geometric and material problem scales are identified. Previously published predictions and data for two different FSP projectile calibers (12.7 mm and 20 mm) and two different strength aluminum alloys show the scaling law to be accurate. In this paper we extend the same concept to several other alloys and show that this scaling law is predictive.

Sound insulation analysis of micro-perforated panel coupled with honeycomb panel considering air cavity for offshore plants

The wall panels used in offshore plants require sound insulation performance as well as fireproofing. A honeycomb panel made of metal is incombustible but unsatisfactory at the middle frequencies for sound transmission loss because the coincidence frequency occurs when the bending wavelength on the panel matches the wavelength of the incident wave. In this study, the application of a micro-perforated plate to the honeycomb panel was considered to supplement the sound transmission loss at the middle frequencies. The honeycomb core was assumed to overlap an orthotropic layer with an air layer, and face sheets were assumed to be isotropic. The kinetic and potential energy for the face sheets and the honeycomb core, the kinetic energy for the air layer located between the face sheets, and the sound absorption coefficient for the panel were derived. These were substituted into the Lagrange equation, and by solving the equation, the sound transmission loss was obtained. By comparing the experimental results with theoretically predicted results, it was found that the theory well reflected the measured surface density, elasticity, and absorption coefficient. Finally, simulations were performed for the micro-perforated plate perforation presence, micro-perforated plate perforation diameter, cell wall thickness, and cell size. These were analyzed with regard to the surface density, elasticity, and absorption coefficient.