Effect of Temperature on the Tensile Strength and Failure Modes of Angle Ply Aramid Fibre (KRP) Tubes Under Hoop Loading

A comprehensive study was undertaken to characterise Kevlar reinforced plastic (KRP) angle ply filament wound tubes at different temperatures. Quasi-static burst tests were performed on tubes of 25°, 55° and 75° winding angle. The tubes were burst under internal radial pressure with minimum end constraints. An experimental rig and two conditioning tanks were designed and built to test the specimens at three temperatures; –46°C (low temperature) and +20°C (room temperature) and +70°C (high temperature). For each test the internal pressure and the strains in both circumferential and longitudinal directions were recorded on suitable digital processing equipment.For a particular batch of tubes tested at three different temperatures, an increase in ultimate hoop strain and a decrease in hoop modulus of the 55° tubes with increasing temperatures was recorded; the temperature effect was less pronounced on the corresponding properties of 25° and 75° tubes. The use of a non-structural thin liner during the tests led to a higher ultimate strength of 55° tubes but had negligible effect on the behaviour of 25° and 75° tubes. The 75° tubes failed in a catastrophic fibre fracture under all test conditions. The mode of failure of 55° changed from weeping at 70°C to fibre fracture at –46°C. The 25° tubes failed by weeping with matrix cracking. The matrix cracking was particularly severe when a liner was used.     

Influence of salt addition and confinement on explosive welding parameters

Experimental data is presented for obtaining a wide range of detonation and flyer plate velocities by salt addition and inertial confinement of the explosive.     

The plastic extension of a chain of rings due to an axial impact load

The plastic response of a chain of circular rings due to an axial tensile impact load was investigated both experimentally and in part, analytically. Chains were built-up from circular aluminium rings and subjected to axial impact loading at one end. High-speed photography was employed to record the development of the deformation process. It was found that plastic collapse was progressively transmitted to neighbouring rings in the manner of a plastic wave. To investigate the situation analytically, a simplified approach was adopted which assumed rigid-perfectly plastic behaviour of the ring material and arrived at an equation of the same form as the classical one-dimensional elastic wave equation.     

Effect of flyer shape on the bonding criteria in impact welding of plates

The paper reports a study of high-speed oblique collision of non-flat metal plates with fixed target blocks. The main aim of the study was to improve the understanding of the industrial process of explosive welding. The results of tests with flat, V- and U-shaped flyer plates were presented. The effect of flyer shape on the area of bonding was examined and three-dimensional numerical modeling was used to identify and relate mechanical parameters, such as plastic strain and shear stress to the quality of welding.Effective plastic strain (PEEQ) and shear stress in the flyer plate were shown to be criteria in determining weld quality.The study has shown that the shape and amplitude of the waves in the interface between flyer plate and target block are dependent on the shape of the flyer plate. Both the numerical modelling and the experimental tests showed that the largest area of weld was produced with flat flyer plates.     

Explosive welding of flat plates in free flight

The explosive welding of two or more plates in one shot, in free flight, is examined both experimentally and theoretically. A simple analysis based on equating the kinetic energy lost in the collision process to the plastic work dissipated in progressive indentations is presented. The predicted wavelength of the resulting interfacial waves is in reasonable agreement with the measured values.     

Penetration by high speed oblique jets: Theory and experiment

The process of deep oblique penetration of solids by impulsively generated short jets is investigated both theoretically and experimentally. Penetrations are characterised by the formation of craters much wider than the jets.

Water jets were generated by explosive impact and caused to impinge on Plasticine targets at different angles. The velocity of such jets was found to decay behind the jet tip in a manner similar to that frequently observed in shaped charge jets. A simplified theoretical treatment based on a theory of quasi-static expansion of cylindrical cavities is presented. Jet lengthening is considered when the shape of the resulting crater is predicted.

Despite the simplifying assumptions made, the predictions of the theory are found to be in reasonable agreement with the experimental results.     

Production of COx-free hydrogen by the thermal decomposition of methane over activated carbon: Catalyst deactivation

Hydrogen, an environment-friendly energy source, is deemed to become strongly in demand over the next decades. In this work, CO_x-free hydrogen was produced by the thermal catalytic decomposition (TCD) of methane by a carbon catalyst. Deactivated catalysts at four-stage of progressive were characterized by nitrogen sorption and scanning electron microscopy. TCD of methane at 820 and 940 °C was about 13- and 8-folds higher than non-catalytic decomposition, respectively. High temperatures positively affected the kinetics of hydrogen production but negatively influenced the total amount of hydrogen and carbon products. The total pore volume was a good indicator of the total amount of hydrogen product. Catalyst activity was decreased because of the changes in the catalyst's textural properties within three ranges of relative time, that is, 0 to 45, 0.45 to 0.65, and 0.65 to 1. Models for specific surface area and total pore volume as functions of catalyst deactivation kinetics were developed.     

The compaction of powder metallurgy bars using high voltage electrical discharges

A new compaction process for the production of high density powder metallurgy (P/M) bars is suggested using a high voltage electrical discharge followed by rotary swaging. This paper gives practical details concerning the production of P/M bars from iron powder by electrical discharge, and endeavours to describe the mechanism of density increase. Experimental results for determining the effect of various parameters are presented.     

Large deflexion elastic-plastic response of certain structures to impulsive load Numerical solutions and experimental results

A theoretical and experimental study of the elastic-plastic response of certain structures to impact and impulsive load is described. Lead rings were allowed to fall freely on to a flat and pointed sharp anvil, aluminium rings were subjected to the impact of a free falling sharp indenter and thin aluminium cantilevers, rectangular and triangular frames and semicircular arches were subjected to magnetomotive and explosive impulse.

A numerical solution based on a finite difference approximation was developed to describe the response of an equivalent lumped parameter model for each of the above structures. This method, although restricted to two-dimensional structures, can be applied to a variety of structural elements.

High-speed photographs were taken for each of the loading events and the experimental data obtained were compared with the theoretical plastic response predicted by the numerical method.