In this study, polycarbonate (PC) and polystyrene (PS) are subjected to plastic deformation by means of cold rolling and the resulting variation of the free volume and its subsequent time evolution after rolling is investigated by means of positron annihilation lifetime spectroscopy (PALS). The value of the long lifetime component that is attributed to the decay of ortho-positronium (tau(o-Ps))...

The finite-element method is used to perform an accurate numerical study of the normal indentation of an elastic-plastic half-space by a rigid sphere. The effects of elasticity and strain-hardening rate of the half-space are explored, and the role of friction is assessed by analysing the limiting cases of frictionless contact and sticking friction. Indentation maps are constructed with axes of ...

Background: Nickel-based superalloys are usually exposed to high static or cyclic loads in non-ambient environment, so a reliable prediction of their mechanical properties, especially plastic deformation, at elevated temperature is essential for improved damage-tolerance assessment of components. Methods: In this paper, plastic deformation in a single-crystal nickel-based superalloy CMSX4 at el...

This paper deals with two-dimensional plane stress wrinkling model of a plastic annular plate. Based on energy method and the nonlinearity of strain-displacement law, a bifurcation function in polar coordinates is derived analytically. This technique leads to the critical conditions for the onset of the plastic wrinkling of flange during the deep drawing process. To find this solution, the Tres...

Since tubes are widely used for different industrial applications, processing of tubes by the Severe Plastic Deformation (SPD) method has been the target of different attempts. Among these attempts, development of SPD processes for tubes based on Equal Channel Angular Pressing (ECAP) has been more successful. As an illustration, Tube Channel Pressing (TCP) has been presented as an attractive SP...

The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectivel...

Background & Aim:  The hot water extract of a mixture of Anogeissus leiocarpus and Prosopis africana is widely used in the northern part of Nigeria for the treatment and management of asthma. Since investigations of its pharmacological activities already justify its use, and the need for standardization of herbal medicine and develop appropriate dosage forms has continued to g...

Two series of experiments are performed to investigate the dynamic response of various essential components of a class of sandwich structures, under high-rate inertial loads. One consists of dynamic inertia tests and the other involves dynamic impact tests. A split Hopkinson bar apparatus is modified and used for these experiments. First, the energy-absorbing characteristics of the plate materi...