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A new linear yield criterion, referred to as geometrical approximation (GA) yield criterion, is proposed in this paper. On the π-plane in Haigh Westergaard stress space, its locus is an equilateral and non-equiangular dodecagon which has the largest approximation to the Mises locus in geometry. Also, its specific plastic work is deduced and applied to the limit analysis of circular plate under uniformly distributed load. Classical yield experimental data are adopted to validate the proposed criterion. It shows that the GA yield criterion can well fit the classical experimental data for different ductile metals. Application of the deduced specific plastic work to the limit analysis of a circular plate shows that the GA-based analytical results are higher than the Tresca results and closely match the Mises numerical results. [ABSTRACT FROM AUTHOR]

Tubular channel angular pressing (TCAP) is a new and novel severe plastic deformation (SPD) technique suitable for fabrication of bulk nanograined tubular materials. There are several parameters in the TCAP process. The present paper investigates the effects of curvature angles, deformation ratio (maximum radius during TCAP/initial radius) and deformation direction on the plastic deformation behavior, strain homogeneity and required loads in TCAP processing. The results showed that higher curvature angles ( ψ and ψ) leads to better strain homogeneity while have not having any significant effect on the process loads. Also, at the second curvature angle of 90°, the best condition is achieved with good strain homogeneity and lower load requirements rather than lower angles. Investigation of deformation direction showed that inlet deformation direction causes tube thinning at the end of the process, and thus, using the inlet case is not recommended. [ABSTRACT FROM AUTHOR]

In the past years, contact between two bodies has been studied from various ways that do not consider the cut-off frequency effect on the contact mechanism. This paper reports the correlation between rough point contact and flat surface contact at different cut-off frequencies of filter. The similarity and difference between the two types of contact mechanisms are presented for materials with linear or elasticperfectly plastic deformation. The conjugate gradient method (CGM) is used for analysing the rough point contact, while the rough flat surface contact is studied with an improved CGM in which the influence coefficient for the elastic deformation of the rough flat surface is obtained with finite element method. Numerical results show that for the above two types of contacts, their von Mises stress and maximum shear stress are greatly affected by the cut-off frequency of a high-pass filter. Moreover, a decrease in the cut-off frequency leads to an increase in the contact area and a decrease in the approach for the rough flat surface contact, while the opposite variations is for the point contact between rough bodies with the small radii. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the influence of rotation, initial stress and gravity field on the propagation of Rayleigh waves in a homogeneous orthotropic elastic medium. The government equations and Lame's potentials are used to obtain the frequency equation which determines the velocity of Rayleigh waves, including rotation, initial stress and gravity field, in a homogeneous, orthotropic elastic medium has been investigated. The numerical results analyzing the frequency equation are discussed and presented graphically. It is important to note that the Rayleigh wave velocity in an orthotropic elastic medium increases a considerable amount in comparison to the Rayleigh wave velocity in an isotropic material. The results indicate that the effects of rotation, initial stress and gravity field on Rayleigh wave velocity are very pronounced. [ABSTRACT FROM AUTHOR]