The effect of minor additions substitutional elements such as Al, Cu, Mn, and Fe on the room-temperature (RT) elevated-temperature hardness a single bcc phase Hf20Nb31Ta31Ti18 refractory high entropy alloy is studied here. Interestingly, 2.5 at. % nominal addition hardened base in temperature range from RT to 800 °C, while same content Mn softened 1000 °C. Regardless solid solution hardening or...

A plasticity-fracture constitutive model is presented for prediction of the behavior of confined plain concrete. A three-parameter yield surface is used to define the elastic limit. Volumetric plastic strain is defined as hardening parameter, which together with a nonlinear plastic potential forms a non-associated flow rule. The use of non-associated flow rule improves the prediction of the dil...

In this study, isothermal compression tests of TB18 titanium alloy were conducted using a Gleeble 3800 thermomechanical simulator for temperatures ranging from 650 to 880 °C and strain rates 0.001 10 s−1, with constant height reduction 60%, investigate the dynamic softening mechanisms hot workability alloy. The results showed that flow stress significantly decreased an increasing deformation te...

In this paper, a simple sub-loading yield surface model for both normally consolidated and over-consolidated clay is proposed with emphasis on the effect of shape. Compared modified Cam-clay model, only one additional material parameter introduced to reflect geometry features surface. A higher-order stress–dilatancy relation given in current study, leading new function capable offering an adequ...

Fifteen ROSAT PSPC observations available in the public archive are analyzed in order to study time and spectral variability of the 12 EMSS AGN detected by ROSAT with more than 2000 net counts. Time variability was investigated on 13 different time scales, ranging from 400 s to 3.15×10 6 s (1 year). Of the 12 sources analyzed, only two do not show a significant variability on any time scale. On...

We present the results of observations of the soft gamma-ray early afterglows with the energy above 100 keV from two bright Gamma-ray bursts detected by the PHEBUS instrument of the GRANAT orbital observatory. We show that the light curves of GRB 910402 and GRB 920723 events present the afterglow emission with fading fluxes. During our observations (∼ 700 s) for these gamma-ray bursts the after...

THIS PAPER is concerned with an analysis of strain localization in ductile crystals deforming by single slip. The plastic flow is modelled as rate-insensitive, and localization, viewed as a bifurcation from a homogeneous deformation mode to one which is concentrated in a narrow ‘shear band’, is found to be. possible only when the plastic hardening modulus for the slip system has fallen to a cer...

We study the plane strain thermomeehanical deformations of a viscoplastie body containing a rigid non-heat-conducting ellipsoidal inclusion a t the center. Two different problems, one in which the major axis of the inclusion is parallel to the axis of compression and the other in which it is perpendicular to the loading axis are considered. In each case the deformations are presumed to be symme...