Features of delayed fracture of martensitic steels during hydrogenation depending on size of initial austenite grains

The effect of the size of the initial austenite grains on the local characteristics of delayed fracture of martensitic steel with high and low levels of residual internal microstresses under hydrogenation conditions has been studied. The contribution of hydrogen and residual internal microstresses to the decrease in local strength of the boundaries of the original austenite grains during hydrogenation during the incubation period is divided.

A new strain-gradient theory for an isotropic plastically deformed polycrystalline solid body

This study considers strain-gradient plasticity theory in the context of small deformations for an isotropic solid body with a view to investigating the distortion effects associated with the divergence of plastic strain through the Burgers tensor. The principle of virtual power is employed and the constraint of irrotationality is imposed on the plastic component of the gradient of the displacement vector. It is obtained that the gradient, curl, and divergence of the plastic strain in the body are mutually related. This relation establishes the existence of work done through the divergence of plastic strain as distinct from the work done through the gradient of the plastic strain. Consequently, a polycrystalline solid body undergoing distortion associated with the divergence of plastic strain exhibits new internal microstresses; and the obtained model, consisting of the microforce balance, constitutive relations, and plastic flow rule, extends the known Gurtin–Anand model in a natural fashion. Furthermore, in the governing flow rule, it is revealed that the internal microstresses associated with the divergence of plastic strain act as opposing agents to the internal microstresses associated with the gradient of the plastic strain via the length scales Q, L, and the gradient of the divergence of the plastic strain. This work shows the distortion effects associated with the divergence of plastic strain which the Gurtin–Anand strain-gradient plasticity theory in literature does not apprehend.

Studying Temperature Effects on Internal Microstresses in Indexable Inserts Made of (Ti,W)C-Co Group Hard Alloys

The article is dedicated to investigating the problem of increasing the efficiency of modular cutting tools with indexable inserts made of hard tool alloys and to describe the most typical types of their damages. The article justifies the relevance of studying the temperature effect of cutting inserts made of (Ti,W)C–Co group hard tool alloys on internal microstresses of the 2nd kind. It contains the data of X-ray studies of samples of hard (TiC 30% WC 66% Co 4%), (TiC 15% WC 79% Co 6%) and (TiC 5% WC 85% Co 10%) alloys using XRD 7000 Shimadzu Maxima automated diffractometer with an add-on heater at temperatures from 20 to 700°C.

Allowance for Internal Microstresses and Texture in Evaluation of Residual Stresses in Cold-Drawn Steel Wires with Micromechanical Models

Under consideration is an allowance for internal grain-scaled stresses in the evaluation of residual macroscopic stress in highly textured polycrystals. The grain-scaled stresses have been evaluated with two micromechanical models: (a) a simplified model developed for a very strong <110> fiber texture and suggesting the corresponding peculiarity of slip pattern in constitutive crystals, and (b) a full-constraint model allowing for accommodation nature of the multi-slip pattern in these crystals. Both models satisfactorily predict the position and relative intensity of the nonlinearities of d{hkl}-sin2y curve. The former model, by treating magnitude of grain-scaled stresses as a fitting parameter, provides better correspondence to experimental data. The latter model, free of fitting parameters, overestimates the grain-scaled stresses, and, consequently, the oscillations of d{hkl}-sin2y curve.