Effects of Grain Boundary Angles on Initial Deformation of 304 Austenitic Stainless Steel under Nanoindentation: A Molecular Dynamics Simulation

Nitrogen-containing 0Cr19Ni10 (304 NG) austenitic stainless steel plays a significant role in Generation IV reactor pressure vessels. The structure and properties of 304 NG are heavily influenced by the grain boundaries (GBs), especially the initial mechanical response and dislocation evolutions. Hence, in this paper, we carried out molecular dynamics (MD) simulations to investigate the effects of the GB angles on the initial deformation of 304 models under nanoindentation. It is found that the GB angle has great effects on the mechanical properties of 304 NG. With the GB angles changing from 90° to 150°, the values of Young’s modulus and maximum shear stress first decrease and then increase due to decreasing of the interaction among the GBs and the grain interiors (GIs) and the smoother shape of GBs. The hardening region slope decreases rapidly result from the GB angles changing the grain size on the both sides, which fully fits the Hall–Petch relationship. After the dislocations reaching the GBs along the slip system, the dislocation piles-up on the GBs at first, and then GBs serve as a source of dislocation and emit dislocation to free surface with the depth of nanoindentation increasing. This work provides a better understanding on the angle effects of GBs in materials.

Resistance of Structural Materials to Deformation in the Case of Linear and Flat Stresses

Annotation: The deformation resistance properties of structural materials in the case of linear and flat stresses are given on the basis of experimental results. The method of estimating the mechanical properties of the material based on the initial deformation diagrams is described. Keywords: Stress, deformation, longitudinal force, internal pressure, stress state, deformation diagram, initial deformation, Yung modulus, Poisson's ratio, anisotropy, strength, yield strength

COMBINED EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF FREE EXTRUSION AT INITIAL DEFORMATION BY BENDING

All geometric formulas necessary for designing the process of extrusion of glasses with a conical bottom are obtained. Further, the obtained formulas will be used to develop scientifically based methods for calculating technological operations of free and constrained extrusion. The substantiation of the use of the wellknown methods of A. L. Vorontsov, developed for extrusion of glasses with a punch with a flat end, for calculating the deformed state of the workpiece is given.

Combined EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF CONSTRAINED EXTRUSION AT INITIAL DEFORMATION BY BENDING

The methodology for calculating the energy-power and deformation parameters of the process of constrained extrusion of glasses with a conical bottom part, starting with the bend of the workpiece. The extrusion of both non-hardening and hardening material is considered. In the latter case, the account of the hardening of the extruded material is described in detail. The above formulas allow us to determine such important parameters of the stamping process as total and specific deforming force, maximum pressure on the die wall, and an increase in the yield stress.

Effect of Mineral Additives on Fusion Behavior of Agricultural Residue Ashes during Combustion or Co-combustion with Lignite

In this work, the ash fusibility behaviour of selected agricultural residues and their blends with lignite was studied, by carrying out chemical, mineralogical, fusibility and thermogravimetric analyses and calculating slagging/fouling indicators for predicting deposition tendencies in boilers. Two additives, bauxite, and clinochlore, were used at varying amounts to reduce ash melting, followed by examining their anti-fusion mechanisms. Initial deformation and softening temperatures of biomass materials were low for combustion processes operating above 900 °C due to their high concentration in K, Na, and P compounds. When the additives were mixed with raw fuels or lignite/biomass blends, the initial deformation of ashes started at temperatures up to 340 °C higher, whereas the fluid temperature in most cases exceeded 1500 °C. Bauxite was more effective than clinochlore. The positive impact of additives was attributed to the mineralogical transformations during ashing to phases with a high melting point through reactions with K, Na-bearing minerals, or CaO of fuel ashes.

Asymptotic Analysis of Nonlinear Resonance Interaction of Capillary Waves of Arbitrary Symmetry on Moving Charged Jet at Multimode Initial Deformation

The problem of research of a nonlinear resonance between capillary waves on a surface of the charged jet at multimode initial deformation moving regarding the material environment is considered. It is shown in analytical asymptotic calculations of the second order on the dimensionless amplitude of oscillations that on a surface of a jet an internal nonlinear resonant interaction of capillary waves of any symmetry, both degenerate and secondary combinational, takes place. Positions of resonances depend on physical parameters of the system: the values of the coefficient of a surface tension and of the radial electric field at a surface of a jet, the velocity of its movement regarding the material environment, the values of the wave and azimuthal numbers of the interacting waves, a range of the waves defining initial deformation.

DETERMINATION OF THE DEPENDENCE OF THE SIZE OF THE FLOATED PARTICLES ON THEIR PROPERTIES AND THE HYDRODYNAMICS OF THE FLOTATION CHAMBER

It is noted that medium-sized particles have the highest flotation rate. Grains of the boundary classes of the size range have a reduced floatability, and they account for more than 50% of all losses of extracted minerals during flotation. The stability conditions of the particle - bubble flotation unit in the chamber of the foam flotation machine are considered. The effect of perturbations of the bubble surface on the size of the floated particles is studied. The amplitude of the initial deformation of the surface and the amplitude of the initial deformation rate of the bubble surface were determined depending on the energy of the turbulent pulsations of the environmental liquid. It is established that the rate of energy dissipation in the chamber of the flotation machine has a moderate effect on the size of the extracted grains. The influence of the surface properties of mineral particles and their mass on the upper value of the particle size range is studied. It is shown that the hydrophobicity of the surface has a significant effect on the size of the mineral particles that remain in contact with the gas phase. The main parameter that characterizes the effect of the hydrophobicity of the surface of the floated particles on the value of the separation force can be the value of the advancing contact angle.

Quantification of sample disturbance for soft, lightly over-consolidated, sensitive clay samples

When using initial deformation from oedometer tests to quantify sample disturbance, a correction for false deformation is sometimes needed. A method to determine this false deformation is presented.