Obtaining mechanical properties of superelastic materials from microindentation data

Indentation is one of the most widely used techniques for determination of mechanical properties of materials. Many various methods for extraction of mechanical properties had been introduced for elasto-plastic materials. Later, the use of microindentation were extended to composite, porous, anisotropic and multi-phase materials. Use of microindentation for determination of such materials properties is impeded due to its complex behavior and larger number of material properties’ constants. This work is focused on indentation of superelastic materials with austenite - martensite phase transformation and extraction of material properties. Finite element (FE) modeling was used to model indentation of superelastic alloys with Berkovich indenter. Several series of simulations were calculated with different elastic modulus of austenite and martensitic phases, stresses of phase transition in both directions. It is possible to create a method for determining mechanical characteristics of superelastic alloys using results of various materials’ simulations. Elasto-plastic material usually can be described with three constants: Young modulus, yield stress, strain-hardening exponent. Unlike elasto-plastic materials, superelastic materials have a larger number of properties due to their complex behavior. It includes stress of austenite transformation start and finish, stress of martensitic transformation start and finish, elastic modulus of austenite and martensitic phases, maximum transformation strain. Presence of many additional materials’ constant make the problem of determination of its determination much harder. Several works exist that are proposing method for determination of phase transformation stresses [1] or elastic modulus of two phases (similar to Olive-Pharr method) [2] using spherical indenter. Yet, elastic modulus and transformation stress are found to make similar effect on indentation results. That being the case, the united method requires processing and determination of mechanical properties of superelastic by indentation

N-(2-Methyl­phen­yl)benzene­sulfonamide

In the title compound, C13H13NO2S, the conformation of the N—H bond is anti to the ortho-methyl group on the aniline ring, in contrast to the syn conformation observed with respect to the ortho-chloro group in N-(2-chloro­phen­yl)benzene­sulfonamide. The dihedral angle between the two benzene rings is 61.5 (1)°. Mol­ecules are linked into chains running along the a axis by N—H⋯O hydrogen bonds

Modeling of Crystallographic Texture Formation in Hot-rolled Sheets of Ferritic Steel

It is known that hot rolling of ferritic steel leads to formation of texture inhomogeneous through sheet thickness [1-3]. For analysis of processes, which induce formation of texture inhomogeneity, finite element method simulation of hot rolling was carried out at macro- and mesoscopic levels. Crystallographic texture is a sensitive indicator of plastic deformation process so it is possible to use it to assess the quality of the simulation. Simulated orientation distribution functions are in a good agreement with experimental result in central part of sheet (middle in thickness), but does not substantially correspond with it in outer layer. Reasons of these inconsistencies were analyzed and following were singled out: disconnection of texture with mechanical properties, possible operation of some other mechanism of deformation apart from crystallographic slip

Methods of Research of Shape Memory Effect and Superelasticity in the Alloy Ti-22%Nb-6%Zr

Cyclic tensile tests were carried out as applied to annealed foils of the superelastic Ti-22Nb-6Zr alloy (at.%) as well as indentation of these foils with an increasing amplitude of indenter intrusion in the sample at temperatures lowering from 20∘ down to -60-70∘C. Mechanical tests were performed on samples cut along andacross the rolling direction. According to the results of measurements of mechanical properties, it is established that during cyclic stretching of foils in the rolling direction, superelasticity manifests itself, and also material training is observed with subsequent preservation of the maximal renewable deformation. When the foil is loaded in the transverse direction, no superelasticity is observed, moreover, some samplesare destroyed even with a deformation of 2%. With a decrease in the annealing temperature of foils, the curve of the continuous change of loading with the depth of indenter penetration undergoes substantial changes, which indicate the appearance of a superelastic deformation under the indenter. Curves of monotonic loading and discharge undergo an inflection, and the plastic deformation region is substantially reduced. From the discharge curves in this case, we can calculate two elastic modules, typical for the usual elasticity and superelastic behavior of the alloy. In general, the main characteristics of the continuous indentation curve depend on the amount of the martensitic phase. The dependence of the modules of elasticity for foils, coolingdown to -(60-70∘C), and for their subsequent heating up to the room temperature is constructed

Diversity of felodipine solvates: Structure and physicochemical properties

Solvates of the calcium-channel blocking agent felodipine with three structurally related common organic solvents, acetone (ATN), dimethyl sulfoxide (DMSO) and acetophenone (APN), are described. A relationship between the felodipine packing arrangement in all known solvates and the van der Waals volume of the solvent molecule is established. Intermolecular interaction energies in the crystals are examined using the PIXEL approach in order to rationalize the difference between alternative molecule packing arrangements. DSC studies show that the desolvation onset temperatures of the solvates are closely comparable, despite the large difference in the boiling points of the solvent molecules. The enthalpies of formation derived from the calorimetric data for the solvates are also found to be similar, despite the difference in the van der Waals volume of the solvent molecules.This work was supported by a grant from the President of the Russian Federation no. МК- 67.2014.3 and Russian Foundation for Basic Research (project № 14-03-31001).This is the accepted manuscript. The final version is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CE/C5CE00350D#!divAbstract