Crystal Indentation Hardness

There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue

Mechanical properties of β-HMX

Background: For a full understanding of the mechanical properties of a material, it is essential to understand the defect structures and associated properties and microhardness indentation is a technique that can aid this understanding. Results: The Vickers hardness on (010), {011} and {110} faces lay in the range of 304-363 MPa. The Knoop Hardnesses on the same faces lay in the range 314-482 MPa. From etching of three indented surfaces, the preferred slip planes have been identified as (001) and (101). For a dislocation glide, the most likely configuration for dislocation movement on the (001) planes is (001) [100] (|b| = 0.65 nm) and for the (101) plane as (101) 101~(|b| = 1.084 nm) although (101) [010] (|b| = 1.105 nm) is possible. Tensile testing showed that at a stress value of 2.3 MPa primary twinning occurred and grew with increasing stress. When the stress was relaxed, the twins decreased in size, but did not disappear. The twinning shear strain was calculated to be 0.353 for the (101) twin plane. Conclusions: HMX is considered to be brittle, compared to other secondary explosives. Comparing HMX with a range of organic solids, the values for hardness numbers are similar to those of other brittle systems. Under the conditions developed beneath a pyramidal indenter, dislocation slip plays a major part in accommodating the local deformation stresses. © 2015 Gallagher et al.; licensee Springer

Investigation of the visuals associated with the national identity in Turkish republic revolution history and kemalism textbooks

In this research, images related to national identity were examined in history textbooks. In the first stage, nationalism, the historical course of the Turkish national identity and related literature were examined, and some components of national identity were determined. Various categories related to national identity have been formed from the elements obtained. The data about the categories were collected through document analysis. In the second phase, 8 history textbooks taught in the years 1930-2014 were selected as samples. Content analysis was used in the examination of the mentioned textbooks, and quantitative method was chosen in data analysis. In this context, data obtained by document analysis were analyzed with SPSS 13 statistical program. Chi-square tests, Bonferroni corrections for chi-square tests and graphs were used in the analyzes. The significance level for all analyzes was taken as .05. In the research, it was determined that republic values and revolutions, national struggle and the images related to the founder leader Mustafa Kemal Atatürk be a most used in Turkish Republic Revolution History and Kemalism textbooks concerning national identity. In addition, it has been found that the images of national symbols such as homeland maps, flag, parliament, and capital are used too much for the national identity. © 2018 Public Library of Science. All rights reserved

Crystal Indentation Hardness

Dear Colleagues, Determinations of the indentation hardness properties of crystals have expanded to cover the full characterizations of their important elastic, plastic and cracking behaviors, particularly as accomplished with the increased measuring capabilities of nanoindentation hardness testing. No crystal structure of any bonding type is either too soft or too hard to prevent measurement with a suitable probing indenter. The current Special Issue is devoted to surveying the topic with emphasis given in a collection of reports to: (1) the diversity of crystals being tested; (2) the variety of measuring techniques; and (3) the wealth of information being obtained. Prof. Dr. Ron Armstrong Dr. Stephen Walley Prof. Dr. Wayne L. Elban Guest Editor

Vickers Microindentation Hardness Testing of Brazed Joints in Aluminium

This learning activity will provide an introduction to using Vickers microindentation hardness profiling for pre-fabricated aluminum joints. This exercise allows students to calibrate a Vickers microindentation hardness tester, to measure hardness profiles across, and to use computer software to plot the correlation between strength and hardness in the materials. This module is intended for upper-level and advanced undergraduates and can be done in three one-hour class periods. The document is available to download in PDF file format

Synthesis and Biological Activities of Topopyrones

Structure–activity studies were employed to investigate the stabilization of DNA–topoisomerases I and II covalent binary complexes by topopyrone analogues. The synthesis of five new topopyrone derivatives and study of their ability to stabilize DNA–topoisomerase I and DNA–topoisomerase II covalent binary complexes are described. The biochemical assays suggest that the orientation of the fused 1,4-pyrone ring and halogen substituents contribute importantly to the overall potency of the topopyrones as topoisomerase poisons