Initiation and stagnation of room temperature grain coarsening in cyclically strained gold films

Despite the large number of experiments demonstrating that grains in a metallic material can grow at room temperature due to applied mechanical load, the mechanisms and the driving forces responsible for mechanically induced grain coarsening are still not understood. Here we present a systematic study of room temperature grain coarsening induced by cyclic strain in thin polymer-supported gold films. By means of detailed electron backscatter diffraction analysis we were able to capture both the growth of individual grains and the evolution of the whole microstructure on the basis of statistical data over thousands of grains. The experimental data are reported for three film thicknesses with slightly different microstructures and three different amplitudes of cyclic mechanical loading. Although different kinds of grain size evolution with increasing cycle number are observed depending on film thickness and strain amplitude, a single model based on a thermodynamic driving force is shown to be capable to explain initiation and stagnation of grain coarsening in all cases. The main implication of the model is that the grains having lower individual yield stress are coarsening preferentially. Besides, it is demonstrated that the existence of local shear stresses imposed on a grain boundary is not a necessary requirement for room-temperature grain coarsening

Seven ways to make a hypertext project fail

Hypertext is an exciting concept, but designing and developing hypertext applications of practical scale is hard. To make a project feasible and successful 'hypertext engineers' must overcome the following problems: (1) developing realistic expectations in the face of hypertext hype; (2) assembling a multidisciplinary project team; (3) establishing and following design guidelines; (4) dealing with installed base constraints; (5) obtaining usable source files; (6) finding appropriate software technology and methods; and (7) overcoming legal uncertainties about intellectual property concerns

Towards the Quantitative Approach to Studying Evolution of English Verb Paradigm

The article focuses on corpus quantitative investigation of English diachronic morphology with respect to irregularregular verb classes. General tendencies of the evolution of English verb paradigm are analyzed. Three groups of English verbs have been observed: irregular and regular ones plus goup of verbs on the stage of transition from irregular category into regular one, i.e. possessing both types of conjugation forms. A considerable amount of e-texts has been processed and correspondence of these three verb classes has been revealed. The results reveal existence of certain correlation between the frequency dynamics of the verb and its belonging to irregular or regular conjugation paradigm

Research into defectiveness of welded joints of steam pipes operated over a long time

Проведено аналіз пошкоджуваності металу зварних з'єднань паропроводів із Cr–Mo–V теплостійких перлітних сталей, які тривалий час експлуатуються в умовах повзучості та малоциклової втоми. Наведені зварні з'єднання пошкоджуються одночасно порами повзучості та тріщинами втоми. Розглянуто фактори, які викликають пошкоджуваність, а також залежність пошкоджуваності від структури зварних з'єднань і умов експлуатації. Їх пошкоджуваність переважно має крихкий характер

Initiation of fatigue damage in ultra-fine grained thin films: Schmid, Taylor or Hall-Petch?

The evolution of fatigue damage in metallic films is usually described by several subsequent stages. First, the dislocation slip induces formation of slip steps and slip bands. Application of further cyclic mechanical load leads to formation of extrusion/intrusion couples and, finally, crack propagation. Although this general description of the fatigue damage development is well established and can be generally applied to different materials, surprisingly little is known about the very early stage of fatigue damage initiation especially for ultra-fine grained (UFG) and nanocrystalline thin films. From the point of view of classical plasticity theory, the plastic slip should occur first within most favorably oriented grains with the highest resolved shear stress that corresponds to the lowest Taylor factor or the highest Schmid factor. The core question which this presentation will try to address can be formulated as following: is it possible to predict where the fatigue damage will be initiated for a given UFG thin film with a given microstructure? Polymer-supported thin Au and Cu films with UFG microstructures were subjected to cyclic strain with different amplitudes. By means of in-situ resistance measurements the cycle numbers corresponding to the very early stage of damage initiation were deduced. The surface and the microstructure of the films were then analyzed by the scanning electron microscopy and electron backscatter diffraction (EBSD). Please click Additional Files below to see the full abstract

Quantitative analysis of infrared contrast enhancement algorithms

This thesis examines a quantitative analysis of infrared contrast enhancement algorithms found in literature and developed by the author. Four algorithms were studied, three of which were found in literature and one developed by the author: tail-less plateau equalization (TPE), adaptive plateau equalization (APE), the method according to Aare Mallo (MEAM), and infrared multi-scale retinex (IMSR). Engineering code was developed for each algorithm. From this engineering code, a rate of growth analysis was conducted to determine each algorithm’s computational load. From the analysis, it was found that all algorithms with the exception of IMSR have a desirable linear nature. Once the rate of growth analysis was complete, sample infrared imagery was collected. Three scenes were collected for experimentation: a low-to-high thermal variation scene, a low-to-mid thermal variation scene, and a natural scene. After collecting sample imagery and processing it with the engineering code, a paired comparison psychophysical trial was executed using local firefighters, common users of the infrared imaging system. From this trial, two metrics were formed: an average rank and an interval scale. From analysis of both metrics plus an analysis of the rate of growth, MEAM was declared to be the best algorithm overall