Influence of combined impact and cyclic loading on the overall fatigue life of forged steel, EA4T

The performance of forged steel, EA4T, used in rail industry, under simulated in service conditions, i.e. combined impact - cyclic loading, was investigated through a comprehensive experimental programme. The standard Paris-Erdogan fatigue design curve parameters, m and C, were calibrated to account for the effect of the impact component of loading. A minimum threshold for impact load component, identified in the experiments, was also incorporated in the proposed empirical model. Comparison with experimental findings indicated that this “modified” Fatigue design curve could predict the fatigue life of pre impact loaded specimens with sufficient accuracy. It was therefore suggested that the modified model may be used as a novel design tool for predicting the overall fatigue life of components made of this material under the specified combined impact and fatigue loading conditions.Publisher Statement: The final publication is available at Springer via http://dx.doi.org/10.1007/s12206-016-0923-

Antimicrobial and antioxidant screening of curcumin and pyrocatechol in the prevention of biodiesel degradation: oxidative stability

Owing to its hygroscopicity biodiesel may accumulate water during storage, which becomes favorable to the growth of microorganisms. In order to control microbial contamination, use of various chemical biocides has been studied. However, the addition of a natural substance simultaneously with antioxidant and microbial growth inhibition could prove advantageous in the prevention of biodiesel oxidation and microbial contamination. Curcumin and pyrocatechol are antioxidant agents, which also exhibit microbial growth inhibition abilities. This research effort aimed at evaluating the addition of curcumin and pyrocatechol to biodiesel produced from various vegetable sources (waste frying oil, soybean oil, cottonseed oil, sesame oil, macaúba almond oil and microalgae oil). The combined addition of 1% (w/w) water and curcumin (viz. 0.2% (w/w) for biodiesel from spent frying oil, 0.5% (w/w) for biodiesel from soybean oil, 0.1% (w/w) for biodiesel from cotton seed oil, 0.5% (w/w) for biodiesel from sesame seed oil, 0.2% (w/w) for biodiesel from macaúba almond oil, and 0.2% (w/w) for biodiesel from microalgae oil) were those processing variables that promoted the best fungistatic and antioxidant effects, allowing maintenance of an unfavorable environment for microbial growth in biodiesel inoculated with the ubiquitous filamentous mold Paecilomyces variotii Bainier.Project funding by CNPq (National Council for Scientific and Technological Development - Brazil) (CNPq Ref. No. 404808/ 2013-1, Project ‘Studies on Biodiesel: Development of analytical methods for the characterization and quality control, and research of new natural additives to improve the quality of this biofuel’), is hereby gratefully acknowledged. This work received support from CNPq, National Council for Scientific and Technological Development Brazil, in the form of Research Productivity (PQ) fellowships granted to Victor M. Balcão (Ref. No. 306113/2014-7) and Marco V. Chaud (Ref. No. 309598/2014-1). The authors have no conflicts of interest whatsoever to declare

Determination of water content in clay and organic soil using microwave oven

The article deals with the techniques of soil water content determination using microwave radiation. Its practical application would allow solving the problems of resource efficiency in geotechnical survey due to reduction of energy and resource intensity of laboratory analysis as well as its acceleration by means of decreasing labour intensity and, as a result, cost reduction. The article presents a detail analysis of approaches to soil water content determination and soil drying, considers its features and application. The study in soil of different composition, typical for Western Siberia including organic and organic-mineral ones, is a peculiarity of the given article, which makes it rather topical. The article compares and analyzes the results of the investigation into soil water content, which are obtained via conventional techniques and the original one developed by the authors, consisting in microwave drying. The authors also give recommendation on microwave technique application to dry soil

Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview

The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly explained, and the different international standards for each method are summarized. The limits for each scale are explored, and the different forms to calculate hardness in each method are compared and established. The influence of elasticity and plasticity of the material in each measurement method is reviewed, and the impact of the surface deformation around the indenter on hardness values is examined. The difficulties for practical conversions of hardness values measured by different methods are explained. Finally, main issues in the hardness interpretation at different scales are carefully discussed, like the influence of grain size in polycrystalline materials, indentation size effects at micro-and nanoscale, and the effect of the substrate when calculating thin films hardness. The paper improves the understanding of what hardness means and what hardness measurements imply at different scales.Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University ((Faculty Grant SFO Mat LiU) [2009 00971]</p

A quick approach for rheological evaluation of warm asphalt binders using response surface method

This paper describes a quick approach for quantification of the effects of a chemical warm named Rediset, and its interactions with temperature and aging on the rheological properties of asphalt binders using Response Sur-face Method. The central composite method was applied to design experimental programs for three test temperature conditions, namely; very high temperature (120–180 °C), high temperature (46–82 °C), and intermediate temperature (19–31 °C). Rotational viscosity, G*/sin δ and G*sin δ were selected as parameters to assess the effects of the chemical warm additive on the rheological properties of asphalt binders for different aging conditions. Evaluation of the effects of this additive on the transformed value of G*/sin δ at high temperatures indicates that additive content has significant effect on Ln(G*/sin δ). The results for intermediate temperatures show that this additive has a positive effect on G*sin δ of asphalt binders

Experimental study and numerical reproduction of self-weight consolidation behavior of thickened tailings

Abstract: Thickened tailings, defined as mineral wastes that behave as a non-Newtonian fluid, show a small yield stress and release a small amount of water following deposition. Thickening has become an increasingly used option in tailings management. This paper presents a detailed examination of gold mine thickened tailings undergoing self-weight consolidation, which is an important mechanism affecting soft soils immediately after deposition. Self-weight consolidation was evaluated using a column equipped with water pressure transmitters whereas a slurry consolidometer was employed to obtain the compressibility relationship under low vertical effective stresses. The piecewise-linear model CS2 was used to model the experimental self-weight consolidation test. This model proved very accurate in reproducing the observed behavior. Both the test results and the model results also confirmed the absence of sedimentation in the thickened tailings, which is in agreement with values reported in the literature related to similar materials

X-ray computed tomography for additive manufacturing: a review

In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM

Influence of slag composition on the stability of steel in alkali-activated cementitious materials

Among the minor elements found in metallurgical slags, sulfur and manganese can potentially influence the corrosion process of steel embedded in alkali-activated slag cements, as both are redox-sensitive. Particularly, it is possible that these could significantly influence the corrosion process of the steel. Two types of alkali-activated slag mortars were prepared in this study: 100% blast furnace slag and a modified slag blend (90% blast furnace slag? 10% silicomanganese slag), both activated with sodium silicate. These mortars were designed with the aim of determining the influence of varying the redox potential on the stability of steel passivation under exposure to alkaline and alkaline chloride-rich solutions. Both types of mortars presented highly negative corrosion potentials and high current density values in the presence of chloride. The steel bars extracted from mortar samples after exposure do not show evident pits or corrosion product layers, indicating that the presence of sulfides reduces the redox potential of the pore solution of slag mortars, but enables the steel to remain in an apparently passive state. The presence of a high amount of MnO in the slag does not significantly affect the corrosion process of steel under the conditions tested. Mass transport through the mortar to the metal is impeded with increasing exposure time; this is associated with refinement of the pore network as the slag continued to react while the samples were immersed

Quality changes and shelf-life prediction of a fresh fruit and vegetables purple smoothie

The sensory, microbial and bioactive quality changes of untreated (CTRL) and mild heat−treated (HT; 90 ºC/45 s) smoothies were studied and modelled throughout storage (5, 15 and 25 ºC). The overall acceptability was better preserved in HT samples being highly correlated (hierarchical clustering) with the flavour. The sensory quality data estimated smoothie shelf−life (CTRL/HT) of 18/55 (at 5 ºC), 4.5/12 (at 15 ºC), 2.4/5.8 (at 25 ºC) days. The yeast and moulds growth rate was lower in HT compared to CTRL while a lag phase for mesophiles/psychrophiles was observed in HT−5/15 ºC. HT and 5 ºC−storage stabilized the phenolics content. FRAP reported the best correlation (R2=0.94) with the studied bioactive compounds, followed by ABTS (R2=0.81) while DPPH was the total antioxidant capacity method with the lowest adjustment (R2=0.49). Conclusively, modelling was used to estimate the shelf−life of a smoothie based on quality retention after a short time−high temperature heat treatment that better preserved microbial and nutritional quality during storage.The financial support of this research was provided by the Ministerio Español de Economía y Competitividad MINECO (Projects AGL2013−48830−C2−1−R and AGL2013−48993−C2−1−R) and by FEDER funds. G.A. González−Tejedor thanks to Panamá Government for the scholarship to carry out his PhD Thesis. A. Garre (BES−2014−070946) is grateful to the MINECO for awarding him a pre−doctoral grant. We are also grateful to E. Esposito and N. Castillejo for their skilful technical assistance