Heat treated twin wire arc spray AISI 420 coatings under dry and wet abrasive wear

The influence of applying two different heat treatments such as: deep cryogenic and tempering on dry/wet abrasive wear resistance of twin wire arc spray martensitic AISI 420 coatings was evaluated by using a modified rubber wheel type test apparatus. A load dependency was observed on the abrasive wear rate behavior of both; dry and wet tests. Three body (rolling) and two body (sliding) wear mechanisms were identified in dry conditions, prevailing rolling at lower and higher loads. However, at higher loads, more presence of grooving and pits formation was observed. Coatings tempered at 205 °C/1 h displayed better wear resistance than cryogenic treated ones. A change in wear mechanism between dry and wet conditions was observed; two body wear mechanism predominated respect to three body. In both; dry and wet conditions the microstructure (several inter-splat oxides) as well as strain and residual stress promotes brittle material removal which was more evident in cryogenic and as-sprayed samples during dry test and at higher loads in wet conditions.     

Applying Gaia and AUML for the development of multiagent‐based control software for flexible manufacturing systems: addressing methodological and implementation issues

In this article, we present the development of a simple multiagent‐based system for the control of a flexible manufacturing system. We followed the stages of a methodology specially conceived for the development of agent‐based system, which is an integration of the classical methodology for agent‐oriented analysis and design Gaia, and AUML (Agent‐Unified Modeling Language). We adopted as study case the CIMUBB Laboratory at the University of Bio‐Bio, which has a flexible manufacturing system including three flexible manufacturing cells interconnected by a conveyor belt. In the analysis stage, we identified roles involved, and we design models representing roles and protocols. In the design stage, we applied Gaia agent, services, and acquaintance models from Gaia, and we complemented with AUML as the adopted methodology suggests. With the developed models, we constructed a fully functional system where each agent was built as an independent process tree. Agents communicate by passing messages through the Ethernet network with socket interfaces. Various tests executed in our laboratory scale manufacturing system show the effectiveness of our implementation. Copyright © 2015 John Wiley & Sons, Ltd.     

Growth in the number of references in engineering journal papers during the 1972–2013 period

The number of references per paper, perhaps the best single index of a journal’s scholarliness, has been studied in different disciplines and periods. In this paper we present a four decade study of eight engineering journals. A data set of over 70,000 references was generated after automatic data gathering and manual inspection for errors. Results show a significant increase in the number of references per paper, the average rises from 8 in 1972 to 25 in 2013. This growth presents an acceleration around the year 2000, consistent with a much easier access to search engines and documents produced by the generalization of the Internet.     

Microstructure and Mechanical Behavior of Powder Metallurgy Mg98.5Gd1Zn0.5 Alloy

The Mg_98.5Gd₁Zn_0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg₃Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.