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Editorial

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Prediction of steel flow stresses under hot working conditions

An austenitic stainless steel was deformed in torsion over a temperature range of 900-1200 °C using strain rates of 1, 5 and 10 s-1. The stress vs. strain curves determined were corrected for deformation heating and the flow stress was found to rise in the initial work-hardening regime, reaching a maximum before dropp…

Ferrous sulphate mono and heptahydrate reduction of hexavalent chromium in cement: effectiveness and storability

In Community legislation, substances containing hexavalent chromium are classified as carcinogenic, mutagenic and sensitizing. In cement, hexavalent chromium intensifies sensitization and may set off severe allergic reactions in workers in routine contact with the product, whether in the factory or on construction sit…

Ceramic properties of clay from the Asseiceira quarry at Tomar, Portugal

The clay mined at the Asseiceira quarry near the city of Tomar, Portugal, has traditionally been used to manufacture hollow brick. However, since an assessment has shown the ceramic properties of the strata to vary, the quarry could potentially produce clay blends of different qualities to form raw materials appropria…

Laser beam welding of titanium nitride coated titanium using pulse-shaping

A new welding method which allows the assembly of two titanium nitride coated titanium parts is proposed. The welding procedure utilizes the possibility for pulse-shaping in order to change the energy distribution profile during the laser pulse. The pulse-shaping is composed of three elements: a) a short high power pu…

Hygrothermal effects on dynamic mechanical snalysis and fracture behavior of polymeric composites

Polymer composites used above their glass transition temperatures Tg present a substantial degradation of physical properties; therefore a material's glass transition temperature and its change with moisture absorption are of practical importance. Little attention has been paid to the role of the adhesive bonding betw…

Fatigue crack growth resistance and crack closure behavior in two aluminum alloys for aeronautical applications

Aluminum-lithium alloys are candidate materials for many aerospace applications because of their high specific strength and elastic modulus. These alloys have several unique characteristics such as excellent fatigue crack growth resistance when compared with that of the conventional 2000 and 7000 series alloys. In thi…

Kinetics of thermal decomposition of titanium hydride powder using in situ high-temperature X-ray diffraction (HTXRD)

The thermal decomposition of titanium hydride powder (delta-phase) to titanium (alpha-phase) was investigated by means of thermogravimetric analysis (TGA) and high-temperature X-ray diffraction (HTXRD) in high vacuum. The delta-to-alpha phase transformation was followed in situ by HTXRD at temperatures varying from ro…

Characterization of structural alteration in diamond turned silicon crystal by means of micro raman spectroscopy and transmission electron microscopy

In this work, (100) oriented monocrystalline silicon samples were single point diamond turned under conditions that led to a ductile and brittle regime. Raman spectroscopy results showed that the ductile regime diamond turning of silicon surfaces induced amorphization and, on the contrary, in the brittle mode machinin…

Strengthening of Masonry Structures under Compressive Loads by FRP Strips: Local-Global Mechanical Behaviour

Optimization of the operative conditions for heteropolyacids synthesis through ion exchange

Phospho-tungstic and phospho-molybdic Wells-Dawson heteropolyacids, H6P2W18O62 .xH2O and H6P2Mo18O62 .xH2O respectively, were synthesized through ion exchange with a higher yield (~ 90%) than the conventional organic route (~ 70%). Pure, non-degraded heteropolyacids are obtained when the corresponding ammonium salt [(…

Residual analysis applied to S-N data of a surface rolled cast iron

Surface rolling is a process extensively employed in the manufacture of ductile cast iron crankshafts, specifically in regions containing stress concentrators with the main aim to enhance fatigue strength. Such process hardens and introduces compressive residual stresses to the surface as a result of controlled strain…

Europium incorporated into titanium oxide by the sol-gel method

In this work titanium sol was prepared from tetraethylorthotitanate (TEOT) in ethanol, stabilized with beta-diketonate 2,4 pentanedione in molar ratio 1:1 homogenized by magnetic stirring, europium ion was add as structural probe. The xerogels were heat treated at 500, 750 and 1000 °C and the characterization was real…

Nucleation and growth during recrystallization

The evolution in the understanding of the recrystallization phenomena is summarized in this paper. Initially the main developments concerning recrystallization are presented from a historical perspective. Definitions and concepts involving recrystallization are presented regarding it as a solid-state reaction that occ…

Measurement of oxygen atom diffusion in Nb and Ta by anelastic spectroscopy

Impurity interstitial atoms present in metals with BCC structure can diffuse in the metallic matrix by jumps to energetically equivalent crystallographic sites. Anelastic spectroscopy (internal friction) is based on the measurement of mechanical loss or internal friction as a function of temperature. Due to its select…

Hardness analysis and morphological characterization of copper-zinc alloys produced in pyrophosphate-based electrolytes

In this work, copper-zinc alloy coatings on mild steel substrates were obtained in nontoxic pyrophosphate-based electrolytes, at room temperature and under continuous current. The effects of bath composition and current density on the hardness of the coatings, as well as on their morphologies, were evaluated. The resu…

Luminescence spectroscopy applied to a study of the curing process of diglycidyl-ether of bisphenol-A (DGEBA)

This work involved the application of luminescence spectroscopy under steady-state conditions to study the curing process of the epoxy resin diglycidyl-ether of bisphenol-A (DGEBA) using the curing agents 4,4'-diaminodiphenylmethane (DDM) and 4,4'-diaminodiphenylsulfone (DDS). Two fluorescence methods were employed: t…

Comparison of analytical models with cellular automata simulation of recrystallization in two dimensions

Cellular automata simulation of recrystallization in two dimensions is carried out. The simulated microstrutural evolution is compared in detail with the predictions from mathematically exact analytical theories considering both kinetic and geometrical aspects. Very good agreement is observed between the cellular auto…

The optical absorption of gamma irradiated and heat-treated natural quartz

Quartz with aluminum as impurity absorbs energy from ionizing radiation and modifies its color. Colorless quartz becomes smoky or dark smoky (morion quartz) when exposed to gamma rays. By heat-treatment, smoky quartz may become successively greenish, yellowish, or brownish as the irradiation dose increases. Natural, c…