Use of zeolite-rich rocks and waste materials for the production of structural lightweight concretes

This paper aims at testing the use of mixtures constituted by natural zeolitized products and SiC-bearing industrial wastes (sludge deriving from polishing of porcelain stoneware tiles, hereafter DPM) for the production of lightweight expanded aggregates as constituents of structural and/or thermo-insulating lightweight concretes. Two commercial products have been used as zeolite natural source: Cab70 (Yellow facies of Campanian Ignimbrite) and IZclino (Turkish clinoptilolite-rich epiclastite). Different amounts of a calcareous material (Pozzano limestones — hereafter CP) from the Sorrento peninsula (Naples — Italy) were also added to a Cab70–DPM mixture. All raw materials were characterized by means of mineralogical (XRPD) and chemical (XRF) analyses. All the products and mixtures were tested from a technological point of view by means of fusibility and firing tests in order to evaluate the expanding properties. It was evidenced that the expansion of the mixture was deeply depending on the occurrence of SiC in the industrial waste. The addition of CP (10 wt.%) to the mixtures accounts for an even increased expansion, though this is accompanied by a worsening of the mechanical features of the material.These results along with literature data allowed to select 3 mixtures (70% Cab70–30% DPM, 70% IZclino–30% DPM, 60% Cab70–30% DPM–10% CP) and each of them was used for the preparation of 5 l of lightweight aggregates afterward employed for the manufacture of lightweight concretes. It was remarked that natural zeolitized materials mixed with DPM (30 wt.%) can provide lightweight aggregates with densities ranging between 0.8 and 1.0 g/cm³ suitable for the preparation of structural lightweight concretes. The addition to the mixture of CP (10 wt.%) produces less dense aggregates (0.6–0.7 g/cm³) potentially useful for the manufacture of thermo insulating lightweight concretes.     

On the Use of the Flickermeter to Limit Low-Frequency Interharmonic Voltages

The possibility of using the IEC flickermeter for the assessment of the limits of low frequency interharmonic voltages is critically analyzed. The response of flickermeters to interharmonic components is analytically investigated, obtaining approximation formulas for the calculation of Pst in the presence of couples of components at frequencies that are symmetric with reference to the fundamental and in the presence of one or more single components. The instrument characteristics and limitations are also highlighted, using the results obtained from a numerical implementation of the IEC flickermeter. Finally, the general problem of the limits of low frequency interharmonic voltages is discussed and practical solutions are proposed.     

Assessing the health research’s social impact: a systematic review

Scientometrics - In recent year, a growing attention is dedicated to the assessment of research’s social impact. While prior research has often dealt with results of research, the last decade...     

The influence of tool rotation on an incremental forming process

Incremental forming is a sheet metal forming process characterized by high flexibility; for this reason, it is suggested for rapid prototyping and customised products. On the other hand, this process is slower than traditional ones and requires in-depth studies to know the influence of certain process parameters.The purpose of this study is to investigate the influence of tool rotation on an incremental forming process. Pyramid frusta are created for different speeds and both directions of tool rotation, starting with aluminium alloy sheets; a punch with hemispherical head is used as tool.The variation of speed of tool rotation puts into the variation of friction coefficients, so these ones are preliminarily evaluated for different speeds, in order to explain the influence of tool rotation in terms of forming forces, temperatures reached and surface roughness. The evaluation of these quantities highlights the influence of tool rotation, both in terms of speed and direction of rotation, on the components of the forming forces in the sheet plane, whereas neither the heating of the sheet caused by the friction nor the surface finishing feel the effects of this parameter significantly.     

Automated Procedure for Roll Pass Design

The aim of this work has been to develop an automatic roll pass design method, capable of minimizing the number of roll passes. The adoption of artificial intelligence technologies, particularly expert systems, and a hybrid model for the surface profile evaluation of rolled bars, has allowed us to model the search for the minimal sequence with a tree path search. This approach permitted a geometrical optimization of roll passes while allowing automation of the roll pass design process. Moreover, the heuristic nature of the inferential engine contributes a great deal toward reducing search time, thus allowing such a system to be employed for industrial purposes. Finally, this new approach was compared with other recently developed automatic systems to validate and measure possible improvements among them.     

Specific pressure in steel rod rolling with grooves

In the design of roll stands for use in grooved steel rod rolling, the contact pressure between the rolls and the incoming workpiece is very important. This value can be estimated with the help of a number of analytical and semiempirical models described in the published scientific and technical literature. In this study, the possibility of using numerical simulation in determining the contact pressure during the rolling of a round bar with oval grooves is analyzed. The results of the numerical analyses are then compared with those of two other modified analytical models.     

The Wear Behaviour of Composite Materials with Epoxy Matrix Filled with Hard Powder

The wear behaviour of composite materials, sliding under dry conditions against smooth steel counterface, has been investigated. The composite materials consisted of glass woven fabric reinforcing three different systems of matrix: epoxy resin, epoxy resin filled with powders of silica and epoxy resin filled with powders of tungsten carbide. The powders were mixed in a volumetric fraction of 6% with the epoxy resin. Three laminates were manufactured by hand lay up technology. The sliding tests have been conducted on the specimens, cut from the three laminates, with a pin on disk apparatus. The results put in evidence different wear behaviours of the composite materials observed at different values of sliding speed and pressure. The presence of different wear mechanisms has been appreciated by SEM-micrographic examinations.     

Comparison of Tensile Strength of Composite Material Elements with Drilled and Molded-in Holes

Holes are generally obtained through drilling operations; this causes a property decrease for polymer composites reinforced by fibers, brought about by damage due to fiber continuity interruption, and to delamination between the laminate layers. In this study, specimens with circular holes, both drilled and molded-in, obtained in different ways, are tested in order to investigate on whether it is possible to avoid the decrease in mechanical properties of components with holes. In particular, a number of laminates were manufactured by RIFT (Resin Infusion under Flexible Tool), a closed mold process capable of obtaining large and complex forms, impregnating, under vacuum, a dry preform placed on the rigid mold. At specific points of these laminates, molded-in holes are generated during the resin infusion phase, operating in two different ways: displacing or cutting the fibers in the dry preform. Tensile tests were carried out in order to compare the mechanical properties of elements in composite materials which have molded-in holes generated during the impregnation process, with the properties of those with holes produced after the resin cure by drill operations.