Quantification of volume deficit of rectangle shaped cast aluminium alloys

AbstractVolume deficit of rectangular shape US 413 and US A356 cast aluminium alloy has been estimated in the present study. The decrease in specific volume directs to a volume deficit in castings and it has been shown as a defect. The volume deficit can be classified as macro cavities, internal porosity, surface sinking and volumetric contraction and measured using mathematical formulae; the actual volume deficit of the given casting was obtained by adding all the defects. Quantification of internal closed porosity has been addressed through X-ray computer tomography. The information regarding the volume deficit and its distribution is critical in minimizing casting defects

Pull-out behaviour of Glass-Fibre Reinforced Polymer perforated plate connectors embedded in concrete. Part I: Experimental program

The Glass Fibre Reinforced Polymer (GFRP) connectors studied in this work were previously proposed by the authors for connecting the outer Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) layers of sandwich panels for prefabricated modular housing. In this building system, SFRSCC was used to totally eliminate the need for conventional reinforcement and to decrease the thickness of the panel's outer layers, with consequent reduction of the global self-weigh of the panels, while GFRP connectors aimed to significantly decrease thermal bridging effects. For a reliable design of the structural elements that make use of these connectors, the mechanical behaviour of this connection should be known and taken into account. The present paper summarizes the results obtained in an experimental research devoted to the assessment of the behaviour of GFRP-SFRSCC connection by performing pullout tests with specimens representative of the developed sandwich panel. The specimens were designed to examine the influence of the number and geometry of holes executed in the GFRP connector that assure the connection between these two materials.This work is part of the research project QREN number 5387, LEGOUSE, involving the companies Mota-Engil, CiviTest, the ISISE/University of Minho and PIEP. The first author would like to thank the financial support provided by PAIP/UNILA. The third author wish to acknowledge the grant SFRH/BSAB/114302/2016 provided by FCT.info:eu-repo/semantics/publishedVersio

An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process

Magnesium alloy is a light weight metallic material which offers good engineering properties and environmental advantages. Most cast components in this material are produced by the traditional casting processes, predominantly the die-casting process. The Expendable Pattern Casting Process (EPC process) is a relatively new casting process which provides many design, processing and environmental benefits. However, the process differs significantly from the conventional empty mould sand casting process and there is the need for research to develop an understanding of the process parameters. The research was established to provide a preliminary evaluation of the production of magnesium base alloy castings by the expendable pattern casting process under gravity and counter gravity pouring. The major process parameters investigated were filling pressure, pouring temperature and pattern bead density. The problems experienced in applying this process for this material in the experimental research were defined. Microstructures and mechanical properties of the cast specimens were investigated and reported. The results showed that the quality of test bar specimens produced by the EPC process under counter gravity pouring with optimised process parameters was compatible with the quality of castings produced by the conventional sand casting process. In addition to the experimental research a review was conducted of the modelling of different methods of pouring. The pouring methods considered were bottom gating in gravity pouring, counter gravity pouring in an empty cavity mould process, and expendable pattern casting processes under both gravity and counter gravity pouring. A quasi one dimensional fluid mechanics analysis was conducted to explain the effect of pattern degradation on the delay in mould filling

The effect of water storage and simulated cleansing on some properties of two newly developed denture base materials

Ph. D ThesisHeat-cured PMMA has been used to make denture bases about 80 years ago due to its having superior properties in comparison with other polymers. However, some properties need improvement, such as impact and fatigue strength and the long curing duration. Recently, new denture base materials have been developed and introduced to the market to overcome PMMA shortcomings. These new materials include the Eclipse resin system, a light-cured resin, and Weropress polymer, a pourable cold-cured resin, which can be polymerised in a relatively short time. No studies have been conducted measuring their properties for short and long term use. Therefore, these materials were tested and compared with heat- and cold-cured PMMA denture base materials, acting as positive and negative controls, respectively, to determine if they can be used as alternatives to conventional materials in long term use. The comparison was performed in terms of flexural properties, water sorption and solubility, surface properties (roughness and hardness), and colour stability. The comparison was made in three stages, at the baseline, after water storage for different time intervals, and after simulated cleaning with a liquid-based cleanser (Dentural), and a tablet-based cleanser (Poligrip). The findings showed that Eclipse was statistically superior to the positive control in all tested properties at baseline, after water storage, and after cleansing, except for roughness, although no statistically significant difference was found, while it was clinically superior in strength, hardness and colour stability. Weropress showed no statistically significant difference from that of the negative control, but did have very high colour stability, and it was not clinically lower than positive control except in strength. To conclude, in terms of the tested properties, Eclipse can be used as an alternative denture base material, while Weropress is recommended as a denture base material for cases with high aesthetic demands and low mechanical needs, or as a denture base material on a temporary basis.Ministry of High Education and Scientific Research in Ira

Thermo-physical properties measurement and steel - ceramic shell interactions in investment casting

Investment casting is a process in which a ceramic shell is prepared on a wax or foam pattern. The wax is melted out or the foam is burnt out and the shell is sintered to have sufficient strength to withstand casting conditions. The investment casting process is very important as it produces near net shape castings which reduce the need for subsequent operations of castings like machining etc. Investment casting shells are subjected to a number of heating cycles during pattern removal, firing, preheating before pouring and finally during solidification. The thermo-physical properties of the shell play an important role during these processes. One focus area of this research was measuring the thermal conductivity and the specific heat capacity of investment casting shells. The measured properties were included in a simulation software database (Magmasoft). A second focus area of the research was casting surface defects due to liquid steel - ceramic shell interactions. A special cube-shaped specimen with a deep pocket region was designed and simulated using Magmasoft. Three different types of shells were prepared with silica, zircon and alumina flour in the prime coat slurries. For comparison, shells prepared around the same pattern were obtained from three industrial foundries. Shells were preheated to 800⁰C and poured with HY130 steel. Shell samples in contact with the steel were taken from the pocket region of the castings, polished and SEM/EDS analyzed. Multiple interaction products included complex Mn-Si-O, Al-Si-Mn-O and Fe-Si-Mn-Al-O oxides were experimentally identified. The experimental results are discussed with respect to the thermodynamic predictions. The results can be used for shell material selection and to identify casting procedures that would limit these defects --Abstract, page iii

Classification of Metals used in the Sand Casting Process

The Sand Casting Process And The Different Methods Used To Cast The Metals Are The Subjects Of This Paper. Casting Is A Manufacturing Process For Creating Complex Material Shapes. A Large Classification Is Needed To Understand The Metals Used By Researches, Why They Were Used, And What The Most Commonly Used Metal For Their Research Is. We Studied And Understanded The Various Types Of Sand Casting Processes Used By The Researchers In This Review Paper. And We Categorized And Graded All The Papers We Reviewed And Classified Based On Their Respective Study Areas And Material Use

Solidification behaviour of Al-Sn-Cu immiscible alloys and Al-Si cast alloys processed under intensive shearing

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Alloy castings are usually solidified with a coarse columnar grain structure under normal casting conditions unless the mode of the solidification is carefully controlled. It is desirable for the grain structure to be fine and equiaxed to improve their mechanical performance as finished castings. It is possible to develop a fine and equiaxed grain structure either by increasing the number of nucleation sites or by grain multiplication. Immiscible alloys with a microstructure in which a soft phase is dispersed homogeneously in a hard matrix have significant potential applications in advanced bearing systems, especially for the automotive industry. Despite considerable efforts made worldwide, including extensive space experiments, no casting techniques so far can produce the desired immiscible microstructure of alloys. Experimental results on Al-Sn-Cu immiscible alloys have confirmed that intensive shearing using melt conditioning by an advanced shearing technology (MCAST) unit, is an effective way to achieve a fine and uniform dispersion of the soft phase without macro-demixing, and that such a dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm for 60 s will be adequate to produce a fine and uniform dispersion of the Sn phase, and that a higher shearing speed and prolonged shearing time can only achieve further minor refinement. A study of Al-Si hypoeutectic and hypereutectic alloys presents the effects of the processing temperature and intensive shearing on the microstructural and mechanical properties which have been investigated systematically. Attempts have been made to explain the solidification mechanism with intensive melt shearing. The sheared melt was cast into tensile test samples by high pressure die caster (HPDC) to examine the microstructures and mechanical properties. The experimental results reveal that significant grain refinement and uniformity of grains was achieved by the intensive shearing and also a considerable increase in mechanical properties with pouring temperature by changing intermetallic particles morphology, the position of defect band and reduced microscopic defects

Reinforced brick-masonry light vaults : semi-prefabrication, construction, testing and numerical modeling

This work deals with short to mid span-length light vaults made of reinforced brick-masonry. The research is oriented at proposing semi-prefabrication and construction techniques. Numerical models for predicting the structural behavior of this type of structures are developed. Experimental research is performed with the following three main objectives: (i) validating the proposed construction techniques, (ii) investigating the structural performance, and (iii) calibrating the numerical models. The obtained results show that the proposed techniques are feasible, and that the structural behavior is adequate in terms of ductility and of strength. The structural system can be modeled with the developed numerical tools.This work has received financial support from the Catalonian Government (CIDEM, "CERARMAT" IT - Technological Innovation - project 605) the Spanish Government (Ministry of Industry and Energy, "PRECERAM" ATYCA project M172/1999) and the European Commission ("ISO-BRICK" CRAFT - Cooperative Research - Project G5ST-CT-2001-50095). All these supports are gratefully acknowledged

The effect of aerosol exposure on foundry workers and arc welders at a large engineering plant in South Africa

ThesisSouth African data regarding the extent of aerosol exposure and health effects in the workplace are limited . Furthermore, a shortage of industrial hygiene- and epidemiological data from large scale studies exist. Given the increasing concern about the health of industrial metal workers, an inhalation exposure study of South African iron foundry workers and welders at a large engineering plant in Bloemfontein, was undertaken. The aim of the study was to compile a source inventory, identifying and characterising all health related inorganic aerosols to which metal workers of the plant are potentially or actually exposed. In addition, the exposure risk was assessed by the integration of aerosol concentrations and biological data from urine analyses. Aerosols were sampled by means of time sequence particulate sampling on streaker filter frames and analysed with Particle Induced X-ray Emission (PIXE) on the Tandem van de Graaff accelerator of the University of the Witwatersrand, Johannesburg. The streaker is analysed in 1 mm steps, corresponding to 1 hour of exposure. PIXE analysis yielded concentrations or detection limits of elements AI, Si , P, S, CI , K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, In, Br and Pb. The urine of selected exposed workers was sampled according to NIOSH method 8310 and analysed using Atomic Absorption (AA) spectrometry for the urine-metal concentrations In, Cd, Co, Ni, Mn, Cu, Cr, AI , Fe, Pb, Si and V. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1 ), peak expiratory flow (PEF), peak inspiratory flow (PIF), average expiratory flow between 25 % and 75 % of FVC (FEF2s-7S), expiratory flow at 25 % of FVC (Vma>e2S), expiratory flow at 50 % of FVC (VmaxSO) , expiratory flow at 75 % of FVC (Vmax7s) and forced expiration time (100 % FVC) (FET1oo), was conducted with a Cosmed Pony spirometer. This was done to provide a physical image of the workers' lungs. A new method for the assessment of aerosol inhalation exposure risk, called AIER, using aerosol concentrations and metal urine concentrations, is proposed for estimation of the inhalation risk. The assumptions and calculation for the new method are presented. A number of sources or source categories have been identified in the foundry's and welding shop's air by making use of patterns of time variations and elemental ratios. Six sources namely crustal particles, sulphur, In-Pb-CI, two distinct components of different castings and other heavy metals were identified as sources. The main pollutants and the relative contributions from other sources have been identified for iron foundries and welding shops with recognised air quality problems. Overexposure occurred during specific operations which was also quantified for rectification. The urine analysis of the foundry workers yielded high concentrations of Cd, Cu, Fe and Si. It is assumed that the Fe and Si concentrations are exposure related. The analysis of urine from the welders yielded high concentrations of Ni, Cr and Fe. Although Ni concentrations in the workroom air were low, the occurrence of all three elements in the urine may ·be as a result of chronic exposure to welding fumes in their workplace. Except for vanadium, no statistical significant differences (P > 0.05) were found between the different metal urine concentrations of the workers of the two localities. The total exposed foundry population showed a significant decrease in FEV1 and FVC which indicates that the pollution in the workplace contributes to the development of restrictive lung disorders in foundry workers. The dust created during the welding of steel in the welding shop is a contributing agent in the development of obstructive respiratory disorders in the welder population. Examination of the relationship between elemental variations has allowed identification of several sources and activities contributing to airborne particles. The aerosol profiles did not show similar diurnal time variation patterns in the foundry or the welding shop due to irregularities in the continuation of the processes. The AIER for the foundry resulted in a maximum value of 92.3 % while the corresponding value for the welding environment was 71.7 %. The results present the worst case scenario during winter conditions and it is expected that conditions will be more healthy during summer time when windows and doors are open. The planning and prioritisation for the improvement of indoor air quality in both workplaces can proceed , using the data on the sources of the pollutants. It can be concluded that workers exposed to conditions as found during this project, will experience health problems after chronic exposure. The results emphasised the importance of exposure characterisation in order to provide for identification of pollutants, control of sources and the application of industrial hygiene principles for the protection of human health. It is recommended that all industries implement exposure characterisation programmes as a tool in applying good occupational and environmental hygiene