1,720,977 research outputs found
Simultaneous Effect of Plunger Motion Profile, Pressure, and Temperature on the Quality of High-Pressure Die-Cast Aluminum Alloys
No full textHigh-pressure die casting has been used widely to manufacture a large variety of products with high dimensional accuracy and productivity. Although this process has a considerably lower cycle time than the other metal forming processes, it is not yet optimized, due to the complexity of the process and the number of parameters to be controlled. Hence, the identification of the parameters affecting quality of castings is the current challenge toward efficient and effective production. In their previous work, the authors proposed and validated some novel kinematic parameters of the plunger, which explain and forecast both the static mechanical properties and the internal quality of castings. The present work extends such an approach by including two other meaningful parameters, which describe the effect of upset pressure and temperature on the final outcome. These parameters are here formulated and have been validated by means of a statistically significant sample manufactured with different plunger motion profiles, upset pressures, and temperatures of the melt and die. The quality of the castings was assessed through static mechanical properties and density measurements. As further proof, internal defects were analyzed on the fracture surfaces of some meaningful castings
Process parameters affecting quality of high-pressure die-cast Al-Si alloy
No full textIn the last years, aluminium alloys have become more and more relevant because of their low density, coupled with good mechanical and corrosion properties. Different processes are available for the production of aluminium alloy components, but a very significant role is played by foundry processes. However, defects and imperfections are physiologically generated by foundry techniques, as a result of the process itself, of the alloy properties and of the die design. Particularly, high-pressure die-casting (HPDC) is considered a “defect generating process”, since an average of 5 - 10 % scrap is typically generated by this process. Several process parameters need to be controlled in order to obtain sound and reliable castings. Among the different process variables, the determination and control of the injection parameters remain a key requirement throughout the HPDC process. In this work, a statistically significant sample of castings in AlSi9Cu3(Fe) alloy has been manufactured through different injection parameters in order to identify the most relevant process parameters and estimate their correlations with the quality of the casting. In particular, the plunger I and II phase velocities (v1 and v2), the switch point between two phases (SW) and the intensification pressure (IP) have been varied randomly in accordance to the Design of Experiment methodology. The static mechanical properties of the castings have been measured using the bending test. Furthermore, the castings have been analysed by X-rays and their percentage of porosity has been estimated by means of image analysis software. Some novel aggregate parameters, representing a measure of the mechanical energy related to the plunger motion and the thermal energy exchanged with the die have been extracted from the plunger displacement curves and from thermocouple signals. The application of statistical concepts, methods and models demonstrates that these novel parameters allow explaining and forecasting both the mechanical properties and the porosity, and therefore the overall quality of the castings
A tool for predicting the effect of the plunger motion profile on the static properties of aluminium high pressure die cast components
Full text linkThe availability of tools for predicting quality in high pressure die casting is a challenging issue since a large amount of defects is detected in components with a consequent worsening of the mechanical behavior. In this paper, a tool for predicting the effect of the plunger motion on the properties of high pressure die cast aluminum alloys is explained and applied, by demonstrating its effectiveness. A comparison between two experiments executed through different cold chamber machines and the same geometry of the die and slightly different chemical compositions of the alloy is described. The effectiveness of the model is proved by showing the agreement between the prediction bounds and the measured data. The prediction model proposed is a general methodology independent of the machine and accounts for the effects of geometry and alloy through its coefficients
Approccio ecotossicologico allo sviluppo e applicazione di un sistema informativo territoriale del pericolo industriale
No full textCorrelation between process, microstructure and properties in high pressure die casting aluminium-silicon alloys
No full textNowadays automotive industry and, in general, transportation one increasingly needs light components in order to reduce total weights and therefore limit harmful emissions and fuel consumption. The die casting process, on one hand, is a versatile and highly productive process but, on the other, the elevated amount of defects found in the castings sometimes compromises the characteristics of the final product. This paper presents the results of the analyses carried out using a Reference Die, referred to as horse shoe-shaped die, specifically designed to generate as many kinds of defects as possible, at different levels of severity. A Design of Experiments method has been applied for analysing the influence of the main process parameters on the casting quality and an innovative sensor network installed on the machine allowed a continuous control of the process itself. Visual inspection, X-ray investigations and micrograph analyses have been carried out in order to assess the casting quality. Correlations between process parameters and casting quality have been deduced analysing the data collected through the equipment installed on the die casting machine: in-cavity sensor network, plunger speed and displacement sensors. Results show the effectiveness of the horse shoe-shaped casting in highlighting the correlations between process and quality and the strong influence of second phase plunger velocity, temperature and pressure on defect formation
Dabase project for environmentl impact evaluation of productive activities in a densiily populated area
No full textWEP/19
Correlations between defect content, mechanical properties and fractographic investigation of AISi9Cu3(Fe) alloy reference castings
No full textHigh Pressure Die Casting (HPDC) is a foundry process particularly suitable for high production rates and applied in several industrial fields, but the amount of scrap, caused by defects or incomplete filling, is sometimes very high. Thus it is important to know which are the main causes of defect formation and their effects on microstructure and mechanical properties. This paper presents, within the European MUSIC project, the qualitative and quantitative results of a study conducted on AlSi9Cu3(Fe) alloy castings, referred to as Horse-shoe Reference Castings, specifically designed to generate different kinds of defects with different severity levels. The work focuses on the correlations obtained between the casting mechanical properties, their defect content in terms of porosity and oxide films and the process parameters adopted, mainly second phase plunger velocity and intensification pressure. The three point bending test was carried out on the four specimens obtained from the two appendixes of the casting. The fracture surfaces were studied by scanning electron microscopy (SEM) and optical microscopy (OM) highlighting that the defect content is clearly correlated to the mechanical properties and the process parameter settings
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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