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Jönköping, Sweden

Mardan N.,Linkoping University | Klahr R.,Swerea SWECAST AB | Karlsson M.,Linkoping University
Proceedings of the 24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2011 | Year: 2011

In recent years, there has been a worldwide focus on the issue of energy because of increased energy prices and the threat of increasing global warming. Furthermore, industries are facing greater competition as a result of increasing globalisation, which is forcing companies to reduce their expenses. Reducing the use of energy is therefore an essential task for the future as it has a positive impact on both the environment and the profits of any business. Reductions in energy demand can be accomplished by different means, such as investments in energy-efficient processes or load management. Analytical tools may be used to support the decision-making process, when choosing between a number of measures, and analysing the results can help to choose which changes should be made. This paper studies two types of energy analysis tool: energy systems optimisation (ESO) and discrete event simulation (DES). The aim of this paper is to describe a method where a DES and an ESO tool are combined in order to study the potential energy and resource reduction in complex industrial energy systems. A case study representing a part of a dairy is also included to illustrate the use of the method. The system modelled includes a process where the durability or longevity of milk increases from a few days to 28 days by using steam injection. The results from the case study show that the dairy has much higher potential production capacity than realised today. This also means that there is a potential to reduce the operation hours from a three-shift to a two-shift operation to meet the existing weekly demand. The analysis also shows that there are large potential reductions in both energy and other resources. The largest potential reductions are primarily from electricity and water. The combination of tools increases the reliability of the analysis and facilitates decision making in an industrial site. Source

Dioszegi A.,Jonkoping University College | Fourlakidis V.,Swerea SWECAST AB | Svensson I.L.,Jonkoping University College
Materials Science Forum | Year: 2010

The fracture mechanism of gray cast iron was investigated on tension loaded samples produced under different conditions. The parameters studied included the graphite morphology, the carbon content, the inoculation and the cooling condition. The observations made reveal the role of the microstructure on crack propagation. The cracks were found to always propagate parallel with the graphite flakes. The interaction between the metallic matrix precipitated as primary austenite and graphite has been interpreted by a simplified model of the austenite reinforced eutectic cell. The geometrical transcription gave a standard crack component configuration with known mathematical solution. The microstructure observed in the experiments has been analysed by means of a novel interpretation. The fictitious stress intensity at yield and the fictitious maximum stress intensity at failure are strongly related to the relative shape of the eutectic cell and the fraction primary austenite. A different slope is observed for the material cooled at high rate when the precipitation of primary carbide reduces the stress intensity. The observed relations indicate that the tensile strength of the grey cast iron is the result of the collaboration between the toughness of the metallic matrix precipitated as primary austenite and the brittleness of the graphite phase. The shape and distribution of the primary austenite and graphite can be influenced by chemical composition, by inoculation or by the cooling condition, but they will maintain equilibrium with respect to the stress intensity. © (2010) Trans Tech Publications. Source

Bladh M.,Swerea SWECAST AB | Wessen M.,Jonkoping University College | Dahle A.K.,University of Queensland
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2010

Significant progress has been made in recent years in understanding and modelling the rheology of semi-solid metals. These models show the effects of the microstructure in terms of size and morphology of globules on the material response. More recently it has been shown that semi-solid metals can behave as compacted granular materials such as sand. A particular signature of such deformation is that the deformation becomes concentrated into shear bands which are 10-20 grains wide. Such bands have also been observed in a range of cast products. Recently, it has been clearly shown that shear bands in high pressure die cast (HPDC) products are also the results of Reynolds dilatancy. Shear bands are also known to be a common feature in semi-solid metal products. The segregation banding in semi-solid metal (SSM) material and its dependence of plunger velocity were investigated. Shaped castings were made with the RHEOMETAL™ process with a range of different plunger velocities. The microstructural characteristics were investigated, with a particular emphasis on shear bands. It is shown that ingate velocities influence the location and characteristics of the shear bands. © 2010 The Nonferrous Metals Society of China. Source

Sjogren T.,SP Technical Research Institute of Sweden | Sjogren T.,Jonkoping University College | Svensson H.,Swerea SWECAST AB
Key Engineering Materials | Year: 2011

In this experimental study, six pearlitic grey cast irons with different Cu and Cr content, different section thicknesses and different eutectoid cooling rates have been examined. The eutectoid cooling rate was approximated by casting simulation analysis. The purpose of the experiments was to study the effect of the matrix structure on the overall mechanical properties. An emphasis is put on the pearlite interlamellar spacing because this controls the resulting mechanical properties to a large extent. By keeping the graphite structure constant, the effect of the matrix structure was able to be studied. This was achieved by shake-out at temperatures above the eutectoid transformation range followed by subsequent cooling in air, mould or in a furnace. The pearlite interlamellar spacing ranged from 90 to 330 nm for the matrices studied. Comparing the strength of the fine structured and coarse structured materials, the tensile and yield strength was reduced by almost 50%. Regarding the elastic deformation, a weak increase in the tangent modulus with increasing alloying content was observed. It was also observed that lower cooling rate decreased the tangent modulus. The tangent modulus ranged between 70 and 110 GPa. Analysing the plastic deformation of the materials, in terms of strain hardening exponent, n, and strength coefficient, K, a strong dependence on the pearlite coarseness was observed. It was concluded that the effect of graphite particle length on tensile strength was negligible and the major improvement on the strength was due to refinement of the pearlite. Source

Svensson H.,Swerea SWECAST AB | Sjogren T.,SP Technical Research Institute of Sweden | Sjogren T.,Jonkoping University College
Key Engineering Materials | Year: 2011

The matrix structure formation of cast irons is strongly affected by the casting process where different alloying elements and cooling conditions are methods used to achieve the desired structure and performance of the material. In the presented study, six pearlitic grey cast irons have been analysed regarding how the pearlitic structure formation might be controlled. Different amounts of copper and chromium were added, ranging from 0.07 to 1.11 wt% and 0.08 to 0.60 wt%, respectively. Three different section sizes (Ø20, Ø45 and Ø85 mm) and three different cooling conditions through the eutectoid transformation were used to control the matrix structure formation. The three different cooling conditions were achieved by shake-out at 950°C and cooling in air or furnace, or by keeping the casting in the mould. The present paper focuses on the pearlite appearance, since it strongly affects the mechanical properties. The analysis shows that the refining effect of Cr is much stronger than that of Cu. Comparing the low alloyed base melt with the ones alloyed with Cu and Cr, it is seen that additions of 0.75 wt% Cu refines the pearlite by approximately 10%. Keeping this Cu level constant and adding Cr, it is observed that an addition of ∼0.6 wt% refines the pearlite by another 20%. The most potent refining effect of Cr is achieved by additions up to 0.35 wt%. Keeping the Cr constant at 0.35% and changing the Cu content (0.35 to 1.10 wt%), almost no variation is observed in the overall interlamellar spacing. The eutectoid cooling rate most strongly affects the interlamellar spacing down to cooling rates of about -0.75 °C/s. At higher (i.e. lower value) cooling rates the interlamellar spacing is fairly constant. In addition to studying the interlamellar spacing, the graphite structure has also been analysed and evaluated concerning effects from the different casting variables. Source

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