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Simulating and Modelling Local Material Performance of High Pressure Die Cast components: Influence of Microstructure and Porosity on the Local Mechanical Properties of the Aluminum High Pressure Die Cast Components
Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH, Product Development.
2018 (English)Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
Abstract [en]

The automotive industry constantly strives to achieve better performance and reduce emissions by reducing the fuel consumption. This trend is now seen in all genres of vehicles as manufacturers throughout the world find innovative solutions to achieve the intended goal. Scania CV AB is one of the world’s leading commercial vehicle manufacturers based in Sweden. The intensions of reducing the weight of the individual components while not jeopardizing their functionality has been a vital area of research. The company along with the Materials and Manufacturing Department at Jönköping University aim to better understand the influence of local material properties of High Pressure Die Cast (HPDC) aluminum components.While designing a component during the development stage, traditionally, is defined with a homogeneous material property which is far from the reality. A casting comprises of variation and complexities in the geometry which lead to variations in solidification times and in turn causes local variations in microstructure and mechanical properties.The thesis work presented aims at better understanding of the casting process and its effects on the local material properties. The component under study is the oil cooler cover used in engines which was supplied by Scania. Casting simulations were performed to understand the geometric influence on the casting. Tensile specimens were extracted from different positions of the component and tested. Directional solidification technique was used to understand the potential of the alloy under study. Model equations were formulated to define the relation between secondary dendrite arm spacing (SDAS) and Hollomon parameters by regression analysis of tensile data from directional solidified samples. These were then used to compare the results obtained from the tensile tests of as-cast samples along with setting up FE analysis to simulate the tensile tests. Digital image correlation (DIC) tests were performed on as-cast samples to understand the local variations in tensile properties due to porosity. The works mentioned above were performed using the workshop facility, computer software and lab equipment at Jönköping University and radiography test facility at Scania CV AB, Södertälje.The results showed that changes in the microstructure influences the tensile behaviour of the material such Hollomon parameters. The variations in ultimate tensile stress (UTS), elongation and Hollomon parameters were significant in the case of directional solidified samples. The predicted Hollomon parameters from the model equations were within the range of standard deviations seen in the case of as-cast samples. However, it was observed that the variations in the UTS, elongation and Hollomon parameters from as-cast samples were not very significant. The SDAS from simplified casting simulation of the component provided a good match with the measured SDAS from as-cast samples. The results from simulation strategy provided good fit with the experimental results. The radiography test of the as-cast samples showed porosities from some of the areas which were depicted as hotspots in the casting simulations. DIC test was performed on the samples with porosities and was found that the strain and deformations was higher in the areas with porosities when compared to non-faulty areas confirming the local variations in strain due to porosities.Despite the variations in mechanical properties observed in the case of directional solidified samples, the variation in the cast component was not seen to be compelling. This can be due to the small variations in the cooling rates due to the HPDC process. Porosities however was seen to have significant effect on local mechanical properties which was observed in the DIC tests. Considering local variations and utilizing simulation strategy can be helpful in developing optimized components resulting in reduced material usage, reduction in weight, low fuel consumptions ultimately benefiting the economy and environment.

Place, publisher, year, edition, pages
2018.
Keywords [en]
Aluminum, HPDC, local material properties, Hollomon Equations, DOE, casting simulation, Finite Element Analysis (FEA), material testing, elasto-plastic behavior, Digital Image Correlation (DIC)
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:hj:diva-42757ISRN: JU-JTH-PRU-2-20190118OAI: oai:DiVA.org:hj-42757DiVA, id: diva2:1282719
External cooperation
Scania CV AB
Subject / course
JTH, Product Development
Supervisors
Examiners
Available from: 2019-01-28 Created: 2019-01-25 Last updated: 2019-01-28Bibliographically approved

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