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Kianfar, Sina

University of British Columbia

Next-generation internal combustion engines (ICEs) require advanced manufacturing technologies to fulfill efficiency regulations concerning automotive fuel consumption and emissions. This is commonly achieved by reducing the weight and/or increasing the operating pressure of ICEs. Most weight-reduction efforts have focused on replacing heavy ferrous alloys in powertrain components such as engine blocks with lightweight aluminum (Al) alloys. However, insufficient high-temperature strength and wear resistance restrict Al alloy’s applicability for engine blocks. Therefore, cast iron (Fe) liners are extensively used to protect the Al cylinder wall from wear. During the manufacturing of Al engine blocks with cast-in Fe liners, the thermal expansion coefficient mismatch between the Al cylinder wall and the Fe liners results in high residual stress evolution. This residual stress can surpass the Al alloy’s strength, causing the engine block’s distortion and/or premature failure under in-service loadings. Further, the cylinder bore distortion results in the engine’s efficiency and power loss, increasing fuel consumption and emissions. Hence, it is essential to predict the residual stress generation during the engine block manufacturing processes, i.e., casting and heat treatment. An in-depth understanding of residual stress evolution can assist in alleviating them, improving the engine block’s durability and the vehicle’s fuel efficiency. This research aims at developing a fundamental understanding of residual stress evolution during the manufacturing process of Al powertrain components. To do so, first, material characterization of the samples of interest was conducted in terms of microstructure, thermophysical, and mechanical properties at room and elevated temperatures. Then, destructive and non-destructive techniques were utilized for measuring residual stresses in the samples. Next, a novel FEM model of casting and heat treatment processes, with advanced temperature-dependent boundary conditions, was developed. The model was then utilized to investigate residual stresses in a stress-lattice casting, an inline-6 precision sand-cast engine block, and an inline-4 high-pressure die-cast engine block with cast-in Fe liners. Finally, the simulation results were compared with the experiment, and good agreement was found in most cases. The results of this research will assist the automotive industry in optimizing the next-generation ICEs with reduced residual stresses, leading to the production of high-efficiency, sustainable ICEs.

Text

2022-09-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82682

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/