With recent advancements in additive manufacturing (AM) technology, it is possible to deposit copper conductive paths and insulation layers of an electric machine in a selective controlled manner. AM of copper enables higher fill factors that improves the internal thermal conduction in the stator core of the electric machine (induction motor), which will enhance its efficiency and power density. This will reduce the motor size and weight and make it more suitable for aerospace and electric vehicle applications, while reducing/eliminating the rare-earth dependency. The objective of this paper is to present the challenges associated with AM of copper coils having 1 × 1 mm cross section and complex features that are used in producing ultra-high efficiency induction motor for traction applications. The paper also proposes different approaches that were used by the authors in attempts to overcome those challenges. The results of the developed technologies illustrate the important of copper powder treatment to help in flowing the powder easier during deposition. In addition, the treated powder has higher resistance to surface oxidation, which led to a high reduction in porosity formation and improved the quality of the copper deposits. The laser powder direct energy deposition (LPDED) process modeling approach helps in optimizing the powder deposition path, the laser power, and feed rate that allow the production of porosity free thin wall and thin floor components. The laser powder bed fusion (LPBF) models identify the optimum process parameters that are used to produce test specimens with >90% density and minimum porosity.
With recent advancements in additive manufacturing (AM) technology, it is possible to deposit copper conductive paths and insulation layers of an electric machine in a selective controlled manner. AM of copper enables higher fill factors that improves the internal thermal conduction in the stator core of the electric machine (induction motor), which will enhance its efficiency and power density. This will reduce the motor size and weight and make it more suitable for aerospace and electric vehicle applications, while reducing / eliminating the rare-earth dependency. The objective of this paper is to present the challenges associated with AM of copper coils having 1×1mm cross section and complex features that are used in producing ultra-high efficiency induction motor for traction applications. The paper also proposes different approaches that were used by the authors in attempts to overcome those challenges.
The kinematics of the deep rolling tool, contact stress, and induced residual stress in the near-surface material of a flat Ti-6Al-4V alloy plate are numerically investigated. The deep rolling tool is under multiaxis nonlinear motion in the process. Unlike available deep rolling simulations in the open literature, the roller motion investigated in this study includes penetrative and slightly translational motions. A three-dimensional finite element model with dynamic explicit technique is developed to simulate the instantaneous complex roller motions during the deep rolling process. The initial motion of the rollers followed by the penetration motion to apply the load and perform the deep rolling process, the load releasing, and material recovery steps is sequentially simulated. This model is able to capture the transient characteristics of the kinematics on the roller and contacts between the roller and the plate due to variations of roller motion. The predictions show that the magnitude of roller reaction force in the penetration direction starts to decrease with time when the roller motion changes to the deep rolling step and the residual stress distributions in the near-surface material after the material recovery step varies considerably along the roller path.
Deep rolling process is a mechanical surface treatment that provides several advantages, such as low friction on the interface between the tool and workpiece in the process, controlled profile of induced compressive residual stress to enhance the HCF and LCF strength, enhancement of the stability of the near-surface structure at high temperature, and improvement of surface finish after the process. This paper investigates the deep rolling process under lubricated condition for a complex deep rolling path. A three-dimensional finite element model incorporating the strain hardening and strain rate effects on the material responses is developed to sequentially simulate the continuous multi-axis roller motion in the process. This model can capture the horizontal and normal forces acting on the roller so that a time-varying apparent coefficient of friction can be obtained. In addition, due to the complex roller path, the model also predicts a complex residual stress distribution in the near-surface material.
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