| 1. |
- Torkamani, Hadi, et al.
(författare)
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Effect of Rotation Speed and Steel Microstructure on Joint Formation in Friction Stir Spot Welding of Al Alloy to DP Steel
- 2022
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Ingår i: Journal of Manufacturing and Materials Processing. - : MDPI. - 2504-4494. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- In this work, friction stir spot welding of 5754 aluminum alloy to dual phase steel was investigated using two different ratios of martensite and ferrite (0.38 and 0.61) for steel sheet initial microstructure and varying tool rotation speed (800, 1200 and 2000 rpm). The effect of these parameters on the joint formation was evaluated by studying the plunging force response during the process and the main characteristics of the joint at (i) macrolevel, i.e., hook morphology and bond width, and (ii) microlevel, i.e., steel hook and sheet microstructure and intermetallic compounds. The plunging force was reduced by increased tool rotation speed while there was no significant effect from the initial steel microstructure ratio of martensite and ferrite on the plunging force. The macrostructural characterization of the joints showed that the hook morphology and bond width were affected by the steel sheet initial microstructures as well as by the tool rotation speed and by the material flow driver; tool pin or shoulder. At microstructural level, a progressive variation in the ratio of martensite and ferrite was observed for the steel hook and sheet microstructure. The zones closer to the tool presented a fully martensitic microstructure while the zones away from the tool showed a gradual increase in the ferrite amount until reaching the ratio of ferrite and martensite of the steel sheet initial microstructure. Different types of FexAly intermetallic compounds were found in three zones of the joint; the hook tips, in the hooks close to the exit hole and in the corner of the exit hole. These compounds were characterized by a brittle behavior with hardness values varying from 456 to 937 HV01.
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| 2. |
- Holmberg, Jonas, 1976-, et al.
(författare)
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Abrasive Water Jet Milling as An Efficient Manufacturing Method for Superalloy Gas Turbine Components
- 2022
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Ingår i: Journal of Manufacturing and Materials Processing. - : MDPI. - 2504-4494. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve efficiency when manufacturing gas turbine components, alternative machining techniques need to be explored. In this work, abrasive water jet (AWJ) machining by milling has been investigated as an alternative to traditional milling. Various test campaigns have been conducted to show different aspects of using AWJ milling for the machining of superalloys, such as alloy 718. The test campaigns span from studies of individual AWJ-milled tracks, multi-pass tracks, and the machining of larger components and features with complex geometry. In regard to material removal rates, these studies show that AWJ milling is able to compete with traditional semi/finish milling but may not reach as high an MRR as rough milling when machining in alloy 718. However, AWJ milling requires post-processing which decreases the total MRR. It has been shown that a strong advantage with AWJ milling is to manufacture difficult geometries such as narrow radii, holes, or sharp transitions with kept material removal rates and low impact on the surface integrity of the cut surface. Additionally, abrasive water jet machining (AWJM) offers a range of machining possibilities as it can alter between cutting through and milling. The surface integrity of the AWJM surface is also advantageous as it introduces compressive residual stress but may require post-processing to meet similar surface roughness levels as traditional milling and to remove unwanted AWJM particles from the machined surface. © 2022 by the authors.
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| 3. |
- Sridhar, Praveen, et al.
(författare)
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Modeling Grinding Processes-Mesh or Mesh-Free Methods, 2D or 3D Approach?
- 2022
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Ingår i: Journal of Manufacturing and Materials Processing. - : MDPI. - 2504-4494. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- The objectives of this study are mainly two: (1) to validate whether a single grain scratch process can be modeled in two dimensions under the assumption of plane strain, and (2) to select the best discretization approach to model a single grain scratch process. This paper first focuses on the simulation of the orthogonal cutting process (aluminum alloy A2024 T351) using two mesh-based discretization approaches, the pure Lagrangian method (LAG) and the arbitrary Lagrangian-Eulerian method (ALE), and two particle-based approaches, the particle finite element method (PFEM) and smooth particle hydrodynamics (SPH), for both positive and negative rake angles. Benchmarking of the orthogonal cutting models at a rake angle of gamma = 20 degrees is performed with the results of the process forces (cutting and passive forces) of a turning experiment from the literature. It is shown that all models are able to predict the cutting forces, but not the passive force. The orthogonal cutting model is further extended to simulate the cutting mechanism with negative rake tool geometries typically found in grinding and single grit scratching processes. The effects of the negative rake angles on the discretization approaches are studied. The calculated process forces are also compared to the measurements of the single grit scratch process performed at our laboratory. The 2D orthogonal cutting models significantly overestimate the process forces. One of the reasons why the orthogonal 2D cutting model is inadequate is that it cannot describe the complex mechanisms of material removal such as rubbing, plowing, and cutting. To account for these phenomena in LAG, ALE, and SPH discretization approaches, a 3D scratch model is developed. When comparing the process forces of the 3D model with the experimental measurements, all three discretization approaches show good agreement. However, it can be seen that the ALE model most closely matches the process forces with the experimental results. Finally, the ALE 3D scratch model was subjected to sensitivity analysis by changing the cutting speed, the depth of cut and the tool geometry. The results clearly show that the ALE method not only predicts the process forces and form the trends observed in the scratching experiments, but also predicts the scratch topography satisfactorily. Hence, we conclude that a 3D model is necessary to describe a scratch process and that the ALE method is the best discretization method.
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