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| 2. |
- Bahbou, M. Fouzi, 1973-, et al.
(författare)
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On-Line measurement of plasma-sprayed ni-particles during impact on a ti-surface : influence of surface oxidation
- 2007
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 16:6, s. 506-511
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to analyze the impact of plasma-sprayed Ni5%Al particles on polished and grit-blasted Ti6Al4V samples under oxidized and nonoxidized conditions. For this purpose, measurements of thermal radiation and velocity of individual plasma-sprayed particles were carried out. From the thermal radiation at impact, splat diameter during flattening and temperature evolution during cooling were evaluated. Characteristic parameters related to the quality of contact between the splat and the substrate were retrieved. The flattening speed was introduced to characterize wetting, while the cooling rate was used to characterize solidification. The idea was to get a signature of particle impact for a given surface roughness and oxidation state by identifying parameters which strongly affect the splat behavior. Sieved Ni5%Al powder in a narrow range (+65 −75 μm) was sprayed on four sets of titanium alloy surfaces, consisting of polished and grit-blasted samples, one set had a nonoxidized surface and the other one was oxidized in an oven at 600 °C for two hours. Resulting splats after impact were characterized by scanning electron microscopy, the splats on oxidized surface showed pores in their core and detached fingers at the periphery. The cooling rate and flattening degree significantly increased on the oxidized smooth surface compared to the nonoxidized one. This trend was not found in grit-blasted surfaces, which implies that impact phenomena are different on grit-blasted surfaces than on smooth surfaces thus further work is needed.
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| 3. |
- Bahbou, M. Fouzi, 1973-, et al.
(författare)
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Relationship between surface topgraphy parameters and adhesion strength for plasma spraying
- 2005
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Ingår i: ITSC 2005. - : The Material Information Society. ; , s. 1027-1031
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Konferensbidrag (refereegranskat)abstract
- To achieve sufficient adhesion strength within thermal spraying, the surface to be coated has to be modified. Grit blasting is the most common way to generate a clean and roughened surface. The bonding mechanism between the grit-blasted substrate and the coating is assumed to be due to mechanical anchoring, why an optimal surface roughness is essential. The surface roughness is usually evaluated using Ra which cannot fully characterize the complex nature of the chaotic substrate topography. This study was performed in order to evaluate if Ra can be replaced by other surface characteristic parameters such us R.q, Rpk, Rpv, Rk…with higher correlation to adhesion strength. Average roughness was measured by a perthometer and with white light interferometry to get 3D images of the surface topography. Disc shaped substrate samples of Ti6Al4V (AMS 4928) were grit blasted with aluminium oxide grit and plasma sprayed with a Ni5%Al coating. Adhesion strength was determined according to the ASTM C633 standard. The correlation between a number of different surface-parameters and adhesion strength were evaluated and compared with Ra.
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| 4. |
- Ericsson, Mikael, 1975-, et al.
(författare)
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A look at the optimization of robot welding speed based on process modelling
- 2007
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Ingår i: Welding Journal. - 0043-2296. ; 86:8, s. 238-244
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Tidskriftsartikel (refereegranskat)abstract
- Simulation tools to search for optimal process parameters are of great interest to reduce the number of experiments and thereby reduce cost and production time. In this paper, robot simulation has been used in combination with finite element simulations to optimize robot speed in order to minimize distortion while keeping complete joint penetration. In an earlier work performed by the authors, a finite element model was developed to predict heat transfer and residual stresses of parts with complex shapes. An interface between a robot simulation model and a finite element analysis model was also constructed. In this paper, an iterative method for robot speed optimization has been developed using MATLAB. The algorithm is designed to maintain complete joint penetration while maximizing productivity by utilizing the fastest weld speed. The method makes it possible to optimize the heat input to the component and thereby minimize component deformation for parts with complex shapes. The system was evaluated on stainless steel plates with varying thicknesses. Robot weld paths were defined off line and automatically downloaded to the finite element software where the optimization was performed. Simulations and experimental validations are presented.
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| 5. |
- Ericsson, Mikael, 1975-, et al.
(författare)
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Off-line programming of robots for metal deposition
- 2005
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Ingår i: Trends in welding research. - 0871708426 ; , s. 629-634
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Metal Deposition (MD) is a rapid prototyping technique to build parts by depositing metal in a required fashion. When a complex-shaped part is to be built, a simulation tool is needed to define robot trajectories. Three different simulation-based methods for robot trajectory generation are introduced and compared in this study. The methods are; reversed milling, adapted rapid prototyping and application programming in a computer aided robotics software. All methods were shown capable of creating robot paths for complex shapes, with the CAR software approach being the most flexible. Using this method, the geometry to be built is automatically sliced into layers and a robot path is automatically generated. The method was tentatively evaluated and appears to provide a powerful technique in the design and optimisation of robot paths for MD. Experiments showed that it is possible to manufacture fully dense parts using an Nd-Yag laser.
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| 6. |
- Ericsson, Mikael, 1975-, et al.
(författare)
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Three dimensional simulation of robot path, heat transfer and residual stresses of a welded part with complex geometry
- 2005
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Ingår i: International jourrnal for the joining of materials. - 0905-6866. ; 17:2, s. 42-51
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Tidskriftsartikel (refereegranskat)abstract
- In this article a simulation system is presented that combines computer aided robotics software used to define the welding operation, with a finite element model that predicts temperature-time histories and residual stress distributions for welding applications. The objective is to develop a tool for engineering processes in which robot trajectories and welding process parameters can be optimized off-line on parts with complex geometries. The system was evaluated on a stainless steel gas turbine component. Temperature dependent properties and phase change were included in the analysis. The turbine component was welded using an in-house TIG welding cell. The assumptions and principles that underpin the modeling techniques are presented together with predicted temperature histories, residual stresses, and fixture forces. Predicted residual stresses were compared with neutron diffraction measurements.
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| 7. |
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| 8. |
- Fasth, Angelica, et al.
(författare)
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A comparative study of mechanical properties between HVOF-sprayed Maxphase materials
- 2009
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Ingår i: Proceedings of the 22nd International Conference on Surface Modification Techniques. - 9780981706511 ; , s. 149-156
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Konferensbidrag (refereegranskat)abstract
- Mn+1AXn –phases (MAX-phase materials) are ternary compounds consisting of an early transition metal (M), such as Ti or V, a p-element from group III-V (A) and C and/or N (X). The phases have a layered structure in which the A element form planes separated by MX slabs. This nanolaminated atomic arrangement gives rise to a unique set of properties. These properties in combination with a good match in thermal expansion between substrate and coating make MAX-phase materials challenging materials to extend the lifetime of thermal barrier coatings. Evaluation of properties of HVOF sprayed MAX-phase materials and to compare these properties with commercially used bond coat materials such as MCrAlY coatings is thus of great interest which was the aim of this study.The non-linear load displacement relationships and Young’s modulus for HVOF-sprayed Ti2AlC coatings and APSsprayed NiCoCrAlY coatings onto Hastalloy X substrates were determined using data from both Berkovich andspherical microindentation. Results between Berkovich and spherical microindentation measurements are comparedand discussed.
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| 9. |
- Jiang, Janna, 1978-, et al.
(författare)
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Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY
- 2009
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Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 18:2, s. 194-200
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Tidskriftsartikel (refereegranskat)abstract
- Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.
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| 10. |
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