| 1. |
- Chapko, R., et al.
(författare)
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Numerical solution of parabolic Cauchy problems in planar corner domains
- 2014
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Ingår i: Mathematics and Computers in Simulation. - : Elsevier. - 0378-4754 .- 1872-7166. ; 101, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- An iterative method for the parabolic Cauchy problem in planar domains having a finite number of corners is implemented based on boundary integral equations. At each iteration, mixed well-posed problems are solved for the same parabolic operator. The presence of corner points renders singularities of the solutions to these mixed problems, and this is handled with the use of weight functions together with, in the numerical implementation, mesh grading near the corners. The mixed problems are reformulated in terms of boundary integrals obtained via discretization of the time-derivative to obtain an elliptic system of partial differential equations. To numerically solve these integral equations a Nystrom method with super-algebraic convergence order is employed. Numerical results are presented showing the feasibility of the proposed approach.
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| 2. |
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| 3. |
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| 4. |
- Peng, Ru, et al.
(författare)
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Influence of Dry Cut and Tool Wear on Residual Stresses in High Speed Machining of Nickel-Based Superalloy
- 2014
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Konferensbidrag (refereegranskat)abstract
- Machining induced residual stresses were investigated in Inconel 718 prepared by high speed turning under dry cut condition. The influence of cutting tool wear and the use of cutting fluid were studied. By x-ray diffraction measurements, characteristic residual stress distributions with tensile stresses in the top layer and compressive stresses in the layer below were found in all the investigated samples. The magnitude of surface tensile stresses and size of the tension as well as compression zones varied depending on the cutting condition. The application of cutting fluid for turning using new tool has a minor effect, giving a somewhat larger subsurface compressive zone but reducing the surface tensile stresses. Tool flank wear has shown a much stronger effect. While a flank wear of VBmax=0.15 mm enhanced mostly the surface tensile residual stresses, a severer wear of VBmax=0.3 mm greatly increased the thickness of the subsurface compression zone and at the same time resulted in strong stress anisotropy. Microstructural study by electron channelling contrast imaging shows that the observed influence of tool flank wear or cutting fluid on residual stresses are related to different contributions from increased plastic deformation and cutting heat, which changed with the cutting conditions.
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| 5. |
- Peng, Ru, et al.
(författare)
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Residual Stresses in High Speed Turning of Nickel-Based Superalloy
- 2014
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Ingår i: HTM Journal of Heat Treatment and Materials. - : Carl Hanser Verlag GmbH. - 1867-2493 .- 2194-1831. ; 69:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- Residual stresses induced by machining operations can be critical for the performance and lifetime of the machined components. This paper investigated the influence of cutting conditions, including the use of cutting fluid, cutting speed and tool flank wear, on the residual stresses in high speed turning of Inconel 718 alloy. X-ray diffraction measurements revealed characteristic residual stress distributions with tensile stresses in a thin surface layer and compressive stresses in a much thicker subsurface layer in all investigated samples. However, the magnitude of the surface tensile stresses and subsurface compressive stresses as well as the size of the tension and compression zone depended on the cutting parameters. Surface tensile residual stresses over 1600 MPa and 1400 MPa were induced by tool flank wear and increased cutting speed, respectively, in dry turning. The effect of cutting induced local plasticity and temperature increase on the observed residual stress distributions was analyzed based on microstructural study by electron channeling contrast imaging and electron backscatter diffraction
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| 6. |
- Prilepsky, Jaroslaw E., et al.
(författare)
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Discrete solitons in coupled active lasing cavities
- 2012
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 37:22, s. 4600-4602
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Tidskriftsartikel (refereegranskat)abstract
- We examine the existence and stability of discrete spatial solitons in coupled nonlinear lasing cavities (waveguide resonators), addressing the case of active defocusing media, where the gain exceeds damping in the low-amplitude limit. A new family of stable localized structures is found: these are bright and gray cavity solitons representing the connections between homogeneous and inhomogeneous states. Solitons of this type can be controlled by discrete diffraction and are stable when the bistability of homogenous states is absent.
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| 7. |
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