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- Bövik, Peter, 1961, et al.
(författare)
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Autobalancing of Rotors
- 1986
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Ingår i: Journal of Sound and Vibration. ; 111, s. 429-440
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Tidskriftsartikel (refereegranskat)
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| 13. |
- Bövik, Peter, 1961
(författare)
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On the dynamics in an auto-balancing system
- 2017
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A simple symmetric physically realisable auto-balancing system with a six dimensional phase space is analysed and its dynamics is simulated. If the mass of the moving correction particle is obtaind from static balancing condition, then the system contains two fixed points where one is the balanced state and the other corresponds to a whirling motion of the rotor. By using numerical continuation techniques a bifurcation analysis of codimension one is performed, but some results for codimension two bifurcations are also shown. When the bifurcation parameter is equal to one the motion switches from subcritical to supercritical motion at a branch point where the two fixed points coincide and an exchange of stability occurs through a saddle-node bifurcation, but only in a very small interval of the parameter. Both fixed point becomes unstable through a subcritical Hopf bifurcation almost immediatley after the branch point, leading to a complicated dynamics for an interval of the bifurcation parameter. The balanced state then becomes stable through a supercritical Hopf bifurcation at the end of the interval where the system is in a supercritical motion. Numerical simulations reveal the complicated dynamics in the interval between the two Hopf points and calculation of the Lyapunov exponents and Poincar\'{e} maps shows that chaotic motions exists mixed with mode locking states with k-periodic orbits of different orders of k. Numerical bifurcation diagrams shows Feigenbaum routs of period doubling cascades to chaotic motion.
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- Bövik, Peter, 1961
(författare)
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Thin Layers in Elastic Wave Propagation -Effective Modelling and Diffraction
- 1992
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the present thesis, the interest is focussed on the problem of effective modelling of thin interface layers for applications in elastic wave scattering. The layers are considered to be thin compared with wavelengths involved and it is shown that when all effects to lowest order in the layer thickness are included, we get boundary conditions (BCs) which have a number of nice features, including the one of implying that no scattering occurs when the layer has material parameters identical to the ones in the matrix medium. The layers are replaced by a single surface of discontinuity for the field variables, and the discontinuities are specified in such a manner that the influence of the original layer is reproduced locally to within O(h^2), where h is the layer thickness. Layers of fairly general shape, but of constant thickness, are considered. The BCs obatined are more complicated than the simple spring contact BCs, but they have the obvious advantage of containing all effects to the order indicated. The approach is possible to use in conjunction with almost any method for solving scattering problems. In this thesis the developed approximation thechnique is used in solving some potentially useful canonical scattering problems by the Wienr-Hopf method. The problems considered are scattering of time-harmonic horisontally polarized shear waves from swmi-infinite planar elastic (both isotropic and anisotropic) layers, and diffraction of L-TV waves from a fluid layer extending from an open crack imbedded in an elastic medium. The solutions can be used as building blocks in a more extensive investigation of finite layers, using the Geometrical Theory of Diffraction (GTD).
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- Larsson, Lars, 1984, et al.
(författare)
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Integral equation method for evaluation of eddy-current impedance of a tilted, surface-breaking crack
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 114:19
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Tidskriftsartikel (refereegranskat)abstract
- An integral equation method for solving the eddy-current nondestructive evaluation problem for aflat, tilted, and surface-breaking crack in a conducting half-space is presented. The method involvesuse of a half-space Green’s tensor and the Bowler potential. This potential describes the jump in theelectric field over the crack and is expanded in basis functions related to the Chebyshev polynomials,being a more analytical approach than the commonly used boundary element method. In the method,the scatterer defines a transformation operator to be applied on the incoming field. This is practical insimulations of the eddy-current inspection where this operator is independent of the position of theprobe. The numerical calculations of the change in impedance due to the crack are compared to aFinite Element model of the problem and good agreement is found.
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- Wirdelius, Håkan, 1963, et al.
(författare)
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A model for ultrasonic NDE on defect detection
- 1995
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Ingår i: Proc. 13th Int. Conf. on NDE in the nuclear and pressure vessel industries. - 0871705486 ; , s. 237-243
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Konferensbidrag (refereegranskat)
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