| 1. |
- Fällström, Karl-Evert, et al.
(författare)
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Transient bending waves in plates studied by hologram interferometry
- 1989
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Ingår i: Experimental mechanics. - 0014-4851 .- 1741-2765. ; 29:4, s. 378-387
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Tidskriftsartikel (refereegranskat)abstract
- Propagating bending waves are studied in plates made of aluminum and wood. The waves are generated by the impact of a ballistic pendulum. Hologram interferometry, with a double pulsed ruby laser as the light source, is used to record the out of plane motion of the waves. Elliptic-like fringes visualize differences in wave speed for different directions in the anisotropic plate and circular ones are obtained for the isotropic plate. The experimental data for the isotropic plate compare favorably with analytical results derived from the Kirchhoff-plate equation with a point impact of finite duration. A similarity variable is found when starting conditions are modeled as a Dirac pulse in space and time, that brings new understanding to the importance of specific parameters for wave propagation in plates. A formal solution is obtained for a point force with an arbitrary time dependence. For times much larger than the contact time, the plate deflection is shown to be identical to that from a Dirac pulse applied at the mean contact time. A method for determining material parameters, and the mean contact time, from the interferograms is hence developed.
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| 2. |
- Wåhlin, Anders, et al.
(författare)
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Wave propagation in plates studied by pulsed hologram interferometry
- 1989
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Ingår i: The Sixth Meeting in Israel on Optical Engineering. - Bellingham, Wash : SPIE - International Society for Optical Engineering. ; , s. 146-53
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Konferensbidrag (refereegranskat)abstract
- Isotropic and non-isotropic plates are impacted by a ballistic pendulum. The bending waves that are generated are studied with holographic interferometry using a double pulsed ruby laser as light source. The pulse shape changes with time because of the dispersivity of the waves. Initially the fringe pattern in the isotropic case is cylindrically symmetric and determined from an initial value problem. Later, when the waves have reached the plate rim, in- and outgoing waves gradually develop fringe patterns which in the end will be a combination of eigenmodes of the plate. A solution to the corresponding Kirchhoff plate equation is presented, which in the special case when the impact is modelled as a Dirac-pulse in space and time, is shown to depend only of the distance to the impact point divided by the square root of the time after impact and a parameter containing plate parameters. From the slope of the central deflection material parameters can be determined. Another solution, assuming a finite impact time, is shown to agree better with experiments. Results from investigations of non-isotropic materials are also presented.
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| 3. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Problems of optimizing of structures and laws of control of the motion of electromechanical manipulators
- 1987
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Ingår i: Soviet journal of computer and systems sciences. - 0882-4002. ; 25:6, s. 103-112
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Tidskriftsartikel (refereegranskat)abstract
- A number of problems of optimizing the structural parameters and control laws aimed at minimizing the manipulator mass, the energy expenditures, and the maximum power of the electric motors, are formulated and solved within the framework of a mathematical model of an electromechanical manipulator that takes into account the distributed elasticity of an extended link. A formalization method is developed and an algorithm for solving the problem of the mathematical design of an optimal manipulator is proposed. The effect of the values of the moment of the electromagnetic forces at the initial and final instants of the control process on the kinematic and dynamic characteristics of the controlled motions of an elastic electromechanical manipulator is investigated.
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| 4. |
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| 5. |
- Östlund, Sören, et al.
(författare)
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Asymptotic crack tip fields for dynamic fracture of linear strain-hardening solids
- 1988
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 24:11, s. 1141-1158
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Tidskriftsartikel (refereegranskat)abstract
- Asymptotic crack tip fields, for dynamic crack propagation in an elastic-plastic material, have been calculated. The material is characterized by J2flow theory with linear-strain hardening. The possibility of plastic reloading on the crack flank is taken into account. Numerical results for the strength of the crack tip singularity, the angular positions of elastic unloading and possible plastic reloading regions, and the angular variation of the stress and velocity fields, are presented as functions of the crack tip speed and the ratio between tangent modulus and elastic modulus. Calculations have been performed for crack tip speeds below a certain limit velocity which depends on the tangent modulus and the loading conditions. The different loading modes which have been studied are modes I and II (plane strain and plane stress) and mode III (antiplane strain).
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| 6. |
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| 7. |
- Sundin, Karl-Gustaf, et al.
(författare)
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A stiff and compact impact-force transducer based on strain measurement
- 1985
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Ingår i: Experimental mechanics. - 0014-4851 .- 1741-2765. ; 25:1, s. 48-53
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Tidskriftsartikel (refereegranskat)abstract
- A stiff and compact transducer for both static and impact compressive forces has been developed. The principle of the transducer is based on measurement of tangential strain around the periphery of an axially loaded short and axisymmetric body. It is shown that for an appropriate choice of transducer geometry the output is nearly insensitive to the distribution of the force over the loaded surface. In an experimental investigation, a prototype of the transducer was subjected to both static and impact loads of different distributions. The results show only a few percent variation in transducer sensitivity for the load distributions used. The transducer consists essentially of a homogeneous body and is simple to make. The size and material can be chosen to fit special applications
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| 8. |
- Sundin, Karl-Gustaf, et al.
(författare)
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Force transducer based on measurement of mean strain in a compact body
- 1989
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Ingår i: Journal of Strain Analysis for Engineering Design. - 0309-3247 .- 2041-3130. ; 24:1, s. 31-35
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Tidskriftsartikel (refereegranskat)abstract
- A force transducer based on measurement of mean strain in a body has been developed. The transducer can be made stiff and compact and is therefore suitable for measurement of impact forces as well as static forces. An experimental test of a simple first prototype was performed using both static and impact loads with different distributions over the load-carrying area of the transducer. The results of the experiments show that the requirement of insensitivity to differences in load distribution is acceptably fulfilled. Improvements are expected to be possible if the transducer is made in a more accurate way.
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| 9. |
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| 10. |
- Boström, Anders E, 1951, et al.
(författare)
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Elastodynamic scattering from inclusions with thin interface layers
- 1988
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Ingår i: Wave Propagation in Structural Composites AMD Vol. 90; Proceedings of the Joint ASME/SES Applied Mechanics and Engineering Sciences Conference, June 20-22, 1988. ; , s. 109-116
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Konferensbidrag (refereegranskat)
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