Abstract
In this thesis two aspects on rotors made from composite materials have been treated. The first major aspect is that due to centrifugal forces imperfection of thin-walled shafts will lead to changes in the geometry. This study shows that the change in the stiffness due to an imperfection has much greater influence than a change in the geometry. Imperfection of the types treated in here have largest influence when the filament winding angle is about 60 degrees. The only terms that largely influence the behaviour of a rotor in a Fourier Series expansion of the deformed contour due to an imperfection, are the three first. The second aspect is that for classical rotor materials the influence of material damping can mostly be neglected. For composites, however, the damping can be one to two orders of magnitude larger. This study shows how hysteretic material damping can be analyzed by using a viscous damping model, where the damping constant is depending on the frequency. An instability criterion for various conditions of shafts and bearings are given. It is shown that the combined effects of fluid film bearings and internal damping has to be taken under account in analyses of composite shafts mounted
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Citation Formats
Svensson, Haakan.
Dynamics of composite rotors, with special reference to influence of imperfections and internal damping.
Sweden: N. p.,
1993.
Web.
Svensson, Haakan.
Dynamics of composite rotors, with special reference to influence of imperfections and internal damping.
Sweden.
Svensson, Haakan.
1993.
"Dynamics of composite rotors, with special reference to influence of imperfections and internal damping."
Sweden.
@misc{etde_10117096,
title = {Dynamics of composite rotors, with special reference to influence of imperfections and internal damping}
author = {Svensson, Haakan}
abstractNote = {In this thesis two aspects on rotors made from composite materials have been treated. The first major aspect is that due to centrifugal forces imperfection of thin-walled shafts will lead to changes in the geometry. This study shows that the change in the stiffness due to an imperfection has much greater influence than a change in the geometry. Imperfection of the types treated in here have largest influence when the filament winding angle is about 60 degrees. The only terms that largely influence the behaviour of a rotor in a Fourier Series expansion of the deformed contour due to an imperfection, are the three first. The second aspect is that for classical rotor materials the influence of material damping can mostly be neglected. For composites, however, the damping can be one to two orders of magnitude larger. This study shows how hysteretic material damping can be analyzed by using a viscous damping model, where the damping constant is depending on the frequency. An instability criterion for various conditions of shafts and bearings are given. It is shown that the combined effects of fluid film bearings and internal damping has to be taken under account in analyses of composite shafts mounted on fluid film bearings. The material damping for a high-modulus carbon fiber in a epoxy resin has been investigated for different filament winding angles. the separate contributions on the damping from the stresses in the directions of the fibre, transverse to the fibres and in shear has been taken into account. Finally, this study shows that the optimal filament winding angle interval to get as low weight as possible for three different constraints, lateral eigenfrequency, maximum torque due to static stress and maximum torque due buckling, is in the same interval as the optimal filament winding angle to get as low dissipation energy as possible. 15 refs, 49 figs}
place = {Sweden}
year = {1993}
month = {Dec}
}
title = {Dynamics of composite rotors, with special reference to influence of imperfections and internal damping}
author = {Svensson, Haakan}
abstractNote = {In this thesis two aspects on rotors made from composite materials have been treated. The first major aspect is that due to centrifugal forces imperfection of thin-walled shafts will lead to changes in the geometry. This study shows that the change in the stiffness due to an imperfection has much greater influence than a change in the geometry. Imperfection of the types treated in here have largest influence when the filament winding angle is about 60 degrees. The only terms that largely influence the behaviour of a rotor in a Fourier Series expansion of the deformed contour due to an imperfection, are the three first. The second aspect is that for classical rotor materials the influence of material damping can mostly be neglected. For composites, however, the damping can be one to two orders of magnitude larger. This study shows how hysteretic material damping can be analyzed by using a viscous damping model, where the damping constant is depending on the frequency. An instability criterion for various conditions of shafts and bearings are given. It is shown that the combined effects of fluid film bearings and internal damping has to be taken under account in analyses of composite shafts mounted on fluid film bearings. The material damping for a high-modulus carbon fiber in a epoxy resin has been investigated for different filament winding angles. the separate contributions on the damping from the stresses in the directions of the fibre, transverse to the fibres and in shear has been taken into account. Finally, this study shows that the optimal filament winding angle interval to get as low weight as possible for three different constraints, lateral eigenfrequency, maximum torque due to static stress and maximum torque due buckling, is in the same interval as the optimal filament winding angle to get as low dissipation energy as possible. 15 refs, 49 figs}
place = {Sweden}
year = {1993}
month = {Dec}
}