Dynamics of ship-ice interaction

Analysis of the ship-ice interaction problem using finite element method is presented in this report to determine the failure loads and the total stress and deformation states developed in the ice-field during the interaction process. The ice sheet is discretized using 20-noded three-dimensional finite elements and the failure in ice is described by Tsai-Wu criterion.NRC publication: Ye

Dynamic Response of Tubular T-Joints Under the Influence of Propagating Cracks

This paper presents an analytical study on the vibration response of tubular T-joint

Modeling and Calibration for Crack Detection in Circular Shafts Supported on Bearings Using Lateral and Torsional Vibration Measurements

In this paper the requisite foundational numerical and experimental investigations that are carried out, to model the “uncracked and cracked” shaft and to identify its bending and torsional vibration responses, are reported. The cylindrical shaft used in this experimental study is continuous over two spans (with a cantilever span carrying a propeller) with ball-bearing supports. During modal tests the backward end of shaft (away from the propeller end and connecting it to an electric motor, required for online monitoring) is fixed to one of the test frame supports; later on this backward end will be connected to an electric motor to carry out online modal monitoring for crack identification. In the numerical study, beam elements are used for modeling the bending and torsional vibrations of the rotating shaft. The paper describes in detail the numerical “linear spring” models developed for representing the effects of “ball bearings and the (experimental test) frame supports” on the vibration frequencies. Shaft response parameters are obtained using modal analysis software, LMS Test Lab, for bending vibrations monitored using accelerometers, and three “sets” of shear strain gages fixed at three different shaft locations measure the torsional vibrations. Effects of different crack depths on bending and torsional frequencies and mode shapes are investigated experimentally and numerically, and the results interpreted to give better comprehension of its vibratory behavior

Dynamics of ship/ice interaction

Analysis of the ship-ice interaction problem using finite element method helps us to determine the failure loads and the total stress and deformation states developed in the icefield during the interaction process. The mechanism of the interaction process which was mathematically formulated as a contact process with experimentally determined contact coefficients has been numerically solved and the induced loads computed.NRC publication: Ye

Effect of induced damping on the near resonant responses of a deep water tripod tower platform

Near-resonant responses of a deepwater platform to wave excitation are controlled by inducing additional hydrodynamic damping in the system. The study used a device designed to induce flow-separation around a vertical column at low Kc numbers. The results of two experimental investigations are presented in this paper. In the first experiment, in-line forces on a 0.3m diameter vertical cylinder were measured without and with the attachment of the flow-separation device. At low Kc numbers the drag coefficients increased by five times due to the attached device to the cylinder, whereas the inertial coefficients were found to be insensitive to the device. The second experiment investigated the wave induced responses of a 8.6m high hydroelastic model of a deepwater tripod tower platform in a 200x12x7m wave tank. A significant reduction in responses at and close to resonance, due to the induced drag damping, observed in the experimental measurements shows that the device is very effective for damping applications. The experimental findings are also supported by analytical results.Peer reviewed: YesNRC publication: Ye