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The provision of helical grooves on the surface of a plain journal bearing can improve the stability of a rotor-bearing system. However, the improvement depends on the arrangement of the grooves along the axial length of the bearing. In order to verify this improved stability three types of helical groove bearing and a reference plain journal bearing were investigated. The helical groove journal bearings were: a symmetrical, an asymmetrical and a partial grooved bearing. The bearing test rig was used to measure the oil flow rate, load carrying capacity, power losses, bearing surface temperatures, and stability characteristics. A theoretical model was developed to calculate the load carrying capacity, stiffness and damping coefficients, and stability characteristics of the various types of bearing. The experimental and theoretical results show that at the expense of a reduced load capacity the helical groove bearings are more stable particularly at low eccentricity ratios. However, the experimental observations showed that the partial helical groove bearing is not a practical bearing because the bearing becomes misaligned above certain load. For a given eccentricity ratio and speed the symmetrical bearing ran hotter and with greater power losses in comparison to the other three bearings. At the same eccentricity ratio and speed, the asymmetrical bearing ran at about the same temperature as the plain journal bearing.

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This thesis presents the results of an investigation of bearing failure at a loaded hole in carbon fibre composite laminates. The investigation included finite element analysis and a program of experimental testing for quasi-isotropic laminates, uni-directional laminates and laminates with fibres steered along predefined trajectories. The investigation formed part of a research program in the Cooperative Research Centre for Advanced Composite Structures Ltd (CRC-ACS) support by the Office of Naval Research from the United States. Work in progress in the CRC includes research defined in this thesis including the addition of nano-particles to the resin to improve the bearing strength. The literature survey undertaken in this thesis identified that the micro-buckling theory proposed by Professor C.T. Sun from Purdue University, Indiana USA, is the best analysis procedure for initial bearing failure in pin-loaded laminates. This failure theory has therefore been implemented in a Fortran program using the results from a finite element analysis for the nonlinear contact problem of a pin bearing on a hole in a composite laminate. The finite element analysis is executed using the commercial finite element system MSC.MARC. The numerical predictions have been validated by a test of progressive failure with the aid of an acoustic emission monitoring system. The acoustic emission parametric and frequency analysis is performed using the acoustic emission software Vallen Systeme. Fast fourier transformation of the waveform have been achieved to distinguish and identify microfailure mode. Failure mechanisms have been verified by post-mortem microstructural examination. There are 3 failure mechanisms associated with bearing failure in carbon fibre reinforced epoxy composite, the first is fibre matrix interfacial failure, followed by fibre fracture, and subsequently matrix splitting. The application of AE technique has been applied successfully to characterise the development of failure.

Thesis (M.S.)--Ohio State University, 1989. / Includes bibliographical references. Available online via OhioLINK's ETD Center

Thesis (M.S.)--Ohio University, June, 1993. / Title from PDF t.p.