The principal aim of this thesis was to investigate the contact and deformation of rough surfaces such as those found on the teeth of gears. Freshly manufactured surfaces undergo a process known as “running-in”, in which the surface geometry is altered as a result of contact under load. Plastic deformation can occur which induces significant residual stresses, and it has been suggested that these may have implications for the subsequent fatigue life of the surfaces. In this thesis, finite element analysis (FEA) has been used to perform full elastic-plastic contact analysis based on profiles from gear teeth which are used in micropitting tests in order to determine the detailed nature of deformation and the magnitude and distribution of the residual stresses. FEA was performed using Abaqus, and the techniques were first developed using known contact problems of smooth elastic bodies. Plastic behaviour was subsequently introduced, guided by previous studies in the literature. Profiles from real surfaces were then used to study the behaviour of typical gear surfaces under load. Experiments were carried out in which the rough surfaces of crowned steel discs were loaded together, with relocated profiles taken before and after loading. The aim was to provide experimental verification of the residual deformations predicted by FEA. Good agreement was found between the analysis and experiments carried out at different loads. Regions of surface and subsurface residual tensile stress were predicted to occur in proximity to heavily loaded asperity contacts. Greater plastic deformation resulted in increased magnitudes of residual stress. Significant residual tensile stresses were predicted in regions where crack initiation has been shown to occur in practice at depths typical of micropitting failures in gears. It is concluded that residual effects of initial plastic deformation taking place during running-in can be a significant factor in micropitting failures in gears.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:590356 |
| Date | January 2013 |
| Creators | Bryant, Michael James |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/57302/ |
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