| Shrnutí: | <p>The relationship between interfacial displacement and load for rough contacts is determined by the contact stiffness. The tangential contact stiffness for ground Ti-6Al-4V surfaces is measured to linearly decrease with the application of tangential load, approaching zero at slip. At the beginning of the application of tangential load, for ground surfaces, the ratio of the tangential contact stiffness to the normal contact stiffness is seen to be approximately half the Mindlin ratio, consistent with many other published experimental studies. Measurements of normal contact stiffness for ground surfaces conform to a model that posits a linear relationship between normal contact stiffness and normal load. An equivalent surface roughness parameter is defined for two surfaces in contact; and the normal contact stiffness for ground surfaces is observed to be inversely proportional to this parameter. These results indicate a straightforward means to estimate both normal and tangential contact stiffness at different loads for ground surfaces of known surface roughness.</p>
<br>
<p>Single asperity models were constructed to simulate the effect of different frictional laws and plasticity on the tangential displacement of an asperity contact. Further, multi-asperity modelling showed the effect of different normal load distributions on the tangential behaviour of interfaces. In addition, normal contact stiffness was modelled for a grid of asperities in which asperity interaction was permitted, i.e. displacement at an asperity was affected by the loading at all asperity contacts.</p>
<br>
<p>The second part of the thesis analyses plane receding contacts, assuming linear elasticity, and perfectly smooth interfaces with a friction law. Receding contacts, though ubiquitous in mechanical and structural components, such as in bolted joints, are difficult to model with conventional methods such as finite elements. One promising method of analysis is the distributed dislocation technique. However, current methods require the distribution of dislocations to be bounded to zero or singular at the ends of the area of application, which is not appropriate to model many receding contacts. A receding contact problem for which the required form of the distributed dislocations is bounded-
bounded was solved. Then, a fundamental 2D frictional receding contact problem involving a homogeneous linear elastic infinite layer pressed by a line load onto a half-plane of the same material was analysed. This was done by the insertion of preformed distributed dislocations (or eigenstrains), which take into account the correct form of the separation of the interface at points away from the area of loading, along with corrective bounded-bounded distributions. The general method of solution was further refined and adapted to solve three other receding contact problems. The solutions demonstrated the robustness and applicability of this new procedure.</p>
|
|---|