Several major algorithmic and modelling aspects of the discrete element method are presented, with particular effort made to establish a general framework for the combined finite/discrete element simulation of shot peening and peen forming processes. On the basis of a general review of the contact detection algorithms, the alternating digital tree (ADT) and the augmented spatial digital tree (ASDT) are presented as examples of tree based search algorithms; whilst the dynamic cell based search algorithm is presented as an example of cell/grid based search algorithms. Extensive numerical tests are provided to compare the performance of the approaches discussed and to perform a parametric study of the dynamic cell algorithm. Contact resolution for circular and spherical discrete objects is comprehensively discussed. Following the establishment of geometric relations between contact pairs, four interaction laws for the normal contact are reviewed, together with a general analysis of the equivalence between them. A modified classic Coulomb friction model is proposed for 3D contact problems, and a new time stepping scheme is developed to ensure both short and long term stability of the contact models. In addition, two different schemes that incorporate energy dissipation into the contact model are reviewed. A new approach is proposed for contact resolution of 2D superquadrics. An advancing front technique based algorithm is described to generate a random packing of disks, ellipses and polygons; whereas a geometric based compression algorithm is developed to generate a random packing of spheres of various sizes within a geometric domain. A general algorithmic framework is established for the combined finite/discrete element analysis of shot peening processes, particularly for the evaluation and comparison of several interaction laws governing the contact between shot and workpiece. The proposed model is also verified with the experiments conducted elsewhere. A two stage combined finite/discrete element and explicit/implicit solution procedure for the simulation of peen forming process is developed, and verified with experiments.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637214 |
| Date | January 2004 |
| Creators | Han, Kuanjin |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://cronfa.swan.ac.uk/Record/cronfa42687 |
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