Experimental And Numerical Study Of Single And Multiple Imapcts Of Angular particles On Ductile Metals
thesisposted on 24.05.2021, 11:14 authored by Mahdi Takaffoli
Solid particle erosion occurs when small high speed particles impact surfaces. It can be either destructive such as in the erosion of oil pipelines by corrosion byproducts, or constructive such as in abrasive jet machining processes. Two dimensional finite element (FE) models of single rhomboid particles impact on a copper target were developed using two different techniques to deal with the problem of element distortion: (i) element deletion, and (ii) remeshing. It was found that the chip formation and the material pile-up, two phenomena that cannot be simulated using a previously developed rigid-plastic model, could be simulated using the FE models, resulting in a good agreement with experiments performed using a gas gun. However, remeshing in conjunction with a failure model caused numerical instabilities. The element deletion approach also induced errors in mass loss due to the removal of distorted elements. To address the limitations of the FE approach, smoothed particle hydrodynamics (SPH) which can better accommodate large deformations, was used in the simulation of the impact of single rhomboid particles on an aluminum alloy target. With appropriate constitutive and failure parameters, SPH was demonstrated to be suitable for simulating all of the relevant damage phenomena observed during impact experiments. A new methodology was developed for generating realistic three dimensional particle geometries based on measurements of the size and shape parameter distributions for a sample of 150 µm nominal diameter angular aluminum oxide powder. The FE models of these generated particles were implemented in a SPH/FE model to simulate non-overlapping particle impacts. It was shown that the simulated particles produced distributions of crater and crater lip dimensions that agreed well with those measured from particle blasting experiments. Finally, a numerical model for simulating overlapping impacts of angular particles was developed and compared to experimental multi-particle erosion tests, with good agreement. An investigation of the simulated trajectory of the impacting particles revealed various erosion mechanisms such as the micromachining of chips, the ploughing of craters, and the formation, forging and knocking off crater lips which were consistent with previously noted ductile solid particle erosion mechanisms in the literature.