Experimental And Numerical Study Of Single And Multiple Imapcts Of Angular particles On Ductile ...

156 Pages·2013·4.86 MB·English

by  Mahdi Takaffoli

Ryerson University
Digital Commons @ Ryerson
Theses and dissertations
1-1-2012
Experimental And Numerical Study Of Single And
Multiple Imapcts Of Angular particles On Ductile
Metals
Mahdi Takaffoli
Ryerson University
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(2012).Theses and dissertations.Paper 1724.
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EXPERIMENTAL AND NUMERICAL STUDY OF SINGLE AND MULTIPLE IMPACTS OF
ANGULAR PARTICLES ON DUCTILE METALS

by

Mahdi Takaffoli
MSc, 2007, Tehran University, Iran
BSc, 2005, Iran University of Science and Technology, Iran

A dissertation
presented to Ryerson University

in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy
in the program of
Mechanical and Industrial Engineering

Toronto, Ontario, Canada, 2012
© Mahdi Takaffoli 2012
I hereby declare that I am the sole author of this dissertation. This is a true copy of the
dissertation, including any required final revisions, as accepted by my examiners.
I authorize Ryerson University to lend this dissertation to other institutions or individuals
for the purpose of scholarly research.
I further authorize Ryerson University to reproduce this dissertation by photocopying or
by other means, in total or in part, at the request of other institutions or individuals for the
purpose of scholarly research.
I understand that my dissertation may be made electronically available to the public.
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EXPERIMENTAL AND NUMERICAL STUDY OF SINGLE AND MULTIPLE IMPACTS OF
ANGULAR PARTICLES ON DUCTILE METALS

Mahdi Takaffoli

2012

Ph.D.

Department of Mechanical and Industrial Engineering
Ryerson University

Abstract
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
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150 m 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.
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Acknowledgements

I would like to express my very great appreciation to my supervisor, Professor Marcello
Papini whose guidance, expertise and encouragement was greatly helpful to me throughout my
PhD research. All the meetings and discussions I had with you left me with passion and great
ideas to address the challenges of my dissertation. I will forever be thankful to you for what I
have learned in the past five years.
I would also like to thank my supervisory committee, Dr. Daolun Chen and Dr. Donatus
Oguamanam, for their suggestions during my Ph.D. candidacy exam. My grateful thanks are
also extended to Professor Khaled Sennah and Professor William Altenhof for agreeing to be on
my examination committee.
I also wish to acknowledge the technical staff of our department, Misters Joseph
Amankrah, Alan Machin, Devin Ostrom, Qiang Li and Chao Ma whose support and assistance
were greatly helpful to me throughout my dissertation.
Very special thanks to the Natural Sciences and Engineering Council of Canada
(NSERC), the Canada Research Chairs Program, the Ontario Ministry of Training, Colleges and
Universities, the Ryerson University School of Graduate Studies and the Department of
Mechanical and Industrial Engineering for their financial support.
Finally my warmest gratitude to my mother, father and three sisters for all the caring and
support provided to me over the phone or in person when I visited home during the time of my
PhD. This dissertation is dedicated to them.

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Table of Contents
2B

Abstract ......................................................................................................................................... iii
Acknowledgements ....................................................................................................................... v
Table of Contents ......................................................................................................................... vi
Nomenclature ................................................................................................................................ x
List of Tables .............................................................................................................................. xiii
List of Figures ............................................................................................................................. xiv
List of Appendices .................................................................................................................... xviii
Chapter 1 Introduction................................................................................................................. 1
1.1 Background and motivation ...................................................................................... 1
1.2 Objectives ................................................................................................................. 2
1.3 Literature review ....................................................................................................... 3
1.3.1 Modeling single particle impact of angular particles ......................................... 3
1.3.2 Representative models of erosive particles ........................................................ 6
1.3.3 Numerical modeling of solid particle erosion of ductile metals ........................ 7
1.3.4 Material removal mechanisms in ductile metals .............................................. 10
1.4 Dissertation outline ................................................................................................. 11
Chapter 2 Lagrangian Finite Element Modeling of Single Particle Impacts ........................ 12
2.1 Introduction ............................................................................................................. 12
2.2 Experiments ............................................................................................................ 13
2.3 Finite element modeling ......................................................................................... 16
2.3.1 Material model ................................................................................................. 17
2.3.2 Contact model .................................................................................................. 19
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2.3.3 Element deletion and remeshing ...................................................................... 20
2.4 Rigid-plastic Model ................................................................................................ 20
2.5 Results and discussion ............................................................................................ 21
2.6 Summary and conclusions ...................................................................................... 29
Chapter 3 Smoothed Particle Hydrodynamics Modeling of Single Particle Impact ............ 31
3.1 Introduction ............................................................................................................. 31
3.2 The smoothed particle hydrodynamics (SPH) method ........................................... 31
3.3 Experiments ............................................................................................................ 33
3.4 Model description ................................................................................................... 36
3.4.1 Model Geometry and Boundary Conditions .................................................... 36
3.4.2 Contact definition............................................................................................. 37
3.4.3 Constitutive equation ....................................................................................... 38
3.4.4 Strain rate dependency ..................................................................................... 40
3.4.5 Failure model ................................................................................................... 40
3.5 Results and discussion ............................................................................................ 41
3.5.1 Effect of impact angle and initial orientation on impact crater ....................... 41
3.5.2 Effect of strain rate dependency model ........................................................... 42
3.5.3 Comparison of SPH model to experiments ...................................................... 42
3.5.4 The effect of tensile instability on the SPH results .......................................... 49
3.6 Summary and conclusions ...................................................................................... 50
Chapter 4 Three Dimensional Representation of Abrasive Particle Samples for Numerical
Modeling ...................................................................................................................................... 52
4.1. Introduction ............................................................................................................ 52
4.2 Particle Shape Characterization .............................................................................. 52
4.3 Particle Modeling .................................................................................................... 56
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4.4 Summary and Conclusions ..................................................................................... 57
Chapter 5 Numerical Simulation of Non-Coincident Impacts of 150-m Alumina Particles
on Al6061-T6 ............................................................................................................................... 59
5.1 Introduction ............................................................................................................. 59
5.2 Experiments ............................................................................................................ 59
5.2.1 Particle Impact Experiments ............................................................................ 59
5.2.2 Particle Velocity Measurement ........................................................................ 60
5.3 Modeling ................................................................................................................. 63
5.3.1 Implementation of representative particles in a FE/SPH model ...................... 63
5.3.2 Target Modeling............................................................................................... 64
5.4 Results and discussion ............................................................................................ 66
5.4.1 Crater and pile-up size distributions ................................................................ 66
5.4.2 Normal Incidence ............................................................................................. 66
5.4.3 Oblique Incidence ............................................................................................ 69
5.4.4 Material removal mechanisms ......................................................................... 73
5.5 Summary and conclusions ...................................................................................... 79
Chapter 6 Numerical Simulation of Multiple Overlapping Impact of Alumina Particles on
Al6061-T6..................................................................................................................................... 80
6.1 Introduction ............................................................................................................. 80
6.2 Experiments ............................................................................................................ 80
6.3 Model Description .................................................................................................. 80
6.4 Analysis of simulated and experimental eroded surfaces ....................................... 82
6.5 Results and discussion ............................................................................................ 82
6.5.1 Blasted surface topography .............................................................................. 82
6.5.2 Predicted erosion at various angles of attack ................................................... 84
6.5.3 Simulated erosion mechanisms ........................................................................ 87
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6.5.4 The effect of thermal softening on material removal ....................................... 95
6.6 Summary and Conclusions ..................................................................................... 95
Chapter 7 Summary and Conclusions ...................................................................................... 97
7.1 Summary ................................................................................................................. 97
7.2 Conclusions ............................................................................................................. 98
7.3 Contributions........................................................................................................... 99
7.4 Recommendations for Future Work...................................................................... 100
Appendices ................................................................................................................................. 103
A.1 A MATLAB Code to Generate a Representative Model of Erodent Powders .... 103
A.2 An ANSYS Parametric Design Language (APDL) Code to Construct FE Model of
a Sample of Representative Particles .......................................................................... 108
A.3 Evidence for the Ability of Thermal Softening to be Implemented into a Structural
Analysis Using the Johnson Cook Material Model .................................................... 119
A.3.1 LS-DYNA Manual ........................................................................................ 119
A.3.2 Evidence from papers in the literature .......................................................... 120
A.3.3 Taylor bar impact FE simulations ................................................................. 122
A.3.4 Conclusion .................................................................................................... 130
References .................................................................................................................................. 131

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