Powder bed fusion is a commonly used Additive Manufacturing technique. This technique uses a layer-by-layer approach to create the desired part in 3D printing, where the layers are created by spreading a thin layer of powder. The ability to simulate this process would give scientists the opportunity to visualize this process before printing the part, allowing them to best utilize the capabilities of powder bed fusion. Spreading of the powder to create the layer to be fused is the first step in the process, and the quality of the layer can impact the building of the part. The overall goal of this research is to investigate the use of simulation models for the spreading of the powder. However, before this simulation is possible, the required simulation inputs must be understood, and the model calibrated. Calibration of the simulation models is the focus of this research. The simulation inputs are based on the powder used in the process. Powder characterization tests are run to understand properties about the powder. One of the most common, due to its simplicity, is the angle of repose test. This paper develops an efficient calibration model for the simulation of the angle of repose test using the discrete element method. The discrete element method (DEM) is the basis to calculate how the particles react when they collide with other particles or equipment. A commercial DEM software, EDEM, is used to simulate the DEM for this experiment. This calibration technique efficiently calibrates the input variables associated with the angle of repose test. Future research can apply this technique to ultimately calibrate a simulation for powder spreading in the powder bed fusion process.
Proceedings of the Third International Conference on Discrete Element Methods, held in Santa Fe, New Mexico on September 23-25, 2002. This Geotechnical Special Publication contains 72 technical papers on discrete element methods (DEM), a suite of numerical techniques developed to model granular materials, rock, and other discontinua at the grain scale. Topics include: DEM formulation and implementation approaches, coupled methods, experimental validation, and techniques, including three-dimensional particle representations, efficient contact detection algorithms, particle packing schemes, and code design. Coupled methods include approaches to linking solid continuum and fluid models with DEM to simulate multiscale and multiphase phenomena. Applications include fundamental investigations of granular mechanics; micromechanical studies of powder, soil, and rock behavior; and large-scale modeling of geotechnical, material processing, mining, and petroleum engineering problems.
Complex behavior models (plasticity, cracks, visco elascticity) face some theoretical difficulties for the determination of the behavior law at the continuous scale. When homogenization fails to give the right behavior law, a solution is to simulate the material at a meso scale in order to simulate directly a set of discrete properties that are responsible of the macroscopic behavior. The discrete element model has been developed for granular material. The proposed set shows how this method is capable to solve the problem of complex behavior that are linked to discrete meso scale effects. The first book solves the local problem, the second one presents a coupling approach to link the structural effects to the local ones, this third book presents the software workbench that includes all the theoretical developments.
Complex behavior models (plasticity, cracks, visco elascticity) face some theoretical difficulties for the determination of the behavior law at the continuous scale. When homogenization fails to give the right behavior law, a solution is to simulate the material at a meso scale in order to simulate directly a set of discrete properties that are responsible of the macroscopic behavior. The discrete element model has been developed for granular material. The proposed set shows how this method is capable to solve the problem of complex behavior that are linked to discrete meso scale effects.
The combined finite discrete element method is a relatively new computational tool aimed at problems involving static and / or dynamic behaviour of systems involving a large number of solid deformable bodies. Such problems include fragmentation using explosives (e.g rock blasting), impacts, demolition (collapsing buildings), blast loads, digging and loading processes, and powder technology. The combined finite-discrete element method - a natural extension of both discrete and finite element methods - allows researchers to model problems involving the deformability of either one solid body, a large number of bodies, or a solid body which fragments (e.g. in rock blasting applications a more or less intact rock mass is transformed into a pile of solid rock fragments of different sizes, which interact with each other). The topic is gaining in importance, and is at the forefront of some of the current efforts in computational modeling of the failure of solids. * Accompanying source codes plus input and output files available on the Internet * Important applications such as mining engineering, rock blasting and petroleum engineering * Includes practical examples of applications areas Essential reading for postgraduates, researchers and software engineers working in mechanical engineering.
This book presents the latest advances in Discrete Element Methods (DEM) and technology. It is the proceeding of 7th International Conference on DEM which was held at Dalian University of Technology on August 1 - 4, 2016. The subject of this book are the DEM and related computational techniques such as DDA, FEM/DEM, molecular dynamics, SPH, Meshless methods, etc., which are the main computational methods for modeling discontinua. In comparison to continua which have been already studied for a long time, the research of discontinua is relatively new, but increases dramatically in recent years and has already become an important field. This book will benefit researchers and scientists from the academic fields of physics, engineering and applied mathematics, as well as from industry and national laboratories who are interested in the DEM.
Additive manufacturing (AM) is a fast-growing sector with the ability to evoke a revolution in manufacturing due to its almost unlimited design freedom and its capability to produce personalised parts locally and with efficient material use. AM companies, however, still face technological challenges such as limited precision due to shrinkage, built-in stresses and limited process stability and robustness. Moreover, often post-processing is needed due to high roughness and remaining porosity. Qualified, trained personnel are also in short supply. In recent years, there have been dramatic improvements in AM design methods, process control, post-processing, material properties and material range. However, if AM is going to gain a significant market share, it must be developed into a true precision manufacturing method. The production of precision parts relies on three principles: Production is robust (i.e. all sensitive parameters can be controlled). Production is predictable (for example, the shrinkage that occurs is acceptable because it can be predicted and compensated in the design). Parts are measurable (as without metrology, accuracy, repeatability and quality assurance cannot be known). AM of metals is inherently a high-energy process with many sensitive and inter-related process parameters, making it susceptible to thermal distortions, defects and process drift. The complete modelling of these processes is beyond current computational power, and novel methods are needed to practicably predict performance and inform design. In addition, metal AM produces highly textured surfaces and complex surface features that stretch the limits of contemporary metrology. With so many factors to consider, there is a significant shortage of background material on how to inject precision into AM processes. Shortage in such material is an important barrier for a wider uptake of advanced manufacturing technologies, and a comprehensive book is thus needed. This book aims to inform the reader how to improve the precision of metal AM processes by tackling the three principles of robustness, predictability and metrology, and by developing computer-aided engineering methods that empower rather than limit AM design. Richard Leach is a professor in metrology at the University of Nottingham and heads up the Manufacturing Metrology Team. Prior to this position, he was at the National Physical Laboratory from 1990 to 2014. His primary love is instrument building, from concept to final installation, and his current interests are the dimensional measurement of precision and additive manufactured structures. His research themes include the measurement of surface topography, the development of methods for measuring 3D structures, the development of methods for controlling large surfaces to high resolution in industrial applications and the traceability of X-ray computed tomography. He is a leader of several professional societies and a visiting professor at Loughborough University and the Harbin Institute of Technology. Simone Carmignato is a professor in manufacturing engineering at the University of Padua. His main research activities are in the areas of precision manufacturing, dimensional metrology and industrial computed tomography. He is the author of books and hundreds of scientific papers, and he is an active member of leading technical and scientific societies. He has been chairman, organiser and keynote speaker for several international conferences, and received national and international awards, including the Taylor Medal from CIRP, the International Academy for Production Engineering.
This book provides a detailed instruction to virtually reproduce the processes of Additive Manufacturing on a computer. First, all mathematical equations needed to model these processes are presented. Due to their flexibility, meshfree methods represent optimal computational solution schemes to simulate Additive Manufacturing processes. On the other hand, these methods usually do not guarantee an accurate solution. For this reason, this monograph is dedicated in detail to the necessary criteria for computational solution schemes to provide accurate results. Several meshfree methods are examined with respect to these conditions. Two different 3D printing techniques are presented in detail. The results obtained from the simulation are investigated and compared with experimental data. This work is addressed to both scientists and professionals working in the field of development who are interested to learn the secrets behind meshfree methods or get into the modeling of Additive Manufacturing.
In this dissertation, two main topics will be discussed. First, a novel approach to computational mechanics via a Domain Specific Language(DSL) with a syntax to facilitate new model development will be presented. Second, discrete element multiphysical models will be proposed to study powder based additive manufacturing processes. The DSL presented is a tool for computational mechanics which is designed to allow an engineer to focus more on model development and investigation by providing a syntax which makes it easier to define new discretizations and test different constitutive models. In order to achieve this, a system for managing data and specifying models is created around the Python development environment. There are three powerful features of the DSL. First, the language provides a syntax for creating objects which describe the fundamental physical objects and numerical elements in the problem and facilitates the allocation, management and modification of the data allocated for these objects. Second, all constitutive models are input using symbolic notation allowing for the language of math, rather than raw code, to be used to describe interactions. Third, low level code is automatically generated for the models and their gradients(via symbolic differentiation) for use with linear and non-linear solvers and time-stepping methods, both explicit and implicit. Also, Python wrappers are automatically generated so the high performance implementations can be used in the Python environment without additional work by the user. The discrete element method is a Lagrangian technique which uses interactions of spherical elements to model material behaviors. In the past, it has been most commonly used in the study of granular media such as sands and soils. Here, extensions to the method to model heat transfer, thermal expansion and interactions with non-spherical objects will be discussed for simulating additive manufacturing processes. The formulation, implemented with the DSL, is used to study powder packing in a manner that is physically consistent with Selective Laser Sintering/Melting machines. Also, the dynamics of powders subjected to a heat source are investigated. Additional multiphysics behavior is incorporated through a temperature dependent bonding model to create an efficient simulation for studying Laser Metal Deposition. Finally, a method for using discrete elements to enhance Eulerian finite elements to efficiently prevent advection welding is proposed.
Discrete Element Methods (DEM) is a numerical technique for analysing the mechanics and physics of particulate systems. Originated in the late seventies for analysing geotechnical problems, it has seen significant development and is now employed extensively across disciplines. Produced in celebration of the 70th Birthday of Colin Thornton, this book contains a selection of papers concerning advances in discrete element modelling which were presented at the International Symposium on Discrete Element Modelling of Particulate Media held at Birmingham, UK on 28-30th March, 2012. The book showcases the wide application of discrete element modelling in gas-solid fluidisation, particulate flows, liquid-solid systems and quasi-static behaviour. It also reports the recent advancement in coupled DEM with computational fluid dynamics, Lattice Boltzmann Methods for multiphase systems and the novel application of DEM in contact electrification and fracture of granular systems. Aimed at research communities dealing with this technique in the powder handling and formulation industries, this will be a welcomed addition to the literature in this area.
