Lee Margetts

• BSc, MSc, PhD, MBA
• UKAEA Chair of Digital Engineering for Fusion Energy at The University of Manchester

Following rupture, tendons are sutured to reapproximate the severed ends and permit healing. Several repair techniques are employed clinically, with recent focus towards high-strength sutures, permitting early active mobilisation thus improving resultant joint mobility. However, the arrangement of suture repairs locally alters the loading environme...

Many students, engineers, scientists and researchers have benefited from the practical, programming-oriented style of the previous editions of Programming the Finite Element Method, learning how to develop computer programs to solve specific engineering problems using the finite element method. This new fifth edition offers timely revisions that i...

Sauropod dinosaurs are the largest terrestrial vertebrate to have lived on Earth. This size must have posed special challenges for the musculoskeletal system. Scaling theory shows that body mass and hence the loads that must be overcome increases with body size more rapidly than either the ability of the muscles to generate force, or the ability of...

A large part of the earth’s surface is covered by seasonally or permanently frozen soils. Considering the negative impact of climate change, future development of such regions can be underpinned by mathematical methods for accurate analysis of heat and moisture transport in freezing and thawing soils. Reported in this paper is a novel non-local for...

Understanding of the thermal, hydraulic and mechanical behavior of soils under freezing and thawing is important in solving problems of permafrost engineering and artificial ground freezing. Accurate mathematical descriptions of heat and moisture transport and the associated mechanical deformations is critical for developing such understanding. Pha...

1. Abstract This work investigates the toughening mechanisms in concrete due to fibre reinforcement when a crack propagates in a notched ultra high performance fibre reinforced concrete (UHPFRC). The specimen was imaged using X-ray computed tomography (XCT) during the in-situ loading. A wedge splitting test of a 40x20x25mm specimen was carried out...

Surrogate models have been used as a substitute for traditional engineering simulation to get target simulation results faster. These surrogate models usually need sufficient data to fulfil their optimum performance. However, the acquisition of high quality datasets for cases like welding residual stress is both difficult and costly. This work deve...

Describing heat transfer in domains with strong non-linearities and discontinuities, e.g. propagating fronts between different phases, or growing cracks, is a challenge for classical approaches, where conservation laws are formulated as partial differential equations subsequently solved by discretisation methods such as the finite element method (F...

New high-performance computing (HPC) software designed for massively parallel computers with high-speed interconnects is presented to accelerate research into geometric formulations of solid mechanics based on discrete exterior calculus (DEC). DEC is a relatively new and entirely discrete approach being developed to model non-smooth material proces...

Nuclear graphite is a candidate material for Generation IV nuclear power plants. Porous materials such as graphite can contain complex networks of pores that influence the material's mechanical and irradiation response. A methodology known as the random finite element method (RFEM) was adapted to create synthetic microstructures and predict the inf...

This manuscript provides optical microscopy, scanning electron microscopy, and transmission electron microscopy micrographs that show the microstructure of three superfine nuclear graphite grades IG-110, 2114 and ETU-10. This collection of microstructural data showcases the microstructure of these materials and helps to differentiate the most impor...

Nuclear graphite is a candidate material for Generation IV nuclear power plants. Porous materials such as graphite can contain complex networks of pores that influence the material's mechanical and irradiation response. A methodology known as the random finite element method (RFEM) was adapted to create synthetic microstructures and predict the inf...

A formulation of elliptic boundary value problems is used to develop the first discrete exterior calculus (DEC) library for massively parallel computations with 3D domains. This can be used for steady-state analysis of any physical process driven by the gradient of a scalar quantity, e.g. temperature, concentration, pressure or electric potential,...

Non-healing wounds have led to a soaring clinical and socioeconomical need for advanced wound-care techniques. Electrical stimulation is an emerging therapy inspired by the wound's endogenous electric field. Promising results of clinical trials have encouraged efforts to create wearable stimulation devices, uncover multiple cellular targets, and op...

Stenosis of the cerebral aqueduct (CA) is featured in many studies relating to elevated intracranial cerebral pressures. It also presents a challenging situation to clinicians. Compressive forces play a lead role in pathological situations such as the presence of tumors and hence can cause obstruction to the flow of cerebrospinal fluid (CSF). Becau...

A wide range of natural and industrial processes involve heat and mass transport in porous media. In some important cases the transported substance may undergo phase change, e.g. from liquid to solid and vice versa in the case of freezing and thawing of soils. The predictive modelling of such phenomena faces physical (multiple physical processes ta...

Background: Stenosis of cerebral aqueduct (CA) is featured in many studies related to elevated intracranial cerebral pressures (ICP). It also presents a challenging situation to clinicians. Compressive forces play a lead role in pathological situations like tumor presence and hence can cause obstruction to the flow of cerebrospinal fluid (CSF). Due...

A direct formulation of linear elasticity of cell complexes based on discrete exterior calculus is presented. The primary unknown are displacements, represented by primal vector-valued 0-cochain. Displacement differences and internal forces are represented by primal vector-valued 1-cochain and dual vector-valued 2-cochain, respectively. The macrosc...

Brain is an actuator for control and coordination. When a pathology arises in cranium, it may leave a degenerative, disfiguring and destabilizing impact on brain physiology. However, the leading consequences of the same may vary from case to case. Tumour, in this context, is a special type of pathology which deforms brain parenchyma permanently. Fr...

Fracture is an inherently statistical phenomenon as it is a function of micro-structural heterogeneities such as distributed defects and inclusions. This is evidenced by scatter in the toughness of seemingly identical specimens. Therefore, deterministic approaches do not give full picture of scatter in fracture behaviour. More suitable probabilisti...

A wide range of natural and industrial processes involve heat and mass transport in porous media. In some important cases the transported substance may undergo phase change, e.g. from liquid to solid and vice versa in the case of freezing and thawing of soils. The predictive modelling of such phenomena faces physical (multiple physical processes ta...

Recent high profile collapses coupled with an aging bridge stock, increased loading and the pressures of climate change have led to greater focus on bridge management by policy makers. To prevent any negative socio-economic impacts, timely inspection of bridges becomes of prime importance. Visual inspection is standard practice around the world but...

This paper presents a novel AI based self-organising data reduction technique which combines feature detection and topological learning to reduce the memory footprint of point cloud data in an adaptive way, reducing point density in featureless parts of the point cloud whilst maintaining sufficient points to preserve details of interest to the engi...

Accurate analysis of heat transfer with phase change is important for many natural phenomena and engineering applications. Modelling of this phenomenon is a challenging mathematical problem due to the multi-physical nature of the processes involved. The phase transition introduces strong non-linearity caused by rapid variations of thermo-physical p...

A direct formulation of linear elasticity of cell complexes based on discrete exterior calculus is presented. The primary unknown are displacements, represented by primal vector-valued 0-cochain. Displacement differences and internal forces are represented by primal vector-valued 1-cochain and dual vector-valued 2-cochain, respectively. The macrosc...

A formulation of elliptic boundary value problems is used to develop the first discrete exterior calculus (DEC) library for massively parallel computations with 3D domains. This can be used for steady-state analysis of any physical process driven by the gradient of a scalar quantity, e.g. temperature, concentration, pressure or electric potential,...

Cerebrospinal fluid (CSF) plays a pivotal role in normal functioning of Brain. Intracranial compartments such as blood, brain and CSF are incompressible in nature. Therefore, if a volume imbalance in one of the aforenoted compartments is observed, the other reaches out to maintain net change to zero. Whereas, CSF has higher compliance over long ter...

This paper presents a novel computational framework for modelling multiscale fracture that can be used to solve engineering problems subject to dynamic loading. The framework simulates, mechanistically, at the mesoscale, the physical processes that lead to brittle fracture. A homogenisation step is used to translate the accumulation of damage from...

Material nonlinearity is implemented in finite element programs using mathematical models of material behaviour. These are typically defined by a set of parameters whose values are determined from experimental data. These constitutive models are phenomenological; that is they describe nonlinear material behaviour, but do not explicitly model the ph...

This paper presents OpenFPCI, a framework for coupling the C++ toolbox OpenFOAM-Extend, a computational fluid dynamics package, with the general purpose finite element package ParaFEM, written in Fortran and used to solve structural mechanics problems. The coupling of these two open source and scalable toolboxes, facilitates the use of high perform...

This paper proposes a novel method for bridge inspection that essentially digitises bridges using LIDAR so that they can be later inspected in a virtual reality environment. The work uses conventional terrestrial LIDAR together with affordable virtual reality hardware and freely available software development kits originally intended for authoring...

Total Cost of Ownership (TCO) is often asked about when comparing two different compute options but when it comes to using the cloud for simulations, it’s not truly about cost but rather value gained. There are many benefits that are more valuable than money in this context: ability, agility, competitiveness, innovation etc., for which you may need...

Functional materials' properties are influenced by microstructures which can be changed during manufacturing. A technique is presented which digitises graphite foam via X-ray tomography and converts it into image-based models to determine properties in silico. By simulating a laser flash analysis its effective thermal conductivity is predicted. Res...

This paper presents the application of the image-based finite element method (IBFEM) to quantify the impact of micro-structure caused by manufacturing processes on the performance of fusion energy heat exchangers. The components, containing tungsten, were imaged with high-power lab-based X-ray CT and neutron CT. Volume data was converted into part-...

This paper presents the application of the image-based finite element method (IBFEM) to quantify the impact of micro-structure caused by manufacturing processes on the performance of fusion energy heat exchangers. The components, containing tungsten, were imaged with high-power lab-based X-ray CT and neutron CT. Volume data was converted into part-...

Timely, recent developments in X-ray micro-computed tomography (XµCT) imaging such as increased resolution and improved sample preparation are enabling non-destructive time lapse imaging of polymeric biomaterials when implanted in soft tissue, which we demonstrate herein. Imaging the full 3D structure of an implanted biomaterial provides new opport...

Graphite is a candidate material for Generation IV concepts and is used as a moderator in Advanced Gas-cooled Reactors (AGR) in the UK. Spatial material variability is present within billets causing different material property values between different components. Variations in material properties and irradiation effects can produce stress concentra...

This paper describes a multi-scale fracture framework, for modelling dynamic fracture in polycrystalline materials. The motivation behind developing such an application is to provide a high fidelity tool to model and capture dynamic structural deformations, at the macro scale, undergoing fracture at the micro scale. The application links two highly...

There are approximately over 2.5 million bridges throughout the world, built to withstand massive forces and last for decades or centuries but very unlikely to last forever. According to a recent survey, there are more than 64,000 bridges in the US that have been declared as structurally deficient. Moreover, recent bridge collapse incidents in Ital...

In the engineering world the post processing of CFD simulations is done with tools that are very difficult to use for whoever is not an insider. Moreover, simulations are often heavy and displaying the results may be very time consuming. This is even more true when the simulations are non-steady or in the case of Fluid-Structure Interaction, when i...

A 3D multi-scale cellular automata finite element (CAFE) frame-work for modelling fracture in heterogeneous materials is described. The framework is implemented in a hybrid MPI/Fortran coarray code for efficient parallel execution on HPC platforms. Two open source BSD licensed libraries developed by the authors in modern Fortran were used: CGPACK,...

Being able to predict bone fracture or implant stability needs a proper constitutive model of trabecular bone at the macroscale in multiaxial, non-monotonic loading modes. Its macroscopic damage behaviour has been investigated experimentally in the past, mostly with the restriction of uniaxial cyclic loading experiments for different samples, which...

MECD (pronounced MEK-DEE), the University of Manchester Engineering Campus Development, is a £300M+ capital building project that will bring all of the University of Manchester engineering schools under one roof, albeit a very large one! The project, which is scheduled to be completed for the 2019/20 academic year, is part of an impressive programm...

This paper uses X-ray computed tomography to track the mechanical response of a vertebrate (Barnacle goose) long bone subjected to an axial compressive load, which is increased gradually until failure. A loading rig was mounted in an X-ray computed tomography system so that a time-lapse sequence of three-dimensional (3D) images of the bone’s intern...

Specification file for CT Scanning.

The authors are working towards the development of an open source platform for solving fluid-structure interaction (FSI) problems that is scalable on high performance computing (HPC) systems. Using existing open source software, we have built a prototype application to demonstrate the benefits of high performance computing for this class of problem...

The purpose of this paper is to provide a high level, holistic overview of the work being undertaken in the wind energy industry. It summarises the main techniques used to simulate both aerodynamic and structural issues associated with wind turbines and farms. The motivation behind this paper is to provide new researchers with an outlook of the mod...

The academic literature is a rich source of articles about fluid-structure interaction. A common feature of these publications is that the structure is almost always an elastic solid. The structure is so unimportant that it is often dismissed as a " ghost " structure. One might interpret this as a cultural difference between experts in CFD and expe...

The purpose of this paper is to critically review and address the cause of variation in the values of elastic modulus (E) of bone. Properties used for materials (especially) bones is one of the crucial factors in modeling and simulation experiments with sensitive procedures such as Finite Elements. The values of elastic modulus acquired from second...

Many students, engineers, scientists and researchers have benefited from the practical, programming-oriented style of the previous editions of Programming the Finite Element Method, learning how to develop computer programs to solve specific engineering problems using the finite element method. This new fifth edition offers timely revisions that in...

Micro-finite element models have been extensively employed to evaluate the elastic properties of trabecular bone and, to a limited extent, its yield behaviour. The macroscopic stiffness tensor and yield surface are of special interest since they are essential in the prediction of bone strength and stability of implants at the whole bone level. Whil...

The objective of this study is to investigate whether there is significant spatial variability in the mechanical properties of Gilsocarbon nuclear graphite at different sections of the billet; specifically the dynamic Poisson’s ratio, dynamic shear modulus, dynamic Young’s modulus and density. Similar studies have been done, usually in the context...

A two-scale analytical-numerical homogenisation approach is developed to predict effective elastic properties of ultra high performance fibre reinforced concrete considering distribution of pore sizes acquired from 3D micro X-ray computed tomography (μXCT) images of 24.8μm resolution. In the first scale, the mortar, consisting of sand, cement paste...

Finite element methods (FEM) modelling of materials with complex microstructures is typically achieved by homogenisation and applying effective material properties. This work investigated the use of a technique whereby 3D X-ray tomography images of such materials are converted directly into image-based FEM (IBFEM) models. In this instance IBFEM was...

PDF version of powerpoint presentation that accompanies the abstract.

The finite element method is a well established technique used to predict the performance of engineering materials, components and structures under a range of environmental and loading conditions (Smith et al, 2014). In recent work, the authors have investigated why cracks in nuclear graphite bricks do not appear in the same location as predicted b...

Nuclear materials are subjected to demanding environments, encountering high temperature gradients and fast neutron fluxes that gradually damage its structure and therefore change the material properties. Some components of a nuclear reactor determine its lifetime , such as the graphite core and steel pressure vessel for fission reactors. In case o...

This paper describes the porting of the open source engineering software ParaFEM to the Intel Xeon Phi processor. The results of a preliminary performance study are presented for a new open source ParaFEM mini-app written especially for the purpose. The main findings of the study are that: (i) The original MPI-based software scales linearly on up t...

The extreme environments found within the nuclear sector impose large safety factors on modelling analyses to ensure components operate in their desired manner. Improving analysis accuracy has clear value of increasing the design space that could lead to greater efficiency and reliability. Novel materials for new reactor designs often exhibit non-...

We have developed miniapps from MPI finite element library ParaFEM and Fortran 2008 coarray cellular automata library CGPACK. The miniapps represent multiscale fracture models of polycrystalline solids. The software from which these miniapps have been derived will improve predictive modelling in the automotive, aerospace, power generation, defense...

Computational homogenisation approaches using high resolution images and finite element (FE) modelling have been extensively employed to evaluate the anisotropic elastic properties of trabecular bone. The aim of this study was to extend its application to characterise the macroscopic yield behaviour of trabecular bone. Twenty trabecular bone sample...

The extreme environments found within the nuclear sector will be even more demanding as future generation power-plants strive for further efficiency and increased output. It is required that components not only withstand such conditions but operate in their desired manner, thus large safety factors are imposed on modelling analyses. Improving analy...

This chapter describes eight programs which enable the calculation of the intrinsic dynamic properties of systems, namely their undamped natural frequencies and mode shapes. The first program describes forced vibration analysis of elastic slender beam structures using direct integration in the ‘time domain’. Programs two, three, four and five descr...

This chapter deals with the transient states with inclusion of transport phenomena (diffusion with convection). It presents eleven programs that solve the transient problems. The first two programs analyse the 1D consolidation equation using an ‘implicit’ algorithm and program three uses an ‘explicit’ algorithm that avoids the need for global matri...

This chapter describes how finite element computation programs can be constructed in order to formulate and solve the matrix equations which take the form of linear and non-linear algebraic equations, eigenvalue equations or ordinary differential equations in the time variable. If differential equations are to be solved over regions of general shap...

This chapter describes 13 programs that deal only with material non-linearity. Before describing the programs, it presents a discussion on the form of the stress-strain laws that are to be adopted. In addition, two popular methods of generating body loads for ‘constant stiffness’ methods, namely ‘viscoplasticity’ and ‘initial stress’ are described....

Practical finite element analysis had as its starting point matrix analysis of ‘structures’, by which engineers usually mean assemblages of elastic, line elements. This chapter presents seven finite element programs. The first program, presented in this chapter, permits the analysis of a rod subjected to combinations of axial loads and displacement...

This chapter describes the finite element spatial discretisation process, whereby partial differential equations can be replaced by matrix equations which take the form of linear and non-linear algebraic equations, eigenvalue equations or ordinary differential equations in the time variable. This results in matrix equations relating the input at sp...

The ability to solve eigenvalue problems is important in many aspects of finite element work. This chapter describes four programs for the determination of eigenvalues and eigenvectors of elastic structures and solids. Different algorithms and storage strategies are employed in the various cases. The first program computes the natural frequencies a...

The five programs presented in this chapter solve steady-state problems governed by Laplace's equation. Typical examples of this type of problem include steady seepage through soils and steady heat flow through a conductor. Examples are presented of planar (confined and unconfined), axisymmetric and three-dimensional flow. The first program describ...

The aim of the present book is to teach the reader to write intelligible programs and to use them. Both serial and parallel computing environments are addressed and the building block routines and all test programs have been verified on a wide range of computers. The special features of vector, multi-core, graphics and parallel processors are expla...

This chapter describes seven programs which can be used to solve equilibrium problems in small strain solid elasticity. The first program deals with 2D plane strain or axisymmetric analysis of rectangular regions using any of the 2D elements described in this book. Program two introduces 3D strain for the special case of non-axisymmetric strain of...

This chapter describes six programs for steady-state and transient coupled problems. First program describes a steady-state solution of the Navier-Stokes equations, in which the simultaneous equations are non-linear. Program two solves the same problem without any global matrix assembly using a BiCGStab(l) iterative solver. Program three describes...

This chapter provides parallel finite element programs for the solution of a wide variety of problems in engineering and science. The chapter structured into five distinct sections namely introduction, differences between parallel and serial programs, graphics processing units, cloud computing and conclusion. The more common approach, used in the m...

At the conference, the author will present a critical review of the recent NAFEMS survey on “Computing Platforms for Engineering Simulation”. There is a growing choice of computing platforms for engineering simulation, from typical workstations through to compute clusters and Cloud Computing. Furthermore, each of these platforms can be “accelerated...