scholarly journals Modelling Polycrystalline Materials: An Overview of Three-Dimensional Grain-Scale Mechanical Models

2013 ◽  
Vol 05 (01) ◽  
pp. 1350002 ◽  
Author(s):  
I. Benedetti ◽  
F. Barbe
Keyword(s):  
Three Dimensional ◽  
Constitutive Modelling ◽  
Polycrystalline Materials ◽  
High Fidelity ◽  
Computational Capability ◽  
Mechanical Models ◽  
Three Dimensional Models ◽  
The Individual ◽  
Individual Grains ◽  
Micro Structures

A survey of recent contributions on three-dimensional grain-scale mechanical modelling of polycrystalline materials is given in this work. The analysis of material micro-structures requires the generation of reliable micro-morphologies and affordable computational meshes as well as the description of the mechanical behavior of the elementary constituents and their interactions. The polycrystalline microstructure is characterized by the topology, morphology and crystallographic orientations of the individual grains and by the grain interfaces and microstructural defects, within the bulk grains and at the inter-granular interfaces. Their analysis has been until recently restricted to two-dimensional cases, due to high computational requirements. In the last decade, however, the wider affordability of increased computational capability has promoted the development of fully three-dimensional models. In this work, different aspects involved in the grain-scale analysis of polycrystalline materials are considered. Different techniques for generating artificial micro-structures, ranging from highly idealized to experimentally based high-fidelity representations, are briefly reviewed. Structured and unstructured meshes are discussed. The main strategies for constitutive modelling of individual bulk grains and inter-granular interfaces are introduced. Some attention has also been devoted to three-dimensional multiscale approaches and some established and emerging applications have been discussed.

Three-Dimensional X-Ray Diffraction Microscopy Using High-Energy X-Rays

MRS Bulletin ◽  
2004 ◽  
Vol 29 (3) ◽  
pp. 166-169 ◽  
Author(s):  
Henning F. Poulsen ◽  
Dorte Juul Jensen ◽  
Gavin B.M. Vaughan
Keyword(s):  
Materials Science ◽  
Three Dimensional ◽  
High Energy ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reconstruction Methods ◽  
The Individual ◽  
Individual Grains

AbstractThree-dimensional x-ray diffraction (3DXRD) microscopy is a tool for fast and nondestructive characterization of the individual grains, subgrains, and domains inside bulk materials. The method is based on diffraction with very penetrating hard x-rays (E ≥ 50 keV), enabling 3D studies of millimeter-to-centimeter-thick specimens.The position, volume, orientation, and elastic and plastic strain can be derived for hundreds of grains simultaneously. Furthermore, by applying novel reconstruction methods, 3D maps of the grain boundaries can be generated. The 3DXRD microscope in use at the European Synchrotron Radiation Facility in Grenoble, France, has a spatial resolution of ∼5 μm and can detect grains as small as 150 nm. The technique enables, for the first time, dynamic studies of the individual grains within polycrystalline materials. In this article, some fundamental materials science applications of 3DXRD are reviewed: studies of nucleation and growth kinetics during recrystallization, recovery, and phase transformations, as well as studies of polycrystal deformation.

scholarly journals An advanced shape-fitting algorithm applied to quadrupedal mammals: improving volumetric mass estimates

2015 ◽  
Vol 2 (8) ◽  
pp. 150302 ◽  
Author(s):  
Charlotte A. Brassey ◽  
James D. Gardiner
Keyword(s):  
Body Mass ◽  
Three Dimensional ◽  
Physical Property ◽  
Skeletal Structure ◽  
Shape Fitting ◽  
Alpha Shapes ◽  
Fundamental Physical Property ◽  
Three Dimensional Models ◽  
The Individual ◽  
Ground Sloth

Body mass is a fundamental physical property of an individual and has enormous bearing upon ecology and physiology. Generating reliable estimates for body mass is therefore a necessary step in many palaeontological studies. Whilst early reconstructions of mass in extinct species relied upon isolated skeletal elements, volumetric techniques are increasingly applied to fossils when skeletal completeness allows. We apply a new ‘alpha shapes’ ( α -shapes) algorithm to volumetric mass estimation in quadrupedal mammals. α -shapes are defined by: (i) the underlying skeletal structure to which they are fitted; and (ii) the value α , determining the refinement of fit. For a given skeleton, a range of α -shapes may be fitted around the individual, spanning from very coarse to very fine. We fit α -shapes to three-dimensional models of extant mammals and calculate volumes, which are regressed against mass to generate predictive equations. Our optimal model is characterized by a high correlation coefficient and mean square error ( r 2 =0.975, m.s.e.=0.025). When applied to the woolly mammoth ( Mammuthus primigenius ) and giant ground sloth ( Megatherium americanum ), we reconstruct masses of 3635 and 3706 kg, respectively. We consider α -shapes an improvement upon previous techniques as resulting volumes are less sensitive to uncertainties in skeletal reconstructions, and do not require manual separation of body segments from skeletons.

A Model for Bending, Torsional, and Axial Vibrations of Micro- and Macro-Drills Including Actual Drill Geometry—Part I: Model Development and Numerical Solution

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Sinan Filiz ◽  
O. Burak Ozdoganlar
Keyword(s):  
Cross Section ◽  
Model Development ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Three Dimensional Model ◽  
Axial Thrust ◽  
One Dimensional ◽  
Three Dimensional Models ◽  
The Individual ◽  
Actual Geometry

Part I of this work presents a combined one-dimensional/three-dimensional approach for obtaining a unified model for the dynamics of micro- and macro-drills. To increase the numerical efficiency of the model, portions of the drill with circular cross-section (shank, extension, and tapered sections) are modeled using one-dimensional beam models without compromising model accuracy. A three-dimensional model is used for an accurate representation of the fluted section, considering the actual geometry with the pretwisted shape and axially varying (nonaxisymmetric) cross-section. The actual cross-section of the drills is incorporated to the model through a polynomial mapping while the pretwist effect is captured by defining a rotating reference frame. The boundary-value problem for both one- and three-dimensional models are derived using a variational approach, based on the extended Hamilton’s principle, and are subsequently solved by applying the spectral-Tchebychev technique. A component-mode synthesis is used for connecting the individual sections to obtain the dynamic model for the entire drill. Convergence of the model is studied by varying the number of polynomials for each section. The experimental validation of the model is included in Part II for both macro- and micro-drills. Also included in Part II is an analysis of drill dynamics for varying drill-geometry parameters and axial (thrust) force.

scholarly journals Person-centred mental health care: the challenge of implementation

2012 ◽  
Vol 21 (2) ◽  
pp. 139-144 ◽  
Author(s):  
L. Gask ◽  
P. Coventry
Keyword(s):  
Mental Health ◽  
Health Care ◽  
Mental Health Care ◽  
Three Dimensional ◽  
Holistic Approach ◽  
Health And Social Care ◽  
Unique Experience ◽  
Three Dimensional Models ◽  
The Individual ◽  
The Impact

Within mental health care, ‘person-centredness’ has been generally interpreted to convey a holistic approach with an attitude of respect for the individual and his/her unique experience and needs. Although it has been possible to demonstrate that professionals can acquire such skills through training, the impact on clinical outcomes has been more difficult to demonstrate in randomized controlled trials. Indeed what is becoming increasingly apparent in the literature is the need to acknowledge and address the degree of complexity that exists within the health care system that militates against achieving satisfactory implementation and outcomes from person-centred mental health care. In addressing this, we must develop and work with more sophisticated and three-dimensional models of ‘patient-centredness’ that engage with not only what happens in the consulting room (the relationship between individual service users and healthcare professionals), but also addresses the problems involved in achieving person-centredness through modifying the way that services and organizations work, and finally by engaging families and communities in the delivery of health care. A truly meaningful concept of ‘people-centredness’ encompasses how the views of the population are taken into consideration not only in healthcare but also in health and social care policy, and wider society too.

Box-Scan: A Novel 3DXRD Method for Studies of Recrystallization and Grain Growth

2012 ◽  
Vol 715-716 ◽  
pp. 518-520 ◽  
Author(s):  
Allan Lyckegaard ◽  
Henning Friis Poulsen ◽  
Wolfgang Ludwig ◽  
Richard W. Fonda ◽  
Erik M. Lauridsen
Keyword(s):  
Spatial Resolution ◽  
Near Field ◽  
Polycrystalline Materials ◽  
High Temporal Resolution ◽  
Far Field ◽  
X Ray Diffraction ◽  
The Individual ◽  
Individual Grains ◽  
Non Destructive

Within the last decade a number of x-ray diffraction methods have been presented for non-destructive 3D characterization of polycrystalline materials. 3DXRD [1] and Diffraction Contrast Tomography [2,3,4] are examples of such methods providing full spatial and crystallographic information of the individual grains. Both methods rely on specially designed high-resolution near-field detectors for acquire the shape of the illuminated grains, and therefore the spatial resolution is for both methods limited by the resolution of the detector, currently ~2 micrometers. Applying these methods using conventional far-field detectors provides information on centre of mass, crystallographic orientation and stress state of the individual grains [5], at the expense of high spatial resolution. However, far-field detectors have much higher efficiency than near-field detectors, and as such are suitable for dynamic studies requiring high temporal resolution and set-ups involving bulky sample environments (e.g. furnaces, stress-rigs etc.)

scholarly journals Bringing to Life a Newly Discovered Signature of Fatigue Crack Initiation via Multimodal Characterizations

2022 ◽  
Author(s):  
Dalton Shadle ◽  
Kelly Nygren ◽  
Jean Stinville ◽  
Marie Charpagne ◽  
Timothy Long ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Driving Forces ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Orientation Distributions ◽  
The Individual ◽  
Individual Grains

Abstract Fatigue is the most prevalent failure mode in structural materials, yet remains challenging to study due to the seemingly unpredictable nature of crack initiation. To elucidate the driving forces of crack initiation in ductile polycrystalline metals, we employ a multimodal approach to identify and track grains with a suspected potential to initiate fatigue cracks via a newly founded signature. We discover this crack initiation potential (CIP) signature under the hypothesis that slip localization, a well-known precursor to crack initiation, is linked to intragrain misorientation, which can be quantified through single grain orientation distributions. We verify the CIP signature in an Inconel-718 material via static two-dimensional and three-dimensional electron microscopy and “bring to life” the dynamics of the CIP signature via in-situ synchrotron X-ray diffraction. With this CIP signature, we move to better focus studies of fatigue crack initiation on the individual grains and processes that drive fatigue failure.

3DXRD – Mapping Grains and Their Dynamics in 3 Dimensions

2004 ◽  
Vol 467-470 ◽  
pp. 1363-1372 ◽  
Author(s):  
Henning Friis Poulsen ◽  
Xing Fu ◽  
Erik Knudsen ◽  
Erik M. Lauridsen ◽  
L. Margulies ◽  
...  
Keyword(s):  
European Synchrotron Radiation Facility ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
Time Dynamic ◽  
3 Dimensional ◽  
Reconstruction Methods ◽  
Set Up ◽  
The Individual ◽  
Individual Grains

3-Dimensional X-Ray Diffraction (3DXRD) microscopy is a tool for fast and non-destructive characterization of the individual grains, sub-grains and domains inside bulk materials. The method is based on diffraction with highly penetrating hard x-rays, enabling 3D studies of millimeter - centimeter thick specimens. The position, volume, orientation, elastic and plastic strain can be derived for hundreds of grains simultaneously. Furthermore, by applying novel reconstruction methods 3D maps of the grain boundaries can be generated. With the present 3DXRD microscope set-up at the European Synchrotron Radiation Facility, the spatial resolution is ~ 5 µm, while grains of size 100 nm can be detected. 3DXRD microscopy enables, for the first time, dynamic studies of the individual grains and sub-grains within polycrystalline materials. The methodology is reviewed with emphasis on recent advances in grain mapping. Based on this a series of general 3DXRD approaches are identified for studies of nucleation and growth phenomena such as recovery, recrystallisation and grain growth in metals.

scholarly journals Framework for 3D Point Cloud Modelling Aimed at Road Sight Distance Estimations

2019 ◽  
Vol 11 (23) ◽  
pp. 2730
Author(s):  
González-Gómez ◽  
Iglesias ◽  
Rodríguez-Solano ◽  
Castro
Keyword(s):  
Point Cloud ◽  
Three Dimensional ◽  
The Road ◽  
3D Objects ◽  
Sight Distance ◽  
Road Geometry ◽  
Three Dimensional Models ◽  
The Individual ◽  
Periodic Evaluation ◽  
Cloud Modelling

Existing roads require periodic evaluation in order to ensure safe transportation. Estimations of the available sight distance (ASD) are fundamental to make sure motorists have sufficient visibility to perform basic driving tasks. Mobile LiDAR Systems (MLS) can provide these evaluations with accurate three-dimensional models of the road and surroundings. Similarly, Geographic Information System (GIS) tools have been employed to obtain ASD. Due to the fact that widespread GIS formats used to store digital surface models handle elevation as an attribute of location, the presented methodology has separated the representation of ground and aboveground elements. The road geometry and surrounding ground are stored in digital terrain models (DTM). Correspondingly, abutting vegetation, manmade structures, road assets and other roadside elements are stored in 3D objects and placed on top of the DTM. Both the DTM and 3D objects are accurately obtained from a denoised and classified LiDAR point cloud. Based on the consideration that roadside utilities and most manmade structures are well-defined geometric elements, some visual obstructions are extracted and/or replaced with 3D objects from online warehouses. Different evaluations carried out with this method highlight the tradeoff between the accuracy of the estimations, performance and geometric complexity as well as the benefits of the individual consideration of road assets.

Mechanical Models of Cell Adhesion Incorporating Nonlinear Behavior and Stochastic Rupture of the Bonds

2011 ◽  
pp. 599-627
Author(s):  
Jean-François Ganghoffer
Keyword(s):  
Cell Membrane ◽  
Three Dimensional ◽  
Point Of View ◽  
Three Dimensional Model ◽  
Stochastic Field ◽  
Present Contribution ◽  
Ecm Extracellular Matrix ◽  
Mechanical Models ◽  
Distribution Of Power ◽  
The Individual

The rolling of a single biological cell is analysed using modelling of the local kinetics of successive attachment and detachment of bonds occurring at the interface between a single cell and the wall of an ECM (extracellular matrix). Those kinetics correspond to a succession of creations and ruptures of ligand-receptor molecular connections under the combined effects of mechanical, physical (both specific and non-specific), and chemical external interactions. A three-dimensional model of the interfacial molecular rupture and adhesion kinetic events is developed in the present contribution. From a mechanical point of view, this chapter works under the assumption that the cell-wall interface is composed of two elastic shells, namely the wall and the cell membrane, linked by rheological elements representing the molecular bonds. Both the time and space fluctuations of several parameters related to the mutual affinity of ligands and receptors are described by stochastic field theory; especially, the individual rupture limits of the bonds are modelled in Fourier space from the spectral distribution of power. The bonds are modelled as macromolecular chains undergoing a nonlinear elastic deformation according to the commonly used freely joined chains model, while the cell membrane facing the ECM wall is modelled as a linear elastic plate. The cell itself is represented by an equivalent constant rigidity. Numerical simulations predict the sequence of broken bonds, as well as the newly established connections on the ‘adhesive part’ of the interface. The interplay between adhesion and rupture entails a rolling phenomenon. In the last part of this chapter, a model of the deformation induced by the random fluctuation of the protrusion force resulting from the variation of affinity with chemiotactic sources is calculated, using stochastic finite element methods in combination with the theory of Gaussian random variables.

Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

2001 ◽  
Vol 34 (6) ◽  
pp. 751-756 ◽  
Author(s):  
H. F. Poulsen ◽  
S. F. Nielsen ◽  
E. M. Lauridsen ◽  
S. Schmidt ◽  
R. M. Suter ◽  
...  
Keyword(s):  
Stress State ◽  
Grain Boundaries ◽  
Tensile Deformation ◽  
Strain Tensor ◽  
Three Dimensional ◽  
High Energy ◽  
European Synchrotron Radiation Facility ◽  
X Rays ◽  
The Individual ◽  
Individual Grains

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is verified by comparing an electron microscopy map of the orientations on the 2.5 × 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 µm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Δ∊ ≃ 10−4.

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