A Study of Ductile Damage and Failure of Pure Copper – Part I: Constitutive Equations and Experiments

This paper presents the results of an experimental study of ductile damage and failure of pure copper. Uniaxial tension tests were performed for specimens with different arrangements of pre-drilled micro-holes representing the simulation models of cylindrical voids. This experimental method has already been applied by a number of researchers in order to investigate the damage of metals under plastic deformation and proved to be useful for studying an evolution of damage in ductile materials in terms of local strains of both representative volume elements (RVE) and meso-elements (i.e., material unit cells with a single void). Two measures are used for the assessment of damage in the deformed material. The first one relates damage to an increase in the void volume. The second measure accounts for the damage associated with a change in the void shape. Both measures were introduced as part of a tensorial theory of damage in Zapara et al. (2008). They are based on experimental studies of damage kinetics in metallic materials under plasticity conditions. In combination with similar data from the literature the obtained results are important for the modeling of metal forming processes with dominating tensile deformation (e.g., deep-drawing, ironing, wire drawing)

A Study of Ductile Damage and Failure of Pure Copper – Part II: Analysis of the Deep Drawing Process of a Cylindrical Shell

The analysis of the stress-strain state and strain induced damage of a cylindrical shell made of copper during the process of deep drawing is presented. The stresses on the contact surface of operating tools (punch and die) are assigned implicitly, which leads to the mixed boundary-value problem. The results are obtained on the basis of the solution of the constitutive differential equations presenting plane plastic flow in curvilinear characteristic coordinates. The material functions required for the analysis of deep drawing were obtained by experimental studies of ductile damage and failure of pure copper (cf., Zapara et al., 2011). The process of deformation with discontinuities of the tangential velocities at the plastic zone boundaries is discussed. An estimate of the local strains and damage in the material is given both for the plastic zone and for its boundaries. The distributions of strains and of the damage within the wall of a finished part are determined. These distributions strongly affect the strength properties of a shell. The modeling of ductile damage in a material during deep drawing is based on experimental results and considerably extends them for a wider range of stress triaxialities. It is shown that the use of a drawing die with a cone angle of 12°...13° leads to a noticeable shift of the stress triaxialities into a range of negative values as compared to deep drawing with a die of larger angle ( 15°...18° ). The modeling reveals a smoother increase and decrease in damage of the finished part in case of the smaller cone angle as well as the absence of void coalescence. This fact is very important when manufacturing such products at high operating speeds. The obtained results in combination with similar ones from the literature can be applied to the analysis of metal forming processes with dominant tensile deformation (e.g., drawing, deep drawing, stripdrawing, ironing)

X-ray resonant photoexcitation: line widths and energies of K{\alpha} transitions in highly charged Fe ions

Photoabsorption by and fluorescence of the K{\alpha} transitions in highly charged iron ions are essential mechanisms for X-ray radiation transfer in astrophysical environments. We study photoabsorption due to the main K{\alpha} transitions in highly charged iron ions from heliumlike to fluorinelike (Fe 24+...17+) using monochromatic X-rays around 6.6 keV at the PETRA III synchrotron photon source. Natural linewidths were determined with hitherto unattained accuracy. The observed transitions are of particular interest for the understanding of photoexcited plasmas found in X-ray binaries and active galactic nuclei.Comment: Revised versio

The landscape of a Swedish boat-grave cemetery

This is the published PDF version of an article published in Landscapes© 2010. The definitive version is available at http://www.maneyonline.com/toc/lan/11/1The paper integrates topographical and experiential approaches to the mortuary landscape of a Viking period inhumation-grave excavated in 2005 within the cemetery at Skamby, Kuddy parish, Östergötland province, Sweden. We argue that the landscape context was integral to the performance of the funerary ceremonies and the subsequent monumental presence of the dead in the landscape. We offer a way to move beyond monocausal explanations for burial location based on single-scale analyses. Instead, we suggest that boat-inhumation at Skamby was a commemorative strategy that operated on multiple scales and drew its significance from multiple landscape attributes.British Academ

Classificatory Theory in Data-Intensive Science: The Case of Open Biomedical Ontologies

publication-status: Publishedtypes: ArticleThis is the author's version of a paper that was subsequently published in International Studies in the Philosophy of Science. Please cite the published version by following the DOI link.Knowledge-making practices in biology are being strongly affected by the availability of data on an unprecedented scale, the insistence on systemic approaches and growing reliance on bioinformatics and digital infrastructures. What role does theory play within data-intensive science, and what does that tell us about scientific theories in general? To answer these questions, I focus on Open Biomedical Ontologies, digital classification tools that have become crucial to sharing results across research contexts in the biological and biomedical sciences, and argue that they constitute an example of classificatory theory. This form of theorizing emerges from classification practices in conjunction with experimental know-how and expresses the knowledge underpinning the analysis and interpretation of data disseminated online.Economic and Social Research Council (ESRC)The British AcademyLeverhulme Trus

Secondary Endoleak Management Following TEVAR and EVAR.

Endovascular abdominal and thoracic aortic aneurysm repair and are widely used to treat increasingly complex aneurysms. Secondary endoleaks, defined as those detected more than 30 days after the procedure and after previous negative imaging, remain a challenge for aortic specialists, conferring a need for long-term surveillance and reintervention. Endoleaks are classified on the basis of their anatomic site and aetiology. Type 1 and type 2 endoleaks (EL1 and EL2) are the most common endoleaks necessitating intervention. The management of these requires an understanding of their mechanics, and the risk of sac enlargement and rupture due to increased sac pressure. Endovascular techniques are the main treatment approach to manage secondary endoleaks. However, surgery should be considered where endovascular treatments fail to arrest aneurysm growth. This chapter reviews the aetiology, significance, management strategy and techniques for different endoleak types

Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, Megalopta genalis (Halictidae)

Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis

Matter in Strong Magnetic Fields

The properties of matter are significantly modified by strong magnetic fields, $B>>2.35\times 10^9$ Gauss ($1 G =10^{-4} Tesla$), as are typically found on the surfaces of neutron stars. In such strong magnetic fields, the Coulomb force on an electron acts as a small perturbation compared to the magnetic force. The strong field condition can also be mimicked in laboratory semiconductors. Because of the strong magnetic confinement of electrons perpendicular to the field, atoms attain a much greater binding energy compared to the zero-field case, and various other bound states become possible, including molecular chains and three-dimensional condensed matter. This article reviews the electronic structure of atoms, molecules and bulk matter, as well as the thermodynamic properties of dense plasma, in strong magnetic fields, $10^9G << B < 10^{16}G$. The focus is on the basic physical pictures and approximate scaling relations, although various theoretical approaches and numerical results are also discussed. For the neutron star surface composed of light elements such as hydrogen or helium, the outermost layer constitutes a nondegenerate, partially ionized Coulomb plasma if $B<<10^{14}G$, and may be in the form of a condensed liquid if the magnetic field is stronger (and temperature $<10^6$ K). For the iron surface, the outermost layer of the neutron star can be in a gaseous or a condensed phase depending on the cohesive property of the iron condensate.Comment: 45 pages with 9 figures. Many small additions/changes. Accepted for publication in Rev. Mod. Phy

The IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array: Joint Contribution to the 34th International Cosmic Ray Conference (ICRC 2015)

We have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube `high-energy starting events' sample and the other with 16 high-energy `track events'. The angular separation between the arrival directions of neutrinos and UHECRs is scanned over. The same events are also used in a separate search using a maximum likelihood approach, after the neutrino arrival directions are stacked. To estimate the significance we assume UHECR magnetic deflections to be inversely proportional to their energy, with values $3^\circ$, $6^\circ$ and $9^\circ$ at 100 EeV to allow for the uncertainties on the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube sample of through-going muon track events which were optimized for neutrino point-source searches.Comment: one proceeding, the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands; will appear in PoS(ICRC2015