Mechanical and microstructural features of plasma cut edges in a 15 mm thick S460M steel plate

In general, the thermal cutting processes of steel plates are considered to have an influence on microstructures and residual stress distribution, which determines the mechanical properties and performance of cut edges. They also affect the quality of the surface cut edges, which further complicates the problem, because in most cases the surface is subjected to the largest stresses. This paper studies the influence of plasma cutting processes on the mechanical behavior of the cut edges of steel and presents the characterization results of straight plasma arc cut edges of steel plate grade S460M, 15 mm thick. The cutting conditions used are the standard ones for industrial plasma cutting. The metallography of CHAZ (Cut Heat Affected Zones) and hardness profiles versus distance from plasma cut edge surface are tested; the mechanical behavior of different CHAZ layers under the cut edge surface were obtained by testing of instrumented mini-tensile 300 µm thick specimens. Also, the residual stress distribution in the CHAZ was measured by X-ray diffraction. The results for the mechanical properties, microstructure, hardness, and residual stresses are finally compared and discussed. This work concludes that the CHAZ resulting from the plasma cutting process is narrow (about 700 µm) and homogeneous in plate thickness

Fatigue Behavior of High Strength Steel S890Q Containing Thermally Cut Straight Edges

This paper evaluates the effect of different thermal cutting methods on the fatigue life of high strength steel S890Q. The investigation covers flame, plasma and laser cutting methodologies, and specimens with rectangular sections and cut straight edges. The experimental program is composed of 30 specimens that were conducted to failure by applying fatigue cycles with a stress ratio (R) of 0.1 in a high frequency testing machine. The resultant best-fit S-N curves have been compared, revealing a better performance for laser cut straight edges. Moreover, the corresponding Eurocode 3 FAT class has been derived for each of the three cutting methods, resulting in FAT160 in all cases. This suggests that the use Eurocode 3 FAT125, which is the fatigue class currently provided for flame cut straight edges, is an overconservative assumption for thermally cut straight edges in steel S890Q, regardless of the thermal cutting technique being used (flame, laser or plasma)

Local functional models of critical correlations in thin-films

Recent work on local functional theories of critical inhomogeneous fluids and Ising-like magnets has shown them to be a potentially exact, or near exact, description of universal finite-size effects associated with the excess free-energy and scaling of one-point functions in critical thin films. This approach is extended to predict the two-point correlation function G in critical thin-films with symmetric surface fields in arbitrary dimension d. In d=2 we show there is exact agreement with the predictions of conformal invariance for the complete spectrum of correlation lengths as well as the detailed position dependence of the asymptotic decay of G. In d=3 and d>=4 we present new numerical predictions for the universal finite-size correlation length and scaling functions determining the structure of G across the thin-film. Highly accurate analytical closed form expressions for these universal properties are derived in arbitrary dimension.Comment: 4 pages, 1 postscript figure. Submitted to Phys Rev Let

Adaptive Radiation within Marine Anisakid Nematodes: A Zoogeographical Modeling of Cosmopolitan, Zoonotic Parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area

Fatigue performance of thermally cut bolt holes in structural steel S460M

Current fatigue codes only consider the fatigue performance of drilled and punched holes, limiting the use of thermal cutting processes to produce bolt holes. This paper studies the fatigue performance of structural steel S460M plates containing thermally cut bolt holes. The research covers three thermal cutting methods: the traditional one (oxy-fuel cutting) and two more modern processes (plasma and laser cutting). Specimen geometry is defined by a rectangular cross section with a cut hole in the middle. All the specimens were conducted to failure by applying fatigue cycles, the stress ratio (R) being 0.1. The corresponding S-N curve and fatigue limit were obtained for each cutting method. Fatigue results have been compared with previous researches on fatigue performance of drilled and punched holes, and with the predictions provided by current fatigue standards, analyzing the possibility to extrapolate their S-N curves, focused on drilled and punched holes, to thermally cut holes

Polymer depletion interaction between two parallel repulsive walls

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic polymers [D. Rudhardt, C. Bechinger, and P. Leiderer, Phys. Rev. Lett. 81, 1330 (1998)].Comment: 17 pages, 3 figures. Final version as publishe

Ductilidad y tenacidad de un borde cortado por plasma en una chapa de acero S460M de 15 mm de espesor

Los procesos de corte (y soldadura) son sin duda traumáticos para la microestructura de los materiales, de los que se deriva su comportamiento mecánico. Además esto afecta a la superficie, lo que agrava el problema, pues con frecuencia son las zonas que soportan unos mayores esfuerzos. En este trabajo se propone determinar si un corte por plasma mejora o no su comportamiento mecánico (fundamentalmente de cara a su comportamiento en fatiga bajo cargas alternadas). Se presentan los resultados de la caracterización de un borde cortado por plasma en condiciones industriales. La chapa es de acero S460M de 15 mm de espesor. Se discute la rugosidad superficial introducida en la superficie del borde de corte, la metalografía de la Zona Afectada por el Calor/Corte, el perfil de durezas que se introduce en el material, el comportamiento mecánico del material a diferentes distancias medidas desde la superficie del corte, que se obtiene realizando ensayos de tracción de miniprobetas instrumentadas con bandas. También se presentan las medidas de tensiones residuales, obtenidas mediante difracción de rayos X y se compara el conjunto de resultados.In general, thermal cutting processes of steel plates are considered to have an influence on microstructures and residual stresses distribution, which determines the mechanical properties of cut edges. It also affects the quality of the surface of cut edges, which complicates even more the problem, because in most cases the surface is subjected to the larger stresses. This work deals with the question of whether a plasma arc cutting process has influence on the mechanical behavior of cut edges of steel plate (basically from its future fatigue behavior under alternating loading conditions). The paper presents the characterization results of straight plasma arc cut edges of steel plate grade S460M 15 mm thick, under standard industrial plasma arc cutting conditions. The surface roughness Rz5 of plasma arc cut edges is measured, the metallography of Cut-HAZ (Heat Affected Zone) of cut edges and hardness profiles versus distance from plasma cut edge surface are tested; the mechanical behavior of different CHAZ layers under the cut edge surface, obtained by testing of instrumented (with strain gauges) mini-tensile specimens. Also residual stresses distribution in CHAZ of cut edges is measured by X-ray diffraction and all results are compared

Quantum Quenches in Extended Systems

We study in general the time-evolution of correlation functions in a extended quantum system after the quench of a parameter in the hamiltonian. We show that correlation functions in d dimensions can be extracted using methods of boundary critical phenomena in d+1 dimensions. For d=1 this allows to use the powerful tools of conformal field theory in the case of critical evolution. Several results are obtained in generic dimension in the gaussian (mean-field) approximation. These predictions are checked against the real-time evolution of some solvable models that allows also to understand which features are valid beyond the critical evolution. All our findings may be explained in terms of a picture generally valid, whereby quasiparticles, entangled over regions of the order of the correlation length in the initial state, then propagate with a finite speed through the system. Furthermore we show that the long-time results can be interpreted in terms of a generalized Gibbs ensemble. We discuss some open questions and possible future developments.Comment: 24 Pages, 4 figure

Propiedades mecánicas de las zonas afectadas por un corte láser, corte por plasma y oxicorte de una chapa de acero S460M de 15 mm de espesor

Se presentan los mini ensayos de tracción realizados sobre láminas extraídas en las zonas afectadas por el corte de una chapa de acero S460M de 15 mm de espesor. Los cortes se realizan tanto por láser como por plasma y oxicorte. Se extraen miniprobetas de tracción a diferentes distancias del borde de corte, determinándose cómo varía el límite elástico, la carga de rotura, alargamiento, índice de endurecimiento en función de la profundidad y las diferentes técnicas de corte. Se comparan las profundidades afectadas por el corte y su relación con la microestructura y microdurezas.Mini-tensile tests results are presented. Mini-tensile probes are extracted from Cut Heat-Affected Zones from the cut edge a S460M steel plate with a thickness of 15 mm. Cuts were done by laser beam, plasma arc and oxy-fuel. Minitensile test-piece were extracted at different distances from the cut edge. Yield stress, ultimate tensile strength, elongation, hardening index were obtained vs. distance from cut edge for the different thermal cutting techniques. Comparisons are made of the depth of Cut Heat-Affected Zones and their relation with microstructure and microhardness measurements

Efecto del método de corte sobre el comportamiento a fatiga de un acero estructural de alta resistencia S690Q

Este artículo estudia el efecto de los diferentes métodos de corte térmico en la vida a fatiga de un acero estructural de alta resistencia S690Q. Se han seleccionado tres sistemas de corte térmico mecanizado ampliamente utilizados en la industria (oxicorte, corte por plasma y corte por láser) y dos detalles estructurales: bordes rectos cortados térmicamente y orificios obtenidos mediante corte térmico para su posterior empleo en uniones atornilladas. El programa experimental está constituido por 60 probetas, las cuales se han llevado a rotura por fatiga en una máquina de resonancia. El valor de la relación de tensiones (R) seleccionado es igual a 0.1. Por cada combinación de método de corte y detalle estructural se ha obtenido su correspondiente curva S-N y límite de fatiga. Se ha llevado a cabo un análisis de la rugosidad superficial y dureza de la Zona Afectada Térmicamente con objeto de determinar la influencia de los métodos de corte térmico en la vida en fatiga. Los resultados obtenidos se comparan con los valores de diseño propuestos por las normativas de diseño en fatiga, evaluando la posibilidad de extrapolar sus curvas S-N tanto a bordes rectos como agujeros cortados mediante cualquiera de los tres sistemas de corte térmico.This paper analyses the effect of different cutting methods on the fatigue life of high strength steel S690Q. The research covers three cutting methods (oxy-fuel, plasma and laser) and two specimen geometries: plain specimens with rectangular sections and cut edges, and specimens with machined edges and a cut hole in the middle section. All the specimens were conducted to failure by applying fatigue cycles, the stress ratio (R) being 0.1, and the corresponding SN curves were obtained for each combination of cutting method and specimen geometry. Measurements of roughness and hardness have been performed in order to explain the influence of the cutting method on the fatigue life of this particular steel. Fatigue results have been compared with the predictions provided by current fatigue standards, analysing the possibility of extrapolating their S-N curves, focused on oxy-fuel cuts, to plasma and laser cuts.HIPERCUT: High Performance Cut Edges in Structural Steel Plates for Demanding Aplication