Revistas
Autores:
Bergara, A. (Autor de correspondencia); Dorado, J. I. ; Martín, Antonio; et al.
Revista:
MECHANICS OF ADVANCED MATERIALS AND STRUCTURES
ISSN:
1537-6494
Año:
2021
Vol.:
28
N°:
8
Págs.:
861-873
This work presents the numerical modeling and validation of two different fatigue propagation tests that attempt to simulate the crack growth situation that takes place at aeronautic engine vane guides. These vanes, which are cylindrical skins of very thin thickness (few millimeters), are responsible for holding the static blades of both the compressor and the turbine. The union of discs and blades is a very conflictive zone due to high stresses and possible manufacturing defects. The first test designed for this work tries to reproduce crack growth at geometric discontinuities and sharp edges, such as the union between the disc and the blades. The second test tries to reproduce the crack growth situation that takes place in skins of very thin thickness, such as vane guides. First, the experimental set-ups as well as the experimental results are presented. Then, the numerical FE models and simulations -corresponding to the experimental tests that have been performed- are explained. Finally, the comparison between the experimental and numerical results is presented. Crack growth was controlled by optical microscopy and by progressive crack surface heat-tinting. For the numerical simulations, the Extended Finite Element Method (XFEM) implemented in Abaqus (R) 2017 software has been used. The comparison between the experimental and numerical results shows very good correlation regarding crack shape and number of cycles until failure. The capabilities of the XFEM-based LEFM approach to simulate fatigue crack growth in complex crack fronts are validated.
Revista:
INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HARD MATERIALS
ISSN:
0958-0611
Año:
2018
Vol.:
70
Págs.:
45 - 55
Six suppliers from several countries were asked to furnish parallelepiped 10 × 30 × 80 mm3 samples of commercial purity tungsten machined from rolled plates in view of selecting a provider of tungsten bricks for the target of the European neutron spallation source, ESS, under construction in Lund (Sweden). Sample surfaces were to be ground and free from visible defects or oxidation. The material should be rolled after sintering. A minimum room temperature tensile strength of 600 MPa was specified. The samples were submitted to different blind mechanical tests, measurement of physical properties and structural observations in order to assess their suitability for the application. We present here a summary of their main measured properties. The dispersion of results is noteworthy; the exercise allowed to sort-out technically eligible candidates for the application.
Revista:
ANALES DE LA MECANICA DE LA FRACTURA
ISSN:
0213-3725
Año:
2018
Vol.:
35
Págs.:
52 - 57
La vida a fatiga de los componentes aeronáuticos rotativos que trabajan a elevadas temperaturas dentro de la turbina de
un motor de aviación es un factor crítico de diseño. Las condiciones en las que se mecanizan componentes como los
discos de turbina en estas aleaciones de base níquel, por ejemplo, discos de turbina, afectan a su posterior vida en servicio.
Los procesos de mecanizado de distintas zonas (torneado, brochado¿) afectan a la rugosidad superficial, daño y capa
superficial deformada (incluyendo los efectos de posibles carburos rotos) y a la distribución de las tensiones residuales
próximas a la superficie. Por añadidura, es posible aplicar o no un tratamiento posterior de granallado que modifica la
integridad superficial. El propósito de este trabajo es ser capaz de separar los efectos que tienen las diferentes variables:
rugosidad, espesor de la capa afectada por el mecanizado y las tensiones residuales; de modo que se puedan optimizar
tanto las condiciones del mecanizado como la vida en fatiga de los componentes.
Revista:
METALS
ISSN:
2075-4701
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 mu m 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 mu m) and homogeneous in plate thickness.
Autores:
Klimpel, A. ; Cholewa, W.; Bannister, A.; et al.
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2017
Vol.:
92
N°:
1 - 4
Págs.:
699 - 713
The paper deals with experimental investigations of the influence of laser beam and plasma arc cutting parameters on edge quality of a range of steel grades and thicknesses. Based on the experimental results, a variety of methods have been taken to carry out the analysis of influence of laser beam and plasma arc cutting parameters on the quality and mechanical properties of cut edges of selected high-strength low-alloy (HSLA) strips and plates. In this study, three approaches were investigated corresponding to rank correlation analysis, multidimensional data analysis and decision trees. These techniques were able to elucidate the most relevant cutting parameters as well as the optimal field of values of these parameters to give the required geometrical and mechanical quality levels. As a result of this study, general rules in the form of cutting procedure specifications were established. This was needed to describe the relation between laser beam or plasma arc cutting parameters and the geometrical and mechanical quality factors of cut edges of different medium- and high-strength steel materials. The proposed rules can be also adopted for providing a comparison between the surface qualities achievable by the different combinations of cutting parameters for laser beam and plasma arc cutting processes of medium- and high-strength steels.
Autores:
Cicero, S.; Garcia, T.; Alvarez, J.; et al.
Revista:
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH
ISSN:
0143-974X
Año:
2017
Vol.:
128
Págs.:
74 - 83
Thermal cutting includes oxy-fuel, plasma and laser cut technologies. These cutting methods generate cut surfaces and material transformations that determine the final fatigue behaviour of cut structural components. The BS7608, like most of the standards, does not provide fatigue design curves for thermally cut holes, restricting its scope to drilled or reamed holes. This limits the use of oxy-fuel, plasma and laser technologies in numerous engineering applications. This research analyses the effett of the three thermal cutting methods on the fatigue behaviour of cut holes performed on a wide range of structural steels (S355M, 5460M, S690Q and S890Q). The experimental fatigue results obtained have been used to generate the corresponding BS7608 design classes, which have also been validated by comparing them to experimental data found in the literature. (C) 2016 Elsevier Ltd. All rights reserved.
Revista:
INTERNATIONAL JOURNAL OF FATIGUE
ISSN:
0142-1123
Año:
2017
Vol.:
103
Págs.:
112 - 121
This work presents the numerical simulation and validation of a fatigue propagation test of a semi elliptical crack located at the side of the rectangular section of a beam subjected to four-point bending. For most common fatigue test configurations there are equations that allow calculating the stress intensity factors (SIFs). However, no solution is provided if the crack is located on any of the lateral sides of the rectangular section, since one part of the crack is located in the tractive zone while the other is at the compressive zone. In these cases, it is necessary to use alternative methods. The Extended Finite Element Method (XFEM) provides a new alternative for the calculation of SIFs, and to simulate crack propagation, by using special interpolation functions. Furthermore, XFEM-based LEFM approach offers the advantage of performing crack growth analysis without the need for updating the mesh (re meshing). The experimental tests have been carried out in an Instron 8874 biaxial testing machine. Crack growth was controlled by optical microscopy and by progressive crack surface heat tinting. For the numerical simulations, the Extended Finite Element Method (XFEM) implemented in the Abaqus (R) 2017 software has been used. The comparison between the experimental and numerical results shows very good correlation regarding crack shape and number of cycles to failure. The capabilities of the XFEM-based LEFM approach to simulate fatigue crack growth in complex crack fronts are validated. (C) 2017 Elsevier Ltd. All rights reserved.
Autores:
Andres, D.; Garcia, T.; Cicero, S.; et al.
Revista:
MATERIALS CHARACTERIZATION
ISSN:
1044-5803
Año:
2016
Vol.:
119
Págs.:
55 - 64
Thermal cutting processes introduce changes in the heat affected zone (HAZ), which can lead to a significant reduction of the service life of components. In order to assess their influence, different cutting processes have been analysed on a structural steel. The characterization of the reduced volumes of HAZ posed a major challenge, since conventional techniques require greater pieces of material. Alternative miniature techniques had to be applied, such as Small Punch tests and microhardness measurements, from which the material tensile properties and fracture toughness values have been obtained. Results show that oxyfuel HAZ exhibit minor alterations of the material, while plasma cutting seems to improve the material tensile properties and fracture toughness. Besides, the suitability and accuracy of the Small Punch technique for similar applications can be derived from this work, turning it into a promising candidate to perform integrity assessments of actual components. (C) 2016 Elsevier Inc All rights reserved.
Autores:
Cicero, S.; Garcia, T.; Alvarez, J.; et al.
Revista:
INTERNATIONAL JOURNAL OF FATIGUE
ISSN:
0142-1123
Año:
2016
Vol.:
87
Págs.:
50 - 58
When the fatigue behaviour of structural components containing holes is analysed, Eurocode 3 only considers the fatigue performance of drilled holes, limiting the use of thermal cutting processes to produce, for example, bolt holes. This paper studies the fatigue performance of structural steel plates containing thermally cut holes. The research covers three thermal cutting methods: the traditional one (oxy-fuel cutting) and two more modern processes (plasma and laser cutting). An experimental program composed of 150 fatigue specimens has been completed, combining four steels (S355M, 5460M, S690Q and S890Q), the three thermal cutting methods and two different thicknesses (15 mm and 25 mm). The S-N results obtained have been used to estimate the corresponding Eurocode 3 FAT classes, which have finally been validated by comparing them to additional experimental data found in the literature. (C) 2016 Elsevier Ltd. All rights reserved.
Autores:
Cicero, S.; Garcia, T.; Alvarez; J.; et al.
Revista:
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH
ISSN:
0143-974X
Año:
2016
Vol.:
120
Págs.:
221 - 231
Thermal cutting, which includes oxy-fuel, plasma and laser cut technologies, is frequently used in engineering practice to obtain the final shape of structural components. These cutting methods generate cut surfaces and material transformations that determine the final fatigue behaviour. Nevertheless, in practice, design codes such as the BS7608 provide fatigue design curves for oxy-fuel cuts, while other relevant technologies such as plasma and laser cutting are not generally covered, something that limits their use in many engineering applications. This research analyses the effect of the three above mentioned thermal cutting methods on the fatigue behaviour of cut straight edges performed on a wide range of structural steels (5355M, S460M, 5690Q and S890Q). The S-N results obtained have been used to derive the corresponding BS7608 design classes, which have been finally validated by comparing them to numerous experimental data found in the literature. (c) 2016 Elsevier Ltd. All rights reserved.
Autores:
Cicero, S. (Autor de correspondencia); García, T.; Alvarez; J.A.; et al.
Revista:
PROCEDIA ENGINEERING
ISSN:
1877-7058
Año:
2016
Vol.:
160
Págs.:
246 - 253
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).
Autores:
Cicero, S.; Garcia, T.; Alvarez, J.; et al.
Revista:
ENGINEERING STRUCTURES
ISSN:
0141-0296
Año:
2016
Vol.:
111
Págs.:
152 - 161
Thermal cutting is commonly used in engineering practice to obtain the final shape of structural components, and includes oxy-fuel, plasma and laser cut technologies. The characteristics of the cut surface and the material transformations caused by these cutting methods determine the corresponding fatigue behaviour. However, in the case of thermally cut straight edges, design codes, including the Eurocode 3, provide fatigue design curves for oxy-fuel cuts, whereas emergent technologies such as plasma and laser cutting are not associated to any design curve, limiting their use in many engineering applications. This paper analyses the effect of oxy-fuel cutting, plasma cutting and laser cutting on the fatigue behaviour of cut straight edges performed on structural steels S355M, S460M, S690Q and S890Q An experimental programme composed of 150 fatigue specimens has been completed, combining the four steels, the three thermal cutting methods and two different thicknesses (15 mm and 25 mm). The obtained S-N results have been used to estimate the corresponding Eurocode 3 FAT classes, which have been finally validated by comparing them to numerous experimental data found in the literature. (C) 2015 Elsevier Ltd. All rights reserved.
Revista:
EXPERIMENTAL TECHNIQUES
ISSN:
0732-8818
Año:
2016
Vol.:
40
N°:
2
Págs.:
777 - 787
Thermomechanical fatigue (TMF) tests are carried out in order to characterize the behavior of turbine blades and vanes materials: superalloys. These materials suffer high stress levels at very high temperature and to simulate these extreme operation conditions a test-piece is subjected to controlled thermal and mechanical strain waveforms. In this paper, a test procedure is explained, which is unusual due to the fact that the heating system is based on direct resistance method and temperature is controlled by means of a pyrometer. For this purpose, emissivity evolution was studied. The effectiveness of the method, as well as some other important aspects such as alignment and a proper thermal-mechanical strain decoupling are discussed. Finally, some preliminary results of the cyclic behavior and life prediction of C-1023 nickel base superalloy are introduced. This also includes an analysis of specimens fractography.
Revista:
MECHANICS OF MATERIALS
ISSN:
0167-6636
Año:
2015
Vol.:
83
Págs.:
103 - 109
Recent biaxial experiments on clear-spruce wood allow to have a more complete understanding of fracture behavior of wood. An elliptic failure surface, like that of Tsai¿Wu, has been previously proposed as a failure surface. Previous works in this area have shown the need for further developments. In this study a new failure model that accounts for existing different couplings and interactions in the longitudinal compressive and tensional domains is presented. The model is based on the fracture behavior of clear spruce wood and related experimental works. The model is more accurate compared to existing phenomenological models.
Autores:
Garcia, T.; Cicero, S.; Ibañéz, F.T.; et al.
Revista:
PROCEDIA ENGINEERING
ISSN:
1877-7058
Año:
2015
Vol.:
133
Págs.:
590 - 602
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 S460 M 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.
Revista:
MATERIALS AT HIGH TEMPERATURES
ISSN:
0960-3409
Año:
2013
Vol.:
30
N°:
1
Págs.:
19 - 26
Thermo-mechanical fatigue tests were carried out in MarM-247 nickel-based superalloy with a system that uses the direct resistance method for heating, instead of the common induction system. Therefore, this paper has two aims: (1) to validate the test facility via an inter-comparison exercise (carried out at BAM) and (2) to give an overview of the material behaviour based on cyclic response, lifetime and some microstructural aspects. In-phase (IP), out-of-phase (OP) and in-phase test with 2 minutes of dwell period (IP dwell) were executed. Ostergren and Zamrik life prediction approaches were found to be suitable tools for life assessment regardless of the test-type. In fact, some modifications in the mentioned models allow predicting life within a factor of two of the unit correlation line. Apart from that, microstructural investigations reveal that IP tests are prone to intergranular fracture whereas in OP tests trangranular fracture prevails given a clear indication of the prevailing damage mechanisms.
Revista:
EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS
ISSN:
0018-3768
Año:
2012
Vol.:
70
N°:
6
Págs.:
871 - 882
Many different phenomenological failure criteria have been proposed. These type of criteria do not explain the mechanism of failure itself. They merely identify failure (yes or no) and are usually regarded in practice as a simple and reliable tool for design. Most of them were developed for composite materials, but are extensively applied for wood. In this study, existing phenomenological strength criteria for orthotropic materials were applied to clear wood data. Instead of fitting the criteria to available experimental data, the criteria were used to predict failure of biaxial tests based on uniaxial strength. This procedure is closer to practice, and hence an answer to the question "is there any reliable failure criterion for wood?" Predictability of the criteria was assessed using normalisation procedure, and statistical significance of the difference of the means analysed. Based on the results, it can be concluded that a general criterion cannot be applied to predict failure, but should be chosen according to the biaxial stress state.
Revista:
ANALES DE LA MECANICA DE LA FRACTURA
ISSN:
0213-3725
Año:
2011
Vol.:
28
Págs.:
39 - 44
En la primera parte de este trabajo se realiza una revisión de los distintos modelos de fallo de la madera en estados de carga multiaxial propuestos hasta el momento. A continuación se hace un análisis estadístico del ajuste de dichos criterios a resultados experimentales, encontrados en la literatura, de ensayos realizados en madera de abeto blanco bajo distintas condiciones de carga. Finalmente se propone un nuevo criterio de fallo no continuo con el cual, sin aumentar el número de parámetros requeridos por otros criterios, se obtiene un mejor ajuste a los datos experimentales.
Revista:
MATHEMATICS AND COMPUTERS IN SIMULATION
ISSN:
0378-4754
Año:
2011
Vol.:
81
N°:
11
Págs.:
2564 - 2580
Liquid-phase sintering (LPS) is a consolidation process for metallic and ceramic powders. At given temperature conditions, the process occurs with constant amount of liquid phase. However, the evolution of solid-particle shape is observed, namely, the rounding of particles and the growth of big particles at the expense of the small ones, which is known as Ostwald ripening. In this work, we propose a Monte Carlo (MC) model to simulate the microstructural evolution during LPS. The model considers the change of state of the discretising elements, namely voxels, of the system. The microstructural evolution proceeds accounting for both the geometrical characteristics of the particles, such as the number of solid neighbours, and the amount of solute contained in or surrounding a randomly chosen voxel. This has been implemented in terms of two probability distribution functions (PDFs). The diffusion of solute has also been considered by means of the implementation of a three-dimensional finite-difference algorithm. The diffusional MC model that we present is able to reproduce the Ostwald ripening behaviour and, in particular, results match the case in which the process is limited by the diffusion of the solute in the liquid phase. (C) 2011 IMACS. Published by Elsevier B.V. All rights reserved.
Autores:
Perez, M.; Gubeljak, N.; Porter, D.; et al.
Revista:
TEHNICKI VJESNIK-TECHNICAL GAZETTE
ISSN:
1330-3651
Año:
2011
Vol.:
18
N°:
4
Págs.:
561 - 569
In the present investigation, the effect of both: rolling parameters (2 reduction rates and 3 cooling rates) and chemical elements such as: C, Mn, Nb, Ti, Mo, Ni, Cr, Cu and B, has been studied in relation to strength properties in low-carbon microalloyed steels with high niobium contents (up to 0,12 wt.% Nb). For this purpose, an experimental set-up was designed based on an intelligent design of experiments (DoE), resulting in 26 casts (laboratory casts). A combination of metallography, Electron Back-Scattered Diffraction (EBSD) and tensile tests have been performed to study how processing parameters and chemical composition affect the strength. The results, where the proof stress, tensile strength, uniform and fracture elongations are the response variables, have been analysed statistically by means of multiple linear regression technique, leading to response equations. From the results, it was found that the effectiveness of niobium increasing the strength is reduced as carbon content increases.
Revista:
MATHEMATICS AND COMPUTERS IN SIMULATION
ISSN:
0378-4754
Año:
2010
Vol.:
80
N°:
7
Págs.:
1469 - 1486
Liquid-phase sintering (LPS) is an industrial process used to consolidate materials composed of two different kinds of metallic and/or ceramic powders. At constant temperature, the amount of the present liquid-phase is constant However, the shape of particles of solid phase changes over time In general, the rounding of particles and the growth of big particles at the expense of the small ones are observed This process is known as Ostwald ripening. In this work, we propose a Monte Carlo (MC) model to simulate the microstructural evolution during LPS The discretizing elements of the system. namely the voxels. change state between solid and liquid. according to previously defined melting and solidification probability distribution functions (PDFs) The generated PDFs take into account the geometrical characteristics of the system particles in terms of number of solid neighbours that surround a randomly chosen voxel The geometrical MC model that we present is able to reproduce the Ostwald ripening behaviour and, in particular, matches the case in which the process occurs limited by the attachment/detachment of the solid phase to/from the surface of the particle (C) 2009 IMACS Published by Elsevier B V All rights reserved.
Revista:
ENGINEERING FAILURE ANALYSIS
ISSN:
1350-6307
Año:
2010
Vol.:
17
N°:
1
Págs.:
48 - 60
What is the optimum cross-section for a compression member built by bending a plate of a given thickness and area? It is shown that a parabolic shape is 41% better than a tubular section. A number of examples are shown where this section is found in nature. (C) 2008 Elsevier Ltd. All rights reserved.