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.

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.

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.

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.

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.

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.

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.

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.

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.

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.