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The American standard ASTM E837 presents a standard procedure to determine residual stresses in isotropic materials using the incremental hole drilling technique (IHD). The standard, however, presents limitations regarding its applicability, such as those related with the thin thickness of the samples. According to this standard, in depth non uniform residual stresses can only be determined, roughly, in plates where the thickness is greater than the mean diameter of the strain gage rosette used. This limitation excludes important experimental cases and, therefore, deserves to be investigated. In this work this limitation is numerically and experimentally investigated in detail, considering the case of residual stresses induced by laser shock peening (LSP) in aluminum alloy 7075-T651 plates. The obtained results using the incremental hole drilling technique (IHD), based on the integral method, are benchmarked against the results of several diffraction techniques, used as reference, and a procedure to correct the experimentally determined strain-depth relaxation curves, to accurately still apply the ASTM E837 standard procedure is discussed and validated.

Oxygen uptake efficiency slope during submaximal tests has been proposed as a more appropriate measure of aerobic capacity after suffering a stroke, since some individuals cannot tolerate maximal exercise testing. However, it has not yet been investigated whether the oxygen uptake efficiency slope is able to differentiate between healthy individuals and those who have suffered a stroke.To compare the oxygen uptake efficiency slope during walking and stair climbing between stroke survivors and age- and sex-matched healthy controls.This is a cross-sectional study in which 18 individuals who had suffered a stroke (stroke survivors) and 18 healthy controls matched for sex and age were included. Oxygen consumption and minute ventilation were collected breath-by-breath during walking (6-min Walk Test) and stair climbing. The oxygen uptake efficiency slope was estimated by the slope of the line obtained through linear regression.The stroke survivors had a lower oxygen uptake efficiency slope during the 6-min Walk Test than the healthy controls (MD 498, 95% CI 122 to 873,Stroke survivors had lower oxygen uptake efficiency slope during the performance of the 6-min Walk Test when compared to sex- and age-matched healthy controls. This suggests that stroke survivors have worse cardiopulmonary capacity.

To determine whether minute ventilation-to-carbon dioxide production (VE/VCORegression analysis of cross-sectional data from 50 individuals between 1 and 4 years post-stroke was carried out to investigate the prediction of energy expenditure during stair ascent/descent. In addition, discriminant analysis was carried out to investigate the discrimination between walking abilities for energy expenditure: community (walking speed ≥ 0.8 m/s) and non-community (walking speed0.8 m/s) walkers.Oxygen pulse and rate pressure product were retained in the model. Oxygen pulse alone explained 70% of the variance in energy expenditure during stair ascent/descent. By adding rate pressure product, 79% of the variance was explained. Energy expenditure was able to discriminate the community from the non-community walkers, with a cutoff value of 13.8 ml∙kgOxygen pulse and rate pressure product significantly predicted energy expenditure during stair ascent/descent in individuals with chronic stroke. Energy expenditure during stair ascent/descent discriminated community from non-community walkers.

Recently opened for users at LNF XLab-Frascati a μ XRF station, named “Rainbow X-ray” – RXR, has been optimized for most of X-ray analytical research fields. The basic principle of the station is in the use of various geometrical combinations of polycapillary optics for X-ray beam shaping (focusing/collimation) at specially designed laboratory unit. In this work we have presented the results of archaeological studies on the artifacts of Paleolithic period and Iron Age (9th century BC to the midway of the 8th BC). The elemental analysis of these artifacts has been first performed by compact laboratory setup. Superficial (2D) and bulk (3D) micro-fluorescence mapping provides useful informations for the geologists in order to identify the possible artifacts provenience and origin. The results presented in this work are a part of wider anthropological/archeological investigations aimed at the understanding of social and economical relations of prehistorical communities.

The focus of this paper is on the use of the Laser Shock Peening (LSP) process, and the strategy with which it is employed, to retard fatigue cracks in thin metallic airframe structural panels. This approach allows for the extension of component life in both design and maintenance applications. LSP was carried out without an ablative coating. Various compressive residual stress fields were created by using different laser parameter sets, through the variation of power intensity and coverage. These were quantified using X-Ray Diffraction and Incremental Hole Drilling techniques. The size and position of the peened region was considered in order to balance induced compressive residual stresses and the resulting tensile residual stresses to obtain improved fatigue life and damage tolerance. The investigation was carried out using analytical fracture mechanics code AFGROW and validated through experimentation. Applying LSP to a pre-cracked aluminium panel provided clear retardation of the crack front as it propagated through the processed region. Decreasing the offset of the LSP region from the centre of the panel and increasing the width of the LSP region improved the results. The best configuration, a 15 mm wide LSP region with a 15 mm offset from the crack tip, yielded a fatigue life of more than 6 times the baseline fatigue value.

Airborne dust extracted from deep ice core perforations can provide chemical and mineralogical insight into the history of the climate and atmospheric conditions, with unrivalled temporal resolution, time span and richness of information. The availability of material for research and the natural complexity of the particulate, however, pose significant challenges to analytical methods. We present the developments undertaken to optimize the experimental techniques, materials and protocols for synchrotron radiation-based analysis, in particular for the acquisition of combined Synchrotron Radiation X-Ray Fluorescence and X-ray Absorption Spectroscopy data.

The effects of rapid pulse electric current sintering (PECS), Ni as a Co binder substitute, Mo2C additions and laser surface modification (LSM) on the microstructure, mechanical properties and machining performance during roughing and finishing turning of Ti-6Al-4 V were investigated. Additions of Mo2C reduced the carbide grain size from 0.65 ± 0.01 μm to 0.5 ± 0.01 μm in liquid phase sintered (LPS) WC-Co/Ni cermets, with the PECS manufactured WC-0.5Cr3C2–3.5Mo2C-10Co (wt%) having the highest hardness. The LSM technique produced a ~2.5 μm self-carbide coating, increasing the surface hardness of all the samples. LSM was done to improve abrasion, attrition and thermal wear resistance. Turning was done at cuttings speeds (vc) of 45–120 m/min, depths of cut (ap) of 0.25–2.0 mm and feeds of 0.15–0.2 mm/revolution, under lubricated conditions. The developed inserts were compared to TH10 (an industrial reference), and performance was assessed by cutting forces, tool wear and tool life. The liquid phase sintered WC-0.5Cr3C2-10Co (wt%) and WC-0.5Cr3C2–3.5Mo2C-10Co (wt%) inserts had longer tool lives than TH10 during roughing at a cutting speed (vc) of 45 m/min, depth of cut (ap) of 2 mm and feed of 0.2 mm/revolution, although TH10 had the best tool life during finishing (vc = 120 m/min, ap = 0.25 mm and feed =0.15 mm/revolution). Generally, LSM had a negligible effect on tool life, WC-Ni based inserts had the shortest tool lives and LPS inserts performed better than PECS inserts.

The effects of rapid pulse electric current sintering (PECS), substitution of WC by NbC and Co by Ni, and carbide additives (TiC and Mo2C) on the microstructure, elastic modulus, B3B transverse rupture strength (TRS) and high temperature sliding wear on WC-Co, WC-Ni, NbC-Co and NbC-Ni cermets were studied. Additions of x% Mo2C and y% TiC (where x and y were 14 GPa hardness and ~10 MPa.m1/2 fracture toughness (KIC) and ball-on-three-balls (B3B) TRS > 1600 MPa. The sintering techniques had negligible effect on the samples' elastic and shear modulus, and all WC-based samples had higher elastic modulus than all NbC-based samples (by ~120 GPa). High temperature sliding wear tests were carried out using a ball-on-disk tribometer, with a 10 N force, at a sliding speed of 1.34 m/s for 0.8 km (10 min) and 2.4 km (30 min), using 100Cr6 (AISI 52100) steel balls at 400 °C and 0% humidity. For the 2.4 km sliding distance, all the WC cermets had lower wear volumes than NbC cermets, with LPS WC-0.5Cr3C2-10Co having the lowest wear volume. Additions of TiC and Mo2C to NbC-12Ni improved the sliding wear resistance, with TiC having the greater effect, reducing the sample wear rate by over 30% from 15.1 × 10−6 mm3/N·m to 9.4 × 10−6 mm3/N·m after sliding distance of 2.4 km. Generally, the LPS samples had lower wear volumes than the corresponding SPS samples, due to higher K1c and TRS.

X-ray fluorescence analysis is a widely used technique in many applications. Recent advances in X-ray optics, in particular, in polycapillary manufacturing, have allowed achieving microscale spatial resolution, even with conventional sources. Nowadays, many apparatus for X-ray microfluorescence are available. But the majority of them are equipped with experimental chambers, which limit their applicability only to small-sized samples. To overcome this limitation, a new instrument named Rainbow X-Ray (RXR), optimized for large and heavy objects, has been developed at XLab Frascati. Here, we present this unit dedicated to 2D and 3D X-ray microspectroscopy (both mapping and ‘colour‘ tomography), with a resolution between 25 and 75 μm, depending from the incident energy in the range 800eV–25keV. Copyright © 2015 John Wiley & Sons, Ltd.

The effects of rapid sintering by pulse electric current sintering (PECS), variation in starting WC size (0.1–0.8 μm), Ni as a Co binder substitute and TiC, NbC and Mo 2 C additions on the microstructure, abrasion wear, thermal shock and impact resistance of WC–Co and WC–Ni alloys were studied. Abrasion wear tests were done using a ball-on-disk tribometer, with 100Cr6 steel and silicon nitride balls. Use of PECS gave finer microstructures with poorly distributed binder pools than similar liquid phase sintered (LPS) samples, although large angular WC grains of up to 1 μm occurred in the nano (0.1 μm) and ultrafine (0.4 μm) grades. Addition of 5 wt.% NbC to WC–10Co (wt.%) had negligible effect on the WC grain size, while 5 wt.% Mo 2 C to WC–6.25TiC–9.3Ni significantly improved WC grain growth inhibition, leading to increased hardness (from ~ 13 to > 21 GPa) and reduced wear rate (from 2.73 × 10 − 4 to − 5 mm 3 ·N − 1 ·m − 1 ), compared to the LPS WC–9.3Ni. Thermal shock and impact resistance were measured using a thermal imaging camera and force gauges while testing the samples as cutting tools on Ti–6Al–4V under aggressive interrupted milling conditions. The LPS samples had better thermal shock and impact resistance, due to their higher fracture toughness (> 12.5 MPa·m 0.5 ) and B3B transverse rupture strength (> 2100 MPa), as a result of the larger and better binder pool distribution.

structural applications in the petrochemical, telecommunication, aerospace, and foodprocessing industries. This is due to their excellent corrosion resistance and good mechanical properties, such as toughness, ductility, and formability (Bain and Griffiths, 1927; Jenkins et al. 1937; Zapffe, 1949). However, due to the austenitic structure, these steels have quite low surface hardness and poor wear resistance (Bell, 2002; Fewell et al., 2000). To improve the surface properties, diffusion and thermochemical surface treatment techniques such as carburizing (Agarwal et al., 2007; Fewell et al., 2000), nitriding (Bell, 2002), nitro-carburizing (Renevier et al., 1999) and ion implantation (Liang et al., 2007) have been used, without impairing the corrosion resistance of the steel (Bell, 2002; Renevier et al., 1999). The treatment temperatures were kept below 500°C to prevent the formation of chromium carbides and nitrides, which deplete chromium from the matrix and reduce corrosion resistance (Matula et al., 2001). Little has been reported on the pack carburizing of austenitic stainless steels and its effects on the mechanical properties. This is probably because pack carburizing of these stainless steels is considered a difficult process, due to the presence of the Cr2O3 oxide surface layer (Davis, 1994; Mingolo et al., 2006). The tenacious Cr2O3 surface layer serves as an inhibiting barrier and is also selfhealing, which contributes to the ‘stainless’ characteristic of stainless steels. However, it was felt a worthwhile endeavour to ascertain whether this cheaper method could be used. Other forms of carburizing, such as gas and plasma, are normally used for stainless steel rather than pack carburizing, which is more commonly used for mediumand low-carbon steels (Agarwal et al., 2007; Fewell et al., 2000; Renevier et al., 1999). The major parameters that influence carburizing are soaking time, carburizing temperature, and carbon potential (Shewmon, 1963). As a high proportion of mechanical failures are due to fatigue, extensive research is being done in this area (Akita and Tokaji, 2006). Nucleated fatigue cracks grow into macrocracks, resulting in catastrophic failures. Initiation of fatigue is a surface phenomenon, and approximately 80% of all engineering Mechanical behaviour of pack carburized AISI 316L austenitic stainless steel

Laser shock peening (LSP) technology is a laser-induced shock process implemented as a surface enhancement technique to introduce beneficial compressive residual stresses into metallic components. The process employs water to confine and enhance the pressure pulse delivered to the target. For thick water layers, or fully water immersed LSP, a cavitation bubble is generated by the surface vaporization of the LSP laser pulse. This research shows that the first bubble oscillation period of the cavitation bubble can be used to characterize effective and repeatable energy delivery to the target. High-speed shadowgraphy is implemented to show that variations in the bubble period occur before visual observations of dielectric breakdown in water. The diagnostic potential of the first bubble oscillation period is used to identify the dielectric breakdown threshold of water, which shows an increase with increasing water quality measured by water conductivity.

An attempt to improve the machining performance of NbC-Ni cutting inserts by rapid pulse electric current sintering (PECS), TiC and Mo2C additions and laser surface modification (LSM) was done. Use of a nickel binder and additions TiC and Mo2C to liquid phase sintered (LPS) NbC based samples led to comparable hardness (>13 GPa) and KIC (~10 MPa.m1/2) to LPS WC-Co/Ni samples. The laser surface modification (LSM) technique produced a ~2.5 μm thick self-carbide coating, increasing the surface hardness of all the samples. Laser surface modification was done to improve abrasion and attrition wear resistance. Face-milling of grade 17 grey cast iron (BS 1452/GG35) was conducted at 100–500 m/min cutting speeds (vc) and 0.25–1.5 mm depths of cut (ap). The insert wear was measured after every pass, and analyzed by annular dark field scanning transmission electron microscopy (ADF-STEM). During roughing, WC-Co based inserts had the lowest flank wear rate (FWR) values, with the WC-10Co (LPS) insert having a FWR of 10.15 μm/min after 20 min cutting time. However, during semi-finishing and finishing, NbC-4TiC-12Ni (PECS) and NbC-4Mo2C-4TiC-12Ni (PECS) inserts had the lowest FWR values, showing up to six times longer tool life than the WC-Co (LPS) inserts based inserts and 12 times longer life than the WC-Ni based inserts. Generally, LSM improved the NbC inserts' tool life, reducing the FWR values in all NbC based inserts in all cutting tests.

Quantitative elemental determination for concentrations in the ppb range requires a careful preparation of the sample. In particular, for elemental analysis of very low concentration samples, less than 1 ng/mm 2 , a very bright X-ray source, typically synchrotron radiation (SR) in total external reflection fluorescence regime (SR-TXRF), is required. Here, we wish to demonstrate that a conventional source combined with a polycapillary semi-lens can provide a quasi-parallel beam intense enough for desktop TXRF analysis of low concentration samples.

The presence of multilayered structures is common in such cultural artefacts as paintings, corroded metals, objects that underwent a whatever form of surface qualification. One of the most usual and complete ways to investigate such structures is observing a cross section, which requires sampling. There are however situations where at least part of the stratigraphic information can be derived non-destructively: the literature shows that X-ray fluorescence (XRF) has frequently been used, in recent years, for this purpose, with special regard to paintings and gilded metals. Aim of this paper is to further explore the suitability of XRF-based techniques to characterise multilayered structures. This is achieved by introducing improvements, with respect to previous works, in both equipment and data processing. The method, that has been developed for gilded and enamelled silver artefacts, relies on optimum excitation conditions provided for silver and on the relationship existing between the ratio AgKα/AgKβ of its fluorescence lines and the gilding thickness itself. The coating (gilding or enamel) thickness is derived by verifying the condition C Kα,Ag = C Kβ,Ag , where C Kα,Ag and C Kβ,Ag are the mass fractions of silver calculated on the lines AgKα and AgKβ, respectively. The calculations are carried out by PyMCA, a Fundamental Parameters code that implements the analysis of multilayered samples. As a case study we investigated in situ the four processional crosses of Borbona, Sant'Elpidio, Rosciolo and Forcella, made of a wood core with attached gilt and embossed silver sheets and enamelled silver plates. The analyses allowed to distinguish ancient restorations from original parts, to characterise the enamels and find their composition consistent with the dates of manufacturing and, as regards the cross of Rosciolo, to hypothesize the contribution of different “hands” in its manufacturing.

Fatigue and crack propagation tests are carried out on 7075-T73 open hole aluminium alloy specimens. A remarkable increment of fatigue life due to the Split Sleeve Cold ExpansionTM process is observed, further improved by applying the process twice on the same hole. Comparable increments are obtained by using the StressWaveTM method. Specific tests are performed in order to point out a possible relaxation of the residual stresses due to fatigue loading. The results obtained reveal no relaxation phenomena in the tested specimens. The compressive residual stress around cold expanded holes is numerically evaluated. Dedicated experiments based on the Sachs method are conducted to confirm the residual stress prediction.

An experimental investigation of a fluid to reconstruct the internal structure was carried out by an X-ray ?-tomography technique using a Cu K? source coupled with polycapillary optics and a CCD detector. The fluid was a transient gasoline spray generated by a multi-hole GDI injector for automotive applications at 40 MPa injection pressure and 4.0 ms duration. Measurements of mass density and droplet fragmentation in a region of few cubic millimeters downstream the injector nose are of huge importance to define the atomization process and the air/fuel mixture formation going on for the combustion. The coupling of a conventional X-ray source with polycapillary optics increased greatly the radiation flux, shaping a low-divergent beam and overcoming the relative low absorption of the hydrocarbon chain. The experimental setup is restrained in a table-top configuration contrary to the synchrotron sources generally used for these samples. Extinction images acquired along the line-of-sight source-spray-detector permitted the reconstruction of a 3D structure of the spray and its morphology. Gaussian-type distribution of the fuel densities results for the cross sections of the jets with peaks along its axis and a decreasing behavior toward the periphery.

OBJECTIVE: To evaluate the effects of different instructions for the assessment of maximum walking speed during the ten-meter walking test with chronic stroke subjects. METHODS: Participants were instructed to walk under four experimental conditions: (1) comfortable speed, (2) maximum speed (simple verbal command), (3) maximum speed (modified verbal command-"catch a bus") and (4) maximum speed (verbal command + demonstration). Participants walked three times in each condition and the mean time to cover the intermediate 10 meters of a 14-meter corridor was registered to calculate the gait speed (m/s). Repeated-measures ANOVAs, followed by planned contrasts, were employed to investigate differences between the conditions (α=5%). Means, standard deviations and 95% confidence intervals (CI) were calculated. RESULTS: The mean values for the four conditions were: (1) 0.74m/s; (2) 0.85 m/s; (3) 0.93 m/s; (4) 0.92 m/s, respectively, with significant differences between the conditions (F=40.9; pOBJETIVO: Avaliar os efeitos de diferentes instruções para avaliação da velocidade de marcha máxima de indivíduos hemiparéticos durante o teste de caminhada de 10 metros. MÉTODOS: Os indivíduos deambularam em quatro condições experimentais: (1) velocidade habitual, (2) velocidade máxima (comando verbal simples), (3) velocidade máxima (comando verbal modificado: pegar ônibus), (4) velocidade máxima (comando verbal + demonstração). Solicitou-se a cada participante que deambulasse três vezes em cada condição, e a média do tempo necessário para percorrer os 10 metros intermediários de um corredor de 14 metros foi utilizada para cálculo da velocidade (m/s). A ANOVA de medidas repetidas, com contrastes pré-planejados, foi utilizada para comparação dos dados (α=5%), sendo apresentados valores de média, desvio-padrão e intervalos de confiança (IC) de 95%. RESULTADOS: As médias de velocidade para as quatro condições foram: (1) 0,74m/s; (2) 0,85m/s; (3) 0,93m/s; (4) 0,92m/s, respectivamente, apresentando diferenças significativas entre as condições (F=40,9; p

The current paper describes a destructive, sectioning method for measuring residual stress in welded panels, using electric strain gauges. Since this method is carried out rather simply, it has a wide range of possible applications. For this reason, a more thorough analysis of the method is performed. The potential limits of its application are investigated, together with the parameters that can influence the obtained results. The sectioning method is verified by determining residual stress in welded panels numerically. The results show it is possible to estimate the residual stress field in a welded structure rapidly and accurately, by using reasonably priced equipment.

Fatigue tests were carried out on 4 mm thick spot welded joints; the material was stainless steel AISI 301, quarter hard. Some specimens were instrumented with a strain gauge bonded in correspondence with one of the edges of the spot weld. Strain gauge output was demonstrated to be a reliable instrument to monitor the nucleation and propagation of fatigue cracks. A good correlation was found between strain gauge output and spent fatigue life. Some fatigue tests were suspended when the strain gauge output was equal to pre-fixed values, corresponding to fatigue life in the range from 15 to 85%. Subsequently, the specimens were dissected to observe fatigue cracks. The same correlation existed between crack depth and fatigue life. Small cracks were observed in specimens fatigue tested up to 15% of the mean fatigue life; fatigue cracks in the joints under examination would be nucleated between 5 and 10% of fatigue life. Finite Element calculations were carried out, introducing in the models cracks similar to those observed in the fatigue tests. Calculated strain at the external surface compared well with the measured strain as a function of crack depth. Calculations demonstrated that small errors in strain gauge position can be tolerated without appreciable deterioration in crack dimension prediction.

Polycapillary lenses are well known optical devices for radiation and charged particles. These lenses consist of thousands channels through which the signal is transmitted by total external reflection phenomenon. Their application have made possible technical improvements in different fields such as imaging, fluorescence analysis, channeling studies etc. In particular, the application of this optics coupled with conventional sources such as X-ray tubes has opened a new season for potential applications of desktop instrumentations. For instance, the usage of such lenses has enhanced the spatial coherence and the brilliance over the sample allowing better resolution and contrast for imaging purposes. In addiction, improved focusing power and confocal configuration of other lenses has improved the resolution, from both the energy and the spatial points of view, in fluorescence mapping. A recent work has addressed the behavior of the transmitted radiation through a single capillary in vibrating regime. In this work a test of using a vibrating capillary for stroboscopic imaging is presented. A sample characterized by a known periodic event is studied with a synchronized vibrating capillary.

XRF imaging spectrometry is a powerful tool for materials characterization. A high spatial resolution is often required, in order to appreciate very tiny details of the studied object. With respect to simple pinholes, polycapillary optics allows much more intense fluxes to be achieved. This is fundamental to detect elements in trace and to strongly reduce the global acquisition time that is actually among the main reasons, in addition to radioprotection issues, affecting the competitiveness of XRF imaging with respect to other faster imaging techniques such as multispectral imaging. Unlike other well-known X-ray optics, principally employed for high brilliant radiation source such as synchrotron facilities, polyCO can be efficiently coupled also with conventional X-ray tubes. All these aspects make them the most suitable choice to realize portable, safe and high performing μXRF spectrometers. In this work preliminary results achieved with a novel 2D and 3D XRF facility, called Rainbow X-Ray (RXR), are reported, with particular attention to the spatial resolution achieved. RXR is based on the confocal arrangement of three polycapillary lenses, one focusing the primary beam and the other two capturing the fluorescence signal. The detection system is split in two couples of lens-detector in order to cover a wider energy range. The entire device is a laboratory user-friendly facility and, though it allows measurements on medium-size objects, its dimensions do not preclude it to be transported for in situ analysis on request, thanks also to a properly shielded cabinet.

The Frascati National Laboratories (LNF) are the oldest and largest research infrastructure of INFN, mainly devoted to the research in nuclear and particle physics, to the development of particle accelerators and frontier studies on new acceleration techniques. LNF is the place where the first electron-positron collisions were obtained in the early 60s. Presently LNF operates two accelerator complexes: DAFNE, an e+e- collider with center of mass energy set to the mass of the Φ meson, 1020 MeV. SPARC, a high intensity photoinjector capable of delivering electron beams up to 200 MeV, combined with a high power laser (FLAME), able to produce ultra short pulses, in the so called SPARC_LAB facility. The laboratory hosts also the NAUTILUS gravitational waves resonant bar detector, and thanks to the availability of several infrastructures, workshops, clean rooms etc.., it is also widely used as a facility for constructing large particle detectors used in other laboratories. The purpose of the present document is to address the question: is there a viable program on the development of internal activities which can allow the Laboratory to maximally exploit its capabilities and to maintain its role at the forefront of scientific research in the next decade? In particular, given the present Italian financial situation, is this possible by wisely upgrading the presently running infrastructures at moderate costs? On November 10-11, 2014 a workshop was held at LNF with the aim to discuss the above issues, with a broad participation of researchers from Italian and foreign institutions. A second workshop dedicated to the applications of the existing facilities to Materials Science was held on February 26-27, 2015. This document tries to summarize the main conclusions of these discussions.

The series version of the M346 military trainer aircraft is currently under construction at Aermacchi (Venegono Superiore, Italy). The design target life of the aircraft, which will be certified for Damage Tolerance, is 12 000 flight hours (FH), with the possible extension to 16 000 FH after specific inspections. Fatigue tests were performed on critical elements at the Department of Aerospace Engineering at University of Pisa in order to verify crack propagation calculations. The wing to fuselage connection is one of the most interesting elements from the fatigue point of view. Spars and frames, both integrally machined, are connected by two lug-fork joints; the base material is aluminium alloy 7050-T7451 for both the elements. High interference bushings, ForceMate®, produced by FTI (Fatigue Technology Inc., Seattle, WA) were used in the lug/fork connections. Experimental activity was carried out on two different specimens. The first, a Compact Tension specimen, was tested under constant amplitude loading to verify the fatigue crack growth rate data contained in NASGRO 4, the software used for Damage Tolerance evaluations. Experimental results were fully comparable with the NASGRO 4 material database. Additional variable amplitude loading tests were carried out in order to calibrate crack growth prediction models used in the analyses. The second specimen was a lug-fork joint designed as the actual joints present on the aircraft. Both constant and variable amplitude loading fatigue tests were carried out in this case too. Results obtained clearly indicated the beneficial effect of ForceMate bushings, compared to shrink fit bushings.

Since Friction Stir Welding has been identified as a key technology for primary aerospace structures, fatigue crack growth testing and modelling is required. However, there is still a complete lack of information regarding the fatigue crack propagation in friction stir welds under variable amplitude loading and flight loading conditions. Experimental investigations have been performed on centre cracked 4 mm thick AA2024-T3 base metal and FSW specimens: regarding the FSW samples, the crack was placed 5 mm out of the weld centre, in the most critical part of the joint: the coupons have been tested under simple variable amplitude load sequences, and under a standardized flight-simulation load history, Falstaff. The fatigue crack propagation was then predicted using widespread aerospace fracture mechanics software packages. Interaction effects and internal residual stresses were firstly separately simulated and than combined in order to evaluate the ability to predict the fatigue crack propagation on FSW welded structures under service loading conditions.

Fatigue tests were carried out on 2024-T351, thickness 1.6 mm, central hole specimens containing pins installed with five different interference-fit levels. Tests clearly demonstrated the beneficial effect of interference fit on fatigue resistance, up to the maximum value examined, 2.5%. A three-dimensional (3D) finite-element model was used in order to characterize the stress field around the hole. A large specimen, with a 40-mm-diameter hole filled with interference-fit pin, was instrumented by strain gauges and statically tested in order to check FEM results. A very good correlation existed between measured and numerically evaluated strains. FEM results demonstrated the well-known effect of interference-fit fasteners on reducing stress ranges. By increasing the interference level, the stress range was practically unchanged, while the mean stress decreased. Interference-fit produces a biaxial stress state, which must be taken into account for fatigue evaluation. In the present case, a simple criterion, based on hoop strain, predicted the fatigue results quite well with the exception of open hole fatigue test results, which were overestimated.

An experimental study was performed in order to determine the influence of the sequence of operations on the effectiveness of Laser Shock Peening (LSP) treatment in increasing the fatigue performances of open-hole aluminium specimens. Residual stress measurements, fractographic analysis and FEM analysis were performed, indicating the presence of compressive residual stresses on the surface of the treated specimens and tensile residual stresses in the mid-section along the thickness of the specimens. Negative effects on fatigue lives were encountered on the specimens with the hole already present, while positive effect were observed in specimens in which the hole was drilled after LSP treatment. These results indicate that LSP can be a good solution for “in production” application, in which open holes are to be drilled after the LSP treatment. The application in which LSP is used “in service” on structures with pre-existing cut-outs, has proven to be impracticable in the investigated configuration.

Fatigue crack propagation tests of through cracks in 3 mm thick aluminium alloy 6013-T6 plates, under combined membrane and bending stresses were carried out. Five different values for the ratio of bending to membrane stresses, SB, were examined: 0, 0.55, 1.25, 1.8 and 2.23. Firstly, the results were elaborated by taking into account only the membrane stress and the front dimension of the crack for the evaluation of the stress intensity factor range. The results relevant to the lower SB values, evaluated in this mode, show good agreement with the results obtained when only the membrane stress was applied, while the results obtained at the higher SB values exhibit a remarkable increase in the crack propagation rate. The results were successively evaluated on the basis of tabular stress intensity factor solutions available in the literature; the agreement between the predicted and the experimental data occurs when mean values of stress intensity factor, rather than local values, were used at the back face of the plate, i.e., the face where the bending produces a compressive stress, to counteract the high gradient of stress intensity factor present in this area.

This work reports the results of X-ray μ -tomographic investigation on the inner structure of high pressure fuel sprays. X-ray imaging is widely used in industry where non-destructive and high accuracy measurements of the samples morphology are required. A high flux beam can overcome the problems related to the low absorption of hydrocarbon chains as fossil fuels, therefore synchrotron X-ray sources are generally used for fuel sprays investigation. A desktop facility has successfully been used to characterize high pressure gasoline sprays for automotive applications. A X-ray tube coupled with polycapillary optics has been used providing a high flux beam with low divergence. In this paper the last improvements concerning quantitative measurements carried out on fuel sprays are reported.

This paper relates the X-ray micro-Computed Tomography and micro X-ray Fluorescence 2D mapping of a synthetic emerald performed by a conventional X-ray source matched with polycapillary optics. The investigated crystals were synthesized in 1888 by Hautefeuille and Perrey starting from a stochiometric oxide mixture and using LiMoO4 as a flux; Cr was added to the system to give the green-color to the resulting crystals. Preliminary scanning electron microscope-backscattered electron images, coupled with wavelength-dispersive spectrometry microanalyses, showed a peculiar ‘hourglass’ distribution of Cr across the beryl crystals. In this contribution, we show the capability of a laboratory polycapillary lenses/X-ray tubes layout to characterize at the micrometric scale; the 3D spatial distribution of Cr in these emerald crystals. Actually, this technique offers many opportunities to characterize natural and technological materials where zoning of particular chemical elements occur at the micron or sub-micron scale. Copyright © 2015 John Wiley & Sons, Ltd.

A novel study on a different use of polycapillary optics is presented. The scope of this study is to achieve an efficient radiation collimation due to handled beam profiling that avoids the typical one based on total external reflection into the capillary channel. For this purpose a vibration is applied to a monocapillary in order to emulate a “virtual roughness” on the channel internal wall surface. The transmission properties of such a system for different vibrational states are discussed.

Comparative fatigue tests were carried out on Friction Stir Welded specimens of a 2195-T8 aluminum–lithium alloy that differed significantly in width. The width of the larger specimens was over thirteen times greater than that of the small specimens. Fatigue results showed a clear “size effect”, i.e. fatigue life of large specimens was about 40% of the corresponding value of small specimens. The Equivalent Initial Flaw Size methodology was adopted to correlate the two sets of results. Fatigue crack initiation life was disregarded with respect to crack propagation life, and fatigue life was evaluated only as propagation of a small pre-existing defect. Following this methodology, test results of small specimens were used to evaluate the initial equivalent flaw contained in each specimen. It was assumed that this data followed a normal distribution. The equivalent initial flaw in larger specimens was evaluated by simple geometrical considerations. A very good assessment of mean fatigue life and scatter in the fatigue results of large specimens was obtained by simulating the propagation of these defects. Calculations were carried out by taking also welding residual stresses into account, but the results demonstrated that this effect was not significant.

In this work the testing results for the spectrometer with a large sensitive area developed for the crystal monitoring station of modern hadron accelerator control systems used for the beam collimation are presented. The investigations were carried out at the XLab Frascati LNF laboratory aiming mostly in studying the detector sensitivity uniformity throughout the sensor area.

A X-ray μ -tomography technique, using a Cu K α source at 8.048 keV coupled with both polycapillary optics and CCD detector, has been developed to reconstruct the composition of a transient gasoline spray generated by a high-pressure GDI injector for automotive applications. The polycapillary elements enable shaping the divergent beams and getting high-contrast images due to the suppression of radiation multiple scattering. A pressure-tight device permits the 360 ° rotation of a six-hole nozzle, with a step of 0.1 ° , at injection pressures up to 20 MPa, while the spray plume develops in a vented Plexiglas chamber at the atmospheric backpressure. The entire system is configured as a table-top experiment. The extinction images acquired along the X-ray source-spray-detector line-of-sight have permitted the reconstruction of a 3D structure together with a morphology of the jets within a 3 mm region downstream the nozzle. The spray shape as well as the propagation direction can be clearly identified in the tomographic reconstruction for all the six jets. Quantitative measurements of the fuel mass density in the near nozzle region have been performed. Typical Gaussian-shape distribution of the intensities appears for the cross sections revealing the more dense jet regions in the core, while slight longitudinal asymmetries indicate an interaction between the jet plumes.

Comparable fatigue tests were carried out on aluminium alloy 7475-T7351 double butt joints with untreated and with cold expanded holes. Surprisingly, the behaviour of the specimens having cold expanded holes was worse than that of specimens with untreated holes. This result was attributed to the surface upset which was present in cold expanded holes. Several hypotheses were formulated and experimentally verified to overcome this problem, such as deeper hole deburring, rivet diameter, joint design and grip material, steel instead of aluminium alloy. Additional tests demonstrated that the problem was not present in sealed joint as the surface upset was hidden in the sealant thickness. Sealants have detrimental effects in the fatigue resistance of riveted joints, as they increase the load transferred by rivet bearing. The hole expansion is beneficial in this condition, while in un-sealed joints its effect must be accurately evaluated. Other authors too highlighted possible problems due to surface upset, up to suggest to eliminate it. Only in a very few cases, a reduction of fatigue life as a consequence of hole expansion was observed.

Laser Shock Peening (LSP) is a material enhancement process used to introduce compressive residual stresses in metallic components. This investigation explored the effects of different combinations of LSP parameters, such as irradiance (GW/cm2) and laser pulse density (spots/mm2), on 3.2 mm thick AA6056-T4 samples, for integral airframe applications. The most significant effects that are introduced by LSP without a protective coating include residual stress and surface roughness, since each laser pulse vaporizes the surface layer of the target. Each of these effects was quantified, whereby residual stress analysis was performed using X-ray diffraction with synchrotron radiation. A series of fully reversed bending fatigue tests was conducted, in order to evaluate fatigue performance enhancements with the aim of identifying LSP parameter influence. Improvement in fatigue life was demonstrated, and failure of samples at the boundary of the LSP treatment was attributed to a balancing tensile residual stress.

Application of polycapillary optical systems to improve a spatial resolution for the ?-XRF analysis by focusing a primary x-ray beam and/or by collecting fluorescence emission is well known. The challenge is to optimize them in combination with x-ray source for exciting K-lines above 20 keV that could allow characterization of many materials composed by heavy elements. To pursue this goal, preliminary studies on possible polycapillary lens employment in thickness determination for multilayer metal materials will be presented in this work. In this paper, the results of first attempts of integrating PyMCA with Monte Carlo simulation code (XMI-MSIM) that takes into account the secondary fluorescence effects on quantitative analysis of homogeneous matrices, in particular, metal alloys, are presented. © 2014 Author(s).

In this paper all the research activities carried out till now for the project of the PhD Course in 'Materials, Technologies and Complex Industrial Systems Engineering MATISE' (XXVIII cycle) on the development of XRF analysis for the characterization of multilayer objects of cultural interest are illustrated. This project is carried out within the frame of the collaboration between the laboratory XLab Frascati of Laboratori Nazionali di Frascati (INFN) and the Istituto Tecnologie Applicate ai Beni Culturali di Roma (CNR).

The results of fatigue and crack propagation tests carried out on dog-bone specimens made of 2024-T3 are described. Two types of specimens were investigated: the first was machined from a 1.27-mm-thick sheet, while the second was machined from a bonded metal-laminated sheet, made of four 0.3-mm-thick layers. Crack propagation tests confirmed the high resistance of metal-laminated sheets to the propagation of fatigue cracks, compared to monolithic sheets, once again. At the same time, standard fatigue tests, carried out up to the final failure of the specimens, demonstrated a comparable fatigue resistance of monolithic and laminated specimens. As a consequence, it can be concluded that fatigue cracks nucleated earlier in the metal-laminated specimens, compared to the monolithic ones, but propagated more slowly. This behaviour was attributed to the presence of sharp edges in the inner laminas of metal-laminated materials which cannot be eliminated by deburring. Additional tests were carried out on monolithic specimens containing burrs and sharp edges at the holes. These specimens were drilled and reamed after stacking and pressing them to form a package. The specimens were fatigue tested without deburring the holes. A decrease in the fatigue resistance was observed. The formation of burrs and sharp edges was additionally promoted by inserting plastic foils between the specimens during the machining operations. Fatigue resistance of these specimens is progressively lower.