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The forthcoming introduction of the EURO VII regulation requires urgent strategies and solutions for the reduction of sub-23 nm particle emissions. Although they have been historically considered as particulate matter-free, the high interest for Natural Gas (NG) Heavy-Duty engines in the transport sector, demands their compliance with the new proposed regulations.In order to obtain high conversion of gas pollutants and a strong abatement of the emitted particles, the use of Particle Filters in NG aftertreatment (CPF) in conjunction with the Three-Way Catalyst (TWC) may represent an attractive and feasible solution.Performances of a cordierite filter were explored through an extensive experimental campaign both in Steady-State conditions and during transient engine maneuvers that involved a whole analysis of the emitted particles in terms of number and mass.This investigation assessed different emitted particle reduction efficiency, highlighting distinct levels between no-load (low idle phases) and load operating conditions.The analysis was supported by the development of a specific 1D filtration model to evaluate the particles abatement. This model was also validated during a World Harmonized Transient Cycle (WHTC), proving to be a valuable tool for understanding filtration phenomena during critical phases of the cycle.The tested filter technology showed high filtration efficiency with global levels approaching 90% over the whole cycle, without significant increase in backpressures and fuel consumption.The performed analysis lays the foundation for the use of innovative and simplified filtration models to support the optimization process of this device in view of the next stringent regulations.

BACKGROUND The radial artery is recommended by international guidelines as the default vascular access in patients with acute coronary syndromes (ACS) managed invasively. However, crossover from radial to femoral access is required in 4-10% of cases and has been associated with worse outcomes. No standardised algorithm exists to predict the risk of radial crossover. AIMS We sought to derive and externally validate a risk score to predict radial crossover in patients with ACS managed invasively. METHODS The derivation cohort consisted of 4,197 patients with ACS undergoing invasive management via the randomly allocated radial access from the MATRIX trial. Using logistic regression, we selected predictors of radial crossover and developed a numerical risk score. External validation was accomplished among 3,451 and 491 ACS patients managed invasively and randomised to radial access from the RIVAL and RIFLE-STEACS trials, respectively. RESULTS The MATRIX score (age, height, smoking, renal failure, prior coronary artery bypass grafting, ST-segment elevation myocardial infarction, Killip class, radial expertise) showed a c-index for radial crossover of 0.71 (95% CI: 0.67-0.75) in the derivation cohort. Discrimination ability was modest in the RIVAL (c-index: 0.64; 95% CI: 0.59-0.67) and RIFLE-STEACS (c-index: 0.66; 95% CI: 0.57-0.75) cohorts. A cut-off of ≥41 points was selected to identify patients at high risk of radial crossover. CONCLUSIONS The MATRIX score is a simple eight-item risk score which provides a standardised tool for the prediction of radial crossover among patients with ACS managed invasively. This tool can assist operators in anticipating and better addressing difficulties related to transradial procedures, potentially improving outcomes.

This paper describes some strategies to deal with the arduous challenge of reducing emissions from the transport sector. Two different approaches in particle emissions reduction from natural gas (NG) heavy duty (HD) engines were evaluated. The focus was on reducing the ultra-fine sub 23 nm particles, a key aspect in the vehicles’ impact on human health and environment. To this end, an experimental research activity was carried out on a NG HD engine that was EURO VI regulation compliant. Lubricant oils characterized by different base compositions and ash contents were compared to provide a preferred path to develop formulations. The performed activity on world harmonized transient cycles (WHTCs) have demonstrated a high reduction potential (≈70%) that is reachable by acting on the lube formulation. A CNG particle filter (CPF), derived from the diesel and gasoline engines technology, was fully characterized in terms of its filtration efficiency. Three different types of tests were carried out: steady state, WHTCs, and several idle-to-load step maneuvers. The CPF was highly efficient in reducing solid particles over 10 nm diameter in all the different tests. During WHTCs, the mean abatement efficiency was about 85%. Both technologies provide interesting insights to make NG HD engines compliant with the upcoming Euro VII regulation.

In bridge structural health monitoring, typically the dynamic response of the system is used to assess the health condition of the bridge. However, the dynamic interaction between a bridge and a passing vehicle imposes non-stationarity on the system response, whereby the bridge modal parameters become time-dependent and detecting damage, for example, based on the bridge modal parameters, becomes challenging. Dynamic vehicle-bridge interaction (VBI) responses have mainly been investigated for damage detection through identifying signal singularities and abrupt changes. The singularities are usually associated with high-frequency components (relative to the bridge natural frequencies), and it is demanding to isolate the damage-induced singularities from those caused by either an operational condition, i.e., track irregularities, or noise. Unlike the high-frequency range, the influence of damage on the resonance frequency of the coupled system has not been fully explored. The present study proposes the shape of the bridge instantaneous frequency as a damage sensitive feature in which the influence of the vehicle dynamics can be excluded. This study demonstrates the feasibility of a damage detection approach based on the bridge instantaneous frequency by applying Wavelet Synchrosqueezed Transform (WSST). In this approach the bridge instantaneous frequency variation induced by damage is distinguished from the bridge instantaneous frequency variation induced by the vehicle. Several damage scenarios that are implemented numerically are analyzed to verify the method’s performance. The results demonstrate that a high resolution instantaneous frequency extracted from the VBI dynamic response outperforms the resonance frequency in determining the local disruption, leading to detecting the damage. A Damage Index (DI) is also proposed as an attempt to quantify the damage severity.

This research focuses on the verification of the viability of image compression in infrared thermography in order to address the problem of data storage. Specifically, images from vibrothermographic tests were utilized due to their special characteristics compared to the results from alternative infrared thermography techniques, which are able to introduce additional uncertainties to the compression process. In this research, an adaptive algorithm based on the lifting discrete wavelet transform and set-partitioning embedded blocks was used for image compression. Five different methods, namely the compression ratio, mean squared error, peak signal-to-noise ratio, structural similarity index and coordinate modal assurance criterion, were applied to evaluate the performance of the compression process while identifying and locating the regions affected more significantly after image compression. Feature extraction through the independent component analysis was then applied to the images to separate the features such as the hot spots so that the influence from the image compression process on each important feature could be evaluated independently. In this article, the theoretical background of the applied data processing techniques is firstly presented. Through two sets of data acquired from vibrothermographic tests on an aerospace-grade composite plate containing delamination, the effects of the image compression process on the relevant hot spots are evaluated, and the effectiveness of the compression process is verified. It is demonstrated that the compression process was able to reduce the size of the images significantly without adversely affecting the quality of the important features indicating the presence of damage. The major characteristics of the key features have been successfully preserved after effective image compression.

OBJECTIVES The aim of this study was to assess the impact of access-site crossover in patients with acute coronary syndrome undergoing invasive management via radial or femoral access. BACKGROUND There are limited data on the clinical implications of access-site crossover. METHODS In the MATRIX (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox)-Access trial, 8,404 patients with acute coronary syndrome were randomized to radial or femoral access. Patients undergoing access-site crossover or successful access site were investigated. Thirty-day coprimary outcomes were a composite of death, myocardial infarction, or stroke (major adverse cardiovascular events [MACE]) and a composite of MACE or Bleeding Academic Research Consortium type 3 or 5 bleeding (net adverse clinical events [NACE]). RESULTS Access-site crossover occurred in 183 of 4,197 patients (4.4%) in the radial group (mainly to femoral access) and 108 of 4,207 patients (2.6%) in the femoral group (mainly to radial access). In multivariate analysis, the risk for coprimary outcomes was not significantly higher with radial crossover compared with successful radial (MACE: adjusted rate ratio [adjRR]: 1.25; 95% confidence interval [CI]: 0.81 to 1.93; p = 0.32; NACE: adjRR: 1.40; 95% CI: 0.94 to 2.06; p = 0.094) or successful femoral access (MACE: adjRR: 1.17; 95% CI: 0.76 to 1.81; p = 0.47; NACE: adjRR: 1.26; 95% CI: 0.86 to 1.86; p = 0.24). Access site-related Bleeding Academic Research Consortium type 3 or 5 bleeding was higher with radial crossover than successful radial access. Femoral crossover remained associated with higher risks for MACE (adjRR: 1.84; 95% CI: 1.18 to 2.87; p = 0.007) and NACE (adjRR: 1.69; 95% CI: 1.09 to 2.62; p = 0.019) compared with successful femoral access. Results remained consistent after excluding patients with randomized access not attempted. CONCLUSIONS Crossover from radial to femoral access abolishes the bleeding benefit offered by the radial over femoral artery but does not appear to increase the risk for MACE or NACE compared with successful radial or femoral access. (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox [MATRIX]; NCT01433627) (C) 2021 by the American College of Cardiology Foundation. The MATRIX trial was sponsored by Societa Italiana di Cardiologia Invasiva (a nonprofit organization), which received grant support from The Medicines Company and Terumo. This substudy did not receive any direct or indirect funding. Dr. Leonardi has received grants and personal fees from AstraZeneca, Bristol Myers Squibb/ Pfizer, and Chiesi; and has received personal fees from Bayer outside the submitted work. Dr. Vranckx has received personal fees from AstraZeneca, Terumo, CSL Behring, Daiichi-Sankyo, and Bayer Health Care outside the submitted work. Dr. Frigoli is affiliated with CTU Bern, University of Bern, which has a staff policy of not accepting honoraria or consultancy fees. However, CTU Bern is involved in the design, conduct, or analysis of clinical studies funded by not-forprofit and for- profit organizations. In particular, pharmaceutical and medical device companies provide direct funding to some of these studies. For an up- to-date list of CTU Bern's conflicts of interest, see http://www.ctu.unibe.ch/research/declaration_of_interest/index_eng. html. Dr. Windecker has received research and educational grants to the institution from Abbott, Amgen, Bristol Myers Squibb, Bayer, Boston Scientific, Biotronik, Cardinal Health, CardioValve, CSL Behring, Daiichi- Sankyo, Edwards Lifesciences, Johnson & Johnson, Medtronic, Querbet, Polares, Sanofi, Terumo, and Sinomed; serves as an unpaid member of the steering and/or executive groups of trials funded by Abbott, Abiomed, Amgen, Bristol Myers Squibb, Boston Scientific, Biotronik, Cardiovalve, Edwards Lifesciences, MedAlliance, Medtronic, Polares, Sinomed, V-Wave, and Xeltis (but has not received personal payments from any pharmaceutical company or device manufacturer); and is a member of the steering and/or executive committee groups of several investigator- initiated trials that receive funding from industry without impact on his personal remuneration. Dr. Valgimigli has received grants and personal fees from Abbott, Terumo, and AstraZeneca; has received personal fees from Chiesi, Bayer, Daiichi-Sankyo, Amgen, Alvimedica, Biosensors, and Idorsia; and has received grants from Medicure outside the submitted work. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Valgimigli, M (corresponding author), Ente Osped Cantonale, Cardioctr Ticino Inst, Via Tesserete 48, CH-6900 Lugano, Switzerland. marco.valgimigli@cardiocentro.org

This study describes a physics-based and data-driven nonlinear system identification (NSI) approach for detecting early fatigue damage due to vibratory loads. The approach also allows for tracking the evolution of damage in real-time. Nonlinear parameters such as geometric stiffness, cubic damping, and phase angle shift can be estimated as a function of fatigue cycles, which are demonstrated experimentally using flexible aluminum 7075-T6 structures exposed to vibration. NSI is utilized to create and update nonlinear frequency response functions, backbone curves and phase traces to visualize and estimate the structural health. Findings show that the dynamic phase is more sensitive to the evolution of early fatigue damage than nonlinear parameters such as the geometric stiffness and cubic damping parameters. A modified Carrella–Ewins method is introduced to calculate the backbone from nonlinear signal response, which is in good agreement with the numerical and harmonic balance results. The phase tracing method is presented, which appears to detect damage after approximately 40% of fatigue life, while the geometric stiffness and cubic damping parameters are capable of detecting fatigue damage after approximately 50% of the life-cycle.

This research focuses on the development of a damage detection algorithm based on modal testing, vibrothermography, and feature extraction. The theoretical development of mathematical models is presented to illustrate the principles supporting the associated algorithms, through which the importance of the three components contributing to this approach is demonstrated. Experimental tests and analytical simulations have been performed in laboratory conditions to show that the proposed damage detection algorithm is able to detect, locate, and extract the features generated due to the presence of sub-surface damage in aerospace grade composite materials captured by an infrared camera. Through tests and analyses, the reliability and repeatability of this damage detection algorithm are verified. In the concluding observations of this article, suggestions are proposed for this algorithm’s practical applications in an operational environment.

Wind turbines life time is commonly predicted based on statistical methods. However, the success of statistics-based maintenance depends on the amount of variation in the system design, usage and load. Life time prediction based on physical models seeks to overcome this drawback by considering the actual design and evaluating the specific usage, load and operating condition of the considered systems. In this paper, a load-based maintenance approach is proposed to predict wind turbines life time. Physical models are used to evaluate load profiles at wind turbine blade root, rotor hub center and tower head. The effects of surface roughness, side winds, yaw misalignment, rotor tilt and blade cone angle, individual blade pitching and wind turbulences are considered and quantified. It is shown that centrifugal, gravity, Euler and Coriolis accelerations dominate the blade root loads. Tilt and cone angle, as well as individual blade pitching, affect the rotor hub and dynamic tower head loads. Further, the actual wind speed distribution is considered which is also proven to be a critical life time prediction parameter. Finally, a set of parameters is proposed that need to be monitored in a specific wind turbine to enable the practical implementation of a predictive maintenance policy.

In view of the increasingly stringent emission regulations, the automotive sector needs considerable support from the development of robust and reliable engine and aftertreatment models. Accurate reproduction of engine-out and tailpipe pollutants plays a crucial role in complying with these legislations. Given the difficulty in characterizing some critical phenomena, frequently caused by strong dynamics and related to experimental uncertainties, communication between several calibrated and reliable models is mandatory. This is certainly valid for powertrains that will be powered with alternative gas fuels such as natural gas, bio-methane and hydrogen in the future. This paper describes a methodology to co-simulate a 1D CNG HD 6-cyl engine model and a 1D quasi-steady Three-Way Catalyst model in a global framework for high-fidelity virtual prototyping of the vehicle system. Through the implementation of a dedicated control logic in MATLAB/Simulink, the modeling architecture allows for the reproduction of the engine performance parameters together with the evaluation of the TWC pollutants’ conversion efficiency. An extensive database of experimental tests was used to assess the model response. The latter was validated in multiple steady-state operating conditions of the engine workplan. Using a semi-predictive combustion model, the validation was carried out over a wide range of different air-to-fuel ratios and during fast rich/lean transitions to evaluate the formation and conversion phenomena of the main chemical species, both engine-out and tailpipe. Subsequently, the complete model was validated in dynamic conditions throughout a WHTC, accurately reproducing the cut-off phases and their sudden accelerations. The numerical–experimental agreement on pollutant reproduction is generally good and globally below 3%. Larger deviations occur in extremely rich conditions and in CH4 emission evaluation due to the lack of information related to the combustion process and chemical mechanisms involving the Pd surface.

Engines fed by gaseous fuels, such as Natural Gas (NG), are proving to be an alternative to the traditional gasoline and Diesel engines. Considering the more and more restrictive regulations on pollutant emissions and the global direction towards decarbonization, Natural Gas could represent a midterm alternative solution. Methane is the primary component of NG and it has the highest H/C ratio among the hydrocarbons, providing lower carbon based emissions. In Heavy Duty sector, historically represented by Diesel vehicles, NG engines show comparable performance and benefits in terms of emissions [1]. The upcoming EURO VII regulation for gas engines is pointing the attention to the sub- 23 nm solid Particle Number (PN) emissions which can represent a critical aspect, even for this kind of engine [2]. The authors evaluated the potentialities offered by three different strategies in the abatement of PN emissions, mainly focusing on sub-23 nm particles control. An extensive experimental campaign has been carried out on a test bench Euro VI NG HD Spark Ignition engine. It is recognized that the main source of PN emissions from gaseous fuels engine is linked to the lube oil consumption [3] and its introduction into the combustion chamber. In this sense, the effect of improved rings pack design was studied, comparing two configurations of the same engine characterized by different oil rings pack. The upgrading of the rings pack reduces the oil deposits in the crevices and in the ring seats thus lowering the oil access to the combustion chamber. The results demonstrate a significant abatement (95%) of engine out PN emissions with the new designed rings pack. Since oil consumption is also influenced by the oil quality [4], the impact of specific lubricant properties has been studied. Typical automotive lubricants consist of base oil (roughly 75-90% by mass) and an additive package; the ash content is the incombustible component of the oil. The effects of different base oils and ash contents on PN emissions have been evaluated. The experimental tests have been performed on the engine with upgraded rings pack. The results show that the improvement of oil quality determines a further PN reduction up to 70%. Differently from the previous described approaches, the last strategy is not headed to the control of particle formation processes, but towards the abatement of PN at the exhaust through the addition of a CNG Particulate Filter (CPF) coupled with a Three Way Catalyst (TWC). Such technology is derived from the well consolidated DPF for Diesel engines. The potentiality of the filter has been studied when applied to a NG engine, characterized by different working conditions and significative low level of emitted particle. The study also provides insights future optimization of the system. The CPF has been tested on the engine with improved rings pack. The abatement efficiency has been calculated through a comparison of the PN emitted with and without the CPF. Although the CPF technology is still under development and optimization, the results are very encouraging and show its high potential to achieve an important PN decrease from a NG engine of roughly 85% A recap of the strategies tested and the achieved results is presented in Figure 1. Fig. 1. Technologies and abatement efficiencies on particle emissions The analyzed methods can lead to a proper sub-23 particles control toward the future regulation limits.

The dynamic response of a vehicle–bridge interaction (VBI) system is a noisy, nonstationary, and multicomponent response with closely spaced spectral components. Considering the ultimate goal as utilizing the VBI system instantaneous frequencies (IFs) for bridge condition monitoring, this paper carries out a systematic study to investigate the performance of four advanced time-frequency analysis techniques on a series of VBI responses: Hilbert–Huang transformation (HHT), continuous wavelet transform (CWT), robust local mean decomposition (robust-LMD), and wavelet synchrosqueezed transform (WSST). The novel contribution of this study is the application of the two latter techniques. The synthesized tests demonstrate that the WSST is the best method to precisely separate and localize in time the closely spaced resonances. Therefore, the WSST is applied to field measurements obtained from the Boyne viaduct in Ireland, as well. The results verify the capacity of this method to deal with time-varying vibrations adequately.

Continuous Scanning Laser Doppler Vibrometry (CSLDV) methods first appeared in the literature in the early 1990s and over the past three decades they have undergone an evolution in terms of procedures and applications which constitute a new state-of-the-art now described in this review paper. The advances in vibration measurement performed by Scanning Laser Doppler Vibrometers augmented the capability of measuring vibration data from a grid of a few hundred measurement points to a single scan which traverses and measures at many thousands of points on the same structure. The deflection shapes of vibration modes can be created by assembling two pieces of information from a scanning measurement - temporal and spatial - and the more measurement ‘points’, the better the spatial density and resolution of the deflection shape(s). The introduction of Continuous Scanning techniques challenged the traditional principle that the number of measurement points defines the spatial definition of the deflection shape. Thereafter, high definition deflection shapes could be achieved by measuring a single time series from a continuously sweeping trajectory covering the same surface area that would traditionally be covered by a set of fixed-point measurements, each of which spans a range of frequencies. The CSLDV approach compresses both the temporal oscillation and the spatial distribution of the deflection shape into one LDV output-modulated signal, whereby the harmonic oscillation and the spatial distribution across a swept area were now defined by a central response harmonic and its sidebands. This change of perspective in vibration measurements from the conventional stepped-scan method to the continuous-scan approach allowed several researchers to exploit and expand the potential of the scanning vibrometer further than its initial design specifications. This paper starts with the raison d’etre, with a brief historical account of how vibration measurements have developed over the past decades, and then moves to the theoretical background and applications of the CSLDV approach. Finally, the paper presents a philosophical and technical account of the research work carried out by several colleagues over the past thirty years and aims to provide a chronological order to the various advancements that CSLDV techniques offer in engineering structural dynamics.

During the last two decades, wind turbine industries have faced high failure rates, downtimes and costly repairs. Gearbox and generator have contributed to this, especially, because their high speed shaft bearings have often failed. In this article, an analytical method is proposed to calculate the reaction loads of flexible connecting couplings installed between wind turbine gearbox and generator. Raction loads are determined from joint kinematics and metal disk pack deformations as well as axial and angular shaft misalignment. The calculations are executed for both flexible connecting couplings and a universal joint shaft and applied to the gearbox high speed shaft. The performance of flexible connecting couplings and universal joint shaft is compared with respect to the bearing loads and life-time of the gearbox high speed shaft. It is shown that the early, unplanned bearing failures of gearbox and generator high speed shaft can often be attributed to the flexible connecting couplings installed between gearbox and generator.

Stroke is the leading cause of disability and mortality worldwide. After an acute cerebrovascular ischemia, recurrent vascular events, including recurrent stroke or transient ischemic accidents (TIA), occur in around 20% of cases within the first 3 months. In order to minimize this percentage, antiplatelet therapy may play a key role in the management of non-cardioembolic cerebrovascular events. This review will focus on the current evidence of antiplatelet therapies most commonly discussed in practice guidelines and used in clinical practice for the treatment of stroke/TIA complications. The antiplatelet therapies most commonly used and discussed are as follows: aspirin, clopidogrel, and ticagrelor.

Research activities in the development of reliable computational models for aftertreatment systems are constantly increasing in the automotive field. These investigations are essential in order to get a complete understanding of the main catalytic processes which clearly have a great impact on tailpipe emissions. In this work, a 1D chemical reaction model to simulate the catalytic activity of a Pd/Rh Three-Way Catalyst (TWC) for a Natural Gas heavy-duty engine is presented. An extensive database of tests carried out with the use of a Synthetic Gas Bench (SGB) has been collected to investigate the methane abatement pathways, linked to the lambda variation and oxide formation on palladium surface. Specific steady-state tests have shown a dynamics of the methane conversion even at fixed ? and temperature conditions, essentially due to the Pd/PdO ratio. Furthermore, combining the results of such test with dedicated Rich-Lean ? transitions it has been demonstrated that the presence of NO reduces the rate of the methane oxidation reaction. Given the high reliability of the experimental data and the possibility of managing the chemical composition of the gas entering the catalyst, important aspects related to the NH3 formation were analyzed. In the proposed kinetic scheme, NH3 decomposition phenomena are also present at high temperature due to the presence of Rh in the catalyst. Reactions involving Cerium for oxygen storage and release characterization are included in the proposed model in addition to the surface reaction mechanism, reasonably determining the TWC conversion efficiency of the main species

BACKGROUND Contemporary definitions of bleeding endpoints are restricted mostly to clinically overt events. Whether hemoglobin drop per se, with or without overt bleeding, adversely affects the prognosis of patients with acute coronary syndrome (ACS) remains unclear. OBJECTIVES The aim of this study was to examine in the MATRIX (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox) trial the incidence, predictors, and prognostic implications of in-hospital hemoglobin drop in patients with ACS managed invasively stratified by the presence of in-hospital bleeding. METHODS Patients were categorized by the presence and amount of in-hospital hemoglobin drop on the basis of baseline and nadir hemoglobin values and further stratified by the occurrence of adjudicated in-hospital bleeding. Hemoglobin drop was defined as minimal (

The growing diffusion of Heavy-Duty engines powered by Natural Gas (NG) has made it necessary to investigate specific Three-Way Catalysts (TWC), with the consequent development of reliable numerical models. This reactor allows a high conversion efficiency exclusively in a limited range of Air-to-Fuel Ratio (AFR) around the stoichiometric. In highly dynamic conditions, its behavior can differ from Steady-State ones due to numerous phenomena of Oxygen Storage and oxide formation on palladium surface, not fully detected from Engine Test Bench (ETB) data. Goal of the present research activity was to develop a 1D chemical reaction model of a Pd/Rh TWC for NG application with the use of a Synthetic Gas Bench (SGB) through an extensive and innovative experimental characterization. Specific Steady-State experiments have shown a dynamics in the methane conversion, not only to ? variation but also at fixed ? and temperature conditions, linked to the reversible Pd ? PdO transformation. Through dedicated temperature-programmed oxidation and reduction (TPO / TPR) tests, hysteresis phenomena in the methane oxidation rate were highlighted. Furthermore, with fast Rich-Lean ? transitions tests, it has been also demonstrated that the presence of NO reduces the methane oxidation reaction rate. A dedicated experimental protocol has shown the high impact of Steam Reforming reaction on methane conversion, partly responsible of a particular decrease in CO conversion efficiency at high temperatures in rich and stoichiometric conditions. In addition, given the high reliability of the experimental data and the possibility of managing the chemical composition of the gas entering the catalyst, important aspects related to the NH3 formation and decomposition were analyzed. The proposed reactions kinetic scheme describes in an acceptable way the behavior of a TWC for NG application.

The investigation of the carbon fibre reinforced plastic components under vibration fatigue testing is known to be challenging; as it involves the analyses of both the mechanical response and the inherent self-heating behaviour which emerges due to the high-frequency testing. The paper will firstly address an open question about the so-called critical event, which is a sudden change in one of the dynamic parameters measured during the fatigue test. Past experiments showed that such a change is associated with delamination, but its onset and early growth were not clarified. Therefore, a set of interrupted fatigue tests and CT scan measurements will show the onset of delaminations and how these are correlated with the vibration parameters. The second objective is to investigate the failure behaviour under vibration fatigue and elevated environmental temperatures. The research will present both the experimental set-up for achieving fatigue under environmental conditions and the vibration data obtained from testing samples at many severity levels; both in terms of applied mechanical vibrations and thermal loads. The paper will investigate how the inherent self-heating behaviour and the applied thermal load will affect the time to failure of composites. The relationship between fatigue behaviour and environmental temperature conditions are presented in two forms. The first one is a typical S-N curve, whereas the second one, the relationship between the response phase and hot-spot temperature data. Both relationships will show how relevant is the environmental temperature in terms of fatigue behaviour for the type of components presented in this paper.

Functionally significant coronary lesions identification is necessary for appropriate revascularization. This review aims to provide an overview of the available options for coronary stenosis physiologic evaluation with a focus on the latest developments in the field.

This article presents a novel modal-based vibrothermographic approach for health monitoring of loosening bolted joints in coupled structures. In this article, the theoretical background supporting this proposed approach is firstly presented. Through finite element analyses on a simple bolted structure with varying joint conditions achieved by adjustment of bolt loads, the relationship between the bolt load and the temperature increase in the vibrating bolted joint during vibrothermographic tests was revealed. Experimental vibrothermographic tests on a more complex structure were completed to verify the observations from the finite element analyses while demonstrating the viability of the vibrothermographic approach in a laboratory environment. It has been shown that this vibrothermographic approach was able to determine the stage of a bolted joint in its progression of failure by tracing the changes in the temperature increase in relevant regions during vibrothermographic tests. Moreover, additional tests have been performed to illustrate that this approach was effective even by using only the residual responses of the structure’s vibration that were away from the resonances, which indicates it is more applicable to structures with higher damping as such structures have stronger residual responses during vibration that can be utilized. In the concluding observations of the article, the procedure for practical application of this approach is summarized, and its potential for further development is discussed.

Background: Dual antiplatelet therapy (DAPT) with aspirin and ticagrelor is recommended for at least 12 months in patients after an acute coronary syndrome (ACS). However, its underuse and premature discontinuation are common in clinical practice. We aimed to investigate the impact of a dedicated follow-up strategy with clinical visits and counselling on adherence levels to ticagrelor in patients after ACS. Methods: PROGRESS (PROmotinG dual antiplatelet therapy adheREnce in the setting of acute coronary Syndromes) is a prospective, randomized trial enrolling 400 ACS patients treated with ticagrelor. Patients were randomized to be followed-up in a dedicated outpatient clinic (In-person follow-up group, [IN-FU], n=200), or with scheduled for phone interviews only (Telephone follow-up group [TEL-FU], n=200), to assess ticagrelor adherence and related complications. DAPT disruption was defined as an interruption of the administration of the drug due to complications or other reasons of non-adherence, and divided according to the duration into short (1-5 days), temporary (6-30 days) and permanent (≥30 days) disruption. The primary endpoint was the rate of DAPT disruption at 1-year follow-up. Results: The rate of ticagrelor disruption at 1 year follow-up was higher in the TEL-FU group than in the IN-FU group (19.6 vs 5.5%; p Conclusion: The PROGRESS trial showed a net reduction in DAPT disruption in patients followed-up with clinical (in-person) follow-up visits in a dedicated outpatient clinic compared with those scheduled for phone interviews only.

Structural integrity of aerospace assets is paramount for both the safety and economy of aviation. The introduction of composites into the design of aero-structures generated several economic benefits but also led to several challenges, including fatigue damage growth and self-heating behaviour. Fatigue of metals is widely managed by calculations of damage accumulation and prediction of residual life. The same techniques do not always apply to composites fatigue, where the onset of damage and its propagation are still under investigation. Furthermore, vibration-induced fatigue is even less understood because of a handful of failure criteria available and also biased by the self-heating conditions of the material itself. The authors have underpinned one failure criterion for vibration fatigue and mapped that against self-heating and environmental temperatures. Despite the advances, several research questions were left open because of the complex multiphysics behaviour of fatigue which outreached the experimental capacity. Therefore, this research suggests a Simulation-Driven Dynamic Test (SDDT) framework that deconstructs vibration fatigue experiments into step-wise steady-state analyses. This novel approach will enable (a) investigating the failure mode mixity of the underlying failure criterion, and (b) simulating the surface temperature during the delamination growth under vibration conditions.

This research article proposes experimental methods for monitoring damage propagation of Carbon Fibre Reinforced Plastic (CFRP) components under vibration fatigue. High cycle fatigue (HCF) behaviour of composites is often not as dramatic as that of metal alloys, where any crack initiation might rapidly lead to failure. Instead, composites HCF behaviour is often a prolonged state of continuous degradation of the resin-to-fibre bonding. Furthermore, the interlaminar contact conditions at any opening delamination cause complex dynamic responses, which can be nonlinear and temperature dependent. Vibration fatigue is generally caused by large deformations which can be suitably measured by non-contact measurement systems. Hence, this paper explores the application of the scanning laser vibrometer to monitor damage propagation of CFRP components under vibration fatigue loading. The objective is to show how this measurement system can systematically implement a set of experimental methods aimed at monitoring the dynamic properties during the crack propagation caused by fatigue. The set of experimental techniques are autonomously executed by a custom-made control panel. A thermal camera is also part of the measurement chain and provides qualitative information about location of temperature hot spots and damage evolution.

This manuscript proposes, for the first time, the use of the Virtual Crack Closure Technique (VCCT) applied to a Finite Element (FE) model undergoing vibration fatigue. This work presents the simulation and validation of the early propagation in a laminate CFRP component, which is measured by the response phase during the test. Here, the FE model supports the comprehension of a psychical phenomenon that is experimentally measured but poorly understood by the only means of experiments. Two FE models are built to calculate, under the same experimental conditions of the fatigue test, the response phase at a critical moment of damage occurrence. The VCCT is applied, by using modal displacements, to measure the crack length as a function of number of cycles. The novelty of this paper is to show that the Paris’ law can be used for explaining the change in response phase while the crack opens. Both a 2D and a 3D model will be used to numerically simulate the experimental measurements. The vibration loading ratio is typically R = - 1 where the small forces at the resonance generate very large modal displacements. Hence, the paper presents a qualitative analysis carried out by the VCCT, the results of which show a strong correlation between changes the response phase and energy release rates.

Modal testing is widely used today as a means of validating theoretical (Finite Element) models for the dynamic analysis of engineering structures, prior to these models being used for optimisation of product design. Current model validation methodology is confined to linear models and is primarily concerned with (i) correcting inaccurate model parameters and (ii) ensuring that sufficient elements are included for these cases, using measured data. Basic experience is that this works quite well, largely because the weaknesses in the models are relatively sparse and, as a result, are usually identifiable and correctable. The current state-of-the-art in linear model validation has contributed to an awareness that residual errors in FE models are increasingly the consequence of some unrepresented nonlinearity in the structure. In these cases, additional, higher order parameters are required to improve the model so that it can represent the nonlinear behaviour. This is opposed to the current practice of simply refining the mesh. Again, these nonlinear features are generally localised, and are often associated with joints. We seek to provide a procedure for extending existing modal testing to enable these nonlinear elements to be addressed using current nonlinear identification methods directed at detection, characterisation, location and then quantification – in order to enhance the elements in an FE model as necessary to describe nonlinear dynamic behaviour. Emphasis is placed on the outcome of these extended methods to relate specifically to the physical behaviour of the relevant components of the structure, rather than to the nonlinear response characteristics that are the result of their presence.

It is often desired to measure the model parameters of bridges, but normally the forcing function cannot be measured so it is necessary to use output-only system identification methods. A moving vehicle provides a force on a bridge that could be used for input-output analysis, which could be superior, but the force varies in space as well as time, so existing system identification methods are not directly applicable. To address this issue, this paper proposes a new strategy to use the moving load response to identify the modal parameters. A numerically simulated simply supported Euler-Bernoulli beam of known parameters is used as an example case to test the validity of the approach. Frequency Domain Decomposition is first implemented to extract the mode shapes from the simulated acceleration responses. Then, by applying the mode superposition method, the simulated force and acceleration responses are transformed into modal space. The accelerances of five modes are then processed using the Levenberg-Marquardt method such that the three unknown parameters, namely natural frequency, damping ratio, and modal mass, of each mode are determined simultaneously. The effectiveness of the proposed method is validated by the low percentage errors (less than 1.7%) for all three identified modal parameters compared to their actual values for four of the five modes.

The main objective of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical in real-world driving operating conditions, as fuel cutoff phases or engine misfire, on the aftertreatment devices, which are generally very sensitive to these changes. This phenomenon is particularly evident when dealing with engines powered by natural gas, which requires the use of a three-way catalyst (TWC). Indeed, some deviations from the stoichiometric lambda value can interfere with the catalytic converter efficiency. In this work, a numerical &ldquo, quasi-steady&rdquo, model was developed to simulate the chemical and transport phenomena of a specific TWC for a compressed natural gas (CNG) heavy-duty engine. A dedicated experimental campaign was performed in order to evaluate the catalyst response to a defined &lambda, variation pattern of the engine exhaust stream, thus providing the data necessary for the numerical model validation. Tests were carried out to reproduce oxygen storage phenomena that make catalyst behavior different from the classic steady-state operating conditions. A surface reaction kinetic mechanism concerning CH4, CO, H2, oxidation and NO reduction has been appropriately calibrated at different &lambda, values with a step-by-step procedure, both in steady-state conditions of the engine work plan and during transient conditions, through cyclical and consecutive transitions of variable frequency between rich and lean phases. The activity also includes a proper calibration of the reactions involving cerium inside the catalyst in order to reproduce oxygen storage and release dynamics. Sensitivity analysis and continuous control of the reaction rate allowed evaluating the impact of each of them on the exhaust composition in several operating conditions. The proposed model predicts tailpipe conversion/formation of the main chemical species, starting from experimental engine-out data, and provides a useful tool to evaluate the catalyst&rsquo, s performance.

The study focuses on the understanding of failure behaviour of composites which are subjected to vibration fatigue under environmental temperature conditions. The study of vibration fatigue failure in composites can be challenging because of the coupling between mechanical and thermal properties. In fact, stiffness distribution and self-heating are typically occurring under vibration conditions. As the problem stands, the sole use of either testing or simulation would not be adequate to understand the failure behaviour fully. This paper will present both an experimental and numerical work, based on a component designed with a ply-drop feature to enhance and localise the damage occurrence. The vibration testing experiments were carried while an environmental chamber was used to control the exposure temperature. Similar experimental conditions are simulated in a finite element multi-physics environment, where the crack opening is modelled by VCCT method. The simulation environment is very challenging because both mechanical (dynamics) and thermal behaviours need to be incorporated to study the failure of a given vibration loading. Both experimental and numerical results will be qualitatively compared.

Background The twelve‑lead electrocardiogram (ECG) has become an essential tool for the diagnosis, risk stratification, and management of patients with acute coronary syndromes (ACS). However, several areas of residual controversies or gaps in evidence exist. Among them, P-wave abnormalities identifying atrial ischemia/infarction are largely neglected in clinical practice, and their diagnostic and prognostic implications remain elusive; the value of ECG to identify the culprit lesion has been investigated, but validated criteria indicating the presence of coronary occlusion in patients without ST-elevation are lacking; finally, which criteria among the multiple proposed, better define pathological Q-waves or success of revascularisation deserve further investigations. Methods The Minimizing Adverse hemorrhagic events via TRansradial access site and systemic Implementation of AngioX (MATRIX) trial was designed to test the impact of bleeding avoidance strategies on ischemic and bleeding outcomes across the whole spectrum of patients with ACS receiving invasive management. The ECG-MATRIX is a pre-specified sub-study of the MATRIX programme which aims at analyzing the clinical value of ECG metrics in 4516 ACS patients (with and without ST-segment elevation in 2212 and 2304 cases, respectively) with matched pre and post-treatment ECGs. Conclusions This study represents a unique opportunity to further investigate the role of ECGs in the diagnosis and risk stratification of ACS patients with or without ST-segment deviation, as well as to assess whether the radial approach and bivalirudin may affect post-treatment ECG metrics and patterns in a large contemporary ACS population.

The use of non-contact measurement methods for detecting and locating sources of nonlinearities can be potentially a break-through in the nowadays experimental modal analysis. The primary goal is to define more effective test strategies, whereby contact sensors will measure the nonlinear vibration responses at the best location possible. Jointed structures are a typical example where a large number of the joint can pose the question of where what and how to measure the nonlinear response. Upon the identification of one, or more, nonlinear response mode the objective is to determine where is the source of such nonlinear vibration. Nonlinearity can be characterised when its source is well defined and can be adequately tested. This paper will attempt to detect and locate the source of nonlinearity from a multi-beam jointed assembly. The approach will be carried out by using both contact and non-contact measurement methods, the results of which will be compared and evaluated. The operator to detect the source of nonlinearity will be the coherence function applied to random response data.

In this work, a numerical "quasi-steady" model was developed to simulate the chemical and transport phenomena of a specific Three-Way Catalyst (TWC) for a natural-gas heavy-duty engine. Goal of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical of real world driving operating conditions, as fuel cutoff phases or engine misfire, which produce strong deviations from stoichiometric in Air-to-Fuel (A/F) ratio and characterize catalytic converter efficiency. In fact, according to the literature it is confirmed that the catalyst dynamic behavior differs from the steady-state one due to oxygen storage phenomena. A dedicated experimental campaign has been performed in order to evaluate the catalyst response to a defined ? variation pattern of the engine exhaust stream, thus providing the data necessary for the numerical model validation. A surface reactions kinetic mechanism, concerning CH4, CO, H2 oxidation and NO reduction, has been appropriately calibrated, with a step-by-step procedure, both in steady-state conditions of the engine work plan, at different A/F ratios, and during transient conditions, through cyclical and consecutive transitions of variable frequency between rich and lean phases. The activity also includes a proper calibration of the reactions involving Cerium inside the catalyst, in order to reproduce oxygen storage and release dynamics. Sensitivity analysis and a reactions rate continuous control allowed evaluating the impact of each of them on the exhaust composition in several operating conditions. The proposed model predicts tailpipe conversion/formation of the main chemical species, starting from experimental engine-out data and provides a useful tool for evaluation of the catalyst performance.

This paper presents a research work on diagnostics using continuous scanning laser methods. Structural Health Monitoring based on laser vibrometry can exploit the ability of a scanning laser to measure vibration responses remotely both regarding temporal and spatial resolution. Therefore, it can be a powerful approach for rapid damage detection of components presenting an unhealthy dynamic behaviour. The work is focused on numerical analysis of a cantilever beam which is subjected to damage of different severity levels. The severity will be measured regarding response phase shift for a fixed excitation frequency. The simulated nodal responses of the surface being scanned by a laser beam are selected and used for simulating the spectral responses obtained from CSLDV methods. The main objective of this work is to determine the structural integrity based on an indicator obtained by referencing the relative spectral sidebands between a pristine and damage condition.

A power transformer is an important component in power trains and electrical distribution networks. Predicting its life time is desirable, especially, if a zero downtime policy is applied. However, end customers often have to deal with a lack of information and cannot always use the established methods for life time prediction. Therefore, the present paper provides an alternative way to calculate the hot spot temperature and thus, the life time of power transformers based on limited information, i.e. transformer rating information and rms current and voltage measurements (including phase angles). The transformer hot spot temperature is derived from the transformer losses and a virtual twin. Therefore, the paper provides methods i) to evaluate the separate transformer losses, i.e. core, winding and stray losses, ii) to create a simple virtual transformer twin and iii) to calculate the temperature distribution in the transformer windings and thus, the hot spot temperature. The methods are applied to one phase of a 154 kV, 15MVA power transformer. It is shown that the calculated losses and hot spot temperature matches with winding measurements available in literature.

Most nonlinear identification problems often require prior knowledge or an initial assumption of the mathematical law (model structure) and data processing to estimate the nonlinear parameters present in a system, i.e. they require the functional form or depend on a proposition that the measured data obey a certain nonlinear function. However, obtaining prior knowledge or performing nonlinear characterisation can be difficult or impossible for certain identification problems due to the individualistic nature of practical nonlinearities. For example, joints between substructures of large aerospace design frequently feature complex physics at local regions of the structure, making a physically motivated identification in terms of nonlinear stiffness and damping impossible. As a result, black-box models which use no prior knowledge can be regarded as an effective method. This paper explores the pragmatism of a black-box approach based on Polynomial Nonlinear State Space (PNLSS) models to identify the nonlinear dynamics observed in a large aerospace component. As a first step, the Best Linear Approximation (BLA), noise and nonlinear distortion levels are estimated over different amplitudes of excitation using the Local Polynomial Method (LPM). Next, a linear state space model is estimated on the non-parametric BLA using the frequency domain subspace identification method. Nonlinear model terms are then constructed in the form of multivariate polynomials in the state variables while the parameters are estimated through a nonlinear optimisation routine. Further analyses were also conducted to determine the most suitable monomial degree and type required for the nonlinear identification procedure. Practical application is carried out on an Aero-Engine casing assembly with multiple joints, while model estimation and validation is achieved using measured sine-sweep and broadband data obtained from the experimental campaign.

This research article presents a novel application of travelling wave excitation method applied to a composite bladed disc. The objective of this work is to develop a non-contact excitation method for research applications where (i) blades are non-ferromagnetic and (ii) damping is nominally high. This goal was achieved by spinning a disc, on which 14 powerful DC magnets were installed, in front the composite bladed disc. Small DC magnets were attached near each blade root to provide repellent forces. Twenty blades were manufactured with pre-pregs IM7–8552, using unidirectional stacking sequence and were installed on a rigid metallic mounting hub. The paper will present the design and make of the bladed disc, the theoretical study of normal and tangential forces in a magnet-to-magnets configuration and, finally, the experimental validation of a 14-DC magnetic exciter. The forced responses were measured in one test case by a 3D single point LDV system and in another test case by a Scanning LDV system. This work will also present an attempt to develop a DC electromagnetic exciter with its limitation and potential.

The rise of output-only modal analysis has offered an economical and efficient way to identify modal parameters of civil engineering structures, namely natural frequencies, damping ratios and mode shapes. However, since the forcing is unknown, it is not possible to directly estimate modal masses, and estimates of damping ratios may be inaccurate. With the advancement of wireless sensor networks both vehicle and bridge responses can be simultaneously measured. This offers the possibility of estimating true Frequency Response Functions (FRFs), since the vehicle acceleration gives an estimate of the force input to the bridge. Hence in principle it is possible to estimate modal masses and more accurate damping ratios. However, the spatial and temporal variation of the moving load from a passing vehicle gives challenges to this idea and precludes the direct use of existing single-input-multiple-output (SIMO) system identification methods. Even if the system is treated as a multiple-input-multiple-output (MIMO) one, the inputs are highly correlated so existing methods for these systems are not applicable either. For this reason, a two-stage strategy is proposed to modify an existing method to solve this moving load problem.

In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments.

This work presents a strategy for testing and validating structures connected together with bolted joints, which are the most common components in mechanical structures. Considering the great number of coupled mechanical structures and research studies on this subject, the authors focused this research work on bolted flanges of aircraft engine casings. In fact, the coupling of engine casings is generally obtained by a large number of joints which assure the correct sealing at the flanges’ interfaces. From a finite element (FE) modelling perspective, joints are often modelled by either rigid connections or springs, otherwise incurring a very expensive computational time. This modelling approach is not a problem when dealing with low amplitude levels of vibrations. For higher levels of vibrations, joints and flanges cannot be considered rigidly connected and that exerted flexibility at the joints’ area can determine nonlinear dynamic behaviour. This work aims to study the dynamic behaviour of bolted flanges by using modal testing performed under controlled response amplitude. Two test structures, (1) a simple bolted flange test case and (2) a sector of a Rolls-Royce aero-engine casing, are tested under high level of vibrations. Both test structures are modelled by FE method, and nonlinear elements are used for modelling the flanges’ interfaces so as to perform prediction of nonlinear responses. These predictions are eventually correlated with the measured data.

This study focuses on the variability of the dynamic response of jointed structures. It is well known that the dynamic response of joints is prone to variability issues when they are open and closed again. This paper will present one numerical example and two experimental ones on different type of structures used for studying this issue of variability. The numerical example will focus on parameters such as torque magnitude and contact area. The analysis, which is linear, will present the changes of natural frequency caused by the variation of these two parameters. The experimental examples will focus on parameters like torque magnitude, torque sequence and number of assembling. Both natural frequency and damping changes will be measured from a number of repeated sequences and analysed using statistical methods.

Complex shaped aerodynamic structures such missiles are prone to exhibit some level of nonlinear phenomena due to their aerodynamically tailored design and application. Aside from the aerodynamic and aeroelastic challenges experienced by a missile, an important but fundamental challenge encountered by a deployable missile is the inevitable concentrated structural nonlinearities which are observed around the hinge of its fins. Due to the current design and manufacturing process, the hinge of the fin of a missile often consist of complex configurations, joints and other nonlinear features that leads to concentrated structural nonlinearities. Some of the nonlinearities encountered includes off sets, piecewise linear, bilinear nonlinearity, hysteresis, coulomb friction and damping nonlinearities. These nonlinearities are frequently triggered at large vibration amplitudes caused by high pressure loads during operational flight. Activation of these nonlinearities often affect the dynamic response of the missile and in some cases lead to structural failures in the air vehicle. In this context, identifying and predicting the vibration response of aerodynamic structures with nonlinearities will be of great advantage to the present aerospace industries. In this paper the nonlinear dynamic behaviour of a prototype missile is examined using established nonlinear identification methods applied to measured data obtained from experimental test. The nonlinear identification is achieved using the acceleration surface method and the Hilbert transform FORCEVIB method, these methods are applied to sine-sweep excitation and stepped sine excitation measurements to obtain nonlinear parametric coefficients. The nonlinear experimental model was developed using the white box identification process (Detection, Characterisation and Parameter Estimation). In addition, Force controlled stepped sine experiments at several excitation levels were conducted to gain useful insight into the amplitude dependant behaviour of the missile in the existence of structural nonlinearities.

Endurance of composites materials is a critical and important factor that enables engineers to design structural components more efficiently. In fact, what it matters for many industries is to define the life of their products and, within that life, their safe operational conditions. Endurance of composites materials goes by the definition of failure criteria that can be obtained by cooperation between research groups acting both in a modelling and in an experimental framework. This research work is focussed on the development of an experimental test planning directed at testing composites components. Endurance trials for full reverse loading conditions, such as R = −1, can be executed by exploiting the first resonant mode of a beam, or a narrow plate. The major obstacles for this type of testing are (a) the fixture of the sample and (b) the amplitude of vibrations required for initiating fatigue behaviours. This paper will present two experimental methods based on (i) pulsed air-jet contactless excitation method and (ii) a novel fixture for electromagnetic shaker type testing. These methods will show how to overcome these obstacles in order to perform endurance trials on Carbon Fiber Reinforced Polymer (CFRP) components. The experimental results obtained from two sets of components are presented here and an interpretation of the fatigue behaviour of the trialled specimens will be also attempted.

The dynamic response of a structure can consist of up to six degrees of freedom (DOF). Not all of them may be present at all times in a structure, but for a detailed finite element model validation it is important to provide as much information as possible. Current contact transducers can pick up a combination of some of the mentioned DOFs, but are not able to provide all six DOFs from a single transducer. Several contact-less transducers, such as a Scanning Laser Doppler Vibrometer (SLDV), can be combined to a single measurement system that allows the determination of up to three translational degrees of freedom at a point, but they are still not providing rotational information as the laser beam is fixed to a point. Continuously Scanning Laser Doppler Vibrometer (CSLDV) methods can partly overcome this issue by travelling in small circles around the measurement location and thus also sensing the rotation around the three axes at a point. An introduction of CSLDV methods for measuring DOFs at a point is given, focussing on a method for capturing up to 5 DOFs using a lens. However, the lens can make the measurement of the in-plane rotation very difficult and impractical. This paper presents a new type of scanning device which allows measuring all six degrees of freedom at a measurement location with a single setup and a single point LDV, by combining variable small circle scans. Experimental validation of the scanning head is presented and the measurement of the last DOF, the in-plane rotation, is demonstrated.

The definition of failure is fundamental to the characterisation of fatigue strength of components and structures and is often expressed as a percentage of stiffness degradation. This article proposes a new method to capture damage initiation and structural degradation during a fatigue test, by exploiting resonance vibrations. The method entails monitoring dynamic parameters, including the phase angle between excitation and response, which suddenly changes as soon as the overall stiffness changes as a consequence of damage. In this paper, a theoretical approach based on equations of motion is presented in order to describe the possible scenarios in which a component undergoes structural degradation. In the proposed approach, an abrupt change in the time history of the stiffness of the component is assumed and analysed in both the quasi-static case at low excitation frequencies and the dynamic case, when the excitation frequency is close to the resonance frequency. The resulting analytical solution shows that any small stiffness variation is amplified by the dynamic response of the component as a large phase change, even when it is too small to be captured by the quasi-static response. The idea is successfully applied to capture the initiation of delamination in CFRP laminates, and the relative S-N curve to initiation is drawn. The experimental evidence of a critical event in the fatigue life of a component is found both in the dynamic phase response and in the base acceleration. The critical event is captured from a sudden change in the dynamic parameters of the structure as soon as a delamination is initiated. Thermography, C-scan and micrograph confirmed that the onset of delamination occurs at the moment of the critical event, after an initial stage of microcracking.