GIANLUCA D'ELIA - personale UniMoRe

Nuova ricerca

GIANLUCA D'ELIA

Ricercatore t.d. art. 24 c. 3 lett. B
Dipartimento di Scienze e Metodi dell'Ingegneria

Pubblicazioni

2024 - Experimental Setup for Non-stationary Condition Monitoring of Independent Cart Systems [Relazione in Atti di Convegno]
Jabbar, A.; D'Elia, G.; Cocconcelli, M.
abstract

The paper discusses the independent cart technology, which utilizes linear motors to move carts along a predetermined track autonomously. This technology offers control of individual speed profiles for each section along the track, frictionless propulsion mechanism, and the ability to start and stop loads quickly. Nevertheless, the initial cost of these systems is substantial, and regular condition monitoring is required to ensure optimal performance and long-term economic benefits. The paper provides an overview of various condition monitoring and signal processing techniques for analysis, including data-driven modeling with machine learning algorithms. The article presents an experimental setup based on the independent cart system and outlines a strategy for data acquisition that emphasizes specific conditions during each run of the system. The collected data is critical in monitoring the independent cart system’s condition and developing expertise in identifying different types of faults and their precise locations, utilizing hybrid modeling approaches.

2023 - Prognostics of rotating machines through generalized Gaussian hidden Markov models [Articolo su rivista]
Soave, Elia; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

Nowadays, the industrial scenario is driven by the need of costs and time reduction. In this contest, system failure prediction plays a pivotal role in order to program maintenance operations only in the last stages of the real operating life, avoiding unnecessary machine downtime. In the last decade, Hidden Markov Models have been widely exploited for machinery prognostic purposes. The probabilistic dependency between the measured observations and the real damaging stage of the system has usually been described as a mixture of Gaussian distributions. This paper aims to generalize the probabilistic function as a mixture of generalized Gaussian distributions in order to consider possible distribution variations during the different states. In this direction, this work proposes an algorithm for the estimation of the model parameters exploiting the observations measured on the real system. The prognostic effectiveness of the resulting model has been demonstrated through the analysis of several run-to-failure datasets concerning both rolling element bearings and more complex systems.

2022 - Blind deconvolution criterion based on Fourier–Bessel series expansion for rolling element bearing diagnostics [Articolo su rivista]
Soave, E.; D'Elia, G.; Cocconcelli, M.; Battarra, M.
abstract

In the last years, Blind Deconvolution methods demonstrated their effectiveness for the diagnostics of rotating machines through the extraction of impulsive signatures directly from noisy observations. Recently, in this scenario the explicit combination between Blind Deconvolution and cyclostationary theory strongly improved the fault detection ability of this diagnostic tool. This work presents a novel criterion based on the Fourier–Bessel series expansion instead of the common Fourier transform. This idea comes from the comparison between the mathematical nature of the Fourier–Bessel and the Fourier series, based on modulated and constant amplitude sinusoidal functions, respectively. The two criteria are compared through the analysis of both simulated and real vibration signals of faulty bearings. The results highlight the ability of the proposed criterion to detect the fault-related source with a lower number of characteristic cyclic frequency harmonics, strongly reducing the computational time required by the algorithm.

2022 - Digital Twins: Neural-Networks for the implementation of digital twins of gearboxes [Relazione in Atti di Convegno]
Zippo, A.; Bergamini, L.; D'Elia, G.; Pellicano, F.; Dalpiaz, G.; Iarriccio, G.; Molaie, M.
abstract

2022 - Parameter estimation algorithm for bearing prognostics through monovariate generalized Gaussian Hidden Markov Models [Relazione in Atti di Convegno]
Soave, E.; D'Elia, G.; Dalpiaz, G.; Mucchi, E.
abstract

2021 - A novel approach for increasing test efficiency and realism in multi-axial vibration control testing [Abstract in Atti di Convegno]
Monco, G.; D’Elia, G.; Troncossi, M.; Mucchi, E.
abstract

Vibration control tests are typically performed on shakers in order to replicate the in-service dynamic response of structures. The methodologies for performing vibration control tests are constantly evolving thank to the enormous advances of the available control technologies. The avant-garde test facilities have the capability to address simultaneous multi-axial vibration testing by exploiting Multi-Input Multi-Output (MIMO) control techniques. Over recent years, numerous publications point out the advantages in replicating the in-service conditions by using MIMO control strategies, satisfying the will of the environmental research community to turn multi-axis vibration control testing into the main reference procedure. This work presents a test campaign carried out on a high performance motorbike engine. In particular, the device under test (DUT) is the entire exhaust system connected to the head of the engine. A three-axial electrodynamic shaker table is used for replicating the acceleration time histories previously acquired during field-testing. The test results clearly highlight the importance of reproducing in the laboratory the operational boundary conditions. Differences between test and in-field conditions produce mechanical impedance mismatches that alter the dynamic behaviour of the DUT during the control test. The purpose of the work is to define a MIMO control methodology that makes the test conditions closer to the in-field ones, thus improving the test result reliability. As a consequence, it is possible to directly assess the dynamic response (experimentally retrieved) of the exhaust system after introducing design modifications to some components.

2021 - A rattle index formulation for single and multiple branch geartrains [Articolo su rivista]
Pizzolante, F.; Battarra, M.; D'Elia, G.; Mucchi, E.
abstract

The paper proposes an analytical procedure for the generalization of the rattle index in any type of ordinary transmission layouts, single or multiple branch, both in idle and loaded conditions. Its definition is obtained by a recursive analytical formulation of the rotational dynamics of gears. Numerical analytical studies are exploited to examine the effectiveness and reliability of the introduced index. Several geartrain layouts are investigated and results show its capability to instantaneously describe the vibro-impact events related to any gear pair of the driveline. Moreover, the general definition is shown to be a proper indicator of the potential presence of mutual interactions between different gear pairs pertaining to the same driveline. The analysis of the results reveals an excellent agreement with the expected behavior of the outlined parameter.

2021 - Gear diagnostic: Experimental data comparison of radial accelerometers, tangential accelerometers and torquemeter [Abstract in Atti di Convegno]
Zippo, A.; Pellicano, F.; Iarriccio, G.; Bergamini, L.; D'Elia, G.; Dal Piaz, G.
abstract

Industry 4.0 is the next step of the evolution of future companies in order to improve efficiency sustainability and performances. With a view to industry 4.0 and to improve the efficiency of gear transmission a measurement campaign has been performed comparing four gear pair with different surface treatment, damages and coating The experimental results on the measurement of radial accelerometers, tangential accelerometers and torque-meter measurement of spur gears rig with surface coatings, advanced pitting with a crack and damaged gears are presented and analysed with Time Synchronous Averaged (TSA) method and results are explained, comparing the effectiveness of the different sensors used to monitor the system under investigation.

2020 - A laser triangulation sensor for vibrational structural analysis and diagnostics [Articolo su rivista]
Soave, E.; D'Elia, G.; Mucchi, E.
abstract

The industrial progress has reached a level in which it is necessary to understand the behavior of mechanical components and to monitor their conditions without disassembling them. Nowadays, a suitable methodology is based on vibrational analysis usually performed through acceleration signals measured directly on the system to be tested. However, in the last years, the industrial scenario has deeply changed due to the need for time reduction, in particular, for the control operations at the end of the productive line. The genuine methods based on acceleration measurements, for example, through piezoelectric accelerometers, came into conflict with the industrial need as the sensors used for the quality control have to be easily and fastly mounted and unmounted. A valid alternative is represented by the exploitation of laser triangulation sensors that are able to measure the dynamic displacement in a contactless way, strongly reducing the (un)mounting time. The target of this paper is to highlight pros and cons of the contactless displacement analysis through laser triangulation sensors with respect to the contact one through genuine accelerometers by means of a comparison between the results obtained both for experimental modal analysis and vibrational diagnostics of rotating machines.

2020 - A tool for validating and benchmarking signal processing techniques applied to machine diagnosis [Articolo su rivista]
Buzzoni, Marco; D’Elia, Gianluca; Cocconcelli, Marco
abstract

2020 - Condition monitoring indicators for pitting detection in planetary gear units [Articolo su rivista]
Berlato, F.; D'Elia, G.; Battarra, M.; Dalpiaz, G.
abstract

In industrial field, there is an increasing demand for monitoring systems enabling predictive maintenance programs. In this context, the present work concerns the monitoring of distributed wear (pitting) in planetary gearboxes. For this purpose, some metrics of the synchronous average of the vibration signal, based on the statistical moment of the fourth order, are present in literature; in this paper, a new indicator is proposed, namely NA4mod. The effectiveness of this metric in identifying the early stage of pitting has been evaluated by conducting an accelerated life test of about 700 hours on a test bench using a back-to-back configuration. The paper introduces the proposed metric, describes the test, presents and dis-cusses the results. Metric NA4mod exhibits satisfactory capability to detect pitting with better reliability than other metrics in literature. In addition, the metric is shown to be sensitive to both early stage damage and pitting severity in the final stage. Results are verified by means of wavelet-transform analysis.

2020 - Motor Current Cyclic-Non-Stationary Analysis for Bearing Diagnostic [Relazione in Atti di Convegno]
D’Elia, G.; Cocconcelli, M.; Strozzi, M.; Mucchi, E.; Dalpiaz, G.; Rubini, R.
abstract

The Motor Current Signature Analysis (MCSA) is a research area focused on the diagnosis of components of electric motors based on post-processing of the current signal mainly. In particular, the bearing diagnostics is based on two different assumptions: the fault on the bearing causes a vibration of the shaft it supports, so there is an air gap variation between stator and rotor causing a modulation in the current signal; the fault on the bearing hinders the rotation of the shaft, so it can be modeled as an additional loading torque that the motor satisfies increasing the current signal. In this paper, a cyclic-non-stationarity analysis of the motor current is used to assess the status of ball-bearings in servomotors, running at variable speed. Both speed of the motor and motor current are provided by the control loop of the servomotor, that is no external sensors are used. The cyclic nature of the application allows an average of the cyclic-cyclic order maps to increase the signal-to-noise ratio. The proposed technique is successfully applied to both healthy and faulty bearings.

2020 - Motor current cyclic-non-stationarity analysis for bearing diagnostic [Relazione in Atti di Convegno]
D'Elia, G.; Cocconcelli, M.; Strozzi, M.; Mucchi, E.; Dalpiaz, G.; Rubini, R.
abstract

2019 - A vibration-based method for contact pattern assessment in straight bevel gears [Articolo su rivista]
Buzzoni, Marco; D'Elia, Gianluca; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

So far, the study of gear contacts in lightly loaded gears by means of vibration analysis has not been sufficiently addressed in the literature. Indeed, the complex nature of the physical phenomena involved makes the vibration analysis extremely challenging. This paper deals with the development and the validation of an approach for the contact pattern assessment in straight bevel gears within a pass/fail decision process. The proposed methodology is based on blending vibration-based condition indicators with classification algorithms in order to discriminate proper contact patterns from improper ones. Specifically, three different classification algorithms have been investigated: the Naive Bayes classifier, the weighted k-Nearest Neighbors classifier and a novel classifier proposed by the authors. The classifier accuracies are evaluated with a MC cross-validation that includes an extended experimental campaign consisting of more than one hundred different straight bevel gear pairs. The results show that the proposed classifier is superior to the other considered classifiers in terms of average accuracy. Finally, this manuscript proposes an original methodology that provides a reliable and quick assessment of the contact pattern in straight bevel gears considering different speeds, gear parameters and surface finish. (C) 2018 Elsevier Ltd. All rights reserved.

2019 - Fourier-Bessel series expansion based blind deconvolution method for bearing fault detection [Relazione in Atti di Convegno]
Soave, E.; D'Elia, G.; Dalpiaz, G.
abstract

In the last few years blind deconvolution techniques proved to be useful in order to extract impulsive patterns related to bearing fault from noisy vibration signals. Recently, a novel blind deconvolution method based on the generalized Rayleigh quotient has been proposed and an iterative algorithm related to the maximization of the cyclostationarity of the source has been defined. This paper presents a new condition indicator that exploit the Fourier-Bessel series expansion for the computation of a new cyclostationarity index that drives the maximization problem for the extraction of the excitation source. The main target of this work is to compare the results obtained through the exploitation of the Fourier-Bessel transform with respect to the classic Fourier transform in term of lower number of cyclic frequencies required for the algorithm. The comparison between the application of the two different methods involves both simulated and real signal taking into account a bearing fault. The results prove the capability of the new indicator to extract the impulsive source without the need of a set of cyclic frequencies but only with the first one, with a strong reduction of the computational time.

2019 - On the Nyquist frequency of random sampled signals [Relazione in Atti di Convegno]
Hamadache, M.; D'Elia, G.; Dalpiaz, G.
abstract

In modern industry, the wide use of reliable and sophisticated sensors with their connection to internet has introduced the phenomena of Big Data, especially in the field of condition monitoring systems (CMSs) in e-maintenance applications. In particular, in the case of vibration signals, high-performance acquisition systems are required, characterized by anti-aliasing filtering and high uniform sampling rate, in order to properly digitalize the meaningful frequency content of the signals. In this context, the capability of non-uniform random sampling (RS) is assessed in this work. While in different fields, such astronomy, structural and biomedical studies, the RS is a problem to be resolved, due to the unavailability of samples at specific instants (missing data problem), in the field of fault detection & diagnosis (FDD), RS can be a chosen sampling method thanks to its advantages: Anti-aliasing property and low average sampling rate. Therefore, this paper focuses on studying the anti-aliasing property of the random sampled data, verifying the criterion proposed in literature for establish the Nyquist frequency, and analyzing its sensitivity to the sampling parameters. This study is carried out using simulated signals and computing the spectral window, giving the Nyquist frequency for different random sampling parameters; moreover, a spectral analysis method, the Schuster periodogram, is used to verify when the spectrum is actually free of alias. The results show that the Nyquist frequency depends on the numerical accuracy of the randomly generated time instants.

2019 - On the diagnostics of two degrees of freedom planetary gearboxes [Abstract in Atti di Convegno]
D'Elia, Gianluca; Dalpiaz, G.; Mucchi, E.
abstract

2019 - Stall and Surge in Wet Compression: Test Rig Development and Experimental Results [Articolo su rivista]
Munari, Enrico; D'Elia, Gianluca; Morini, Mirko; Pinelli, Michele; Spina, Pier Ruggero
abstract

Wet compression is a strategy adopted to increase the power output of gas turbines, with respect to dry conditions, usually also incrementing the operating range of the compressor. However, stall and surge are two aerodynamic instabilities which depend on many factors, and they are expected to occur even in wet compression at low flow rates. Despite the many studies carried out in the last 80 years, literature does not offer many works concerning these instability phenomena in wet compression. In this paper, an experimental analysis of stall and surge in wet compression conditions is carried out on an axial-centrifugal compressor installed in an existing test rig at the Engineering Department of the University of Ferrara. The intake duct was implemented with a water injection system (WIS) which allows the uniform mixing of air and water before the compressor inlet. The control and data acquisition system of the test bench was updated with new hardware and software to obtain faster data sampling. Transient and steady-state tests were carried out to make a comparison with the experimental results in dry conditions. The analysis was carried out using traditional thermodynamic sensors, by means of both classic postprocessing techniques and cyclostationary analysis. The aim is to (i) evaluate the influence of wet compression on the stable performance of the compressor, (ii) qualitatively identify the characteristics of stall and surge in wet compression, and (iii) demonstrate the reliability of cyclostationary analysis in wet compression conditions for stall and surge analysis.

2019 - UniVibe: A novel user-friendly software for automated condition monitoring and diagnostics of geared transmission [Relazione in Atti di Convegno]
D'Elia, G.; Daini, I.; Romagnoli, L.; Mucchi, E.
abstract

Nowadays, huge emphasis is given to research on diagnostic tools in order to prevent and monitor the health status of gears and bearings. However, the link between advanced signal processing techniques and ease of use is still missing in commercial software tools. Actually, softwares that implement advanced signal processing techniques leak in ease user interaction and automated diagnostic procedures. Authors have developed a commercial software tool, called UniVibe, that attempts to fill the gap between high sensitivity in the diagnostics of faults in complex geared transmission and user-friendly interface. This work focuses on the description of the UniVibe core, highlighting its diagnostic capabilities on the basis of a real industrial case. Specifically, the automated procedure that shepherds the user to the successfully fault diagnosis of a complex geared transmission is pointed out.

2019 - Vibrational analysis and diagnostics by means of laser triangulation sensor [Relazione in Atti di Convegno]
Soave, Elia; D'Elia, Gianluca; Mucchi, Emiliano
abstract

Nowadays, vibrational analysis is one of the most exploited methods in order to understand the behavior of mechanical components, by means of modal testing, and to monitor their conditions, by means of vibrational diagnostics. This kind of analysis has usually been performed through acceleration measures and exists a truly rich literature about this. However, in the last years, the genuine methodologies based on acceleration measurement, e.g. through piezoelectric accelerometers, came into conflict with the industrial need for time reduction. The sensors used have to be easily removable in order to speed up the control operation, for example at the end of the productive line. In this scenario a valid solution is represented by the use of laser triangulation sensors that are able to measure the dynamic displacement without the contact with the component surface and consequently with very high decrement of the time needed to mount and unmount. This work is focused on a comparison of the results obtained by piezoelectric accelerometer and laser triangulation sensor both for vibrational analysis, i.e. experimental modal analysis and vibrational diagnostics of rotating machines. This paper highlights pros and cons of the contactless displacement analysis with respect to the accelerometer measurements.

2018 - A diagnostic protocol for the monitoring of bearing fault evolution based on blind deconvolution algorithms [Relazione in Atti di Convegno]
Buzzoni, M.; Elia, Soave; D’Elia, Gianluca.; Mucchi, E.; Dalpiaz, G.
abstract

The detection and identification of bearing faults at their initial stage is pivotal in order to avoid catastrophic failures. However, the vibration contribution related to early stage bearing faults are frequently weak and masked by strong background noise and mechanical interferences. In this scenario, blind deconvolution algorithms can be exploited for extracting impulsive patterns related to incipient bearing faults. Maximum Correlated Kurtosis Deconvolution (MCKD) and Multipoint Optimal Minimum Entropy Deconvolution Adjusted (MOMEDA) proved to be effective for fault diagnosis in rotating machines. However, their effectiveness on monitoring the progressive degradation of rolling element bearings has not yet been exhaustively studied. In this paper, the experimental data from an endurance test are investigated by means of MCKD and MOMEDA. The results in terms of incipient fault detection and fault identification accuracy are discussed from different perspectives, highlighting advantages and limits of such blind deconvolution approaches. In particular, an original diagnostic protocol is proposed, based on a condition indicator computed from the cumulative of the blind deconvolution maximized criterion combined with a non-parametric statistical threshold. The proposed indicator is sensitive to the fault degradation as well as the fault type.

2018 - An algorithm for the simulation of faulted bearings in non-stationary conditions [Articolo su rivista]
D'Elia, Gianluca; Cocconcelli, Marco; Mucchi, Emiliano
abstract

In the field of condition monitoring the availability of a real test-bench is not so common. Furthermore, the early validation of a new diagnostic technique on a proper simulated signal is crucial and a fundamental step in order to provide a feedback to the researcher and to increase the chances of getting a positive result in the real case. In this context, the aim of this paper is to detail a step-by-step analytical model of faulted bearing that the reader could freely and immediately use to simulate different faults and different operating conditions. The vision of the project is a set of tools accepted by the community of researchers on condition monitoring, for the preliminary validation of new diagnostics techniques. The tool proposed in this paper is focused on ball bearing, and it is based on the well-known model published by Antoni in 2007. The features available are the following: selection of the location of the fault, stage of the fault, cyclostationarity of the signal, random contributions, deterministic contributions, effects of resonances in the machine and working conditions (stationary and non-stationary). The script is provided for the open-source Octave environment. The output signal is finally analysed to prove the expected features.

2018 - Blind deconvolution based on cyclostationarity maximization and its application to fault identification [Articolo su rivista]
Buzzoni, Marco; Antoni, Jérôme; D'Elia, Gianluca
abstract

Blind deconvolution algorithms prove to be effective tools for fault identification, being able to extract excitation sources from noisy observations only. In this scenario, the present paper introduces a novel blind deconvolution method based on the generalized Rayleigh quotient and solved by means of an iterative eigenvalue decomposition algorithm. This approach not only is characterized by a weighting matrix that drives the deconvolution process, but can also be easily adapted to arbitrary criteria. Based on this framework, a novel criterion rooted on the maximization of the cyclostationarity of the excitation – as typically encountered with machine faults – is proposed and compared with other blind deconvolution methods existing in the literature. The comparisons involve both synthesized and real vibration signals, taking into account a gear tooth spall and an outer race bearing fault. The results reveal superior capability to recover impulsive cyclostationary sources with respect to other blind deconvolution methods, even in the presence of impulsive noise or under non-constant speed.

2018 - Development of an Indicator for the Assessment of Damage Level in Rolling Element Bearings Based on Blind Deconvolution Methods [Articolo su rivista]
Buzzoni, Marco; Soave, Elia; D'Elia, Gianluca; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

The monitoring of rolling element bearings through vibration-based condition indicators plays a crucial role in the modern machinery. The kurtosis is a very efficient indicator being sensitive to impulsive components within the vibration signature that often are symptomatic of localized faults. In order to improve the diagnostic performance of the kurtosis, blind deconvolution algorithms can be exploited in order to detect bearing faults and, most importantly, their position. In this scenario, this paper focuses on the development of a novel condition indicator specifically designed for the damage assessment in rolling element bearings. The proposed indicator allows to track the bearing degradation process taking into account three different possible positions: outer race, inner race, and rolling element. This indicator fits real-Time monitoring procedures allowing for the automatic detection and identification of the bearing fault. The validation of the proposed indicator has been carried out by means of both simulated signal and a run-To-failure experiment. The results highlight that the proposed indicator is able to detect more efficiently the fault occurrence and, most importantly, quicker than other established techniques.

2018 - Experimental Investigation of Vibrational and Acoustic Phenomena for Detecting the Stall and Surge of a Multistage Compressor [Articolo su rivista]
Munari, Enrico; D'Elia, G.; Morini, M.; Mucchi, E.; Pinelli, M.; Spina, P. R.
abstract

2018 - Stall and surge in wet compression: Test rig development and experimental results [Relazione in Atti di Convegno]
Munari, E.; D'Elia, G.; Morini, M.; Pinelli, M.; Spina, P. R.
abstract

Wet compression is a strategy adopted to increase the poweroutput of gas turbines, with respect to dry conditions, usuallyalso incrementing the operating range of the compressor.However, stall and surge are two aerodynamic instabilities whichdepend on many factors, and they are expected to occur even inwet compression at low flow rates. Despite the many studiescarried out in the last 80 years, literature does not offer manyworks concerning these instability phenomena in wetcompression. In this paper, an experimental analysis of stall andsurge in wet compression conditions is carried out on an axialcentrifugal compressor installed in an existing test rig at theEngineering Department of the University of Ferrara. Somemodifications of the test rig were necessary.The intake duct was implemented with a water injectionsystem which, by means of water spray injectors, allows theuniform mixing of air and water before the compressor inlet. Thecontrol and data acquisition system of the test bench was updatedwith new hardware and software to obtain faster data sampling.Transient and steady-state tests were carried out to make acomparison with the experimental results in dry conditions. Theanalysis was carried out using traditional thermodynamicsensors, by means of both classic post-processing techniques,and cyclostationary analysis.The aim is to i) evaluate the influence of wet compressionon the stable performance of the compressor ii) qualitativelyidentify the characteristics of stall and surge in wet compressionby means of sensors which were shown to capture thesephenomena well and iii) demonstrate the reliability ofcyclostationary analysis in wet compression conditions for stalland surge analysis.

2017 - Combining blind separation and cyclostationary techniques for monitoring distributed wear in gearbox rolling bearings [Articolo su rivista]
D'Elia, G.; Cocconcelli, Marco; Mucchi, E.; Dalpiaz, G.
abstract

This work seeks to study the potential effectiveness of the Blind Signal Extraction (BSE) as a pre-processing tool for the detection of distributed faults in rolling bearings. In the literature, most of the authors focus their attention on the detection of incipient localized defects. In that case, classical techniques (i.e. envelope analysis) are robust in recognizing the presence of the fault and its characteristic frequency. However, when the fault grows, the classical approach fails, due to the change of the fault signature. De facto, in this case the signal does not contain impulses at the fault characteristic frequency, but more complex components with strong non-stationary contents. Moreover, signals acquired from complex machines often contain contributions from several different components as well as noise; thus the fault signature can be hidden in the complex system vibration. Therefore, pre-processing tools are needed in order to extract the bearing signature, from the raw system vibration. In this paper the authors focalize their attention on the application of the BSE in order to extract the bearing signature from the raw vibration of mechanical systems. The effectiveness and sensitivity of BSE is here exploited on the basis of both simulated and real signals. Among different procedures for the BSE computation, the Reduced-Rank Cyclic Regression algorithm (RRCR) is used. Firstly a simulated signal including the effect of gear meshing as well as a localized fault in bearings is introduced in order to tune the parameters of the RRCR. Next, two different real cases are considered, a bearing test-rig as an example of simple machine and a gearbox test-rig as an example of complex machine. In both examples, the bearings were degreased in order to accelerate the wear process. The BSE is compared with the usual pre-processing technique for the analysis of cyclostationary signals, i.e. the extraction of the residual signal. The fault detection is carried out by the computation of the Integrated Cyclic Modulation Spectrum on the extracted signals. The results indicate that the extracted signals via BSE clearly highlight the distributed fault signature, in particular both the appearance of the faults as well as their development are detected, whilst noise still hides fault grow in the residual signals.

2017 - Diagnosis of Localized Faults in Multistage Gearboxes: A Vibrational Approach by Means of Automatic EMD-Based Algorithm [Articolo su rivista]
Buzzoni, M.; Mucchi, E.; D'Elia, G.; Dalpiaz, G.
abstract

The gear fault diagnosis on multistage gearboxes by vibration analysis is a challenging task due to the complexity of the vibration signal.The localization of the gear fault occurring in a wheel located in the intermediate shaft can be particularly complex due to the superposition of the vibration signature of the synchronous wheels. Indeed, the gear fault detection is commonly restricted to the identification of the stage containing the faulty gear rather than the faulty gear itself. In this context, the paper advances a methodology which combines the Empirical Mode Decomposition and the Time Synchronous Average in order to separate the vibration signals of the synchronous gears mounted on the same shaft. The physical meaningful modes are selected by means of a criterion based on Pearson’s coefficients and the fault detection is performed by dedicated condition indicators. The proposed method is validated taking into account simulated vibrations signals and real ones.

2017 - Experimental investigation of vibrational and acoustic phenomena for detecting the stall and surge of a multistage compressor [Relazione in Atti di Convegno]
Munari, Enrico; D'Elia, Gianluca; Morini, Mirko; Mucchi, Emiliano; Pinelli, Michele; Spina, Pier Ruggero
abstract

Nowadays, the operative range limit of compressors is still a key aspect of the research into turbomachinery. In particular, the study of the mass flow rate lower limit represents a significant factor in order to predict and avoid the inception of critical working conditions and instabilities such as stall and surge. The importance of predicting and preventing these dangerous phenomena is vital since they lead to a loss of performance and severe damage to the compression system and the compressor components. The identification of the typical precursors of these two types of compressor unstable behaviors can imply many advantages, in both stationary and aeronautic applications, such as i) avoiding the loss of production (in industry) and efficiency of systems and ii) reducing the cost of maintenance and repairing. Many approaches can be adopted to achieve this target, but one of the most fascinating is the vibroacoustic analysis of the compressor response during operation. At the Engineering Department of the University of Ferrara, a test bench, dedicated to the study of the performance of an aeronautic turboshaft engine multistage compressor, has been equipped with a high frequency data acquisition system. A set of triaxle accelerometers and microphones, suitable for capturing broad-band vibration and acoustic phenomena, were installed in strategic positions along the compressor and the test rig. Tests were carried out at different rotational speeds, and with two different piping system layouts, by varying the discharge volume and the position of the electric control valve. Moreover, two different methodologies were adopted to lead the compressor towards instability. This experimental campaign allowed the inception of compressor stall and surge phenomena and the acquisition of a great amount of vibro-acoustic data which were firstly processed through an innovative data analysis technique, and then correlated to the thermodynamic data recorded. Subsequently, the precursor signals of stall and surge were detected and identified demonstrating the reliability of the methodology used for the study of compressor instability. The results of this paper can provide a significant contribution to the knowledge of the inception mechanisms of these instabilities. In particular, the experimental data can offer a valid support to the improvement of surge and stall avoidance (or control) techniques since it presents an alternative way of analyzing and detecting unstable compressor behavior characteristics by means of non-intrusive measurements.

2017 - METRICHE VIBRAZIONALI PER IL MONITORAGGIO DELL’USURA DISTRIBUITA IN RIDUTTORI EPICICLOIDALI [Relazione in Atti di Convegno]
Francesco, Berlato; D'Elia, G.; Mucchi, E.; Dalpiaz, G.
abstract

Oggigiorno il monitoraggio dei riduttori è un’esigenza sempre più sentita ed importante nell’industria. In particolare, questo lavoro riguarda il monitoraggio dell’usura distribuita (pitting) nei riduttori epicicloidali, mediante l’impiego di alcune metriche della media sincrona del segnale vibratorio, basate sul momento statistico del quart’ordine: si tratta di FM4, NA4 e NA4*; si propone inoltre un nuovo indicatore di condizione chiamato NA4mod. L’efficacia di queste metriche nell’individuare l’insorgere di difetti distribuiti è stata valutata e confrontata conducendo una prova di usura accelerata su banco prova in configurazione back-to-back della durata di circa 700 ore, in cui uno dei due riduttori è stato portato a fine vita. L’articolo introduce le metriche impiegate, descrive la prova condotta e ne presenta e discute i risultati. La nuova metrica proposta, NA4mod, ha evidenziato una soddisfacente capacità di rilevamento dell’insorgere del pitting, con maggiore affidabilità rispetto ad altre metriche presenti in letteratura; NA4mod risulta inoltre sensibile sia all’innesco sia all’evoluzione del pitting.

2017 - On the identification of the angular position of gears for the diagnostics of planetary gearboxes [Articolo su rivista]
D'Elia, G; Mucchi, E.; Cocconcelli, Marco
abstract

Generally, in planetary gearbox diagnostics, vibration transducers are placed on the gearbox case near the ring gear. The relative angular position of the planet gears with respect to the transducer is a useful information for the evaluation of vibration signals related to planet/sun gears. This angular position is usually unknown, or it is known with a large tolerance causing serious difficulties in both gears and bearing diagnostics. In fact, noise and spurious component from healthy planets could overhang the informative content about incipient faults. The present work seeks to propose two alternative methods for the identification of the angular position of the planet gears with respect to the transducer. The first one is based on the study of how the power flows inside the Time Synchronous Average of the ring gear, whilst the second method is based on a modified statistical parameter such as the Crest Factor. The effectiveness of these methods is assessed on the basis of actual vibration signals acquired from a faulty planetary gearbox. The knowledge of the exact angular position of the planet gears allows the diagnostics of both gears and bearings, as proven by extensive experimental activities reported in the paper.

2017 - Step-by-step algorithm for the simulation of a faulted gearbox [Relazione in Atti di Convegno]
D’Elia, Gianluca; Cocconcelli, Marco; Rubini, Riccardo
abstract

This paper focuses on the simulation of expected vibration signal of a faulted gearbox. The main mechanical components simulated are ball bearings and ordinary gears. In a previous work [1] the authors presented a step-by-step algorithm for the simulation of faulted bearings. In this paper the model has been extended to include ordinary gears and their most common faults, such as pitting or crack on a tooth, the presence of backlash or bent shafts. Regarding the ball bearings model, the simulation takes into account the selection of the location of the fault's type, the stage of the fault, cyclostationarity of the signal, random contributions, deterministic contributions, eects of resonances in the machine and working conditions. Although several detailed models are available in literature, the scientic papers just outline the theoretical foundations of assumptions and features of the model - as supposed - leaving to the reader the task of converting all the procedure in lines of code. This is in contrast with the idea of "reproducible research", which posits the possibility of being able to reproduce the proposed procedure and verifying the conclusions of the paper. As soon as the model is veried by scientic community, it could be used as preliminary test-bench, for the validation of new diagnostics techniques that the reader could develop in the future. This project has been developed under a Creative Commons license (Attribution-ShareAlike 4.0 International). The reader could freely and immediately use to simulate dierent faults and dierent operating conditions on ordinary gearbox. The script is provided for the open- source Octave environment. The output signal is nally analyzed to prove the expected features. [1] G. D'Elia, M. Cocconcelli, E. Mucchi, R. Rubini and G. Dalpiaz, Step-by-step algorithm for the simulation of faulted bearings in non-stationary conditions, ISMA 2016, Leuven, Belgium, 19-21 September 2016.

2017 - Wind turbine loads induced by terrain and wakes: An experimental study through vibration analysis and Computational Fluid Dynamics [Articolo su rivista]
Castellani, Francesco; Buzzoni, Marco; Astolfi, Davide; D'Elia, Gianluca; Dalpiaz, Giorgio; Terzi, Ludovico
abstract

A wind turbine is a very well-known archetype of energy conversion system working at non-stationary regimes. Despite this, a deep mechanical comprehension of wind turbines operating in complicated conditions is still challenging, especially as regards the analysis of experimental data. In particular, wind turbines in complex terrain represent a very valuable testing ground because of the possible combination of wake effects among nearby turbines and flow accelerations caused by the terrain morphology. For these reasons, in this work, a cluster of four full-scale wind turbines from a very complex site is studied. The object of investigation is vibrations, at the level of the structure (tower) and drive-train. Data collected by the on-board condition monitoring system are analyzed and interpreted in light of the knowledge of wind conditions and operating parameters collected by the Supervisory Control And Data Acquisition (SCADA). A free flow Computational Fluid Dynamics (CFD) simulation is also performed, and it allows one to better interpret the vibration analysis. The main outcome is the interpretation of how wakes and flow turbulences appear in the vibration signals, both at the structural level and at the drive-train level. Therefore, this wind to gear approach builds a connection between flow phenomena and mechanical phenomena in the form of vibrations, representing a precious tool for assessing loads in different working conditions.

2016 - Analyzing wind turbine flow interaction through vibration data [Relazione in Atti di Convegno]
Castellani, Francesco; D'Elia, Gianluca; Astolfi, Davide; Mucchi, Emiliano; Dalpiaz, Giorgio; Terzi, Ludovico
abstract

Wind turbines commonly undergo non-stationary flow and, not rarely, even rather extreme phenomena. In particular, rough terrains represent a challenging testing ground, because of the combination of terrain-driven flow and wakes. It is therefore crucial to assess the impact of dynamic loads on the turbines. In this work, tower and drive-train vibrations are analyzed, from a subcluster of four turbines of a wind farm sited in a very complex terrain. The main outcome of the study is that it is possible to start from the analysis of wind conditions and interpret how wakes manifest in the vibrations of the turbines, both at structural level (tower vibrations) and at the drive-train level. This wind to gear approach therefore allows to build a connection between a flow phenomenon and a mechanical phenomenon (vibrations) and can be precious to assess loads in different working conditions.

2016 - Step-by-step algorithm for the simulation of faulted bearings in non-stationary conditions [Relazione in Atti di Convegno]
D'Elia, Gianluca; Cocconcelli, Marco; Mucchi, E.; Rubini, Riccardo; Dalpiaz, Giorgio
abstract

The early validation of a new diagnostic technique on a proper simulated signal is crucial, in order to provide a feedback to the researcher and increasing the chances of getting a positive result in the real case-studies. While dozens of comprehensive models of ball bearing have proposed in literature so far, the complexity of these models accordingly increased. As supposed, the scientific papers just outline the theoretical foundations of assumptions and features of the model, leaving the reader the task of converting all in lines of code. The aim of this paper is to detail step-by-step an analytical model of faulted bearing that the reader could freely and immediately use to simulate different faults and different operating conditions. It is based on the model proposed by Antoni in 2007 and the features available are the following: selection of the location of the fault, stage of the fault, cyclostationarity of the signal, random contributions, deterministic contributions, effects of resonances in the machine and working conditions (stationary and non-stationary).

2015 - Evolution of gear condition indicators for diagnostics of planetary gearboxes [Relazione in Atti di Convegno]
D'Elia, Gianluca; Cocconcelli, Marco; Rubini, Riccardo; Dalpiaz, Giorgio
abstract

In the last decades diagnostics of planetary gearboxes became a necessity in different fields, such as Industry and Army, and a plethora of gear condition indicators (CI) were proposed. Among the others: FM4, NA4, ER and SI. All of these CIs have proved to be effective in specific conditions, but it is a matter of fact that several indicators may lead to different decisions, while the literature only reports case studies with positive responses for each CI. In this paper a critical comparison among different CIs is carried out during a complete life of a gearbox. In particular a test bench runs a three-stage gearbox for a non-stop target period of 700 hours. At the end of the test the presence of faults are evident from the analysis of the vibrations. Moreover two original CI, namely RV and CRV, have been introduced and tested. The evolution of CIs response is monitored during the test, showing different behavior in both parameter sensitivity and response dynamics. The data analysis allows a choice of the most promising indicators

2015 - On the Diagnostics of Planet Gear Bearings [Relazione in Atti di Convegno]
D'Elia, G.; Cocconcelli, M.; Mucchi, E.; Dalpiaz, G.
abstract

Bearings play a pivotal role in the rotating machine scenario, due to their ubiquity and importance. A crowd of signal processing procedures have been developed in order to extract information about incipient localised faults in bearings from the measured acceleration signals. In the case of bearings for planetary gear applications, additional complexities are introduced. First, transducers may only be placed on the exterior of the gearbox, usually rather far from bearings. Second, the rotational axes of the planet gears are not fixed, i.e. they move with respect to the gearbox housing and thus to the transducers. As a result, the vibration signature of the planet gear bearings can be altered by the variable transfer path. In this condition, the standard signal processing techniques fail, and the characteristic bearing fault frequencies cannot be determined. On the other hand, global indicators of the bearing health may be used, but they are not able to specify where the fault is located. In this paper, a pre-processing technique is applied to the vibration signals of a planetary gearbox in order to highlight the planet gear bearing signatures. This technique is based on the McFaddens time synchronous averaging method to extract the vibration data relative to each planet. Then, cyclostationary techniques such as the Cyclic Power has be applied to extract the bearing signature.

2015 - On the use of cyclostationary indicators in IC engine quality control by cold tests [Articolo su rivista]
Delvecchio, Simone; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

This paper addresses the use of first- and second-order cyclostationary (CS1 and CS2) tools to process the vibration signals picked up from internal combustion (IC) engines during cold tests. This type of analysis is needed in order to detect and diagnose irregular operations for quality control purposes. The effectiveness of indicators such as Mean Instantaneous Power (MIP), Degree of Cyclostationarity (DCS alpha) and Indicator of Cyclostationarity (ICSnx) in detecting assembly faults has been tested on real signals concerning three faulty conditions: inverted piston, connecting rod with incorrectly tightened screws, connecting rod without one bearing cap. In the past several authors have mainly used cyclostationary metrics for diagnostics purposes in rolling bearings and gear systems. Moreover, a signal model, qualitatively reproducing the features of actual cold test signals, has been formulated and used in order to preliminarily study the influence of signal parameters on the Indicators of Cyclostationarity. The results indicate that the cyclostationary tools - mainly CS2 tools - are effective in detecting and diagnosing all tested faulty conditions. In particular, indicator ICS2x is highly sensitive to faults and it is suitable as pass/fail tool in quality control at the end of the engine assembly line. As a further second-order cyclostationary metric, the MIP is effective for detection, as well for fault identification, since it is able to localize regular and fault events within the engine cycle. In addition DCS alpha effectively characterizes the CS2 periodicities, giving the cyclic order distribution. Since these CS2 tools require a moderate computation cost, they can be considered ready for on-line industrial applications.

2014 - On the use of Vibration Signal Analysis for Industrial Quality Control: Part I [Relazione in Atti di Convegno]
D'Elia, Gianluca; Delvecchio, Simone; Malago', Marco; Dalpiaz, Giorgio
abstract

Vibration signals can be successfully captured and analyzed for quality control at the end of the production line. Various signal processing techniques and their applications are presented in this paper. These applications demonstrate the importance of selecting proper signal processing tools in order to extract the most reliable information from the signals. The presented applications regards tooth fault detection in helical gears and the detection of assembly faults in diesel engines by means of cold test technology.

2014 - On the use of Vibration Signal Analysis for Industrial Quality Control: Part II [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Malago', Marco; Dalpiaz, Giorgio
abstract

Vibration signals can be successfully captured and analyzed for quality control at the end of the production line. Various signal processing techniques and their applications are presented in this paper. These applications demonstrate the importance of selecting proper signal processing tools in order to extract the most reliable information from the signals. The presented applications regards ball bearings and threshing process in harvesting machines.

2014 - Use of cyclostationary analysis for rust detection on the hub of heavy duty wheels [Relazione in Atti di Convegno]
Mucchi, Emiliano; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

Heavy duty wheels are used in applications as automatic vehicles and are mainly composed of a polyurethane tread glued to a cast iron hub. In the manufacturing process, the adhesive application between tread and hub is the most critical assembly phase, since it is completely made by an operator and a contamination of the link area may happen. Furthermore the presence of rust on the hub surface can contribute to worsen the adherence interface, reducing the wheel operating life. In this scenario, a fault detection procedure to be use at the end of the manufacturing process has been developed. The fault detection procedure is based on vibration processing techniques. In this paper, several wheels with rust presence on the hub have been manufactured ‘ad hoc’ with anomalies similar to the ones that can really be originated. Signal processing techniques have been used in order to detect the presence of rust; in particular, cyclostationary theory is applied to extract information from the frequency/order domain of the processed signals. Indicators based on cyclostationary theory can be considered as the key parameters to be adopted in a monitoring test station at the end of the production line.

2013 - Advances in Condition Monitoring of Machinery in Non-Stationary Operations [Curatela]
Dalpiaz, G.; Rubini, Riccardo; D'Elia, G.; Cocconcelli, Marco; Chaari, F.; Zimroz, R.; Bartelmus, W.; Haddar, M.
abstract

The growing interest of the industrial world on the topics covered by the CMMNO involves the fields of packaging, automotive, agricultural, mining, processing and wind machines in addition to that of the systems for data acquisition. The participation of speakers and visitors from industry makes the event an opportunity for immediate assessment of the potential applications of advanced methodologies for the signal analysis. The condition monitoring of machines, particularly if operating in non-stationary conditions, requires the measurement of appropriate parameters related to the operating conditions and wear to be monitored and the subsequent processing of the acquired signals for diagnostic purposes

2013 - Application of cyclostationary indicators for the diagnostics of distributed faults in ball bearings [Relazione in Atti di Convegno]
D'Elia, G.; Delvecchio, S.; Cocconcelli, M.; Dalpiaz, G.
abstract

This paper deals with the detection of distributed faults in ball bearings. In literature most of the authors focus their attention on the detection of incipient localized defects. In that case classical techniques (i.e. statistical parameters, envelope analysis) are robust in recognizing the presence of the fault and its characteristic frequency. In this paper the authors focalize their attention on bearings affected by distributed faults, due to the progressive growing of surface wear or to low-quality manufacturing process. These faults can not be detected by classical techniques; in fact, in this case the signal does not contain impulses at the fault characteristic frequency, but more complex components with strong non-stationary contents. Distributed faults are here detected by means of advanced tools directly derived from the theory of cyclostationarity. In particular three metrics - namely Integrated Cyclic Coherence (ICC), Integrated Cyclic Modulation Coherence (ICMC) and Indicator of Second-Order Cyclostationarity (ICS2x) - have been calculated in order to condense the information given by the cyclostationary analysis and to help the analyst in detecting the fault in a fast fault diagnosis procedure. These indicators are applied on actual signals captured on a test rig where a degreased bearing running under radial load developed accelerated wear. The results indicated that all the three cyclostationary indicators are able to detect both the appearance of a localized fault and its development in a distributed fault, whilst the usual approach fails as the fault grows. Copyright © 2013 by ASME.

2013 - Condition monitoring of marine couplings by means of vibration analysis techniques [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

This paper shows the application of some processing techniques for the vibration analysis in working conditions of two different types of marine flexible couplings for boat propulsion. The flexible couplings are mounted between the flywheel of the marine diesel engine and the propeller shaft. The vibration signals are processed in time and frequency domain. Moreover, due to the presence of impulses in the signals, Continuous (CWT) and Discrete Wavelet Transform (DWT) are applied and compared with the conventional time and frequency domain methods. In this work the wavelet analysis is used for the impulse component extraction and the choice of different wavelet functions for this purpose is evaluated. The experimental comparison between two different types of couplings is also given. The results suggest that the wavelet transform techniques are effective to indicate which type of coupling provides a good vibrational behaviour especially in working condition when the angular speed of the propeller shaft is often inverted. Copyright © 2013 by ASME.

2013 - Incoming stall identification in axial compressors by vibration analysis [Relazione in Atti di Convegno]
D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

This work addresses on a complete vibro-acoustic characterization of an axial compressor with the aim to foresee the rotor instability. The tests were performed on a turboshaft Allison 250-C18. The compressor is composed of six axial stages and one centrifugal stage. Four vibration signals were simultaneously measured by means of accelerometers, while the acoustic signals were measured by means of two microphones. Two different kinds of tests have been carried out on the compressor that operates at constant speed: in the course of the first test the six signals were acquired at different positions of the throttle opening, whereas during the second test, the signals were acquired while the throttle was gradually opened. The test results show a sensitive increase of the sub-synchronous activity in the accelerometers spectrum map, moreover, closing the throttle, the amplitude of the spectrum components increases. These phenomena can be related to the rotating stall behavior

2013 - ON THE WEAR AND LUBRICATION REGIME IN VARIABLE DISPLACEMENT VANE PUMPS [Articolo su rivista]
Mucchi, Emiliano; Agazzi, Alessandro; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

This paper proposes an experimental methodology for the analysis of the lubrication regime and wear that occur between vanes and pressure ring in variable displacement vane pumps. The knowledge of the lubrication regime is essential for the improvement of the performance of high pressure vane pumps by reducing wear, increasing the volumetric efficiency and decreasing maintenance costs. Tests using pressure rings of different materials were carried out in order to identify the best material in terms of wear and friction. The proposed methodology is based on Archard’s law and takes advantage of wear experimental measurements, an empirical model for the estimation of contact pressure forces and hardness standard tests. The results of the analysis state that low wear and reduced friction can be obtained if elasto-hydrodynamic lubrication between vanes and pressure ring is established. Results have been also verified by an analytical elasto-hydrodynamic model.

2013 - On the time synchronous average in planetary gearboxes [Relazione in Atti di Convegno]
D'Elia, Gianluca; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

Generally, in planetary gearbox diagnostics, transducers are placed on the gearbox case near the ring gear. The relative angular position of the planet gears with respect to the transducer is a pivotal information for the evaluation of vibration signals related to planet/sun gears. This angular position is usually unknown, or it is known with a large tolerance. The present work seeks to propose two alternative methods for the identification of the angular position of the planet gears with respect to the transducer. The first one is based on the study of how the power flows inside the Time Synchronous average of the ring gear, whilst the second method is based on a modified statistical parameter such as the Crest Factor. The effectiveness of these methods is assessed on the basis of actual vibration signals acquired from a faulty planetary gearbox.

2012 - Assessment of the lubrication regime in variable displacement vane pumps [Relazione in Atti di Convegno]
Mucchi, Emiliano; Agazzi, Alessandro; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

This paper proposes a combined numerical-experimental methodology for the analysis of the lubrication regime and wear that occur between vanes and pressure ring in variable displacement vane pumps. The knowledge of the lubrication regime is essential for the improvement of the performance of high pressure vane pumps by reducing wear, increasing the volumetric efficiency and decreasing maintenance costs. Tests using pressure rings of different materials were carried out in order to identify the best material in terms of wear and friction. The proposed methodology is based on Archard’s law and takes advantage of wear experimental measurements, an empirical model for the estimation of contact pressure forces and hardness standard tests. The results of the analysis state that low wear and reduced friction can be obtained if elasto-hydrodynamic lubrication between vanes and pressure ring is established. Results have been also verified by analytical elasto-hydrodynamic models.

2012 - On the Use of Fourier-Bessel Series Expansion for Gear Diagnostics [Relazione in Atti di Convegno]
D'Elia, Gianluca; Delvecchio, Simone; Dalpiaz, Giorgio
abstract

This work seeks to study the potential effectiveness of Fourier-Bessel (FB) series expansion for gear fault diagnostics. FB series expansion is a method for cross-terms suppression in Wigner-Ville distribution (WVD). In particular, FB series expansion is used as a signal decomposition technique in order to subdivide the signal into its components before WVD evaluation. The pros and cons of this method are highlighted by the analysis of experimental results. In particular two case studies are taken into account: a fatigue crack at the tooth root and spalls of different sizes. The presented results highlight the conditions in which FB decomposition technique is effective in WVD cross-term suppression, the limitations, as well as the advantages in terms of fault identification.

2012 - Simulation of the running in process in external gear pumps and experimental verification [Articolo su rivista]
Mucchi, Emiliano; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

Before marketing external gear pumps are subjected to a running in process to increase their efficiency. However, this is one of the most time-consuming tasks of the entire manufacturing process. Therefore, a mathematical model for optimizing the running in process can be a useful tool for time-to-market reduction. In particular, in this paper a model for the analysis of the dynamic behaviour of external gear pumps, developed by the authors in previous works, is modified and used for simulating the running in process. The modified model is presented and validated via experimental data. A good correlation between simulation and test results guarantees the effectiveness of the model in determining the amount and the distribution of the removed material during the running in process. A meaningful reduction (16%) of the global running in time has been achieved with the introduction of a modified running in process drawn from simulation results.

2011 - Combining blind separation and cyclostationary techniques for monitoring distributed wear in gearbox rolling bearings [Relazione in Atti di Convegno]
G., D' Elia; S., Delvecchio; Cocconcelli, Marco; G., Dalpiaz
abstract

This work seeks to study the potential effectiveness of the Blind Signal Extraction as a pre-processing tool for the detection of distributed faults in rolling bearings. In literature, most of the authors focus their attention on the detection if incipient localized defects. In that case classical techniques (i.e. envelope analysis) are robust in recognizing the presence of the fault and its characteristic frequency. However, when the fault grows, the usual approach fails, due to the change of the fault signature. De facto, in this case the signal does not contain impulses at the fault characteristic frequency, but more complex components with strong non-stationary contents. Moreover, signals acquired from complex machines often contain contributions from several different components as well as noise; thus the fault signature can be hidden in the complex system vibration. Therefore, pre-processing tools are needed in order to extract the bearing signature, from the raw system vibration. In this paper authors focalize their attention on the application of Blind Signal Extraction (BSE) in order to extract the bearing signature from the raw vibration of a gearbox. The effectiveness and sensitivity of BSE is here exploited on the basis of both simulated and real signals. Firstly a simulated signal including the effect of gear meshing as well as a localized fault in bearings is introduced in order to tune the parameters of the BSE algorithm. Next, real vibration signals acquired from a gearbox where tow degreased bearing developed accelerated wear are analysed. In particular, the BSE is compared with the usual pre-processing technique for the analysis of cyclostationary signals, i.e. the extraction of the residual signal. The fault detection is carried out by the computation of the Integrated Cyclic Modulation Spectrum (ICMS) on the extracted signals. The results indicate that the extracted signals via BSE clearly highlight the distributed fault signature, in particular both the appearance of the faults as well as their development are detected, whilst noise still hides fault grow in the residual signals

2010 - A novel approach for the cyclo-non-stationary analysis of speed varying signals [Relazione in Atti di Convegno]
D'Elia, Gianluca; Z., Daher; J., Antoni
abstract

2010 - Advanced signal processing tools for the vibratory surveillance of assembly faults in diesel engine cold tests [Articolo su rivista]
Delvecchio, Simone; D'Elia, Gianluca; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

This paper addresses the use of several signal processing tools for monitoring and diagnosis of assembly faults in diesel engines through the cold test technology. One specific fault is considered here as an example: connecting rod with incorrectly tightened screws. Firstly, the experimental apparatus concerning the vibration tests is introduced. Subsequently, the dynamic analysis of the engine has been carried out in order to calculate the connecting rod forces against the crankpin for predicting the position where mechanical impacts are expected. Then, a vibration signal model for this type of faults is introduced. It deals with the cyclostationary model in which the signal is subdivided into two main parts: deterministic and non-deterministic. Finally, the acceleration signals acquired from the engine block during a cold test cycle at the end of the assembly line are analyzed. For quality control purposes in order to obtain reliable thresholds for the pass/fail decision, a method based on the image correlation of Symmetrized Dot Patterns (SDP) is proposed. This method visualizes vibration signals in a diagrammatic representation in order to quickly detect the faulty engines in cold tests. Moreover the fault identification is discussed on the basis of the cyclostationary model of the signals. The first-order cyclostationarity is exploited by the analysis of the Time Synchronous Average (TSA). In addition the residual signal is evaluated by subtracting the TSA from the raw synchronized signal, and thus the second-order cyclostationarity analysis is developed by means of the Wigner-Ville Distribution (WVD), Wigner-Ville Spectrum (WVS) and Mean Instantaneous Power (MIP). Moreover, Continuous Wavelet Transform (CWT) is presented and compared with the WVD and WVS.

2010 - CONDITION MONITORING BY MEANS OF VIBRATION ANALYSIS TECHNIQUES: SOME CASE STUDIES [Relazione in Atti di Convegno]
Cavallari, Marco; D'Elia, Gianluca; Delvecchio, Simone; Malago', Marco; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

This paper evaluates the effectiveness of some vibration processing techniques for quality control at the end of the assembly line in two industrial cases: the detection of contamination faults in polyurethane wheels, and tooth fault detection in helical gears. These applications illustrate the capability of vibration analysis as condition monitoring tool, as well as the importance of the proper selection of test and processing parameters.

2010 - Detection of Generalized Roughness on Ball Bearing by Cyclostationarity Technique [Relazione in Atti di Convegno]
G., D'Elia; Cocconcelli, Marco; Rubini, Riccardo
abstract

2010 - Diagnostics of distributed faults in ball bearings by means of vibration cyclostationary indicators [Relazione in Atti di Convegno]
D'Elia, Gianluca; Delvecchio, Simone; M., Cocconcelli; Dalpiaz, Giorgio
abstract

2010 - On the monitoring and diagnosis of assembly faults in diesel engine cold tests: a case study [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Mucchi, Emiliano; DI GREGORIO, Raffaele
abstract

tools as a means for the monitoring and the diagnosis of assembly faults in internal combustion (i.c) engines through the cold test technology. Firstly, an approach based on the use of symmetrized dot patterns for the visual characterization of vibration signatures is proposed. This method is applied in order to obtain reliable thresholds for the pass/fail decision after the cold test. Secondly, the fault identification is discussed on the basis of the cyclostationary modeling of the signals. First of all, first-order cyclostationarity is exploited through the analysis of the Time Synchronous Average (TSA). Subsequently, second-order cyclostationarity is developed by means of the mean instantaneous power, Wigner-Ville Distribution (WVD) and Wigner-Ville Spectrum (WVS). Finally, the Continuous Wavelet Transform (CWT) is presented and compared with the Wigner Ville Distribution. In order to show the effectiveness and the limitations of the above-mentioned techniques, tests were carried out for a number of different faults. In this paper the results relative to a specific fault are shown as example.

2009 - On the use of vibration signal analysis for industrial quality control [Relazione in Atti di Convegno]
Cavallari, Marco; D'Elia, Gianluca; Delvecchio, Simone; Malago', Marco; Mucchi, Emiliano; Dalpiaz, Giorgio
abstract

2008 - Application of advanced vibration signal processing techniques in i.c. engine cold tests [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

2008 - COMPARING WIGNER-VILLE DISTRIBUTION AND WAVELET TRANSFORM FOR THE VIBRATION DIAGNOSIS OF ASSEMBLY FAULTS IN DIESEL ENGINES [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Dalpiaz, Giorgio
abstract

2008 - Fault detection in rotating machines by vibration signal processing techniques [Altro]
D'Elia, Gianluca
abstract

2008 - Gear spall detection by non-stationary vibration signal analysis [Relazione in Atti di Convegno]
D'Elia, Gianluca; Delvecchio, Simone; Dalpiaz, Giorgio
abstract

2008 - Use of the cyclostationary modelling for the diagnosis of assembly faults in i.c. engine cold tests [Relazione in Atti di Convegno]
Delvecchio, Simone; D'Elia, Gianluca; Cavallari, Marco; Dalpiaz, Giorgio
abstract

2007 - Design of a Test Bench for the Vibro-Acoustical Analysis and Diagnostics of Rotating Machines [Relazione in Atti di Convegno]
Dalpiaz, Giorgio; D'Elia, Gianluca; Delvecchio, Simone
abstract

2006 - Comparison of analytical and experimental SEA models with commercial software [Altro]
D'Elia, G; N, S FERGUSON; P, Gardonio
abstract

2006 - Modeling run in process in external gear pumps [Relazione in Atti di Convegno]
Dalpiaz, Giorgio; D'Elia, Gianluca; Mucchi, Emiliano; A., FERNANDEZ DEL RINCON
abstract

2006 - Pressure phenomena in dynamic analysis of external gear pumps [Relazione in Atti di Convegno]
Dalpiaz, Giorgio; Mucchi, Emiliano; D'Elia, Gianluca; A., FERNANDEZ DEL RINCON
abstract

2006 - Vibro-acoustic measurements for the identification of incoming stall in axial compressors [Relazione in Atti di Convegno]
Dalpiaz, Giorgio; D'Elia, Gianluca; Mucchi, Emiliano; A., Rivola
abstract

Università degli studi di Modena e Reggio Emilia

Pubblicazioni