Friction, Vibration and Dynamic Properties of Transmission System under Wear Progression

This reprint focuses on wear and fatigue analysis, the dynamic properties of coating surfaces in transmission systems, and non-destructive condition monitoring for the health management of transmission systems. Transmission systems play a vital role in various types of industrial structure, including wind turbines, vehicles, mining and material-handling equipment, offshore vessels, and aircrafts. Surface wear is an inevitable phenomenon during the service life of transmission systems (such as on gearboxes, bearings, and shafts), and wear propagation can reduce the durability of the contact coating surface. As a result, the performance of the transmission system can degrade significantly, which can cause sudden shutdown of the whole system and lead to unexpected economic loss and accidents. Therefore, to ensure adequate health management of the transmission system, it is necessary to investigate the friction, vibration, and dynamic properties of its contact coating surface and monitor its operating conditions

A neural network approach for chatter prediction in turning

[EN] Machining processes, including turning, are a critical capability for discrete part production. One limitation to high material removal rates and reduced cost in these processes is chatter, or unstable spindle speed-chip width combinations that exhibit self-excited vibration. In this paper, an artificial neural network (ANN) is applied to model turning stability. The analytical stability limit is used to generate a data set that trains the ANN. It is observed that the number and distribution of training points influences the ability of the ANN model to capture the smaller, more closely spaced lobes that occur at lower spindle speeds. Overall, the ANN is successful (>90% accuracy) at predicting the stability behavior after appropriate training.The authors gratefully acknowledge financial support from the UNC ROI program. Elena Perez-Bernabeu and Miguel Selles also acknowledge support from Universitat Politenica de Valencia (PAID-00-17). Additionally, some of the neural net figures and the 10-fold cross validation figures are based on the TikZ codes provided on StackExchange-TeX by various users. Harish Cherukuri would like to thank them for their valuable advice.Cherukuri, H.; Pérez Bernabeu, E.; Sellés, M.; Schmitz, TL. (2019). A neural network approach for chatter prediction in turning. Procedia Manufacturing. 34:885-892. https://doi.org/10.1016/j.promfg.2019.06.1598858923

Multi-categories tool wear classification in micro-milling

Ph.DDOCTOR OF PHILOSOPH

Noise eliminated ensemble empirical mode decomposition scalogram analysis for rotating machinery fault diagnosis

Rotating machinery is one type of major industrial component that suffers from various faults and damage due to the constant workload to which it is subjected. Therefore, a fast and reliable fault diagnosis method is essential for machine condition monitoring. Artificial intelligence can be applied in fault feature extraction and classification. It is crucial to use an effective feature extraction method to obtain most of the fault information and a robust classifier to classify those features. In this study, an improved method, noise-eliminated ensemble empirical mode decomposition (NEEEMD), was proposed to reduce the white noise in the intrinsic functions and retain the optimum ensembles. A convolution neural network (CNN) classifier was applied for classification because of its feature-learning ability. A generalised CNN architecture was proposed to reduce the model training time. The classifier input used was 64×64 pixel RGB scalogram samples. However, CNN requires a large amount of training data to achieve high accuracy and robustness. Deep convolution generative adversarial network (DCGAN) was applied for data augmentation during the training phase. To evaluate the effectiveness of the proposed feature extraction method, scalograms from the related feature extraction methods such as ensemble empirical mode decomposition (EEMD), complementary EEMD (CEEMD) and continuous wavelet transform (CWT) were also classified. The effectiveness of the scalograms was also validated by comparing the classifier performance using greyscale samples from the raw vibration signals. The ability of CNN was compared with two traditional machine learning algorithms, k nearest neighbour (kNN) and the support vector machine (SVM), using statistical features from EEMD, CEEMD and NEEEMD. The proposed method was validated using bearing and blade datasets. The results show that the machine learning algorithms achieved comparatively lower accuracy than the proposed CNN model. All the outputs from the bearing and blade fault classifiers demonstrated that the scalogram samples from the proposed NEEEMD method obtained the highest accuracy, sensitivity and robustness using CNN. DCGAN was applied with the proposed NEEEMD scalograms to enhance the CNN classifier’s performance further and identify the optimal amount of training data. After training the classifier using the augmented samples, the results showed that the classifier obtained even higher validation and test accuracy with greater robustness. The test accuracies improved from 98%, 96.31% and 92.25% to 99.6%, 98.29% and 93.59%, respectively, for the different classifier models using NEEEMD. The proposed method can be used as a more generalised and robust method for rotating machinery fault diagnosis

Pattern recognition of micro and macro grinding phenomenon with a generic strategy to machine process monitoring

Abstract In modern manufacturing environments waste is an issue of great importance. Specifically the research in this thesis looks at issues in establishing the initial steps to gain a generic process monitoring system that ensures that grinding is both optimised but not the determent where costly malfunctions mean the scrapping and re-melting of expensive quality intensive materials. The research conducted in this thesis investigates the process of cutting, ploughing and rubbing during single grit scratch tests. These investigations meant the correlation between physical material removal phenomenon and the emitted material dislocations gained from acoustic emission extraction. The initial work looked at different aerospace materials and the distinction of cutting, ploughing and rubbing during single grit radial scratch tests. This initial work provided novel results not seen in this area before and paved the way for more robust results in investigating the same phenomena during horizontal single grit scratch tests. This work provided more robust classification of cutting, ploughing and rubbing and transferred directly to grinding pass cuts from 1um and 0.1mm depth cuts respectively. In using robust classifiers such as the Neural Network and novel classifiers such as non-linear data paradigms, Fuzzy-c clustering with Genetic Algorithm optimisation, cutting, ploughing and rubbing phenomenon was investigated. These investigations showed that more cutting occurs when there is moreinteraction between grit and workpiece based on the increase depth of cut. Other thesis results investigated a generic classifier using Genetic Programming to classify multiple anomaly phenomena. This work can be bridged together with the unit event grit classification work

Pattern recognition of micro and macro grinding phenomenon with a generic strategy to machine process monitoring

Abstract In modern manufacturing environments waste is an issue of great importance. Specifically the research in this thesis looks at issues in establishing the initial steps to gain a generic process monitoring system that ensures that grinding is both optimised but not the determent where costly malfunctions mean the scrapping and re-melting of expensive quality intensive materials. The research conducted in this thesis investigates the process of cutting, ploughing and rubbing during single grit scratch tests. These investigations meant the correlation between physical material removal phenomenon and the emitted material dislocations gained from acoustic emission extraction. The initial work looked at different aerospace materials and the distinction of cutting, ploughing and rubbing during single grit radial scratch tests. This initial work provided novel results not seen in this area before and paved the way for more robust results in investigating the same phenomena during horizontal single grit scratch tests. This work provided more robust classification of cutting, ploughing and rubbing and transferred directly to grinding pass cuts from 1um and 0.1mm depth cuts respectively. In using robust classifiers such as the Neural Network and novel classifiers such as non-linear data paradigms, Fuzzy-c clustering with Genetic Algorithm optimisation, cutting, ploughing and rubbing phenomenon was investigated. These investigations showed that more cutting occurs when there is moreinteraction between grit and workpiece based on the increase depth of cut. Other thesis results investigated a generic classifier using Genetic Programming to classify multiple anomaly phenomena. This work can be bridged together with the unit event grit classification work

ON THE STABILITY OF VARIABLE HELIX MILLING TOOLS

One of the main aims of the manufacturing industry has been to maximise the material removal rate of machining processes. However, this goal can be restricted by the appearance of regenerative chatter vibrations. In milling, one approach for regenerative chatter suppression is the implementation of variable-helix cutters. However, these tools can lead to isolated unstable regions in the stability diagram. Currently, variable-helix unstable islands have not been extensively researched in the literature. Therefore, the current thesis focuses on studying and experimentally validating these islands. For the validation, an experimental setup that scaled not only the structural dynamics but also the cutting force coefficients was proposed. Therefore, it was possible to attain larger axial depths of cut while assuming linear dynamics. The variable-helix process stability was modelled using the semi-discretization method and the multi-frequency approach. It was found that the variable helix tools can further stabilise a larger width of cut due to the distributed time delays that are a product of the tool geometry. Subsequently, a numerical study about the impact of structural damping on the variable-helix stability diagram revealed a strong relationship between the damping level and instability islands. The findings were validated by performing trials on the experimental setup, modified with constrained layer damping to recreate the simulated conditions. Additionally, a convergence analysis using the semi-discretization method (SDM) and the multi-frequency approach (MFA) revealed that these islands are sensitive to model convergence aspects. The analysis shows that the MFA provided converged solutions with a steep convergence rate, while the SDM struggled to converge. In this work, it is demonstrated that variable-helix instability islands only emerge at relatively high levels of structural damping and that they are particularly susceptible to model convergence effects. Meanwhile, the model predictions are compared to and validated against detailed experimental data that uses a specially designed configuration to minimise experimental error. To the authors' knowledge, this provides the first experimentally validated study of unstable islands in variable helix milling, while also demonstrating the importance of accurate damping estimates and convergence studies within the stability predictions

Apprentissage profond multimodal appliqué à l'usinage

Les techniques axées sur les données ont offert à la technologie de fabrication intelligente des opportunités sans précédent pour assurer la transition vers une productivité basée sur l'industrie 4.0. L'apprentissage automatique et l'apprentissage profond occupent une place cruciale dans le développement de systèmes intelligents pour l'analyse descriptive, diagnostique et prédictive des machines-outils et la surveillance d’état des systèmes de fabrication industrielle. De nombreuses techniques d'apprentissage profond ont été testées sur les problèmes de surveillance d’état des machines-outils, de la détection du broutement, du diagnostic de défauts, de la sélection optimale des paramètres de coupe, etc. Une étude bibliométrique est proposée pour à retracer les techniques de détection du broutement, depuis les méthodes de traitement du signal temps-fréquence, la décomposition jusqu'à la combinaison avec des modèles d'apprentissage automatique ou d'apprentissage profond. Une analyse cartographique a été réalisée afin d’identifier les limites de ces différentes techniques et de proposer des axes de recherche pour détecter le broutement dans les processus d'usinage. Les données ont été collectées à partir du web of science (WoS 2022) en exploitant des requêtes particulières sur la détection du broutement. La plupart des documents recueillis présentent la détection du broutement à l'aide de techniques de transformation ou de décomposition. Ce travail a permis de détecter les articles les plus significatifs, les auteurs les plus cités, la collaboration entre auteurs, les pays, continents et revues les plus productifs, le partenariat entre pays, les mots-clés des auteurs et les tendances de la recherche sur la détection du broutement. Cette thèse à pour objective de proposer dans un premier temps, une méthode de prédiction du choix des paramètres de coupe en exploitant l’apprentissage profond multimodal. L'apprentissage profond multimodal a été utilisé pour associer un choix de conditions de coupe (outil, vitesse de coupe, profondeur de coupe et vitesse d'avance par dents) avec un état de surface, en considérant la rugosité arithmétique moyenne (Ra) et une photo de la pièce. Nous avons construit un modèle de fusion multimodale tardive avec deux réseaux de neurones profonds, un réseau de neurones convolutif (CNN) pour traiter les données images et un réseau de neurones récurrent avec des couches de mémoire à long terme (LSTM) pour les données numériques. Cette méthode permet d’intégrer les informations provenant de deux modalités (fusion multimodale) afin à terme d'assurer la qualité de surface dans les processus d'usinage. Les difficultés rencontrées lors de l’élaboration de cette méthode nous ont orientés vers une approche unimodale pour détecter le broutement d’usinage. Par la suite nous présentons une approche basée sur des compétences mécaniques pour d’abord identifier les traitements optimaux des signaux puis l'apprentissage profond (apprentissage par transfert) pour détecter automatiquement le phénomène de broutement en usinage. Ce travail a mis l’accent sur l’utilisation de données collectées dans les conditions industrielles contrairement à la majorité des travaux basés sur les données qui utilisent les données laboratoire. Cette méthode arrive à avoir de bonnes performances malgré le fait qu’elle ne donne aucune indication au réseau de neurones sur l'amplitude du signal, la vitesse de rotation

Reports on industrial information technology. Vol. 12

The 12th volume of Reports on Industrial Information Technology presents some selected results of research achieved at the Institute of Industrial Information Technology during the last two years.These results have contributed to many cooperative projects with partners from academia and industry and cover current research interests including signal and image processing, pattern recognition, distributed systems, powerline communications, automotive applications, and robotics

Condition monitoring of tools in CNC turning

The metal cutting industry today is highly automated and, as a step towards Europe's ability to compete on the world market, an increased level of automation can be expected in the future. Therefore, much attention has been paid to the use of automated monitoring systems within the maintenance strategies designed to prevent breakdown. This research focuses on the condition monitoring of cutting tools in CNC turning, using airborne acoustic emission, (AAE). A structured approach for overcoming the problems associated with changing cutting parameters is presented with good results. A reverse and novel approach in estimating gradual tool wear in longitudinal roughing has been made by predicting cutting parameters directly from the acoustics emitted from the process. Using the RMS as a representation of the energy in the signal, where the spectral distributions are working as divisional operators, it has been possible to accurately extract a representation of feed rate, depth of cut and cutting speed from the signal. Using a simplified relationship to estimate tangential cutting force, a virtual force can be calculated and related to a certain amount of flank wear using non-linear regression. Furthermore, this research presents a monitoring solution where disturbances are eliminated by recognising the sound signatures where it, afterwards, is possible to evaluate the reliability of the wear decision. This is done by describing irregularities in the signal , where surface parameters used on a sound waveform, combined in a neural network, has been used to trigger outputs for several defined classes of disturbances. An investigation of the two wear types flank and crater wear, has been conducted and is has been concluded, that although crater wear has an effect on the AAE, it is difficult to recognise this. AAE has shown to an efficient tool to detect flank wear, where a direct relationship is shown between the changes in the cutting parameters, tool wear and AAE. This approach has resulted in a precise monitoring so lution, where flank wear can be estimated within an error of I0%.EThOS - Electronic Theses Online ServiceGBUnited Kingdo