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Identification of abnormal tribological regimes using a microphone and semi-supervised machine-learning algorithm

Friction 2022年第4期10卷 583-596页

作者： Vigneashwara PANDIYAN josef prost Georg VORLAUFER Markus VARGA Kilian WASMER Laboratory for Advanced Materials Processing(LAMP) Swiss Federal Laboratories for Materials Science and Technology(Empa)Thun CH-3602Switzerland AC2T research GmbH Viktor-Kaplan-Straße 2/CWiener Neustadt 2700Austria

Functional surfaces in relative contact and motion are prone to wear and tear,resulting in loss of efficiency and performance of the workpieces/*** occurs in the form of adhesion,abrasion,scuffing,galling,and scoring between ***,the rate of the wear phenomenon depends primarily on the physical properties and the surrounding *** the integrity of surfaces by offline inspections leads to significant wasted machine time.A potential alternate option to offline inspection currently practiced in industries is the analysis of sensors signatures capable of capturing the wear state and correlating it with the wear phenomenon,followed by in situ classification using a state-of-the-art machine learning(ML)*** this technique is better than offline inspection,it possesses inherent disadvantages for training the ML ***,supervised training of ML models requires the datasets considered for the classification to be of equal weightage to avoid *** collection of such a dataset is very cumbersome and expensive in practice,as in real industrial applications,the malfunction period is minimal compared to normal ***,classification models would not classify new wear phenomena from the normal regime if they are *** a promising alternative,in this work,we propose a methodology able to differentiate the abnormal regimes,i.e.,wear phenomenon regimes,from the normal *** is carried out by familiarizing the ML algorithms only with the distribution of the acoustic emission(AE)signals captured using a microphone related to the normal *** a result,the ML algorithms would be able to detect whether some overlaps exist with the learnt distributions when a new,unseen signal *** achieve this goal,a generative convolutional neural network(CNN)architecture based on variational auto encoder(VAE)is built and *** the validation procedure of the proposed CNN architectures,we were

关键词： surface integrity acoustic emission auto encoders condition monitoring wear prediction

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Comprehensive review of tribometer dynamics-Cycle-based data analysis and visualization

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Friction 2022年第5期10卷 772-786页

作者： josef prost Guido BOIDI Thomas LEBERSORGER Markus VARGA Georg VORLAUFER AC2Tresearch GmbH Wiener Neustadt 2700Austria

Tribologists often rely on triboexperiments to investigate factors that affect a *** inherent dynamic behavior of the respective tribometer setups and its effect on data interpretation remain often *** this study,a comprehensive analysis of sensor data obtained from lubricated and dry triboexperiments is *** are generated on a pin-on-disc test rig with a silicon nitride ball on a steel disc contact with a rotation frequency of~3 ***-speed acquisition of sensor data up to 5 kHz is performed to resolve changes in the data within individual *** characteristic frequencies of the system and their temporal evolution are determined via time--frequency analysis,which reveals periodic patterns in the sensor ***-based data evaluation allows the detection of localized events and changes during an operation and considerably reduces the apparent measurement uncertainty,as compared with an unreduced *** data analysis and visualization routines presented herein may serve as a prototype for further application to tribometer setups.

关键词： high-speed data acquisition time-frequency analysis(TFA) cycle-resolved analysis pin-on-disc tribometer

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Longs short-term based semi-supervised memory encoder-decoder for early prediction of failures in self-lubricating bearings

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Friction 2023年第1期11卷 109-124页

作者： Vigneashwara PANDIYAN Mehdi AKEDDAR josef prost Georg VORLAUFER Markus VARGA Kilian WASMER Laboratory for Advanced Materials Processing(LAMP) Swiss Federal Laboratories for Materials Science and Technology(Empa)Thun CH-3602Switzerland AC2T research GmbH Wiener Neustadt 2700Austria

The existing knowledge regarding the interfacial forces,lubrication,and wear of bearings in real-world operation has significantly improved their designs over time,allowing for prolonged service *** a result,self-lubricating bearings have become a viable alternative to traditional bearing designs in industrial ***,wear mechanisms are still inevitable and occur progressively in self-lubricating bearings,as characterized by the loss of the lubrication film and ***,monitoring the stages of the wear states in these components will help to impart the necessary countermeasures to reduce the machine maintenance *** article proposes a methodology for using a long short-term memory(LSTM)-based encoder-decoder architecture on interfacial force signatures to detect abnormal regimes,aiming to provide early predictions of failure in self-lubricating sliding contacts even before they *** sliding experiments were performed using a self-lubricating bronze bushing and steel shaft journal in a custom-built transversally oscillating tribometer *** force signatures corresponding to each cycle of the reciprocating sliding motion in the normal regime were used as inputs to train the encoder-decoder architecture,so as to reconstruct any new signal of the normal regime with the minimum *** this semi-supervised training exercise,the force signatures corresponding to the abnormal regime could be differentiated from the normal regime,as their reconstruction errors would be very *** the validation procedure for the proposed LSTM-based encoder-decoder model,the model predicted the force signals corresponding to the normal and abnormal regimes with an accuracy of 97%.In addition,a visualization of the reconstruction error across the entire force signature showed noticeable patterns in the reconstruction error when temporally decoded before the actual critical failure point,making it possible to be used for early predic

关键词： predictive maintenance in-situ sensing long short-term memory(LSTM) encoder-decoder wear monitoring tribology

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Spatially Resolved Photoelectric Performance of Axial GaAs Nanowire pn-Diodes

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Nano Research 2011年第10期4卷 987-995页

作者： Andrey Lysov Sasa Vinaji Matthias Offer Christoph Gutsche Ingo Regolin Wolfgang Mertin Martin Geller Werner prost Gerd Bacher Franz-josef Tegude Center for Nanointegration Duisburg-Essen University of Duisburg-Essen 47048 Duisburg Germany

The spatially resolved photoelectric response of a single axial GaAs nanowire pn-diode has been investigated with scanning photocurrent and Kelvin probe force microscopy. Optical generation of carriers at the pn-junction has been shown to dominate the photoresponse. A photocurrent of 88 pA, an open circuit voltage of 0.56 V and a fill factor of 69% were obtained under AM 1.5 G conditions. The photocurrent followed the increasing photoexcitation with 0.24 A/W up to an illumination density of at least 90 W/cm2, which is important for potential applications in concentrator solar cells.

关键词： GaAs nanowire solar cells scanning photocurrent microscopy Kelvin probe force microscopy electroluminescence

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