1,721,063 research outputs found
Experimental Investigation of Shaft Radial Load Effect on Bearing Fault Signatures Detection
Full text linkThis paper investigates the influence of external radial load applied to the shaft on bearing fault detection based on vibration or current in induction motors operating under different conditions. This paper details the results of a laboratory trial comprising different test sets on the condition monitoring and fault diagnostic of a six-poles induction motor using a design of experiment (DOE) approach. The dedicated test setup comprises a custom-made fixture that allows us to dynamically vary the radial load applied to the output shaft. The aim is to investigate the effects of radial load on the fault diagnosis of shaft bearings and the interactions between other operating parameters, such as output torque. Specific scalar parameters have been proposed for the condition monitoring of the test motor from vibration and current data. The correct choice of the significant parameters is proven by the strong dependence on the damage returned by DOE results
Relationship Between Vibration Energy and Wear Condition of Ball Bearings Based on Reye’s Hypothesis
No full textThis paper deals with the study of the correlation between the dynamic behavior of a failed ball bearing and wear defect development. Ball bearings are intensively used in industrial applications as supports for rotating machines, so a failure of those components produces unexpected downtime of the line-production. Most of the literature techniques focus on the early detection of localized faults on bearings (e.g. on the outer ring), but more recently some authors have also worked on distributed faults (e.g. generalized roughness).This paper focuses on distributed faults, in particular on the consequences of a lack of grease in ball bearings. This condition happens when the bearing is not maintained correctly or when it works in hostile conditions (e.g. chemical attack). In such cases there is not a pure rotation of the bearing spheres but friction between races and spheres. As a consequence, the presence of an external load generates friction forces which damage the bearing surfaces and increase the bearing vibration. This paper propose a new approach based on Reye’s hypothesis to assess the wear of the bearing surfaces. According to Reye’s hypothesis the mechanical work of the friction force is proportional to the material volume removed by reason of wear. By means of experimental tests it is possible to evaluate the proportional coefficient and to determine the relationship between the typology and intensity of the vibrations and the failure evolution. The aim of this work is to provide a monitoring methodology able to predict the residual life of the suppor
Mounting of accelerometers with structural adhesives: experimental characterization of the dynamic response
No full textThe use of accelerometers to monitor the vibrations of either complex machinery or simple components involves some considerations about the mounting of the sensor to the structure. Different types of mounting solutions are commonly used, but in all cases they can be classified in one of these categories: stud mounting, screw mounting, adhesive mounting, magnetic mounting, and probe sensing. Indeed, each of them has a specific field of application depending on e.g. the mounting surface conditions, the temperature, the accessibility to the specific mounting point, etc. The choice of the mounting solution has an important effect on the accuracy of the usable frequency response of the accelerometer, since the higher the stiffness of the fixing, the higher the low-pass frequency limit of the mounting. This article specifically focuses on adhesive mounting of accelerometers, which includes a great number of different products from the temporary adhesives like the beeswax to the permanent ones like cyanoacrylate polymers. Among the variety of commercial adhesives, three specific products have been experimentally compared to assess their transmissivity and the results are reported in this article. A two-component methylmethacrylate (HBM X60), a modified silane (Terostat 737), and a cyanoacrylate (Loctite 454) adhesive have been used to join two aluminum bases, one connected to an accelerometer and the other to the head of electromagnetic shaker. A design of experiment (DOE) approach was used to test the system at several levels of amplitude and frequency of the external sinusoidal excitation supplied by the shaker
Overview on condition monitoring for bearings in variable speedconditions: the example of a packaging machine
No full textThis paper proposes a review of some techniques for the diagnostics of ball bearingbased on the experience of the authors on an industrial application. Frequently engineering industrysuggests non-trivial problems and new fields of research for the academy. This is the case of bearingdiagnostics in direct-drive motors, for example. Direct-drive are brushless motors fully controlledby the drive system. Thanks to an encoder or a resolver mounted on the shaft they could performcomplex motion profiles such as polynomial or splines, including reverse rotation of the shaft. Themain advantage of direct-drive motors is the removal of cams or gearboxes afterwards the motorwith a consequent reduction of economic and maintaining costs. Indeed the main drawback is thedifficulty to make diagnostics on their bearings. Regarding the bearing diagnostics, most of theliterature techniques are based on the search of fault-characteristic frequencies in the vibration spectrumof the motor. These fault frequencies are linearly dependent on the rotational frequency of theshaft supposing it is constant. In direct-drive motors the rotational speed changes continuously andconsequently the fault frequencies are meaningless. Diagnostics of machineries in non-stationaryconditions is attractive and promising field and recently different papers have been proposed in literature[1] and thematic conference [2] organized, covering a wide range of applications, e.g. frommanufacturing [3] to mining industry [4]. Focusing on a specific industrial case the authors runthrough their experience on bearing diagnostics for a packaging machine working under variablespeed condition. The developed techniques include an improved version of the order tracking, theuse of correlation function, wavelet analysis and two supervised learning approaches: the artificialneural networks and the support vector machines. Moreover the closing part of the paper covers thebearing diagnostics by mean of the stator current signal analysis of the moto
Support Vector Machines for Condition Monitoring of Bearings in a Varying-Speed Machinery
No full textThis paper deals with the diagnostics of ball bearings in direct-drive motors by means ofSupport Vector Machines (SVM). For the new generation of packaging machines,direct-drive motors have substituted parts of the mechanical transmission chains asgears train or cams between the motor and the load. In fact, a position feed-back is usedby the control system to perform polynomial profiles of motion involving continuouschanges of the shaft speed and a cyclic inversion of its rotating direction.The presenceof complex shaft dynamics provides a vibration signal extremely noisy, where theevents due to malfunctions or damages disappear and are not periodic, so the classicmethodologies for the monitoring of the support conditions based on the signal analysisin the frequency domain are ineffective. In this paper the use of Support VectorMachines overcomes the constant-speed limits and the SVM are proven to be apowerful and reliable tool to diagnose the health of ball bearing even in variable-speedapplications, based on experimental tests conducted on an industrial packaging machin
Future Challenges in Condition Monitoring from an Industrial Perspective: The Case of the Independent Carts Systems
Full text linkIn this paper, the authors discuss about the future challenges of condition monitoring in an industrial context. One of the authors is Line Manager at Data Processing & Analytics for Equipment, Industry 4.0 & MES Products division of Tetra Pak Packaging Solutions S.p.A., a multinational company that approached condition monitoring and diagnostics fifteen years ago. So far, they have gained experience and have a clear idea of what the Industrial field expects in the coming years. In this paper, the analysis of a specific case study is an opportunity to suggest more general research themes on condition monitoring
Correlation Between the Stator Current Signal and the Kinematic Model of the Rolling Bearing for the Diagnostics
No full textEffect of Temperature on the Dynamic Response of Adhesively Mounted Accelerometers
Full text linkThis paper focuses on the effect of temperature on the frequency response function (FRF) of three different structural adhesives; namely a two component methylmethacrylate (HBM X60), a modified silane (Terostat 939) and a cyanoacrylate (Loctite 454). The structural adhesives are commonly used in vibration analysis to mount accelerometers on structures or machines. The stiffness of the adhesive can influence the response function on large frequency band, affecting the proportional excitation between the structure and the accelerometer. In the “system structure + adhesive + accelerometer”, the adhesive may acts like a filter between the source and the sink of vibrations. A variation of the dynamic response of the filter could lead to an erroneous analysis. The authors already investigated the relation between the frequency response function and operating conditions of the test. This paper expands the research by considering the temperature effect in order to depict a complete picture of the adhesive behavior on dynamic response of an accelerometer. A design of experiments (DOE) approach was used to test two bonded aluminum bases at different levels of temperature and frequency of the external sinusoidal excitation, supplied by an electromagnetic shaker. The results clearly demonstrate that the adhesive is not able to change the system response, therefore the signal transmission is good in the entire range of temperature regardless the adhesive chosen
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