1,721,003 research outputs found
Measurement of the perimeter of curved elements by laser sensor triangulations
No full textIn this work a new system for the cross-sectional perimeter measurement of curved elements has been studied and built. An example is shown of an application to the measurement, in the production line, of the pipe perimeter employed by the automotive industry to realize the exhaust head.
Digital simulation models enabled an evaluation of the uncertainty of measurement which arise depending on the algorithms of the calculus adopted and the experimental configuration of the sensors.
A comparative analysis of the results enable an optimal choice of the mathematical model to analize the data and to establish experimental configuration of the used sensors.
Subsequently, the measurement chain was set up and a software for the analysis of the experimental data developed. Some measurements were carried to define the principal non desired input and the causes of uncertainty.
The analysis with patterns of known geometry enabled a characterization of the complete system and a comparison of the values of the uncertainties with those obtained from the computer simulations
Evaluation of the dynamic pressure between tyre and ground using PVDF piezoelectric films
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Thermoelastic Stress Analysis of the Contact Between a Flat Plate and a Cylinder
No full textIn the frame of intercomparison testing among different optical full-field measurement techniques, the crucial aspect concerning contact problems between bodies has been extensively analyzed through thermoelasticity. This technique has allowed us to obtain stress patterns in terms of the first stress invariant by measuring temperature fluctuation on the surface of a cyclically loaded mechanical component. For the present study, a special-purpose test bench was assembled to be used within a round robin test, so as to properly load the sample. The test case taken into account is the very well-known contact problem between a cylinder and a flat plate. The results obtained from thermoelasticity through the use of a zoom lens, were compared to classical Hertz theory prediction and FEA models
Measurement of contact pressure distributions between surfaces by thermoelasticic stress analisys
No full textThe development of new techniques for the measurement of contact pressure distributions between bodies in contact is of large interest in mechanics, for the design and verify of many couplings between mechanical components. Examples are the contact between tooth of gears, between the balls and rings of ball bearings, between the wheel and rail etc.
In this paper a new measurement technique is proposed, based on the measurement principle known as thermoelasticity. The particular case about the measurement of contact pressure distribution between a ball and a flat plate is discussed. Previous studies was performed in order to examine the contact surface between the two bodies realizing one of the two bodies in contact using an infrared transparent material, with appropriate values of the other mechanical properties. These studies were anyway only qualitative. In the present work, two calibration methodologies are proposed to obtain measures of contact surface stress between a ball and a flat. One of these methodologies is based on experimental test and the other one is based also on analytic results. The measured stress behaviours are in agreement with the classic Hertz theory; relative uncertainty is smaller than 0.1. This allows to obtain first quantitative results of contact pressure distribution by using thermoelasticit
Characterization of professional knifes by thermoelasticity. R. Marsili, G. L. Rossi, Ingegneria Alimentare International
No full textIn this work the mechanical behaviour of the blade, has been studied using thermoelastic analysis. This measurement technique permit to correlate the thermal variation, induced by a cyclic load,
with the stresses distribution on the knife blade. The image of superficial stresses acquired by thermoelastic system (Deltatherm 1550) has been compared with FEM analysis results directly
The Thermoelastic techniques for the measurement of stresses distribution on component of structures or machines
No full textDesign of an optical measurement system for dynamic testing of electrospindles
No full textDynamic characterization of electrospindles is necessary to ensure long life, reliability and high-tech performance required in many industrial applications. Many diagnostic approaches have been developed with regard to fault detection and dynamic characterization of rotating machinery.
Here, an optimized set-up of a measurement system based on electro-optical sensors is proposed for performing vibration tests on electrospindle rotors. A complete, dynamic characterization of the rotor is obtained through modelling and accurate measurements of shaft vibrations are performed to trace vibration modes of the rotor. The proposed measurement set-up can be used to support the design optimization of electrospindles in order to increase quality standards
Development of a new capacitive matrix for a steering wheel's pressure distribution measurement
No full textPressure distribution measurements are becoming increasingly important in the automotive field for ergonomic optimization of components like seats or steering wheel. Nowadays, traditional sensors shows several drawbacks such as response variation in time, low sensitivity and high level of intrusiveness. Moreover the great difficulty of carrying out dynamical analysis in the area of interest highly limits their use. A new type of matrix, now available, promises to overcome such problems, and it has been widely tested in the automotive field. The matrix is based on a series of condensers which vary the capacity depending on the pressure applied on their surface. The high sensitivity and the chance of monitoring pressure distribution with frequency contents up to 200 Hz make this tool particularly suitable for evaluating steering wheel’s goodness effectiveness in an on-road test. Relevance to industry: The knowledge of the behavior of capacitive sensor matrix for pressure distribution at the operator’s hand-car stirling wheel interface may benefit automobile designers and manufacturers to evaluate steering wheel goodness and seat effectiveness perform through on-road tests and to evaluate the efficiency of the power steering mechanism
Misure di deformazione superficiale: analisi comparative tra metodologie basate sul principio termoelastico e sulla correlazione digitale di immagini
No full textLa correlazione digitale di immagini (di seguito DIC: acronimo di Digital Image Correlation) è una tecnica per la misurazione del campo di deformazione basata sull’analisi di immagini acquisite in istanti successivi, durante l’applicazione di un carico. A fronte della semplicità e della rapidità di esecuzione delle misurazioni, i risultati sono fortemente influenzati sia dalla qualità delle immagini acquisite, sia dagli algoritmi di calcolo impiegati per la loro elaborazione.
Le considerazioni condotte sono riferite ad un tipico “test case” costituito da un sottile provino di sezione rettangolare realizzato in AISI 304 sul quale è praticato un foro centrale, soggetto ad una semplice sollecitazione mono assiale di trazione. Il foro ha lo scopo di generare un campo non uniforme di deformazioni, come spesso si verifica nelle situazioni di comune interesse. Normalmente, per validare i risultati ottenuti con la DIC, si utilizzano degli estensimetri. Nel caso specifico il loro impiego risulta difficoltoso a causa degli elevati gradienti di deformazioni nel volume di misura.
I risultati ottenuti sono quindi confrontati con quelli ricavati mediante la tecnica di analisi termoelastica (di seguito TSA: Thermoelastic Stress Analysis). Questa tecnica è infatti idonea alla misura del primo invariante della deformazione superficiale, valore questo direttamente confrontabile con uno degli output disponibili dai più comuni software commerciali per DIC. I risultati delle misurazioni condotte con le due metodologie, su uno stesso provino, nelle medesime condizioni di prova, sono elaborati numericamente al fine di valutare ed evidenziare la sovrapponibilità degli stessi
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