The modelling of electrical current NDT methods and its application to weld testing

Discussion of the numerical modeling of NDT methods based on the potential drop and the disruption of power lines to describe the nature, importance and application of modeling. La 1ère partie est consacrée aux applications aux contrôles par courants de Foucault. The first part is devoted to applications for inspection by eddy currents.

The modelling of electrical current NDT methods and its application to weld testing

Control by voltage drop DC. Contrôle par chute de potentiel de courant alternatif. Control by voltage drop AC.

Hitsauksen reaaliaikaisen NDT-tarkastuksen nykytilanne

Tämän kandidaatintyön tarkoituksena on selvittää hitsien tarkastukseen käytettyjen NDT-menetelmien nykytilannetta. Työssä kerrotaan mitä reaaliaikainen NDT-tarkastus on ja mitä menetelmiä siihen voidaan käyttää. Työn tarkoituksena on antaa lukijalle kokonaiskuva NDT-tarkastuksen nykytilasta ja siinä käytettävistä menetelmistä. Tutkimus suoritettiin kirjallisuuskatsauksena. Kirjallisuuskatsaus on luonteeltaan toteava. Lähteiden etsintä suoritettiin suurimmalta osin Internet-hakuna. NDT-tarkastusmenetelmät voidaan jakaa kahteen pääkategoriaan; pinta- ja volumetrisiin menetelmiin. Kaikki tarkastusmenetelmät eivät sovellu reaaliaikaiseen tarkastukseen. Hitsien tarkastuksessa käytetyimmät reaaliaikaiset menetelmät ovat: ultraäänitarkastus, radiografinen tarkastus, optinen spektroskopia, termografia ja pyörrevirtatarkastus. Kaikilla reaaliaikaisilla menetelmillä on omat vahvuutensa ja heikkoutensa. Työssä esitetään myös CASE-esimerkkejä reaaliaikaisesta hitsien tarkastamisesta.Tärkeimpinä johtopäätöksinä voidaan nähdä se, että hitsien NDT-tarkastuksen onnistuminen on aina hyvin tapauskohtaista ja riippuu useista muuttujista. Tästä syystä tällä hetkellä NDT-tarkastusmenetelmistä ei voi valita parasta kaikkiin käyttökohteisiin sopivaa menetelmää. Monessa prosessissa NDT-tarkastustehokkuutta ei määritä mekaanisen laitteiston mittaustarkkuus, vaan tulosten analysointiin käytettyjen algoritmien tehottomuus. Tutkimuksessa esitetään myös idea hybridi-NDT-tarkastusjärjestelmästä, jolla saataisiin havaittua tehokkaasti sekä pinta-että volumetrisia virheitä.

Controlo postural em adolescentes com défice cognitivo

Introdução: O controlo postural é base do movimento humano, e pode ser estudado através das tarefas como o levantar e o alcance. Nestas, observam-se frequentemente alterações neuromotoras em indivíduos com défice cognitivo. Objetivo: descrever as alterações na relação entre os segmentos corporais na sequência de movimento levantar-para-alcançar, em adolescentes com défice cognitivo, face à aplicação de um programa de intervenção em fisioterapia baseado no Conceito de Bobath/ Tratamento do Neurodesenvolvimento (TND). Métodos: antes e após a intervenção em fisioterapia, filmou-se as vistas lateral e posterior da sequência de movimento de levantar-para-alcançar, a qual foi posteriormente dividida em 5 fases, para a análise observacional e quantitativa. A análise quantitativa foi realizada através da distância entre tragus-acrómio, crista ilíaca-acrómio, espinha ilíaca postero-superior homolateral-T1, ângulos inferiores da omoplata e ângulo inferior da omoplata homolateral-T1, recorrendo-se ao software de Avaliação Postural - SAPo. Face à avaliação inicial e evolução dos participantes foram estabelecidos planos de intervenção, tendo em conta aspectos como o contexto, a tarefa e a motivação. Resultados: no geral, foram detetadas alterações na relação entre os segmentos corporais na análise observacional e quantitativa, após a intervenção. Conclusão: As alterações na relação entre os segmentos corporais poderão indicar uma possível reorganização motora.

Comportamento da tibiotársica na sequência de movimento de sentar para de pé em crianças prematuras

Introdução: A prematuridade constitui um fator de risco para a ocorrência de lesões ao nível do sistema nervoso central, sendo que uma idade gestacional inferior a 36 semanas potencia esse mesmo risco, nomeadamente para a paralisia cerebral (PC) do tipo diplegia espástica. A sequência de movimento de sentado para de pé (SPP), sendo uma das aprendizagens motoras que exige um controlo postural (CP) ao nível da tibiotársica, parece ser uma tarefa funcional frequentemente comprometida em crianças prematuras com e sem PC. Objetivo(s): Descrever o comportamento dos músculos da tibiotársica, tibial anterior (TA) e solear (SOL), no que diz respeito ao timing de ativação, magnitude e co-ativação muscular durante a fase I e início da fase II na sequência de movimento de SPP realizada por cinco crianças prematuras com PC do tipo diplegia espástica e cinco crianças prematuras sem diagnóstico de alteração neuromotoras, sendo as primeiras sujeitas a um programa de intervenção baseado nos princípios do conceito de Bobath – Tratamento do Neurodesenvolvimento (TND). Métodos: Foram avaliadas 10 crianças prematuras, cinco com PC e cinco sem diagnóstico de alterações neuromotoras, tendo-se recorrido à eletromiografia de superfície para registar parâmetros musculares, nomeadamente timings, magnitudes e valores de co-ativação dos músculos TA e SOL, associados à fase I e inico da fase II da sequência de movimento de SPP. Procedeu-se ao registo de imagem de modo a facilitar a avaliação dos componentes de movimento associados a esta tarefa. Estes procedimentos foram realizados num único momento, no caso das crianças sem diagnóstico de alterações neuromotoras e em dois momentos, antes e após a aplicação de um programa de intervenção segundo o Conceito de Bobath – TND no caso das crianças com PC. A estas foi ainda aplicado o Teste da Medida das Funções Motoras (TMFM–88) e a Classificação Internacional da Funcionalidade Incapacidade e Saúde – crianças e jovens (CIF-CJ). Resultados: Através da eletromiografia constatou-se que ambos os grupos apresentaram timings de ativação afastados da janela temporal considerada como ajustes posturais antecipatórios (APAs), níveis elevados de co-ativação, em alguns casos com inversão na ordem de recrutamento muscular o que foi possível modificar nas crianças com PC após o período de intervenção. Nestas, verificou-se ainda que, a sequência de movimento de SPP foi realizada com menor número de compensações e com melhor relação entre estruturas proximais e distais compatível com o aumento do score final do TMFM-88 e modificação positiva nos itens de atividade e participação da CIF-CJ. Conclusão: As crianças prematuras com e sem PC apresentaram alterações no CP da tibiotársica e níveis elevados de co-ativação muscular. Após o período de intervenção as crianças com PC apresentaram modificações positivas no timing e co-ativação muscular, com impacto funcional evidenciado no aumento do score final da TMFM-88 e modificações positivas na CIF-CJ.

Evaluation of Maturity and Pulse Velocity Measurements for PCC Traffic Opening Decisions, HR-380, 1998

Concrete paving is often at a disadvantage in terms of pavement type selection due to the time of curing required prior to opening the pavement to traffic. The State of Iowa has been able to reduce traffic delay constraints through material selection and construction methods to date. Methods for monitoring concrete strength gain and quality have not changed since the first concrete pavements were constructed in Iowa. In 1995, Lee County and the Iowa DOT cooperated in a research project, HR-380, to construct a 7.1 mile (11. 43 km) project to evaluate the use of maturity and pulse velocity nondestructive testing (NDT) methods in the estimation of concrete strength gain. The research identified the pros and cons of each method and suggested an instructional memorandum to utilize maturity measurements to meet traffic delay demands. Maturity was used to reduce the traffic delay opening time from 5-7 days to less than 2 days through the implementation of maturity measurements and special traffic control measures. Recommendations on the development of the maturity curve for each project and the location and monitoring of the maturity thermocouples are included. Examples of equipment that could easily be used by project personnel to estimate the concrete strength using the maturity methods is described.

Kompressoriyksiköiden mekaaninen kunnonhallinta

Kunnossapidon kuluista suurimman osan aiheuttavat koneiden ennakoimattomat rikkoutumiset ja niiden tuomat tuotannonpysäytykset. Kunnossapidon suunnitelmallisuutta ja vikojen ennustettavuutta pyritään parantamaan erilaisin kunnonvalvonnallisin keinoin. Havaitsemalla alkava vikaantuminen ajoissa ja seuraamalla sen kehittymistä luodaan mahdollisuus korjaustoimenpiteiden ja -ajankohdan hallittuun suunnitteluun ja tätä kautta kustannussäästöihin. Tässä työssä on tutkittu kompressoriyksiköiden (kaasuturbiini ja keskipakokompressori) ja niiden apulaitteiden kunnossapidon menetelmiä, niiden hyödynnettävyyttä sekä mahdollisuuksia kehittää mekaanista kunnonhallintaa. Työssä päädyttiin johtopäätökseen, että käytettävien menetelmien hyödynnettävyydessä on kehitettävää. Kunnonvalvonnan ohjeistuksia tarkennettiin vastaamaan tämän päivän tavoitteita. Todettiin myös, että värähtelynvalvontaan perustuva kunnonvalvontajärjestelmä soveltuu hyvin kompressoriyksiköiden kunnonvalvonnan järjestelmäksi. Värähtelynvalvontaan perustuva kunnonvalvontajärjestelmä luo mahdollisuuden turvallisen käyttöajan ennustamiseen. Kunnonvalvonnan kehittämisen ja käyttövarmuuden parantamisen kannalta jatkotutkimuksen tekeminen kompressoriyksiköiden mekaanistenlaitteiden turvallisen käyttöajan ennustamiseksi on perusteltua.

Nondestructive evaluation of concrete compression strength by means of Artificial Neural Network (ANN)

The evaluation of structural performance of existing concrete buildings, built according to standards and materials quite different to those available today, requires procedures and methods able to cover lack of data about mechanical material properties and reinforcement detailing. To this end detailed inspections and test on materials are required. As a consequence tests on drilled cores are required; on the other end, it is stated that non-destructive testing (NDT) cannot be used as the only mean to get structural information, but can be used in conjunction with destructive testing (DT) by a representative correlation between DT and NDT. The aim of this study is to verify the accuracy of some formulas of correlation available in literature between measured parameters, i.e. rebound index, ultrasonic pulse velocity and compressive strength (SonReb Method). To this end a relevant number of DT and NDT tests has been performed on many school buildings located in Cesena (Italy). The above relationships have been assessed on site correlating NDT results to strength of core drilled in adjacent locations. Nevertheless, concrete compressive strength assessed by means of NDT methods and evaluated with correlation formulas has the advantage of being able to be implemented and used for future applications in a much more simple way than other methods, even if its accuracy is strictly limited to the analysis of concretes having the same characteristics as those used for their calibration. This limitation warranted a search for a different evaluation method for the non-destructive parameters obtained on site. To this aim, the methodology of neural identification of compressive strength is presented. Artificial Neural Network (ANN) suitable for the specific analysis were chosen taking into account the development presented in the literature in this field. The networks were trained and tested in order to detect a more reliable strength identification methodology.

Optimization of wireless power transfer via magnetic resonance in different media

A wide range of non-destructive testing (NDT) methods for the monitoring the health of concrete structure has been studied for several years. The recent rapid evolution of wireless sensor network (WSN) technologies has resulted in the development of sensing elements that can be embedded in concrete, to monitor the health of infrastructure, collect and report valuable related data. The monitoring system can potentially decrease the high installation time and reduce maintenance cost associated with wired monitoring systems. The monitoring sensors need to operate for a long period of time, but sensors batteries have a finite life span. Hence, novel wireless powering methods must be devised. The optimization of wireless power transfer via Strongly Coupled Magnetic Resonance (SCMR) to sensors embedded in concrete is studied here. First, we analytically derive the optimal geometric parameters for transmission of power in the air. This specifically leads to the identification of the local and global optimization parameters and conditions, it was validated through electromagnetic simulations. Second, the optimum conditions were employed in the model for propagation of energy through plain and reinforced concrete at different humidity conditions, and frequencies with extended Debye's model. This analysis leads to the conclusion that SCMR can be used to efficiently power sensors in plain and reinforced concrete at different humidity levels and depth, also validated through electromagnetic simulations. The optimization of wireless power transmission via SMCR to Wearable and Implantable Medical Device (WIMD) are also explored. The optimum conditions from the analytics were used in the model for propagation of energy through different human tissues. This analysis shows that SCMR can be used to efficiently transfer power to sensors in human tissue without overheating through electromagnetic simulations, as excessive power might result in overheating of the tissue. Standard SCMR is sensitive to misalignment; both 2-loops and 3-loops SCMR with misalignment-insensitive performances are presented. The power transfer efficiencies above 50% was achieved over the complete misalignment range of 0°-90° and dramatically better than typical SCMR with efficiencies less than 10% in extreme misalignment topologies.

Optimization of Wireless Power Transfer via Magnetic Resonance in Different Media

A wide range of non-destructive testing (NDT) methods for the monitoring the health of concrete structure has been studied for several years. The recent rapid evolution of wireless sensor network (WSN) technologies has resulted in the development of sensing elements that can be embedded in concrete, to monitor the health of infrastructure, collect and report valuable related data. The monitoring system can potentially decrease the high installation time and reduce maintenance cost associated with wired monitoring systems. The monitoring sensors need to operate for a long period of time, but sensors batteries have a finite life span. Hence, novel wireless powering methods must be devised. The optimization of wireless power transfer via Strongly Coupled Magnetic Resonance (SCMR) to sensors embedded in concrete is studied here. First, we analytically derive the optimal geometric parameters for transmission of power in the air. This specifically leads to the identification of the local and global optimization parameters and conditions, it was validated through electromagnetic simulations. Second, the optimum conditions were employed in the model for propagation of energy through plain and reinforced concrete at different humidity conditions, and frequencies with extended Debye's model. This analysis leads to the conclusion that SCMR can be used to efficiently power sensors in plain and reinforced concrete at different humidity levels and depth, also validated through electromagnetic simulations. The optimization of wireless power transmission via SMCR to Wearable and Implantable Medical Device (WIMD) are also explored. The optimum conditions from the analytics were used in the model for propagation of energy through different human tissues. This analysis shows that SCMR can be used to efficiently transfer power to sensors in human tissue without overheating through electromagnetic simulations, as excessive power might result in overheating of the tissue. Standard SCMR is sensitive to misalignment; both 2-loops and 3-loops SCMR with misalignment-insensitive performances are presented. The power transfer efficiencies above 50% was achieved over the complete misalignment range of 0°-90° and dramatically better than typical SCMR with efficiencies less than 10% in extreme misalignment topologies.

Vibrational methods applied to NDT testing and fluid density measurement

A system for the NDI' testing of the integrity of conposite materials and of adhesive bonds has been developed to meet industrial requirements. The vibration techniques used were found to be applicable to the development of fluid measuring transducers. The vibrational spectra of thin rectangular bars were used for the NDT work. A machined cut in a bar had a significant effect on the spectrum but a genuine crack gave an unambiguous response at high amplitudes. This was the generation of fretting crack noise at frequencies far above that of the drive. A specially designed vibrational decrement meter which, in effect, measures mechanical energy loss enabled a numerical classification of material adhesion to be obtained. This was used to study bars which had been flame or plasma sprayed with a variety of materials. It has become a useful tool in optimising coating methods. A direct industrial application was to classify piston rings of high performance I.C. engines. Each consists of a cast iron ring with a channel into which molybdenum, a good bearing surface, is sprayed. The NDT classification agreed quite well with the destructive test normally used. The techniques and equipment used for the NOT work were applied to the development of the tuning fork transducers investigated by Hassan into commercial density and viscosity devices. Using narrowly spaced, large area tines a thin lamina of fluid is trapped between them. It stores a large fraction of the vibrational energy which, acting as an inertia load reduces the frequency. Magnetostrictive and piezoelectric effects together or in combination enable the fork to be operated through a flange. This allows it to be used in pipeline or 'dipstick' applications. Using a different tine geometry the viscosity loading can be predoninant. This as well as the signal decrement of the density transducer makes a practical viscometer.

Plasma nitriding of AA2011 alloy and surface characterization by NDT techniques

Al-Cu alloys are widely used in the aerospace and automotive industries due to their high specific strength in some tempered conditions. However, due to poor corrosion and wear resistance, they are often anodized and/or painted. Plasma nitriding has been proposed as an alternative, though the developments in this technique are still in a recent stage for Al alloys. Electrical characterization techniques are well implemented NDTs in the industry because of good accuracy associated with lower cost, compared to other methods. Some, like eddy currents and 4-point probe techniques, are often used in coating inspection. The objective of this study was to perform Al nitriding at low temperatures to minimize the tempering initial condition damage and to assess the feasibility of eddy currents technique as a method for evaluating surface properties. The work developed can be divided in two stages. The first one was the process tuning, done at the Shibaura Institute of Technology, in Tokyo; and the second was the electrical characterization done in Faculdade de Ciências e Tecnologia, UNL. Low temperature nitriding of AA2011 alloy specimens was successfully achieved. Electrical conductivity results show that lift-off measurements by eddy currents testing can be related to surface properties.

A bayesian approach for NDT data fusion: The Saint Torcato Church case study

This paper presents a methodology based on the Bayesian data fusion techniques applied to non-destructive and destructive tests for the structural assessment of historical constructions. The aim of the methodology is to reduce the uncertainties of the parameter estimation. The Young's modulus of granite stones was chosen as an example for the present paper. The methodology considers several levels of uncertainty since the parameters of interest are considered random variables with random moments. A new concept of Trust Factor was introduced to affect the uncertainty related to each test results, translated by their standard deviation, depending on the higher or lower reliability of each test to predict a certain parameter.

Hierarchical modelling of timber reference properties using probabilistic methods: Maximum Likelihood Method, Bayesian Methods and Probability Networks

In recent decades, an increased interest has been evidenced in the research on multi-scale hierarchical modelling in the field of mechanics, and also in the field of wood products and timber engineering. One of the main motivations for hierar-chical modelling is to understand how properties, composition and structure at lower scale levels may influence and be used to predict the material properties on a macroscopic and structural engineering scale. This chapter presents the applicability of statistic and probabilistic methods, such as the Maximum Likelihood method and Bayesian methods, in the representation of timber’s mechanical properties and its inference accounting to prior information obtained in different importance scales. These methods allow to analyse distinct timber’s reference properties, such as density, bending stiffness and strength, and hierarchically consider information obtained through different non, semi or destructive tests. The basis and fundaments of the methods are described and also recommendations and limitations are discussed. The methods may be used in several contexts, however require an expert’s knowledge to assess the correct statistic fitting and define the correlation arrangement between properties.

Review of theoretical models of electromagnetic NDT and their applications

There is an increasing interest in modelling electromagnetic methods of NDT - particularly eddy currents. A collaboration within the International Institute of Welding led to a survey intended to explain to non mathematicians the present scope of modelling. The present review commences with this survey and then points out some of the developments and some of the outstanding problems in transferring modelling into industry.