Spot welding of 1.4307 material of 1+1 mm thickness is tuned out excellently by the enterprise ROSTEX – at the changes only of the welding current it was managed to approach the value of thickness achieved by enterprise ROSTEX. At the welding of 1.4307 material of 2+2 mm thickness it was managed to achieve more strength under welding parameters: Fs = 5500N, Is = 8,964 kA, ts = 10 Per. Spot welding of 1.0330 material revealed a possibility in proceeding with welding current increasing which could stand for the weld strength increasing (not necessarily) – a limit where material could splash was not achieved. The soft mode welding is not convenient for up-to date spot welding because the material is extremely affected by heat at the long welding time, it also leads to huge thermal losses, thermal effect and distortion of electrodes (electrodes life diminishing). Soft mode welding is not expedient even economically. In accordance with economic comparison, see chart 27, page 64 – for instance welding of 1.4307 material with 1+1 mm thickness at 1000 welds there is difference of 644 Czech crowns between the hard and the soft mode welding in benefit to the hard mode.

Capacitor discharge welding is an efficient, cost-effective and stable process. It is mostly used for projection welding. Real-time monitoring is desired to ensure quality. Until this point, measured process quantities were evaluated through expert systems. This method takes much time for developing, is strongly restricted to specific welding tasks and needs deep understanding of the process. Another possibility is quality prediction based on process data with machine learning. This method can overcome the downsides of expert systems. But it requires classified welding experiments to achieve a high prediction probability. In industrial manufacturing, it is rarely possible to generate big sets of this type of data. Therefore, semi-supervised learning will be investigated to enable model development on small data sets. Supervised learning is used to develop machine learning models on large amounts of data. These models are used as a comparison to the semi-supervised models. The time signals of the process parameters are evaluated in these investigations. A total of 389 classified weld tests were performed. With semi-supervised learning methods, the amount of training data necessary was reduced to 31 classified data sets.

Les alliages à mémoire de forme Nickel Titane sont des matériaux aux propriétés remarquablesdues à une transformation martensitique réversible et sont largement utiliséspar l’industrie biomédicale et dans des dispositifs de type actionneurs. La première partiede cette étude porte sur une analyse de leur comportement thermomécanique basée surla réalisation de mesures de champs cinématiques (par corrélation d’images visibles) etthermiques (par caméra infrarouge). Une part importante du travail présenté concernel’amélioration des calculs de sources de chaleur à partir des champs de température. Pource faire, les capacités et conductivités thermiques des phases austénitique et martensitiqueont été estimées par différentes méthodes expérimentales. Ensuite, la méthode de calcul desource a été validée sur des données virtuelles obtenues numériquement et sur des donnéesexpérimentales obtenues lors d’une transformation martensitique induite par un refroidissementnaturel. Cette première partie se conclut par l’application des développements àdes mesures réalisées lors d’un essai de cisaillement. La seconde partie est une contributionà la réalisation de matériaux architecturés constitués d’empilement de tubes de NiTi liésentre eux ; notre étude concerne la réalisation et la caractérisation de liaisons de tubes deNiTi par soudage résistif. / NiTi shape memory alloys have amazing properties due to a reversible martensitictransformation and are widely used by biomedical industries and as actuators. The firstpart of this study deals is a thermomechanical analysis of the material, based on kinematical(with digital image correlation) and thermal (with infrared camera) field measurements.An important part of this work deals with the improvement of the heat sources estimationfrom thermal fields. For this, thermal heat capacities and conductivities of austeniteand martensite were estimated with several experimental methods. Then, the heat sourceestimation method was validated from virtual data obtained numerically and from experimentaldata obtained during a martensitic transformation induced by natural cooling.This first part is concluded with the use of this technique to study shear tests. The secondpart of this study is a contribution to the realization of architectured materials composedof linked stacked tubes. Our study deals with the realization and the characterization ofthe NiTi link, realized by resistance welding.

Submitted by ISABELA ATILIO null (isabelaatilio@hotmail.com) on 2017-10-31T16:58:11Z No. of bitstreams: 1 Dissertação Final - Isabela Atilio.pdf: 12968588 bytes, checksum: 24d1b58efcf37a8ffc0d9ed1afc4d7d4 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-11-10T19:48:34Z (GMT) No. of bitstreams: 1 atilio_i_me_guara.pdf: 12968588 bytes, checksum: 24d1b58efcf37a8ffc0d9ed1afc4d7d4 (MD5) / Made available in DSpace on 2017-11-10T19:48:34Z (GMT). No. of bitstreams: 1 atilio_i_me_guara.pdf: 12968588 bytes, checksum: 24d1b58efcf37a8ffc0d9ed1afc4d7d4 (MD5) Previous issue date: 2017-09-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O aumento da demanda por petróleo e seus derivados tem instigado o desenvolvimento de materiais para dutos com elevadas tenacidade à fratura e resistência mecânica, como os aços de alta resistência e baixa liga (ARBL) pertencentes às classes API. Aliada à utilização destes aços, a aplicação do processo de soldagem por resistência elétrica de alta frequência (HF/ERW) tem conquistado maior interesse no setor. Entretanto, defeitos nas juntas soldadas constituem uma das principais causas de falhas em dutos, principalmente quando associados às condições externas de operação, o que tem sido motivo para estudos relacionados à integridade estrutural destes tubos. O objetivo deste trabalho foi estudar a tenacidade à fratura de um tubo de aço API 5L X70 soldado pelo processo HF/ERW, a partir de dados obtidos com ensaios CTOD de espécimes de flexão por três pontos, tipo SE(B) “gull wing”. A metodologia proposta envolveu ensaios de CTOD a variadas temperaturas, incluindo a região de transição dúctil-frágil, a fim de avaliar a integridade estrutural do material em condições críticas de operação. Os ensaios foram realizados com base nas normas ASTM E1820 e BS7448, e consistiram na utilização de corpos de prova retirados diretamente da parede do tubo, com posterior planificação. De forma geral, as amostras de material base apresentaram uma boa tenacidade à fratura em todas as temperaturas de ensaio, o que não aconteceu com as amostras de material de solda, que apresentaram baixa tenacidade. Os resultados de tenacidade obtidos mostraram que a metodologia empregada para o estudo da integridade estrutural por meio de ensaios CTOD com amostras extraídas diretamente da parede do tubo, com posterior planificação, mostrou-se adequada. Embora as normas ASTM E1820 e BS7448 adotem diferentes parâmetros para a determinação do valor de CTOD, observou-se que os valores de CTOD foram bem próximos. / The increasing demand for oil and its products has driven the development of materials for ducts with high fracture toughness and high mechanical strength, such as high strength low alloy (HSLA) steels, appertaining to the API classes. In addition to the use of these steels, the application of the high frequency resistance welding process (HF/ERW) has gained greater interest in the sector. However, defects in the welded joints are one of the most causes of failures in pipelines, especially when they are associated with external operating conditions, which has been the reason for studies related to the structural integrity of these tubes. The aim of this work was to study the fracture toughness of an API 5L X70 steel tube welded by the HF/ERW process, from data obtained with CTOD tests bending specimens by three points, type SE (B) gull wing. The proposed methodology involved CTOD tests at various temperatures, including the ductile-brittle transition region, in order to assess the structural integrity of the material under critical operating conditions. The tests were performed based on the ASTM E1820 and BS7448 standards, and consisted of the use of specimens taken directly from the wall of the tube, with subsequent planning. In general, the base material samples showed good fracture toughness at all test temperatures, which did not occur with the samples of welded material, which presented low toughness. The toughness results obtained showed that the methodology used for the study of structural integrity by means of the CTOD tests with samples drawn directly from the wall of the tube, with subsequent planning, was adequate. Although the ASTM E1820 and BS7448 standards adopt different parameters for the determination of the CTOD value, it was observed that the CTOD values were very close.

In an effort to increase the fuel efficiency of cars more widespread use of higher strength steels is seen for their high strength-to-weight ratio. Thesesteels are more limited in their formability and tendency to harden than conventional steels, complicating manufacturing. This thesis summarizes the available research on resistance projection nut welding to higher strength steels and investigates the accuracy of the simulation program SORPAS when simulating projection nut welds to AlSi-coated Boron steel. It was found that the greatest difficulties in welding coated ultra high strength steels were the metallurgical effects of both the high alloying content of the steel and the coatings interacting with the weld when melting. Although SORPAS was an intuitive program to use for resistance welding and had a wide library of materials available, it was not found to be able to predict the resistance characteristics or results of projection nut welds to coated Boron steel without significant changes to default material parameters. The biggest issue was the delaying effect the coating layer had on the peak resistance, something not observed experimentally. Better results are suggested to be possible after experimentally ensuring the properties of the materials used and importing those values into SORPAS. / I ett försök att öka bilars bränsleeffektivitet används i allt större utsträckning stål med högre hållfasthet på grund av deras goda förhållande mellan styrka och vikt. Dessa stål är mer begränsade i sin formbarhet och tendens att härda än konventionella stål, vilket försvårar tillverkning. Denna uppsats sammanfattar den tillgängliga forskningen om motståndssvetsning med projektionsmutter i höghållfasta stål och undersöker noggrannheten hos simuleringsprogrammet SORPAS vid simulering av projektionsmuttersvetsar i AlSi-belagt borstål. Det konstaterades att de största svårigheterna vid svetsning av belagda ultrahöghållfasta stål var de metallurgiska effekterna av både stålets höga legeringsinnehåll och beläggningarnas interaktion med svetsen vid smältning. Trots att SORPAS var ett intuitivt program att använda för motståndssvetsning och hade ett brett bibliotek av tillgängliga material kunde det inte förutsäga motståndsegenskaperna eller resultaten av projektionsmuttersvetsar mot belagt borstål utan betydande förändringar av standardmaterialparametrarna. Det största problemet var den fördröjande effekt som beläggningsskiktet hade på maximala resistansen, något som inte observerades experimentellt. Bättre överenstämmelse föreslås vara möjlig efter att experimentellt säkerställa egenskaperna hos de material som används och importera dessa värden till SORPAS.

This Diploma thesis deals with assessment of the influence of two fundamental types of resistance welders operation on chosen power quality parameters at the point of common coupling (PCC) of the power network. The assessed parameters of power quality are the total harmonic distortion of the supply voltage, asymmetry of the supply voltage and the level of short term flicker at the point of common coupling. The assessment is based on the comparison of the results of computer simulations done in PSCad 4.2.0 with the requirements of technical standards. The outcome of this thesis is the determination of allowable limits for physical and operation parameters for the general arrangement of a power distribution network and a resistance welder that should guarantee the power quality compliance.