Dissertations / Theses on the topic 'Tools for stud welding'

The subject of this diploma thesis is the simulation and digital commissioning of a robotic production system for welding elements such as studs on sheet metal parts. The basis of the work is search of information related to industrial robots, PLC control, tools used for welding, fixtures, manipulators, sensors, safety and protection elements commonly used in such production systems. The second part of the work deals with the given problem and it is a virtual commissioning of the given concept of a robotic production system. This means creating its simulation model in the Process Simulate environment, selecting robots, creating robotic trajectories, collision analysis, creating sensors, signals and optimization. Last part includes the connection of the simulation model with the software S-7PLCSIM Advanced and TIA Portal, the creation of control PLC logic in the form of a program, visualization and verification of their functionality using the above-mentioned connection with the simulation model.

Heat generation during the FTSW process plays and important role in determining the characteristics of the weld. In order to obtain temperature fields, a transient temperature heat analysis is required. An area is the maximum temperatures reached within the base material during the FTSW process. These temperatures will be measured during experimentation, and compared to the welding simulation done using FEA. From the literature search it appeared that no heat transfer analysis had been done using finite element methods.

Thesis (M.S.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 29-31).

Regarding the ground electrical connection in trucks and buses, the requirements of earthing in heavy-duty vehicles were gathered and evaluated. The most important problems in the state-of-the-art grounding devices are corrosion, electrical resistance and uncertainty in the mounting process, altogether with depreciation over time. The goal is to come up with new concepts that can give a more reliable and better ground connection into the frame with faster, easier and safer manufacturing operations. Several methods for attaching different ground connectors to the steel frame are going to be investigated, including bolted connections, press devices, soldering, brazing and local plating spots. It will be shown that the welding operation gives the best electrical results, while lowering mounting costs, time and variability. Two welded connectors are then going to be proposed as the best alternatives and a parallel investigation with both of them is going to be carried out. These new concepts, filed for patent protection, are going to be labelled as “SRM Welded ground stud” and “SRM Welded grounding nut”. The first of them consists of a plated steel threaded stud (M8 or M10) with a ring shaped contact surface built in one of the ends, where the Ø12 mm weld is to be performed onto the uncoated frame. The second concept comprises a stainless steel M10 round nut welded over a punched hole. The optimization will also cover different alternatives for plating metals, contact aid compounds and masking caps for both devices. The risk of mechanical weakening of the frame because of the new welded concepts is going to be tested for the case of the SRM Welded ground stud. The results will show an increase in fatigue resistance of at least 20% compared to the current ground screw. Furthermore, the strength of the welded interface will show higher proof load than the stud itself. The welded nuts, tested with torque loading, will show a sufficient performance as well. The electrical tests present an expected decrease in ground resistance of 40% for the welded stud and an increase of 28% for the welded nuts, compared with the current ground screw. The conclusion of this Master Thesis states the recommendation of the implementation of a new grounding method through the SRM Welded ground stud. Although, some modifications in the transportation process of the frames might be needed because of the new protruding parts, pointing an estimated distance of 20mm from the frame surface.
När det gäller jordad elanslutning i lastbilar och bussar, har kraven på jordning i tunga fordon samlats och utvärderats. De största problemen i de mest avancerade jordade enheterna är korrosion, elektriskt motstånd och osäkerhet i monteringsprocessen, sammantaget med avskrivning över tiden. Målet är att utveckla nya koncept som kan ge en bättre och mer tillförlitlig jordanslutning i ramen med snabbare, enklare och säkrare tillverkning. Flera metoder för att fästa olika mark kontakter till stålramen kommer att undersökas, bland annat skruvförband, pressanordning, lödning, hårdlödning och lokala pläteringsfläckar. Det kommer att visa att svetsning ger den bästa elektriska resultatet, samtidigt som monteringskostnader, tid och variabilitet minskar. Två svetsade kontakter kommer sedan att föreslås som de bästa alternativen och en parallell undersökning med dem båda kommer att genomföras. Dessa nya koncept, för vilka patentskydd har ansökts, kommer att märkas som “SRM Svetsade marktapp” och “SRM Svetsade jordmutter”. Den första av dem består av en pläterad stålgängad tapp med en ringformad kontaktyta byggt i en av ändarna, där svetsen skall utföras på den obelagda ramen. Det andra konceptet består av en rostfri rund mutter svetsad över ett stansat hål. Optimeringen kommer även att omfatta olika alternativ för pläterade metaller, kontaktstöds föreningar och maskeringslock för de båda enheterna. Risken för mekanisk försvagning av ramen på grund av det nya svetsade konceptet kommer att testas med avseende på fallet med SRM Svetsad bottenreglar. Resultaten visar en ökad utmattningshållfasthet på minst 20% jämfört med den nuvarande jordskruven. Dessutom kommer styrkan av den svetsade gränsytan uppvisa en högre provbelastning än tappen själv. De svetsade muttrarna, testade med momentbelastning, kommer också uppvisa en tillräcklig prestanda. De elektriska testerna presenterade en förväntad minskning av markmotståndet på 40% för svetsade tappar och en ökning med 28% för svetsade muttrar, jämfört med den nuvarande jordskruven. Slutsatsen av detta examensarbete anger en rekommendation av genomförandet av en ny jordningsmetod genom en SRM Svetsad marktapp. Trots detta kan vissa ändringar behövas i transportprocessen av ramarna på grund av de nya utskjutande delarna, vilka pekar från ramens yta med ett uppskattat avstånd av 20 mm.

In Laser Materials Processing there has always been a need for suitable methods to supervise and monitor the processes on line, to ensure correct production quality or to trigger alarms when failures are detected. Numerous investigations have been made in this field, including experimental and theoretical work. It is common practice in this field to monitor surface temperature, plasma radiation and back-reflected laser light, coaxially with the laser beam. Traditionally, the monitoring systems involved carry out no statistical analysis of the signals received - they merely involve thresholds. This thesis looks at the feedback collected during laser welding using such a co-axial setup from a Digital Signal Processing point of view and also uses high speed video photography to correlate signal perturbations with process anomalies.Modern Digital Signal Processing techniques such as Kalman filtering, Principal Component Analysis and Cluster Analysis have been applied to the measurement data and have generated new ways to describe the weld behaviour using parameters such as reflected pulse shape. The limitations of commercially available welding supervision systems have been studied and design suggestions for the next generation of on line weld monitoring equipment have been formulated.
Godkänd; 2009; 20091103 (ricols); LICENTIATSEMINARIUM Ämnesområde: Produktionsutveckling/Manufacturing Systems Engineering Examinator: Professor Alexander Kaplan, Luleå tekniska universitet Tid: Onsdag den 16 december 2009 kl 13.00 Plats: E 232, Luleå tekniska universitet

PROBLEM - The bobbin friction stir welding (BFSW) process has potential benefits for welding thin sheet aluminium alloy. The main benefits of friction stir welding over conventional thermal welding processes are minimisation of energy usage, no need for consumables, potential for good weld quality without porosity, no fumes, minimal adverse environmental effects (green), minimal waste (lean), and reduced threats to personal health and safety. The BFSW process has further advantages over conventional friction stir welding (CFSW) in the reduction of welding forces, faster welding, and less fixturing. It is especially attractive to industries that join thin sheet material, e.g. boat-building. The industrial need for this project arose from the desire to apply the technology at a ship manufacturing company, INCAT located in Hobart, Tasmania, Australia. However there are peculiar difficulties with the specific grade of material used in this industry, namely thin sheet aluminium Al6082-T6. Early efforts with a portable friction stir welding machine identified the process to have low repeatability and reproducibility, i.e. process-instability. There are a large number of process variables and situational factors that affect weld quality, and many of these are covert. This is also the reason for divergent recommendations in the literature for process settings. PURPOSE - The main purpose of this research was to identify covert variables and better understand their potentially adverse effects on weld quality. Therefore, this thesis investigated the hidden variables and their interactions. Developing this knowledge is a necessity for making reliable and repeatable welds for industrial application. APPROACH - An explorative approach that focused on the functional perspective was taken. An extensive empirical testing programme was undertaken to identify the variables and their effects. In the process a force platform and BFSW tools were designed and built. A variety of machine platforms were used, namely portable friction stir welding, manual milling machine and computer numerical control (CNC) milling machine. The trials were grouped into 14 test plans. These are tool shoulder gap, spindle and travel speed, tool features, machines, tool fixation, machinery, welding direction, plate size (width and dimension), support insulation, tool materials, substrate properties and fixation. For the welded plates besides visual inspection of the weld, current, force, and temperature were measured. The Fourier transform was used to analyse the frequency response of machines. Also the welded samples were tested to the maritime standards of Det Norske Veritas (DNV). A number of relationships of causality were identified whereby certain variables affected weld quality. A model was developed to represent the proposed causality using the IDEF0 systems engineering method. FINDINGS - From these trials six main variables have been identified. These are tool features, spindle speed, travel speed, shoulder gap compression, machine variability, tool and substrate fixation. A rigid system is required for a consistent weld results. Under this condition, full pin features (threads and flats) need to be used to balance the adverse effects of individual features. It has been shown that fabricated bobbin tools with sharp edges can cause cuts and digging thus this feature should be avoided. Additionally, the substrate should have continuous interaction with the tool so the shoulder interference needs to be fixed and well-controlled. It is found that the compression generated by the shoulder towards the substrate helps material grabbing for better tool-substrate interaction. It is also shown that tool entry causes ejection of material and hence an enduring mass deficit, which manifests as a characteristic tunnel defect. The new explanation of the formation, origin and location of this defect has been explained. Material transportation mechanisms within the weld have been elucidated. It is also found that the role of the travel speed is not only to control heat generation but also for replacing the deficit material. Additionally, heat supplied to the weld depends not only on thickness, but also the width of the plate. Different types of machine cause an interaction in the material flow through their controller strategies. Jerking motion can occur at a slow travel speed, which also alters the way material is being transported. The Fourier transform (FFT) has been used to identify the characteristics of good and bad BFSW welds. This has the potential to be expanded for real-time process control. IMPLICATIONS - Tool deflection and positioning, material flow and availability are identified as affecting weld quality through stated mechanisms. The impact is even more severe when involving thin-plate aluminium. For the industry to successfully adopt this technology the process typically needs tight control of shoulder gap, tool strength and stiffness, feature fabrication, substrate and tool fixation. Additionally spindle and travel speed need to be adjusted not only based on the type of materials and thickness, but also the width, type of machine and method of tool entry. ORIGINALITY - New data are presented, which lead to new insights into the welding mechanics, production settings, material transportation and weld defects for BFSW on thin sheet material. The conventional idea that the welding tool has a semi-steady interaction with the substrate is not supported. Instead the interaction is highly dynamic, and this materially affects the weld-quality, especially in the difficult-to-weld material under examination. Factors such as shoulder gap, tool and substrate fixation compliance and machine types emerge as variables that need to be given attention in the selection of process parameters. The causal relationships have been represented in a conceptual model using an IDEF0 system approach. This study has made several original contributions to the body of knowledge. First is the identification of previously hidden variables that effect weld formation for the fixed gap BFSW process. The second contribution is a new way of understanding the material transportation mechanics within the weld. This includes the flow around the pin in the plane of the weld, the vertical transportation of material up the pin, the formation of turbulent-like knit lines at the advancing side, and the formation of tunnel defects. Also included here is a new understanding of how material deficit arises at tool entry and exit, and from flash/chips, and how this contributes to the tunnel weld defect. In addition, new understandings of the role of feed rate have been identified. Related to the material transportation, the work has also identified the importance of an interference fit between the substrate and tool. A third contribution is the identification of the dynamic interaction between tool and substrate. This identifies the important role rigidity plays. Associated with this is the identification of frequency characteristics of the motors under load. The fourth contribution is identification of the specific process settings for the difficult-to-weld material of AL6082-T6. The fifth contribution is the development of a novel method of fabricating bobbin friction stir welding tools as embodied in a patent application.

With the desire to lighten the frame while keeping or increasing the strength, Advanced High-Strength Steels (AHSS) have been developed for use in the automotive industry. AHSS meet many vehicle functional requirements because of their excellent strength and acceptable ductility. But joining AHSS is a challenge, because weldability is lower than that of mild steels. Friction stir spot welding (FSSW) is a solid state joining process that can provide a solution to the weldability issues in AHSS, but FSSW has not been studied in great detail for this application. In this work, Si3N4 tools were used for FSSW experiments on DP 980 steel with 1.2mm thickness. Joint strength was measured by lap shear tension testing, while thermocouples were used for the temperature measurements. A finite element model was developed in order to predict material flow and temperatures associated with FSSW. Since a 3D model of the process is very time consuming, a novel 2D model was developed for this study. An updated Lagrangian scheme was employed to predict the flow of sheet material, subjected to the boundary conditions of the fixed backing plate and descending rotating tool. Heat generation by friction was computed by including the rotational velocity component from the tool in the thermal boundary conditions. Material flow was calculated from a velocity field while an isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of temperature, strain and strain rate. Shear stress at the tool/sheet interface was computed using the viscoplastic friction law. The model predicted welding temperatures to within 4% of the experiments. The welding loads were significantly over predicted. Comparison with a 3D model of FSSW showed that frictional heating and the proportion of total heat generated by friction were similar. The position of the joint interface was reasonably well predicted compared to experiment.

Friction stir welding (FSW) is a relatively new solid-state welding technology invented at The Welding Institute of UK in 1991. It is versatile and has been widely adopted to join various materials. There has been strong research activity on revealing the details of the material flow pattern in the nugget zone induced by the conventional shoulder tool. However, there is insufficient understanding on the aspects of the scroll shoulder tool design and the shoulder flow zone formation utilizing this type of tool. The major objective of this study was to conduct experiments, analyse results and then reveal the shoulder flow zone forming mechanism for the scroll shoulder tool. The method used was to identify the flow pattern in the shoulder flow zone using a ‘marker insert’ technique, and then to suggest the forming mechanism of the shoulder flow zone based on the obtained flow pattern; although the ‘marker insert’ technique has never been used to study the shoulder flow zone flow pattern induced by the scroll shoulder tool. Experiments were conducted to examine the thick sections 6061 aluminium ‘marker insert’ welds, which were welded using a scroll shoulder tool at a range of welding parameters. These were followed by quantifying the mass of the accumulated work piece material within the scroll groove (pick up material-PUM), evaluating the effect of welding parameters on the shoulder flow zone formation, and documenting the shoulder flow zone flow pattern. The major finding was that there is a simple banded structure which forms in a layer to layer manner in the bottom portion of the shoulder flow zone, but it disappears in the top portion of the shoulder flow zone. Accordingly, the forming mechanism of the shoulder flow zone for the scroll shoulder tool was suggested as follows. Firstly, the tool pin is plunged into the work piece; the work piece material is extruded by the pin and pushed up into the scroll groove forming the PUM. Secondly, after the tool shoulder is plunged into the work piece to a certain depth, the scroll groove is fully filled up with the PUM. Finally, during the forward movement of the tool, the central portion of PUM is driven downward by the root portion of the pin and then detaches from the pin (tip portion) in a layer to layer manner. It has also found that the thickness of the shoulder flow zone varies with a thicker on the advancing side than on the retreating side, and there is a positive linear relationship between the mass of PUM and the weld quality. This study has revealed for the first time the forming mechanism of the shoulder flow zone, and has improved the understanding of the shoulder flow zone formation using a scroll shoulder tool. It is recommended that a ‘shoulder-breaking’ technique is developed to break the rotating shoulder suddenly and hence embed it into the work piece during FSW, in which a real-time shoulder-work piece couple could be produced for a better three-dimensional examination of the shoulder flow zone.

Doktorska disertacija razmatra modelovanje procesa zavarivanja i modelovanje podataka, koji omogućuje elektronski oblik dokumentovanih procedura, zapisa, specifikacija, planova kvaliteta i radnih uputstava. Model integralnog procesa zavarivanja je razvijen da bi se identifikovali svi faktori koji utiču na kvalitet zavarenog spoja, odnosno proizvoda od faze preispitivanja zahteva iz ugovora i tehničkog preispitivanja, podugovaranja, opreme i osoblja, procesa zavarivanja, rukovanja i skladištenja osnovnog i potrošnog materijala, ispitivanja, kontrole, verifikacije, kalibracije, neusaglašenosti, korektivnih mera, identifikacije i sledljivosti.Predloženi model integralnog procesa zavarivanja je prototipski što mu daje originalnost jer je jedinstven. Prototipski pristup omogućuje da se informacioni sistem prilagodi svakom pojedinačnom proizvodnom sistemu, odnosno kompaniji u skladu sa njenim potrebama i zahtevima.
The doctoral dissertation discusses the modeling of welding processes and data modeling, which allows electronic forms of documented procedures, records, specifications, quality plans and work instructions.The model of integrated welding process was developed to identify all the factors that affect the quality of the weld, i.e. the product from the stage of the review required under the contract and technical review, subcontracting, equipment, personnel, processes, welding, handling and storage of basic supplies and materials, testing, control, verification, calibration, non-conformities, corrective actions, identification and traceability.The proposed model of integrated welding process is a prototype which gives originality because it is unique and allows the information system adjusts each production system, and the company in accordance with its needs and requirements

Este trabalho apresenta uma abordagem da ferramenta FMEA, Failure modes and effect analysis, em uma integração com os custos relativos à qualidade, aplicada ao processo de soldagem GMAW, gas metal arc welding. O objetivo principal é evidenciar a importância da utilização desta ferramenta para se prever e prevenir falhas de processo antes que as mesmas ocorram, e minorar os custos da qualidade envolvidos. A proatividade da ferramenta FMEA proporciona, através das ações recomendadas de melhoria, a possibilidade de se mensurar com antecipação os custos relativos à prevenção, avaliação e falhas de qualidade. O método empregado para esta abordagem foi de uma pesquisa-ação, sendo estabelecida uma equipe multidisciplinar para implantação e execução da FMEA e avaliação dos custos da qualidade. Os resultados obtidos na fase anterior à aplicação da FMEA informavam que os custos das falhas apresentavam uma participação de 89,84% dos custos da qualidade; com a utilização da ferramenta, estes foram reduzidos para 3,82% devido ao investimento de melhoria. Objetivando-se equilibrar os custos associados, foi projetada uma estimativa futura de 50% de custo de falhas. Na análise comparativa dos custos da qualidade, foi verificado que os custos de falhas relativos à fase anterior ao FMEA reduziram 86% em relação à projeção futura, e os custos da qualidade reduziram de 74%, evidenciando-se deste modo o benefício da utilização da ferramenta FMEA para a redução de custos operacionais.
This paper presents an approach of the FMEA tool, Failure modes and effect analysis, in integration with the costs of quality, applied to the GMAW welding process, gas metal arc welding. The main objective is to highlight the importance of using this tool to predict and prevent process failures before they occur, and reduce the costs of quality involved. The proactivity of FMEA tool, provides through the recommended actions for improvement, the possibility to measure in advance the costs of prevention, assessment and quality failures. The method employed for this approach was an action research, which established a multidisciplinary team for deployment and implementation of FMEA and evaluation of quality costs. The results obtained in the previous phase to the implementation of FMEA reported that the cost of failure had a 89.84% share of the costs of quality; using the tool, these were reduced to 3.82% due to improved investment. In order to balance the costs, was projected a 50% estimated future cost of failures. In comparative cost analysis we founded that the quality failure costs related to the phase prior to FMEA reduced 86% compared to the projected future, and quality costs were reduced of 74%, demonstrating thereby the benefit of using the FMEA tool to reduce operating costs.

碩士
國立中興大學
材料科學與工程學系所
105
5083-H321 aluminum alloy with advantages of low density, medium strength, and corrosion resistance, is widely used in marine applications such as ships, auto parts, aircraft welding parts, subway tracks, drilling. and so on. In order to meet the needs of the domestic industry such as cost down and automatic production, this study was conducted with a 4 mm thin plate friction stir welding (FWS) by using a non-inclinating stirrer process with an automated CNC (Computerized Numerical Control) machine, In this study, the 5083-H321 aluminum alloy test piece, completed by friction stir welding, was subjected to the examinations of welding bead surface and welding bead section. Finally, the qualified weld test piece was analyzed and compared with the substrate of raw material, including tensile tests, metallographic observations, Vicker hardness tests, X-ray diffraction, SEM, EDS and electrochemical corrosion tests. In the tensile test, the yield strength and the elastic coefficient welding bead are greater than that of the substrate, and the resisting ability of axial deformation is larger than the substrate. In the metallographic test, it is observed that the grain in the welding bead is finer after the friction stir welding. Verified by Hall-Petch equation. The yield strength of finer grain sized material is better, and so it the hardness. Since the fracture is found at the substrate, it is speculated that the higher the hardness, the stronger the strength is. The diffraction intensity ratio of (111) to (200) is varied and observed by X-Ray diffraction, indicating that the rolled 5083-H321 aluminum alloy has a preferential orientation and then back into random orientation after welding. From the energy dispersive X-ray spectroscopy(EDS), it is found that there are (MnFe)Al6 precipitates in the welding bead, leading to the increasing strength and the slightly decreasing corrosion resistance of the welding bead. Finally, the weld mechanical properties such as hardness and strength of 5083-H321 aluminum alloy 4 mm sheet through the tipless mixing head process FWS are better than the substrate, while the related corrosion resistance of the welding bead is deteriorated slightly. It is concluded that under the appropriate welding parameters, it is feasible to set the appropriate friction stir welding process without tilting the mixing head.

Automation of Capacitor Discharge Welding (CDW) has not been investigated in industry due to the limited understanding of the process. The US Department of Energy's Albany Research Center (ALRC) has done an extensive study of the process and reported applications of welds in the manufacture of electro-mechanical products such as relays and circuit-breakers. The main purpose of this work was to investigate automation of the load/unload cycle of CDW. An automatic CDW machine was built with real-time quality monitoring capabilities. Tooling and fixtures were fabricated for joining silver to brass components used in a circuit breaker assembly. A machine controller was used to automatically sequence the process and the actuators. Computer-based instrumentation was developed for on-line data acquisition and quality monitoring of the weld. This demonstrational setup shows that the equipment can be compact and the process can be easily automated for high production rates. The automation architecture developed can be used as a general model for automating CDW operations in other environments. The automated CDW system was tested by welding silver contacts to brass brackets at different parameter settings. Metallographic examination of the resultant capacitor discharge (CD) welds (made by the automated CDW system) revealed the formation of continuous metallurgical bonds between silver and brass. A comparison of CD welds made by the manual and the automated system was performed to determine the effect of CDW automation on weld quality. The welds were also found to be superior to resistance welds.
Graduation date: 1997

碩士
國立屏東科技大學
材料工程研究所
105
This research is aim to discuss the influence of adding A-RSW in soldering process to the feature of soldering stainless steel. Steel materials are applied with 2 mm of 304 stainless steels; planting materials are M6 and M8 of 304 stainless steels, activated powder is SiO2. The research reveals stainless steel stud sequentially displays incomplete melt in completely melted and fused melt fracture when improving the welding current or welding time, in the condition where the length of protruding planting nail and arc length are the same. Because the active Stud arc welding processes can increase the contact resistance, the use of a lower welding current or welding time can be shorter Stud Welding. Compared with traditonal arc welding stud, active arc welding stud can effectively improve stainless steels and the channel penetration. The study has found that the soldering process of active arc stud can enhence stainless steel weld residual ferrite content: furthermore, being able to aquire the stainless steel soldering channel hardness rate of more traditional arc welding process. Keywords: Stainless steel; Activated flux; Stud welding

碩士
國立虎尾科技大學
材料科學與綠色能源工程研究所
103
This study is aimed at discussing the effect on microstructure, mechanical properties, and bond stress for welding 17-4PH stainless steel and high stress steel with capacitor discharge stud welding of different parameters, such as: working pressure (6 kgf, 8Kgf and 10 kgf), electric voltage (70~ 120 V). From elongation test, the best values are obtained at the electric voltage from 80V to 100V, and three kinds of pressure parameters. The coverage of stud bead in this range is the most intact. especially at pressure of 8kgf and 10 kgf and electric voltage of 100V; which leads to better stress. But the phenomenon of liquid metal splashing gets worsen when electric voltage is over 100V; which makes coverage of welding bead incomplete and porosity increase;It also damages metal studs and sheets.After comparing average width of heat affective zoom, the metal sheets are heat effected worse than the metal stud is, which means the splashing liquid metal is from the molten metal sheets.By observing microstructure, it''s found that the stud bead cooling rate is quick; the microstructure of stud bead is turned into the mix phase of martensite and bainite.

碩士
國立臺灣師範大學
機電工程學系
103
This study was divided into two parts. First, we used self-reacting pin tool (or could be known as a bobbin tool)which was designed by myself to weld different aluminum alloy by friction stir welding without any heat source, and discussed the possibility of welding. Second, according to experiments of first part, we decided the material of specimen and discussed the mechanical properties under various rotating speed at fixed welding speed. Last, the specimen was observed by metallographic test, optical microscope and scanning electron microscope. A 1050 aluminum alloy was friction stir welded by self-reacting pin tool. The geometry of the weld nugget zone (WNZ) obviously displayed saddle sharp with the increasing rotation speed. The defects in WNZ were significantly raising with the increasing welding speed. The values of microhardness at soft region were lower than base material and it decreased with the increasing welding speed, but the microhardness in WNZ was increased with increasing welding speed. Ultimate tensile strengths would be increased with increasing welding speed in the tensile tests. And the average ultimate tensile strength of specimen could reach 59% of the base material. The tensile fracture surfaces of the joints were analyzed by scaning electron microscope, as presented the ductile fracture mode.

碩士
國立中山大學
機械與機電工程學系研究所
100
This study aims to design a novel inserted welding tool to friction stir spot weld SS400 low carbon steel sheets of 4mm thickness. In order to enhance the efficiency of frictional heat generation and to enhance the quality of the welding spot, the welding tool based on a cylindrical tungsten carbide and is inserted by a SS400 low carbon cylinder. The welding apparatus composed of a vertical milling machine and a welding platform that can keep the load between tool and workpiece constant. The plunge load is 8kN and there''s no inclination angle on the tools. Welding temperature and the tool plunge depth are measured by thermelcouples and a displacement meter. 　　At the tool rotational speed of spindle of 900rpm and welding for 60 seconds, the temperature rising rate of the tools with 5 mm and 10 mm inserted material are 5.28 times and 6.31 times greater than the one without insert. While they are 1.36 and 1.42 times greater than at 1200rpm.At the tool rotational speed of spindle of 900rpm and welding for 300 seconds, themaximun welding temperature the tools with 5 mm and 10 mm inserted material can reach are 59℃ and 412℃ higher than the one without insert. While they can reach 35.6℃ and 197.6℃ greater than at 1200rpm. According to the tensile test, the shear failure loads of clad steel plates increase 11.3kN and 15.5kN by using tools with 5 mm and 10 mm inserted material at 900rpm for 60 seconds, and increase 7.6kN and 18.3kN by using tools with 5 mm and 10 mm inserted material at 1200rpm.

博士
國立臺灣科技大學
機械工程系
103
Recently, severe material flow is caused to obtain successful joints by an innovative joining process, called friction stir spot welding (FSSW). Because of its thermomechanical characteristic, the interaction between process parameters and tool geometry makes the process complicated and leads to temperature and pressure difference in welds, resulting in variation of material flow and joint strength of welds. In this study, aluminum alloy sheets were joined by the FSSW process using various threaded tools. The influences of tool geometry and process parameters on material flow evolution, welding force, work, power, weld temperature and joint strength during FSSW were analyzed. In addition, numerical simulation of weld temperature was also discussed. The results indicated that rotational speed and dwell time increase process work and weld temperature, lowering weld torque and material flow resistance. Additionally, threaded locations had little effect on weld temperature in local regions. The highest temperature was shown in the upper sheet region, which was nearest to the shoulder. During tool plunging, the lower sheet penetrated into the upper sheet. A sheet interface and rotational speed was beneficial for promoting the penetration behavior. In a dwell period, sink and source of material were formed at the ends of threads. Material flowed into threaded sections via material sink, following moving forward to material source to form a stir zone (SZ). The growth of SZ squeezed the sheet interface, resulting in the variations of weld morphology and joint strength. The reduction in upper sheet thickness was suppressed in the T-tool welds, thus exhibiting superior joint strength. In addition, the welds joined by tools with 900 rpm, 9 s and counterclockwise rotation showed superior joint strength.

碩士
南台科技大學
機械工程系
97
Both 2024-T3 and 7075-T6 are heat treatable aluminum alloys which have been applied widely in aerospace industry, due to their high specific strength and corrosion resistance. However, if the welding parameters for the aluminum alloy are inappropriately specified during the traditional welding process, defects such as high porosity and solidification cracking can occur easily. Friction stir welding (FSW), which is different from traditional arc welding, is used on welding process conducted under the melting point, and is an emerging solid-state joining process that produces low-distortion and high-quality welds. FSW will effectively better general welding quality. In this study, FSW processes are conducted on 2024-T3 and 7075-T6 aluminum alloys, 3mm thick. The major areas discussed were, the effect of the welding parameters, the microstructures and hardness in different tool pin shapes (threaded cylindrical, threaded triangular). The results show that the grain size of both tool pin shapes was significantly reduced in the fixed rotation speed after welding, but the hardness of the weld increased. This is because the input heat decreases with welding speed increasing. This increasing trend of hardness was not apparent for the threaded triangular pin shape. However, the hardness of the weld in the 2024-T3 alloy increased, and in the 7075-T6 decreased while welding speed was fixed and the rotation speed increased. This can be attributed to the different internal precipitation mechanisms of the two materials. When either fixed rotation speed or welding speed was changed the welding quality for threaded triangular was found to be better than that for the threaded cylindrical tool pin. In addition, the threaded triangular tool pin allows greater plastic flow, with the 2024-T3 specimen having a greater amount of plastic flow than the 7075-T6. The results for the different welding materials indicated that as the rotation speed increased, there was a tendency for weld appearances to become more homogenous and the threaded triangular tool pin was better. In term of hardness, the hardness of specimens using both types of tool pins was improved as the rotation speed and the welding speed were increased. For the hardness of the TMAZ and HAZ located at the two sides of the specimens, the retreating side in 2024-T3 was better than its advancing side. Between the tool pins, the threaded triangular was providing higher hardness than the threaded cylindrical pin. In the specimen AS(2024)-RS(7075), the tensile strength and elongation ratio of the weld increased when the rotation speed and the welding speed were increased for the threaded triangular tool pin. However, in the case of the threaded cylindrical tool pin, both tensile strength and elongation ratio decreased. Furthermore, the tensile strength and elongation of AS(7075)-RS(2024) was generally lower than that of AS(2024)-RS(7075). For the tool pin shape, threaded triangular was better.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
O processo de soldadura por fricção linear (FSW) é um método muito adequado para a união de materiais similares ou dissimilares. A soldadura de materiais dissimilares é muito complexa ou mesmo impossível através dos métodos de soldadura por fusão.A presente dissertação estuda a influência da geometria da ferramenta bem como de parâmetros de processo na qualidade das soldaduras obtidas por FSW dissimilares em juntas T, constituídas pelas ligas de alumínio AA5083-H111 e AA6082-T6. Duas geometrias de ferramenta foram utilizadas na realização das soldaduras, uma com pino piramidal progressivo e outra com pino cónico roscado progressivo. A configuração de junta foi estruturada com o objetivo de permitir o completo preenchimento das regiões de concordância sem que ocorra redução de espessura do skin. O fluxo de material nas soldaduras foi analisado através de microscopia ótica e eletrónica assim como a análise EDS com vista a reduzir ou mesmo prevenir a formação de defeitos.A geometria, a velocidade de rotação e de avanço da ferramenta revelaram um papel importante no fluxo e mistura dos materiais. A diminuição da razão entre a velocidade de rotação e a velocidade de avanço reduziu o calor adicionado aos materiais, o que levou à formação de defeitos no lado do avanço das soldaduras, devido a um fluxo inadequado.As soldaduras nas quais a liga AA6082-T6 constituía skin mostraram uma redução relevante da dureza na região soldada, contrariamente às soldaduras em que o skin era composto pela liga AA5083-H111, onde esta redução não foi tão significativa. Os ensaios de tração e de arrancamento revelaram que as juntas efetuadas com a ferramenta com pino cónico roscado progressivo são mais eficientes comparativamente às produzidas com a ferramenta com pino piramidal progressivo.Nos testes de fadiga, a ferramenta com pino piramidal progressivo permitiu a obtenção de curvas S-N de soldaduras dissimilares próximas das curvas caraterísticas de soldaduras similares em juntas T.
Friction stir welding (FSW) is a very suitable process for joining similar or dissimilar materials. The welding of dissimilar materials is currently very difficult or even impossible by fusion welding processes.The present dissertation studies the influence of tool geometry as well as the process parameters on the quality of FSW welds of dissimilar T-joints made of AA5083-H111 and AA6082-T6 aluminum alloys. Two tools geometries were used in the welding process, one with a progressive pyramidal pin and the other with a progressive tapered threaded pin. The joint preparation was designed in order to allow the complete filling of the fillets without any reduction of the skin thickness. The material flow in the welds was analyzed by optical and electronic microscopy as well as by EDS analysis in order to reduce or even prevent the defect formation. The tool geometry, the tool rotation speed and the welding speed revealed a key role in the flow and mixing of the materials. The decrease of the ratio between the rotation speed and the welding speed decreased the heat input to the materials, which led to the formation of defects on the advancing side of the welds, due to inadequate material flow.The welds in which the AA6082-T6 alloy was the skin showed a drastic reduction in hardness in the weld as opposed to those where the alloy AA5083-H111 was the skin. The tensile tests and pullout tests showed that the joints done with the progressive tapered threaded pin tool are more efficient than those made with the pyramidal progressive pin tool.In the fatigue tests, the tool with progressive pyramidal pin allowed obtaining S-N curves of dissimilar welds close to those for similar T welds.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
A soldadura por fricção linear (FSW) surge como um método de soldadura inovadora e amplamente requisitada para indústrias de ponta, como a indústria aeroespacial, naval e automotiva. O processo emerge como uma tecnologia substituta e vantajosa em relação aos processos de soldadura por fusão convencional, especialmente na união de materiais considerados não soldáveis e materiais dissimilares.O objetivo deste trabalho é averiguar quais as condições de fabricação que viabilizem a produção de soldaduras de boa qualidade, utilizando materiais com diferentes características. Nesse sentido, foram utilizadas as ligas de alumínio AA2017-T4, AA5083-H111 e AA6082-T6 sob a forma de chapas de 3 mm de espessura. Parâmetros do processo, como a velocidade de soldadura, posição dos materiais de base na junta e o uso de diferentes geometrias de ferramenta foram alvos de estudo. Para a pesquisa da soldabilidade de juntas em T dissimilares e tridissimilares usando o FSW, pretende-se estudar o efeito das alterações dos parâmetros citados na morfologia e no comportamento global das soldaduras produzidas. Os fluxos do material e a microestrutura das juntas soldadas foram examinados por microscopia ótica, procurando relacionar as caraterísticas observadas com as condições intrínsecas de processamento. A fim de obter uma visão quantitativa e qualitativa do comportamento mecânico das juntas, foram executados os testes de microdureza e ensaios de tração e de fadiga, exclusivos para as soldaduras sem defeitos. Foram adquiridas soldaduras sólidas e de boa qualidade tanto na ligação de materiais tridissimilares e dissimilares, contudo era essencial a sua concepção utilizando ferramentas progressivas. Nas soldaduras realizadas com ferramentas simples, constatou-se que maiores rácios entre velocidade de soldadura e velocidade de avanço favoreciam o aparecimento de defeitos macroscópicos de maior dimensão, como defeitos de túnel e kissing bond. Deste modo, a velocidade de avanço e a geometria da ferramenta alteraram significativamente os estados de mistura e a estrutura da soldadura.
Friction stir welding (FSW) arises as a modern and widely required welding method for leading industries, such as aerospace, naval and automotive industries. O process emerges as an alternative and advantageous technology in relation to conventional fusion welding processes, especially in a union of materials considered non-weldable and dissimilar materials.The purpose of this work is to investigate which manufacturing conditions enable the production of high-quality welds, using materials with different characteristics. In these sense, AA2017-T4, AA5083-H111 and AA6082-T6 aluminum alloys were used in the shape of 3 mm thick plates. Process parameters, such as welding speed, position of base materials in the joint and the use of different tool geometries were study targets.For the research of dissimilar and tridissimilar T-joint weldability using FSW, it is expected to study the effect of the variations in the parameters cited in morphology and overall behavior of the welds produced.The material fluxes and the microstructure of the welded joints were examined by optical microscopy, trying to relate the characteristics observed with the inherent conditions of processing. In order to obtain a quantitative and qualitative view of the joint’s mechanical behavior, microhardness tests and tensile and fatigue tests were performed, exclusive to free-defect welds. Robust and high-quality welds were acquired for both tridissimilar and dissimilar materials bonding, however, its design using progressive tools was essential. In welds performed with simple tools, it was found that higher ratios between welding speed and traverse speed favored the appearance of larger macroscopic defects, such as tunnel defects and kissing bond. Thus, the traverse speed and the tool geometry significantly altered the mixing states and the welding structure.