Дисертації з теми "Welding generator"

Дисертація присвячена питанням підвищення ККД зварювальних генераторів постійного струму. З метою підвищення ККД запропонована нова комбінована електромагнітна та магнітоелектрична система збудження зварювального генератора. Розроблена методика розрахунку електромагнітних характеристик генератора за результатами розрахунку магнітного поля методом скінчених елементів. Проведено аналіз впливу торцевих полів розсіювання на адекватність моделі постійного магніту прийнятої при розрахунку магнітного поля. Розроблена математична модель залежності усталеності горіння дуги від довжини повітряного зазору та струму збудження. Створена загальна схема розрахунку зварювального генератора. Розроблено та створено експериментальний зварювальний генератор з комбінованим збудженням та проведено його випробування. Створена модель дослідного зварювального генератора.
The dissertation is devoted by a problem of increase efficiency of welding generators of a direct current. With the purpose of increase efficiency the offered new combined electromagnetic and permanent magnet system of excitation of the welding generator. The design procedure of electromagnetic characteristics of the generator on results of calculation of a magnetic field is created by a method of final elements. The analysis of influence of face fields of dispersion on adequacy of model of a constant magnet accepted is carried spent at calculation of a magnetic field. The mathematical model of dependence of stability of burning of an arch from length of an air backlash and a current of excitation is developed. The general circuit of calculation of the welding generator is created. The experimental welding generator with the combined excitation is developed and created and its tests are carried spent. The created model of the experienced welding generator.

The task of designing concepts for the next generation of submerged arc welding heads was given by ESAB. ESAB is a global company manufacturing welding equipment for a wide span of industries and uses. In October 2011, ESAB introduced a new technology called Integrated Cold Electrode™, abbreviated and trademarked as ICE™. ICE™ is a technique which utilizes three electrodes in a highly productive and stable process. The current state of the ICE™ technique focuses on welding thick plates with conventional joint types such as x- and v-joints. The next phase in the development of the technique is to be able to weld milled 16/8°-joints which are developed by German company Graebner. This kind of joint determines the requirements of the next generation of ESAB’s equipment for submerged arc welding.Simultaneously as designing the welding torch being able to weld the 16/8°-joint, a concept for a highly customizable modular head was developed enabling the possibility to tailor the submerged arc welding process according to the customer’s precise needs.A progressive conceptual development has been conducted in close collaboration with ESAB. Theoretical models have been developed to evaluate thermal-electric behavior of the welding torches to obtain plausible dimensions for the electric conductors to withstand the effects caused by joule heating. Deliverables for the project has been well defined 3D CAD-models while a prototype was not included in the scope of the project.One concept for the 16/8° joint is presented as the Narrow Joint Concept, NJC, which fulfills the requirements specified. The NJC is developed with focus on smart design with low manufacturing cost as well as ease-of-use for the operator. NJC brings ICE™ into narrow joints.The Modular Head Concept, MHC, presents an idea how to create a fully customizable process with the possibility to emulate the ICE™ technique
Uppdraget att utveckla nästa generation pulverbågsutrustning gavs av företaget ESAB. ESAB är ett globalt företag som tillverkar svetsutrustning för ett brett spann av branscher och användningsområden. I oktober 2011 lanserade ESAB en ny teknik vid namn Integrated Cold Electrode™, ICE™. ICE™ är en teknik som utnyttjar tre stycken elektroder i en högproduktiv och stabil svetsprocess. I dagsläget fokuserar ICE™-tekniken på att svetsa konventionella fogtyper såsom x- och v-fogar i tjocka plåtar. Nästa fas i utvecklingen av tekniken är möjligheten att svetsa frästa 16/8°-fogar som det tyska företaget Graebner utvecklar. Denna typ av foggeometri ger kraven för ESAB’s nästa generation pulverbågsutrustning.Simultant togs koncept fram för att möjliggöra skräddarsydd utrustning efter kunders specifika processbehov.En progressiv konceptutveckling har utförts i nära sammarbete med ESAB. Teoretiska modeller har tagits fram för att utvärdera de termo-elektriska egenskaperna hos de utvecklade svetshuvudena så att dessa kan motstå den resistiva uppvärmningen som sker i de elektriska ledarna. Då en prototypframtagning ej låg inom ramen för arbetet har detaljerade 3D CAD-modeller producerats.Konceptet för 16/8°-fogen kallas Narrow Joint Concept, NJC, och uppfyller de uppställda kraven. NJC är framtaget med fokus på smart konstruktion där låg tillverkningskostnad och enkel användning har premierats. NJC sammanfogar ICE™ och smala fogar.Det modulära konceptet kallat Modular Head Concept, MHC, representerar en idé för att skapa skräddarsydda lösningar efter kunders behov. MHC äger förmågan att fungera som ett ICE™-huvud.

The research is focused on the development of an expert system to generate welding procedures for arc welding processes. The system has been developed on an IBM AT microcomputer, using an expert system shell KES (Knowledge Engineering System), a product of Software Architecture & Engineering Inc. The system is primarily intended for novice users, hence good 'help' facilities and graphical representations are provided in the system.

In this project, we have successfully joined MA956 Oxide Dispersion-Strengthened (ODS) steel plates using Friction Stir Welding (FSW). ODS steels are prime candidate materials for the fuel cladding in Generation IV nuclear fission reactors and as first wall components in nuclear fusion reactors. This is due to their exhibiting excellent high temperature strength and creep behaviour, together with enhanced resistance to radiationinduced void swelling. ODS steels are heavily reliant on a fine dispersion of (Y-Al-O) nanooxide particles to provide the aforementioned properties. This, however, makes ODS steels particularly problematic to join. Most joining techniques melt the material along the joint line, but this would severely alter or deplete the nano-oxide dispersion and hence be highly detrimental to the material’s performance in a nuclear environment. FSW is a solid-state joining technique, and therefore can join ODS steel without melting the material. Although FSW can potentially alter the microstructure of the base material and affect the distribution of nano-oxide particles, if a sufficient number of nano-sized particles and a sufficiently homogeneous dispersion remain after the welding process, then a major roadblock for the implementation of ODS steels will have been removed. The research of this thesis focused on the impact of FSW on: i) the microstructure, ii) the mechanical properties, iii) the residual stresses, and iv) the abnormal grain growth behaviour of ODS steels; utilizing a wide array of techniques to assess the micro-to-nano scale structure and the properties of the base material and welds, including optical, scanning and transmission and electron microscopy, X-ray and neutron diffraction, small-angle neutron scattering, tensile testing and micro-hardness measurements. We also produced welds with systematic changes to the tool traverse speed and rotation speed to investigate the impact of changing the welding parameters on the weld microstructure, and therefore optimise the process parameters for enhanced radiation and mechanical performance of the ODS steel welds.

Finite element models of friction welding can be used to estimate internal conditions of welds which are useful for weld analysis and developing experimental welding procedures. Many modeling techniques are used to accomplish these goals, each with relative strengths and weaknesses. A comparative analysis of friction welding models using different heat generation methods is presented. The three different heat generation methods examined were viscoplastic friction, constant steady-state generation, and experimentally measured power data. The models were compared against each other using three output measurements: temperature, axial force, and upset. The friction model predicted temperatures within 40 degrees C. Temperature accuracy improved at a higher upset rate and higher spindle speed, when weld samples heated up faster. The model was excellent at predicting upset, with accuracy within 1.5%. Maximum force was predicted within 9-18%. The constant heat generation model typically predicted temperatures within 30 degrees C. Upset was estimated within 7%. Maximum force was predicted within 12% at high feed rates, but accuracy dropped to 28% when feed rate was reduced. The motor power model was the most accurate model at estimating temperature, with a typical accuracy within 25 degrees C. Axial upset was predicted within 5%. Maximum force was predicted within 1-8%, with greater accuracy occurring at higher feed rates.

The overall purpose of this research is to develop a real-time ultrasound based system for controlling robotic weld quality by monitoring the weld pool. The concept of real-time weld quality control is quite broad, and this work focuses on weld penetration depth monitoring and control with laser ultrasonics. The weld penetration depth is one of the most important geometric parameters that define the weld quality, hence remains a key control quantity. This research focuses on the implementation and optimization of the laser phased array generation unit and the development of signal analysis algorithms to extract the weld penetration depth information from the received ultrasonic signals. The system developed is based on using the phased array technique to generate ultrasound, and an Electro-Magnetic Acoustic Transducer (EMAT) as a receiver. The generated ultrasound propagates through the weld pool and is picked up by the EMAT. A transient FE model is built to predict the temperature distribution during welding. An analytical model is developed to understand the propagation of ultrasound during real-time welding and the curved rays are numerically traced. The cross-correlation technique has been applied to estimate the Time-of-Flight (ToF) of the ultrasound. The ToF is then correlated to the measured weld penetration depth. The analytical relationship between the ToF and penetration depth, obtained by a ray-tracing algorithm and geometric analysis, matches the experimental results. The real-time weld sensing technique developed is efficient and can readily be deployed for commercial applications. The successful completion of this research will remove the major obstacle to a fully automated robotic welding process. An on-line welding monitoring and control system will facilitate mass production characterized by consistency, high quality, and low costs. Such a system will increase the precision of the welding process, resulting in quality control of the weld beads. Moreover, in-process control will relieve human operators of tedious, repetitive, and hazardous welding tasks, thus reducing welding-related injures.

Thesis (Ph. D.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 13, 2006) Vita. Includes bibliographical references.

The effect of friction stir welding on the microstructure, precipitation, mechanical properties, and tensile fracture has been studied. Friction stir welding has been applied to a third generation Al-Cu-Li alloy, the AA2199, in the T3 condition. Post weld heat treatment (PWHT) to the T8 condition, was carried out to artificially age the welds and improve mechanical properties. Welds were characterised using field emission scanning electron microscopy (FE-SEM) with electron channeling contrast imaging (ECCI), differential scanning calorimetry (DSC), micro-hardness, and tensile testing. Welds created with tool rotation speed of 877RPM showed ultimate tensile strength level of 93% of base metal in the T8, an elongation of 6% at fracture, and microhardness values ranging between 120-140 HV across the welds. The ability of welds to gain in hardness and strength during PWHT has been linked to the limited formation of large scale precipitates which act as sinks for alloying elements.
L'effet du soudage par friction-malaxage sur la microstructure, la precipitation, les propriétés mécaniques et la rupture par traction ont été étudiés. Le soudage par friction-malaxage a été appliqué à une troisième génération d'alliage d'Al-Cu-Li, le AA2199-T3. Un traitement thermique après soudage (PWHT) sur l'alliage AA2199-T8 a été réalisé pour vieillir les soudures artificiellement et en améliorer les propriétés mécaniques. Les soudures ont été caractérisées par microscopie électronique à balayage (FE-SEM), par imagerie en contraste cristallographique (ECCI), par calorimétrie différentielle à balayage (DSC) et par des essais de micro-dureté et de traction. Les soudures créées avec une vitesse de rotation d'outil de 877RPM ont montré une limite à la rupture de 93% par rapport la plaque de depart, un allongement à la rupture de 6% , et des valeurs de microdureté variant entre 120 à 140 HV dans les soudures. Le gain en dureté et en résistance du matériau dans les zones soudées au cours du traitement thermique PWHT est lié à la formation à grande échelle de précipités absorbant les éléments d'alliage.

碩士
國立中興大學
機械工程學系所
104
The understanding of the Acoustic Emission (AE) generation and propagation in material during laser welding will be helpful to the development of the welding quality monitoring system. In this thesis, the experimental analysis of AE signal generation during laser welding and the AE signal propagation inside bulk and multi-layer material are focused. In the signal generation analysis, experiments with various laser powers were conducted to investigate the signal variation with the proceeds of the welding process. At the same time, the high speed camera was also setup to investigate the condition of welding pool during laser welding. In signal propagation analysis, the steel cubic samples with/without slot and curvature design were used for studying the path effect on the AE signal propagation through material. The multi- steel sheets with the installation of AE sensor on each layer of steel were also adopted to study the variation of the AE signal propagation affected by the contact condition between layers. The results show that the collected signals will be affected with the torque for sensor installation lower than 1.5N-m. In signal propagation study, AE signals obtained from the sensors located at various location will affected significantly by the propagation path, especially for the beginning period of signal generation. In considering the gap effect on signal propagation in multi-layer steel sheets study, the signal will not propagate completely to the bottom layer sheet at the beginning period of signal generation. However, signal energy collected by the AE sensor on the bottom layer will increase gradually until 0.22ms. In the study of signal generation during laser welding, two high energy burst signal can be observed in the first half period of laser welding with the laser power higher than 300W. By contrast, only one burst signal obtained with laser power lower or equal to 300W. By the way, the time span between two burst signals will increase as the laser power lower down from 900 W. In comparison to the photos obtained from the high speed camera, the burst AE signals map well to the period with the quick change of the lighting area at welding point. By contrast, the low signals map well to the period with stable lighting area.

博士
逢甲大學
機械與航空工程博士學位學程
104
The Hybrid Spline Difference Method is developed to solve the direct nonlinear heat transfer problem in ultrasonic welding process. Verification by welding problem finds that the presented method can simplify the complex determination process of traditional spline theory. Interestingly, its concept is very similar to that of finite difference method; however, its numerical accuracy is significantly enhanced. Thus, not only the hybrid spline difference method presented in this thesis has a simple computational process, but also it can be strongly potential replaced the conventional finite difference method and complicate spline method. The Broyden–Fletcher–Goldfarb–Shanno (BFGS) inverse algorithm is investigated to predict the unknown time-dependent heat generation at the weld interface and convection heat transfer coefficient during a one-dimensional ultrasonic metal welding process based on the knowledge of temperature measurements taken on the horn. With known temperature data at some locations on the horn, the inverse solution was rapidly obtained through a computational procedure that involves the hybrid spline difference method for nonlinear direct problem, central finite difference, and simple step method in collaboration with BFGS method. The proposed algorithm, which did not need solving adjoint problem and sensitivity problem, reveals the characteristics of high efficiency, lower iterations, and high accuracy for estimating values even when measurement errors were considered. These results show that an accurate estimation on interfacial heat generation (or temperature) and the convection coefficient can be quickly found with arbitrary initial guesses. The BFGS combined with steepest descent method (SDM) is proposed for estimating unknown interface heat generation in a two-dimensional ultrasonic seam welding process. If the temperature within a lower workpiece is known, the interface temperature and heat generation can be determined inversely through the direct problem, adjoint problem, and simple step method. When the simple step method is used to find the search step length instead of the sensitivity problem, the computational algorithm becomes easier to calculate unknown parameters. Moreover, the convergence speed of the proposed inverse method is compared to that of the previous methods (i.e. BFGS, CGM and SDM). Special feature of proposed method is stable, accurate, and efficient for estimating moving heat sources and interface temperature even including some degree of measurement errors. In addition, the influence of the measurement location on the accuracy of estimated solutions with or without error of measurement was also discussed. These findings indicate that the estimated heat generation is more sensitive than the temperature to different measured temperatures and locations. To broaden the application of the inverse method, the BFGS method is continuously developed to estimate unknown interface heat generation during an actual ultrasonic seam welding with knowledge of experimental temperatures in a workpiece. Following the computational iteration process contains reading experimental temperature, solving adjont problem, using BFGS method, and using simple step method, the nonlinear inverse ultrasonic welding problem can be accurately solved. The estimated temperature was in very good agreement with the measurement temperature. In addition, the heat generation and its distributed range as well as interface temperature were rapidly predicted. According to understanding of the temperature distribution history at the workpieces and heat generated at the interface, the occurrence of thermal defects can be avoided during the welding process. In addition, the proposed method, which is a reliable and robust method for solving some welding applications, strongly provides valuable information for the optimization problem in the ultrasonic welding process. Therefore, the welding conditions can be appropriately adjusted, and then the weld quality will be controlled entirely.