Showing papers on "Butt welding published in 2010"

Numerical simulation of friction stir butt welding process for AA5083-H18 sheets

Abstract: Thermo-mechanical simulation of the friction stir butt welding (FSBW) process was performed for AA5083-H18 sheets, utilizing a commercial finite volume method (FVM) code, STAR-CCM+, which is based on the Eulerian formulation. Distributions of temperature and strain rate histories were calculated under the steady state condition and simulated temperature distributions (profiles and peak values) were compared with experiments. It was found that including proper thermal boundary condition for the backing plate (anvil) is critical for accurate simulation results. Based on the simulation, thermal and deformation histories of material elements were also calculated, useful to predict material characteristics of the weld such as hardness or grain size, and possibly for the susceptibility of weld to abnormal grain growth (AGG) after post-weld heat treatment.

Modeling of AA5083 Material-Microstructure Evolution During Butt Friction-Stir Welding

Abstract: A concise yet a fairly comprehensive overview of the friction stir welding (FSW) process is provided. This is followed by a computational investigation in which FSW behavior of a prototypical solution-strengthened and strain-hardened aluminum alloy, AA5083-H131, is modeled using a fully coupled thermo-mechanical finite-element procedure developed in our prior study. Particular attention is given to proper modeling of the welding work-piece material behavior during the FSW process. Specifically, competition and interactions between plastic-deformation and dynamic-recrystallization processes are considered to properly account for the material-microstructure evolution in the weld nugget zone. The results showed that with proper modeling of the material behavior under high-temperature/severe-plastic-deformation conditions, significantly improved agreement can be attained between the computed and measured post-FSW residual-stress and material-strength distribution results.

Torque control of friction stir welding for manufacturing and automation

Abstract: Friction stir welding (FSW) is a solid-state welding process that utilizes a rotating tool to plastically deform and forge together the parent materials of a workpiece. The process involves plunging the rotating tool that consists of a shoulder and a pin into the workpiece and then traversing it along the intended weld seam. The welding process requires a large axial force to be maintained on the tool. Axial force control has been used in robotic FSW processes to compensate for the compliant nature of robots. Without force control, welding flaws would continuously emerge as the robot repositioned its linkages to traverse the tool along the intended weld seam. Insufficient plunge depth would result and cause the welding flaws as the robot’s linkages yielded from the resulting force in the welding environment. The research present in this paper investigates the use of torque instead of force to control the FSW process. To perform this research, a torque controller was implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative control architecture was tuned using the Ziegler–Nichols method. Welding experiments were conducted by butt welding 0.25 in. (6.35 mm) × 1.5 in. (38.1 mm) × 8 in. (203.2 mm) samples of aluminum 6061 with a 0.25 in. (6.35 mm) threaded tool. The results indicate that controlling torque produces an acceptable weld process that adapts to the changing surface conditions of the workpiece. For this experiment, the torque was able to be controlled with standard deviation of 0.231 N-m. In addition, the torque controller was able to adjust the tool’s plunge depth in reaction to 1 mm step and ramp disturbances in the workpiece’s surface. It is shown that torque control is equivalent to weld power control and causes a uniform amount of energy per unit length to be deposited along the weld seam. It is concluded that the feedback signal of torque provides a better indicator of tool depth into the workpiece than axial force. Torque is more sensitive to tool depth than axial force. Thus, it is concluded that torque control is better suited for keeping a friction stir welding tool properly engaged with the workpiece for application to robotics, automation, and manufacturing.

Weld defect detection systems and methods for laser hybrid welding

Abstract: Laser hybrid welding systems adapted to identify and/or fix a weld defect occurring during a laser hybrid welding process are provided. Embodiments of the laser hybrid welding system may include one or more devices that provide feedback to a controller regarding one or more weld parameters. One embodiment of the laser hybrid welding system includes sensors that are adapted to measure the weld voltage and/or amperage during the welding process and transmit the acquired data to the controller for processing. Another embodiment of the laser hybrid welding system includes a lead camera and a lag camera that film an area directly in front of the weld location and directly behind the weld location.

Arc welding system, single arc welding system, and tandem arc welding system

Abstract: An arc welding system according to the present invention includes a welding power supply for supplying welding power to a welding wire, a welding robot including a welding torch mounted to an arm fore end thereof, and a controller for controlling the welding power supply and the welding robot. The welding power supply and the controller perform communication using digital signals, and the welding power supply outputs, to the controller, a welding power-supply feedback signal obtained at the time of inputting of a welding power-supply sync signal. With that configuration, accurate arc tracking can be realized by using the digital signals.

Robot welding seam tracking method based on passive vision for thin plate closed-gap butt welding

Abstract: A passive vision sensor is added to a teaching and playback welding robot for pulsed gas tungsten arc welding, which is normally used in the welding of thin plate closed-gap butts. This paper presents a seam tracking method based on this sensor through period visual measurement of the offset between the torch and the seam center. A robust image processing algorithm is developed to extract the seam center. A kind of ARX(auto-regressive with exogenous input) model is studied to describe the relationship between the rectifying voltage and the offset. The fuzzy PID(proportional-integral-derivative) seam tracking controller is analyzed and designed in consideration of various offsets based on the ARX model. The experimental results on straight line weld display a good seam tracking capability of the proposed method.

Visual seam tracking system for butt weld of thin plate

Abstract: An image-based visual seam tracking system is designed for butt weld of thin plate in this paper The torch deviation from the joint in the horizontal direction is measured from the seam image Since the weld seam is so narrow, its image is based on natural lighting Due to the hardness of measuring depth information using monocular vision, structured laser light is used for detecting the torch deviation in the vertical direction For steady seam tracking, a robust and fast feature extraction algorithm is developed Moreover, a reliable controller is designed with error filtering and output pulse verification Finally, experiments are conducted to verify the proposed seam tracking system

Dual beam method for laser welding of galvanized steel: Experimentation and prospects

Abstract: Laser welding of zinc-coated steel sheets in lap configuration poses a challenging problem, because of the zinc vapours spoiling the quality of the weld. In continuation to the earlier work, the novel solution of dual laser beam method for lap welding of galvanized steel sheets is discussed here in view of the recently obtained observations and ensuing concerns. In this method the precursor beam cuts a slot, thus making an exit path for the zinc vapours, while the second beam performs the needed welding. The metallurgical analysis of the welds is encouraging showing absence of zinc in the welded area. In the current work on this technique, new experimental results have been obtained verifying the earlier observations. Along with this, the possibility of using a transversely split-up beam for the welding purposes with this approach is discussed and analyzed in this paper. This new technique is expected to be very useful in prospective industrial applications requiring higher welding throughput along with the needed quality.

Analysis of pulsed Nd:YAG laser welding of AISI 304 steel

Abstract: Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions. The material properties such as conductivity, specific heat, and mass density were determined as functions of temperature. The latent heat was considered within the given temperature range. The three-dimensional heat source model for pulsed laser beam butt welding was designed by comparing the finite element analysis results and experimental data. This successful simulation of pulsed Nd:YAG laser welding for AISI 304 stainless steel will prove useful for determining optimal welding conditions.

Microstructural characterization of dissimilar friction stir welds between AA2219 and AA5083

Abstract: Fusion welding of dissimilar aluminum alloys is very challenging. In the present work, Al-Cu alloy AA2219-T87 was friction stir welded to Al-Mg alloy AA5083-H321. Weld microstructures, hardness, and tensile properties were evaluated in as-welded condition. Microstructural studies revealed that the nugget region was primarily composed of alloy 2219, which was placed on the advancing side. No significant mixing of the two base materials in the nugget region was observed. Hardness studies revealed that the lowest hardness in the weldment occurred in the heat-affected zone on alloy 5083 side, where tensile failure were observed to take place. Tensile tests indicated a joint efficiency of around 90%, which is substantially higher than what can be achieved with conventional fusion welding. Overall, the results show that satisfactory butt welds can be produced between AA2219-T87 and Al-Mg alloy AA5083-H321 sheets using friction stir welding.

Effect of Compliance and Travel Angle on Friction Stir Welding With Gaps

Abstract: This paper presents an investigation of the effects of friction stir weld tool travel angle and machine compliance on joint efficiency of butt welded 5083-H111 aluminum alloy in the presence of joint gaps. Friction stir welds are produced with a CNC mill and an industrial robot at travel angles of 1 deg, 3 deg, and 5 deg with gaps from 0 mm to 2 mm, in 0.5 mm increments. Results indicate that the more rigid mill resulted in higher joint efficiencies than the relatively compliant robot when welding gaps greater than 1 mm with a 3 deg travel angle using our test setup. The results also show that when gaps exceed 1 mm welds made with a travel (tilt) angle of 5 deg are able to generate higher joint efficiencies than welds made with a travel angle of 1 deg and 3 deg. Based on tool geometry and workpiece dimensions, a simple model is presented that is able to estimate the joint efficiency of friction stir welds as a function of gap width, travel angle, and plunge depth. This model can be used as an assistive tool in optimizing weld process parameters and tool design when welding over gaps. Experimental results show that the model is able to estimate the joint efficiency for the test cases presented in this paper.

Microstructure and mechanical properties of friction stir welded joint of Zr55Cu30Al10Ni5 bulk metallic glass with pure copper

Abstract: Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass (BMG) plate and pure copper plates with 2 mm in thickness were successfully joined by friction stir butt welding. Microstructure characterization revealed that a clear interface between the two materials was formed in the stir zone and no crystallization from the amorphous phase can be detected. On the copper side in the stir zone, a transitional microstructure of refined elongated grain structure, refined equiaxial grain structure and coarse equiaxial grain structure was found varying with the distance from the BMG/Cu interface. The welded joint showed lower hardness than that of the base metals and finally fractured on the copper side in tensile tests. The ultimate tensile strength of the joint was about 253 MPa, which reached up to 95% of the pure copper.

Modeling of laser beam welding of stainless steel sheet butt joint using neural networks

Abstract: Laser beam welding (LBW) of austenitic stainless steel (AISI 304) of thickness 1.6 mm is carried out using 2 kW CW Nd:YAG laser. The effect of laser power, welding speed and beam incident angle on the butt weld bead geometry, i.e. depth of penetration (DOP) and bead width (BW) is investigated. The experiment is designed based on three level Box-Behnken design with replication. Modeling of laser welding of stainless sheet butt joint is performed using backpropagation trained neural network. The predicted results of the research showed a comprehensive and usable prediction of the laser welding parameters for butt joints using neural network.

Welding methods and systems

Abstract: A welding system is provided, in which two electrodes are directed at a joint between two work pieces and the electrodes are energized with DC pulse or AC welding waveforms at a controlled waveform phase angle. The systems include a synchronizing controller to synchronize the welding waveforms, and a work point allocation system provides one or more work point values to the welding machines to provide synergic control of the welding according to a user selected system work point value or parameter. The systems and methods further provide for synchronized work point value modulation for the opposite sides of a dual fillet weld. The system and method further provide a high energy heat source that directs intense heat at a portion of the weld joint to improve weld penetration.

Investigation of force-controlled friction stir welding for manufacturing and automation:

Abstract: Friction stir welding (FSW) is a solid-state joining process for materials with low melting points. The process uses a rotating tool that consists of a shoulder and a pin. The tool plastically deforms the material with its pin and then forges together the parent materials underneath the shoulder. Past research has established that the axial force on the tool that creates the forging pressure is a function of plunge depth, traverse speed, and rotation speed. Historically, force control of FSW has been accomplished by varying the plunge depth of the tool. The research presented in this paper examines the force control of FSW by varying each of the process parameters separately. A force controller was implemented on a retrofitted milling machine. The closed-loop proportional-integral-derivative (PID) control architecture was tuned using the Ziegler-Nichols method. Welding experiments were conducted by butt welding 1 / 4inch (6.35mm) ·1 1 / 2inch (38.1mm) ·8inch (203.2mm) samples of aluminium 6061-T6511 with a 1 /4inch (6.35mm) FSW tool. The results indicate that force control via traverse speed is the most accurate and, as a by- product, heat distribution control along the weld seam occurs. Force control via plunge depth is the least accurate but it compensates for machine and robot deflection. Tensile test data show that greater strength can be obtained through force control via rotation speed. It is concluded that force is maintained by keeping the amount of tool surface area in contract with the workpiece constant throughout the welding process when plunge depth is used as the controlling variable. Force is maintained by varying the rate of heat generation when rotation speed is used as the controlling variable. Lastly, force is maintained by changing the amount of heat deposited per unit length along the weld seam when traverse speed is used as the con- trolling variable. Successful robotic FSW requires to be selected the appropriate controlling variable and the sensitivity of the interaction between the tool and the workpiece to be reduced.

Material flow and mixing patterns during dissimilar FSW

Abstract: The main goal of this investigation is to study the flow pattern and mixing which take place during dissimilar friction stir welding (FSW). Aspects such as the origin of onion rings and development of welding defects are considered. An evaluation of the impact of welding parameters (rotational speed) on material mixing of AA 7075-T6 and AA 2024-T3 (3 mm thickness) dissimilar butt welds was performed. The 'stop action' technique has been employed in order to acquire a close snap shot of the flow and mixing in one of the samples which showed limited mixing but optimal mechanical performance and surface condition. A non-stable rotational flow inside the threads has been identified in this sample due to the formation of a cavity on the rear of the pin. This fact gave rise to characteristic bands in the longitudinal section but it was not enough for developing an onion ring-like mixing pattern.

Investigation of the effect of clamping on residual stresses and distortions in butt welded plates

Abstract: One major disadvantage of many arc welding processes is welding-induced residual stresses and distortions. The non-uniform heating and cooling during arc welding result in non-uniform expansion and contraction of the weld and surrounding base material, which produces undesirable residual stresses and deformations in the welded joint. A number of methods can be used to control welding-induced distortions. The methods used for controlling welding distortions a ect residual stresses and vice versa. One practical method for minimizing welding angular distortions is the use of clamping. In this paper, the e ect of clamping and clamp releasing time on welding residual stresses and distortions in the single-pass butt welding of 304 stainless steel plates are investigated. Cases with and without clamping have been studied, and residual stresses and angular distortions have been predicted by three-dimensional nite element simulation. Moreover, experiments have been carried out to measure temperature histories, angular distortions and residual stresses for the unclamped case to verify the numerical model. The results of this study revealed that clamping and clamp release time have a great in uence on the distribution of residual stresses and nal angular distortions. Using clamping during welding and releasing after cooling to ambient temperature can signi cantly reduce the amount of nal angular distortions.

Development of a Robot System for Pipe Welding

Abstract: Large amount of stainless steel tubes would be applied in the desalination system. If the tubes are welded manually, there would be a lot of the repeated work accompanied with the extremely low efficiency and the welding quality could not guaranteed either. So the best choice to finish the work is using a robotic welding system. In this paper, a robotic system to be employed in welding the pipes for desalination of sea water is introduced. The robotic system contains four revolute axes and could be mounted on a branch pipe, so it can both maneuver between the pipes and adjust to a wide range of pipes’ diameter. Moreover, it is very convenient to take with for it is compact and lightweight. The mathematical method for calculating of the geometry of welding path of the intersecting cylinders is also explained. The welding robot, a digital welding power and the gas shielded system are included in the welding system. The robot movement is controlled by a micro-controller and it could communicate with the host IPC (industrial personal computer) through RS232. Other devices are directly controlled by the host IPC. Finally, a simulation is taken and the result shows that the welding system is able to meet the requirements.

Joining for lightweight vehicles

Abstract: This chapter gives an overview of the joining technologies applicable in the design and manufacturing of lightweight automobile bodies It covers liquid-phase welding, solid-phase welding, mechanical joining, and adhesive bonding for steels, aluminum alloys, and magnesium alloys The process parameters and their effects on joint performance for each process are described Benefits, limitations, and applicability of each process for automotive body construction are also discussed A brief review of the joining techniques for polymer matrix composites is also provided

Mechanical, micro-, and macrostructural analysis of AA7075-T6 fabricated by friction stir butt welding with different rotational speeds and tool pin profiles

Abstract: Friction stir welding (FSW) is a solid state welding process for joining aluminium alloys, has been employed in different industries, and is a new and promising welding process that can produce low-cost and high-quality joints of heat-treatable aluminium alloys because this process uses a non-consumable tool to generate frictional heat in the abutting surfaces and can eliminate some welding defects such as crack and porosity. The various parameters such as rotational speed, welding speed, axial force, and attack angle play vital roles in the FSW process in order to analyse the weld quality. In this research, the impact of processing parameters such as different rotational speed and tool pin profiles on the mechanical, micro-, and macrostructural properties during the FSW process involving the butt jointing of AA7075 T6 is investigated. It is important to note that four-flute and taper threaded pin profiles are utilized and the mechanical characteristics are determined by comparing the ultimate str...

Experimental investigation of onion ring structure formation in friction stir butt welds of copper plates produced by non-threaded tool pin

Abstract: The origin of the onion ring structure is an important issue in friction stir welding process but has not been firmly established yet. This paper peresents optical macro- and micrographs of friction stir welds on a copper alloy produced by a non-threaded tool pin. It is shown that onion ring structure can be created by non-threaded tool pin in transverse cross-section of friction stir weld of copper plate. The macrographs of transverse cross-sections exhibit contrasting bands. A microstructural study shows that the weld has lamellar structure, and the bands are sections of weld layers.

Method of laser machining of fiber-reinforced composite material and product made by the method

Abstract: A method of laser machining of a fiber-reinforced composite material of the present invention is characterized in that the fiber-reinforced composite material or composite ply material (ply material consisting of plates of metal or inorganic material and fiber-reinforced material) is cut using an ultra short pulse solid-state laser having a pulse-width ranging from 10 pico to 100 nano second and a pulse energy of 1mJ-500J, repeatedly irradiated to the material with the number of frequency ranging from 10Hz to 100kHz. According to the present invention, it is possible to work, e.g., cut, pierce, groove, or carve a fiber-reinforced composite material including CFRP, by removing materials by means of a laser with a high precision and good quality. It is also possible to form a fitting joint of proper shape so that a male-female joint may be available in a butt welding that has been hardly feasible. It is further possible to produce structural members such as a light weight panel or a H-column because the male-female joint can be used for a plate of any desired dimension (width, length and thickness).

Method for realizing swing welding with laser-GMA electric arc hybrid welding device

Abstract: The invention discloses a method for realizing swing welding with a laser-GMA electric arc hybrid welding device, relating to a laser-melting electrode gas metal arc welding hybrid welding method The method solves the problem that the defects such as incomplete fusion, gas hole and included slag, and the like, are easily existed between a side wall and a layer when welding a moderate plate and a thick plate with the laser-GMA electric arc hybrid welding device The method comprises the following steps of: 1 chamfering; 2 clamping a work piece to be welded; 3 ensuring the positions of an electric arc and a laser beam, wherein the laser beam is perpendicularly irradiated to the surface of the work piece to be welded, an included angle between the electric arc and the laser beam is 15-60 DEG C, and the distance between the laser beam and the sharp end of a GMA electric arc welding wire is 2-6mm; 4 setting a welding technology parameter; and 5 performing the welding, wherein an electric arc welding gun is kept to be immovable when welding, and a laser beam-focused wielding gun swinging welds in the shape of 'S' The method is used for butt welding of a thick plate more than 10mm in national defense and civil use fields of shipbuilding, petroleum pipe lines, high-pressure vessels, fighting vehicles and nuclear devices, etc

Stainless steel or nickel sheet laser tailor-welding alignment clamping device and method

Abstract: The invention discloses a stainless steel or nickel sheet laser tailor-welding alignment clamping device and a method. The alignment clamping device comprises an XYZ three-dimensional translation RZ one-dimensional rotation motion mechanism, a video monitoring alignment regulating mechanism and a magnet pneumatic clamping mechanism, wherein the stainless steel or nickel sheet laser tailor-welding alignment clamping device can align and position sheets through the XYZ three-dimensional translation RZ one-dimensional rotation motion mechanism and the video monitoring alignment regulating mechanism, and then clamps and fixes the stainless steel or nickel sheets by the magnet pneumatic clamping mechanism to realize the laser tailor-welding of the stainless steel or nickel sheets. The invention can solve the problem of difficult welding of the stainless steel or nickel sheets smaller than 0.3mm in thickness in laser butt welding because the sheets are easy to deform owing to easy deformation property per se and thermal stress, and guarantees the quality of tailor-welded seams.

Nd:YAG laser welding of titanium alloys using a directed gas jet

Abstract: The increasing utilization of titanium alloys in the aerospace industry, a direct result of socioeconomic pressures, has created the need for a production process which can produce high quality near-net-shape titanium alloy components. Keyhole laser welding is a joining technology which could be utilized for this requirement. In general, when laser welding titanium alloys, a jet of inert gas, directed at the region of the laser beam/material interaction point is utilized to achieve the weld quality required. A statistical study has been performed in order to determine the optimum position and flow rate of this directed gas jet, with respect to reducing the weld metal porosity and optimizing the weld profile, for autogeneous Nd:YAG laser welding of 3.25 mm thickness Ti-2.5Cu and Ti-6Al-4V. As a result, butt welds have been reproducibly made with a quality that exceeds the most stringent aerospace weld quality criteria. High speed imaging and spectroscopic analysis of the welding process have revealed that,...