Experimental and theoretical analysis of friction stir welding of Al–Cu joints

This paper presents a study of friction stir welding of aluminium and copper using experimental work and theoretical modelling. The 5083-H116 aluminium alloy and pure copper were successfully friction-stir-welded by offsetting the pin to the aluminium side and controlling the FSW parameters. A theoretical analysis is presented along with key findings. The process temperatures are predicted analytically using the inverse heat transfer method and correlated with experimental measurements. The temperature distribution in the immediate surroundings of the weld zone is investigated together with the microstructures and mechanical properties of the joint. This was supported by a finite element analysis using COMSOL Multiphysics. In this study, two rotational speeds were used and a range of offsets was applied to the pin. The microstructure analysis of the joints was undertaken. This revealed some particles of Cu inclusion in the nugget zone. The energy dispersive spectroscopy showed a higher diffusion rate of aluminium towards the interface while copper maintained a straight base line.     

Angular distortion analysis of the multipass welding process on combined joint types using thermo-elastic–plastic FEM with experimental validation

In this research, the capability of the multipass welding advisor (MWA) is to be evaluated in analyzing the angular distortion that is induced by gas metal arc welding (GMAW) process used to join a combination of butt and T-joint with thickness of 9 mm. The MWA in SysWeld 2010 is applied to develop and compare 2D/3D finite element analysis (FEA) based on the thermal elastic–plastic approach with low manganese carbon steel S355J2G3 as parent and weld material. For this simulation, the heat source of GMAW follows the Goldak's double ellipsoid model that is available within the FEA code. Detailed procedures of MPA are presented throughout this study followed with a comparison between 2D and 3D results of distortion and computational time on the combined types. To validate the simulation results, a series of experiments was conducted on low carbon steel using robotic welding process, GMAW power source with shielding gas composition of Ar (80 %)/CO₂ (20 %), and both-sided clamping method. It was established that the results of 3D simulation and experiments showed acceptable accuracy, while 2D results offers a fast solution analysis time in estimating distortion trend.     

Study of ultrasonic vibrations’ effect on friction stir welding

In this paper, effect of ultrasonic vibrations on friction stir welding (FSW) is studied. Ultrasonic vibrations were employed on the tool in pin direction (perpendicular to the welding direction). To do this study, a vibration tool was designed by Abaqus software in a way to have a longitudinal frequency about 20 kHz and was then manufactured and assembled with an ultrasonic transducer and was controlled using an ultrasonic generator to oscillate ultrasonically with a peak-to-peak amplitude of 10 μm. After preparation of experimental setup, some experiments were performed on AA6061-T6 as a work material, and the effect of ultrasonic vibrations on force, temperature, tensile strength, and hardness was investigated in FSW. Based on the achieved results, ultrasonic vibrations can decrease force and increase temperature in FSW.     

New friction welding process for pipeline girth welds—welding time optimisation

CAD/CAM systems are the important interface for automating manufacturing processes to accommodate the varying market demands. However, they are often operated in an isolated environment and are unable to communicate with each other. Rapid development and enhancement of the network technology had made it possible for manufacturing processes to be implemented in a distributed environment. The purpose of this study is to develop a dispersed networked multi-axis surface manufacturing system. The proposed research uses the Integrated Definition for Function Modelling (IDEF0) methodology to analyze the manufacturing activities and adopts the Common Object Request Broker Architecture (CORBA) standard as the infrastructure of software components. Using IDEF0, the manufacturing activities can be analyzed and represented as a hierarchical and structural functional model. The developed system has the “plug-and-play” capability and can be integrated with other development teams to achieve information sharing. On-line test of the prototype system has been implemented collaboratively by three development teams and the effectiveness of the developed system has also been confirmed. The developed system has successfully integrated resources of different locations through a network and can effectively reduce the product development and manufacturing time, thus enhancing the global competitiveness of the industry.     

Experimental analysis of high temperature capacitance variance of MLCC

研究了多层片式瓷介电容器(MLCC)受高温时的容值变化。结合MLCC的特点,提出了其在引信中的使用方法,同时,讨论了温度稳定性对电子产品设计的影响。实验结果表明,低频MLCC的容值受温度影响较大。     

Experimental studies on optimization of process parameters and finite element analysis of temperature and stress distribution on joining of Al�CAl and Al�CAl2O3 using ultrasonic welding

This study is carried out to optimize the process parameters like weld time, weld pressure, and amplitude of vibration to maximize the weld strength in Al?CAl welding using Taguchi??s design of experiments methodology. Experiments are conducted using 0.3-mm thick pieces of aluminum, and the temperature generated at the weld interface and the weld strength for all the specimens are measured. Also, a finite element model is developed that is capable of predicting the interface temperature and stress distribution during welding. Further, a preliminary study on the joining of alumina to aluminum is also carried out, and the finite element models of temperature and stress distribution during welding are simulated. Results of experimental work and FEM studies are compared and found to be in good agreement.     

Analysis of weld pool dynamic during stationary laser–MIG hybrid welding

A mathematical model was established to simulate the weld pool development and dynamic process in stationary laser–metal inert gas (MIG) hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow pattern; moreover, typical phenomena of MIG welding such as filler droplets impinging weld pool, electromagnetic force in the weld pool, and typical phenomena of laser beam welding such as recoil pressure, inverse Bremsstrahlung absorption, and Fresnel absorption were all considered in the model. The laser beam and arc couple effect was introduced into this model by the plasma width during hybrid welding. Transient weld pool shape and complicated liquid metal velocity distribution from two kinds of weld pool to a unified weld pool were calculated. Furthermore, the simulated weld bead geometries were in good agreement with experimental measurement.     

Experimental research and analysis of three-finger micro-tweezers

1Introduction Withthedevelopmentofmicro electro me chanicalstructure(MEMS),grasping,manipu latingandassemblingofmicroobjectsarequite fascinating.Newtoolsforthesepurposeshave beendevelopedrapidly.However,mostofthese researchesarefocusedontwo fingermicro tweezers[1～3].Thestabilityandapplicationof two fingermicro tweezersinmanipulationand assemblyareverylimitedingraspingsphere,co lumnarorcomplicatedmicroobjects[4].Inorder tograspparticlesmoresteadily,carbonfibers areusedtocreatethethreefingers…     

Experimental investigation on submerged arc welding of Cr–Mo–V steel

Welding aspects of a high-quality Cr–Mo–V steel are investigated in the present work. Cr–Mo–V steel can be suggested as a best choice for fabrication of pressure vessels to be operated in high-temperature operating conditions. Welding of this group of steel demands very critical attention on the parameters setting of chosen welding process. Only a few researchers had carried out research on the optimization aspects of the submerged arc welding of Cr–Mo–V steel. In the present work, complete experimental analysis is carried out on the submerged arc welding of Cr–Mo–V steel. The important input process parameters considered are welding current, voltage, welding speed, and wire feed. The effect of these input parameters is studied on various responses related to weld bead geometry and few mechanical properties. Taguchi’s L₉ orthogonal array is used for design of experiment and the mathematical models are developed for the responses using MINITAB 15 software. The models developed are validated by conducting more experiments. Optimised parameter setting is also obtained by using a recently developed teaching–learning-based optimization algorithm.     

Calibration of dynamic tool–workpiece interface temperature measurement during friction stir welding

The objective of this work is to accurately measure the transient temperatures at the tool–workpiece interface during friction stir welding (FSW) using thermocouples that are embedded in the tool. Temperature sensors embedded in the friction stir (FS) tool provide a non-consumable localized temperature measurement capability that is crucial for process research, development, and control. A modification of the ASTM E-1461 standard for measuring thermal diffusivity with pulses of heat flux is proposed for calibrating the transient response of temperature sensors located near the surface of the FS tool. These tests enable the calculation of each sensor’s time constant, which are used in one-dimensional analytical models of the dynamic response to calculate the true interface temperature. Time constants between 21 and 43 ms are measured for 0.25-mm-diameter, sheathed thermocouples located at the FS tool surface.     

Parameter optimization and mechanism of laser–arc hybrid welding of dissimilar Al alloy and stainless steel

Laser–cold metal transfer arc hybrid welding of 6061 Al alloy and AISI304 stainless steel (304SS) was carried out. Bead morphologies and intermetallic compound (IMC) layer characterizations of the joints were studied in detail. The optimal parameter range for accepted bead appearances (OPRBA) without surface and interface defects was obtained, and the growth mechanism of the IMC layer was summarized. The results showed that the nonuniformity in the thickness and shape along the fusion zone/304SS interface from the top surface to the bottom increases with increasing heat input and is more sensitive to laser power because the interface temperature is dominated by a high-temperature laser keyhole throughout the molten pool. As the welding parameters are within the OPRBA and the heat input is within the range of 80–110 J/mm, the joints are stronger than 130 MPa and the corresponding IMC layer thickness is at the range of 3–6.5 μm. The kinetic analysis showed that a controlling interface temperature no more than 1,120 °C may limit the growth of the IMC layer.     

Numerical modeling of heat transfer and fluid flow in hybrid laser–TIG welding of aluminum alloy AA6082

This paper describes a three-dimensional numerical model based on finite volume method to simulate heat transfer and fluid flow in laser–tungsten inert gas (TIG) hybrid welding process. To simplify the model and reduce the calculation time, keyhole dynamics are not considered; instead, a new modified volumetric heat source model is presented for the laser source to take into account the effect of the keyhole on the heat transfer into the workpiece. Due to the presence of arc current, an appropriate electromagnetic model based on the Maxwell equations are also solved to calculate electromagnetic forces in the weld pool. The results of computer simulation, including temperature, current density, electromagnetic, and melted material velocity field, are presented here. Furthermore, several dimensionless numbers are employed to recognize the importance of fluid flow driving forces in the weld pool. It is deduced that the fluid flow has an important effect on the weld pool shape. It is also founded that among the driving forces, Marangoni force is dominant fluid force in the weld pool. Besides, calculated results of hybrid welding process are compared with those of TIG and laser welding processes. The weld pool depth is relatively the same, but the width of the weld pool is highly larger in hybrid welding than lone laser welding. Eventually, the presented model is validated by comparison between calculated and experimental weld pool shape. It is founded that there is a good agreement as the capability of this model can be proved.     

Effect of welding seam spacing and relative bar wall thickness of bus framework on joint’s local mechanical property

Now the researches concerning integral bus mainly focused on design and analysis of overall mechanical property of bus body,and paid little attention to characteristic of local structures,such as joint,plug welding hole,and bolt connection point,etc.So there is much blindness on the design of local connecting structure.Since integral bus body structure cancels large section longitudinal beam,and uses framework made by welding small section bars together as principal part to bear the whole load when the vehicle works,there are many joints receiving high load in the body structure,and local stress concentration can not be avoided.Under such circumstances,by adopting beam-shell mixed model based on super element technique,and selecting a joint commonly used by bus sidewall,the rule of the effect of bar joint’s welding seam spacing on joint’s local mechanical property is investigated in this paper,and the investigating results show that joints have minimum stress concentration with welding seam spacing of 8 mm.To learn whether the above rule is affected by relative bar wall thickness,many groups of bars with different relative bar wall thicknesses are studied experimentally,and the experimental results show that the joints local stress levels vary with different relative bar wall thicknesses,but the rule of the effect of bar joint’s welding seam spacing on joint’s local stress level remains the same.The research is significant for local structure design of bus joint in the future.     

Behavior of the plasma characteristic and droplet transfer in CO2 laser–GMAW-P hybrid welding

The plasma behavior and metal transfer in CO₂ laser?+?GMAW-P hybrid welding have been investigated. A 650 nm laser, in conjunction with the shadow graph technique, is used to observe the metal transfer process. The effect of the mutual distance and laser power on the metal transfer has been discussed. The results indicate that the laser-induced plasma plume have a significant impact to the arc shape, resistance, electrode melting, droplet formation, detachment, and impingement onto the workpiece. The laser-induced plasma changes the conductive path and forces affecting on the droplet. High laser power and short distance between laser beam and arc (DLA) reduce the pulse base time (PB) of the voltage of phase, increase the droplet detachment time (PD) and the pulse current time (PP) of the voltage of phase, and it also lead to an upward and inward force near the bottom of the droplet. As a consequence, the droplet formation time is increased, and eventually an off-axis droplet phenomenon is deduced. The vapor jet force induced by the the keyhole plasma acts on the droplet as a retention force; this force decreases when the DLA becomes larger and increases when the laser power becomes higher. The observation may help in understanding the weld characteristics with respect to variation in mutual distance and laser power which may be beneficial in using the main process parameters to produce desired weld quality.     

Design and dynamic analysis of single-axis integrated inertia measurement device

The structure and measurement theory of a single-axis integrated inertia measurement device are discussed in this paper.The acceleration and angle velocity can be detected by the proposed sensor at the same time.The kinetic model of the device is also established.In addition,the signal generation of the single-axis integrated inertiameasurement device is analyzed and simulated.The results of the model are consistent with simulation result.     

Digital in-line holography for the analysis of Bénard-convection

Digital in-line holography (Skarman et al., Flow Measurement and Instrumentation 7 (1) (1996) 1–6) represents a novel optical method for flow and temperature measurements of transparent liquid media. A CCD-camera is used to record digital holograms of tracer particles in a fluid volume. The procedure is based on the phase-shift method. Algorithms for computational focusing on individual particles in three dimensions have been developed. As an additional benefit the holographic recording contains interferometric information about the optical path length which in turn enables the calculation of the density and temperature profile of the flow.     

Performance analysis of wire electrochemical turning process��RSM approach

Electrochemical machining (ECM) has become one of the most widely spread techniques of the non-traditional processes. The main problem of ECM is that of choosing the correct working parameters to attain a high degree of accuracy under fine surface finish conditions. Recently, electrochemical turning has gained attention as a finishing process. By feeding a shaped tool into a rotating workpiece, axially symmetric turned parts can be manufactured. In this way, large symmetric workpiece can be made with small tools. This paper discusses the feasibility of using a wire as a tool in electrochemical turning process (WECT). The present study measures the performance criteria of the WECT process through investigating the effect of working parameters, namely, applied voltage, wire feed rate, wire diameter, workpiece rotational speed, and overlap distance, on metal removal rate, surface roughness, and roundness error. The experimental results are statistically analyzed and modeled through response surface methodology. The regression model adequacies are checked using analysis of variance. Furthermore, the optimal combination of these parameters has been evaluated to maximize metal removal rate and minimize surface roughness and roundness error. The study reveals the ability of using a wire as a tool in WECT and its productivity; the shape errors can be controlled through the mentioned input parameters. The results show that the increase of wire feed rate enhances the productivity of the process and improves both surface quality and roundness error. Also, the increase of rotational speed improves both the productivity of the process and geometrical error of the produced parts.     

Vibration modeling and analysis of wire during the WEDM process

During the wire electrical discharge machining (WEDM) process, the vibrations of the wire generated by the gap force is the main cause of imprecision. To achieve more precise results with better accuracy, understanding of the vibration management of the wire is essential. In this article, the wire’s vibration behavior is introduced briefly, followed by an exploration of an equation, derived from Hamilton’s principle, which expresses the vibration of a wire moving axially. This equation is presented under some simplified assumptions. In addition, the relationship between the maximum amplitude of the vibration and the main relative variables is presented. The solution demonstrates that a thicker workpiece results in a larger amplitude of vibration, yet the axial speed of the wire has no impact on the maximum amplitude.