Friction Stir Welding of Aluminum 6061-T6 and Multi-Purpose Copper 11000 Alloy

Friction Stir Welding (FSW) is a solid-state joining process invented by The Welding Institute (TWI, United Kingdom) in 1991 in partnership with the National Aeronautics Space Agency. The process is emerging as one of the preferred alternative methods to permanently join materials that are difficult to join with traditional fusion methods (e.g., MIG, TIG, etc.). The welding of various copper alloys to various aluminum alloys is of great interest to the nuclear industry and the electrical distribution industry. The very different melting points of these two alloys preclude traditional fusion welding. Since the pin tool is simultaneously rotating and traversing through the work piece, flow around the tool is asymmetrical. This has led to designating one side of the tool as advancing and the opposite side as retreating. On the advancing side of the weld, the tool has a tangential velocity in the same direction as the weld is being created. The retreating side of the weld tool is the opposite. It can be can expected that asymmetric heating and deformation will occur in the weld due to this advancing/retreating nature of the FSW pin tool. Although previous studies have been performed that have observed this asymmetric behavior in both similar and dissimilar materials, the resulting welds have been of a poor quality. Large statistical experiments were conducted locally to study the effects of tool geometry, process parameters, and material composition have upon the friction stir butt welding of aluminum alloy 6061-T6 to copper alloy 11000 using a modern conventional 3-axis CNC vertical mill. The research seeks to determine (1) which direction a dissimilar metal friction stir weld between aluminum and copper should be executed, (2) the optimal shoulder diameter to be used when friction stir welding aluminum and copper on a CNC mill, and (3) the addition of a third material to act as an aide. The extensive statistical interactions between these parameters is also documented. A weld schedule was developed that resulted in an ultimate tensile strength (UTS) surpassing (greater than 90% of the weaker, more ductile copper alloy UTS strength) what has been documented in the current literature despite the machine limitations of the CNC vertical mill. Proper optimization of the welding schedule developed may approach 100 percent of the basic copper 11000 properties across the welded zone into the aluminum 6061-T6 alloy.

Organization and Compaction of Composite Filler Material Using Acoustic Focusing

Carbon nanofibers in polymer-based composites reduce the electrical resistivity of the composite but can be up to 100 times more expensive than the bulk polymer. This work uses acoustic focusing to organize and compact carbon nanofibers in a mineral oil mixture. The result is a decrease in the composite electrical resistivity without an increase in the global volume fraction of the fibers in the composite and associated material cost. The composite consisted of Pyrograf PR-19-LHT carbon nanofibers mixed in light mineral oil at 1.6% volume fraction carbon nanofibers. The mixture was contained in a 1 cm × 1 cm × 4 cm glass cuvette. A PZT-4 piezoelectric transducer, epoxied to the external face of one of the sidewalls, generated the acoustic radiation forces in the container. A 1.179 MHz sinusoidal signal powered the transducer, producing a standing wave with 27 nodes and 13 antinodes in the container. A digital multimeter performed the 2-wire resistance measurement before, during and after focusing. Settling of the filler due to gravity resulted in an initial drop in the electrical resistance. Once the mixture reached steady state, toggling the signal power off and on also toggled the approximate electrical resistance between the 19.2 MOhms and 11.5 MOhms respectively. This work also presents a simple volume fraction model, which predicted that the focused resistance would be 34% of the unfocused value. In the experiment, acoustic focusing reduced the electrical resistance to 60% of the resistance in the unfocused mixture, demonstrating acoustic focusing as a method for reducing electrical conductivity within a composite.

Influence of Process Parameters on Electrochemical Micromachining of Nimonic 75 Alloy

Electrochemical micromachining process is one among the successful micromachining technique, which uses the electrochemical energy and is recognized for machining difficult-to-cut materials. One such material is Nimonic 75 alloy, which is used to make gas turbine components. In this study, an effort has been made to machine micro-hole profiles in Nimonic 75 with a thickness of 500 μm using two different electrolytes. A combination of sodium bromide, hydrofluoric acid and ethylene glycol has been chosen as the first electrolyte, while the second is a combination of sodium chloride and sodium nitrate. Solid tungsten carbide of diameter 500 μm is used as the tool in each case. For layout of experiments, Taguchi orthogonal array was chosen with following input parameters namely voltage, micro-tool feed rate and duty cycle. Performance characteristics such as material removal rate, overcut and conicity have been assessed for each electrolyte. Experimental results have shown that the first electrolyte yields lower values of overcut (OC) and conicity, whereas the second electrolyte gives higher material removal rate (MRR). Further, the optimal combinations of process parameters have been found by implementing the TOPSIS procedure and the results were found to be in good agreement with the experimental outcomes.

Modeling and Experimental Characterization of Viscoelastic 3D Printed Spring/Damper Systems

The development of flexible, viscoelastic materials for consumer 3D printers has provided the opportunity for a wide range of devices with damping behavior such as tuned vibration isolators to be innovatively developed and inexpensively manufactured. However, there is currently little information available about the dynamic behavior of these 3D printed materials necessary for modeling of dynamic behavior prior to print. In order to fully utilize these promising materials, a deeper understanding of the material properties, and the subsequent dynamic behavior is critical. This study evaluates the use of three different types of models: transient response, frequency response and hysteretic response to predict the dynamic behavior of viscoelastic 3D printed materials based on static and dynamic material properties. Models of viscoelastic materials are presented and verified experimentally using two 3D printable materials and two traditional viscoelastic materials. The experimental response of each of the materials shows agreement with the modeled behavior, and underscores the need for improved characterization of the dynamic properties of viscoelastic 3D printable materials.

Anisotropic Behavior of Aluminum Alloy 2024-Graphene Composites at Varying Strain Rates

In fabrication of high strength materials coupled with improved mechanical properties; focus on integration of multifunctional reinforcements are increasing along with novel processing methods. Single layer 2-D material Graphene are among one such novel material with huge aspect ratio, posse’s high strength. But the real challenge is processing and incorporation of these reinforcements with appropriate content in metals or its alloys matrix. Current research work focus to study the anisotropic behavior on addition of pristine Graphene/MWCNT and processing methods like ball milling under constant ball to powder precursor ratio (BPR) of AA 2024 nanocomposites. The extent change in aspect ratio, size of the nanoparticle mixtures during ball milling were analyzed under SEM and Raman spectroscopy. Thus obtained (ball milled) precursors are consolidated through vacuum hot press and hot extruded to get typical flat specimen at optimized processing parameters. XRD analysis, relative density and hardness measurement is done on extruded composites. Thus developed composites are subjected to study the anisotropic behavior at various orientations and strain rates (0.5, 1.0, 1.5 mm/min) using uniaxial tensile testing instrument and corresponding stress strains graphs were obtained. The fracture surfaces were characterized by scanning electron microscope (SEM) and its shows the nucleation of the dimple size are varies with increasing the strain rate and also deeper dimple size were noticed. Negative strain sensitivity were observed for the lower strain rate (0.1 and 0.3 mm/min) and positive strain sensitivity for higher strain rates. Microstructural anisotropy infers that AA2024-Graphene/MWCNT composites are sensitive to strain rate and shear type of failure is observed on increasing the strain rate.

Numerical Simulations of Thermal Transport in Random Porous Materials and Powder Systems Using the Smoothed Particle Hydrodynamics Method

A numerical method to solve thermal transport problems in powder bed systems and porous materials with finite thermal contact conductance at interfaces between individual powder particles or grains is developed based on the Smoothed Particle Hydrodynamics approach. The developed method is applied to study the effective thermal conductivity of two-dimensional random powder bed systems with binary distribution of powder particles radii. The effects of particle size distribution parameters, density parameter, and effective interface area between particles on the effective thermal conductivity are studied. It is found that at finite Biot number, which characterizes the ratio of the interfacial conductance to the conductance of the bulk powder material, the effective thermal conductivity of porous samples increases with increasing fraction of particles of larger size.

Microhardness and Microstructural Studies on Underwater Friction Stir Welding of 5052 Aluminum Alloy

As compared to normal Friction Stir Welding (FSW) joints, the Underwater Friction Stir Welding (UFSW) has been reported to be obtainable in consideration of enhancement in mechanical properties. A 5052-Aluminum Alloy welded joints using UFSW method with plate thickness of 6 mm were investigated, in turn to interpret the fundamental justification for enhancement in mechanical properties of material through UFSW. Differences in microstructural features and mechanical properties of the joints were examined and discussed in detail. The results indicate that underwater FSW has reported lower hardness value in the HAZ and higher hardness value in the intermediate of stir zone (SZ). The average hardness value of underwater FSW increases about 53% greater than its base material (BM), while 21% greater than the normal FSW. The maximum micro-hardness value was three times greater than its base material (BM), and the mechanical properties of underwater FSW joint is increased compared to the normal FSW joint. Besides, the evaluated void-area fraction division in the SZ of underwater FSW joint was reduced and about one-third of the base material (BM). The approximately estimated average size of the voids in SZ of underwater FSW also was reduced to as low as 0.00073 mm2, when compared to normal FSW and BM with approximately estimated average voids size of 0.0024 mm2 and 0.0039 mm2, simultaneously.

Analysis of the Effect of Open and Close Angle of Workpiece Surface on Contour Error

The machining of complicated surface is a hot spot in manufacturing industry in nowadays. The complicated surfaces should be machined with five-axis machine tools because of its geometric characteristics. In this paper, the characteristic of workpiece surface called open and close angle of surface is defined. The transition area from open angle to close angle will cause the twist and singularity of the surface. The twist mainly affects the principle errors of surface. And the singularity will cause the mutation of rotation axis movement and make an influence on the contour errors. To test the influence of the open and close angle on the contour error, a workpiece with special surface characteristics is designed. With the theoretical, simulational and experimental analyses, the influence law from the open and close angle is found out. The conclusion can be helpful for the tool trajectory planning.

An Internet-of-Things Based Framework for Collaborative Manufacturing

The exchange of data and information among collaborating partners and resources in a distributed manufacturing system assumes significance especially in today’s global economy. In recent years, Internet of Things (IoT) and Cyber Physical Systems (CPS) related practices and technologies have emerged as enablers of collaborative manufacturing and engineering practices. Smart technologies involving Virtual Reality and haptic based interactions are continuing to play an important role in concurrent engineering based methods in distributed contexts. The research presented in this paper explores the design of an IoT based framework for electronics manufacturing involving the use of VR based environments and Cloud computing technologies. The process domain of interest is electronics manufacturing with an emphasis on Surface Mount assembly of printed circuit boards (PCBs). The VR based assembly environment played a key role in this IoT framework as it supported Concurrent Engineering practices by enabling stakeholders in this manufacturing system context to obtain a better understanding of the manufacturing process design while providing ‘what if’ analysis capabilities for changing customer requirements. Another benefit of such VR based IoT frameworks is the potential of such 3D environments to provide effective training of assembly processes as well as facilitating better understanding of process design issues from distributed locations.

Machinability Analysis of Aluminum Alloy-Graphene Metal Matrix Composites Using Uncoated and DLC-Coated Carbide Insert

Metal Matrix Composites (MMCs) based on Aluminum Alloys 2024, 6061 and 7075 reinforced with Graphene was fabricated using powder metallurgy process followed by hot extrusion process. The extruded samples were used for conducting the turning experiments to evaluate the machinability of the developed composites. Turning experiments were conducted in ACE Micromatic made CNC lathe as per the Design of Experiments (DOE) designed using L18 Taguchi’s mixed orthogonal array. Uncoated and DLC coated carbide inserts, along with three levels of cutting speeds, feed rates and depths of cut were considered for the turning experiments. During the experiments the cutting force generated was recorded “online” and subsequent to the experimentation the surface roughness generated on the work piece and the surface hardness for every trial were recorded. The influence of the cutting tool material and other cutting parameters on the machinability of composites was analyzed using ANOVA. The microstructural observation on the surface of the machined specimen reveals the detachment of reinforcement materials from the composite and their impact of the surface quality.