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With the advances of industry 4.0, augmented reality (AR) devices are being deployed across the manufacturing sector to enhance worker perception and efficiency. AR is often used to deliver spatially relevant work instructions on mobile devices for maintenance procedures on the factory floor. In these situations, workers use their mobile devices to view instructions in the form of 3D animations and annotations that directly overlay the equipment being maintained. Workers then follow the AR instructions and must ultimately rely on their own judgement and knowledge of the procedure as they progress from step to step. An AR assistant that could validate each stage of the procedure in real time and provide the worker with feedback on any observed errors would ensure that each maintenance procedure is completed successfully. This work presents a mobile, quality inspection system for AR maintenance procedures that is capable of assessing the maintenance task in real time. The system is designed for deployment on handheld mobile devices and can thus manage the challenges inherent to performing quality inspection with a non-fixed vision system. This work enumerates four essential qualities of mobile quality inspection tools and outlines some of the challenges encountered during the development of such a system. In the end, testing established that the system could provide adequate assistance for capturing inspection images, accurately process the captured images using machine vision, and generate detailed feedback from the quality inspection in a timely manner.

Given recent advancements in technology and recognizing the evolution of smart manufacturing, the implementation of digital twins for factories and processes is becoming more common and more useful. Additionally, expansion in connectivity, growth in data storage, and the implementation of the Industrial Internet of Things (IIoT) allow for greater opportunities not only with digital twins but closed loop analytics. Discrete Event Simulation (DES) has been used to create digital twins and in some instances fitted with live connections to closely monitor factory operations. However, the benefits of a connected digital twin are not easily quantified. Therefore, a test bed demonstration factory was used, which implements smart technologies, to evaluate the effectiveness of a closed-loop digital twin in identifying and reacting to trends in production. This involves a digital twin of a factory process using DES. Although traditional DES is typically modeled using historical data, a DES system was developed which made use of live data with embedded machine learning to improve predictions. This model had live data updated directly to the DES model without user interaction, creating an adaptive and dynamic model. It was found that this DES with machine learning capabilities typically provided more accurate predictions of future performance and unforeseen near future problems when compared to the predictions of a traditional DES using only historic data, resulting in smarter decisions and implementation of more timely solutions.

Friction stir welds were manufactured from aluminum alloy 2024-T3 and 7075-T6 workpieces under temperature control. Three control conditions, high-temperature, low-temperature and uncontrolled, were selected for each alloy based on the precipitation/dissolution temperatures of their strengthening phases, and the welds were characterized through positron annihilation lifetime spectroscopy and mechanical testing. For 2024, positron lifetimes and numerical simulation of the temperature profiles demonstrated that the S phase dissolution temperature was not achieved for any of the control conditions and hardness recovery upon cooling did not occur; however, for the low-temperature control (410°C), the S phase precipitated adjacent to the weld zone with the least extent of overaging, yielding the highest tensile strength of the three conditions. For 7075, dissolution of the η phase did not occur for the low-temperature (390°C) and the high-temperature (430°C) control conditions, and the low-temperature control produced the highest tensile strength due to the lesser degree of overaging of the strengthening phase. The uncontrolled condition for 7075, however, did achieve temperatures capable of dissolving the η phase, but due to the slow natural aging kinetics of 7075, a hardness recovery was not observed within the timeframe of this investigation.

With the growth of Industry 4.0 in recent years, Augmented Reality (AR) technologies are changing the way operators work by increasing their efficiency and operational performance. A common use of AR is providing operators helpful work instructions for assembly by presenting relevant digital information in the context of the physical environment. These AR experiences can be viewed via several devices such as mobile, wearable, and stationary devices, each being useful for different applications. While in the experience, instructions are provided by means of 3D animation, text, images, and interactive buttons, all of which are directly overlaid onto the physical product or equipment being worked on. This work presents a closed-loop, enterprise connected, AR system for post end Printed Circuit Board (PCB) assembly work instructions. The system is designed to work with a stationary device, allows for varying types of PCB”s, provides overlaid instruction, and logs important information to an enterprise system, such as overall cycle time, step cycle time, number of errors, type of error, and who performed the assembly. A comparison was made for single cell manual assembly PCB work instructions using both an Industry 4.0 driven system and a more traditional manufacturing system which used packets, tracers, Manufacturing Execution System (MES), and PDF instructions. Discovered benefits of an enterprise connected AR system included increased throughput and utilization, improved communication between operators and support, reduced overtime costs, reduced defects, reduced non-value-added secondary inspections, nearly 50% increase in ergonomics, reduced labor due to rework, and improved corrective actions due to granularity between steps compared to total operation. This AR driven solution transformed the single cell manual assembly to be more informed, make better decisions, and help operator productivity.

With the developments of Industry 4.0, data analytics solutions and their applications have become more prevalent in the manufacturing industry. Currently, the typical software architecture supporting these solutions is modular, using separate software for data collection, storage, analytics, and visualization. The integration and maintenance of such a solution requires the expertise of an information technology team, making implementation more challenging for small manufacturing enterprises. To allow small manufacturing enterprises to feasibly obtain the benefits of Industry 4.0 data analytics, a full-stack data analytics framework is presented, and its performance evaluated as applied in the common industrial analytics scenario of predictive maintenance. The predictive maintenance approach was achieved by using a full-stack data analytics framework comprised of the PTC Inc. Thingworx software suite. When deployed on a lab-scale factory, there was a significant increase in factory uptime in comparison with both preventive and reactive maintenance approaches. The predictive maintenance approach simultaneously eliminated unexpected breakdowns and extended the uptime periods of the lab-scale factory. This research concluded that similar or better results may be obtained in actual factory settings, since the only source of error on predictions in the testing scenario would not be present in real world scenarios. An analysis of the effect of downtime period durations and discussion on the cost of reactive maintenance and associated breakdowns is also presented.

As automotive designs add more aluminum to lightweight their vehicles, friction stir welding (FSW) will likely become a principal joining process in the industry. FSW is a solid-state joining process which avoids many of the traditional problems of welding aluminum alloys such as hot cracking, porosity and solidification shrinkage. These attributes enable high preforming friction stir welded joints of cast, 5XXX, 6XXX, 7XXX or mixed aluminum alloy combinations. Although FSW technologies have advanced to support high volume applications and have been applied in current automotive parts, its inability for nondestructive evaluation (NDE) increases the cost to manufacture friction stir welded parts. Current state of the art NDE methods for FSW are either ultrasound or radiographic technologies which add complexity to manufacturing lines and additional costs to FSW production. Many have researched ways to reduce NDE costs by using measured forces of the FSW process. These methods have included trained neural networks (NN) that result in accurate defect predictions that can be applied in an industrial setting. Although NN provide an alternative solution to traditional NDE methods, they require large amounts of training and can only inspect welds that share exact welding parameters and machinery that were included in the training. An ideal FSW NDE method would reduce costs and be able to be applied on multiple welding machines and with a variety of parameters. The cost of a cited generalized force based stochastic NDE method in an industrial setting will be validated by an automotive production example here in.

Refill Friction Stir Spot Welding (RFSSW) has demonstrated capability in joining thin sheets of aluminum with dissimilar thickness, alloy, and composition. The process remains to be implemented on a wide scale in the automotive and aerospace industries, partially due to the relatively short number of welds producible by a toolset, prior to needing cleaning. In the following work, an investigation was conducted to better understand this limitation. First, the effective tool life of a steel toolset was quantified. Experiments showed that less than 60 consecutive welds could be made before the toolset seized and required cleaning. To better understand the conditions contributing so such a short tool life, thermocouples were used in subsequent experiments, to measure the temperatures achieved at various locations in the weld. Peak weld temperature increased with longer cycle times and decreased with shorter cycle times. During the experiments, it was noted that weld temperatures in excess of 500 °C were observed at weld center. At these high temperatures, the authors anticipate that intermetallic compounds (IMCs) are able to grow on tool surfaces. A rough, existing model of IMC growth in an Fe-Al system predicted IMC growth on the same order of magnitude of the tool clearances, supporting the anticipation that IMC growth is a factor in the observed, short tool life between cleanings. Following this analysis, future evaluation of less re-active tool materials is recommended.

The formability of aluminum alloy 5754-O tailor-welded blanks prepared by friction stir welding was studied experimentally. The strain evolution and deformation during limiting dome height experiments were studied using digital image correlation and the ARAMIS software. The influence of the sheet thickness of the base materials on the punch loading, fracture strain and formability were investigated experimentally. It was found that the punch loading, fracture strain and limiting dome height values increase with the increasing sheet thickness of the base materials. A linear relationship between the limiting dome height value and the sheet thickness was demonstrated. An increase of 16.8% in the fracture strain of aluminum tailor-welded blanks was observed for an increase of 36% in sheet thickness. This paper provides a methodology for experimentally determining the forming limits of aluminum alloy tailor-welded blanks accurately.

Friction stir welding (FSW) is an advantageous solid-state joining process, suitable for many hard to weld materials in the energy, aerospace, naval, and automotive industries. Precipitation strengthened alloys, specifically 2XXX and 7XXX series aluminum alloys, are often joined by FSW to protect the strength of the materials and to avoid cracking. To maximize the strength of FSW joints in these precipitation hardened alloys, the thermal input affect must be better understood. The authors hypothesised that controlling the welding temperature under the dissolution temperature would result in stronger joints. To test the main hypothesis single alloy friction stir “butt” welds were produced, from aluminum 2024-T351 and 7075-T651 alloys, and tensile tested. Spindle speed proportional–integral–derivative (PID) temperature control was implemented to achieve sub-dissolution welding temperatures. This preliminary study will supply additional research to better understand the resulting microstructure, weld properties of sub-dissolution FSW. In addition, a numerical simulation to represent the temperature distribution will be built. Then optimized FSW temperatures could be predicted and tested in these alloys.

With more than a decade of research and development documenting both the benefits and the challenges of refill friction stir spot welding (RFSSW), we see remarkedly few industrial applications that have moved to full implementation. Two major challenges have been recognized that are currently impeding further adoption; namely, cycle time and tool life. While these two challenges are not mutually exclusive, the focus of the current work will be to contest reported trends that claim reducing cycle time below 2 s has a deleterious effect on weld properties. Recently published work challenged this trend for RFSSW of a work-hardenable AA5052-H36, where weld times were reported as low as 800 ms (Larsen and Hovanski in Reducing cycle times of refill friction stir spot welding in automotive aluminum alloys, SAE International, 2020). While this study demonstrated that machine capabilities drive reduction in weld cycle time without a commensurate reduction in weld properties, the focus was on demonstrating these changes for a work-hardenable alloy rather than a precipitation-hardened alloy. As such, the current work will demonstrate that a similar reduction in cycle time may be realized in AA7075-T6.

This research used a discrete event simulation to create data on a shipment receiving process instead of using historical records on the process. The simulation was used to create records with diff...

Under tensile shear loading, fracture modes of dissimilar lap welds produced by friction stir scribe technology were studied. Three fracture modes were observed. For zone A fracture, the initial cr...

Considerable progress has been achieved in friction stir welding (FSW) of steels in every aspect of tool fabrication, microstructure control and properties evaluation in the past two decades. With the development of reliable welding tools and precise control systems, FSW of steels has reached a new level of technical maturity. High-quality, long welds can be produced in many engineering steels. Compared to traditional fusion welding, FSW exhibits unique advantages producing joints with better properties. As a result of active control of the welding temperature and/or cooling rate, FSW has the capability of fabricating steel joints with excellent toughness and strength. For example, unfavorable phase transformations that usually occur during traditional welding can be avoided and favorable phase fractions in advanced steels can be maintained in the weld zone thus avoiding the typical property degradations associated with fusion welding. If phase transformations do occur during FSW of thick steels, optimization of microstructure and properties can be attained by controlling the heat input and post-weld cooling rate.

Friction stir welding (FSW) is a cost-effective and high-quality joining process for aluminum alloys (especially heat-treatable alloys) that is historically operated at lower joining speeds (up to hundreds of millimeters per minute). In this study, we present a microstructural analysis of friction stir welded AA7075-T6 blanks with high welding speeds up to 3 M/min. Textures, microstructures, mechanical properties, and weld quality are analyzed using TEM, EBSD, metallographic imaging, and Vickers hardness. The higher welding speed results in narrower, stronger heat-affected zones (HAZs) and also higher hardness in the nugget zones. The material flow direction in the nugget zone is found to be leaning towards the welding direction as the welding speed increases. Results are coupled with welding parameters and thermal history to aid in the understanding of the complex material flow and texture gradients within the welds in an effort to optimize welding parameters for high-speed processing.

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the ro...

One challenge in adapting welding processes to dissimilar material joining is the diversity of melting temperatures of the different materials. Although the use of mechanical fasteners and adhesives have mostly paved the way for near-term implementation of dissimilar material systems, these processes only accentuate the need for low-cost welding processes capable of impartially joining dissimilar material components regardless of alloy, properties, or melting temperature. Friction stir scribe technology was developed to overcome the challenges of joining dissimilar material components where melting temperatures vary greatly, and properties and/or chemistry are not compatible with more traditional welding processes. Although the friction stir scribe process is capable of joining dissimilar metals and metal/polymer systems, a more detailed evaluation of several aluminum/steel joints is presented herein to demonstrate the ability to both chemically and mechanically join dissimilar materials.

Heat input and high strain rate deformation during friction stir welding of aluminum and steel resulted in the diffusion-based formation of a FexAly intermetallic compound (IMC) layer. Compared with conventional friction stir welding tools, a friction stir scribe tool can reduce heat input significantly limiting the IMC layer thickness (~100–750 nm). Friction stir scribe joined lap joints fractured either through the welded interface or within the base aluminum alloy on the loading side, depending on IMC layer thickness during tensile lap shear testing. In addition, a modified effective heat of formation model predicted that Al13Fe4 formed first at aluminum/steel interface and, during welding process, was substituted by Al5Fe2 with local silicon enrichment, which was verified via microstructural characterization. Keywords: Friction stir scribe technology, Dissimilar, Intermetallic, Thermodynamic, Kinetic

This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld zone and thermo-mechanically affected zones exhibited shear texture components; however, there were many textures that deviated from ideal simple shear. Factors affecting the microstructure which are characteristic of the friction stir welding process, such as post-recrystallization deformation and complex deformation induced by tool geometry were discussed as causes for deviation from simple shear textures.

The impact of a graded metallic spacer on the galvanic corrosion between magnesium and mild steel is investigated in this work using a COMSOL model based on a validated numerical model. A graded spacer of 4 mm thickness decreases the peak galvanic corrosion by 50% over a system without a spacer, and 37% over a system with an aluminum spacer. The impact of the electrochemical properties of spacer materials is also investigated.

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and they have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high volumes. While friction-stir welding (FSW) has been traditionally applied at linear velocities less than 1 m/min, high-volume production applications demand the process be extended to higher velocities more amenable to cost-sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low-to-moderate welding velocities do not directly translate to high-speed linear FSW. Therefore, to facilitate production of high-volume aluminum FSW components, parameters were developed with a minimum welding velocity of 3 m/min. With an emphasis on weld quality, welded blanks were evaluated for postweld formability using a combination of numerical and experimental methods. An evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum TWBs, which provided validation of the numerical and experimental analysis of laboratory-scale tests.

Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energy for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon–Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys' model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.

Friction stir welding has gained wide interest in industry and drawn large research attention due to its high level of automation and superior joint performance. In this study we further expand the welding parameters to be of magnitudes higher than those previously reported to lower the cost and enable high volume joint production. Sound butt-joints were produced with aluminum alloy 6111-T4 blanks with welding speeds up to 6000 mm/min. Tensile tests of the joint pieces show >97% joint efficiency in terms of ultimate tensile strength. The T4 natural aging and grain refinement is found to contribute to the superior joint properties. Electron backscatter diffraction (EBSD) analysis is used to qualitatively study the local shear texture inside the nugget zones of the welds. The shear texture result is a good indicator of the material flow directions in the nugget zones. The flow directions behind the rotation tool are found to be flattened towards the top surface of the workpiece when the welding speed is increased, suggesting intense material mixing and transportation along the longitudinal welding direction (WD).

Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11–14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge® software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within 4%, and the position of the joint interface to within 10%, of the experimental results.

High speed friction stir spot welding was applied to 1.2 mm thick DP 980 steel sheets under different welding conditions, using PCBN tools. The range of vertical feed rates used during welding was 2.5∼102 mm per minute, while the range of spindle speeds was 2500∼6000 rpm. Extended testing was carried out for five different sets of welding conditions, until tool failure. These welding conditions resulted in vertical welding loads of 3.6∼8.2 kN and lap shear tension failure loads of 8.9∼11.1 kN. PCBN tools were shown, in the best case, to provide lap shear tension failure loads at or above 9 kN for 900 spot welds, after which tool failure caused a rapid drop in joint strength. Joint strength was shown to be strongly correlated to bond area, which was measured from weld cross sections. Failure modes of the tested joints were a function of bond area and softening that occurred in the heat-affected zone.

A comparison of welding techniques was performed to determine the most effective method for producing aluminum tailor-welded blanks for high volume automotive applications. Aluminum sheet was joined with an emphasis on post weld formability, surface quality and weld speed. Comparative results from several laser based welding techniques along with friction stir welding are presented. The results of this study demonstrate a quantitative comparison of weld methodologies in preparing tailor-welded aluminum stampings for high volume production in the automotive industry. Evaluation of nearly a dozen welding variations ultimately led to down selecting a single process based on post-weld quality and performance.

High-speed friction stir welding provides an opportunity to enable high-volume aluminum joining, thus lowering the expense of the process. To better understand this important industrial process the properties of the welds must be fully characterized. In this study we examined the microstructures of AA7075 butt welds with welding speeds of 1, 2 and 3 m/min. The welds were also tested for their corrosion resistance in a diluted EXCO solution at room temperature. The welds with higher speeds had a smaller corrosion sensitive area along with smaller HAZs, but the nugget zone became more corrosion susceptible. Their microstructure features were used to explain the non-uniform corrosion behavior across the weld. Both constituent particles and precipitate distribution were altered by the friction stir process and resulted in an overall sensitized weld affected region compared to the base material.

Solid-state joining of thick section aluminum to steel plate has been achieved using a new process called friction stir dovetailing (FSD). In FSD, a custom designed pin tool is used to flow a lower melting point material (AA6061) into dovetail grooves machined into the surface of an underlying material that has a higher melting point (rolled homogeneous armor [RHA]). Repeating dovetails form a mechanical interlocking structure akin to metallic Velcro. In this study, 38.1 mm (1.5 in.) thick AA6061 was joined to 12.7 mm (0.5 in.) thick RHA plates. The effectiveness of FSD is demonstrated through tensile test data that shows specimens failing in the processed aluminum rather than at the joint interface. Numerical simulations that highlight the importance of optimizing dovetail geometry are presented. The effect of process parameters on joint strength and microstructure also are discussed.