A New One-Sided Joining Process for Aluminum Alloys: Friction Stir Blind Riveting

Friction stir blind riveting is a new joining process for one-sided joining (compared with the two-sided access required for, for example, self-piercing riveting) of aluminum alloys, which eliminates the need to predrill a hole for rivet insertion. A blind rivet rotating at high speed is brought into contact with the workpieces, thereby generating frictional heat between the rivet and the workpiece, which softens the workpiece material and enables the rivet to be driven into the workpieces under reduced force. Once fully inserted, the blind rivet is upset using the internal mandrel (as in a conventional blind riveting process) to fasten the workpieces together. Our study showed that friction stir blind riveting process can be carried out over a wide range of operating parameters. The resulting joints show consistent strength under tensile load with minimal influence of changes in operating parameters. The robustness of the process against variations in operating conditions shows that the process can be carried out without high-end equipment and without requiring precise initial setup. It also suggests that the process is feasible for rapid joint fabrication in volume production. Further study revealed superior static and fatigue strength from the friction stir blind riveting process, when compared with conventional spot welding, which suggests potential for reduction in the number of joints required in a structure.

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Friction Stir Blind Riveting for Joining Dissimilar Cast Mg AM60 and Al Alloy Sheets

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4030156 ◽

2015 ◽

Vol 137 (5) ◽

Cited By ~ 19

Author(s):

Junying Min ◽

Jingjing Li ◽

Blair E. Carlson ◽

Yongqiang Li ◽

James F. Quinn ◽

...

Keyword(s):

Loading Condition ◽

Tensile Load ◽

Strengthening Mechanism ◽

Frictional Heat ◽

Process Window ◽

Al Alloy ◽

Forming Process ◽

Friction Stir ◽

Lap Shear ◽

Riveting Process

A new one-sided joining method, friction stirring blind riveting (FSBR) was successfully implemented to form lap-shear joints for dissimilar metals from pairs of 3.05 mm thick cast Mg AM60, rolled 1.5 mm thick Al AA6022, and extruded 3.15 mm thick Al AA6082 specimens. The concept of this process is riveting the two workpieces with reduced force under frictional heat and fastening the workpieces through blind riveting once the rivet is fully inserted. In this research, the process was experimentally analyzed and optimized for four joint combinations. It was demonstrated that switching the positions of Mg and Al alloy specimens has a significant effect on the process window and maximum tensile load of the joints. Three quality issues of the FSBR joints were observed and discussed. During tensile testing, the sheet closer to the rivet tail work-hardens due to tail forming process but has worse loading condition than the sheet closer to the rivet head. For AA6xxx sheets, precipitate hardening due to frictional heat is another strengthening mechanism in FSBR compared to the conventional riveting process, which leads to higher tensile loads in FSBR joints.

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Friction Self-Piercing Riveting (F-SPR) of AA6061-T6 to AZ31B

Volume 2B: Advanced Manufacturing ◽

10.1115/imece2013-64212 ◽

2013 ◽

Author(s):

YongBing Li ◽

ZeYu Wei ◽

YaTing Li ◽

ZhaoZhao Wang ◽

Xiaobo Zhu

Keyword(s):

Magnesium Alloys ◽

Spot Welding ◽

High Speed ◽

Dissimilar Materials ◽

Friction Stir Spot Welding ◽

Friction Stir ◽

Riveting Process ◽

Solid State Joining ◽

Joining Process ◽

Vehicle Bodies

Implementation of lightweight low-ductility materials such as aluminum alloys, magnesium alloys and composite materials has become urgently needed for automotive manufacturers to improve the competitiveness of their products. However, the hybrid use of these materials poses big challenges to joining processes. Self-piercing riveting (SPR) is currently the most popular technique for joining dissimilar materials and has been widely used in joining all-aluminum and multi-material vehicle bodies. However, in riveting magnesium alloys, cracks always occur for its low ductility. In this paper, a hybrid joining process named friction self-piercing riveting (F-SPR), which combines mechanical joining mechanism of SPR with solid-state joining mechanism of friction stir spot welding (FSSW) by making rivet rotating at high speed in riveting process, was proposed aiming at joining the low ductility materials. 1-mm-thick AA6061-T6 and 2-mm-thick AZ31B were used to validate the effectiveness of the F-SPR process. The results showed that the F-SPR process could significantly improve the rivetability of magnesium alloys, and greatly increase the joint strength, comparing with traditional SPR process.

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Friction Self-Piercing Riveting of Aluminum Alloy AA6061-T6 to Magnesium Alloy AZ31B

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4025421 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 43

Author(s):

YongBing Li ◽

ZeYu Wei ◽

ZhaoZhao Wang ◽

YaTing Li

Keyword(s):

Magnesium Alloys ◽

Spot Welding ◽

High Speed ◽

Dissimilar Materials ◽

Friction Stir ◽

Magnesium Alloy Az31b ◽

Riveting Process ◽

Solid State Joining ◽

Joining Process ◽

Vehicle Bodies

Implementation of lightweight low-ductility materials such as aluminum alloys, magnesium alloys and composite materials has become urgently needed for automotive manufacturers to improve the competitiveness of their products. However, hybrid use of these materials poses big challenges to traditional joining process. Self-piercing riveting (SPR) is currently the most popular technique for joining dissimilar materials and has been widely used in joining all-aluminum and multimaterial vehicle bodies. However, in riveting magnesium alloys, cracks always occur for its low ductility. In this paper, a hybrid joining process named friction self-piercing riveting (F-SPR), which combines mechanical joining mechanism of SPR with solid-state joining mechanism of friction stir spot welding (FSSW) by making rivet rotating at high speed in riveting process, was proposed aiming at joining the low-ductility materials. The effectiveness of the F-SPR process was validated via riveting 1 mm thick AA6061-T6 and 2 mm thick AZ31B. The results showed that the F-SPR process could significantly improve the rivetability of magnesium alloys, and greatly increase the joint strength, comparing with the traditional SPR process.

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Modeling of Friction Stir Welding of AL7075 Using Neural Networks

International Journal of Applied Evolutionary Computation ◽

10.4018/jaec.2012010104 ◽

2012 ◽

Vol 3 (1) ◽

pp. 66-79 ◽

Cited By ~ 1

Author(s):

Sasidhar Muttineni ◽

Pandu R. Vundavilli

Keyword(s):

Neural Network ◽

Mechanical Properties ◽

Neural Networks ◽

Friction Stir Welding ◽

Aluminum Alloys ◽

High Speed ◽

Welding Process ◽

High Speed Steel ◽

Operating Conditions ◽

Friction Stir

Friction stir welding (FSW) is a solid state welding process, which is used for the welding of aluminum alloys. It is important to note that the mechanical properties of the FSW process depends on various process parameters, such as spindle speed, feed rate and shoulder depth. Two different tool materials, such as High speed steel (HSS) and H13 are considered for the welding of Al 7075. The present paper deals with the modeling of FSW process using neural networks. A three layered feed forward neural network (NN) has been used to model the FSW of aluminum alloys. It is important to note that the connection weights and bias values of the NN are optimized with the help of a binary coded genetic algorithm (GA). The training of the NN with the help of GA is a time consuming process. Hence, offline training has been provided to optimize the connection weights and bias values of the neural network. Once, the training is over, the GA trained neural network will be used for online prediction of the mechanical properties of FSW process at different operating conditions.

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Characteristics of air entrainment during dynamic wetting failure along a planar substrate

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.110 ◽

2014 ◽

Vol 747 ◽

pp. 119-140 ◽

Cited By ~ 24

Author(s):

E. Vandre ◽

M. S. Carvalho ◽

S. Kumar

Keyword(s):

High Speed ◽

Water Solution ◽

Air Entrainment ◽

Dynamic Contact ◽

Operating Conditions ◽

Dynamic Wetting ◽

Glycerol Water ◽

Planar Substrate ◽

Wide Range ◽

Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

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A Study on the Deformation due to High Speed Processing of Aircraft Wing Structure

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.880.63 ◽

2021 ◽

Vol 880 ◽

pp. 63-68

Author(s):

Jihye An ◽

Hyunji Kim ◽

Dohyeon Kim ◽

Sangkyoo Nam ◽

Yunyoong Yoo ◽

...

Keyword(s):

Residual Stress ◽

High Speed ◽

Tensile Force ◽

Tensile Load ◽

Working Hours ◽

Frictional Heat ◽

Aviation Industry ◽

High Speed Machining ◽

Skilled Workers ◽

Processing Site

Residual stresses generated during high-speed machining of spoiler beams used in aircraft cause product deformation and dimensional mismatch, which increases the defect rate and leads to material waste. To overcome this problem, the processing site uses manual modification techniques that stretch part of the workpiece according to the experience of skilled workers. However, due to the nature of the aviation parts industry, there are no established methods for modification of product shapes and parts. Studying the modification process would allow for increased productivity, such as shorter working hours, throughout the aviation industry. In this study, a method of predicting residual stress due to frictional heat generated during high-speed machining and applying a tensile force to a model deformed by residual stress was used to modify the product. Our analysis showed that a degree of deformation similar to the measured value was produced, and that the product was modified by applying a tensile load.

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Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

Volume 7B: Structures and Dynamics ◽

10.1115/gt2017-65040 ◽

2017 ◽

Cited By ~ 1

Author(s):

B. R. Nichols ◽

R. L. Fittro ◽

C. P. Goyne

Keyword(s):

Flow Rate ◽

High Speed ◽

Operating Conditions ◽

System Stability ◽

Supporting Evidence ◽

Test Rig ◽

Flow Rates ◽

Oil Supply ◽

Bending Mode ◽

Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

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Assessment of engine combustion network recommendations for measurement of ignition and lift-off length

International Journal of Engine Research ◽

10.1177/1468087420922646 ◽

2020 ◽

pp. 146808742092264

Author(s):

Boni F Yraguen ◽

Farzad Poursadegh ◽

Caroline L Genzale

Keyword(s):

Ignition Delay ◽

High Speed ◽

Operating Conditions ◽

Bias Error ◽

Ambient Conditions ◽

Intensity Histogram ◽

Wide Range ◽

Engine Combustion ◽

Length Measurements ◽

Lift Off

The engine combustion network recommends two different imaging-based diagnostics for the measurement of diesel spray ignition delay and lift-off length, respectively. To measure ignition delay, high-speed imaging of broadband luminosity, spectrally filtered to limit collected wavelengths below 600 nm, is recommended. This diagnostic is often referred to as broadband natural luminosity. For lift-off length measurements, the engine combustion network recommends imaging of OH* chemiluminescence. This diagnostic requires using an image-intensified camera to detect narrowly filtered light around 310 nm. Alternatively, it has been shown that the lift-off length can be measured using broadband natural luminosity, avoiding the need for an intensifier and ultraviolet-transmitting optics. However, care is needed in the collection and processing of this diagnostic to accurately isolate the chemiluminescence signal. Particularly, standard intensity thresholding techniques are not sufficient for isolating the chemiluminescence signal in broadband natural luminosity images. Thus, an intensity-histogram-based thresholding method is introduced. This article assesses the feasibility and practicality of measuring lift-off length using broadband natural luminosity using a detailed comparison to OH* chemiluminescence measurements. It is shown that lift-off length measurements using broadband natural luminosity are prone to user bias error in the optical setup and data processing, especially under moderate- to high-sooting conditions. We conclude that while OH* imaging provides the most reliable and accurate measurement of lift-off length at a wide range of ambient conditions, an intensity-histogram analysis can help discriminate the high-temperature chemiluminescence signal from others in a broadband natural luminosity image at higher-sooting operating conditions than demonstrated in current literature.

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Cyclic NO2:NOx ratio from a diesel engine undergoing transient load steps

International Journal of Engine Research ◽

10.1177/1468087419833202 ◽

2019 ◽

Vol 22 (1) ◽

pp. 284-294 ◽

Cited By ~ 5

Author(s):

FCP Leach ◽

MH Davy ◽

MS Peckham

Keyword(s):

Diesel Engine ◽

High Speed ◽

Exhaust Gas Recirculation ◽

Operating Conditions ◽

Formation Mechanisms ◽

Exhaust Gas ◽

Work Cycle ◽

Wide Range ◽

Gas Recirculation ◽

Aftertreatment Systems

As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO2/NOx ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NOx aftertreatment systems. In this work, cycle-to-cycle NO and NOx emissions have been measured using a Cambustion CLD500, and the cyclic NO2/NOx ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NOx, and hence NO2/NOx ratio, are instantaneous upon a step change in engine load. NO2/NOx ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO2 than have been previously reported in the literature are observed.

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