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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1938

The Increase in Frictional Resistance Caused by Various Types of Rivet Heads as Determined by Tests of Planing Surfaces

The increase in the frictional resistance of a surface caused by the presence of rivet heads was determined by towing four planing surfaces of the same dimensions. One surface was smooth and represented a surface without rivet heads or one with perfectly flush countersunk rivets. The other three surfaces were each fitted with the same number of full-size rivet heads but of a different type arranged in the same pattern on each surface. The surfaces were towed at speeds representative of the high water speeds encountered by seaplanes during take-off and the range of Reynolds Number covered by the test was from 4 x 10(exp 6) to 18 x 10(exp 6). The rivet heads investigated were oval countersunk, brazier, and round for rivets having shanks 5/32 inch in diameter. The oval countersunk heads were sunk below the surface by dimpling the plating around them. The results of the tests showed that, for the rivet heads investigated, the increase in the friction coefficient of the surface is directly proportional to the height of the rivet head. The order of merit in regard to low resistance is flush countersunk, oval countersunk (whether sunk below the surface or not), brazier, and round.

Truscott, Starr↗
NASA NTRS1972

Stress wave riveting

The stress wave riveter deforms the rivet material by a high amplitude stress wave. Thus, the entire rivet is set in motion radially. The rivet expands rapidly and impacts the hole surface before the rivet tail begins to form. Unlike the oversqueezed rivets, therefore, it sets up uniform interference without distortion in the skins. Furthermore, the radial velocity is so high (over 200 in./sec) that upon impact with the hole surface it deforms the surface plastically. This is especially effective in aluminum skins. Thus the SWR combines the advantages of plastically deforming the hole and the economic advantage of a relatively nonprecision hole and inexpensive rivets like those used in oversqueezing. The additional advantage SWR offers is that it is a portable tool.

Leftheris, B. P.↗
NASA NTRS2000

Residual Strength Analyses of Riveted Lap-Splice Joints

The objective of this paper was to analyze the crack-linkup behavior in riveted-stiffened lap-splice joint panels with small multiple-site damage (MSD) cracks at several adjacent rivet holes. Analyses are based on the STAGS (STructural Analysis of General Shells) code with the critical crack-tip-opening angle (CTOA) fracture criterion. To account for high constraint around a crack front, the "plane strain core" option in STAGS was used. The importance of modeling rivet flexibility with fastener elements that accurately model load transfer across the joint is discussed. Fastener holes are not modeled but rivet connectivity is accounted for by attaching rivets to the sheet on one side of the cracks that simulated both the rivet diameter and MSD cracks. Residual strength analyses made on 2024-T3 alloy (1.6-mm thick) riveted-lap-splice joints with a lead crack and various size MSD cracks were compared with test data from Boeing Airplane Company. Analyses were conducted for both restrained and unrestrained buckling conditions. Comparison of results from these analyses and results from lap-splice-joint test panels, which were partially restrained against buckling indicate that the test results were bounded by the failure loads predicted by the analyses with restrained and unrestrained conditions.

Seshadri, B. R.↗
DOE OSTI2020

Joining Dissimilar Materials via Rotational Hammer Riveting Technique

A mechanically robust joining method for Mg/Al and Mg/CFRP could enable multi-material assemblies that decrease vehicle weight while offering more flexibility for designers. However, certain challenges exist for joining Mg/Al and Mg/CFRP. Mechanical joining, such as conventional riveting, clinching and bolting do not form a metallurgical bond between the fastener and metal sheet being fastened. Large differences in physical and mechanical properties of metals and polymers make joining Al or Mg to CFRP challenging via various welding techniques. With solid-state and fusion based welding, rapid formation of brittle intermetallic compounds at the Mg/Al interface lead to interfacial fracture under mechanical loading. In this study, a Rotational Hammer Rivet (RHR) technique was developed to fabricate Mg/CFRP and Mg/Al joints. With RHR technique, direct joining between Mg/Al and Mg/CFRP were replaced by joining Mg rivet head and top Mg sheet. Through heat generated by plastic deformation of an Mg rivet, RHR creates a metallurgical bond between rivet head and Mg sheet which seals corrosive electrolyte from penetrating around the rivet head.

riveting, magnesium alloys, CFRP, Dissimilar Joini↗
DOE OSTI2023

Joining of High Strength Low Ductility AA7055 by Friction Self-piercing Rivet

High strength aluminum (Al) alloy is one of higher specific strength materials for decarbonization in transportation industries. Because of low ductility at room temperature, conventional mechanical fastening such as self-piercing riveting produces cracks at the joint. In this work, we applied friction self-piercing riveting to join Al alloy (AA) 7055. No cracks were observed in the joints because of the improved local ductility of Al alloy by the generated frictional heat during joining step. Numerical modeling of joining process was applied to guide rivet geometry design and rivet material strength. Mechanical integrity of the AA7055 joints was assessed by lap shear tensile and cross-tension testing. Metallurgical characterizations revealed solid-state bonding formed not only between the rivet and surround Al materials, but also upper and lower Al sheets at the joint interface. Both solid-state bonding and mechanical interlocking between the flared rivet and bottom AA7055 sheet were the major joint mechanisms.

Lim, Yong Chae↗
NASA NTRS1986

Jig for Removing Rivets

Drill-press jig used to remove improperly installed rivets. Drillpress jig makes possible to drill accurately-centered, straight holes through rivets. Key component of jig is a drill bushing with spherical recess machined into base. Contour of recess matches contour of rivet head. Operator holds jig handle with one hand and controls drill with other. Handle and screw head hold drill bit in place over center of rivet so rivet drilled out through its axis. With rivet removed, parts separated and refastened or reused elsewhere.

Roebuck, T. P.↗
NASA NTRS1933

The Effect of Rivet Heads on the Characteristics of a 6 by 36 Foot Clark Y Metal Airfoil

An investigation was conducted in the N.A.C.A. full-scale wind tunnel to determine the effects of exposed rivet heads on the aerodynamic characteristics of a metal-covered 6 by 36 foot Clasky airfoil. Lead punching simulating 1/8inch rivet heads were attached in full-span rows at a pitch of 1 inch at various chord positions. Tests were made at velocities varying from 40 to 120 miles per hour to investigate the scale effect. Rivets at the 5 percent chord position the upper surface of the airfoil produced the greatest increase in drag for a single row. Nine rows of rivets on both surfaces, simulating rivet spacing of multispan construction, increased the drag coefficients by a constant amount at velocities between 100 and 120 miles per hour. Accordingly, if rivets spaced the same as those on the test airfoil were used on a Clark Y wing of 300 square feet area and operated at 200 miles per hour, the drag would be increased over that for the smooth wing by 55 pounds and the power required would be increased by 29 horsepower.

Dearborn, Clinton H↗
NASA NTRS1944

Tensile Tests of Round-head, Flat-head, and Brazier-head Rivets

An investigation was conducted to determine the tensile strength of round-head (AN43C), flat-head(AN442), and brazier-head (AN4556) aluminum-alloy rivets because of the scarcity of information on the tensile strength of rivets. The results of the investigation are presented as curves that show the variation of the ratio of the tensile strength of the rivet to the tensile strength of the rivet crank with the ratio of the sheet thickness to the rivet diameter for the different types of rivet.

Schuette, Evan H↗
DOE OSTI2023

Embedded anchoring of multi-material assemblies by friction riveting process

In this paper, we report on work that focused on extending the capability and broaden the applicability of the friction-riveting process for joining stacks composed of a wide range of multi-layer polymer-to-metals and similar and dissimilar metals. We first present direct experimental evidence of our use of this process to join aluminum-to-steel dissimilar metals with steel rivets. We have demonstrated for the first time the use of magnesium as a rivet material for joining carbon fiber reinforced polymer (CFRP) stacks, aluminum as a rivet material to laminate magnesium to CFRP, and aluminum-to-aluminum similar metal joining and aluminum-to-steel dissimilar metal joining with steel rivets. Our work sheds light on detailed process parameter optimization and the corresponding process response behavior, thus advancing our understanding of this complex joining method for a wide range of material combinations.

Friction-riveting, magnesium rivet, carbon fiber r↗
DOE OSTI2024

Meshfree Process Modeling and Experimental Validation of Friction Riveting of Aluminum 5052 to Aluminum 6061

Friction riveting (Fric-riveting) is an innovative, fast, and energy-efficient process for spot-joining metal-metal structures. Although fric-riveting has been studied experimentally in recent years, its process modeling is rarely found in the literature primarily because of the associated large material deformation, extreme thermomechanical conditions, and complex contact conditions. In this work, a mesh-free smoothed particle hydrodynamics (SPH) framework that can well handle the abovementioned numerical challenges is used to simulate the fric-riveting of AA5052 to AA6061. Predicted material morphology, multi-point temperatures, and plunge force are thoroughly validated by experimental observations. The material severe plastic deformation zone in the vicinity of the riveting zone is further predicted by the SPH model, which indicates the material mixing and potential grain refinement zone. Based on the validated model, process parameters can be optimized which yields better performance over the baseline case.

Friction riveting (fric-riveting), Smoothed partic↗
DOE OSTI2024

Effect of die design on microstructure and mechanical joint strength in friction self-piercing riveted AA7055-T76 and AA7055-T76

In the present study, a unique friction self-piercing riveting (F-SPR) was applied to join high-strength, low-ductility aluminum alloy (AA) 7055-T76 and AA7055-T76 to mitigate a cracking issue. Also, the effect of die design on both joint formation and the mechanical joint performance were investigated. A crack-free joint was achieved when joining AA7055-T76 and AA7055-T76 by F-SPR. As the bottom diameter of the die increased, the mechanical interlocking distance initially increased then became almost saturated. At the same time, the solid-state bonding gradually disappeared, and the lap-shear fracture changed from bottom aluminum fracture to rivet pull-out with partial bottom aluminum fracture. The average maximum lap-shear joint strength of 11.57 kN and cross tension of 5.65 kN were achieved from the D2 die design owing to the combined contributions from high mechanical interlocking distance and good solid-state bonding at the joint interface. Ultrafine grain refinement was observed at the region next to the rivet shank outer surface and along the materials flow line between the top and bottom aluminum sheet in the rivet cavity. Further, because of the same joint-process parameters, the hardness profile at the joints made by different dies did not show obvious differences. As the distance from the base metal to the rivet outer surface decreased, frictional heat caused the hardness to initially decrease from 190 to 150 HV in the heat-affected zone. Hardness increased up to 175 HV in the thermomechanical affected zone (TMAZ-I) owing to large plastic deformation.

36 MATERIALS SCIENCE↗
NASA NTRS1936

Mechanical Properties of Aluminum-alloy Rivets

The development of metal construction for aircraft has created a need for accurate and detailed information regarding the strength of riveted joints in aluminum-alloy structures. To obtain this information the National Bureau of Standards in cooperation with the National Advisory Committee for Aeronautics is investigating the strength of riveted joints in aluminum alloys. The strength of riveted joints may be influenced by the form of the head, the ratio of the rivet diameter to the sheet thickness, the driving stress, and other factors. This note gives the results of tests to develop the riveting technique for test specimens and to determine the effects of these factors.

Brueggeman, Wm C↗
NASA NTRS1994

Results of uniaxial and biaxial tests on riveted fuselage lap joint specimens

As part of an FAA-NLR collaborative program on structural integrity of aging aircraft, NLR carried out uniaxial and biaxial fatigue tests on riveted lap joint specimens being representative for application in a fuselage. All tests were constant amplitude tests with maximum stresses being representative for fuselage pressurization cycles and R-values of 0.1. The parameters selected in the testing program were the stress level (sigma(sub max) = 14 and 16 ksi) and the rivet spacing (0.75 and 1.0 inch). All specimens contained 3 rows of countersunk rivets, the rivet row spacing was 1 inch and the rivet orientation continuous.

Vlieger, H.↗
NASA NTRS1947

The Distribution of Loads on Rivets Connecting a Plate to a Beam under Transverse Loads

This report gives theoretical discussion of the distribution of leads on rivets connecting a plate to a beam under transverse leads. Two methods of solution are given which are applicable to loads up to the limit of proportionality; in the first the rivets are treated as discrete members, and in the second they are replaced by a continuous system of jointing. A method of solution is also given which is applicable to the case when nonlinear deformations occur in the rivets and the plate, but not in the beam. The methods are illustrated by numerical examples, and these show that the loads carried by the rivets and the plate are less than the values given by classical theory, which does not take into account the slip of the rivets, even below the limit of proportionality. The difference is considerably accentuated when nonlinear deformations occur in the restructure and the beam then carries the greater portion of the bending moment. If the material of the beam has a higher proportional limit and a higher ultimate strength than the material of the plate, there is thus a transfer of load from weaker to stronger material, and this is to the advantage of the structure. The methods given are of simple application and are recommended for use in the design of light-alloy structures when the design lead is likely to be above the proportional limit.

Vogt, F.↗
DOE OSTI2022

Ultrasonic rivet joining of dissimilar materials

A method for joining dissimilar materials is provided. The method includes a solid-state joining process in which a rivet is plunged into a predrilled hole in a top workpiece. When the rivet contacts the bottom workpiece, ultrasonic vibration by oscillatory motion of a sonotrode, such as horizontal, vertical, or rotational motion, creates frictional heat at the interface between the rivet and the lower workpiece. With the aid of frictional heat and axial compression, metallurgical bonding is achieved at the interface between the rivet and the bottom sheet, while being below the melting temperature of the bottom workpiece. The sonotrode is retracted while the rivet remains.

Lim, Yong Chae↗
DOE OSTI2023

Extent of interlocking and metallurgical bonding in friction riveting of aluminum alloy to steel

In this study, the joining of 6061-T6 aluminum alloy and DP590 steel using a M42 steel rivet via friction riveting technique is investigated. The surface morphology and microstructure characterization reveal the formation of an anchor zone that imparts mechanical interlock as well as the formation of metallurgical bonds at the interface of aluminum and steel. A combination of interlocking and bonding results in the achievement of a high load-carrying capacity of 5.7 kN during lap shear testing at room temperature. A finite element-based computational model was developed which accurately predicted the lap shear response of the joint. The model revealed that the metallurgical bond formed during fric-riveting adds 39% peak load strength to the joint. An extensive microstructural investigation, post-lap-shear fractography, and the modeling results, together provided insights on the joint failure mechanism. In conclusion, this study highlights that friction riveting is a promising method for aluminum-to-steel dissimilar joining, which is important for lighweighing automotive vehicles for energy efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mechanical joint performances of friction self-piercing riveted carbon fiber reinforced polymer and AZ31B Mg alloy

Carbon fiber reinforced polymer (CFRP) and AZ31B Mg alloy were joined by the friction self-piercing riveting (F-SPR) with different steel rivet shank sizes. With the increase of rivet shank size, lap shear fracture load and mechanical interlock distance increased. Ultrafine grains were formed at the joint in AZ31B as a result of dynamic recrystallization, which contributed to the higher hardness. Fatigue life of the CFRP-AZ31B joint was studied at various peak loads of 0.5, 1, 2, and 3 kN and compared with the resistance spot welded AZ31B-AZ31B from the open literature. The fatigue performance was better at higher peak load (>2 kN) and comparable to that of resistance spot welding of AZ31B to AZ31B at lower peak loads (<1 kN). From fractography, the crack initiation for lower peak load (<1 kN) case was observed at the fretting positions on the top and bottom surfaces of AZ31B sheet. When peak load was increased, fretting between the rivet and the top of AZ31B became more dominant to initiate a crack during fatigue testing.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Friction Self-piercing Riveting Process for 3T Configuration of AA7075-AA7075-AA6022

Friction self-piercing riveting (F-SPR), as a solid-state joining process that generates frictional heat during the process, was utilized to join a 3 T configuration of low-ductility AA7075-AA7075-AA6022 sheets. A multi-step F-SPR process was employed to precisely control the mechanical interlocking and solid-state joining, ensuring a strong joint formation. With control of the plunge depth when the transition from rivet penetration to rivet flaring, two joining conditions were developed to assess mechanical joint integrity: one bearing deep penetration with a smaller interlock, and the other yielding a shallow penetration with a larger interlock. Both strategies met the criteria for a sound rivet joint. Customized lap shear tensile configurations were designed to assess the joint strength at interface between first and second layers, as well as between second and third layers. Both conditions demonstrated great joint strength between the first and second layers, while deeper penetration approach showed stronger solid-state joint, leading to improved joint strength between the second and third layers.

Wang, Tianzhao [ORNL] (ORCID:0000000315337602)↗