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To investigate the low-speed impact response of the BR1200HS steel and AA6082 aluminum alloy self-piercing riveted (SPR) joint, low-speed impact tests with impact energies of 2.5 J, 5.0 J, 7.5 J, 10.0 J, 12.5 J, 15.0 J, 20.0 J, and 30.0 J were conducted utilizing a drop hammer impact tester. The results show that with the increased impact energy, the visual breakages of the SPR joints become more severe. The maximum impact energy the joints can sustain ranges from 10.0 J to 12.5 J. When the impact energy is less than 12.5 J, the contact force/energy–time curves show similar variations. Moreover, as the impact energy increases, total uptake energy value (Et), maximum uptake energy value (Ef), and maximum contact force (Fm) of the joints increase gradually. The low-speed impact energy has little effect on the maximum static tensile force of the impacted joints. However, the residual energy values decrease with the increase in impact energy. The tensile failure form of the joints is the pulling out of the rivets from the lower plates, and the low-speed impacts have no significant effect on the tensile failure form of the joints. [ABSTRACT FROM AUTHOR]

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. 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. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on the mechanical quasi-static behavior of self-piercing rivet (SPR) connections with three stacked sheets made from an AA6016-T4 aluminum alloy. The goal was to study the effects of sheet thickness and stack up of the SPR connection under large deformation and failure. Several different types of tests were performed to investigate the initial load-bearing capacity as well as the remaining capacity after partial joint failure. Additionally, the performance of state-of-the-art constraint modeling techniques was evaluated. The parameters for large-scale connector models were found through inverse modeling of the experiments. The models were validated against an additional test configuration where the middle sheet was load-free. [ABSTRACT FROM AUTHOR]

This paper presents a new solution for shaping the rivet progression of a beverage end. The classic method uses three operations to press the cylindrical rivet using 0.208 mm and 0.203 mm thick sheets. The increasing demand for aluminium alloys is prompting measures to make more efficient use of this raw material. One possible solution is to produce packaging from ever thinner sheets. This requires the design of new tooling and the preparation of an appropriate technological process. A method has been developed to stamp a hexagonal-shaped rivet from 0.200 mm thick sheet metal, increasing the number of stamping operations to four. The proposed method was verified through a numerical analysis using the PAM STAMP 2022.0 software package. It was found that for appropriately shaped tools, sheet thicknesses of the stamped component could be achieved that were not less than those for the currently used technology, thus eliminating any possible break in the material structure. Suitable tools and experimental stamping tests were carried out for the developed process. In the simulations, the material Al5182_iso_Xmm was adopted from the programme database, while the experiments were performed on a laboratory press using AW-5182-H48 sheets with a thickness of 0.200 mm. The purpose of the study was to determine the validity for the proposed method of forming the rivet of the beverage end. [ABSTRACT FROM AUTHOR]

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Self-piercing riveting (SPR) is an efficient joining process for bonding sheets through the interlock of rivet flaring. The strength of SPR joints is commonly measured by destructive test. In this study, the metal deformation behaviors in the SPR of aluminum alloy sheets and the mechanical behaviors of the SPR joints in the destructive tests were investigated in order to develop the general strength models of SPR joints. As the important feature in the SPR process, the rivet flaring was quantified by an empirical estimator and utilized to establish the general strength models considering the geometric dimensions of components and tools, the material properties of rivet and sheets, and the load–displacement curve of punch. The predicted strengths of the SPR specimens were verified by the experimental results. All the calculation errors are lower than 8%. Finally, an industrial internet of things (IIoT) was developed to realize the data processing and the SPR joint strength predication. [ABSTRACT FROM AUTHOR]

Cast aluminum alloys are promising materials that can simplify the manufacturing process of automobile body structures. However, the low ductility of cast aluminum poses significant challenges to existing riveting technologies. In the present work, dissimilar AA6061-T6 aluminum alloy and Al-Si7Mg cast aluminum were joined by self-piercing riveting (SPR) and friction self-piercing riveting (F-SPR) processes to reveal the effect of friction heat on rivetability of low-ductility cast aluminum alloys. The joint macro-morphology, microstructure, peak tooling force, microhardness distribution, tensile-shear, and cross-tension performance of the two processes were comparatively studied. Results indicated that the in-situ softening effect of friction heat in the F-SPR process could effectively improve the ductility of cast aluminum, avoid cracking, and reduce the tooling force by 53%, compared to the SPR process. The severe plastic deformation and friction heat induced by rivet rotation results in refined equiaxed grains of aluminum near the rivets and solid-state bonding between aluminum sheets in the rivet cavity. The F-SPR joints are superior to SPR joints in both tensile-shear and cross-tension performance due to the avoidance of cracking, increase of mechanical interlocking, and solid-state bonding of interfaces. Significantly, when Al-Si7Mg is placed on the lower layer, the peak tensile-shear and cross-tension loads of the F-SPR joints are 7.2% and 45.5% higher than the corresponding SPR joints, respectively. [ABSTRACT FROM AUTHOR]

Clinch riveting, which originates from clinching, is an effective way to join aluminum alloy. The presence of rivet significantly improves the shearing load of joint. However, rivet deforms plastically in the forming process, which increases the technological intricacy consequently. This article proposed the clinch riveting with rigid rivet. The influence of thickness combinations on joint quality was investigated. Aluminum alloy (AA5052) was used to produce the joints, and five thickness combinations were tested. The cross sections of joints were observed, and geometrical parameters of joints were obtained. The static loads of joints were measured in tensile, and shearing tests and absorbed energy values of joints were calculated. The failure modes of joints were analyzed. In tensile tests, neck fracture and button separation could be observed. While in shearing tests, all joints failed at neck parts. Results showed that thickness combinations exerted a significant influence on geometrical parameters and strength of joint. When joining sheets with different thickness, the joint with thicker sheet on the top exhibited larger neck thickness and shearing load than the joint with thicker sheet on the bottom. For the joints with the same total thickness, as the thickness ratio between top sheet and bottom sheet increased, both the interlock thickness and the tensile load of joint first increased then decreased. [ABSTRACT FROM AUTHOR]

Friction self-piercing riveting (F-SPR) process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals, such as magnesium alloys, cast aluminum, and 7 series aluminum alloys. In this paper, in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR, a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B. The results indicate that a 1.0 mm die distance is effective to avoid rivet upset and insufficient flaring. As the feed rate increases, the heat input in the whole process decreases, resulting in a larger riveting force, which in turn increases both the bottom thickness and interlock amount. Besides, solid-state bonding, including Al-Mg intermetallic compounds (IMCs), Al-Mg mechanical mixture, and Al-Fe atom interdiffusion was observed at the joint interfaces. The upper Al layer was softened, but the lower Mg layer was hardened, and both sheets exhibited a narrowed affected region with the increase of feed rate, while the rivet hardness shows no obvious change. Three fracture modes appeared accompanying the variations in lap-shear strength and energy absorption as the feed rate increased from 2 mm/s to 8 mm/s. Finally, the F-SPR process using a flat die was compared to those using a pip die and a flat bottom die to show the advantage of flat die on coping with the misalignment problem. [ABSTRACT FROM AUTHOR]

• A novel refill friction stir riveting (RFSR) process is proposed for the first time. • Both solid-state bonding and mechanical interlocking are achieved in RFSR joints. • The size of mechanical interlock is predefined by the groove on the rivet shank. • The high-quality solid-state bonding is generated at the sheet faying surface. • The joint lap-shear and cross-tension forces are 9.09 kN and 6.82 kN respectively. In this study, a novel refill friction stir riveting (RFSR) process was proposed to achieve hybrid solid-state bonding and mechanical interlocking of high-strength aluminium alloy AA7075-T6 sheets. The size of mechanical interlock is predefined by the depth of groove designed on the rivet shank, and realized through sheet material refilling. High-quality solid-state bonding is also generated at the sheet faying surface under the high pressure and strong friction stir from the rivet. The quality characteristics, microstructure, heat generation, microhardness distribution and mechanical properties were systematically investigated to uncover the joint formation mechanism and verify the effectiveness of the RFSR process. The results reveal that a mechanical interlock with 82% of the predefined value was successfully achieved by sheet material refilling into the groove on the rivet shank. An extra mechanical interlock, which was formed between the rivet shank and trapped bottom sheet, further enhanced the joint strength. Continuous solid-state bonding with a width of 0.39 mm was also generated between the two sheets. Strengthened by the multiple connection features, the peak lap-shear and cross-tension forces reached up to 9.09 ± 0.24 kN and 6.82 ± 0.11 kN respectively, and the corresponding failure modes were rivet shank fracture and pull-out of rivet shank from the bottom sheet. [ABSTRACT FROM AUTHOR]

Self-piercing riveting has been widely used in vehicle body manufacturing to join aluminum alloys or aluminum to steel. However, it is difficult to rivet ultrahigh strength steel (UHSS) because of its resistance to piercing of the rivet. In this paper, a thermally assisted self-piercing riveting (TA-SPR) process was proposed to improve riveting of the UHSS, through locally preheating the UHSS sheet using an induction coil prior to the traditional self-piercing riveting (SPR) process. An experimental system consisting of inductive heating apparatus, conventional self-piercing riveting equipment, and coupon transfer mechanism was established and the steps, e.g., preheating, coupons transfer, and riveting, were automatically conducted at preset schedules. Based on experiments with this system, the effects of heating current, heating time, and coil heating distance on riveting of AA6061-T6 and DP980 were examined systematically by metallurgical analyses and mechanical tests. It was found that an appropriate combination of heating current and heating time, e.g., 0.5 s at 600 A, could produce crack-free joints having 77.8% higher undercut and 24% higher lap-shear strength, compared with results obtained using a conventional SPR process. [ABSTRACT FROM AUTHOR]

AA7xxx series aluminum alloys have great potentials in mass saving of vehicle bodies due to pretty high specific strength. However, the use of these high strength materials poses significant challenges to the traditional self-piercing riveting (SPR) process. To address this issue, a novel process, friction self-piercing riveting (F-SPR), was applied to join aluminum alloy AA7075-T6 sheets. The effects of the spindle speed and rivet feed rate on F-SPR joint cross section geometry evolution, riveting force, and energy input were investigated systematically. It was found that the rivet shank deformation, especially the buckling of the shank tip before penetrating through the top sheet, has significant influence on geometry and lap shear failure mode of the final joint. A medium rivet feed rate combined with a high spindle speed was prone to produce a defect-free joint with sound mechanical interlocking. F-SPR joints with the failure mode of rivet shear fracture were observed to have superior lap shear peak load and energy absorption over the joints with mechanical interlock failure. The optimized F-SPR joint in this study exhibited 67.6% and 13.9% greater lap shear peak load compared with SPR and refill friction stir spot welding joints, respectively, of the same sheets. This research provides a valuable reference for further understanding the F-SPR process. [ABSTRACT FROM AUTHOR]

In this study, the effects of thermal fatigue loading on the riveted structures made of 2014, 2024, 6061 and 7075 aluminum alloys which are widely used in the aviation industry have been investigated. An algorithm has been developed under ANSYS finite element analysis software to determine the behavior of these structures that are exposed repeated thermal loading. This algorithm is based on the principle of determining the distribution of the safety factor on the material subjected to the thermal fatigue load. In the study, the rivet spacing (RS), the rivet edge distance (ED) and the rivet hole diameter (RD) were selected as riveting parameters. It is aimed to determine the optimum values of the parameters used under thermal fatigue loading and the most suitable one for this loading among the materials used. It is seen that 7075 aluminum alloy has the highest safety factor distribution for all the models in which the effect of these parameters was investigated. It has been determined that when the rivet spacing is 3 times the rivet diameter (3d), the highest safety factor value is obtained for all material types. And this value decreases when the rivet spacing is increased. When the effect of the rivet edge distance is examined, it is seen that when the rivet edge distance 8d is used, the highest safety factor value is obtained. The safety factor value is the smallest when the rivet edge distance is 2,5d. In addition, when rivet hole diameter increased from 2.5 mm to 4.8 mm, it was determined that safety factor value increased. [ABSTRACT FROM AUTHOR]

Aluminum alloys have been increasingly adopted in the fabrication of automotive body structures as an integral component of mass savings strategy. However, mixed use of dissimilar aluminum alloys, such as sheet metals, castings, and extrusions, poses significant challenges to the existing joining technologies, especially in regard to single-sided joint access. To address this issue, the current study applied the friction stir blind riveting (FSBR) process to join 1.2µmm-thick AA6022-T4 aluminum alloy to 3µmm-thick Aural-2 cast aluminum. A newly developed, robot mounted, servo-driven, FSBR equipment and the procedure using it to make FSBR joints were introduced systematically. The effect of rivet feed rate and spindle speed on joint formation and cross section geometry was investigated, and it was found that a high spindle speed and a low rivet feed rate, i.e., high heat input, are prone to produce good joints, and that low heat input can cause severe problems related to insufficient softening of the sheets. The rivet deformation, especially the notch location on the mandrel relative to the shank has significant influence on lap-shear strength and fracture mode of the final joints. A rivet pull-out fracture mode was observed at higher rivet feed rates and lower spindle speeds and exhibited significantly improved energy absorption capability, i.e., 62% higher compared to traditional blind riveted (BR) joints. [ABSTRACT FROM AUTHOR]

This paper presents a sensor system for inspection of far-side defects around rivets in a multilayer structure. The sensor system includes 64 InSb Hall sensors arrayed in 0.52-mm intervals, over a total length of 33.28 mm. The sensor system was tested on two flat specimens, which have two layers of an aluminum alloy, with and without far-side defects around rivets. The sensor system performance was estimated via both the receiver operating characteristic and the probability of detection (POD) curves. Furthermore, a quantitative evaluation of the surface area, depth, and volume of a defect having a POD greater than 90% was carried out. [ABSTRACT FROM PUBLISHER]

• The joint failure mode of edge riveting is a coexistence of rivet pull out and riveted mouth sheet fracture; • The strength of the riveted joint based on the upper sheet was relatively high at the same edge pitch; • The maximum shear load was relatively high for the riveted joint near the upper sheet edge; • The error values for the geometric parameters of the joint near the upper sheet edge were smaller. In order to improve the use of aluminium alloys in lightweight automotive body panels, the failure mechanism and mechanical properties of AA5052 aluminium alloy sheets under different conditions were investigated by means of self-piercing riveting (SPR). The impact of riveting position on the structural strength, absorbed energy and instantaneous stiffness of self-piercing riveted connections was analyzed using the edge riveting method. Four edge distances of 1.65 mm, 2.65 mm, 3.65 mm and 4.65 mm were considered for the experimental study, and the riveted structure was analyzed and tensile shear tests were carried out by comparing the mechanical properties. The results indicated that this riveting method changed the failure mode of the joint, with the rivet pulling out from the lower sheet to a co-existence of rivet pull-out and riveted mouth sheet breakage; the maximum shear load, absorbed energy and deformation resistance decreased as the distance from the riveting point to the strip edge decreased; and the strength of the riveted joint based on the upper plate was significantly greater than that based on the bottom plate at the same edge pitch, and the stability of the joint is superior. This study provides a theoretical basis for the damage suppression of aluminium alloy edge riveted joints and the lightweight production of vehicles. [ABSTRACT FROM AUTHOR]

The residual stress profile in dissimilar metal sheets joined by a self-piercing rivet is simulated and compared to experimental measurements. Simulation of joining aluminum alloy 6111-T4 and steel HSLA340 sheets by self-piercing riveting (SPR) is performed using a two-dimensional axisymmetric model with an internal state variable (ISV) plasticity material model. Strain rate and temperature dependent deformation of the base materials is described by the ISV material model and calibrated with experimental data. Using the LS-DYNA simulation package, an element erosion technique is adopted in an explicit analysis of the separation of the upper sheet with maximum shear strain failure criterion. An explicit analysis with dynamic relaxation technique was then used for springback and cooling down analysis following the riveting simulation. The residual stress profile of SPR experimental joint with same configuration is characterized using neutron diffraction, and good agreement was found between the simulation and residual stress measurements. [ABSTRACT FROM AUTHOR]

Conventional magnesium alloys, due to their low ductility, have a poor self-piercing rivetability. Cracks always occur when the magnesium sheet is placed at the bottom layer, which brings great challenge to the use of the magnesium alloys. In this paper, friction self-piercing riveting (F-SPR) process was adopted to join 1 mm thick aluminum alloy AA6061-T6 to 2.2 mm thick magnesium alloy AZ31B, and the effect o f rivet hardness and key geometrical features on joint formation were studied systematically. The experimental results showed that using rivets with a hardness of 190 HV, the top aluminum sheet could be well pierced and a larger rivet shank flaring value would be formed between rivet shank and the bottom magnesium. The effect o f the rivet's geometrical features, including ribs under shoulder and inclination angle under shoulder, were examined using two evaluation criteria, i.e., rivet shank flaring value and remaining thickness, and found that the rivet with no ribs and 10 deg inclination angle under shoulder is suitable for joining 1 mm AA6061-T6 to 2.2 mm AZ31B in F-SPR process. [ABSTRACT FROM AUTHOR]

In the present study, the feasibility of joining PA6-matrix thermoplastic composite panel and aluminum alloy is considered. Self-piercing riveting processes of PA6 panels, PA6 composite panels with reinforcing fibers (glass fiber and carbon fiber), and 5754 aluminum alloy sheets are systematically investigated. Macro characterizations of the appearance and transverse sections of the self-piercing riveting joints were conducted to provide more comprehensive understanding of the composite deformation during riveting process. In particular, the effect of reinforcing fibers on the composite deformation behaviors was characterized. Lap-shear testing of the self-piercing riveting joints was performed to evaluate joint strength, and characterization of the fractured joints as well as failure mechanics analysis was conducted to investigate the underlying failure mechanisms of the self-piercing riveting joints. The effects of reinforced fibers on the failure mechanisms and mechanical performance were also discussed. The results showed that self-piercing riveting is an effective technique for joining fiber reinforced thermoplastic composite panels and aluminum alloy sheets. In addition, self-piercing riveting joints with glass fiber reinforced composite failed in a bearing mode and exhibited improved joint strength compared with the PA6 matrix; while self-piercing riveting joints with carbon fiber reinforced composite exhibited slightly decreased joint strength but significantly reduced ductility, owing to the brittleness of the carbon fiber reinforced composite. [ABSTRACT FROM PUBLISHER]

Electromagnetic riveting (EMR) is a new joining technology based on high-speed magnetic impulse forming and conventional riveting. EMR experiments were conducted on dual-layered 2A12 aluminum alloy sheets with one 2A10 aluminum alloy rivet. Observation of the microstructure and mechanical properties of rivet heading verified the forming quality of the heading. And, mechanical property tests were performed to evaluate the durability of riveted specimens through shear and pull-out loading. Microstructure observation indicated that adiabatic shear bands, where the deformation was highly concentrated, were an important characteristic of deformed structures in rivet headings under electromagnetic riveting. The distribution law of hardness in rivet headings was obtained. The compressive yield strength of rivet headings increased 70 % over that of the original rivets. Riveted specimens were capable of withstanding shear loads of 23.2 kN and pull-out loads of 35 kN. Ruptures characterized by a scanning electron microscope were found to be due to shear failure. [ABSTRACT FROM AUTHOR]

A friction stir blind riveting (FSBR) process is used to fabricate joints of carbon fiber-reinforced polymer composite (CFRP) and aluminum alloy AA6111 sheets in a lap shear configuration. Given the 9,000 rpm spindle speed upper limit of conventional computer numerically controlled machines, the maximum feed rate for FSBR joining CFRP to itself is found to be 120 mm min above which quality issues such as cracking of the CFRP sheet predominate. However, the maximum feed rate during dissimilar joining of CFRP to AA6111 can be 420 mm min when the CFRP top sheet is supported by the AA6111 bottom sheet. The maximum lap shear tensile load of the joints shows little dependence on the spindle speed and feed rate during FSBR. The different stack-up sequences of the CFRP and AA6111 lead to different maximum loads, displacements to fracture, and locations of fracture initiation, i.e., in the CFRP vs. in the AA6111. [ABSTRACT FROM AUTHOR]

7-series aluminum (Al) alloy is a promising material that can meet the ever-increasing lightweight demand for transportation tools. However, the assembly between Al alloy and steel components brings challenges to the existing stud pre-embedded technology. This study proposes a friction stud riveting (FSR) process to achieve high-performance and high-efficiency embedding of steel studs in Al alloy parts by shank undercut, grooves interlock, and intermetallic compounds bonding. The stud geometry and FSR process were first optimized by evaluating the macro morphology of the joints. Then, the microscopic characterizations were performed to understand the material flow behavior, plastic deformation, and microstructure evolution of the joint induced by the feeding and rotation of the stud. The results indicate that the transient thermo-mechanical coupled FSR process leads to a continuous transition of sliding, mixed sliding-sticking, and sticking contact conditions between the stud and the Al alloy, resulting in a thermo-mechanical affected zone (TMAZ) outside the stud and a trapped Al alloy (TAA) inside the stud with diverse dynamic recrystallization (DRX) states and microstructures. The rotation state evolution and temperature gradients of the material within the TAA create two DRX bands that dominate the fracture behavior of TAA under tensile and shear loads. The strengths of the optimized steel stud-thick Al FSR joints reach 101.3% and 118.5% of the 7A52 Al alloy base material in tensile and shear tests, respectively, which solves the problem of low joining strength between steel stud and Al alloy plate due to the brittle and thick intermetallic compounds layers in conventional stud welding processes. [Display omitted] • Friction stud riveting process is proposed for steel stud-thick Al plate joining. • Shank macro-undercut and grooves micro-interlock form the primary bearing capacity. • The DRX grain refinement and interfacial solid-phase joining enhance the FSR joint. • The strength of FSR joints is greater than that of 7A52 base metal. [ABSTRACT FROM AUTHOR]

Dissimilar lap-shear joints were fabricated by the friction stir blind riveting process using AA6111 (0.9 mm) as the top-sheet and AA6022 (2.0 mm) as the bottom-sheet in a 2-sheet stack-up. Tensile testing of the friction stir blind riveting joints exhibited a combined fracture mode of initial shear followed by tearing. The maximum tensile load of the friction stir blind riveting joints increases slightly with increasing feed rate and shows little dependence on the spindle speed. The microhardness of the material at different layers along with the rivet penetration are analyzed and discussed. [ABSTRACT FROM AUTHOR]

Self-pierce riveting has a future in the sheet metal assembly process in automotive industry. This paper aims to analyze the variation of auto-body aluminum alloy sheet metal assembly in self-pierce riveting and obtain the method of assembly variation analysis. With the help of the method of influence coefficients and the research of the assembly progress of auto-body aluminum alloy sheet metal in self-pierce riveting, a model which can reflect the effects of part variation, riveting tool variation, and fixture variation on assembly quality is established. The feasibility of assembly variation analysis is also verified by some practical cases. Finally, the orthogonal experiment has been carried out to analyze the effects of some variation sources on the variation of assembly in self-pierce riveting. [ABSTRACT FROM AUTHOR]

The hybrid use of dissimilar lightweight materials, such as aluminum alloy and advanced high strength steel (AHSS), has become a critical approach to reduce the weight of ground transportation vehicles. Self-piercing riveting (SPR) as a preferred cold-forming fastening method is facing problems like weak interlocking and insufficient penetration, due to the reduced formability of AHSS. In this paper, a new process named electroplastic self-piercing riveting (EP-SPR) was proposed to reduce the deformation resistance of AHSS DP780, by applying a direct current (dc) to it during the riveting process. The influence of dc on force and displacement characteristics throughout the riveting process, joint physical attributes and quasi-static performances for two sheet combinations, e.g., AA6061-T6 to DP780 (combination 1) and DP780 to AA6061-T6 (combination 2), were studied and compared with the traditional SPR joints. The results showed that compared with the traditional SPR joints, the EP-SPR ones increased by 12.5% and 23.3% in tensile-shear strength and cross-tension strengths for combination 1, respectively. For combination 2, even though the EP-SPR joints'decreased by 5.8% in tensile-shear strength, it could reduce the penetration risk of bottom AA6061-T6, and present a better energy absorption capability for the increased undercut amount. In addition, the corresponding cross-tension strength of EP-SPR joints still increases by 6.1%. [ABSTRACT FROM AUTHOR]

Abstract: The joining of two aluminium plates with an aluminium self-piercing rivet, as discussed by , showed that heating to soften the plates to be joined might be used to avoid plastic compression or fracture in the rivet. In the present paper, the mechanical behaviour of self-piercing riveted connections using an aluminium rivet was investigated. Two U-shaped specimens in alloy AA6063-W, obtained by a solution heat treatment of the alloy in temper T4, were joined using an aluminium self-pierce rivet in alloy AA7278-T6. The mechanical behaviour of these connections was tested after 3 and 30 days of natural aging of the riveted specimens. Test results showed that the strength of the aluminium riveted joints tended to stabilize after three days of natural aging. In order to evaluate the process effect (i.e. the effect of the pre-straining of the plates in W temper as the result of the riveting process, and the subsequent natural age-hardening of the plates) on the mechanical properties of the riveted connection, a comprehensive material test programme was carried out. Test results revealed that there is an interaction between the pre-straining and natural aging which lowers the material properties in terms of the flow stress compared to the ‘virgin’ material, i.e. the curve obtained after heat treatment and aging only. Then, the process effect on the mechanical behaviour of the riveted connections was investigated more closely by using a 3D-model generated in LS-DYNA. The combined effect of the pre-straining and natural aging was accounted for in the numerical analyses by means of a user-defined constitutive model. Numerical analyses revealed that it is necessary to consider the combined effect of plastic deformation and aging in order to predict the mechanical behaviour with a reasonable accuracy. [Copyright &y& Elsevier]

This paper presents research progress in the assembly dimensional prediction area, using finite element analysis results. A case study of the SPR of two sheets of the aluminium alloy using a steel rivet was investigated The riveting analysis has been performed for joined sheets using finite element method (FEM) with MSC Marc Mentat software. Thus, a simulated analysis was adopted in this study to improve industrial productivity. The comparison analysis has been performed within the numerical experiment range to cover the effect of various riveting process parameters on the rivet deformation. Proper selection of corresponding rivet material features, i.e. its yield point and strain hardening, enables significant changing of the sheet joining process and specific finished joint parameters. The finite element simulation is effective in determining the optimal conditions. [ABSTRACT FROM AUTHOR]

In the paper, the growing interest on hybrid joints developed between composite panels and aluminium alloys blanks is focused. The self-piercing riveting operation is considered and its feasibility for the proposed joints verified. The most relevant process parameters were investigated in order to determine a suitable process window and, what is more, the mechanical performances of the developed joints were investigated in order to determine process parameters aimed to maximise them. Finally, the failure mechanics of the obtained joints were considered in order to highlight the mechanisms which occur and determine the lost of the load carrying capability of the joints. The developed experiments demonstrated that self-piercing riveting can be effectively used to join fibreglass composite panels and aluminium blanks. [ABSTRACT FROM AUTHOR]

Abstract: High tensile strength steel sheets having different strengths were joined with an aluminium alloy sheet by a self-piercing rivet. In the joining, a conventional rivet and die used for aluminium alloy sheets were employed in order to have the versatility for various steel sheets. The effects of the flow stress of the high strength steel sheets and the combination of the sheets on the joinability of the sheets were investigated by finite element simulation and an experiment. As the tensile strength of the high strength steel sheet increases, the interlock for the upper high strength steel sheet increases due to the increase in flaring during the driving through the upper sheet, whereas that for the lower high strength steel sheet decreases. The joint strength for the lower high strength steel is comparatively smaller than that for the upper high strength steel sheet. It was found that the high tensile strength steel sheets below 590MPa were fully joined with the aluminium alloy sheet even with the conventional self-piercing rivet and die. [Copyright &y& Elsevier]

Self-pierce riveting of three thin sheets of 980 MPa steel and 5052 aluminum alloy was performed to investigate the effect of sheet configuration on the deforming behaviors of the sheets and the rivet and joint strength. When the lower sheet was aluminum alloy, the joining range was relatively wide, i.e., the interlock hooking the rivet leg tended to be large. In the sheet configuration in which the upper and lower sheets were A5052 and the middle sheet was 980 MPa steel, the rivet leg spread out moderately and the joint without defects was obtained. In the lower 980 MPa steel sheet, fracture tended to occur due to the low ductility of the lower sheet, and the joining range was narrow with the small interlock although the three sheets were joined by an appropriate die shape. In joint strength of joined three sheets, fracture occurred in the lower-strength aluminum alloy sheet if interlocks of about 300 μm and 150 μm could be formed in the lower aluminum alloy sheet and 980 MPa steel sheet, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A study examining the effect of specimen configuration on the mechanical behaviour of self-piercing riveted, multi-layer joints in aluminium alloys was conducted. It has observed that the specimen configuration had a significant effect on the strength and failure mechanism of a self-piercing riveted multi-layer joint. During shear testing, when secondary bending was present interlock failure was observed, while in the absence of secondary bending, sheet material failure occurred. Interlock and sheet material failure modes were also observed in T-peel tests, where depending on the configuration, either substrate failure led to peeling the top sheet away from the rivet head, or interlock failure resulted in pulling the rivet out of the bottom sheet. In the cases where the sheet material failed, an increase in sheet material strength led to an increase in joint strength. Under identical setting conditions, joints with double shear and no secondary bending effect exhibited significantly higher shear strength and more energy absorption than joints in single shear. [Copyright &y& Elsevier]

Abstract: Ultra high strength steel and aluminium alloy sheets were plastically joined by a self piercing rivet driven through the upper sheet and spread in the lower sheet with a die. The self piercing rivet directly pierces into the sheets without drilling the sheets beforehand unlike the conventional rivets. Insufficient driving though the upper sheet and fracture of the lower sheet occur due to the high hardness and low ductility of the ultra sheet, respectively. An ultra high strength steel sheet having a tensile strength of 980MPa and an aluminium alloy sheet were successfully joined by optimising shapes of the die. [Copyright &y& Elsevier]

Abstract: Monotonic and fatigue strengths of coach peel pop rivet (CPPR) and coach peel self-piercing rivet (CPSPR) joined specimens of aluminum alloy with different plate thickness combinations were investigated. The CPSPR specimens also had epoxy bond as a part of the joint. Fatigue tests were performed in load-control and with load ratio, R=P min/P max, ranging between 0.1 and 0.75. It was observed that plate thickness combination has a significant effect on the ultimate monotonic strength of CPPR joints, but is not the only factor that affects the ultimate strength of CPSPR joints. The ultimate strengths of the CPSPR joints are lower than those of the CPPR joints with the same thickness combinations, and their failure locations depend on the thickness combinations of the joined plates under monotonic loading. However, the overall fatigue performance of the CPSPR joints is better than that of the CPPR specimens with the same thickness combinations. Fatigue crack formation locations and growth paths depend on plate thickness combinations, applied load level, and load ratio for both CPPR and CPSPR joints. [Copyright &y& Elsevier]

The fatigue behaviour of single- and double-rivet aluminum alloy 5754-O self-piercing riveted (SPR) lap joints has been investigated experimentally and analytically. With the single rivet, the experimental program involves a set of 27 cyclic tension tests on joints with 1-, 2- or 3-mm-thick sheet coupons. In most cases (85%), fatigue cracks are found to initiate in the gross section on the faying surface of the upper sheet. With two rivets (installed in two rows), the experimental program consists of nine cyclic tension tests, three for each of the three combinations of riveting orientation possible, on SPR joints consisting of 2-mm-thick sheet specimens. The fatigue life of double-rivet joints is found to be strongly dependent on the orientation combination of the rivets. Monotonic tests with the double-rivet joints also reveal an influence of orientation combination. In addition to experiments, values of local stress and rivet-sheet microslip in the single-rivet joints have been evaluated through three-dimensional elastic finite-element analysis. The analyses are used to interpret experimental observations of fatigue crack initiation location, life and fretting damage severity. [ABSTRACT FROM AUTHOR]

During the self-piercing riveting process of carbon fiber reinforced polymer (CFRP) and aluminum sheets, the CFRP is penetrated by the rivet, which weaken the mechanical properties of the joint of CFRP and aluminum alloy sheets to a certain extent. To improve quality of the joint, this study proposes a post-curing self-piercing riveting (PC-SPR) method to join CFRP with aluminum alloy sheets. The mechanical properties and failure modes of the joints were studied through tensile shear tests and the effects of joint structure and CFRP thickness on joint quality were examined. The failure mode of the joint was analyzed by observing the microscopic appearance, and the damage mechanism of the joint was systematically discussed. Results showed that compared with regular self-piercing riveting (R-SPR) joints, PC-SPR joints had better strength. [ABSTRACT FROM AUTHOR]

• A modified thermal self-piercing riveting process for AA7075-T6 aluminum sheets was proposed. • Optimal riveting temperature for producing T-SPR joint with good joinability was found. • Mechanical behaviors and failure modes of two lap-joints were investigated. • Effects of loading angle and loading speed on T-SRP joinability were discussed. The self-piercing riveting (SPR) owns more advantages of acquiring high joint strength for similar and dissimilar metal sheets than the traditional spot welding. However, the conventional SPR may not obtain good joint quality for AA7075-T6 aluminum alloy sheets due to its high strength and low ductility. Thereby, the possibility of self-piercing riveting under elevated temperatures improving the riveting quality and mechanical behavior has thus been raised as an interesting topic. In this paper, a modified thermal self-piercing riveting (T-SPR) technology for AA7075-T6 sheets was proposed based on the process that the substrate was firstly heated and conducted by the subsequent riveting and heat treatment process. The post-riveted quality and quasi-static mechanical behavior of T-SPR joints under designated temperatures were intrinsically investigated by quantifying the interlocking parameters and the single-lap shear test to assess the optimized riveting temperature. Subsequently, an improved Arcan test was employed to investigate the quasi-static mechanical behavior of cruciform joints under different loading conditions. The failure modes of cross-lap joints were analyzed in detail by combining the experiments and FE simulations coupled with Johnson-Cook (J-C) strength and damage models. The influences of loading angle and loading speed on the mechanical behavior of T-SPR joints were further discussed. The outcomes show that the joinability of T-SPR for AA7075-T6 aluminum alloys can be largely improved by increasing the riveting temperature to 400°C. The loading angle and loading speed also have a significant impact on the mechanical behaviors and failure modes of T-SPR joints under quasi-static loading conditions. Image, graphical abstract [ABSTRACT FROM AUTHOR]

One thin 5000 series aluminium alloy sheet and two thin 980 MPa grade cold rolled ultra-high strength steel sheets were joined by self-pierce riveting and mechanical clinching processes. The joinabilities for a combination of the aluminium and steel sheets in both processes were investigated for different die shapes in the experiment and finite element simulation. In self-pierce riveting, the three sheets were successfully joined for both combinations of the upper and lower aluminium alloy sheets by optimizing the shapes of a die and rivet. In mechanical clinching, the three sheets were successfully joined by an optimum die for the configuration of the upper aluminium alloy sheet. On the other hand, the three sheets for the configuration of the lower aluminium alloy sheet were not joined even by optimizing the die shape in the both finite element simulation and experiment, because the material flow of the steel sheets was insufficient to form the two interlocks. The tension-shear loads for the clinched and riveted sheets with the adhesive were almost the same, because the load for the adhesive was the highest. In the cross-tension test, however, the load by the adhesive was comparatively small. [ABSTRACT FROM AUTHOR]

Friction rivet joining was proposed to replace toxic aldehyde-based adhesives for the joining of wood-metal hybrid structures towards high mechanical performances. Polymer rivets were utilized for superior mechanical performances. Three biphasic interfaces among woods, metals, and polymers were achieved reliably with mechanical interlocking and chemical bonding. Polymer films at the interface between metals and woods were obtained by the squeezing flow of polymer rivets, which provided an alternative approach to achieving the effective bonding indirectly. The tensile shear strength and pull-out strength of the wood-metal hybrid structures reached 36.03 ± 0.91 and 30.32 ± 0.79 MPa, respectively, and the specially-designed joint form was proved to be substantially immune to humidity without external protection and improve the load-bearing performances. A finite element model with wider range of geometric parameters was proposed to illustrate the general structural response. The result indicates that friction rivet joining has the potential to join adhesive-free wood-metal hybrid structures with high performances. [ABSTRACT FROM AUTHOR]

The present work investigates the correlation between energy efficiency and global mechanical performance of hybrid aluminum alloy AA2024 (polyetherimide joints), produced by force-controlled friction riveting. The combinations of parameters followed a central composite design of experiments. Joint formation was correlated with mechanical performance via a volumetric ratio (0.28–0.66 a.u.), with a proposed improvement yielding higher accuracy. Global mechanical performance and ultimate tensile force varied considerably across the range of parameters (1096–9668 N). An energy efficiency threshold was established at 90 J, until which, energy input displayed good linear correlations with volumetric ratio and mechanical performance (R-sq of 0.87 and 0.86, respectively). Additional energy did not significantly contribute toward increasing mechanical performance. Friction parameters (i.e., force and time) displayed the most significant contributions to mechanical performance (32.0% and 21.4%, respectively), given their effects on heat development. For the investigated ranges, forging parameters did not have a significant contribution. A correlation between friction parameters was established to maximize mechanical response while minimizing energy usage. The knowledge from Parts I and II of this investigation allows the production of friction riveted connections in an energy efficient manner and control optimization approach, introduced for the first time in friction riveting. [ABSTRACT FROM AUTHOR]