Search Results (20)

Unlike previous studies focusing on two-layer structures or single-parameter effects, this work systematically investigates the influence of sheet layer combination modes on the mechanical properties of three-layer AA6063-T6 self-piercing riveting (SPR) joints through a combination of experimental testing and numerical simulation. Shear and cross-tensile tests were conducted on three-layer AA6063-T6 SPR joints with three distinct sheet layer combinations: T1 (top/middle: 100 × 40 mm², bottom: 40 × 40 mm²), T2 (top/bottom: 100 × 40 mm², middle: 40 × 40 mm²), and T3 (middle/bottom: 100 × 40 mm², top: 40 × 40 mm²). Experimental results reveal significant differences in joint strength and failure modes across the three combinations. T3 joints exhibited the highest shear strength (9.16 kN) but the lowest cross-tensile strength (3.56 kN), whereas T1 joints showed the highest cross-tensile strength (4.97 kN) but moderate shear strength (8.76 kN). A high-fidelity finite element model was developed to simulate the SPR joint under varying sheet layer combinations, incorporating precise geometric details (0.25 mm mesh at critical zones) and advanced contact algorithms (friction coefficient μ = 0.2). Numerical simulations revealed the stress distribution and failure mechanisms under shear and cross-tensile loading, aligning well with experimental observations. Analysis highlights that the mechanical performance of the joint is governed by two key factors: (1) the stress redistribution in sheet layers due to combination mode variations, and (2) the interlocking strength between the rivet and sheets. These findings provide practical guidelines for optimizing sheet layer combinations in lightweight automotive structures subjected to mixed loading conditions. Full article

Self-piercing riveting (SPR) has become a highly promising new method for connecting dissimilar materials in multi-material vehicle bodies, while the joint’s forming quality which largely affects its connection performance lacks sufficient research. This study conducted a detailed numerical investigation on the forming quality of carbon-fiber-reinforced polymer (CFRP)/aluminum alloy (Al) SPR joint and proposed a novel multi-objective optimization strategy. First, the finite element (FE) model of CFRP/Al SPR joint forming was established and then verified to monitor the forming process. Second, based on FE numerical simulation, the action laws of rivet length and die structural parameters (die depth, die gap, and die radius) on the joint’s forming quality indicators (bottom thickness and interlock value) were systematically studied to reveal the joint’s forming characteristics. Finally, taking the rivet length and die structural parameters as design variables and the above forming quality indicators as optimization objectives, a hybrid Taguchi–Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method was proposed to conduct the multi-objective optimization of the joint’s forming quality. According to the outcomes, the bottom thickness and interlock value of the joint were respectively increased by 10.18% and 34.17% compared with the baseline design, achieving a good multi-objective optimization of the joint’s forming quality, which provides an effective new method for efficiently predicting and improving the forming quality of the CFRP/Al SPR joint. Full article

Aluminum–steel joints are increasingly used in the automotive industry to meet the requirements for energy saving and emission reduction. Among various joining technologies, self-pierce riveting (SPR) and resistance spot welding (RSW) are two well-established technologies for fabricating dissimilar joints with stable and high mechanical performance. However, corrosion will occur in these joints inevitably due to different electrochemical properties, which can degrade the surface quality and the mechanical performance, such as strength. This paper presents a method of understanding the corrosion mechanisms in joining aluminum and steel. For this understanding, a hybrid method combining experimental observations, mechanical properties identification, and analytical approaches was used to assess the evolution of the impact of corrosion on the joining performance, such as traction separation curves. The study was conducted on common combinations used in the vehicles, e.g., a 1.2 mm thickness aluminum alloy (AA 6022) and 2.0 mm thickness hot deep galvanized steel (HDG HSLA 340) joined by SPR and RSW. After the fabrication of these joints, accelerated cyclic corrosion tests of up to 104 cycles were performed, which reproduced the environmental conditions to which a vehicle was exposed. By investigating the microstructural evolution within the joints, the corrosion mechanisms of SPR and RSW joints were revealed, including the initiation and propagation. Moreover, the intrinsic impact of the corrosion on the mechanical performance, including the strength, axial stiffness, and crashworthiness, was analyzed by performing a lap-shear test. It showed that as corrosion proceeds, the fracture modes and mechanical performance are affected significantly. Full article

Friction stir welding (FSW) has gained increasing prominence in the realm of metal–plastic hybrid joints, yet its long-term sustainability remains a subject of uncertainty. This research investigates the sustainability aspect of FSW, positioning it against conventional techniques like adhesive bonding (AB) and self-piercing riveting (SPR). A comprehensive evaluation framework encompassing environmental, social, economic, and physical factors was employed, through which specified criteria were applied to select pertinent sustainability indicators across all dimensions to ensure a thorough assessment. In this study, two advanced multi-criteria decision-making methods (MCDM) were deployed for data normalization and aggregation. Sensitivity analysis was conducted to examine the robustness of the results. The outcomes yielded a sustainability rating system, facilitating a direct and insightful comparison with traditional methods. Based on the results of this study, SPR outperforms both FSW and AB in terms of overall sustainability with comparative average sustainability scores of 75.3%, 54.2%, and 35.3%, respectively. This study not only sheds light on the current state of FSW sustainability but also provides a valuable benchmark for decision-makers in selecting environmentally conscious methods for metal–plastic hybrid joints. Full article

Unique friction-based self-piercing riveting (F-SPR) was employed to join high-strength, low-ductility aluminum alloy 7055 for lightweight vehicle applications. This study aimed to maximize the joint strength of the AA7055 F-SPR joint while avoiding cracking issues due to low ductility at room temperature. A fully coupled Eulerian–Lagrangian (CEL) model was employed to predict the process temperature during F-SPR, and the temperature field was then mapped onto a 2D axisymmetric equivalent model for accelerated numerical analysis. The geometry, dimensions, and material strength of the rivet, as well as the depth of the die cavity and plunging depth, were investigated to enhance joint formation. Also, a static finite-element analysis model was developed to predict and analyze the stress distribution in the rivet under different mechanical testing loading conditions. Overall, the numerical model showed good agreement with the experiment results, such as joint formation and mechanical joint strength. With the aid of virtual fabrication through numerical modeling, the joint design iterations and process development time of F-SPR were greatly reduced regarding the goal of lightweight, high-strength aluminum joining. Full article

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 (E_t), maximum uptake energy value (E_f), and maximum contact force (F_m) 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. Full article

Double-sided self-pierce riveting (DSSPR) can be utilized as an alternative to self-pierce riveting (SPR) to produce butt joints through half-lap joints in dissimilar materials. The mechanical joining process makes use of tubular rivets with simple geometry that are here employed to join two sheets made from aluminium (Al) and copper (Cu). This research work analyses the influence of the stainless-steel rivet on both the electrical and mechanical performance of the joint. The electrical resistance variation of the joined assembly is measured at different temperatures and compared with conventional fastened joints made from the same material combination. The mechanical performance of the aluminium–copper connections is evaluated by means of shear tests and compared to the original fastened Al-Cu joint. An experimental approach is utilized to analyse the combined influence of different mechanical and electrical parameters to assess the performance of DSSPR in electrical applications. Full article

In this study, experimental and numerical investigations were carried out to achieve a comprehensive understanding of the impact of surface conditions on self-piercing riveting (SPR) joint quality. Oil lubrication and sandpaper grinding were employed in experimental tests to change surface conditions at rivet/top sheet, top/bottom sheets and bottom sheet/die interfaces. A finite element (FE) model for the SPR process was also adopted to numerically assess the impact of surface conditions. Variations in surface conditions were modelled by changing friction coefficients at contact interfaces. The results revealed that the friction coefficient between the rivet and top sheet (μ₁) imposed significant influences on the interlock (I₁) by affecting the deformation of the rivet shank and top sheet. The friction coefficient between the rivet and bottom sheet (μ₂) showed a lower influence on the joint quality because of a smaller contact area and shorter interaction time. The friction coefficient between the top and bottom sheets (μ₃) led to opposite changing trends of remaining bottom sheet thickness at the joint centre (t_c) and under the rivet tip (t_tip). The friction coefficient between the bottom sheet and die (μ₄) demonstrated crucial influences on the remaining bottom sheet at the joint centre. The riveting force was significantly influenced throughout the whole riveting process by the μ₁, but only affected at the end of the joining process by the other three friction coefficients. Full article

During the design of automotive structures assembled using Self-Piercing Rivets (SPRs), a rivet and die combination is selected for each joint stack. To conduct extensive physical tensile testing on every joint combination to determine the range of strength achieved by each rivet–die combination, a great deal of lab technician time and substrate material are required. It is much simpler and less material-consuming to select the rivet and die solution by examining the cross sections of joints. However, the current methods of measuring cross sections by measuring the amount of mechanical interlock in a linear X–Y direction, achieved with the flared rivet tail, do not give an accurate prediction of joint strength, because they do not measure the full amount of material that must be defeated to pull the rivet tail out of the bottom sheet. The X–Y linear interlock measurement approach also makes it difficult to rapidly rank joint solutions, as it creates two values for each cross section rather than a single value. This study investigates an innovative new measurement method developed by the authors called Volumelock. The approach measures the volume of material that must be defeated to pull out the rivet. Creating a single measurement value for each rivet–die combination makes it much easier to compare different rivet and die solutions; to identify solutions that work well across a number of different stacks; to aid the grouping of stacks on one setter for low-volume line; and to select the strongest solutions for a high-volume line where only one or two different stacks are made by each setter. The joint stack results in this paper indicate that there is a good predictive relationship between the new Volumelock method and peel strength, measured by physical cross-tension testing. In this study, the Volumelock approach predicted the peel strength within a 5% error margin. Full article

A vibration-damping steel panel is used for lightweight vehicles to block any noise subjected to the passenger cabin replacing heavy fiber-based insulators. Conventional weld joining methods often encounter problems due to the presence of viscoelastic compounds reducing the joint quality and making the joining process unproductive. In this work, we present experimental results that show the self-piercing riveting (SPR) process can be used to produce high-quality joints between vibration-damping steel and (i) commonly used steel alloy (SPFC590DP), (ii) carbon-fiber-reinforced-plastic (CFRP) panels. Various die shapes are used to investigate the resulting interlock width and bottom thickness of the joints and tensile shear load tests were performed to evaluate the joining strength. The results show that high-quality joints between vibration-damping steel and the steel alloy are possible for all the dye types and panel configurations, used in this study, producing up to 6.2 kN of tensile shear load. High-quality joints were also possible with CFRP producing up to 4.0 kN, however, acceptable joints were formed only when the CFRP panels were on top during the riveting process due to severe cracking. Full article

Self-piercing riveting (SPR) is a suitable technology to join various materials and has attracted more attention in the automotive industry. In this work, the effects of forming parameters on the forming qualities and mechanical properties of B1500HS steel/AA5052 aluminum alloy SPR joints were analyzed. The results show that the sheet stack sequence has little influence on the peak tensile load and rigidity of SPR joints. When the steel sheet is placed on the aluminum sheet, the failure displacement, energy absorption, and ductility factor are, respectively, 2.77, 2.13, and 2.28 times larger than those of the joints with the aluminum sheet placed on the steel sheet. The SPR joints with steel sheets placed on aluminum sheets have better mechanical stability. Meanwhile, when the steel sheet is placed on the aluminum sheet, the fatigue life of the joint can be increased by about 98.4%, 88.3%, and 118.1%, respectively, under high, medium, and low fatigue loads. A joint with opposite riveting direction has the optimal fatigue performance and the fatigue life is 1.64 and 2.14 times those of the other two-rivet joints. Generally, the fatigue fractures of aluminum alloy sheets in SPR joints occurred in fatigue tests. The fatigue fracture of a joint with a steel sheet stacked on an aluminum sheet extends uni-directionally to the edge of the sheet from the riveting point, while a symmetric fatigue crack of aluminum occurs for joints with the opposite sequence. The distribution of fatigue cracks is related to fatigue load, and fatigue cracks mainly originate in the fretting wear area of the contact interface between the rivet leg, upper sheet, and lower sheet. Full article

Double-sided self-pierce riveting (DSSPR) has been presenting itself as a proper alternative to self-pierce riveting (SPR) with many advantages for joining geometries of different thicknesses and cross-sections. To ensure its successful future industrial application, this paper presents a detailed comparison between different strategies to produce mechanical joints by means of the DSSPR process and discusses its performance and feasibility. Results show that the use of flat-bottom holes in both sheets provide interesting results, since they allow for a precise positioning of the tubular rivet in specific pre-defined locations, thus avoiding an incorrect joining procedure. This strategy tightens the tolerances of the process, while keeping a suitable level of destructive performance as demonstrated by the lap shear tests. Pre-riveting of the sheet has also been shown to produce suitable results in combination with or without a flat-bottom hole in the opposite sheet. This strategy comes at a cost of a slightly lower performance than that obtained with flat-bottom holes in both sheets, although the requirements of force and energy to complete the joining process are smaller. The conclusions of this research work are essential for selecting the joining strategy with DSSPR according to the requirements of the intended application. Full article

Self-piercing riveted (SPR) joints in automobiles inevitably suffer from corrosion damage and performance reduction. In this work, the influence of salt spray corrosion on the mechanical properties of TA1-Al5052 alloy SPR joints was studied. The TA1-5052 SPR joints were prepared and salt spray tests were carried out for different durations. The static and fatigue strengths of the joints after salt spray corrosion were tested to analyze the effect of salt spray duration on the performance of the joints. The results show that the joints’ static strength and fatigue strength decrease with prolonged salt spray time. The salt spray duration affects the joint’s tensile failure mode. The tensile failure without corrosion and with a short salt spray time is the fracture failure of the lower aluminum sheet, and the tensile failure of the joints after a long time of salt spray corrosion is the failure of the rivets. The fatigue failure form of the SPR joint is the formation of fatigue cracks in the lower aluminum sheet, and salt spray time has little effect on the fatigue failure form. Salt spray corrosion can promote the initiation and propagation of fatigue cracks. The fatigue crack initiation area is located at the boundary between the lower aluminum sheet and the rivet leg. The initiation of cracks originates from the wear zones among the sheet metal, rivets, and salt spray particles. Full article

This study reviewed some simplified methods of finite element analysis (FEA) for connections in cold-formed steel (CFS) structure, and summarized eight simplified methods divided into three categories. Shear performance tests were performed for six groups of self-piercing riveted (SPR) connection in CFS. A constitutive model of shear behavior for SPR connections was proposed, which was simplified from the load–displacement curve of shear performance test results. The models of SPR connection were established in ABAQUS by the eight simplified methods, and then the FEA results and the test results were compared. The applicable scope of each simplified model was explored, and a simplified method of FEA that was most suitable for the shear behavior of the CFS-SPR connection was proposed. Moreover, the shear performance test of the CFS shear wall with SPR was conducted by considering the rivet spacing, and failure modes and load–deformation curves were obtained. On this basis, numerical models of the CFS-SPR connection shear wall were established. By comparing the test results and the FEA results for the CFS-SPR connection shear wall, the feasibility of a simplified method of FEA applied to the CFS-SPR connection was verified. The main failure modes of the CFS-SPR connection were that the rivet tail pulled out from the bottom sheet and the rivet head pulled over from the top sheet. The SPR connection of the CFS frame could be simplified with a pin or a fastener element, and the SPR connection between the steel frame and the sheathing could be simulated by a Cartesian connector or a Spring2 element. The FEA results were highly similar to the test results for the CFS-SPR shear wall. Full article

During the self-piercing riveting (SPR) process, residual stress develops due to the high plastic deformation of the sheet materials. In this study, the effect of the residual stress on the fatigue lifetime of SPR joints with dissimilar magnesium AZ31 alloy and aluminum Al5052 alloy sheets was evaluated. The residual stress distribution was derived through a simulation of the SPR process by the FEA (finite element analysis). The measured values by the X-ray diffraction technique confirmed that the validity of the simulation has a maximum error of 17.2% with the experimental results. The fatigue strength of the SPR joint was evaluated at various loading angles using tensile-shear and cross-shaped specimens. It was found that the compressive residual stresses of the joint reduce the stress amplitude by 13% at 10⁶ cycles lifetime, resulting in extension of its lifetime to approximately 3.4 million cycles from 10⁶ cycles lifetime. Finally, it was confirmed that the fatigue life of SPR joints was appropriately predicted within a factor of three using the relationship between the fatigue life and the equivalent stress intensity factor. The fatigue resistance of the magnesium AZ31 alloy on the upper sheet was found to govern fatigue lifetimes of SPR joints of dissimilar magnesium AZ31 alloy sheets. Full article