Aluminum alloy sheets have been widely used to build the thin-walled structures by mechanical clinching technology in recent years. However, there is an exterior protrusion located on the lower sheet and a pit on the upper sheet, which may restrict the application of the clinching technology in visible areas. In the present study, an improved clinched joint used to join aluminum alloy sheets was investigated by experimental method. The improved clinching process used for joining aluminum alloy evolves through four phases: (a) localized deformation; (b) drawing; (c) backward extrusion; and (d) mechanical interlock forming. A flat surface can be produced using the improved clinching process. Shearing strength, tensile strength, material flow, main geometrical parameters, and failure mode of the improved clinched joint were investigated. The sheet material was compressed to flow radially and upward using a punch, which generated a mechanical interlock by producing severe localized plastic deformation. The neck thickness and interlock of the improved clinched joint were increased by increasing the forming force, which also contributed to increase the strength of the clinched joint. The improved clinched joint can get high shearing strength and tensile strength. Three main failure modes were observed in the failure process, which were neck fracture mode, button separation mode, and mixed failure mode. The improved clinched joint has better joining quality to join aluminum alloy sheets on the thin-walled structures.

In recent years, the use of aluminum alloy has tended to increase for building lightweight automobiles to reduce their automotive weight, which is helpful to save energy and protect the environment. In order to join aluminum alloy, a flat-clinching process combined with material forming technology was investigated to join aluminum alloy sheets using an experimental and a numerical method. Al1060 was chosen as the material of the sheet, and DEFORM-2D software was used to build the numerical model. After the numerical model was validated by the experimental results, the influences of punch diameter and holder force on the materials deforming behavior of the clinched joint were analyzed using the numerical model. Then, the material flow, joining ability, and joining quality were investigated to assess the clinched joint. The results showed that an increase in punch diameter could give rise to an increase in neck thickness and interlocking length, while an increase in blank holder force induced a decrease in interlocking length and an increase in neck thickness. The joining quality could be increased by increasing the forming force. It can be concluded that a clinched joint has better joining quality for joining light-weight sheets onto automotive structures.

The electrical driving system is crucial to the performance of electric vehicles (EVs). It is problematic for an in-wheel motor (IWM) driven by a single motor to satisfy certain dynamics requirements or to remain highly efficient at full operating conditions. In this paper, a novel IWM driving system driven by two permanent magnet synchronous disc motors (PMSDMs) with a planetary differential gear train (PDGT) is put forward. The PMSDMs are designed based on the parameters and dynamic indicators of the vehicle. Thereafter, the PMSDMs are optimized from aspects of the rotor skewing angle and pole arc coefficient and verified by finite element analysis (FEA). Then the characteristic coefficient of PDGT is optimized through non-dominated sorting genetic algorithm II (NSGA-II) combined with dynamic programming (DP). The economic performance improves by $5.0\%$ and dynamic performance improves by $4.4\%$ with the characteristic coefficient optimized from 3 to 1.65. Meanwhile, the economic performance of the novel dual-motor IWM shows significant improvement compared to the traditional single-motor IWM in simulation. Furthermore, a prototype is developed and tested. Both the simulation and experimental results reveal the feasibility and effectiveness of the proposed novel IWM driving system.