Joining Process for Plates Using Plastic Deformation with Rotating Tool and Pilot Hole

AbstractA new joining method using plastic flow has been developed. In this method, a tool with a shoulder and drill-shaped tip is used. This tip rotates and plunges into the workpieces until the shoulder of the tool touches the plate surface. The rotating tool drills a hole through the workpieces and deforms into a rivet shape, so the two plates are joined without preprocessing such as drilling a rivet hole. Therefore, this method is considered to have a decreased number of processes. However, it is difficult to drill a pilot hole with a tool made of metal that is easy to deform, such as aluminum alloy. Therefore, in this study, a pilot hole was drilled into the workpieces before using the tool. This method was used to make lap joints, and the joint strength of the joined aluminum alloy plates was investigated using a tensile shear test. In all cases, the tool plunge rate was kept constant at 1.2mm/min, and the tool rotational speed was set to 766 r/min. A tool plunge depth of 7.0mm below the upper plate surface was used. The tool, which is made of aluminum alloy (AA7075-T6), has a shoulder diameter of 10.0mm, a cylindrical tip diameter of 3.0mm, and a length of 7.0mm. The pilot hole was drilled to a diameter of 3.0–3.6mm. As a result, the tip of the tool softens by frictional heat and deforms by compressive loading and shear force. The maximum tensile shearing loads of all the samples in this study were more than 2.5kN, so all of the samples can be joined with high strength