Friction plug repair welding of glass fiber-reinforced polyamide 6: Investigation of morphology, microstructure, and mechanical properties

Abstract

Friction plug repair welding technology has been demonstrated to be effective to repair the glass fiber-reinforced polyamide 6 sheets in the present paper. Influences of repair hole geometries and parameters on joint morphology and mechanical performance were investigated. Results showed that defect-free repaired joints were produced with the utilization of tapered holes rather than cylindrical holes. Process parameters exerted significant influences on the cross-sectional profile and morphology of the joints. Defect-free repaired welds with larger stir zone thicknesses were produced with the proper increase of rotational speeds, but excessive rotational speeds caused the formation of cavities along the plug boundary and the reduction of stir zone thicknesses. The fluctuation of the wavy bottom interface increased under larger plunge rates and incomplete connections between stir zone and base material were observed under plunge rate of 25 mm/min. Extended dwell time led to larger stir zone thickness and improved joint morphology. Tensile tests showed that the strength of the repaired joints increased and then decreased with the enlargement of rotational speeds. Decreased plunge rate and extended dwell time led to promoted joint mechanical performance. Three failure modes were observed, which corresponded to low, middle, and high repaired weld strengths.

The Effect of Plug Rotation Speed on Micro-Structure of Nugget Zone of Friction Plug Repair Welding Joint for 6082 Aluminum Alloy

“…Stirring needle extraction technology can eliminate the keyhole [ 18 ], but it reduces the effective bearing thickness of the joint. The British Welding Institute invented the friction plug repair welding technology of top forging [ 19 ], which can realize the repair of “keyhole” defects in the fusion welding and friction stir welding of high-strength aluminum alloy materials, which were difficult to repair by traditional fusion welding. In order to replace manual TIG welding, this technology was introduced in the United States for repair welding of space external tanks [ 20 ]; the parameters were optimized by Lockheed Martin and the Marshall Flight Center.…”