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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.

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HighlightsBasic physical properties and mechanical parameters related to moisture content and compression orientation.A discrete model of cabbage seed was established by discrete element method.Crushing simulation has high consistency and small deviation compared with physical experiment.Abstract. To reduce the mechanical damage to cabbage seeds during combined harvesting, storage, and processing and to explore the mechanism of grain breakage, the basic physical parameters, such as the 1000-grain weight and the triaxial size under different moisture content (6.38%~15.30%), and the compressive mechanical properties under different loading methods (ventral loading and lateral loading) were studied. The discrete element method was used to establish a BPM model of cabbage seed. The distribution law underlying macroscopic cracks, evolutionary mechanism of internal damage and the micromechanical response during the compression of cabbage seeds were simulated. The results showed that the triaxial size, 1000-grain weight, arithmetic mean diameter and geometric mean diameter of cabbage seeds were related to the moisture content. The crushing force and apparent elastic modulus were related to the moisture content and the loading method. The distribution law of macroscopic cracks during the simulation processing was consistent with the physical experiment, and it was accompanied by increases in cracks and changes in the internal stress. In comparing the crushing force-displacement curves under the two compression modes, the law of curves between physical and virtual experiments was similar, and the peak values were very close, which indicated the feasibility of using the discrete element method to simulate the crushing of cabbage seeds during the compression process. Keywords: Cabbage seeds, Compression test, Cracks, DEM, Stress.