Piercing injury and pulling-out mechanical properties of garlic scapes based on X-ray CT

To resolve the problems of low operational efficiency and high plant injury rate in mechanized garlic scape harvesting, this study systematically investigated the interfacial mechanical and mechanical damage characteristics of garlic scapes during the pulling-out process. Basic mechanical properties of garlic scapes, including tensile, compressive, bending and shear behaviors, were first measured to clarify the inherent mechanical basis for interfacial mechanical and injury evolution. Pulling-out mechanical tests of garlic scapes were subsequently conducted utilizing three types of working tools to explore the interfacial mechanical response between tool and garlic scape during harvesting operation. Meanwhile, X-ray CT scanning technology was adopted to qualitative characterize the internal piercing damage of garlic scapes induced by tool extrusion and mechanical contact. The test results indicated that the tensile strength and fracture displacement of garlic scapes exhibited a gradual decreasing trend from the apical segment to the basal segment. Increasing tensile speed further improved the tensile strength and fracture displacement of garlic scapes while shortening the fracture duration. Additionally, the compressive, bending and shear resistance of garlic scapes all declined progressively from the top to the base, revealing distinct spatial heterogeneity in mechanical and mechanical adaptability. Comparative mechanical test results demonstrated that the conical tool achieved the highest pulling-out success rate in tool-scape interfacial mechanical operation, yet accompanied by relatively severe internal piercing damage to garlic scapes. Differences in pulling-out performance among the piercing tools may be attributed to the combined effects of piercing height, local tissue properties, pseudostem confinement, and tool-tip geometry. The clarified interfacial mechanical laws and damage mechanisms in this study can provide a fundamental theoretical basis for the optimal design of clamping, piercing and pulling-out mechanical matching devices for high-efficiency and low-damage garlic scape harvesters.