关键词: 油茶苗嫁接, 力学特性, 剪切强度

Abstract:

Objective: This study aims to investigate the mechanical characteristics of Camellia oleifera (oil tea) seedlings to address issues such as excessive clamping force leading to seedling damage and excessive cutting force causing scion seedlings to slip during the mechanized grafting process, providing references for the design and optimization of automated grafting equipment for oil tea. Method: The “Changlin Series No. 53” oil tea seedlings were used as the research object, the main physical characteristics of rootstock seedlings were obtained by measuring physical parameters and performing statistical data analysis. Based on grafting technology standards, two types of seedlings (rootstock and scion) were divided into three groups for radial compression test and three-point bending test. Shear tests on both rootstock and scion seedlings were performed using the Box-Behnken experimental design method, and the influence of tool edge angle, loading speed, and seedling diameter on shear strength was analyzed using response surface methodology. Result: The diameter range of rootstock seedlings was 2.72–4.48 mm, with an average diameter of 3.16 mm, an average mass of 2.34 g, and an average moisture content of 80.12%. The diameter range of scion seedlings was 2.03–3.50 mm, with an average diameter of 2.75 mm, an average mass of 1.84 g, and an average moisture content of 81.34%. The average peak compressive force and maximum compression of rootstock seedlings were 139.4 N and 0.78 mm, respectively. For scion seedlings, these values were 198.1 N and 0.70 mm. The average peak bending force, bending elasticity modulus, and bending strength of rootstock seedlings were 8.24 N, 29.007 MPa, and 8.168 MPa, respectively. The average peak bending force, bending elasticity modulus, and bending strength of scion seedlings were 8.20 N, 23.346 MPa, and 18.497 MPa, respectively. The average shear strength of rootstock and scion seedlings was 1.445 MPa and 3.025 MPa, respectively, with their maximum shear forces of 24.65 N and 24.83 N. Seedling diameter and tool edge angle significantly affected shear strength, while loading speed had no significant impact. Conclusion: The results of the radial compression test indicate that the peak compressive force, maximum compression, and compressive strength of both rootstock and scion seedlings increase with the diameter, with the compressive strength of scion seedlings being higher than that of rootstock seedlings. The results of the three-point bending test show that the peak bending force of both rootstock and scion seedlings increases with diameter, but the bending strength of rootstock samples is generally lower than that of scion samples, and the brittleness of rootstock samples is greater than that of scion samples. The shear test results indicate that the shear strength of rootstock decreases as the tool edge angle decreases, while it increases with the diameter of the rootstock. The shear strength of scion seedlings gradually decreases as the tool edge angle decreases, and shows a trend of first slight decrease followed by rapid increase with increasing scion diameter. The shear strength of both types of seedlings initially decreases and then increases as the loading speed increases. Additionally, the clamping force applied to scion seedlings should range between 100 and 150 N, while the clamping force on rootstock seedlings should not exceed 90 N.

Key words: Camellia oleifera grafting, mechanical properties, shear strength