狼尾草草莖剪切力量及剪切衝量之研究

The Study of Shear Force and Impulse for Napiergrass Stem

連振昌(Cheng-Chang Lien) ； 洪滉祐(Huaang-Youh Houng) ； 艾群(Chyung Ay)

《農業機械學刊》 13卷2期 (2004/06) Pp. 39-50

https://doi.org/10.30062/JAM.200406.0004

摘要

本研究使用一衝擊式的剪切裝置，模擬狼尾草草莖切斷時的剪切狀況，由衝擊剪切試驗得到牧草莖的力量─時間曲線，計算出其單位面積剪切力量及剪切衝量；量測狼尾草草莖的含水率，改變不同的刀刃角度及剪切速度，由力量─時間圖的差異，分析剪切破壞的過程，探究其對狼尾草草莖剪切時的單位面積剪切力量及剪切衝量的影響，以做為狼尾草草莖收穫時之參考依據。由試驗資料及結果分析顯示：狼尾草草莖的表皮在剪切破壞的過程有顯著地影響；在草莖含水率89.5%條件下，以不同的刀刃角θ(°) 和剪切速度V(m/s)進行試驗，得到單位面積剪切力量τ(subscript m)(N/cm2)對刀刃角和剪切速度V多重迴歸方程式， τ(subscript m)=-170.35+4.70θ +58.24 V；決定係數R2=0.932；標準偏差S=18.15 (N/cm2)；刀刃角20~40°間對單位面積剪切衝量I(subscript m)並無顯著影響，但在50°刀刃角θ下，單位面積剪切衝量I(subscript m)急劇增加，且被切斷的狼尾草草莖呈現破裂及切斷面參差不齊。

關鍵字

狼尾草 ； 剪切力量 ； 剪切衝量

並列摘要

An impulse-cutting device was developed in this study to simulate the shear state while cutting Napiergrass stem. The force-time curve was obtained through the impulse-cutting tests of Napiergrass stem. All experiments were conducted to calculate the shear force and shear impulse per unit area. The moisture content of Napiergrass stem, different the bevel angles and shear velocity of the blade were measured in order to analyze what differences in the force-time curve and the level of destruction during the shear cutting process. Furthermore, the influence of the shear force and shear impulse per unit area on cutting Napiergrass stem was investigated; the result could be used as a guide for harvests of Napiergrass stem in the future. According to the experiment and analysis results, the condition of periderm of the grass was remarkably affected in the shear process. When the moisture content of Napiergrass stem is at 89.5%, the formula is τ(subscript m)=-170.35+4.70 +58.24 V, determination coefficient R2=0.932 and standard deviation S=18.15 (N/cm2) . Where τ(subscript m) (N/cm2) is the shear force per unit area, θ(°) is the bevel angle, and V (m/s) is the shear velocity of the blade. The shear impulse per unit area did not vary significantly with the bevel angle from 20° to 40°. However, the shear impulse per unit area did increase rapidly at an bevel angle of 50°, the stem also showed uneven and ragged fracture at the cross-section.

並列關鍵字

Napiergrass stem ； Shear force ； Shear impulse