42.为什么铧刃在犁耕中会出现背棱? 犁耕时,铧刃切开土垡并使之升起,在这个过程中,土壤中许多带有尖锐棱角的石砾,砂粒和粘粒,好象切削刀具一样将铧刃上的金属一点一点切削下来,形成许多的沟痕。随着磨损量的增加,铧刃逐渐变钝,铧宽逐渐变窄(图1)。 42. Why does the blade appear to have a dorsal edge during plowing? During plowing, the blade raises and lifts the soil, during which time many of the rock’s sharp gravel, sand and clay , As if the cutting tool to cut the metal on the Hua blade little by little, forming a lot of groove marks. As the amount of wear increases, the blade becomes dull and the width of the cut becomes narrower (Figure 1).