Why do you use scissors to cut your nails? Why do you cut them with nails instead of cutting them?
So, whether shear, the three necessary conditions are: one pair of equal size, the opposite direction, the action line distance is very close.Carefully observe the scissors and Nail Clippers will know: two blade scissors no longer on a horizontal plane, so the nails when, because of the effects of line two blades in a plane, and the distance is very near, so is the shear.The two edges of the nail clippers are in a vertical plane, so they do not satisfy the third conditions of the shearing stress, so it is not a shearing phenomenon.
Under the action of such external force, the deformation characteristics of the member are that the cross section of the two force is the boundary line, and the two part of the member is relatively deformed along the plane. This deformation form of a component is called shear, and its cross section is a shear plane.
In simple terms, the shear phenomenon requires shear stress, i.e., there are two opposite directions of stress at one side of the plane. The resultant forces of the external forces used on the two sides of the component (nail) are transverse forces of equal magnitude, opposite directions, and very close lines of action.
