“…The vibration direction can be either normal [11][12][13][14]16,23,24] or tangential [3,15,[17][18][19][20] with respect to the contact surface. This effect can be used for the reduction of process force in manufacturing processes, such as ultrasonic machining and ultrasonic-vibration drawing [9], or solving the problem of position control in high vacuum environments, such as electron microscopes, where friction can be controlled through the variation of the vibration amplitude only.…”