## 2 Experimental Setup  
### Experimental Setup  
Figure 1 shows the schema of the experimental setup.  
As shown in Figure 1, a rotary UAD (1) set was clamped onto the three-jaw chuck (2) of a lathe machine. The drill bit (3) was clamped in a collet placed inside the rotary UAD. The aluminum workpiece (5) was fixed on a special fixture which can slide along the axial direction of the lathe spindle. The special fixture (6) had a shaft and bearings (7) constrained by a loadcell (8) permitting measure drilling torque. The feeding motion of the drilling process was implemented by means of static gravity from a preset mass (12) via a roller (11). Under the gravity load, the fixture carrying the workpiece tends to move towards the tool. At the beginning of each test, the static load was gently applied to the experimental sample until the sample contacted with the tool. The lathe was then turned on, the mass released, and the drilling process started. The workpiece displacement was measured by a linear displacement transducer (LVDT) (9). A loadcell (10) was arranged in a special way to measure the cutting torque. The signal from the loadcell was amplified by a signal conditioner (13). A noncontact infrared temperature sensor (4), model IRTP-300 LS, with a measuring range of 0-300 degrees Celsius was placed near the workpiece to capture the temperature of the workpiece. Data from the LVDT (9), loadcell (10), and temperature sensor (4) were collected by a data acquisition system (DAQ) (14) and then stored in a computer (15). Another computer (16) was used to control a power ultrasonic generator (17). A powered ultrasonic wave was then applied to the transducer inside the rotary VAD via a copper commutator brush (18).  
Figure 2 presents the construction of the experimental rotary UAD device. A commercial ultrasonic welding transducer including a proper horn and booster was fitted into a self-made steel tube and clamped at the node of the transducer. The horn was modified by making a hole to put a commercial collet inside. The drill bit was clamped inside the collet. Steady electrical impulses were supplied to the transducer via a copper brush which was positioned at the end of and rotated along with the lathe spindle. Using this arrangement, the drill bit simultaneously received both rotation (from the lathe spindle) and longitudinal vibration (from the transducer).  
Figure 1: Experimental schema.  
As mentioned above, the fixture used in this study was designed and fabricated in a special arrangement and thus can provide axial motion and allow us to measure drilling torque. This structure is illustrated in Figure 3.  
Figure 3: Technical schemata (**a**) in front view and (**b**) cross-sectional view, and (**c**) a photograph of the complete experimental fixture setup. (LVDT: linear variable displacement transducer.)  
Figure 2: A drawing of the rotary ultrasonic-assisted drilling (UAD).  
As shown in Figure 3a, the workpiece was clamped at one end of a shaft supported by a pair of rolling bearings. The shaft tends to rotate when a small amount of torque is applied to the workpiece. A loadcell was used as a barrier to prevent the rotational tendency of the shaft. The value of force acting on the loadcell was used to carry out the corresponding torque by multiplying the force value by the arm length. A spring support was positioned in the opposite side of the shaft in order to create an initial force on the loadcell as indicated in Figure 3b, thus keeping the loadcell always in contact with the shaft. The bearing support, loadcell, and spring support were placed on a thick steel plate. The plate was then fixed on a linear bearing slider. The slider was fixed on the lathe carriage.