Ultrasonic Cold Forging (UCF) is a technology that transforms a metal or metallic alloy surface microstructure to the nanostructure, utilizing ultrasonic vibration energy. It induces severe plastic deformation to the surface, by simultaneously applying static and dynamic force. As a result of this treatment, the mechanical properties of the metals and metallic alloys such as hardness, compressive residual stress, wear and fatigue characteristics are improved. In the present research, steps of designing a new UCF head to form nanostructured surface inside the cylinders and tubes are presented. The new design is developed by modal analysis of vibratory components. A UCF head consists of transducer, booster and horn. The transducer is an available module with a resonance frequency around 20 KHz. Hence, it is necessary to design a new booster and horn with resonance frequency adjacent the resonance frequency of the transducer. The results show that the frequency of the booster and horn, designed in this research are 20560 Hz in longitudinal vibration and 20608 Hz in transvers vibration. An integrated modal analysis for the whole UCF head is performed afterwards. It shows that the resonance frequency of the whole UCF head is 20512 Hz. A static analysis on the UCF head also shows that no static failure occurs, and static safety factor is about 5. In addition, the analyses show that when the tool is in the contact with the workpiece with the specified static load, the nodal point is moved about 5 millimeter in the longitudinal direction. Once the tool is designed and manufactured, it is installed on the lathe machine, and is used to treat the inside surface of an Al 6061-T6 cylindrical tubular specimen. practical improvements of the mechanical properties of the specimen and its microstructure are examined by some mechanical and metallurgical tests, including micro hardness test, wear test and observing the microstructure of the specimen by optical microscope and scanning electron microscope. The results show an increase in the hardness of the surface by about 82.4% , from 63.6 to 116 vickers, where this hardness improvement has continued until the depth of about 400 microns. The friction coefficient reduces by 28.4% , from 0.35 to 0.25 and the amount of metal wear decreases from 8.3 to 7.8 milligrams. The observation of microscopes shows a severe turbulence near the affected surface. It also shows that the work-hardening and elongation of grains happens in the direction of the feed and spindle speed. To some extent the reduction of grain size from an average of 70 micron to 1 micron can also be observed Key Words: UCF Head, modal analysis, vibration, Al 6061-T6, hardness, wear, microscope
