Optimal Design and Experimental Verification of Ultrasonic Cutting Horn for Ceramic Composite Material  
[PERSON]  
1 School of Mechanical Engineering, Hanyang University, Seoul 04763, Korea; [EMAIL_ADDRESS] (M.  
smaller pieces. However, the block-type cutting horn is only used for cutting and splitting of soft materials such as rubber, plastic and foodstuffs, not hard material. The main reason is that the block-type ultrasonic horn and blade are made of a single material such as titanium, aluminum, and stainless steel to increase their high wear resistance, high Q-factor and good acoustic characteristics [8]. Therefore, this monolithic structure with ultrasonic material has lower hardness than tungsten carbide or tool steel, which are commonly used as a tool tip. This limitation can be overcome by developing a horn with ultrasonic material and a blade with high hardness material and combining them to expand the application area of ultrasonic cutting machines to cut hard material.  
Many researchers have investigated the ultrasonic cutting mechanism of block-type horns using an analytical method. [PERSON] et al. studied the reduction of the cutting force of several workpieces according to the working conditions of block-type ultrasonic cutters [11]. [PERSON] et al. developed a finite element model for ultrasonic cutting of a single and double layer model [12]. [PERSON] et al. investigated the ultrasonic cutting of laminated paper using a dynamic model and calculated the cutting force [13]. However, these studies focused on the characteristics of the block-type cutter according to the ultrasonic cutting process or working conditions, and the effect of the geometric characteristics of the horn was not analyzed. Some researchers have studied the characteristics of ultrasonic cutters with respect to the geometry of ultrasonic horns. [PERSON] et al. added small slots to an ultrasonic horn and analyzed the effect of the small slots on the frequency isolation and vibration uniformity, [PERSON] et al. further considered the thickness of the horn as a design variable to analyze the frequency characteristics of the horn [14; 15]. [PERSON] et al. studied the displacement, stress, and heat specification of various horns with different cross-sectional shapes through experimental and analytical methods, and [PERSON] et al. developed a horn with a B-spline cross-sectional shape and further investigated its characteristics [16; 17]. In addition, many researchers have investigated the displacement and frequency characteristics of various ultrasonic machines considering the geometrical characteristics of the horn, but it was a single-material ultrasonic horn and blade, and they did not even consider the various geometrical design variables simultaneously [7; 18; 19; 20; 21; 22; 23; 24; 25; 26].  
In this study, we proposed an optimal block-type ultrasonic cutter with dissimilar material that combines an aluminum horn with a tungsten carbide blade in order to cut hard materials as well as soft materials. We designed an initial ultrasonic block horn, developed a finite element model of the initial model and analyzed the characteristics of its natural frequency and displacement. We formulated a multi-objective optimal design problem of the ultrasonic block horn to maximize the amplitude uniformity and frequency separation to ensure cutting performance. We calculated the optimal design problem  
Figure 1: (**a**) A block-type ultrasonic cutting machine and (**b**) a sonotrode.  
and proposed an optimal block-type ultrasonic horn and also performed the sensitivity analysis to analyze the correlation between many design variables and characteristics of the ultrasonic horn. We fabricated the proposed optimal block horn and verified it experimentally. An ultrasonic cutting experiment was conducted to find the ultrasonic cutting force with hard ceramic composite materials. A cutting test with a conventional cutting machine under the same conditions was also conducted to compare the cutting force and the cutting surface.