Analysis of welding properties using various horn-tip patterns in the ultrasonic metal welding process

The present study was conducted to investigate how the characteristics of welds are affected by the horn-tip pattern shape, in order to assess how to efficiently transfer the vibration energy to a base material through the horn. Energy transfer was evaluated using the indentation marks. The experiment was carried out with aluminum and copper by combining the conditions from four horn-tip patterns, six pressure values, and ten welding time values. The aspect ratio of the indentation marks on the weld surfaces was measured. The effects of the applied pressure, welding time, and horn-tip pattern shape on the aspect ratio were analyzed, and it was found that the horn-tip pattern shape affects the aspect ratio significantly. The aspect ratio was suggested as an analytical reference, and its correlations with the shear strength and the hardness of the welds were verified. In addition, the experiment performed with aluminum and copper, which have different mechanical properties, under the same welding conditions showed that the aspect ratio was dependent on the mechanical properties of the materials. In conclusion, as the density of the horn-tip pattern is decreased, less of the vibration energy was lost, increasing the strength of the welds. Experimental results showed that shear strength of copper was nearly 400 N when the aspect ratio was close to the value of 1. The highest peak of horn-tip pattern forms the lowest aspect ratio of the indentation mark, which can be indicated that the decrease of the aspect ratio effect to the improvement of welds strength. Aspect ratio of horn-tip pattern D, which dimensions are pitch 1.5 mm, height 0.75 mm and stub tooth 0.7 mm was closely to the value of 1 compared to the other patterns