This paper presents a development in design, mathematical modeling, and experimental study of a vibro-impact moling device, which was invented by the author before. A vibratory unit deploying electromechanical interactions of a conductor with oscillating magnetic field has been realized and developed. The combination of resonance in an RLC circuit including a solenoid is found to create a relative oscillatory motion between the metal bar and the solenoid. This results in impacts of the solenoid on an obstacle block, which causes the forward motion of the system. Compared to the former model which employs impact from the metal bar, the improved rig can offer a higher progression rate of six times when using the same power supply. The novel geometrical arrangement allows for future optimization in terms of system parametric selection and adaptive control. This implies a very promising deployment of the mechanism in ground moling machines as well as other self-propelled mobile systems. In this paper, insight to the design development based on physical and mathematical models of the rig is presented. The coupled electromechanical equations of motion then are solved numerically, and a comparison between experimental results and numerical predictions is presented.

In this paper, the influence of ultrasonic vibration on the forming forces and surface quality of products formed using an ultrasonic-assisted incremental sheet forming (UISF) method was investigated and compared with an incremental sheet forming (ISF) method. The elements and parameters used for research include a sheet of Al 5052 aluminum alloy with thickness of 1.0 mm, a lathe with a feed rate of 70–130–225 rpm, and step size of 1.0–1.5–2.0 mm. The results show that ultrasonic vibration significantly reduces the forming forces, of which the main forming force F_zmax is reduced by about 20%. Besides, the results also show that the surface quality of products formed via UISF is significantly improved compared to that formed by ISF.

Implementing the ultrasonic vibration-assisted incremental sheet-forming (UISF) process has been proven to significantly reduce the forming force, improve the surface quality, and enhance the accuracy of the sheet-forming process. However, such effectiveness has primarily focused on easily deformable materials (such as AA1050 and AA1060 aluminum alloys) and small step-down sizes (from 0.3 mm to 0.5 mm). To further enhance the process, it is crucial to study larger step-down sizes and harder materials. In this study, a series of UISF experiments were conducted, with step-down sizes ranging from 0.5 mm to 1.5 mm and feed rates ranging from 200 mm/min to 1200 mm/min. The influence of ultrasonic vibration on the effectiveness of force reduction and the optimal operation parameters was experimentally tested. Forming aluminum alloy AA5052, a difficult-to-deform material with two thicknesses of 0.5 mm and 1.0 mm, indicates that the axial force Fz and the tool movement resistance force Fy tend to decrease significantly with ultrasonic vibration assistance. Optimal equations for force reduction Fz and Fy have been developed for plate thickness based on the step-down size and feed rate. The optimal results show that for 1.0 mm thickness, reductions in Fz and Fy can reach 58.73% and 69.17%, respectively, and that of 64.17% and 71.98%, respectively, for 0.5 mm thickness.

The ultrasonic vibration-assisted incremental sheet forming (UISF) process already indicates its potential in reducing forming forces and increasing the material formability. However, most of previous studies focused on easy-to-deform materials (e.g., Al 1050 and Al 1060 aluminum alloys). It is necessary to investigate its effectiveness with harder materials to further understanding this process. The experiments conducted in this work employed the UISF process with a 0.5 mm step depth size, and the high feed rates vary from 1200 mm/min to 2400 mm/min to form truncated cones with a wall angle of 45°, a depth of 20 mm, and thicknesses of 0.5 mm and 1.0 mm. The effect of feed rates on the reduction in component force was experimentally investigated, as well as the distribution of wall thickness after forming process with and without ultrasonic vibration. The results show that ultrasonic vibration not only reduces deformation force but also contributes to more uniform plate thickness distribution.