The effect of Ce on the microstructure, mechanical properties and corrosion resistance of 27Cr-3.8Mo-2Ni super-ferritic stainless steel were investigated by FactSage 7.2. The results reveal that when the Ce content increases from 0.00 wt-% to 0.0498 wt-%, Al₂O₃ inclusions wrapped by irregular (TiNb)N are gradually modified into spheroidal CeAlO₃, Ce₂O₃, Ce₂O₂S and Ce-O-P complex inclusions, the rare earth inclusions are smaller than 1.0 × 10⁻⁶ m (1.0 μm) and dispersedly distributed. The diameter of recrystallized ferrite grain is decreased, the mechanical properties of super-ferritic stainless steels are well improved, impact fracture appearance transforms from pre-dominant cleavage to ductile fracture at 298 K (25°C), and the cleaving step of the fracture becomes smaller at 243 K (−30°C), the uniform corrosion resistance to H₂SO₄ of steels with is enhanced especially in 40 vol.-% H₂SO₄ at 333 K (60°C). In addition, the microstructure and properties could not be further improved with 0.0744 wt-% Ce content.

A novel sensing and actuating integrated ultrasonic burnishing device (SAIUBD) through only one longitudinal ultrasonic transducer is presented. The sensing and actuating functions are achieved simultaneously by the SAIUBD that improves the burnishing precision and efficiency. Above all, the structure and working mechanism of the SAIUBD is amply depicted. Then, the structure size, sensing, and actuating parameters are designed through simulation analysis. Ultimately, the prototype is fabricated, and the piezoelectric self-sensing calibration and burnishing tests are presented. Testing results show that the steady-state error of ±0.287 μm is achieved based on piezoelectric self-sensing, which means precision sensing and controlling of the burnishing amplitude without external sensors are achieved. Furthermore, the surface burnished by the SAIUBD achieves Ra 0.116 μm, and the precision and efficiency have been improved by 36.3% and 50% compared to the traditional burnishing. The above results indicate that the novel SAIUBD has enormous advantages in improving burnishing precision and efficiency, which has great application potential in ultra-precision machining.

The attenuation and fluctuation of ultrasonic vibration amplitude caused by the change of cutting load have become crucial factors limiting the precision improvement of the 2D ultrasonic-assisted turning (2DUAT). Therefore, the precise control of ultrasonic amplitude is very critical for 2DUAT precision improvement. However, it is difficult to arrange external sensors since the contact between the tool and the workpiece. Here, a novel 2D sensing and actuating integrated ultrasonic turning tool (2DSAIUTT) is proposed. The sensing and actuating of 2D amplitude are realized simultaneously with a single longitudinal-bending hybrid transducer without external sensors. First, the structure of 2DSAIUTT is designed and its open-loop characteristics are tested. Then, a negative feedback decoupler is proposed to overcome the coupling between the longitudinal and bending self-sensing signals, by which the self-sensing error is reduced by 70.1%. Finally, a cutting experiment under variable depth-of-cuts (DOCs) is carried out. The results show that the amplitude control error under variable DOC load is less than ±0.156 μ m. Moreover, the precision is 70.8% higher than that of traditional 2DUAT, and the surface roughness of stainless-steel turning reaches Sa0.127 μ m. These advantages show that 2DSAIUTT has great potential in the field of ultra-precision machining.

This study investigates the development of biomimetic sound-absorbing components through laser sintering technology, drawing inspiration from wood’s natural porous structure. Using a pine wood powder/phenolic resin composite, various specimens were fabricated with different structural configurations (solid, fully porous, and varying straight-pore ratios) and cavity thicknesses. Sound absorption performance was evaluated using the impedance tube transfer function method. The effect of different composite structures, placement orientations, and cavity thicknesses on sound absorption performance was evaluated. The results demonstrate that solid laser-sintered samples exhibit inherent sound absorption properties due to microscopic pores, with absorption coefficients exceeding 0.234. The biomimetic wood-like structure, featuring multi-scale porosity at both microscopic and mesoscopic levels, shows enhanced broadband sound absorption, particularly in mid-high frequencies, with characteristic double-peak absorption curves. The study reveals that absorption performance can be optimized by adjusting structural parameters and thickness, enabling targeted frequency-specific sound absorption. This research establishes the feasibility of creating multi-frequency sound-absorbing materials using laser-sintered biomimetic wood structures, providing a foundation for future applications and development in acoustic engineering.

A novel compact tripodal bonded-type miniature piezoelectric robot (TBMPR) combining large-load capacity and high-speed was designed. Each leg was fabricated by a bonded-type piezoelectric cantilever beam which could be excited in the first order bend modal for compact structure and efficient exciting. A design method based on finite element analysis and dynamic modeling of the TBMPR was built with the rule of maxim amplitude output. Modal and harmonic response analyses were carried out to determine the optimal vibration modal and resonant frequency of the TBMPR. Finally, a prototype with a total dimension and weight of 43 × 37 × 27 mm³ and 2.7 g was fabricated, and the testing experiments were being conducted. The results showed that the linear speed of 3.3 mm/s, the rotational speed of 2.6° s⁻¹ and the maximum load of 5.5 times of its own weight were achieved simultaneously. Thus, the major novelty of the proposed tool was that large-load, high-speed and compact structure could be simultaneously achieved within the proposed TBMPR. These merits make the TBMPR has significant potential for detection in confined spaces.