Jia Bai

To address the practical requirement for controllable wettability design of additively manufactured nickel-based superalloy surfaces, this paper systematically examines how laser processing techniques influence and regulate their wettability. Using a full factorial design combined with analysis of variance (ANOVA), we investigated how laser power, scanning speed, and spot diameter affect groove morphology at different scanning pitches and quantitatively assessed the main and two-way interaction effects of these parameters on wettability. To elucidate the intrinsic “laser parameters–surface morphology–wetting behavior” relationship, we adopted a progressive characterization approach, advancing from static water contact angles (WCAs) and contact angle hysteresis (CAH) to dynamic droplet bouncing behavior. The results indicate that: (1) Under the premise of forming stable grooves, increasing laser power, decreasing scanning speed, or reducing spot diameter promotes the formation of deep and narrow grooves, thereby enhancing the WCA (up to 158.8°) and reducing CAH (as low as 3.7° on engineered wedge structures). (2) CAH is identified as the key parameter characterizing dynamic droplet bouncing performance since lowering CAH effectively results in low adhesion and easy droplet shedding. (3) The WCA and CAH exhibit different sensitivity patterns to parameter coupling; consequently, parameter mismatch can lead to morphological degradation and loss of hydrophobicity, making multi-parameter synergistic optimization essential for maintaining highly stable surface hydrophobicity. This paper provides practical guidance for the surface functional design of additively manufactured superalloy components, holding significant application value for engineering surfaces in aerospace, energy, and other fields that require controllable droplet shedding, anti-icing, and self-cleaning properties.

To investigate the biomechanical performances of artificial cervical disc (ACD) prostheses, many studies have been conducted, either with cervical sections of cadavers under physiological loads or with block-like testing fixtures obeying the ASTM F2346 standard. Unfortunately, both methods are almost impossible to utilize for accurate results of lifetime anti-fatigue experiments for at least 10 million cycles due to the difficulties in cadaver preservation and great deviations of natural cervical bodies, respectively. Based on normal human cervical structural features, a novel specimen fixture was designed for testing the fatigue behavior of ACD prostheses under flexion, extension, and lateral bending conditions, with aspects of both structural and functional bionics. The equivalence between the biomimetic fatigue-testing fixture and the natural cervical sections was investigated by numerical simulations and mechanical experiments under various conditions. This study shows that this biomimetic fatigue-testing fixture could represent the biomechanical characteristics of the normal human cervical vertebrae conveniently and with acceptable accuracy.