In order to investigate the dynamic process of calculi ablation by holmium(Ho) laser and its collateral damage to the surrounding tissues, various model experiments were conducted on artificial gelatin-gypsum samples, along with a homemade holmium laser device. The experimental parameters included the laser energy, the fiber diameter, and the distance between the fiber and the artificial calculi. High-speed shadow graphs showed that an hourglass-shaped bubble would occur in gelatin during the ablation, and a discussion was provided on the morphology evolution mechanism of hourglass-shaped bubbles under different loading conditions. Characterizations on the recovered samples were carried out via optical imaging and scanning electron microscope. The results revealed that gelatin tissue undergoes damage from erosion, cavitation, and fragments jetting of artificial calculi. The ablation crater shows two kinds of morphology on its side face and subface with different roughness due to different material failure mechanisms. Geometric parameters of the ablation crater were obtained using the white-light interferometry technique, along with discussions on the effects of loading conditions. Energy analysis was given on the ablation process, and a linear relation between crater volume and laser energy was evaluated.

Aviation metal structures often face the combined effect of Marine corrosion environment and repeated impact loads during service, which leads to corrosion damage on the material surface and significantly deteriorates its impact fatigue performance. In order to explore this phenomenon in depth, this paper systematically studied the impact fatigue life of AerMet100 steel and TC18 titanium alloy, the key structural materials in the aviation field, under different durations of neutral salt spray corrosion. The impact of corrosion duration on the impact fatigue life of two types of notched three-point bending specimens and the damage mechanism were systematically revealed by the neutral salt spray corrosion test, the dropping hammer impact fatigue life measurement test, and the scanning electron microscope (SEM) characterization technology. The results show: with the increase of salt spray corrosion time, the fatigue life of U/V-90° notched specimens of AerMet100 steel and TC18 titanium alloy U-notched specimens show a nearly linear decay trend, and the fatigue life of AerMet100 steel decreases to about 50% of that of non-corroded specimens after 240 h of corrosion. However, the U-notched specimen of TC18 titanium alloy decreases to about 50% of the uncorroded specimen after 480 h of corrosion. In contrast, the fatigue life of the V-90° notched specimen of TC18 titanium alloy is mainly affected by the stress state rather than the corrosion damage due to the high stress triaxial degree at the notch location. In addition, the SEM results show that with the extension of corrosion time, the number of corrosion products and pitting pits on the surface of AerMet100 steel samples increases significantly, accompanied by surface cracking, which promotes the initiation and propagation of fatigue cracks. Due to the shielding effect of the surface passivating film on the corrosive medium, the TC18 titanium alloy effectively prevents the in-depth erosion of the corrosive medium, limits the propagation path of the crack, and maintains a high fatigue life.

Identification of microcracks in time is important for the safety control of concrete structures. In this study, four-point bending experiments were conducted on basalt fiber concrete specimens. The strain fields information on the specimen surface were acquired by digital image correlation technique during the loading process. In the horizontal strain field, 300 points with large strains were selected as points of interest (POI), the aggregation factor was calculated based on the standard deviation of the coordinates of the POI in the strain field, and a method for identifying microcracks associated with a single strain field only was proposed by using the distribution evolution of the aggregation factor during the loading process. This method can exclude the error generated by human judgment of microcracks, but it is not sufficient to identify multiple microcracks. The accuracy of the method exceeds 95% and is suitable for engineering applications.