During automatic and intelligent cutting at the coal mining face, complex geological conditions (fold structure, fault structure and magmatic intrusion) easily cause distinct occurrence conditions of coal rock seams (gangue, inclusion, or fault in the coal and rock), which induces different coal-rock cutting performances of shearer picks. Therefore, the objective of the present study is to review the selected solutions on the evaluation of coal-rock cutting performances of shearer picks under complex geological conditions. Occurrence conditions of coal rock seams were classified according to different criteria. Mechanical coal-rock breakage of coal rock by shearer picks were introduced. Shearer pick forces during coal-rock cutting (load spectrums of the pick and the mechanical model of the pick force) and coal-rock cutting mechanism (coal-rock cutting process by the pick and pick failure mechanisms) were discussed. The service safety evaluation of the pick based on wear and fatigue (pick wear, quantitative evaluation of service safety, and methods to improve the service safety) was presented. Finally, research prospects were outlined to propose the future research focus of shearer picks under complex geological conditions, such as the adaptive cutting of shearers, the fusion detection method of coal-rock interface by automatic shearers, the effects of geological conditions on coal-rock cutting mechanisms, the selection of systems suitable for different geological conditions, and shearer pick reliability evaluation. Results of this study are of great significance in understanding failure modes and the cutting mechanisms of shearer picks, quantitatively evaluating pick safety, promoting the automatic and intelligent cutting of coal rock seams, and thereby improving the production efficiency of shearers.

The textured design of amorphous carbon (a-C) film can significantly improve the tribological performance and service life of moving mechanical components. However, its friction dependence on different texture shapes, especially under different load conditions, remains unclear. In particular, due to the lack of information regarding the friction interface, the underlying friction mechanism has still not been unveiled. Therefore, the effects of contact pressure and textured shapes on the tribological behavior of a-C films under dry friction conditions were comparatively studied in this work by reactive molecular dynamics simulation. The results show that under low contact pressure, the tribological property of a-C film is sensitive to the textured shape, and the system with a circular textured surface exhibits a lower friction coefficient than that with a rectangular textured surface, which is attributed to the small fraction of unsaturated bonds. However, the increase of contact pressure results in the serious reconstruction and passivation of the friction interface. On the one hand, this induces a growth rate of friction force that is much smaller than that of the normal load, which is followed by a significant decrease in the friction coefficient with contact pressure. On the other hand, the destruction or even disappearance of the textured structure occurs, weakening the difference in the friction coefficient caused by different textured shapes of the a-C surface. These results reveal the friction mechanism of textured a-C film and provide a new way to functionalize the a-C as a protective film for applications in hard disks, MEMS, and NEMS.

Sim, a potent HMG-CoA reductase inhibitor, exhibits notable anabolic effects on bone and can upregulate osteogenic genes such as BMP-2, thereby promoting bone formation. An ideal drug delivery system for Sim involves its controlled and sustained release at the defect site to minimize adverse side effects. In this study, Sim was first modified via HP-γ-CD to form a hydrophilic Sim/HP-γ-CD inclusion complex, thereby improving drug solubility and dispersion in aqueous systems. A gelatin–sodium alginate (Gel/SA) hydrogel was then employed as the drug delivery matrix to construct a Gel-SA-Sim/HP-γ-CD hydrogel sustained release system. This hydrogel system exhibited a high water content (82%), along with enhanced mechanical properties, including a compressive strength of 0.284 MPa and a compressive modulus of 0.277 MPa, suggesting strong load-bearing capacity and favorable stiffness. Importantly, Sim was released in a controlled and sustained manner over 7 days, without exhibiting burst release behavior. In vitro osteogenic differentiation assays demonstrated that optimal concentrations of Sim effectively enhanced cellular bioactivity and osteoinductive performance, offering a promising approach to enhance the bioactivity, osteogenesis, and osseointegration of orthopedic implants.

The operation of the hoist is not simply a constant motion, and different forms of lifting acceleration can cause changes in the tension of the steel wire rope, thereby affecting the strain and friction transmission of the friction lining. The coal mine environment is harsh. During the operation of a friction hoist, different mediums are often mixed between the friction lining and the steel wire rope. In order to explore the appropriate forms of lifting acceleration under different contact interface medium, and to investigate the influence of different contact interface medium on the strain and friction performance of friction lining under different acceleration forms, this paper simulates the mine environment and conducts four different forms of lifting acceleration friction experiments using the dynamic micro sliding friction experimental platform of friction lining and steel wire rope. The strain and friction performance changes of friction linings are analyzed through DIC technology. The results show that under different contact interface medium, the strain change amplitude of the friction lining is the smallest under the trapezoid acceleration form, and the stability of the friction transmission is the best. Under trapezoid acceleration conditions, the friction force, friction coefficient, and strain amplitude of the friction-enhancing grease medium are the smallest, the maximum strain value decreases by 45.6%, and the friction force decreases by 64.3%, which has the greatest impact on the friction transmission performance of the friction lining. This paper provides guidance for the safe operation of friction type hoists.

The current Special Issue, entitled “Friction, Corrosion and Protection of Material Surfaces”, aims to discuss the state-of-the-art research progress regarding the friction and corrosion behaviors of new materials and advanced protective materials or technologies, with a special focus on the understanding of underlying friction and corrosion mechanisms and modification approaches of material surfaces against friction and corrosion in order to guide the design and preparation of materials with high performance for practical applications