For the analysis on the deformation of flexible ring gears in spur gear pairs, the complete flexible ring is discretized, and the boundary condition is added to the connecting points to develop a calculation method for the flexible deformation. The ovality index is used to describe the deformation degree of flexible ring gears, then the influences of ring-gear width and the spalling defects on the flexible deformation of ring gears are discussed. The result shows that the flexible deformation of ring gears is caused by the gear pair meshing force, and the deformed shape is close to an ellipse. In the single-tooth meshing interval of gear pairs, the main form of deformation is being stretched, and while in the double-tooth meshes, the main form is bending deformation. When the width of the ring gear rims is increased, the flexible deformation of the ring gears can be effectively suppressed, and the vibration amplitude of the gear pairs can be reduced. Additionally, when there is a localized spalling fault on gear pairs, the sudden changes in the deformation of flexible ring gears are generated by the shock of the meshing force. Finally, through the finite element analysis model and the experiment, the mathematical model of gear pairs with flexible rings is confirmed.

Fabrication of porous metallic implants using additive manufacturing technology are expected to be an ideal treatment for substantial segmental bone defects. Gyroid porous tantalum (Ta) was produced by selective laser melting (SLM). Chitosan (CHS) and nano-hydroxyapatite (n-HA) composite sponges were prepared in the pores of porous Ta by freeze-drying. The porous Ta possesses a pore diameter of about 359 μm, porosity of 65.8%, elastic modulus of 1.69 GPa, and compressive strength of 68.59 MPa, which make it suitable for bearing loads. Scanning electron microscopy showed that the pores of porous Ta were filled with CHS/n-HA composite sponge with a pore diameter of 20–80 μm and n-HA particles embedded on the pore wall of the CHS sponge. The composite sponge could provide an ideal affinity microenvironment for cell adhesion and growth, which could regulate cellular behaviors and promote new bone regeneration. Porous Ta/CHS/n-HA composite scaffolds fabricated by SLM exhibited the mechanical properties and corrosion resistance of porous Ta, as well as the bioactivity and osteoinductivity of organic–inorganic composite biomaterials. These results indicate that porous Ta/CHS/n-HA composite scaffolds fabricated by SLM could serve as an ideal substitute for bone defect repair.

To address the inherent brittleness of β -tricalcium phosphate ( β -TCP) bioceramics, we incorporated ZnO, SrO, or bioactive glass (AK) into a β -TCP matrix. Porous scaffolds were fabricated via digital light processing and sintering. X-ray diffraction confirmed the preservation of the β -TCP phase, and SEM revealed a multiscale porous architecture with uniform macropores (∼400 μm) and submicron surface micropores specifically in the β -TCP/AK composite. This scaffold exhibited the most balanced performance: its compressive strength increased by ∼38% to 9.65 MPa compared to pure β -TCP. During immersion in simulated body fluid, the β -TCP/AK scaffold induced a favorable alkaline pH, exhibited the highest degradation rate (mass loss), and enabled sustained release of bioactive Si ⁴⁺ and Mg ²⁺ ions, which enhanced apatite mineralization. In vitro , all modified scaffolds promoted osteoblast proliferation. Notably, the β -TCP/AK scaffold most significantly stimulated osteogenic differentiation, elevating ALP activity to 2.48 ± 0.184 (vs. 1.87 ± 0.126 for pure β -TCP) and upregulating key osteogenic genes (ALP, OCN, RUNX2). These results demonstrate that AK doping optimally enhances the mechanical strength, biodegradation, ion release, and osteogenic capacity of β -TCP, presenting a highly promising composite for bone tissue engineering.