Lan Yan

This study developed a biomimetic jumping robot inspired by frogs to enhance its obstacle-crossing capabilities. The biological principles underlying the jumping biomechanics of frog hindlimbs were integrated into the robotic mechanism; quantitative analysis of the bionic structure and its jumping performance not only provides mechanical engineering insights for investigating frog locomotion mechanics but also offers practical design references for the development of biomimetic mobile robots. Through theoretical calculations and application scenario analysis, a six-bar linkage mechanism was designed to simulate the force generation of frog hindlimbs, with tension springs mimicking the elastic energy storage function of the semimembranosus and gastrocnemius muscles. A reducer was integrated into the trunk to enable energy storage, and an adjustable single-hinge structure was adopted for the forelegs to realize take-off angle adjustment and shock absorption. Finite element simulations were conducted to validate the load-bearing capacity and strength of critical components. Multi-body dynamics and the particle swarm optimization (PSO) algorithm were employed to explore the relationship between input parameters and output performance metrics (jumping height and jumping distance), while orthogonal experimental analysis was used for comprehensive parameter evaluation. Finally, a physical prototype was fabricated, and its performance parameters were tested. The prototype has a mass of 150 g, generates a ground push force of 50 N, attains a jumping height of 380 mm, and achieves a maximum jumping distance of 500 mm. This study establishes a biologically inspired working principle for jumping robots and provides a novel practical prototype for research into biomimetic mobile robots.

Annelid-inspired robots exhibit excellent motion adaptability and structural compliance, enabling them to navigate confined, hazardous, or complex environments such as pipelines, soil, or the gastrointestinal tract. This review summarizes key developments in their bionic part design, actuation methods, material selection, and performance characteristics. Comparative analyses show that different actuation strategies (e.g., pneumatic, shape memory alloys, and electroactive polymers, etc.) need to be weighed in terms of their advantages, limitations, and applicable environments. Materials like silicone rubber and SMA are evaluated for their strength, flexibility, and energy performance. Quantitative benchmarks of velocity, load capacity, and energy consumption are presented to highlight design-performance correlations. Prospective research directions include the integration of multifunctional adaptive materials, real-time feedback sensing systems, and scalable architectures for autonomous operation in unstructured environments.

The surface integrity of grinding has a significant influence on the service performance and life of machined parts. In this study, the influence of grinding parameters and the grit size of the grinding wheel on the surface integrity of the hardened steel, including the roughness, microstructure, and hardness of the subsurface and the residual stress of the ground surface, was comprehensively investigated, and the corresponding mechanisms were revealed. The results show that the roughness perpendicular to the grinding direction was significantly larger than that parallel to the grinding direction due to serious side flow, and increasing the grinding speed or reducing the grinding depth was beneficial for reducing the side flow and thus decreasing the roughness. It was found that the grinding temperature dominated the formation of a harder white layer and a softer black layer, and workpiece speed had the smallest effect on the transition of subsurface microstructure compared to grinding speed and depth. It was also found that the increase in workpiece speed, grinding depth, or grinding speed resulted in a transition from compressive to tensile residual stress or an increase in tensile residual stress, and that grinding wheels with finer grit tended to induce compressive residual stress. This study may help to improve surface integrity by optimizing grinding parameters or facilitating the selection of the optimal grinding wheel.

The MM Science Journal, published since 2008, is a world respected scientific journal. The journal, published in English, is double peer reviewed and competitive in distributing knowledge among domestic and international academics and professionals. Full texts are available on-line on the journal...

Coated cutting tools are widely used in the manufacturing industry due to their excellent properties of high heat resistance, high hardness, and low friction. However, the milling process is a dynamic process, so the coatings of milling tools suffer severe cyclic impact loads. Impact resistance is important for the life of milling tools. Multi-coatings with different layer thickness may influence their impact resistance, but few studies focus on this topic. In this study, CVD coating with a structure of TiN layer, Al₂O₃ layer, and TiCN layer was selected as the research objective. Four different CVD coatings with different layer thicknesses were designed and prepared. The impact resistance test method was proposed to simulate the impact due to cut-in during down the milling process. We obtained the load by setting an impact depth of 25/30/35 µm, recording the impact force during the impact process, and calculating the contact stress; it was found that, at the impact depth of 25/30/35 µm, the download loads were around 9/11/13 N, while the contact stresses were all around 1 GPa. The failure morphology of the coating surface was investigated after the impact process. By comparing the contact stress and the surface morphology of the designed coatings, the impact resistance of four kinds of designed CVD coatings were evaluated. Experiments have shown that an increase in coating thickness and total coating thickness reduces impact resistance by about 10%. The impact resistance of coating samples without a TiN surface layer also decreased by about 10%. When the surface layer of TiN was thinner than 1 µm, the surface layer of TiN was prone to chipping and peeling off. Decreasing the thickness of the middle layer of Al₂O₃ and increasing the thickness of the inner layer of TiCN obviously lowered the impact resistance.

Cutting fluids are the most effective method to lower the cutting temperature and decrease the cutting tool wear. At the same time, the cutting fluids influence the corrosion resistance property of the machined surface. In this study, chlorinated paraffin (CP), which is a common additive in the cutting fluid, was selected as the research objective to study its corrosion resistance property. The passivation effect of CP with different concentrations on the machined surface of stainless steel was studied. Electrochemical measurements and surface morphology investigation were used to characterize the passivation effect of CP with different concentrations. The test results showed that the corrosion resistance of stainless steel in the cutting fluid was enhanced with the increase in CP additive. This reason is that the charge transfer resistance increases and the corrosion current density decreases with the increase in CP additive. The X-ray photoelectron spectroscopy (XPS) results show that the proportion of metal oxides on the processed surface of the stainless steel sample was increased from 20.4% to 22.0%, 32.9%, 26.6%, and 31.1% after adding 1 mL, 2 mL, 4 mL and 6 mL CP in the cutting fluid with a total volume of 500 mL, respectively. The oxidation reaction between CP and the stainless steel sample resulted in an increase in metal oxides proportion, which prevented the stainless steel sample from corrosion in cutting fluid.

Single grit scratching is a basic form of material removal for many processes, such as grinding single point diamond turning and coating bonding performance tests. It has been widely used in the study of micro-scale and nano-scale material removal mechanisms. In this study, single grit linearly loading scratching tests were carried out on a scratching tester. A Rockwell indenter made of natural diamond was selected as the tool used, and the material of the workpiece was oxygen-free copper. Scratch topography was measured using a super-depth microscope to analyze the material deformation of the scratching process. A single grit scratching simulation has been developed by AdvantEdge™ to comprehensively study the material deformation of scratching processes. A material constitutive model and friction model were acquired using a quasi-static uniaxial compression experiment and a reciprocating friction test, respectively. These two models were used as the input models in the finite simulations. The simulated scratching forces aligned well with the experimental scratching forces, which verified the precision of the simulation model. Since only the scratching force could be obtained in the scratching experiment, the plastic strain, material flow, and residual stress of the scratching were further analyzed using simulations. The results showed that the plastic strain of the workpiece increased with the increase in scratching depth, and further analysis showed that the workpiece surface was distributed with residual compressive stress and the sub-surface was distributed with residual tensile stress in single grit scratching.