The biological coupling characteristics of dragonfly wings is a model of the perfect combination of flexibility and rigidity of organisms and the presentation of excellent mechanical properties. The fatigue resistance is resulting from the coupling of its optimized shape, structure and mechanical characteristics. Based on this principle, the bionic brake hub processed by laser bionic coupling preparation technology has a service mileage of more than 70,000 km, which not only increases its fatigue life by at least 30% than ordinary untreated brake hubs, but also reduces manufacturing costs by 6.75%.
Dragonfly with superb flying ability, its flight speed and endurance are amazing. Though, the wings are weak and thin, it could vibrate 20 to 40 times per second, and fly 70 kilometers per hour safely. The dragonfly wings possess very good strength and toughness, stability and carrying capacity, which could bear alternating stress with a certain frequency and amplitude, exhibiting excellent anti-fatigue property. Dragonfly wings' surface appears to be reticular veins and non-smooth morphology, composed of hard vein and soft wing membrane. The biological coupling characteristics of dragonfly wings is a model of the perfect combination of flexibility and rigidity of organisms and the presentation of excellent mechanical properties.
Dragonfly wings show perfect mechanical properties, which provides natural resistance to external damage and high-frequency fatigue. Researches show that the optimized network structure and three-dimensional truss-like shape have obvious inhibition on the formation and propagation of fatigue crack. The multi-layer composite of dragonfly's vein has the coupling characteristics of strong and tough. Meanwhile, the partial connection between the vein is flexible, the whole wing appears to be rigid-flexible coupling, which is the main reason of releasing stress and resisting crack.
Figure 1 Dragonfly wings and its coupling characteristics. (a) Dragonfly wings, (b) Venation texture, (c) Layered structure, (d) Flexible vein-joints
At present, this principle has made breakthrough progress in the application of hot work molds, brake hubs, brake discs and other components. The bionic components processed by laser bionic coupling preparation technology can significantly improve thermal fatigue resistance. The brake hub treated by bionic coupling laser process can fully meet the braking requirements of the vehicle. The service life can reach more than 70,000 km, which not only increases its fatigue life by at least 30% than ordinary untreated brake hubs, but also reduces manufacturing costs by 6.75%.
Figure 2 Application test after 35 thousand kilometers. (a) Application on truck, (b) Common hub, (c) Bionic hub
 Yang X, Zhang Z H, Wang J T, et al. Investigation of nanomechanical properties and thermal fatigue resistance of gray cast iron processed by laser alloying[J]. Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics, 2015, 626: 260-263.
 Zhang Z H, Lin P Y, Kong S H, et al. Thermal fatigue behavior of Mg-9Al-Zn alloy with biomimetic strengthening units processed by laser surface remelting[J]. Optics & Laser Technology, 2015, 70: 1-6.
 Zhou H, Zhang Z H, Ren L Q, et al. Effect of units in different sizes on thermal fatigue behavior of 3Cr2W8V die steel with biomimetic non-smooth surface[J]. International Journal of Fatigue, 2009, 31(3): 468-475.
 Li X J, Zhang Z H, Liang Y H, et al. Antifatigue properties of dragonfly Pantala flavescents wings[J]. Microscopy Research and Technique, 2014, 77(5):356-362.
 Ren L Q, Li X J. Functional characteristics of dragonfly wings and its bionic investigation progress[J]. Science China, 2013, 56(4): 884-897.