29 May 2020
The lecture was presided over by Professor Jin, the head of the Department of Engineering Mechanics of the School of Aeronautics and Astronautics. More than 60 teachers and students from the School of Aeronautics and Astronautics, Civil Engineering and Mechanical College attended the lecture.
Professor Jin gave a brief introduction to Roberto. Roberto is the head of the Department of Civil and Environmental Engineering at the University of Houston. He used to be the director of the ASCE Engineering Mechanics Institute. He is currently the editor of the ASCE Engineering Mechanics Magazine and the 2019 ASCE Raymond D. Mindlin Medal Winner.
His multidisciplinary research is mainly about theories, calculations and experimental techniques for characterizing the response of materials to mechanical, thermal and environmental loads, especially the establishment of computational analysis models describing the fatigue and fracture of materials and structures. His research is used in many fields such as civil engineering, mechanical and aerospace engineering, materials science, microelectronic mechanical systems, biotechnology, and prosthetic design.
In the report, Roberto pointed out that natural composite materials are known for their mechanical strength and toughness. Although natural composite materials have a high degree of mineralization, because the organic composition does not exceed a few percents of ordinary composite materials, their fracture toughness is still better than Single crystals of pure minerals are two to three orders of magnitude higher.
The rational distribution of the organic matrix in the mineral phase and the hierarchical structure extending beyond several length scales play a vital role in the mechanical response of natural composites to external loads. In addition, natural composite materials can also repair the serious damage they may suffer.
His research team proved for the first time through experimental and theoretical results that the use of two energy dissipation mechanisms can quantitatively explain the resistance source of the Big Mac Conch to severe fractures: multiple cracking of the outer layer under low load; and under greater load In the case of a harder intermediate layer of the shell, crack bridging will occur.
Both of these mechanisms are closely related to the so-called cross-layered microstructure of the shell, which provides tunnel cracks in the outer layer of the shell and provides crack-free structural features bridging the crack surface at multiple scales. Therefore, Although the mineral content of aragonite is about 99% (volume ratio), the shell of the conch can still be regarded as "ceramic plywood" (although plywood is destroyed in a different way than the shell) and can guide the bionic design of tough, lightweight structures.
This lecture is rich in content, the professor's language is humorous and combined with many examples of vivid colors so that everyone has a better understanding of the reverse engineering and bionic design of mollusk shells. After the report, the teachers and students and Roberto participated in the heated academic exchanges and discussions. The professor communicated with everyone very patiently.
At the end of the lecture, entrusted by the Faculty of Engineering, Professor Jin presented Professor Roberto with a commemorative plaque on the frontier of engineering science. After the announcement of the academic activity, the audience applauded enthusiastically.