Simulations On Hydrogen Embrittlement Of Aluminium Metal And Melting, Tensional Mechanical Properties Of III-VA Group Element Nanotubes

The thesis contains two parts, i.e. Part 1: MD(Molecular Dynamics) simulations on hydrogen embrittlement in aluminium metal materials, and Part 2: MD simulations of the melting and tensional properties of Group III-VA element nanotubes.Part1: MD simulations on hydrogen embrittlement in aluminium metalAluminium metal has many excellent properties, such as light weight, cheap price, abundant reserves, anti-corrosion properties, excellent machining capabilities, high strength and convenient synthesization with other metals into anti-high temperature or low temperature alloys, and is widely used in aeronautics,astro- nautics and navigation scopes. Many literatures and data indicate hydrogen-atoms in aluminium can reduce binding energy and critical stress intensity factor at crack tips, debase crystal lattice of metal, accelerate dislocation growth and mobility, induce crack or fatigue-crack growth in aluminium. Thus, it will result in the fatal accident on account of hydrogen embrittlement in aluminium. So it is necessary to investigate hydrogen embrittlement of aluminium in the aeronautics, astronautics and navigation scopes. Molecular Dynamics simulations were performed in the first part to investigate the properties of hydrogen embrittlement in single crystal and bicrystal aluminium by the down-to-up methods, the configurations and relations of energy/stress and strain were obtained. The mechanism of hydrogen embrittlement in aluminium was discussed at nanometer level.Part2: MD simulations of the melting and mechanical property of Group III-VA element nanotubesDue to the excellent mechanical property and the electrical property,carbon nanotubes were paid much attentions by researchers all over the world. As the important members of one-dimension nano-materials, single-walled silicon, germ- anium, carborundum, boron nitrogen, gallium nitrogen nanotubes hold similar structure to single-walled carbon, and have become hotspot in the field of micro- electron, physics and marerial. Whether do they have outstanding mechanical property similar to carbon nanotube?In this part, molecular dynamics simulations were performed to investigate their properties of melting and mechanics. Firstly, the melting of the III-VA group element nanotubes is simulated by MD, the molecular configurations, pair correlation function and energy changes of the nanotubes during the heating-up are obtained, and the differences of their melting properties are discussed systematically. Secondly, the mechanical properties of the III-VA group element nanotubes are investigated through MD simulations. We obtained Young's modulus, fracture strain, critical load, radial shrinkage ratio of the III-VA group element nanotubes, and analyzed the differences of their mechanical properties.