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The microstructure and cellular transition characteristics of an intermetallic Ti-42Al-3Nb-1Mo-0.1B (at.%) alloy were investigated. The as-cast microstructure of the alloy is mainly composed of (α2+γ) lamellar structure and (β+γ) mixture structure, which distributes along the boundaries of the lamellar colonies. In order to study the phase transformation of lamellar structure at aging temperature, a two-step heat treatment was carried out. After the first step of annealing treatment at 1,260 °C, the microstructure with relatively finer lamellar space and (γ+β/B2) mixture structure is obtained. Aging treatment, as the second heat treatment step, has significant influence on the microstructure, attributing to a cellular reaction of α2+γ→ γ+β. With the increase of aging temperature, the (α2+γ) lamellar structure continues to dissolve, whereas the contents of both the equiaxed γ and β/B2 grains continuously increase. Besides, the orientation of lamellae α2, equiaxed γ and equiaxed β/B2 in the cellular transition region follows a specific relationship of {0–11}ββ//{0001}α2α2//{1–11}γγ.

A dynamic model of a helical gear rotor system is proposed. Firstly, a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed. The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness. Combining the gear dynamic model with the rotor-bearing system model, the gear-rotor-bearing dynamic model is developed. Then three cases are presented to analyze the dynamic responses of gear systems. The results reveal that the gear dynamic model is effective and advanced for general gear systems, narrow-faced gear, wide-faced gear and gear with tooth profile errors. Finally, the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments. The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.

The very large floating structure (VLFS) deployed near seashore, islands and reefs are always exposed to the extremely complex encountering waves. Traditional methods with homogeneous wave inputs are not applicable for the hydroelastic analysis of this type VLFS. In this paper, the authors carry out a numerical and experimental investigation on hydroelastic responses of an 8-module VLFS near a typical island. A direct coupling analysis method is established on the basis of the Boussinesq equation and RANKINE source method. The detailed theoretical derivation, numerical method and relevant calculation program THAFTS-BR are presented. Wave propagation near the island, motions and connector loads of the VLFS deployed a typical island are investigated based on the numerical method and model tests. Several useful conclusions are obtained, which can provide a reference for the analysis of dynamic responses, design and construction of the floating structures near islands and seashores.