The Ti-6Al-4V alloy is a typical α + β type titanium alloy and is widely used in the manufacture of aero-engine fans, compressor discs and blades. The working life of modern aero-engine components is usually required to reach more than 10⁸ cycles, which makes the infinite life design based on the traditional fatigue limit unsafe. In this study, through symmetrical loading high-cycle fatigue tests on Ti-6Al-4V titanium alloy, a nonlinear cumulative damage life prediction model was established. Further very-high-cycle fatigue tests of titanium alloys were carried out. The variation law of plastic strain energy in the evolution process of very-high-cycle fatigue damage of titanium alloy materials was described by introducing the internal stress parameter. A prediction model for the very-high-cycle fatigue life of titanium alloys was established, and the sensitivity analysis of model parameters was carried out. The results show that the established high-cycle/very-high-cycle fatigue models can fit the test data well. Moreover, based on the optimized model parameters through sensitivity analysis, the average error of the prediction results has decreased from 59% to 38%. The research aims to provide a model or method for predicting the engineering life of titanium alloys in the high-cycle/very-high-cycle range.

Planetary gears are recognized as one of the most effective forms of power transmission. A dynamic model of an N-stage power-split planetary gear set is proposed in this article. Three-dimensional translations and axial rotation of all members, mesh stiffness, bearing stiffness, and the interstage coupling stiffness are considered. Subsequently, equations of motion of the whole system are derived. Natural frequencies and vibration modes are obtained by solving the eigenvalue problem governed by corresponding equations. According to the modal properties, all vibration modes of the N-stage system can be categorized as N + 2 groups: the overall axial translational–rotational mode, the overall radical translational mode, and the ith-stage planet mode ( N_i > 3). Furthermore, the typical vibration modes of a two-stage system are graphed. It is also found that the radical interstage coupling stiffness has an impact on natural frequencies of the overall radical translational modes, while the axial and twist coupling stiffness only affect the natural frequencies of the overall axial translational–rotational modes.

With the continuous development of enterprise information technology, information resource sharing has become a major subject of scientific research projects. Traditional enterprises have complex business processes, low management efficiency and high operation cost, which leads to enterprises of low competitiveness. Therefore, it is the best choice for enterprises to regain their core competitiveness to use ERP management system to improve their operation process, simplify their operation and make their operation methods transparent. This paper designs an ERP system based on SSM framework. This paper introduces the basic principles of SSM framework, respectively realizes the business functions of Controller layer, Service layer and DAO layer in the framework, and designs Web pages for data collection and display. The main components of the system consist of six modules: purchase plan, purchase order, purchase contract, purchase document inquiry, purchase to order and purchase return, which can well realize the actual requirements of enterprises.