No abstract

As to the random sonic fatigue problem of thin walled structure of aerospace flight vehicle, estimation method for fatigue life based on Von Mises stress peak probability density is investigated. Assuming that Von Mises stress process satisfies three-parameter Weibull distribution, the peak probability density function of Von Mises stress is derived through the threshold crossing analysis and the peak distribution analysis of stationary random process. According to the Miner linear cumulative damage theory, the method for estimating the fatigue life in the frequency domain is established with the Von Mises stress peak probability density function applied. As an example, an aero-engine Combustor liner is considered, using coupled Finite Element Method (FEM) and Boundary Element Method (BEM) method, the structure vibration response to limited bandwidth Gaussian white noise is calculated. Based on the results, fatigue life of the structure is estimated by using the proposed method. Further more, the influences of the probability density function which is characterized by three-parameter Weibull distribution and two-parameter Weibull distribution respectivily for Von Mises stress response of the Combustor liner structure subjected to random accoustic loadings are discussed.

Easy management and maintenance and highly cost effective equipment make Ethernet an attractive technology for deploying Metropolitan Area Networks (MANs). However, Ethernet has poor scalability due to use flat addressing scheme. To make Metro-Ethernet more scalable, the Provider Edge (PE) nodes can use MAC-in-MAC (MiM) encapsulation scheme for frame forwarding. The MiM encapsulation scheme reduces the forwarding table size in the Core Nodes (CNs), but not in the PE nodes which need to maintain the entries of mapping end user's MAC address to PE's MAC address. In this paper, we propose an End user enabled MAC-in-MAC (EMiM) encapsulation scheme for Metro-Ethernet. In the proposed scheme, a user's MAC address as well as its PE node's MAC address are associated with its Address Resolution Protocol (ARP) entry. The modified ARP entry allows the end user to do MiM encapsulation. Hence a PE node does not need to maintain the entries of mapping end user's MAC address to PE node's MAC address, thus significantly reducing the forwarding table size. The proposed scheme sustains Ethernet's plugand-play feature and provides high scalability. The simulation results show that the proposed scheme can reduce up to 65% maximum forwarding table size in PE nodes.

Advanced materials and processes are required to meet the performance goals in the design of advanced turbofan engine, SiC/Ti composite is typically used in low pressure turbine shaft (LPTS). Firstly, establish the viability and effectiveness of composite cylinder assemblage (CCA) micro-mechanics model and representative volume element (RVE) micro-mechanics model which are utilized to calculate the mechanical parameter of continuous fiber reinforced metal matrix composite (CFRMMC), respectively. Results show that RVE model is more applicable to calculate continuous fiber reinforced LPTS. Secondly, parameters of mechanics performance calculated by RVE model are taken as input to build mechanics analysis model of fiber reinforced metal matrix composite shaft structure. The optimal solution will be got by design and analysis of CFRMMC shaft structure with 2 kinds of loads. Compared with deformation and stress of shaft structure with different material scheme, then an optimization scheme of SCS/Ti2AlNb composite of LPTS can be obtained.

This paper focuses on the course teaching system reform for numerical methods for engineering with new engineering feature. The course of numerical methods for engineering has strong theoretical knowledge, complicated experiments and calculation, which is difficult to active the students' attention. Thus the existing curriculum system should be reformed. Take the course of numerical methods for engineering in Light industrial mechanics department for example. Firstly, based on the teaching idea, strengthen the process of the students in school education. Introduce interaction between students and teachers; promote initiative of students, continuous improvement to achieve leapfrogging. Secondly, improve the teaching methods and means. Breaks the traditional teaching mode and emphasizes students' participation consciousness. Put the students in the central position of classroom teaching and fundamentally change the students' class status. Then, design the teaching content, the course can be divided into several modules to give lectures and arrange discussion between students and teachers. Fourthly, modularize method and continuous improvement is applied in our teaching thoroughly, and guide the students to participate in teaching processing actively. Finally, establish a perfect assessment way, sum up experience timely, and constantly revise and improve our reform. With these, a good start can be made for the reform for numerical methods for engineering in new engineering education.