1. 汇报安排
题目：参加ASME IMECE 2016国际会议总结报告会
时间：2016年11月28日10:00—12:00
地点：曲江校区西五楼南A228会议室
报告人：博1317班—左浩，博1501班—杨来浩，博1417班—耿佳
2. 参加国际会议信息
会议名称：ASME International Mechanical Engineering Congress and Exposition
会议时间：November 11 – 17, 2016
会议地点：Phoenix, Arizona, USA
会议简介：ASME is the premier organization for the promotion of the art, science, and practice of mechanical engineering throughout the world. Our mission is to promote and enhance the technical competency and professional well-being of our members, and through quality programs and activities in mechanical engineering better enable its practitioners to contribute to the well-being of humankind.
The International Mechanical Engineering Congress and Exposition (IMECE) is the largest interdisciplinary mechanical engineering meeting in the world. IMECE plays a significant role in stimulating innovation from basic discovery to translational application. It fosters new collaborations that engage stakeholders and partners not only from academia, but also from national laboratories, industry, research settings, and funding bodies. Among the 4,000 attendees from 75+ countries are mechanical engineers in advanced manufacturing, aerospace, advanced energy, fluids engineering, heat transfer, design engineering, materials and energy recovery, applied mechanics, power, rail transportation, nanotechnology, bioengineering, internal combustion engines, environmental engineering.
会议交流工作：
Presentation: Modelling of Lamb Wave Propagation in Beam-like Structures via Wavelet Finite Element Method.汇报人—左浩
Presentation: Rub-impact Detection of Rotor Systems Using Time-frequency Techniques.汇报人—杨来浩
Presentation: High-frequency Vibration Analysis of Thin Plate Based on B-spline Wavelet on Interval Finite Element Method.汇报人—耿佳
3. 参会论文信息
Title：Modelling of Lamb Wave Propagation in Beam-like Structures via Wavelet Finite Element Method
Author：Hao Zuo，Xuefeng Chen，Zhibo Yang，Laihao Yang
Abstract:Beam-like structure is known as one of crucial engineering structures in practical application of aerospace, vessel, civil and machinery. The damages of beam-like structures have a great influence on machine performance and may cause a serious threaten for security of mechanical structures and systems. Thus it is very signification to identify the damage of beam-like structures for security of mechanical structures and systems. This paper presents a novel application of wavelet finite element method (WFEM) in Lamb wave propagation of beam-like structures. The WFEM, adopting excellent B-spline wavelet on interval (BSWI) basis as approximating functions, has been verified to possess some superiorities for structural dynamic analysis and damage detection. The motion equations of Lamb wave propagation are derived according to Hamilton's principle and two-dimensional wavelet-based element is constructed by adopting BSWI scaling functions. The damage, which is modeled as open crack with duplicate nodes in crack, is considered in beam-like structures and corresponding damage model is also added in proposed wave finite element model. Then the central difference method in time domain is employed for wave propagation simulation. Firstly, the validity and accuracy of proposed WFEM are demonstrated on a beam-like structure without crack by comparing with traditional finite element method (FEM) using 2D plane element. What's more, the obtained velocities of fundamental S0 and A0 mode waves are also compared with Lamb theoretical results to verify the validity and accuracy of proposed model once more. Then the wave propagation in beam-like structures with crack are performed and the process of wave propagation and interaction between Lamb wave and damage is analyzed and discussed in detail. The reflected mode wave and converted mode wave for incident wave interacting with crack are also observed in different wave motion snapshots. In summary, this paper presents an accurate but simple and effective numerical method for wave propagation of beam-like structures.
Title：Rub-impact Detection of Rotor Systems Using Time-frequency Techniques
Author：Laihao Yang，Xuefeng Chen，Shibing Wang，Hao Zuo
Abstract:Since increasing demands for high efficiency of high speed rotating machines in recent years, the clearance between rotor and stator gets smaller and smaller. Consequently, rub-impact fault is more likely to occur. It has become one of the most common and serious malfunctions for rotor system in practical engineering. Because the rub-impact severely induces the rotor dynamic instability, it will finally result in catastrophic failures and great economic loss if undetected in time. The occurrence of the rub-impact leads to a contact force between rotating shaft and stator which can be regarded as an additional support on the rotor system. The contact force will further result in the stiffening effect. As a result, some fast time-varying phenomena of vibration responses including the fast time-varying transient stiffness and the fast oscillated instantaneous frequency (IF) may appear. These phenomena may offer abundant characteristics to diagnose the rub-impact fault of rotor system. In this paper, an effective method based on the fast oscillated characteristics of IF for vibration responses is proposed to detect rub-impact fault of rotor bearing system. First of all, the fast time-varying transient stiffness of rub-impact rotor system is qualitatively formulated based on the Jeffcott rotor model and the fast oscillated characteristics of IF is presented and theoretically analyzed. Second, a time-frequency technique called nonlinear squeezing time-frequency transform (NSTFT) is introduced to extract the fast oscillated IF resulting from the rub-impact fault of rotor systems. Numerical simulations are respectively conducted on the Jeffcott rotor system with linear stiffness and oil film bearings. And then the oscillated characteristics of the IF are analyzed. The analysis results suggest that the IF of the vibration responses remains constant at the rotating frequency if there is no rub-impact fault. However, if rub-impact fault occurs, the IF of the vibration responses will oscillate periodically around the basic harmonic frequency. Furthermore, the oscillation law of the IF of vibration responses for rub-impact rotor systems is also numerically investigated. It’s found that the oscillation frequency is the 1/k (k = 1,2,3, …) of the rotating frequency if the rotor system operates at periodic-k motion. Finally, rub-impact fault experiments are performed under different operating regimes. The experimental results are consistent with the numerical results, thus demonstrating the validity and the practicability of the proposed method.
Title：High-frequency Vibration Analysis of Thin Plate Based on B-spline Wavelet on Interval Finite Element Method
Author：Jia Geng，Xingwu Zhang，Xuefeng Chen，Xiaofeng Xue
Abstract:For the dynamic analysis of thin plate bending problems, the Finite Element Methods (FEMs) are the most commonly used numerical techniques in engineering. However, due to the deficiency of low computing efficiency and accuracy, the FEMs can’t be directly used to effectively evaluate dynamic analysis of thin plate with high modal density within low-high fre-quency domain. In order to solve this problem, the Wavelet Finite Element Methods (WFEMs) has been introduced to solve the problem by improving the computing efficiency and accu-racy in this paper. Due to the properties of multi-resolution, the WFEMs own excellently high computing efficiency and accu-racy for structure analysis. Furthermore, for the destination of predicting dynamic response of thin plate within high fre-quency domain, this paper introduces the Multi-wavelet ele-ment method based on c1 type wavelet thin plate element and a new assembly procedure to significantly promote the calculat-ing efficiency and accuracy which aim at breaking up the limi-tation of frequency domain when using the existing WFEMs and traditional FEMs. Besides, the numerical studies are ap-plied to certify the validity of the method by predicting state response of thin plate within 0~1000Hz based on a special nu-merical example with high modal density. According to the literature, the frequency domain between 0 to 1000Hz contains the low-high frequency domain aiming at the numerical exam-ple. The numerical results show excellent agreement with the reference solutions captured by FEM and analytical expressions respectively. Among these, it is noteworthy that the relative errors between the analytical solutions and numerical solution are less than 0.4% when the dynamic response involved with 1000 modes.
