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Bifurcation and chaos of the bladed overhang rotor system with squeeze film dampers

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Science China(Technological Sciences) 2009年第3期52卷 709-720页

作者： CAO DengQing WANG LiGang CHEN YuShu HUANG WenHu School of Astronautics Harbin Institute of TechnologyHarbin 150001China

To study the nonlinear dynamic behavior of the bladed overhang rotor system with squeeze film damper (SFD), a blade-overhang rotor-SFD model is formulated using the lumped mass method and the Lagrange approach. The cavitated short bearing model is employed to describe the nonlinear oil force of the SFD. To reduce the scale of the nonlinear coupling system, a set of orthogonal transformations is employed to decouple the one nodal diameter equations of blades, which are coupled with the dy- namical equations of the rotor, with other equations of blades. In this way, the original system with 16+4n (n≥3) degrees of freedom (DoF) is reduced to a system with 24 DoF only. Then the parametric excitation terms in the blade-overhang rotor-SFD model are simplified in terms of periodic transforma- tions. The coupling equations are numerically solved and the solutions are used to analyze the dy- namic behavior of the system in terms of the bifurcation diagram, whirl orbit, Poincaré map and spec- trum plot. A variety of motion types are found such as multi-periodic, quasi-periodic, and chaotic mo- tions. Moreover, the typical nonlinear dynamic evolutions including the periodic-doubling bifurcation and reverse bifurcation are noted. It is noticed that there exist apparent differences in the dynamic behavior between the blade-overhang rotor-SFD models without and with considering the effect of blades.

关键词： bladed overhang rotor system squeeze film damper bifurcation chaos

SOLIDIFYING　STRUCTURES　OF　Al_2O_3　SHORT　FIBER／Al－Si　ALLOY　MATRIX　COMPOSITE　PREPARED　BY　squeeze　CASTING

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中国有色金属学会会刊：英文版 1995年第3期5卷 133-135页

作者： Zhang, Siqi Huang, Jinsong Shen, Jian Lu, Bin Xu, Guofu Central South Univ of Technology Changsha China

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关键词： composite short fiber Al-Si alloy solidifying structures squeeze casting

NONLINEAR NUMERICAL ANALYSIS OF A FLEXIBLE ROTOR EQUIPPED WITH squeeze COUPLE STRESS FLUID FILM JOURNAL BEARINGS

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Acta Mechanica Solida Sinica 2007年第4期20卷 309-316页

作者： Cai-Wan Chang-Jian Her-Terng Yau Department of Mechanical and Automation Engineering I-Shou University Kaohsiung County 840 Taiwan China Department of Electrical Engineering Far-East College Tainan County 744 Taiwan China

This study performs a dynamic analysis of a rotor supported by two squeeze couple stress fluid film journal bearings with nonlinear suspension. The numerical results show that the stability of the system varies with the non-dimensional speed ratios and the dimensionless parameter l＊. It is found that the system is more stable with higher dimensionless parameter l＊. Thus it can conclude that the rotor-bearing system lubricated with the couple stress fluid is more stable than that with the conventional Newtonian fluid. The modeling results thus obtained by using the method proposed in this paper can be used to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided.

关键词： couple stress fluid rotor-bearing system bifurcation chaos squeeze

Understanding Contaminant Veins in squeeze Casting and Semi-solid Metalworking Processes

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特种铸造及有色合金 2003年第z1期23卷 230-234,238页

作者： Edward J. Vinarcik, P.E. Engineer Voctorie Co.8218 Medicine Bow Run Fort WayreIdiana 46825 U.S A

When commercializing the semi-solid metalworking processes, component producers looked to conventional die-casting to identify potential defects and control component quality. Several defects were expected including cold shuts, cold flows, flash, drags, warping, and gas entrapment, just to name a few. Efforts were taken to avoid these defects. A new defect type, contaminant veins, has surfaced unique to semi-solid metalworking. Although, semi-solid metalworking has proven to be successful, component producers have been reluctant to report defects for fear of giving this emerging processes a bad reputation. Nonetheless, this defect must be understood to avoid future problems.

关键词： Contaminant Veins squeeze Casting Semi-solid Casting

Experimental investigation of time-dependent cavitation in an oscillatory squeeze film

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Science China(Physics,Mechanics & Astronomy) 2004年第z1期47卷 107-112页

作者： CHEN Xiaoyang, SUN Meili, WANG Wen, D. C. SUN, ZHANG Zhiming & WANG XiaojingResearch Institute of Bearings, Shanghai University, Shanghai 200072, China Department of Mechanical Engineering, State University of New York at Binghamton, NY 13902-6000, USA 1. Research Institute of Bearings Shanghai University 200072 Shanghai China 2. Department of Mechanical Engineering State University of New York at Binghamton 13902-6000 NY USA

The occurrence of time-dependent cavitation and tensile stress in an oscillatory oil squeeze film were investigated experimentally. The test apparatus was a simple thrust bearing consisting of two parallel circular plates separated by a thin viscous oil film. During the test, one plate was at rest while tne other (transparent) oscillated in a direction normal to its surface. This test configuration was chosen to avoid the rotational motion and complicated geometry of a squeeze film Journal bearing. The frequency of oscillation was in the range of 5 to 50 Hz and was controlled by an electro-magnetic exciter. The process of cavity formation and its subsequent development was recorded by a high-speed video camera. Concomitant pressure in the oil film was measured both within and without the cavitation region. It was found that both tensile stress and cavities existed in a squeeze film under certain working conditions.

关键词： dynamically loaded journal bearing, squeeze film effect, time-dependent cavitation.

Occurrence of bistable state in squeeze film damper rotor system

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Journal of Harbin Institute of Technology(New Series) 2000年第2期7卷 75-77页

作者：陈照波焦映厚刘占生夏松波蒋书运 School of Power Engineering Harbin Institute of Technology Harbin 150001 China Tsinghua University Beijing 100084 China

Presents the study on the law governing the occurrence of bistable state in the squeeze film damper supported rigid rotor system by theoretical calculations,the way q calculating the bistable state characteristics, the analysis of bistable state characteristics using bearing parameter B and mass eccentricity U as basic parameters, and the ranges of B and U values established, and concludes that the occurrence of bistable state can be avoided provided design parameters are properly selected so that the B and U values are not in the ranges established. This makes it convenient to optimize the squeeze film damper design parameters.

关键词： squeeze film damper bistable state rotor system

Tensile Strength of squeeze Cast Carbon Fibers Reinforced Al-Si Matrix Composites

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Journal of Minerals and Materials Characterization and Engineering 2011年第2期10卷 127-141页

作者： Ahmed A. Moosa Kahtan K. Al-Khazraji Osama S. Muhammed Department of Production Engineering and Metallurgy University of Technology Baghdad Materials Engineering Department University of Technology Baghdad Iraq.

squeeze casting is a pressure casting process in which molten metal is solidified under the direct action of a pressure. In squeeze casting, the relationship between the process parameters and the quality of the squeeze cast components is not fully understood;thus the need for more studies in this area of technology for better understanding of the process. The present work encompasses studying the effect of direct squeeze casting process parameters on the production of (3 and 20%) volume fraction carbon fibers (CF) reinforced Al-Si matrix composites. The evaluated process parameters are squeeze pressure in the range (7.5-53) MPa, die preheating temperature (100,200,300)°C, pouring temperature (700,780)°C, squeeze time (30 sec.), and delay time (5 sec.). The results show a good distribution of the matrix between the carbon fibers when using higher casting pressures of (38 and 53MPa), lower pouring temperature of (700°C) and lower die temperatures of (100 and 200°C). Increasing the carbon fibers volume fraction had led to increasing the tensile strength. The using of higher pressure (53MPa), lower pouring temperature (700°C), and lower die temperature (200°C) have increased the ultimate tensile strength of the CF/Al-Si composites to (183MPa) when compared to that of the nonreinforced alloy which was (168MPa) because of the increased bonding, decreased shrinkage defects and fibers degradation based on the results. Also, UTS is increased at P=38MPa, Tp=700°C, and Td=100°C.

关键词： Tensile Strength squeeze Cast Carbon Fibers

Elevated Temperatures Tensile Characteristics of Cast A356/Al<sub>2</sub>O<sub>3</sub>Nanocomposites Fabricated Using a Combination of Rheocasting and squeeze Casting Techniques

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Materials Sciences and Applications 2011年第5期2卷 390-398页

作者： El-Sayed Youssef El-Kady Tamer Samir Mahmoud Mohamed Abdel-Aziz Sayed Mechanical Engineering Department Faculty of Engineering King Khalid University (KKU) Abha Kingdom of Saudi Arabia.

In the present investigation, the tensile properties of A356/Al2O3 nanocomposites at both ambient and elevated temperatures were studied. The A356/Al2O3 nanocomposites were fabricated using a combination between the rheocasting and squeeze casting techniques. The A356 matrix alloy was reinforced with Al2O3 nanoparticulates having average sizes of 60 nm and 200 nm with different volume fractions up to 5 vol%. The results revealed that the A356/Al2O3 nanocomposites exhibited better mechanical properties than the A356 monolithic alloy. Such improvement in the mechanical properties was observed at both room and elevated temperatures up to 300°C. Increasing the volume fraction and/or reducing the size of Al2O3 nanoparticulates increase both the tensile and yield strengths of the nanocomposites.

关键词： Nanocomposites Mechanical Properties Rhecocasting squeeze Casting Aluminum Alloys

A Monolithic, FEM-Based Approach for the Coupled squeeze Film Problem of an Oscillating Elastic Micro-Plate Using 3D 27-Node Elements

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Journal of Applied Mathematics and Physics 2013年第6期1卷 20-25页

作者： Anish Roychowdhury Arup Nandy C. S. Jog Rudra Pratap 1Department of Mechanical Engineering Indian Institute of Science Bangalore India 2Center for Nano Science and Engineering Indian Institute of Science Bangalore India Department of Mechanical Engineering Indian Institute of Science Bangalore India

In this study we describe an FEM-based methodology to solve the coupled fluid-structure problem due to squeeze film effects present in vibratory MEMS devices, such as resonators, gyroscopes, and acoustic transducers. The aforementioned devices often consist of a plate-like structure that vibrates normal to a fixed substrate, and is generally not perfectly vacuum packed. This results in a thin film of air being sandwiched between the moving plate and the fixed substrate, which behaves like a squeeze film offering both stiffness and damping. Typically, such structures are actuated electro-statically, necessitating the thin air gap for improving the efficiency of actuation and the sensitivity of detection. To accurately model these devices the squeeze film effect must be incorporated. Extensive literature is present on mod- eling squeeze film effects for rigid motion for both perforated as well as non-perforated plates. Studies which model the plate elasticity often use approximate mode shapes as input to the 2D Reynolds Equation. Recent works which try to solve the coupled fluid elasticity problem, report iterative FEM-based solution strategies for the 2D Reynolds Equation coupled with the 3D elasticity Equation. In this work we present a FEM-based single step solution for the coupled problem at hand, using only one type of element (27 node 3D brick). The structure is modeled with 27 node brick elements of which the lowest layer of nodes is also treated as the fluid domain (2D) and the integrals over fluid domain are evaluated for these nodes only. We also apply an electrostatic loading to our model by considering an equivalent electro-static pressure load on the top surface of the structure. Thus we solve the coupled 2D-fluid-3D-structure problem in a single step, using only one element type. The FEM results show good agreement with both existing analytical solutions and published experimental data.

关键词： squeeze Film Damping Coupled Problem 27-Node Brick Micro-Plate