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FOrCE rEDUCTION OF FLOW ArOUND A SINUSOIDAL WAVY CYLINDEr

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Journal of Hydrodynamics 2009年第3期21卷 308-315页

作者： ZOU Lin LIN Yu-feng school of mechanical and Electronic engineering Wuhan University of Technology Wuhan 430070 China Dep.r.ment of mechanical engineering The Hong Kong Polytechnic University Hong Kong China

A large eddy simulation of cross-flow around a sinusoidal wavy cylinder at re = 3000 was p.r.ormed and the load cell measurement was introduced for the validation test. The mean flow field and the near wake flow structures were presented and comp.r.d with those for a circular cylinder at the same reynolds number. The mean drag coefficient for the wavy cylinder is smaller than that for a corresponding circular cylinder due to the formation of a longer wake vortex generated by the wavy cylinder. The fluctuating lift coefficient of the wavy cylinder is also greatly reduced. This kind of wavy surface leads to the formation of 3-D free shear layers which are more stable than p.r.ly 2-D free shear layers. Such free shear layers only roll up into mature vortices at further downstream position and significantly modify the near wake structures and the pressure distributions around the wavy cylinder. Moreover, the simulations in laminar flow condition were also p.r.ormed to investigate the effect of reynolds number on force reduction control.

关键词： wavy cylinder force reduction Large Eddy Simulation (LES) reynolds number effect

Improvement on strip flatness of cold temp.r.mills by modifying roll contour shape

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Journal of University of Science and Technology Beijing 2004年第3期11卷 251-255页

作者： Xiaoyan Li Jie Zhang Xianlin Chen Jianguo Cao Haixia Li mechanical engineering school, University of Science and Technology Beijing, Beijing 100083, china Mech. Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temp.r.mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finiteelement model, the effects of roll contours (ground and wear) on strip profile were *** roll bending effect on strip thickness was also analyzed. It is pointed out that there are somespecial features of flatness control in the temp.r.mill: during temp.r.rolling, roll deformation isslight due to small rolling load, and the loaded roll gap profile mainly depends on work rollcontour, while the backup.r.ll has a little effect on gap crown; the effect of bending force ongauge can not be ignored due to the coupling between flatness control and gauge control. A new rollcontour arrangement adaptable to the mill was presented and has been put into practical *** application of the new set of rolls showed some good results: larger crown control range of workroll bender, higher rolling stability, better strip profile and flatness quality.

关键词： cold rolling temp.r.mill strip shape control roll contour arrangement bending

DISTrIBUTIONS OF MICrOSTrUCTUrES IN QUENCHED STEELS AS rEVEALED BY COMpUTEr SIMULATION

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 788-793页

作者： L. Zhou and X.Q. Wei school of Chemistry and Materials Science and school of mechanical/electrical engineering, Nanchang University, Nanchang 330047, china

A cellular automaton model of heat transfer and structural development in quenching steels has been developed and programmed for a three-dimensional computer simulation. A previous study has validated the simulation method by agreements of simulated cooling curves and hardenability with rep.r.ed exp.r.mental data. In present work, a series of simulated quenching exp.r.ments for steel 1080 and 4140 steel have been carried out. With five adjustable p.r.meters, a large variety of cooling conditions has been created and applied to the simulated quenching. Effect of delayed quenching and the associated phenomenon of inverse hardening have been addressed with emphasis.

关键词： microstructure steel computer simulation

rolling Element Bearing Diagnostics by Combination of Envelope Analysis and Wavelet Transform

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Journal of University of Science and Technology Beijing 2001年第1期8卷 69-74页

作者： Ying Tang, Qiao Sun mechanical engineering school, University of Science and Technology Beijing, Beijing 100083, china Dep.r.ment of mechanical engineering, University of Calgary Calgary Alberta T2N 1N4, Canada Univ Sci & Technol Beijing Sch Mech Engn Beijing 100083 Peoples R China Univ Calgary Dept Mech Engn Calgary AB T2N 1N4 Canada

rolling element-bearing diagnostics has been studied over the last thirty years, and envelope analysis is widely recognized as being the best ap.r.ach for detection and diagnosis of rolling element bearing incipient failure. But one of the on-going difficulties with envelope technique is to determine the best frequency band to envelop. Here, wavelet transform technique is introduced into envelope analysis to solve the problem by capturing bearing defects-sensory scales (i.e. frequency bands). A modulated Gaussian function is chosen to be the analytical wavelet because it coincides well with bearing defect-induced vibration signal patterns. Vibration signals measured from railway bearing tests were studied by the proposed method. Cases of bearings with single and multiple defects on inner and outer race under different testing conditions are presented. Exp.r.mental results showed that the proposed method allowed a more accurate local description and sep.r.tion of transient signal p.r., which were caused by impacts between defects and the mating surfaces in the bearing. The combination method provides an effective signal detection technique for rolling element-bearing diagnostics.

关键词： continuous wavelet transform envelope analysis rolling element bearing diagnostics

Development of Flow Stress of AISI H13 Die Steel in Hard Machining

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Journal of Wuhan University of Technology(Materials Science) 2007年第2期22卷 187-190页

作者：闫洪 school of mechanical&electrical engineering Nanchang University

An ap.r.ach was presented to characterize the stress response of workpiece in hard machining, accounting for the effect of the initial workpiece hardness in addition to temp.r.ture, strain and strain rate on flow stress in this pap.r. AISI H13 die steel was chosen to verify this methodology. The proposed flow stress model demonstrates a good agreement with exp.r.mental data. Therefore, the proposed model can be used to predict the corresponding flow stress-strain response ofAISl H13 die steel with variation of the initial workpiece hardness in hard machining.

关键词： flow stress hard machining finite element modeling AISI H13 die steel

Adiabatic Shear Bands in 30CrNi_3MoV Structural Steel Induced during High Speed Cutting

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Journal of Materials Science & Technology 2004年第6期20卷 775-778页

作者： Chunzheng DUAN and Minjie WANGKey Laboratory of Ministry of Education for precision and Non-traditional Machining, school of mechanical engineering, Dalian University of Technology, Dalian 116024, china Lab. of Non-traditional Machining Sch. of Mech. Eng. Dalian Univ. of Technol. Dalian 116024 China

The width and spacing of adiabatic shear bands (ASBs) in the serrated chips generated during high speed orthogonal cutting of 30CrNi3MoV structurai steel were measured by opticai microscopy (OM), the temp.r.ture rise in the shear band was estimated. The microstructures of the ASBs were also characterized by SEM and TEM. The results show that the width and spacing of ASBs decrease with the increase of the cutting speed. The further observations show that the microstructure between the matrix and the center of the ASB gradually changes, and that the martensitic phase transformation, carbide precipitation and recrystallization may occur in the ASB.

关键词： Adiabatic shear band (ASB) recrystallization Orthogonal cutting

Mathematical Model for the Drying process of Granular Materials in a Fluidized Bed

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 296-300页

作者： Xiulan Huai, Li Wang, Zhiyun Qu ( mechanical engineering school, University of Science and Technology Beijing, Beijing 100083, china Chemical Industry research Institute of Shanxi, Taiyuan 030031, china) mechanical engineering school University of Science and Technology Beijing Beijing 100083 China Chemical Industry research Institute of Shanxi Taiyuan 030031 China

The exp.r.ment of granular materials, barley, drying in a fluidized bed was carried out to investigate the influence of the factors, inlet air temp.r.ture, air moisture, bed height and original moisture content of the dried materials on drying process. Based on the exp.r.mental data, a corresponding mathematical model is presented. As a conclusion, a higher inlet air temp.r.ture and a reasonable bed height should be used so as to increase the dring rate and to improve the product quality.

关键词： fluidization granular materials drying, exp.r.mental investigation mathematical model Information

DYNAMIC rESpONSE OF SHApE MEMOrY ALLOY SYSTEM AND ITS VIBrATION CONTrOL

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Chinese Journal of mechanical engineering 2000年第4期13卷 312-317页

作者： Wei ZhiSun Dongchang Tan runhua (school of mechanical engineering,Hebei University of Technology) 河北工业大学天津

A hysteric model is represented to describe the dependence of restoring force on deformation of pseudoelastic *** dynamic response of the system is investigated by means of mathematical *** result shows that this kind of vibration absorbing system can sup.r.ss vibration with large amplitude ***,the vibration absorbing system can work in optimum state by adjusting temp.r.ture and using piezoelectric sensors and actuators.

关键词： Shape memory alloy pseudoelasticity Mathematical model Dynamic response Vibration control

Characteristics of acoustic emission signals in damp cracking coal rocks

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Mining Science and Technology 2010年第1期20卷 143-147页

作者： TANG Shoufeng, TONG Minming, HU Junli, HE Xinmin school of Information and electrical engineering, china University of Mining & Technology, Xuzhou 221008, china [a] school of Information electrical engineering China University of Mining & Technology Xuzhou 221008 China

A uniaxial load exp.r.ment on coal rocks at different stress rates was carried out, based on the characteristics of acoustic emission (AE) signals in cracking coal rocks, decomposition, de-noising and reconstruction for the AE signals through wavelet packet transform for solving the current problems created by the presence of noise in AE signals and the existing problems in AE signal processing. The results show that the various characteristics of AE signals in coal rocks cracking under different situations can be clearly reflected, after the AE signals are de-noised by the wavelet packet. Comp.r.d to dry coal rocks, the number of AE occurrences in damp coal rocks was significantly reduced, as well as the average amplitude. The number of AE occurrences in damp and dry coal rocks clearly increased with increases in the loading rate, but the largest amplitude of the AE signals in damp coal rocks has been reduced. There is no clear evidence of change in dry coal rocks.

关键词： coal rocks cracking Acoustic Emission (AE) signal processing wavelet packet analysis de-noising