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Evaluation and Empirical research of critical condition Design of BT Mode

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Evaluation and Empirical research of Critical Condition Desi...

Review of research on loosening of threaded fasteners

2011 International Conference on Management Science and Intelligent Control(ICMSIC 2011)

作者： Wang Chao Department of Civil Engineering and Architecture Anhui University of science &technology Huainan China Yao Chuanqin Department of Civil Engineering and Architecture Anhui University of science & technology Huainan China

The critical condition evaluation of BT mode is adopted to balance rights and benefits between government and investor. This paper aims to describe and analyze repurchasing radix design, yield design, and repurchasing mode design. Apply the fuzzy comprehensive evaluation to set the evaluation model, which includes 8 evaluable factors reflected in the evaluation, and do the preliminary empirical research of the model and get the primary weighing of the 8 factors through the empirical research. By calculating and analyzing, the model truly reflects the interest relation between the government and the investor. Using this model, theoretical foundation to BT mode decision-negotiation is offered.

关键词： BT mode critical condition fuzzy comprehensive evaluation

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Friction 2022年第3期10卷 335-359页

作者： Hao GONG Xiaoyu DING Jianhua LIU Huihua FENG School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Loosening of threaded fasteners is a key failure mode,which is mainly caused by the slippage and friction behaviors on the thread and bearing surfaces,and will affect the integrity and reliability of products.Numerous scholars have conducted research on the loosening of threaded fasteners;however,comprehensive reviews on the loosening of threaded fasteners have been scarce.In this review article,we define loosening as a loss of preload and divide it into non-rotational and rotational loosening.The causes and mechanisms of non-rotational and rotational loosening are summarised.Some essential topics regarding loosening under transverse vibration have also attracted significant attention and have been investigated widely,including the loosening curve,critical condition of loosening,and influencing factors of loosening.The research carried out on these three topics is also summarised in this review.It is believed that our work will not only help new researchers quickly understand the state-of-the-art research on loosening,but also increase the knowledge of engineers on this critical subject.In the future,it is important to conduct more quantitative research on local slippage accumulation,and the relationship between local slippage accumulation and rotational loosening,which will have the potential to comprehensively unravel the loosening mechanism,and effectively guide the anti-loosening design of threaded fasteners.

关键词： threaded fasteners loosening vibration loosening curve critical condition influencing factors

Sealing Performance and Optimization of a Subsea Pipeline Mechanical Connector

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Chinese Journal of Mechanical Engineering 2018年第1期31卷 142-155页

作者： Li-Quan Wang Zong-Liang Wei Shao-Ming Yao Yu Guan Shao-Kai Li College of Mechanical and Electrical Engineering Harbin Engineering University Advanced Manufacturing Research Centre with Boeing The University of Sheffield

Researchers seldom study the optimum design of a mechanical connector for subsea oil-gas pipeline based upon the sealing performance. An optimal design method of a novel subsea pipeline mechanical connector is presented. By analyzing the static metal sealing mechanism, the critical condition of the sealing performance is established for this connector and the formulation method of the contact pressure on the sealing surface is created. By the method the minimum mean contact pressure of the 8.625 inch connector is calculated as 361 MPa, which is the constraint condition in the optimum design of connector.The finite element model is created in ANSYS Parametric Design Language(APDL) and the structure is optimized by the zero-order method, with variance of contact pressure as the objective function, and mean contact pressures and plastic strains as constraint variables. The optimization shows that variances of contact pressure on two sealing surfaces decrease by 72.41% and 89.33%, respectively, and mean contact pressures increase by 31.18% and 52.84%, respectively. The comparison of the optimal connectors and non-optimal connectors in the water pressure experiments and bending experiments shows that the sealing ability of optimized connectors is much higher than the rated pressure of 4.5 MPa, and the optimal connectors don’t leak under the bending moment of 52.2 kN·m.This research provides the formulation to solve contact pressure on the sealing surface and a structure optimization method to design the connectors with various dimensions.

关键词： Mechanical connector Sealing mechanism Sealing performance critical condition Minimum mean contact pressure Variance

Prediction of critical conditions for Dynamic Recrystallization in 316LN Austenitic Steel

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Journal of Iron and Steel Research(International) 2016年第3期23卷 238-243页

作者： Xin-gang LIU Li-ge ZHANG Rong-sheng QI Lei CHEN Miao JIN Bao-feng GUO Key Laboratory of Advanced Forging & Stamping Technology and Science(Yanshan University) Ministry of Education of China Yanshan University Library Yanshan University National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan University

Hot compression experiments conducted on a Gleeble-3500thermo-mechanical simulator and metallographic observation tests were employed to study the critical conditions of dynamic recrystallization（DRX）of 316 LN austenitic stainless steel.The true stress-true strain curves of 316 LN were obtained at deformation temperatures ranging from 900℃to 1 200℃and strain rates ranging from 0.001s-1 to 10s-1.Based on the above tests,the critical conditions of DRX were determined and compared with those obtained from work-hardening theory and the Cingara-McQueen flow stress model.Furthermore,the microstructure was observed to validate the calculated results.The ratio of critical strain to peak strain（εc/εp）for 316 LN was determined,and the quantitative relationship between the critical strain and the deformation parameters of 316 LN was elucidated.The results demonstrated that the onset of DRX corresponds to the constant normalized strain hardening rate（Γ）,namely,the critical strain hardening rateΓcfor316LN is equal to 0.65.

关键词： 316LN austenitic stainless steel hot deformation dynamic recrystallization critical condition

Flume Experiment on Stream Blockage by the Debris Flow From Tributary

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四川大学学报（工程科学版） 2005年第S1期37卷 64-70页

作者： He, Yiping Guo, Zhixue Li, Yong Cui, Peng Wang, Zhaoyin Dept. of Hydraulic and Hydro-electrical Eng. Tsinghua Univ. Beijing 100084 China Chengdu Inst. of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China State Key Lab. of Hydraulics and Mountain River Eng. Sichuan Univ. Chengdu 610065 China

Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area,which takes place when large quantities of sediment transported by debris flow reaches a river channel causing its complete or partial blockage.The dam formed by debris flow may causes upstream and downstream flooding,and presents great threat to people and property.Because of the catastrophic influence on people and property,debris-flow dam has attracted many attentions from the researchers and local adm...

关键词： Debris flow blockage critical condition flume experiment

Nonlinear dynamical behavior of shallow cylindrical reticulated shells

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Applied Mathematics and Mechanics(English Edition) 2007年第2期28卷 151-156页

作者：王新志梁从兴韩明君叶开沅王钢 School of Science Lanzhou University of Technology Physics College Lanzhou University Design Art Academy Lanzhou University of Technology

By using the method of quasi-shells , the nonlinear dynamic equations of three-dimensional single-layer shallow cylindrical reticulated shells with equilateral triangle cell are founded. By using the method of the separating variable function, the transverse displacement of the shallow cylindrical reticulated shells is given under the conditions of two edges simple support. The tensile force is solved out from the compatible equations, a nonlinear dynamic differential equation containing second and third order is derived by using the method of Galerkin. The stability near the equilibrium point is discussed by solving the Floquet exponent and the critical condition is obtained by using Melnikov function. The existence of the chaotic motion of the single-layer shallow cylindrical reticulated shell is approved by using the digital simulation method and Poincare mapping.

关键词： reticulated shells method of quasi-shells chaotic motion critical condition

Investigation of Turbulent Transition in Plane Couette Flows Using Energy Gradient Method

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Advances in Applied Mathematics and Mechanics 2011年第2期3卷 165-180页

作者： Hua-Shu Dou Boo Cheong Khoo Temasek Laboratories National University of Singapore10 Kent Ridge CrescentSingapore 117411Singapore Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore

The energy gradient method has been proposed with the aim of better understanding the mechanism of flow transition from laminar flow to turbulent flow.In this method,it is demonstrated that the transition to turbulence depends on the relative magnitudes of the transverse gradient of the total mechanical energy which amplifies the disturbance and the energy loss from viscous friction which damps the disturbance,for given imposed disturbance.For a given flow geometry and fluid properties,when the maximum of the function K(a function standing for the ratio of the gradient of total mechanical energy in the transverse direction to the rate of energy loss due to viscous friction in the streamwise direction)in the flow field is larger than a certain critical value,it is expected that instability would occur for some initial disturbances.In this paper,using the energy gradient analysis,the equation for calculating the energy gradient function K for plane Couette flow is derived.The result indicates that K reaches the maximum at the moving walls.Thus,the fluid layer near the moving wall is the most dangerous position to generate initial oscillation at sufficient high Re for given same level of normalized perturbation in the domain.The critical value of K at turbulent transition,which is observed from experiments,is about 370 for plane Couette flow when two walls move in opposite directions(anti-symmetry).This value is about the same as that for plane Poiseuille flow and pipe Poiseuille flow(385-389).Therefore,it is concluded that the critical value of K at turbulent transition is about 370-389 for wall-bounded parallel shear flows which include both pressure(symmetrical case)and shear driven flows(anti-symmetrical case).

关键词： Flow instability turbulent transition plane Couette flow energy gradient energy loss critical condition

critical flow-storm approach to total maximum daily load (TMDL) development:an analytical conceptual model

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Frontiers of Environmental Science & Engineering 2008年第3期2卷 267-273页

作者： Harry X.ZHANG Shaw L.YU CH2M HILL 15010 Conference Center DriveChantillyVA 20151–3801USA Department of Civil and Environmental Engineering Thornton HallUniversity of VirginiaCharlottesvilleVA 22904–4742USA

One of the key challenges in the total maximum daily load(TMDL)development process is how to define the critical condition for a receiving waterbody.The main concern in using a continuous simulation approach is the absence of any guarantee that the most critical condition will be captured during the selected representative hydrologic period,given the scarcity of long-term continuous data.The objectives of this paper are to clearly address the critical condition in the TMDL development process and to compare continuous and event-based approaches in defining critical condition during TMDL development for a waterbody impacted by both point and nonpoint source pollution.A practical,event-based critical flow-storm(CFS)approach was developed to explicitly addresses the critical condition as a combination of a low stream flow and a storm event of a selected magnitude,both having certain frequencies of occurrence.This paper illustrated the CFS concept and provided its theoretical basis using a derived analytical conceptual model.The CFS approach clearly defined a critical condition,obtained reasonable results and could be considered as an alternative method in TMDL development.

关键词： critical condition critical flow-storm(CFS)approach total maximum daily load(TMDL) conceptual model derived analytical model nonpoint source pollution

In Sickness and in Health

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ChinAfrica 2015年第12期7卷 54-56页

作者： Li Xiaoyu

WANG Lihui, head nurse at the China-aided Ebola diagnosis and treatment center in LiberJan capital Monrovia will never forget that incident last winter when she and her team battled through the night to save the life ... 详细信息

关键词： diagnosis and treatment critical condition table tennis