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Research Review of Principles and Methods for Ultrasonic Measurement of Axial Stress in Bolts

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Chinese Journal of Mechanical Engineering 2020年第1期33卷 44-59页

作者： Qinxue Pan Ruipeng Pan Chang Shao Meile Chang Xiaoyu Xu School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Key Laboratory of Fundamental Science for Advanced Machining Beijing Institute of TechnologyBeijing 100081China

Bolts are important fasteners indispensable in the manufacturing field for their advantages, which include convenient assembly and disassembly, easy maintenance, refastenability to prevent looseness, and the avoidance of a phase change in the connected material composition. The precise control of the tightening force in bolts is closely related to the safety and reliability of the connected equipment or structure. Although there are many methods for estimating the tightening force applied to a bolt during assembly, poor accuracy in controlling the preload during the tightening process and a lack of monitoring to determine the residual axial force in service remain issues in evaluating the safety of bolted assemblies. As a nondestructive testing technology, ultrasonic measurement can be applied to successfully address these issues. In order to help researchers understand the theoretical basis and technological development in this field and to equip them to conduct further in-depth research, in this review, the basic knowledge describing the state of stress and deformation of bolts, as well as conventional testing methods are summarized and analyzed. Then, through a review of recent research of the ultrasonic measurement of the axial stress in bolts, the influence of the e ective stressed length and temperature are analyzed and proposed methods of calibration and compensation are reviewed. In order to avoid coupling errors caused by traditional piezoelectric transducers, two newly proposed ultrasonic coupling technologies, the electromagnetic acoustic transducer(EMAT) and the permanent mounted transducer system(PMTS), are reviewed. Finally, the new direction of research of the detection of residual axial stress in in-service bolts that have been assembled to yield is discussed.

关键词： Bolted connections Axial stress Ultrasonic waves Influencing factors Coupling techniques

Observations of Dominant Behaviors and Habits of an Effective Leader

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Observations of Dominant Behaviors and Habits of an Effectiv...

Experimental investigation of seismic performance of concrete-filled glass fiber reinforced polymer tubular columns

作者： Ron Drew Stone Center for Performance and ROI

Leadership behavior is at the center of organization performance.Organizations dedicate significant resources to develop leaders so that work teams will achieve organization goals.Theories abound about the traits, characteristics and behaviors that make for the best leaders.Since team members and others who work closely with leaders are in a good position to know the answers, I asked these employees what type of leader and which leader behaviors influence them to do the work and stay connected with the organization.The research identified numerous behaviors and habits that facilitate communication, trust, respect, working relationships, and positive performance.These findings are arranged in two guides, each with an array of behaviors.One guide is for building leadership character and the other is for influencing connection conversations.Both guides are beneficial to leaders as they engage their team to achieve organization goals.A leadership workshop is forthcoming that focuses on applying the guides along with tools for leaders to connect with teams and achieve individual and organization performance goals.

关键词： connections Respect Trust Leader Behavior Habits Willingness Character Compassion Performance

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Journal of Harbin Institute of Technology(New Series) 2011年第5期18卷 37-43页

作者：关宏波王清湘 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology College of Civil Engineering and Architecture Liaoning Technical University

A reinforced concrete (RC) column and four concrete filled GFRP tubular columns,which are subjected to combined axial compression and lateral cycle loading,were tested in order to investigate the seismic performance of composite construction concrete filled glass fiber reinforced polymer (GFRP) tubular (CFFT) columns.The results indicated that concrete-filled GFRP tubular columns exhibit considerable influence over the seismic performance of columns by providing hoop confinement to the core concrete.The concrete filled GFRP tubular columns exhibit significant improvement over traditional RC columns in both ultimate strength and ductility.Different column-footing connection modes do not affect the strength and ductility of concrete filled GFRP tubular columns.The strength of concrete filled GFRP tubular columns under high axial compression load conditions are slightly increased,however,ductility declined.

关键词： concrete columns connections ductility concrete filled GFRP tubular column seismic

Fragility Assessment of Pre-Northridge Steel Moment Frames Using Finite-Length Plastic Hinge Elements and Concentrated Plasticity Fracture Elements

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Computer Modeling in Engineering & Sciences 2019年第9期120卷 657-676页

作者： Filipe L.A.Ribeiro Andre RBarbosa Luis CNeves National Laboratory of Civil Engineering(LNEC)&CERIS-Civil Engineering Research and Innovation for Sustainability DECivilUniversity of LisbonLisbonPortugal School of Civil and Construction Engineering Oregon State UniversityOregonUSA and University of BristolBristolUK Resilience Engineering Research Group University of NottinghamNottinghamUK.

Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the United States of America.In this study,the performance of the 3-and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures,and their uncertainty.This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment.The results show that considering brittle connections leads to significantly l arger d rift demands a nd t o h igher r epair costs,particularly under intense ground shaking.New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections.

关键词： Brittle fracture finite-length p lastic h inge f ragility c urves r epair c ost ratio welded-flange connections

Avoiding sealing failure of flanged connection for tubes made of dissimilar materials subjected to elevated temperature

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Nuclear Science and Techniques 2019年第1期30卷 107-112页

作者： Qi-Ming Li Chong Zhou Jian Tian Yao Fu Yang Zou Na-Xiu Wang Shanghai Institute of Applied Physics Chinese Academy of Sciences

Carbonic composite materials and ceramics appear to be excellent structural materials for parts subjected to very high temperatures in molten salt reactors(MSRs), in which the reactor core outlet temperature is normally above 700℃. Because of the high temperature,there are major challenges in the sealing of flanged connections for tubes made of alloys and nonmetallic materials. In this study, an improved method for sealing bolted flange connections for tubes made of dissimilar materials at high temperature is analyzed. The study focuses on the compensation mechanism for the difference in thermal expansion between the bolts and the flanges. An angle is introduced for the sealing surface in the flanged connection to provide effective sealing. The arctangent of the angle is the ratio of the thickness between the theoretical core of the sealing surface and the outside end face of the flange to the distances between the axis of the flanged joint and the theoretical core of the sealing surface of the flange; the sealing surface of the flange, which is made of the same material as the fastening assemblies, faces the fastening assemblies. To ensure effective sealing, the frictional coefficient between the two sealing surfaces should not exceed the tangent of the angle. This result does not agree well with the solution given by previous researchers. Further, in the modified flanged connection, the compression of each bolt in the clamped condition is increased to maintain the compaction force unchanged without increasing the number of bolts on the flanged joint.

关键词： Sealing Composite flanged connections Thermal expansion Mechanical analysis Molten salt reactors

Women on boards of directors and corporate philanthropic disaster response

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China Journal of Accounting Research 2012年第1期5卷 83-99页

作者： Ming Jia Zhe Zhang Northwestern Polytechnical University Xi'an Jiaotong University

In this study we conduct firm-level analysis of the impact of women in the boardroom on corporate philanthropic disaster response(CPDR).We propose that CPDR contains agency costs and that female directors are more likely to restrain the associated agency costs of CPDR.We predict a negative relationship between the ratio of women on boards of directors(WoBs) and philanthropic contribution,which is weaker in firms with political connections and stronger in firms with better-developed institutional environments.Data was collected from the philanthropic responses to the Wenchuan earthquake on May 12,2008 of privately-owned listed Chinese firms.The results support the hypothesized negative relationship,which is found to be weaker in firms with political connections.However,marketization-related factors do not significantly moderate this relationship.These results indicate that CPDR contains agency costs and that female directors do not facilitate the corporate donation process,but rather evaluate the benefits and restrain the associated agency costs.

关键词： Women on boards of directors Political connections

Discrete-Time Langevin Motion in a Gibbs Potential

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Applied Mathematics 2012年第12期3卷 2032-2037页

作者： Reza Rastegar Alexander Roitershtein Vadim Roytershteyn Jiyeon Suh Department of Electrical and Computer Engineering University of California San Diego San Diego USA Department of Mathematics Grand Valley State University Allendale USA Department of Mathematics Iowa State University Ames USA

We consider a multivariate Langevin equation in discrete time, driven by a force induced by certain Gibbs’states. The main goal of the paper is to study the asymptotic behavior of a random walk with stationary increments (which are interpreted as discrete-time speed terms) satisfying the Langevin equation. We observe that (stable) functional limit theorems and laws of iterated logarithm for regular random walks with i.i.d. heavy-tailed increments can be carried over to the motion of the Langevin particle.

关键词： Langevin Equation Dynamics of a Moving Particle Multivariate Regular Variation Chains with Complete connections

Instructional Design and Training of Typical Simulation Project——water supply and monitoring system

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Instructional Design and Training of Typical Simulation Proj...

Contact Spot Temperature and the Temperature of External Surfaces in an Electrical Connection

2013教育技术与信息系统国际会议

作者： Yafeng. Zhang Qinghai Architectural Vocational and Technical College

In order to foster students’ ability of analyzing and solve problems and improve their practical ability, we designed a comprehensive practical instructional simulation which helps the students to have a clear understanding of water supply and monitoring theory based on the curriculum. This simulation combines the water supply project and its monitoring system tightly. The students should be able to complete the installation and adjustment of the simulation after finishing the related courses such as " water supply and drainage engineering ", " electric control ", " pipe installation process ", " electric construction technology " and the installation of pipelines. Among the numerous ways of water supply, the combination of pool, water tank and pump is widely used. So we choose this typical combination as our simulation course. The main function of monitoring is to control the pump by computer to optimize the system and fulfill a high-efficient but economic operation. The water level in the tank and the pump status are the key parts to be monitored.

关键词： Typical simulation project Water supply equipment installation connections monitoring Operation adjustment

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Contact Spot Temperature and the Temperature of External Sur...