Evaluation of Solar Temperature Field under Different Wind Speeds for Shanghai 65 m Radio Telescope

Hongliang Qian,Deshen Chen,Feng Fan,Ye Liu,Shi-zhao Shen 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.2

The Shanghai 65 m radio telescope is currently the largest full range rotatable radio telescope in Asia. Gravity, wind and temperature are the three main factors which may have a bad effect on the reflector’s surface precision. To study the effect of the thermal deformation caused by daily non-uniform temperature fields on the surface precision of the main reflector, both the temperature field and its effect were studied in detail for two typical days (January 15th and July 15th). The method to simulate temperature fields was studied initially, considering heat conduction, solar radiation, shadowing, air convection, sky radiation and ground radiation. Then, an integral parametric thermal finite element model (FEM) of the telescope was established using the ANSYS thermal analysis module. Finally, the effect of non-uniform temperature fields on the surface precision of the main reflector was estimated in terms of the Root Mean Square (RMS) deformation based on temperature transient analysis. The proposed methods and conclusions drawn can provide valuable information for thermal design, thermal monitoring and thermal control of the Shanghai 65 m radio telescope and other similar giant antenna structures.

Vibration control of rotor system by ultrasonic excited limiter

Hongliang Yao,Qian Zhao,Hao Wu,Bang-chun Wen 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

We propose a novel method with an ultrasonically excited structure as a vibration limiter to control the vibration of rotor systems. Thefriction between the rotor and the limiter is significantly reduced by ultrasonic lubrication, thereby preventing the occurrence of rubbinginducedthermal bowing, which is commonly observed in traditional vibration limiters. In our study, the friction reduction mechanism ofthe ultrasonically excited vibration limiter was first examined based on tribology theory and Hertz contact theory. The vibration controleffects and the alleviation of thermal bowing were then investigated by numerical simulation. Finally, vibration control experiments wereperformed on a Bentley test rig with the ultrasonically excited vibration limiter. The consistency between theoretical and experimentalresults confirmed the effectiveness of the proposed method.

Prediction method for steady-state response of local rubbing blade-rotor systems

Qian Zhao,Hongliang Yao,Qi Xu,Bang-chun Wen 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Blade-rotor systems frequently encounter the problem of blade-to-case rubbing, which affects their safety and stability. Numericalsimulation can be used to predict the steady-state response of these systems. However, such simulation is frequently computationallyexpensive because of the high dimensions of the dynamic model of a blade-rotor system. To overcome this problem, a new method thatcombines the receptance-based dimension-reduction approach with the incremental harmonic balance (IHB) method is presented in thisstudy. First, a dynamic model of a blade-rotor system is developed using the finite element method, and the number of dimensions of themodel is reduced by the receptance method. Subsequently, the steady-state response is obtained by the improved IHB method to convenientlymanage the large number of super-harmonic components of the local rubbing system. Finally, the precision and efficiency of theproposed method is verified by comparing its results with those obtained by the Newmark-b method. The proposed method is found to beefficient in analyzing local rubbing blade-rotor systems with high dimensions, local nonlinearities, and rich super-harmonics.

An Estimate of the Time-varying Temperature Field of the Main Reflector and Subreflector of the Shanghai 65 m Radio Telescope under Solar Illumination

Zhong Jie,Qian Hongliang,Fan Feng,Shen Shizhao 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.1

The time-dependent temperature fields of the reflectors of the Shanghai 65 m radio telescope are investigated numerically, taking account of the non-uniform heating of the reflector surfaces due to solar illumination and the constantly changing ambient air temperature. This paper utilizes a ray casting algorithm to calculate the borderline separating the reflector areas in shadow and in sunshine, aiming to provide an accurate calculation of the solar energy absorbed. Then a ray tracing algorithm is utilized to calculate the total solar energy that is reflected by the main reflector area and received by the subreflector surface area. Finally, the solar energy is used as the main thermal load on the reflector surface to numerically examine the temperature distribution on both the main reflector and the subreflector. The results illustrate that the time-varying temperature fields of the reflectors of a radio telescope due to asymmetric solar illumination can be accurately simulated utilizing the ray casting algorithm and the ray tracing algorithm. The occurring periods and avoidance zones of the overheating of the subreflector are identified, among which the maximum temperature of the subreflector reaches 144.9oC. These dangerous observation zones should be avoided during the operation of the radio telescope.

Fatigue property analysis of U rib-to-crossbeam connections under heavy traffic vehicle load considering in-plane shear stress

Haibo Yang,Hongliang Qian,Ping Wang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.3

In this study, the fatigue property of U rib-to-crossbeam connections in orthotropic steel bridge (OSB) crossbeams under heavy traffic vehicle load was investigated considering the effects of in-plane shear stress. The applicability of an improved structural stress (ISS) method was validated for the fatigue behavior analysis of nonwelded arc-shaped cutout regions in multiaxial stress states. Various types of fatigue testing specimens were compared for investigating the equivalent structural stress, fatigue crack initiation positions, and failure modes with the unified standards. Furthermore, the implications of OSB crossbeams and specified loading cases are discussed with respect to the improved method. The ISS method is proven to be applicable for analyzing the fatigue property of nonwelded arc-shaped cutout regions in OSB crossbeams. The used method is essential for gaining a reliable prediction of the most likely failure modes under a specific heavy traffic vehicle load. The evaluated results using the used method are proven to be accurate with a slighter standard deviation. We obtained the trend of equivalent structural stress in arc-shaped cutout regions and validated the crack initiation positions and propagation directions by comparing them with the fatigue testing results. The implications of crossbeam spans on fatigue property are less significant than the effects of crossbeams.

Multiaxial fatigue behaviors of open-rib to crossbeam joints in orthotropic bridge structures

Haibo Yang,Hongliang Qian,Ping Wang,Pingsha Dong,Fillipo Berto 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.6

The fatigue behavior of welded open rib-to crossbeam joints (ORCJ) in orthotropic bridge structures is investigated using a traction structural stress method. The fatigue behaviors of welded open rib-to crossbeam joints have been a subject of study for decades for ensuring operational safety and future design improvement. A mesh-insensitive combination of traction structural stresses in ORCJ was obtained considering the effect of in-plane shear stress and validated by fatigue test results. The proposed method is advantageous for predicting fatigue cracks that initiate from the crossbeam cutout and propagate along the crossbeam. The investigations carried out with the proposed approach reveal that the normal structural stress decreases with the propagation of fatigue cracks, while the ratio of shear stress to normal stress increases. The effect of shear structural stress is significant for the analysis of fatigue behavior of ORCJ in multiaxial stress states

Effects of Ga-doping on the microstructure and magnetic properties of MnBi alloys

Yang, Yang,Kim, Jong-Woo,Si, Ping-Zhan,Qian, Hui-Dong,Shin, Yongho,Wang, Xinyou,Park, Jihoon,Li, Oi Lun,Wu, Qiong,Ge, Hongliang,Choi, Chul-Jin Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-

<P><B>Abstract</B></P> <P>The low temperature phase Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> (<I>x</I> = 0, 1, 3, 5, and 10) alloys were prepared by induction melting process with subsequent low temperature annealing. The effects of Ga-doping on the crystal structure and magnetic properties of the alloys were systematically studied. The room temperature coercivities of Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> after ball milling increased from 1.43 T for <I>x</I> = 0 to 1.66 T for <I>x</I> = 5, while the saturation magnetization decreased from 60.7 Am<SUP>2</SUP>/kg (<I>x</I> = 0) to 45.1 Am<SUP>2</SUP>/kg (<I>x</I> = 5). The maximum energy product (<I>BH</I>)<SUB>max</SUB> of Mn<SUB>55</SUB>Bi<SUB>44</SUB>Ga powders reached 7.87 MGOe. The Curie temperature of the Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> alloys increased from 633 K to 658 K with increasing Ga concentration in the range of 0 ≤ <I>x</I> ≤ 5.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of doping Ga on the microstructural and magnetic properties of MnBi alloy. </LI> <LI> The MnBi-Ga powders are achieved by surfactant assisted high energy ball milling. </LI> <LI> The maximum energy produce (<I>BH</I>)<SUB>max</SUB> shows 7.87 MGOe for Mn<SUB>55</SUB>Bi<SUB>44</SUB>Ga sample. </LI> <LI> The coercivity of Mn<SUB>55</SUB>Bi<SUB>40</SUB>Ga<SUB>5</SUB> after ball milling reached 1.66 T at room temperature. </LI> <LI> The elevated curie temperature (<I>T</I> <SUB>c</SUB>) by doping Ga makes it a possible candidate for high temperature applications. </LI> </UL> </P>

Static and Seismic Experimental Study of Novel Prefabricated Beam-Column Joints with Elongated-Hole Brackets

Zhang Zhiwei,Li Dong,Wang Huajie,Li Songling,Qian Hongliang,Bi Yanhua,Wang Guoxing,Jin Xiaofei,Fan Feng 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.1

To enhance the structural connectivity of prefabricated steel frame systems and augment their construction effi ciency, this study introduces an innovative prefabricated joint design tailored for square steel columns and H-beams characterized by varying beam heights. This study includes both static loading tests and seismic tests performed on full-scale joints featuring two diff erent beam heights. This investigation involved a comprehensive analysis of the static and seismic performance of the joints, employing various performance metrics such as ultimate load capacities, ultimate rotation angles, hysteresis curves, skeleton curves, stiff ness degradation curves, and ductility coeffi cients, in alignment with established structural codes and standards. The results indicate that the plasticity of the H-beam is fully developed, exhibiting a relative slip phenomenon. Additionally, the joints demonstrate commendable rotational capacity, with hysteresis curves consistently manifesting an inverse S-shape and exhibiting noteworthy stiff ness degradation. Furthermore, the comparison with the unimproved joint shows that the novel joint, in addition to being easy to construct, has better ductility and energy dissipation capacity. The results of the study will provide a technical reference for further optimization and application of prefabricated beam-column joints.