Influence of the Billet Volume Distribution on Macro Deformation and Microstructure Response in Transitional Region of Ti-Alloy Multi-rib Component Under Isothermal Local Loading

Ke Wei,Qing Ma,Haibing Tang,Xiaoguang Fan,Jian Zhang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.12

The folding, die underfilling, rib shifting and average grain size of primary equiaxed were investigated using five different unequal thickness billets in transitional region of Ti-alloy multi-rib component under isothermal local loading and compared with integral loading. In terms of the macro deformation, the results show that the material transfers from the second-loading zone into the first-loading zone and the die underfilling decreases with the initial volume of the first-loading zone increasing, which reduces the risk of folding and rib shifting. However, that folding and rib shifting did not appear during the integral loading. Nevertheless, when the initial volume of the first-loading zone reaches a certain value, the die underfilling is aggravated both in local and integral loading. With respect to the microstructure, as the initial volume of the first-loading zone increases, the average grain size is decreased after the first-loading step, but increased after the second-loading step with consideration of one single loading step, which lead to the grain size being barely influenced by different billet volume distribution under both loading steps.

Effects of Hygrothermal Environment on Tensile Capacity of Adhesive-injected Anchor Bolt of ALC Panel and ETICS

Kewei Ding,Kaili Wang,Yunlin Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.3

The connection between the autoclaved lightweight concrete (ALC) and an external thermal insulation composite system (ETICS) is accomplished by anchors. The anchor is consisted of a connector and an anchor bolt, where the anchor bolt is an important force transmission element. Adhesive is used to install an anchor bolt, and significantly improves the anchoring force of the anchor bolt. However, the hygrothermal environment influences the adhesion of the anchor adhesive, which adversely affects the reliability and security of the ALC panel and ETICS connection. To investigate the effect of high temperature and a humid environment on the anchor bonding performance, 5 sets of durability tests were conducted. Each group of 15 specimens was tested for 0, 15, 30, 45, and 60 thermal rain cycles. The test results reveal that, as the number of cycles increased, the tensile capacity of the adhesive-injected anchor bolts decreased, and the capacity’s discount factor decreased. The discount factors of the anchor bolt tensile load capacity values after 15, 30, 45 and 60 cycles were 85.5%, 72.1%, 56.2%, and 50.4%, respectively. A prediction model was established based on the relationship between the number of thermal rain cycles and the tensile capacity. Based on the anchor bolt tensile capacity requirements, the model can calculate the number of cycles over which the adhesive-injected anchor bolts need in a hygrothermal environment must be tested, reinforced, and replaced to ensure a good connection between the ALC panel and an ETICS.

Relaxation Behavior and Time-Temperature Superposition (TTS) Profiles of Thermally Aged Styrene-Butadiene Rubber (SBR)

Kewei Xiang,Guangsu Huang,Siduo Wu,Jing Zheng,Jingyun Huang,Guangxian Li 한국고분자학회 2014 Macromolecular Research Vol.22 No.8

In this work, styrene-butadiene rubber (SBR) was thermally aged at 130 ℃with ageing period up to 4days. The relaxation behavior was studied by dynamic mechanical analysis (DMA) in temperature scanning modeat multifrequencies and the crosslinking network was characterized by swelling method. Glass transition temperature(Tg) and activation energies (Ea) during transition evaluated by Starkweather method were found to increaseafter ageing. Time-temperature superposition (TTS) procedure was performed to obtain master curve and shift factors(αT). The derived αTs were fitted by William-Landel-Ferry (WLF) and Vogel-Fulcher-Tamman (VFT) equations. WLF fitting parameters confirmed decreased free volume fraction ( f ) and thermal expansion coefficient (αf)near Tg versus ageing time. Temperature dependent relaxation properties were examined by VFT fitting parameterD. It was found that the aged SBR displayed more brittle behavior, becoming more and more deviated from Arrheniusfashion. This phenomenon was illustrated by the enhanced intermolecular coupling and severe crosslinkingduring ageing.

Investigation on the Thermal Oxidative Aging Mechanism and Lifetime Prediction of Butyl Rubber

Kewei Xiang,Guangsu Huang,Jing Zheng,Xiaoan Wang,Jingyun Huang 한국고분자학회 2013 Macromolecular Research Vol.21 No.1

Accelerated thermal aging experiments were conducted on butyl rubber materials in order to investigate aging behavior using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), positron annihilation lifetime spectroscopy (PALS), and differential scanning calometry (DSC). The XPS results suggested that the thermal oxidation process took place heterogeneously along the samples thicknesses. The aging mechanism was identified to be crosslinking by means of the combined use of PALS and DSC results. Lifetime and intensity of ortho-positronium (o-ps) diminished, and the glass transition temperature (Tg) increased during aging. The dispersion condition of silica particles, observed by SEM images, showed that the filler agglomerated after aging. Time temperature superposition was carried out using compression set measurements in the temperature range of 100 to 60 oC. The Arrhenius plot clearly exhibited a curvature around 75 oC, and the activation energy dropped from 126.7to 58.8 kJ/mol across this region. Relative importance of different processes, over the entire temperature range, was discussed; lifetime at room temperature was predicted.

Research on Angle Connector in Composite Beam

Kewei Ding,Xinqi Zhang,Yunlin Liu,Shulin He,Jingfeng Wang,Wanyu Shen 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.3

As a critical component for steel beam and concrete slab to work together, the strength of the shear connector affects the flexural load capacity and stiffness of the composite beam. Connectors were generally studied for longitudinal shear resistance. However, transverse shear needs to be considered when the main beam is far away and the transverse connection is weak. In this paper, an angle connector pre-embedded in the precast slab was proposed, and its pre-embedded position makes it exhibit better transverse shear resistance. To assess the strength, stiffness, and slip capacity of the angle connector, two groups of composite beam with precast slabs negative moment flexural were tested, then several finite element groups were simulated in push-out test. The test variable was the existence of angle connectors, and the variables simulated were the yield strength of the angle connector and its flange thickness. The results showed that the composite beam with angle connectors has greater stiffness than ordinary ones, with little difference in flexural strength capacity and less slippage. The results show that angle connectors can replace extending rebars in precast slabs, which will reduce construction costs. In addition, a new design equation was proposed, including the yield strength of the connector and the thickness of its flange which are not unified in the current equations. The simulations determined the strength of the angle connectors in relation to the yield strength of the angle connector and its web thickness.

Integrated Adaptive Control for Spacecraft Attitude and Orbit Tracking Using Disturbance Observer

Kewei Xia,은영호,Taeyang Lee,박상영 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.4

This paper addresses the control issue of the integrated attitude and orbit tracking of spacecraft in the presence of inertia parameter uncertainty and spatial disturbance. By considering thruster as the control actuator, the 6-degree-of-freedom integrated model consisting of attitude and orbit dynamics is formulated. Based on the backstepping design, an adaptive control strategy is developed by exploiting a projected disturbance observer that compensates for the dynamics uncertainty and an adaptive algorithm that counteracts the observer error. Moreover, an optimal control allocation solution is employed to get the control command of each thruster. Stability analysis proves that the overall closed-loop system is ultimately bounded. To validate the proposed control, the hardware-in-the-loop experiment examples are conducted on the ground testbed facility. Simulation and experiment results show that the spacecraft/simulator can achieve the trajectory tracking and attitude synchronization simultaneously.

자동차 디스크 브레이크 시스템의 패드 댐핑과 형상이 스퀼 소음의 발생에 미치는 영향

조커웨이(Kewei Zhou),김철(Cheol Kim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-2

Two-way Fixed Effects Panel and Robustness Testing Model on Regional Economic Convergence

Bi Kewei,Zhang Yanhua 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.9

Study on seismic behavior of fabricated beam-column bolted joint

Yu Zhang,Kewei Ding 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.6

To better promote the development of fabricated buildings, this paper studies the seismic behavior of precast concrete beam-column bolted joint under vertical low cyclic loading. The experimental results show that cracks appear in the beam-column joint core area. Meanwhile, the concrete and the grade 5.6 bolts are damaged and deformed, respectively. Specifically, the overall structure of the beam-column joint remains intact, and the bolts have good energy dissipation capacity. Based on the experimental study, a new method of beam-column bolted connection is proposed in simulation analysis. The simulation results show that the bolts deform in the core area of the new beam-column joint, which enhances the concrete shear capacity legitimately and protects the T-end of the beam against shear failure. To summarize, both the experimental joint and the simulated joint prolong the service life by replacing the bolts under the seismic loading. The research results provide a reference for applications of the fabricated beam-column joint.

Intermediate State and Weak Intermolecular Interactions of α-trans-1,4-Polyisoprene During the Gradual Cooling Crystallization Process Investigated by In situ FTIR and Two-Dimensional Infrared Correlation Spectroscopy

Xiaoan Wang,Kewei Xiang,Yijing Nie,Guangsu Huang,Jinrong Wu,Zhiqing Su 한국고분자학회 2013 Macromolecular Research Vol.21 No.5

The investigation of the gradual cooling crystallization process of α-trans-1,4-polyisoprene (α-TPI) was carried out for different wavenumber regions by conventional spectral analysis and two-dimensional correlation infrared spectroscopy (2DIR) methods. Interestingly, an intermediate state has been confirmed by the fascinating intensity variation of the 1666 cm-1 band, and the motion of side-chain (CH3 group) seems to be the initial driving force and precondition for forming the ordered 21 helix conformation. It is also found that the occurrence for the splitting of the CH3 group-related bands is consistent with the appearance of the intermediate state, indicating that the interchain interactions between CH3 groups play an important role in controlling the intermediate state and should be the primary driving force for stabilizing the specific 21 helix conformation.