Research on the Microstructure Characteristic and Tensile Property of Laser‑MIG Hybrid Welded Joint for 5A06 Aluminum Alloy

Yanqiu Zhao,Xiaohong Zhan,Qiyu Gao,Shuai Chen,Yue Kang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.3

Laser-metal inter gas (MIG) hybrid welding technique provides higher overall productivity over the traditional fusionwelding processes for joining medium-thick aluminum alloy. In this paper, laser-MIG hybrid welding experiment was performedby the TruDisk 12003 Laser and KUKA robot. The second fusion line, the laser-dominated region and laser-MIGhybrid-dominated region were introduced to this study to discuss the microstructure distribution. A three-dimensionalfinite element model was established by MSC. Marc to study the thermal field distribution of laser-MIG hybrid weldingprocess. It found that the temperature in the laser-MIG hybrid-dominated region was much higher than the laser-dominatedregion. The formation of the second fusion line in the welded joint is mainly owing to the different heat effect of laser-archybrid-dominated region and laser-dominated region. The crystalline size of equiaxed dendrite grains in the laser-MIGhybrid-dominated region is finer than the laser-dominated region. In addition, the tensile property was measured to dissectthe failure mechanism of the laser-MIG hybrid welding joints. The element content in fractured surface at the position ofdimple and pore wall were comprehensively analyzed. The element content of Mg and O in pore wall are higher than dimple. In the solidification process, the growth of equiaxed dendrite grains is in part hindered by the existence of coarse pores inthe laser-MIG hybrid-dominated region.

The Current Situation of Internet Addiction and Its Impact on Sleep Quality and Self-Injury Behavior in Chinese Medical Students

Yanqiu Wang,Ying Zhao,Ling Liu,Yan Chen,Dong Ai,Yingshui Yao,Yuelong Jin 대한신경정신의학회 2020 PSYCHIATRY INVESTIGATION Vol.17 No.3

Objective The purpose of this cross-sectional survey is to explore the current state of Internet addiction (IA) in Chinese medical students and its connection with medical students’ sleep quality and self-injury behavior. Methods Respondents were came from Wannan Medical College, China. The Young’s Internet Addiction Test, Pittsburgh Sleep Quality Index (PSQI), Self-Harm Questionnaire were used in this cross-sectional survey. A total of 3,738 medical students were investigated, 1,552 (41.52%) males, 2,186 (58.48%) females. T-test, chi-square test and MANOVA were used for data analysis. Results Of the 3,738 medical students, 1,054 (28.2%) reported having IA, 1,126 (30.1%) reported having poor sleep quality, 563 (15.1%) having self-harm behaviors. IA tends to be more female, upper grade students. The sleep quality of IA was worse than that of non-IA (χ2=54.882, p<0.001), and the possibility of self-injury was higher than non-IA (χ2=107.990, p<0.001). Conclusion This survey shows that the IA detection rate of medical students was 28.2%. Females, higher grade students had a higher IA detection rate. The low sleep quality and self-injury behavior of medical students are associated with IA.

Influence of heat treatment on complex-shape rotating disk subjected to isothermal precision forging

Yanqiu Zhang,Shuyong Jiang,Xiaoming Zhu,Yanan Zhao,Debin Shan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1

Influence of heat treatment on the mechanical properties of the forging was systematically investigated according to tensile test, hardness test and electrical conductivity test. Simultaneously, typical microstructures of the 7A09 aluminum alloy samples subjected to various solution temperatures and aging regimes were characterized by means of Transmission electron microscope (TEM) and Scanning electron microscope (SEM). In the case of the different solution temperatures, the size of precipitations increases with the increase in the solution temperature, which contributes to improving both strength and stress corrosion resistance of the forging. The solution temperature of 465 °C leads to the well comprehensive mechanical properties and the superior stress corrosion resistance of the forging. G.P. zone, η' phase and η phase are able to precipitate in the matrix of the forging in the case of different aging regimes, such as peak aging, two-stage overaging, two-stage aging, and regression and re-aging. The precipitation phases play an important role in enhancing the mechanical properties of the forging as an obstacle against the dislocation movement.

Strain-Rate Effect on the Stress and Strain Concentration in a Visco-Plastic Plate With An Elliptic Hole

Yanqiu Chen,Jin Zhang,Peishi Yu,Jian Wu,Weibo Wang,Junhua Zhao 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4

The stress and strain concentration in some component has been a signifi cant topic for structural safety assessment. However, the evaluation of the stress and strain concentration based on the widely existing solutions for linear elastic material under static loading would lead to remarkable errors when the material undergoes the dynamic loading, since the coupling eff ect induced by the nonlinearity of the stress–strain relationship and the strain-rate strengthening could be of signifi cant infl uence. Here we analyzed the strain-rate dependent concentration of stress and strain for a visco-plastic plate with an elliptic hole subjected to dynamic loading. The three-dimensional stress and strain are calculated by fi nite element analyses based on a rate-dependent Johnson–Cook model in which the material constants are set according to a typical visco-plastic standard 45 carbon steel. Our results show that both the plastic stress and strain concentration factors signifi cantly depend on not only the strain but also the strain rate. With the increment of the remote strain rate, the stress concentration monotonically increases, while the strain concentration shows decreasing tendency.

Trajectory Tracking Control of Intelligent Vehicles

Cui Guangzhen,Zhao Di,Xiao Yanqiu,Fang Zhanpeng,Yao Lei 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1

In this paper a combined lateral and longitudinal control algorithm based on model predictive control is proposed. In the lateral controllers, feedforward control based on model prediction and feedback of heading error and yaw angle error are used to improve the tracking accuracy of the front wheels. According to the anti-interference ability of the active disturbance rejection controller, the yaw rate is taken as the input to compensate the front wheel angle of the vehicle, improving the tracking stability of the vehicle. In the design process of the longitudinal control system, we use a hierarchical controller. The upper controller is a model predictive controller with a constraint function, that obtains the desired acceleration based on the reference speed. The lower controller is an inverse longitudinal dynamics model, which obtains the fnal control amount of the vehicle based on the output of the upper controller. This proposed method was validated on the co-simulation platform constructed by CarSim and MATLAB/Simulink. The experimental and simulation results demonstrate the efectiveness and superiority of the improved model predictive controller in tracking accuracy and steering smoothness.

Refolding Behavior of Urea-Induced Denaturation Collagen

Xu Wei,Yanqiu Zhao,Jingjing Zheng,Qin Cao,Sheng Li,Lang He,Benmei Wei,Juntao Zhang,Chengzhi Xu,Haibo Wang 한국고분자학회 2021 Macromolecular Research Vol.29 No.6

Exploration of the denaturation and refolding of natural collagen is important for the application of collagen and its denatured products. In this study, using urea as a denaturant, we prepared a denatured natural collagen product and analyzed its structural changes. The denaturation treatment severely destroyed the triple helix conformation of collagen, but had no significant effect on the primary structure of its α chains or the covalent cross-linking between α chains. Next, we observed the refolding behavior of the denatured collagen by removing urea through dialysis. We found that the denatured collagen products from different sources (grass carp skin, bovine tendon) all showed a reconstruction of the triple helix conformation up to 60-75% of the value of natural collagen during the refolding process. The telopeptide did not significantly promote triple helix reconstruction. In conclusion, the reconstruction of the α chains did not perfectly occur in a “head-to-head, tail-to-tail” manner in refolded collagen, as each α chain was participating in the reconstruction of multiple triple helix domains. The refolded collagen still had weak self-assembly ability and formed a unique network-like structure containing small interlaced and closely combined fibers, which shows favorable cell compatibility and potential applications.

Influence of Laser Power on Grain Size and Tensile Strength of 5A90 Al–Li Alloy T-joint Fabricated by Dual Laser-Beam Bilateral Synchronous Welding

Shuai Chen,Xiaohong Zhan,Yanqiu Zhao,Youfa Wu,Dongtao Liu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6

Dual laser-beam bilateral synchronous welding is introduced to produce the 2.5 mm thick 5A90 Al–Li alloy T-joint. Thegrain morphology and grain size of weld metal (WM) in the T-joint are analyzed and calculated. The tensile experiment,scanning electron microscopy and energy disperse spectroscopy are respectively employed to study the tensile strength,fracture morphology and chemical composition of the T-joint. The results reveal that when the laser power is increased from2500 to 3000 W, the grain sizes of fine-grained layers and columnar dendrites near the fusion line are significantly reduced. Conversely, that of equiaxed dendrites at the WM center is not sensitive to the variety of laser power. Moreover, the degreeof elemental segregation in WM near the fusion line is also aggravated with the increasing of the laser power. The tensilestrength of the T-joint with the laser power of 2500 W is significantly higher than that with the laser power of 3000 W. Thetensile fracture locations are occurred in the weld toe with obvious pores, shear dimples and tear ridges, which are the typicalcharacteristics of ductile fracture. Besides, the chemical compositions of the second phase particles in the WM are moresensitive to than the variation of laser power compared with that of the matrix.

Fatty Acid-Binding Protein 4 in Patients with and without Diabetic Retinopathy

Ping Huang,Xiaoqin Zhao,Yi Sun,Xinlei Wang,Rong Ouyang,Yanqiu Jiang,Xiaoquan Zhang,Renyue Hu,Zhuqi Tang,Yunjuan Gu 대한당뇨병학회 2022 Diabetes and Metabolism Journal Vol.46 No.4

Background: Fatty acid-binding protein 4 (FABP4) has been demonstrated to be a predictor of early diabetic nephropathy. However, little is known about the relationship between FABP4 and diabetic retinopathy (DR). This study explored the value of FABP4 as a biomarker of DR in patients with type 2 diabetes mellitus (T2DM).Methods: A total of 238 subjects were enrolled, including 20 healthy controls and 218 T2DM patients. Serum FABP4 levels were measured using a sandwich enzyme-linked immunosorbent assay. The grade of DR was determined using fundus fluorescence angiography. Based on the international classification of DR, all T2DM patients were classified into the following three subgroups: non-DR group, non-proliferative diabetic retinopathy (NPDR) group, and proliferative diabetic retinopathy (PDR) group. Multivariate logistic regression analyses were employed to assess the correlation between FABP4 levels and DR severity.Results: FABP4 correlated positively with DR severity (<i>r</i>=0.225, <i>P</i>=0.001). Receiver operating characteristic curve analysis was used to assess the diagnostic potential of FABP4 in identifying DR, with an area under the curve of 0.624 (37% sensitivity, 83.6% specificity) and an optimum cut-off value of 76.4 μg/L. Multivariate logistic regression model including FABP4 as a categorized binary variable using the cut-off value of 76.4 μg/L showed that the concentration of FABP4 above the cut-off value increased the risk of NPDR (odds ratio [OR], 3.231; 95% confidence interval [CI], 1.574 to 6.632; <i>P</i>=0.001) and PDR (OR, 3.689; 95% CI, 1.306 to 10.424; <i>P</i>=0.014).Conclusion: FABP4 may be used as a serum biomarker for the diagnosis of DR.

Microstructure, Thermal Behavior and Tensile Properties of Laser Welded Bottom-Locking Joint for TA15 Titanium Alloy

Jiayao Wang,Jianfeng Wang,Yanqiu Zhao,Yue Li,Xiaohong Zhan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5

The present investigation aims at the thermal conditions for the TA15 titanium alloy laser welded bottom-locking joint. Bottom-locking featured specimens under three welding speeds were manufactured to study the grain morphology and tensileproperties. Finite element computation based on temperature field simulation was conducted in order to shed more light on themicrostructure characteristics of the bottom-locking joint. The results indicate a significant influence of the welding speed onthe thermal cycle, microstructure evolution and tensile performance. As the welding speed increases, the width of weld zone(WZ) is decreased significantly. At the same time, the columnar crystal features a coarser shape and its growth cross regionat the bottom of WZ becomes smaller with the increasing welding speed. Besides, the size of martensite decreases with theincreasing of welding speed. With the support of both numerical and experimental results, complex microstructure evolutionmechanisms were revealed involving thermal cycle related to the welding speed. In addition, the laser welded bottom-lockingjoint of TA15 titanium alloy is even fractured at the base metal, which exhibits the comparable tensile properties. The EDSresults illustrate the inevitable burning losses of stabilization element during the welding process. All these mechanisms areassociated with the bottom-locking joint arrangement and the welding speed-induced thermal cycle.