Research on failure modes and ultimate strength behavior of typical sandwich composite joints for ship structures

Xu Geng,Qin Kai,Yan Renjun,Dong Qin 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1

This paper presents an experimental and numerical investigation on failure behavior and ultimate strength of fiber-reinforced sandwich composite structures. Tests were conducted on the sandwich Ljoints with Glass Fiber-Reinforced Polymer (GFRP) face sheet and Polyvinyl chloride (PVC) foam core. In the numerical simulation, a progressive damage method is established to simulate the strength and failure behavior of sandwich L-joint, different failure criteria are used to deal with the various failure modes of GFRP laminates. Cohesive zone model and viscoelastic material model are combined to model the face-core adhesive interface, hence the influence of fracture and debonding of adhesive to the total strength of sandwich joints is considered by the numerical modelling. On the base of these theories, the finite element model of sandwich L-joint has been successfully established, and the numerical predictions present a good agreement with the test results on both structural strength and failure process.

Effect of Electrolyte Filtration Accuracy on Electrochemical Machining Quality for Titanium Alloy

Zhiliang Xu,Zhengyang Xu,Hongyu Xu,Zhenyu Shen,Tianyu Geng The Korean Electrochemical Society 2024 Journal of electrochemical science and technology Vol.15 No.2

Electrochemical machining (ECM) is an effective manufacturing method for difficult-to-machine materials and is widely used in the precision manufacturing of aerospace components. In recent years, the requirements for the machining accuracy and surface integrity of ECM have become increasingly stringent. To further improve the machining quality, this work investigated the intricate laws between electrolyte filtration accuracy and machining quality. Electrolytes with different filtration accuracies were compared, and a numerical simulation was used to evaluate the change in temperature and bubble rate of the flow field in the machining area. Experiments were conducted on ECM of Ti-6Al-4V (TC4) alloy workpieces using electrolytes with different filtration accuracy. The workpiece machining accuracy and surface quality were analyzed, and the repetition accuracy of the workpiece was evaluated. The intricate laws between electrolyte filtration accuracy and machining quality were explored. It was found that when the electrolyte filtration accuracy is improved, so too is the machining quality of the ECM. However, once the filtration accuracy has reached a certain value, the machining quality has extremely limited improvement. By evaluating the repetition accuracy of processed workpieces in electrolytes with different filtration accuracies, it was found that when the filtration accuracy reaches a certain value, there is no positive correlation between the repetition accuracy and filtration accuracy. The result shows that, for the workpiece material and conditions considered in this paper, an electrolyte with 0.5㎛ filtration accuracy is suitable for the wide application of precision ECM.

Fabrication of Composite Polymer Foam Films at the Liquid/Liquid Interface through Emulsion-Directed Assembly and Adsorption Processes

Geng, Yuanyuan,Liu, Mei,Tong, Kun,Xu, Jian,Lee, Yong-Ill,Hao, Jingcheng,Liu, Hong-Guo American Chemical Society 2014 Langmuir Vol.30 No.8

<P>The foam films of polystyrene-<I>b</I>-poly(acrylic acid)-<I>b</I>-polystyrene (PS-<I>b</I>-PAA-<I>b</I>-PS) doped with Cd(II) or Pb(II) species were fabricated at the planar liquid/liquid interfaces between a DMF/chloroform (v/v: 1/1) solution of the polymer and aqueous solutions containing cadmium acetate or lead acetate at ambient temperature. Optical microscopic observation shows the thin film is uniform on a larger length scale. Transmission electron microscopic (TEM) investigations reveal that the foam films are made up of microcapsules with the size of several hundreds of nanometers to micrometers. The walls of the microcapsules have a layered structure decorating with nanofibers and hollow nanospheres, where numerous inorganic fine nanoparticles are dispersed homogeneously. The film formation is a result of emulsion droplet-templated assembly and adsorption of the formed microcapsules at the planar liquid/liquid interface. Because of the miscibility of DMF with chloroform and water, DMF migrates to the aqueous phase while water migrates to the organic phase across the interface, resulting in the formation of a W/O emulsion, as revealed by optical microscopic observation, freeze fracture transmission electron microscopic (FF-TEM) observation, and dynamic laser scattering (DLS) investigation. The triblock copolymer molecules and the inorganic species adsorb and self-assemble around the emulsion drops, leading to the formation of the composite microcapsules. X-ray photoelectron spectroscopic (XPS) and FTIR spectroscopic results indicate that two kinds of Cd(II) or Pb(II) species, metal oxide or hydroxide, resulting from the hydrolysis of the metal ions and the coordinated metal ions to the carboxyl groups coexist in the formed thin films, which transform to metal sulfide completely after treating with hydrogen sulfide to get metal sulfide nanoparticle-doped polymer thin films.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-8/la500187d/production/images/medium/la-2014-00187d_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la500187d'>ACS Electronic Supporting Info</A></P>

Cloning and Spatiotemporal Expression Analysis of Bombyx mori elav, an Embryonic Lethal Abnormal Visual Gene

Geng Xian Wang,Ying Liu,Yang Hu Sima,Sheng Xiang Zhang,Shi Qing Xu 한국잠사학회 2009 International Journal of Industrial Entomology Vol.18 No.2

Embryonic lethal abnormal visual (elav) is a lethal gene in Drosophila inducing the abnormal development and function of nervous system. We cloned a Bmelav gene by bioinformatics and biological experiment, based on sequence of ELAV protein and dbEST of Bombyx mori. The full-length of Bm-elav cDNA is 1498 bp, contains a 906 bp open read frame (ORF) encoding a precursor of 301 amino acid residues with a calculated molecular weight of 34 kDa and pI of 8.99. Bm-ELAV protein precursor contains three RNA recognition motifs (RRM) in 24~91, 110~177 and 222~295 bit amino acid residues respectively, and belongs to RNA-binding protein family. Bm-ELAV shared varying positives, ranging from 56% to 60% (Identities from 41% to 45%), with RRM from other species of Xenopus tropicalis, Apis mellifera, Tribolium castaneum, Branchiostoma belcheri and Drosophila. Gene localization indicated that Bm-elav is a single-copy gene, gene mapping within 12-chromosome from 7916.68 knt to 7918.16 knt region of nscaf2993. Spatiotemporal expressions pattern analysis revealed that Bm-elav expressed higher in most tested tissues and developmental stages in whole generation, such as silk gland, fat body, midgut, hemopoietic organ and ovary, but almost no expression in terminated diapause eggs. This suggested that the expression of Bm-elav in early developmental embryonic stages might induce abnormal development like in Drosophila. Cloning of the Bmelav gene enables us to test its potential role in controlling pests by transferring the gene into field lepidopteran insects in the future.

A New Method for Elimination of Zero-Sequence Voltage in Dual Three-Level Inverter Fed Open-End Winding Induction Motors

Geng, Yi-Wen,Wei, Chen-Xi,Chen, Rui-Cheng,Wang, Liang,Xu, Jia-Bin,Hao, Shuang-Cheng The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

Due to the excessive zero-sequence voltage in dual three-level inverter fed open-end winding induction motor systems, zero-sequence circumfluence which is harmful to switching devices and insulation is then formed when operating in a single DC voltage source supplying mode. Traditionally, it is the mean value instead of instantaneous value of the zero-sequence voltage that is eliminated, through adjusting the durations of the operating vectors. A new strategy is proposed for zero-sequence voltage elimination, which utilizes unified voltage modulation and a decoupled SVPWM strategy to achieve two same-sized equivalent vectors for an angle of $120^{\circ}$, generated by two inverters independently. Both simulation and experimental results have verified its efficiency in the instantaneous value elimination of zero-sequence voltage.

Lightweight and Ultrastrong Polymer Foams with Unusually Superior Flame Retardancy

Xu, Linli,Xiao, Linhong,Jia, Pan,Goossens, Karel,Liu, Peng,Li, Hui,Cheng, Chungui,Huang, Yong,Bielawski, Christopher W.,Geng, Jianxin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.31

<P>High-performance flame-retardant materials are urgently needed to address outstanding issues that pertain to safety. Traditional flame retardants are toxic to the environment and/or lack the physical properties required for use in many contemporary applications. Here, we show that isocyanate-based polyimide (PI) foam, a flammable material, can exhibit unusually superior flame retardancy as well as, other excellent properties, such as being lightweight and displaying high mechanical strength, by incorporating red phosphorus (RP)-hybridized graphene. The covalent bonds formed between the graphene platelets and the PI matrix provide the resultant PI foam with a specific Young's modulus (83 kNm kg(-1)) that is comparable to or even higher than those displayed by state-of-the-art foams, including silica aerogels, polystyrene foams, and polyurethane foams. In addition, even a low content of the RP -hybridized graphene (2.2 wt %) results in an exceptionally higher limiting oxygen index (39.4) than those of traditional flame-retardant polymer-based materials (typically 20-30). The resultant PI foam also exhibits thermal insulation properties that are similar to that of air. Moreover, the RP -hybridized graphene is prepared using a one-step ball milling process in 100% yield, and does not require solvent or produce waste. The preparation of the flame-retardant PI foams can be scaled as the starting materials are commercially available and the techniques employed are industrially compatible.</P>

Driver Preview Model with Dual Far-near Points for Autonomous Vehicles

Rongrong Xu,Zezheng Huang,Weihua Li,Jianfeng Wang,Dianbo Ren,Xuewen Geng 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.11

This paper proposes a driver preview-based path-following controller to control both the lateral and longitudinal movements of a vehicle. First, a lateral tracking controller with two preview points is established by considering the displacement and heading errors of the two preview points: the far point, determined by the vehicle speed and fixed preview time, and the near point located at the center of the front axle. Depending on different parameters of the road input, the steering wheel angle is calculated, and different weights are assigned to the steering wheel angles corresponding to different road inputs. Next, a longitudinal tracking controller is established, which controls the vehicle velocity based on the road information of the far point. The control objects are the brake and accelerator pedals. Subsequently, the coupling of the lateral and longitudinal motion of the vehicle is analyzed, and an integrated longitudinal and lateral tracking controller is established. To verify the performance of the controller, the controller and vehicle model are established in Simulink and CarSim, respectively, to enable joint simulation. It is observed that the coupling is solved, and the near-point control makes the tracking error converge to zero and enhances the control effect. It demonstrates high adaptability and control accuracy of the proposed controller.

A Weighted Nuclear Norm Method for Tensor Completion

Juan Geng,Laisheng Wang,Yitian Xu,Xiuyu Wang 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.1

Fabrication and Soft Magnetic Properties of Fe–B–Si–Zr/Hf–Cu Nanocrystalline Alloys with High Glass-Forming Ability

Yaoxiang Geng,Yingmin Wang,Yuxin Wang,Zhijie Zhang,Hongbo Ju,Lihua Yu,Junhua Xu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11

The effects of minor alloying addition of Cu on the glass-forming ability and crystallization process of Fe71.7−xB16.7Si8.3Zr3.3Cuxand Fe72.5−xB16.7Si8.3Hf2.5Cux (x = 0, 0.3, 0.7, 1.0 and 1.3; at%) alloys were investigated. It was found that the critical glassformation size of rod samples gradually decreased from 2.5 to 1 mm with increasing Cu content in these alloys. Single α-Fe phase nanocrystalline alloys were obtained after isothermal annealing the Fe–B–Si–Zr/Hf–Cu glassy alloys containing0.7–1.0 at% Cu. The Fe71B16.7Si8.3Zr3.3Cu0.7alloy exhibited good soft magnetic properties with a high saturation magnetization(~ 1.22 T) and a low coercive force (~ 0.6 A/m) after annealing at 853 K for 10 min due to the precipitation of α-Fenanoparticles of 8 nm size in the glassy matrix. The structural evolution on annealing and the variation tendencies against Cucontent of the glass transition temperature, thermal stability and glass-forming ability of the Fe–B–Si–Zr/Hf–Cu amorphousalloys were discussed using a dual-cluster local structure model.

Autophagy of bovine mammary epithelial cell induced by intracellular Staphylococcus aureus

Na Geng,Kangping Liu,Jianwei Lu,Yuliang Xu,Xiaozhou Wang,Run Wang,Jianzhu Liu,Yongxia Liu,Bo Han 한국미생물학회 2020 The journal of microbiology Vol.58 No.4

Bovine mastitis is a common disease in the dairy industry that causes great economic losses. As the primary pathogen of contagious mastitis, Staphylococcus aureus (S. aureus) can invade bovine mammary epithelial cells, thus evading immune defenses and resulting in persistent infection. Recently, autophagy has been considered an important mechanism for host cells to clear intracellular pathogens. In the current study, autophagy caused by S. aureus was detected, and the correlation between autophagy and intracellular S. aureus survival was assessed. First, a model of intracellular S. aureus infection was established. Then, the autophagy of MAC-T cells was evaluated by confocal microscopy and western blot. Moreover, the activation of the PI3K-Akt-mTOR and ERK1/2 signaling pathways was determined by western blot. Finally, the relationship between intracellular bacteria and autophagy was analyzed by using autophagy regulators (3-methyladenine [3-MA], rapamycin [Rapa] and chloroquine [CQ]). The results showed that S. aureus caused obvious induction of autophagosome formation, transformation of LC3I/II, and degradation of p62/SQSTM1 in MAC-T cells; furthermore, the PI3K-Akt-mTOR and ERK1/2 signaling pathways were activated. The number of intracellular S. aureus increased significantly with autophagy activation by rapamycin, whereas the number decreased when the autophagy flux was inhibited by chloroquine. Therefore, this study indicated that intracellular S. aureus can induce autophagy and utilize it to survive in bovine mammary epithelial cells.