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Bai L.,Shanghai JiaoTong University | Bai L.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Bai L.,Imperial College London | Wadee M.A.,Imperial College London
Engineering Structures | Year: 2016

A variational model that describes the nonlinear interaction between the global and local buckling of a thin-walled I-section strut under pure compression is presented and subsequently exploited. A parametric study is conducted for two limiting cases, where the flange-web joint is assumed to be pinned or rigid. For a chosen set of geometries, the most undesirable parametric spaces are identified for both global and local slendernesses, in terms of the strut length and the flange width respectively, where highly unstable behavior is observed in the post-buckling range. Practical implications are discussed in terms of the idealized design strength relationship. © 2016 Elsevier Ltd.

Guan D.,Shanghai JiaoTong University | Liang F.,Shanghai JiaoTong University | Liang F.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration | Gremaud P.A.,North Carolina State University
Journal of Biomechanics | Year: 2016

One-dimensional (1D) modeling is a widely adopted approach for studying wave propagation phenomena in the arterial system. Despite the frequent use of the Windkessel (WK) model to prescribe outflow boundary conditions for 1D arterial tree models, it remains unclear to what extent the inherent limitation of the WK model in describing wave propagation in distal vasculatures affect hemodynamic variables simulated at the arterial level. In the present study, a 1D model of the arterial tree was coupled respectively with a WK boundary model and a structured-tree (ST) boundary model, yielding two types of arterial tree models. The effective resistances, compliances and inductances of the WK and ST boundary models were matched to facilitate quantitative comparisons. Obtained results showed that pressure/flow waves simulated by the two models were comparable in the aorta, whereas, their discrepancies increased towards the periphery. Wave analysis revealed that the differences in reflected waves generated by the boundary models were the major sources of pressure wave discrepancies observed in large arteries. Additional simulations performed under aging conditions demonstrated that arterial stiffening with age enlarged the discrepancies, but with the effects being partly counteracted by physiological aortic dilatation with age. These findings suggest that the method adopted for modeling the outflow boundary conditions has considerable influence on the performance of a 1D arterial tree model, with the extent of influence varying with the properties of the arterial system. © 2016 Elsevier Ltd.

Wang H.,Shanghai JiaoTong University | Qin R.,Shanghai JiaoTong University | He G.,Shanghai JiaoTong University | He G.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2016

The metallurgical behavior during shielded metal arc welding (SMAW) and the slag detachability of the CaO-CaF2-SiO2 type ENiCrFe-7-covered electrodes was investigated. The results indicated that the slag detachability could be improved as the SiO2 in the flux coatings decreased. When the SiO2 in the flux coating was 10.9 pct, about 28.3 pct CaF2 resulted in the best slag detachability. The CaF2 and SiO2 in the flux coating interacted during SMAW to form gaseous SiF4 to be evacuated. In the reactions, one SiO2 consumed two CaF2, leading to the reduction of the ratio of CaF2/SiO2. After comparing the slag compositions, the best slag detachability was obtained at CaO:CaF2:SiO2 = 1.7:1.8:1, but the worst slag detachability appeared at CaO:CaF2:SiO2 = 1.3:0.9:1. The XRD analysis revealed that the oxides and fluorides in the slags preferred to gather together to form cuspidine and other complex phases. If the CaF2 was dominant in the slags, they intended to form homogenous porous microstructures that were relatively strong and would most likely detach from the weld metal in blocks, exhibiting good slag detachability. If the cuspidine phase was dominant, the slags exhibited a ‘rock strata’-like microstructure in the intergranular area. Such microstructure was very fragile and could be broken into fine powders that were easily embedded in the weld ripples, leading to slag adhesions. This work provides the researcher with a wealth of information and data, which will also be beneficial to the welding material producers and users. © 2016, The Minerals, Metals & Materials Society and ASM International.

Wang H.-Z.,Shanghai JiaoTong University | Zou Z.-J.,Shanghai JiaoTong University | Zou Z.-J.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
China Ocean Engineering | Year: 2016

An investigation has been conducted to quantify the effect of waterway geometry on the form and magnitude of forces and moment experienced by a berthed ship due to a passing ship. By using the dynamic mesh technique and solving the unsteady RANS equations in conjunction with a RNG k-ε turbulence model, numerical simulation of the three-dimensional unsteady viscous flow around a passing ship and a berthed ship in different waterway geometries is conducted, and the hydrodynamic forces and moment acting on the berthed ship are calculated. The proposed method is verified by comparing the numerical results with existing empirical curves and a selection of results from model scale experiments. The calculated interaction forces and moment are presented for six different waterway geometries. The magnitude of the peak values and the form of the forces and moment on the berthed ship for different cases are investigated to assess the effect of the waterway geometry. The results of present study can provide certain guidance on safe maneuvering of a ship passing by a berthed ship. © 2016, Chinese Ocean Engineering Society and Springer-Verlag Berlin Heidelberg.

Li Q.,Shanghai JiaoTong University | He G.,Shanghai JiaoTong University | He G.,Collaborative Innovation Center for Advanced Ship and Deep Sea Exploration
Materials and Design | Year: 2016

Porous titanium with entangled wire structure was enhanced by filling gelatin into the porous structure to form a titanium-gelatin (Ti-G) composite. The density of the composites was 1.6-2.5 g/cm3, similar to that of bone. The strength and elastic modulus of the composites reached 12.9-39.4 MPa and 2.5-7.4 GPa, respectively, which were comparable to that of the cortical bone. Gelatin in Ti-G composite acted as the carrier of gentamicin sulphate (GS). Antibacterial efficacy of GS-loaded Ti-G against Staphylococcus aureus strain was tested. The lack of growth of Staphylococcus aureus strains was found in Luria-Bertani (LB) medium containing GS-loaded Ti-G. GS release behavior from the GS-loaded Ti-G composites in phosphate buffer saline (PBS) was investigated. The effective GS release times from Ti30-G and Ti50-G were 120 h and 168 h, respectively. The gelatin in Ti-G was just degraded 3.2% at the immersion time of 168 h and 9.0% at 336 h. The degradation rate of gelatin was much slower than release rate of GS, indicated that the GS release from gelatin was less affected by the gelatin degradation. These Ti-G composites loaded with drug(s) are expected to be good candidates as functional bone repair materials with drug-delivery capabilities. © 2016.Elsevier Ltd. All rights reserved.

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