Thermal buckling optimisation of composite plates using firefly algorithm

Abstract

Composite plates play a very important role in engineering applications, especially in aerospace industry. Thermal buckling of such components is of great importance and must be known to achieve an appropriate design. This paper deals with stacking sequence optimisation of laminated composite plates for maximising the critical buckling temperature using a powerful meta-heuristic algorithm called firefly algorithm (FA) which is based on the flashing behaviour of fireflies. The main objective of present work was to show the ability of FA in optimisation of composite structures. The performance of FA is compared with the results reported in the previous published works using other algorithms which shows the efficiency of FA in stacking sequence optimisation of laminated composite structures.     

Design and Structural Analysis of Support Structure for ITER Vacuum Vessel

The International Thermonuclear Experimental Reactor (ITER) vacuum vessel (VV) is a safety component confining radioactive materials such as tritium and activated dust. An independent VV support structure with multiple flexible plates located at the bottom of VV lower port is proposed as a new concept, which is deferent from the current design, i.e., the VV support is directly connected to the toroidal coils (TF coils). This independent concept has two advantages comparing to the current one: (1) thermal load due to the temperature deference between VV and TF coils becomes lower and (2) the TF coils are categorized as non-safety components because of its independence from VV. Stress Analyses have been performed to assess the integrity of the VV support structure using a precisely modeled VV structure. As a result, (1) the maximum displacement of the VV corresponding to the relative displacement between VV and TF coils is found to be 15 mm, much less than the current design clearance of 100 mm, and (2) the stresses of the whole VV system including VV support are estimated to be less than the allowable ones defined by ASME Section III Subsection NF, respectively. Based on these assessments, the feasibility of the proposed independent VV support has been verified as a VV support.     

Flow and heat transfer of a Giesekus fluid in plane and 3D ducts

This study aims to investigate the Graetz problem of Newtonian and viscoelastic fluid obeying Giesekus model using ANSYS Polyflow solver. The non‐isothermal flow in straight ducts of circular and noncircular cross‐sections under the constant heat flux boundary conditions is considered. The effect of the mobility parameter (α), fluid elasticity defined by Weissenberg number (We) and Reynolds number (Re) on the flow field, secondary flows, and the fully developed and developing Nusselt number along the ducts length are investigated for all geometries. The obtained results are of great importance for practical application in the polymer industries such as polymer melt.     

Modulated gravity effects on nonlinear convection in viscoelastic ferromagnetic fluids between two horizontal parallel plates

In this study, the analysis of nonlinear stability with viscoelastic ferromagnetic fluids as working media is performed by finite-amplitude perturbations. The solution of the resulting nonautonomous system of the Lorenz model (generalized Khayat–Lorenz model of four modes) is obtained numerically to measure the amount of heat transport. The effects of elastic parameters, Prandtl number, modulation parameters, buoyancy magnetic parameter, and nonbuoyancy magnetic parameter on heat transport are studied. Heat transport is quantified through the average Nusselt number, which is determined by solving the scaled Lorenz model. As limiting cases of the study, the results of Newtonian, Maxwell, Rivlin–Ericksen fluids are determined. The results obtained have been presented graphically.     

Design Impact on Airflow Patterns in Fluidization Units

The airflow behavior in a fluidization unit was integrally studied by means of experimental work and computational fluid dynamics simulation. The computational domain included the gas inlet pipe, plenum, perforated plate, fluidization chamber, and air outlet pipe. Different scenarios were simulated to allow distinguishing the best way to represent perforated‐plate distributors and elucidate the impact of the grid design on the fluidization performance. The simulated pressure drop across the distributor and the plenum flow pattern were in concordance with the experimental data. It was found that the distance between the peripheral holes and walls has a great impact on the airflow downstream the distributor.     

The effect of Cr doped in amorphous carbon films on electrical conductivity: Characterization and mechanism

Metallic bipolar plates (BPPs) are prospective candidates for BPPs in PEMFCs due to their lower cost and higher power density than traditional graphite. Coatings are used to enhance the electrical conductivity and anti-corrsive quality of BPPs, and amorphous carbon (a-C) films have attracted broad attentions from both industry and academia. In this study chromium was incorporated into a-C to further enhance conductivity. A series of Cr-doped a-C films (a-C:Cr) with different doping contents were prepared by CFUBMSIP. Moreover, Microstructure analyses and composition characterizations were performed to explore the mechanism. The results show that Cr decreases the interfacial resistance with satisfying the anti-corrosive behavior. XRD patterns indicate that Cr will form chromium carbide phase and pure metal phase. Moreover, TEM results also show that Cr atoms bond with C atoms. SEM photographs show that Cr atoms refine the grain size and compact the film all the same. C 1s spectrum of XPS shows that C-sp²/C-sp³ increases first and then decreases, reaching the maximum level of 1.708 at Cr_0.205, indicating the resistance drops first and then increases. In addition, Cr doping will also bring changes in nano-hardness and surface roughness.     

Ballistic resistance of spaced multi-layer plate structures: Experiments on Fibre Reinforced Plastic targets and an analytical framework for calculating the ballistic limit

As the use of complex multi-layer structures in defense, marine, aerospace and automotive applications becomes increasingly common, it is vital that the response of such structures to impact loading is better understood and that engineers have adequate analysis tools to design structures optimised for resistance to ballistic penetration. This paper presents the results of a series of ballistic impact experiments carried out on a range of spaced multi-layer fibre reinforced-plastic (FRP) composite targets, with a constant total number of plies per target, but varying numbers of plies per layer and varying layer arrangements. It is shown that varying the ratio of plies between layers can have a significant effect on resistance to ballistic penetration. In light of these experimental results, the validity of applying the Lambert–Jonas equation to spaced multi-layer structures is discussed and an extended framework developed to determine the ballistic limit of a projectile impacting such a structure. The extended Lambert–Jonas framework is then validated with data from the literature. It is hoped that this framework will allow engineers to quickly determine the optimum layer arrangement to maximise the ballistic resistance of complex spaced multi-layer structures.     

High performance polymeric bipolar plate based on polypropylene/graphite/graphene/nano-carbon black composites for PEM fuel cells

In the present study, the effect of the addition of electrically conductive additives such as graphite, graphene, and high structure nano-carbon black on the manufacturing of polypropylene bipolar plates was studied. Furthermore, for achieving better dispersion of graphene in the matrix, maleic anhydride grafted polypropylene, as a compatibilizer, was utilized. An internal mixing device was used in order to mix additives with polypropylene matrix. Additionally, molding procedure was performed via the compression molding method. In-plane electrical conductivity as well as the flexural strength of various compositions were studied. The best composition of such composites possessed the electrical conductivity of 104.63 S/cm and flexural strength of 44.28 MPa. These values are higher than those designated by the United States Department of Energy for construction of bipolar plates.     

燃料电池不锈钢双极板CrN/CrC薄膜表面改性研究

采用离子镀技术在质子交换膜燃料电池不锈钢双极板表面制备了CrN/CrC多层薄膜。测试结果表明,与未镀膜的不锈钢基体相比,镀膜不锈钢的接触电阻(120N/cm2压紧力)降低2个数量级,并且耐蚀性能显著改善,腐蚀电流密度降低0.5~1个数量级。同时,镀膜不锈钢的耐久性亦大幅提升,改性薄膜可以有效保护不锈钢基体免受腐蚀损害。