Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects

A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression strain capacity may be exceeded.Research into the local buckling failure and accurate prediction of the compressive strain capacity are important.A finite element model of a pipeline with a dent is established.Local buckling failure under a bending moment is investigated,and the compressive strain capacity is calculated.The effects of different parameters on pipeline local buckling are analyzed.The results show that the dent depth,external pressure and internal pressure lead to different local buckling failure modes of the pipeline.A higher internal pressure indicates a larger compressive strain capacity,and the opposite is true for external pressure.When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1,the deeper the dent,the greater the compressive strain capacity of the pipeline.And as the ratio is less than 0.1,the opposite is true.On the basis of these results,a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed,which can be referred to during the integrity assessment of a submarine pipeline.

CFD simulation of hydrodynamics and mixing performance in dual shaft eccentric mixers

This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric mixer.Fluid rheology was described by the power law rheological model.Computational fluid dynamics was employed to simulate the velocity field and shear rate inside the stirred tank.The influence mechanism of the rotational modes,height difference between impellers,impeller eccentricities,and impeller types on the flow field have been well investigated.We studied the performance of different dual-shaft eccentric mixers at the constant power input with its fluid velocity profiles,average shear strain rate,mixing time and mixing energy.The counter-rotation mode shows better mixing performance than co-rotation mode,and greater eccentricity can shorten mixing time on the basis of same stirred condition.To intensify the hydrodynamic interaction between impellers and enhance the overall mixing performance of the dual shaft eccentric mixers,it is critical to have a reasonable combination of impellers and an appropriate spatial position of impellers.

Microstructure and mechanical properties of TC4 titanium alloy K-TIG welded joints

The 12 mm-thick Ti−6Al−4V(TC4)titanium alloy plates were welded using keyhole tungsten inert gas(K-TIG)welding at various heat inputs.The microstructure,grain boundary(GB)characteristics and mechanical properties of the weld metal zone(WMZ)were analyzed.The test results show that the K-TIG welds are well formed,and no obvious defects are observed when the heat input is 2.30−2.62 kJ/mm.When the heat input gradually increases,αlaths increase in length,andα′phase and residualβphase are reduced.The electron backscatter diffraction(EBSD)test results indicate that the high-angle GB proportion in the WMZ increases with the increase of heat input.The tensile strength of the WMZ gradually decreases and the elongation of the WMZ increases when the heat input increases from 2.30 to 2.62 kJ/mm.The impact toughness of the WMZ increases as the heat input increases.

The Nest of Torquigener Albomaculosus:Fluid-Dynamic Aspects and Potential for Bio-Inspired Engineering

Torquigener albomaculosus,also known as the white-spotted pufferfish,is known for creating circular nests in the underwater sand as part of the mating ritual.The nests are built by the males to attract females through the nest’s impressive design and related ability to gather fine sand particles.As the fluid-dynamic processes associated with these unique nests are still almost completely unknown,in the present study,an analysis has been conducted to investigate how the geometric parameters related to the nest design influence the fluid velocity in its center.For this reason,a geometric model of the nest consisting of 24 channels,where each unit channel can be described by three strips of broken lines,has been introduced,and a multivariate analysis has been implemented to determine the relative weight of each considered parameter.In particular,the“optimal”combination of parameters has been obtained by means of an orthogonal design approach.We show that these bio-nest structures also display a potential for significant application in marine litter collection,or for use as a buffer against the waves in offshore areas.

Heterogeneous Task Allocation Model and Algorithm for Intelligent Connected Vehicles

With the development of vehicles towards intelligence and connectivity,vehicular data is diversifying and growing dramatically.A task allocation model and algorithm for heterogeneous Intelligent Connected Vehicle(ICV)applications are proposed for the dispersed computing network composed of heterogeneous task vehicles and Network Computing Points(NCPs).Considering the amount of task data and the idle resources of NCPs,a computing resource scheduling model for NCPs is established.Taking the heterogeneous task execution delay threshold as a constraint,the optimization problem is described as the problem of maximizing the utilization of computing resources by NCPs.The proposed problem is proven to be NP-hard by using the method of reduction to a 0-1 knapsack problem.A many-to-many matching algorithm based on resource preferences is proposed.The algorithm first establishes the mutual preference lists based on the adaptability of the task requirements and the resources provided by NCPs.This enables the filtering out of un-schedulable NCPs in the initial stage of matching,reducing the solution space dimension.To solve the matching problem between ICVs and NCPs,a new manyto-many matching algorithm is proposed to obtain a unique and stable optimal matching result.The simulation results demonstrate that the proposed scheme can improve the resource utilization of NCPs by an average of 9.6%compared to the reference scheme,and the total performance can be improved by up to 15.9%.

Study of Iron Ore Processing Technology of Tamir Gol Deposit in Mongolia

Iron ore processing for steel production is crucial to the development and economy of Mongolia. Regardless of having abundant natural resources and raw materials, Mongolia almost doesn’t produce final products. So far, most mining and mineral beneficiation plants export raw materials only subjected to beneficiation process. Out of more than 200 deposits in Mongolia, 91 deposits had been explored with different methods and stages, and estimated the resource of 33 reserves. Without processing the iron ore, it is impossible to use it for steelmaking due to its high sulfur and phosphorus impurities. Therefore, to study the processing of iron ore deposits in Mongolia, we did a preliminary investigation of iron ore deposits and took samples from the Tamir Gol deposit with high silica and phosphorus content that is difficult to process. Then, conducted mineral analysis and determined the grain structure and beneficiation characteristics of Tamir Gol iron deposit. .

Interactive effects of porosity and microstructure on strength of 6063 aluminum alloy CMT MIX + Synchropulse welded joint

The porosity, pore size and softening of 6063 aluminum alloy CMT MIX + Synchropulse welded joint with different welding speeds were studied. The results show that with the increase of welding speed(from 55 to 65 cm/min), the porosity increases dramatically(from 0.1% to 3.9%) and large pores(341.1 μm) appear. The pore size distributions are mainly concentrated at 87.8 and 20.6 μm in the joints produced from weld speeds of 65 and 55 cm/min, respectively. The dissolution and transformation of the β′′ phase in the base metal(BM) result in a significant softening of both the fusion zone and heat-affected zone, and the latter was more serious. The effects of welding speed on the average tensile strength of the full penetration welded joints are minor, which was about 155 MPa(67.4% that of the BM).

Risk and Reliability Analysis of Deepwater Reel-Lay Installation: A Scenario Study of Pipeline during the Process of Tensioning

In terms of reel-lay installation in deep water, studies on the pipeline during the process of tensioning have been completed based on theories of risk and reliability analysis and Ergonomics. Qualitative risk results, including minimum cut sets, structural importance and probability expression of system failure, are obtained from fault tree analysis. Also, quantitative risk results, mainly consisting of failure probability and reliability index of pipeline plastic deformation, are worked out through Monte Carlo simulation. Simultaneously, scientific suggestions based on Ergonomics are provided. Conclusions drawn from this paper can, to some extent, provide certain references for reel-lay installation in deep water.

Two-Dimensional Metal-Halide Perovskite-based Optoelectronics: Synthesis, Structure, Properties and Applications

In the past decade, metal-halide perovskites have attracted increasing attention in optoelectronics, due to their superior optoelectronic properties.However, inherent instabilities of conventional three-dimensional(3D)perovskites over moisture, heat, and light remain a severe challenge before the realization of commercial application of metal-halide perovskites.Interestingly, when the dimensions of metal-halide perovskites are reduced to two dimensions(2D), many of the novel properties will arise, such as enlarged bandgap, high photoluminescence quantum yield, and large exciton binding energy. As a result, 2D metal-halide perovskite-based optoelectronic devices display excellent performance, particularly as ambient stable solar cells with excellent power conversion efficiency(PCE), high-performance light-emitting diodes(LEDs) with sharp emission peak, and high-sensitive photodetectors. In this review, we first introduce the synthesis, structure,and physical properties of 2D perovskites. Then, the 2D perovskite-based solar cells, LEDs, and photodetectors are discussed. Finally, a brief overview of the opportunities and challenges for 2D perovskite optoelectronics is presented.

Flapwise Bending Vibration Analysis of Rotating Tapered Rayleigh Beams for the Application of Offshore Wind Turbine Blades

The flapwise bending vibrational equations of tapered Rayleigh beam are derived based on Hamilton’s principle.The corresponding vibrational characteristics of rotating tapered Rayleigh beams are investigated via variational iteration method(VIM).Natural frequencies and corresponding mode shapes are examined under various rotation speed,taper ratio and slenderness ratio focusing on two types of tapered beam.The convergence of VIM is examined as part of the paper.Validation of VIM solution is made by referring to results available in other literature and corresponding results show that VIM is capable of yielding precise results in a very efficient way.

Numerical Investigation on Vibration Performance of Flexible Plates Actuated by Pneumatic Artificial Muscle

This paper theoretically introduced the feasibility of changing the vibration characteristics offlexible plates by using bio-inspired,extremely light,and powerful Pneumatic Artificial Muscle(PAM)actuators.Many structural plates or shells are typicallyflexible and show highvibration sensitivity.For this reason,this paper provides a way toachieve active vibrationcontrolfor suppressing the oscillations ofthese structuresto meet strict stability,safety,and comfort requirements.The dynamic behaviors of the designed plates are modeled by using thefinite element(FE)method.As is known,the output force vs.contraction curve of PAM is nonlinear generally.In this presentfinite element model,the maximum forces provided by PAM in different air pressure are adopted as controlling forces for applying for the plate.The non-linearity between the output force and displacement of PAM is avoided in this study.The dynamic behaviors of plates with several independent groups of controlling forces are observed and studied.The results show that the natural frequencies of the plate can be varying and the max amplitude decreases significantly if the controlling forces are applied.The present work also demonstrates the potential of the PAM actuators as valid means for damping out the vibration offlexible systems.

BOP shear force evaluation under complex scenarios

As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.

Microstructure and mechanical properties of friction-stir-welded high-Mg-alloyed Al-Mg alloy plates at different rotating rates

Hot-rolled high-Mg-alloyed Al-Mg alloy(Al-9.2 Mg-0.8 Mn-0.2 Zr-0.15 Ti,labeled as 5 A12)plates were successfully friction stir welded at rotating rates ranging from 750 to 1500 r·min^(-1) at a constant welding speed of50 mm·min^(-1).The joints were characterized by optical microscopy(OM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),electron-dispersive spectroscopy(EDS),and tensile testing.All the joints are volume defectfree and exhibit fine,equiaxed dynamic recrystallization(DRX)grains with high-angle grain boundaries(HAGBs)fractions of 88.6%-93.3%in the nugget zones(NZs).The DRX grain size and the second-phase particle size in the NZs have a parabolic relation with the rotating rate.Furthermore,among the joints tested,the joint prepared at1000 r·min^(-1),which has the highest ultimate tensile strength((478±3)MPa)and the largest elongation to rupture(22.5%±1.4%)—approximately 87.5%and145.2%those of the base metal,respectively,exhibits the smallest grain size of 2.93μm,as well as the smallest particle size in the NZs.These excellent mechanical properties can be ascribed to the combined effects of the fine DRX grains with high fraction of HAGBs and the fine second-phase particles with a uniform distribution.

Virtual sensing for gearbox condition monitoring based on kernel factor analysis

Vibration and oil debris analysis are widely used in gearbox condition monitoring as the typical indirect and direct sensing techniques. However, they have their own advantages and disadvantages. To better utilize the sensing information and overcome its shortcomings, this paper presents a virtual sensing technique based on artificial intelligence by fusing low-cost online vibration measurements to derive a gearbox condition indictor, and its performance is comparable to the costly offline oil debris measurements. Firstly, the representative features are extracted from the noisy vibration measurements to characterize the gearbox degradation conditions. However, the extracted features of high dimensionality present nonlinearity and uncertainty in the machinery degradation process. A new nonlinear feature selection and fusion method,named kernel factor analysis, is proposed to mitigate the aforementioned challenge. Then the virtual sensing model is constructed by incorporating the fused vibration features and offline oil debris measurements based on support vector regression. The developed virtual sensing technique is experimentally evaluated in spiral bevel gear wear tests,and the results show that the developed kernel factor analysis method outperforms the state-of-the-art featureselection techniques in terms of virtual sensing model accuracy.

Properties and mechanism of ionic liquid/silicone oil based magnetorheological fluids

A magnetorheological fluid(MRF)is a smart composite suspension composed of nonmagnetic liquid and soft magnetic particles.Carrier fluids can considerably influence the performance of MRFs;therefore,to investigate the effect of carrier fluids on MRFs,an SO/IL-MRF was prepared by mixing an ionic liquid(IL)with silicone oil(SO)in this study.Three types of MRF samples were prepared for experiments(pure SO,pure IL,and SO/IL).According to the experi-mental results,the SO/IL-MRF has better sedimentation stability than those based on pure SO and pure IL.Further,three methods were used to determine the shear yield stresses of the MRFs.The SO/IL-MRF achieved a higher shear yield stress than those of the other two because a network structure is formed between the ionic fragments and the molecular chains of the SO in the SO/IL-MRF.This increases the movement resistance of the particles in the carrier fluid,and it is unlike the mechanism of the IL-enhanced MRF.This work provides new ideas for improving the MRF performance.

Synergistic lubricating effect of graphene/ionic liquid composite material used as an additive

We prepared a graphene/ionic liquid(G/IL)composite material by the hybridization of G and an IL for use as a lubricating oil additive.The friction coefficient and wear volume of a base oil containing 0.04 wt%of the G/IL composite was reduced by 45%and 90%,respectively.Furthermore,the base oil containing the G/IL composite exhibited better lubricating properties than the base oil containing G,IL,or a mixture of IL and G at the same mass fraction.A synergistic lubrication mechanism was also revealed.The G/IL composite was adsorbed and deposited on the wear surface,forming a more ordered protective film and a unique tribochemical reaction film during rubbing.Therefore,the G/IL composite exhibited the synergistic lubricating effects of G and IL,which significantly improved the lubricating performance of the base oil.This study also suggested a way to limit the out-of-plane puckering of G at the macroscale.