Thermal-mechanical response of microscale functional film for infrared window

Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight.A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions.Temperature and stress distribution were obtained with different heat fluxes.There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate.The maximum stresses are located at the points which are 0.3 mm away from the edges.Different film materials result in different stress values.The temperature and stress in ZrN are larger than those in Y2O3.Besides the numerical simulation,an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window.Some place of the window surface has spots damage and some place has line crack damage after thermal shock.

兴隆船闸人字门背拉杆预应力施工

背拉杆作为人字门的主要构件之一,在提高闸门刚度、减少扭曲变形、增强使用寿命中起着重要的作用。人字门在关闭挡水状态下,成三角拱受力状态,门叶所受的压力通过斜接柱、门轴柱传递给闸墙,门叶在自由悬挂状态下处于底枢、顶枢、推力拉杆三点约束下。主要介绍兴隆船闸人字门背拉杆预应力施工,为以后类似人字门背拉杆预应力施工提供参考。

3D density inversion of gravity gradient data using the extrapolated Tikhonov regularization

We use the extrapolated Tikhonov regularization to deal with the ill-posed problem of 3D density inversion of gravity gradient data. The use of regularization parameters in the proposed method reduces the deviations between calculated and observed data. We also use the depth weighting function based on the eigenvector of gravity gradient tensor to eliminate undesired effects owing to the fast attenuation of the position function. Model data suggest that the extrapolated Tikhonov regularization in conjunction with the depth weighting function can effectively recover the 3D distribution of density anomalies. We conduct density inversion of gravity gradient data from the Australia Kauring test site and compare the inversion results with the published research results. The proposed inversion method can be used to obtain the 3D density distribution of underground anomalies.

Solution to 1-D consolidation of non-homogeneous soft clay

In this work, semi-analytical methods were used to solve the problem of 1-D consolidation of non-homogeneous soft clay with spatially varying coefficients of permeability and compressibility. The semi-analytical solution was programmed and then verified by comparison with the obtained analytical solution of a special case. Based on the results of some computations and comparisons with the 1-D homogeneous consolidation (by Terzaghi) and the 1-D non-linear consolidation theory (by Davis et al.) of soft clay, some diagrams were prepared and the relevant consolidation behavior of non-homogeneous soils is discussed. It was shown that the result obtained differs greatly from Terzaghi’s theory and that of the non-linear consolidation theory when the coefficients of permeability and compressibility vary greatly.

Nonlinear analysis of consolidation with variable compressibility and permeability

Terzaghi gave a theory of soil consolidation based on the effective stress principle, which was derived on several ideal assumptions to get a simplified theory. To avoid the limitations involved in Terzaghi’s theory, many efforts are being made by scholars to solve the problems in practical engineering situations. This paper presents a generalized theory for one dimensional consolidation of saturated soft clay with variable compressibility and permeability. The semi-analytical solution presented here takes into account the well known empirical e-logk and e-logp′(σ′) relations under instantaneous loading. Study of the consolida- tion behaviors showed that the ratio of Cc and Ck (the slope of e-logp and e-logk respectively) govern the ratio of consolidation. A simulative laboratory investigation with GDS advanced consolidation system was made to analyze the clay consolidation process and compare the results with the semi-analytical solution.

Analytical solution for evaluating deformation response of existing metro tunnel due to excavation of adjacent foundation pit

The excavation of foundation pit generates soil deformation around existing metro tunnel with shield driving method,which may lead to the deformation of tunnel lining.It is a challenge to evaluate the deformation of shield tunnel accurately and take measures to reduce the tunnel upward displacement as much as possible for geotechnical engineers.A new simplified analytical method is proposed to predict the longitudinal deformation of existing metro tunnel due to excavation unloading of adjacent foundation pit in this paper.Firstly,the additional stress of soils under vertical axisymmetric load in layered soil is obtained by using elastic multi-layer theory.Secondly,the metro tunnel is regarded as a Timoshenko beam supported by Winkler foundation so that the shear effect of tunnels can be taken into account.The additional stress acting on the tunnel due to excavation unloading in layered soil are compared with that in homogeneous soil.Additionally,the effectiveness of the analytical solution is verified via two actual cases.Moreover,parametric analysis is conducted to investigate the responses of the metro tunnel by considering such factors as the variation of subgrade coefficient,offset distance from the excavation center to tunnel longitudinal axis as well as equivalent shear stiffness.The proposed method can be used to provide theoretical basis for similar engineering project.

Coefficients of earth pressure at rest in thick and deep soils

The effect of test methods and stress paths on the experimental value of the coefficient of earth pressure at rest, K0, was investigated under high pressures. The results indicate that the rigid pressure chamber and flexible lateral confining pressure medium method gives a stress ratio at the initial stage that is not the real K0. Moreover, K0 increases during the loading process becoming greater at high pressures. In the unloading process, however, K0 increases only at the initial stage but decreases thereafter. In addition, the incremental magnitude definition, K0=dσ3/dσ1, gives higher values than the total magnitude definition, K0=σ3/σ1, under loading. This is also true during initial stages of unloading. The experiment results also indicate that earth pressure at rest in deep and thick soils can be estimated by a power function of axial and confining pressures. It is necessary to choose the appropriate Kn to avoid some accidents.

Global lateral buckling analysis of idealized subsea pipelines

In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty,usually high temperature and high pressure are used in the transportation of oil and gas.The differences of temperature and pressure cause additional stress along the pipeline,due to the constraint of the foundation soil,the additional stress can not release freely,when the additional stress is large enough to motivate the submarine pipelines buckle.In this work,the energy method is introduced to deduce the analytical solution which is suitable for the global buckling modes of idealized subsea pipeline and analyze the relationship between the critical buckling temperature,buckling length and amplitude under different high-order global lateral buckling modes.To obtain a consistent formulation of the problem,the principles of virtual displacements and the variation calculus for variable matching points are applied.The finite element method based on elasto-plastic theory is used to simulate the lateral global buckling of the pipelines under high temperature and pressure.The factors influencing the lateral buckling of pipelines are further studied.Based upon some actual engineering projects,the finite element results are compared with the analytical ones,and then the influence of thermal stress,the section rigidity of pipeline,the soil properties and the trigging force to the high order lateral buckling are discussed.The method of applying the small trigging force on pipeline is reliable in global buckling numerical analysis.In practice,increasing the section rigidity of a pipeline is an effective measure to improve the ability to resist the global buckling.

Seismic stability of reinforced soil walls under bearing capacity failure by pseudo-dynamic method

In order to evaluate the seismic stability of reinforced soil walls against bearing capacity failure,the seismic safety factor of reinforced soil walls was determined by using pseudo-dynamic method,and calculated by considering different parameters,such as horizontal and vertical seismic acceleration coefficients,ratio of reinforcement length to wall height,back fill friction angle,foundation soil friction angle,soil reinforcement interface friction angle and surcharge.The parametric study shows that the seismic safety factor increases by 24-fold when the foundation soil friction angle varies from 25°to 45°,and increases by 2-fold when the soil reinforcement interface friction angle varies from 0 to 30°.That is to say,the bigger values the foundation soil and/or soil reinforcement interface friction angles have,the safer the reinforced soil walls become in the seismic design.The results were also compared with those obtained from pseudo-static method.It is found that there is a higher value of the safety factor by the present work.

A fast explicit finite difference method for determination of wellhead injection pressure

A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.

Effects of GPU Structuring on Accelerated Schemes of LBM and Classical CFD for Flow over a Flat Plate

Current trends on CFD （Computational Fluid Dynamics） along with high performance computing are moving towards using modem GPUs （Graphics Processing Units） in order to achieve substantial execution speedup. Consequently, it is definitely crucial to have some understanding about execution time of different computational methods and parallelization procedures. In this study, two GPU accelerated schemes namely LBM （Lattice Boltzmann Method） and SFV （Stream Function-Vorticity） formulation are investigated and compared for simulation of flow over a fiat plate. The comparisons are based on solvers runtime and speedup and GPU type of structuring. On study the authors found that although the runtime for SFV formulation is less than LBM, LBM has greater potential to obtain higher speedup by using modern GPUs like NVIDIA GTX 480. In addition, a performance sensitivity is done to investigate for different GPU type of structures as a considerable parameter. The difference between GPU runtime in optimum and regular conditions indicates that using one-dimensional structuring can improve the GPU performance about 50 percent.

Behavior of RC two-way slabs strengthened with CFRP-steel grid under concentrated loading

A novel composite technique of orthogonally bonding carbon fiber-reinforced polymer （CFRP） strips and steel strips is proposed to improve the performance of reinforced concrete （RC） structures based on co-working of CFRP strips and steel strips. To verify the effectiveness of the method for strengthening RC two-way slabs, seven flat slabs with the dimensions of i 500 mm x 1 500 mm x 70 mm and an internal reinforcement ratio of 0.22% were prepared and tested until failure under concentrated loading, of which one was unstrengthened, one was strengthened with CFRP strips bonded to its soffit making a grid pattern （termed the CFRP grid）, and five were strengthened with a hybrid grid of CFRP strips and steel strips in two orthogonal directions （termed the CFRP-steel grid） to the bottom with steel bolt anchorage. The investigation parameters are the strengthening method, the strip spacing （150, 200, and 250 mm） and the layers of CFRP strips （one layer, two layers, and three layers of CFRP strips are applied for CFRP-steel grid）. The experimental results show that the strengthening RC two-way slabs with CFRP-steel grid are effective in delaying concrete cracking and enhancing the load-carrying capacity and deformability in comparison to the CFRP grid strengthening. The yield-line analysis model is proposed to predict the load-carrying capacity of the strengthened slabs. The prediction results are in good agreement with the experimental results.

Study on Dynamic Response of Fiber-Reinforced Plastic Float for Light Seaplane

The marine area of Japan, including territorial waters and the exclusive economic zone, is the sixth largest in the world at about 4,470,000 km2. Therefore, it is becoming necessary to establish appropriate means of transportation other than ships in order to utilize the area efficiently. In this respect, ultra-light seaplanes are attracting attention from the viewpoint of protecting the natural environment. Accordingly, JRPS （Japan Reinforced Plastics Society） is currently developing FRP （fiber-reinforced plastic） floats for such planes. In this study, we conducted simulations of seaplane behavior during alighting by using the smoothed particle hydrodynamics method, which is one of the functions in the PAM-CRASH solver, and we present the observed trend in the vertical acceleration of the floats as a first step toward deriving the impact force from analytical data.

Innovative Approach to Increase Name Plate Capacity of Oil and Gas Gathering Centre

Purpose： The oil and gas gathering and processing facility of Kuwait Oil Company is built with a nameplate capacity of X MBOPD （thousand barrels oil per day） with 50% water cut. However, the facility was operating with a water cut of 35%. This comprehensive technical study was conducted to evaluate possibility of increasing oil processing capacity of this facility in line with current lower water cut and other operational flexibilities available in the facility without utilizing its design margin. Topic： This paper shares an innovative approach to increase name plate capacity of oil and gas processing facility utilizing available operational flexibility and operational margins with minor modification. It shares a case study where facility capacity is increased by around 19% without utilizing design margins of equipment or pipeline. Method： The study includes theoretical verification and analysis of all major equipment and piping to identify available capacity and limitation, in order to utilize available additional margin and to propose debottleneck options to overcome limitations. Achievement： The study confirmed that, facility name plate capacity can be revised from X MBOPD （with 50% w.c （water cut）） to X ＋ 32 MBOPD （with： 45% w.c） minor modification in separator and utilizing margin available in feed specification ofdesalter trains.

Performance of DDA time integration

Discontinuous deformation analysis(DDA) is a numerical method for analyzing the deformation of block system. It employs unified dynamic formulation for both static and dynamic analysis, in which the so-called kinetic damping is adopted for absorbing dynamic energy. The DDA dynamic equations are integrated directly by the constant acceleration algorithm of Newmark family integrators. In order to have an insight into the DDA time integration scheme, the performance of Newmark time integration scheme for dynamic equations with kinetic damping is systematically investigated, formulae of stability, bifurcation, spectral radius, critical kinetic damping and algorithmic damping are presented. Combining with numerical examples, recognition and suggestions of Newmark integration scheme application in the DDA static and dynamic analysis are proposed.

Computational Fluid Dynamics(CFD) Modeling of Heat Transfer in a Polymeric Membrane using Finite Volume Method

The efficiency,robustness and reliability of recent numerical methods for finding solutions to flow problems have given rise to the implementation of computational fluid dynamics(CFD) as a broadly used analysis method for engineering problems like membrane separation system.The CFD modeling in this study observes steady and unsteady(transient) heat flux and temperature profiles in a polymeric(cellulose acetate) membrane.This study is novel due to the implementation of user defined scalar(UDS) diffusion equation by using user-defined functions(UDFs) infinite volume method(FVM).Some details of the FVM used by the solver are carefully discussed when implementing terms in the governing equation and boundary conditions(BC).The contours of temperature due to high-temperature gradient are reported for steady and unsteady problems.