Grid Plate Research Articles

The calculation of in-plane equivalent elastic parameters of a grid beetle elytra plate core

To study the mechanical properties of beetle elytra plates (BEPs) with numerical and theoretical methods, this paper selects the basic unit according to the periodicity of the core layer of grid beetle elytra plates (GBEPs) and establishes an equivalent model of the GBEP core layer. The equivalent Young's modulus and equivalent Poisson's ratio of the unit are obtained on the basis of structural mechanics and the energy method. Compared with the results of finite element method (FEM) simulation, the calculation results of this equivalent model are sufficiently accurate when λ1 (the ratio of the cylinder radius to the wall thickness of a core unit) is within a certain range. Compared with the case of the grid plate (GP) core unit of the same size, the elastic parameters of the GBEP core unit show no superiority when buckling is not considered. The in-plane equivalent Young's modulus of the GBEP core unit can reach 7 times that of the honeycomb core element of a similar size, and the larger λ1 is, the higher the GBEP core unit performance. In this paper, an equivalent model of GBEPs is established and compared with GPs and honeycomb plates (HPs) in FEM and theoretical analysis, laying a foundation for the application of the equivalent model in FEM analysis.

Experimental and numerical studies of wind-resistance performance of twin-box girder bridges with various grid plates

The thin-walled grid plate is one of the passive aerodynamic measures for suppressing vortex-induced vibration (VIV) of twin-box girder bridges. However, the effectiveness of the grid plate in aerodynamic stabilization is not fully known. In this study, we compared the flutter performance and aerostatic performance, as well as VIV performance, of a twin-box girder suspension bridge with four different grid porosities, through a series of wind-tunnel tests and three-dimensional nonlinear finite-element analyses. Results show that a thin-walled grid plate with larger grid porosity could effectively improve both the flutter performance and aerostatic performance of the bridge. This was particularly true with a plate of 100% grid porosity. Based on the 3D nonlinear bridge finite-element model, the flutter divergence mode of a 3D bridge is caused mainly by symmetrical vertical bending as grid porosity increases. Furthermore, the torsional VIV performance of a twin-box girder with smaller grid porosity is superior to those with larger grid porosity, and the application of grid plates of 30% and 50% porosity can result in VIV performance that complies fully with both the wind-resistance specification of China and the Sperling indicator.

Autonomous spheroid formation by culture plate compartmentation

Scaffold-free 3D cell cultures (e.g. pellet cultures) are widely used in medical science, including cartilage regeneration. Their drawbacks are high time/reagent consumption and lack of early readout parameters. While optimisation was achieved by automation or simplified spheroid generation, most culture systems remain expensive or require tedious procedures. The aim of this study was to establish a system for resource efficient spheroid generation with additional early readout parameters. This was achieved by a new approach for spheroid generation via self-assembly from monolayer via compartmentation of cell culture surfaces utilising laser engraving (grid plates). The compartmentation triggered contraction and rolling up of the cell monolayer, finishing in condensation into a spheroid in human adipose-derived stem cell (ASC/TERT1) and human articular chondrocytes (hACs)-ASC/TERT1 co-cultures, when cultivated on grid plates under chondrogenic conditions. Plates with 1 and 3 mm grid size yielded stable diameters (about 140 µm and 300 µm, respectively). ASC/TERT1 spheroids fully formed within 3 weeks while co-cultures took 1–2 weeks, forming significantly faster with increasing hAC ratio (p < 0.05 and 0.01 for 1:1 and 1:4 ASC/TERT1:hAC ratio, respectively). Co-cultures showed slightly lower spheroid diameters, due to earlier spheroid formation and incomplete monolayer formation. However, this was associated with a more homogeneous matrix distribution in the co-culture. Both showed differentiation capacity comparable to standard pellet culture in (immune-)histochemistry and RT-qPCR. To assess usability for cartilage repair, spheroids were embedded into a hydrogel (fibrin), yielding cellular outgrowth and matrix deposition, which was especially pronounced in co-cultures. The herein presented novel cell culture system is not only a promising tool for autonomous spheroid generation with the potential of experimental and clinical application in tissue engineering, but also for the generation of ‘building blocks’ for subsequential biofabrication strategies such as bioprinting.

A new type of bionic grid plate—The compressive deformation and mechanical properties of the grid beetle elytron plate

To develop lightweight and biomimetic structural materials, in this paper, the compressive deformation and mechanical properties of the grid beetle elytron plate (GBEP) with the same core volume as the end-trabecular beetle elytron plate (EBEP) under compression were investigated for the first time. (1) The B-type deformation mode of trabeculae is clarified, which is a higher stage of independent deformation than the Φ-type deformation mode in the beetle elytron plate (BEP). Additionally, the four deformation modes of the BEP are divided into three stages in succession from easy to difficult: C-type, Φ-type and S (B)-type deformation. This paper verifies that the compressive strength and energy absorption capacity of the GBEP increase by 35% and 87%, respectively, relative to those of the grid plate (GP) with the same volume. (2) Although the number of trabeculae of the GBEP is significantly less than that of the EBEP, each trabecula in the GBEP has one more honeycomb wall constraint than each trabecula in the EBEP. The increase range of the compressive properties of the GBEP relative to the GP is greater than that of the EBEP relative to the honeycomb plate (HP). This confirms the prediction that the compressive properties can be effectively improved by appropriately increasing the constraints on the trabeculae. This paper deepens and enriches the knowledge regarding the biomimetic application system of BEPs, lays the foundation for GBEPs, whose preparation is convenient, and accelerates the applications of GBEPs.

Numerical simulation and structure optimization of control rod drop impact in floating reactor

In order to simulate the impact of control rod assembly on upper grid plate of reactor core after emergency shutdown of offshore floating reactor, the structure size of upper grid plate was optimized. In this study, ADAMS simulation software was used to simulate the impact stress and strain of 50 mm and 100 mm thick upper grid plate with and without spring buffer at 0.5 m / s impact speed. Therefore, the thickness of the buffer plate on the grid can be reduced, and the simulation results show that the buffer plate can be optimized effectively.

Особенности сложных колебаний гибких микрополярных сетчатых панелей

In this paper, a mathematical model of complex oscillations of a flexible micropolar cylindrical mesh structure is constructed. Equations are written in displacements. Geometric nonlinearity is taken into account according to the Theodore von Karman model. A non-classical continual model of a panel based on a Cosserat medium with constrained particle rotation (pseudocontinuum) is considered. It is assumed that the fields of displacements and rotations are not independent. An additional independent material parameter of length associated with a symmetric tensor by a rotation gradient is introduced into consideration. The equations of motion of a panel element, the boundary and initial conditions are obtained from the Ostrogradsky – Hamilton variational principle based on the Kirchhoff – Love’s kinematic hypotheses. It is assumed that the cylindrical panel consists of n families of edges of the same material, each of which is characterized by an inclination angle relative to the positive direction of the axis directed along the length of the panel and the distance between adjacent edges. The material is isotropic, elastic and obeys Hooke’s law. To homogenize the rib system over the panel surface, the G. I. Pshenichnov continuous model is used. The dissipative mechanical system is considered. The differential problem in partial derivatives is reduced to an ordinary differential problem with respect to spatial coordinates by the Bubnov – Galerkin method in higher approximations. The Cauchy problem is solved by the Runge – Kutta method of the 4th order of accuracy. Using the establishment method, a study of grid geometry influence and taking account of micropolar theory on the behavior of a grid plate consisting of two families of mutually perpendicular edges was conducted.

Model and Experiment on Resistance Loss of Wet Chordal Grid with Spray Pressure and Structural Parameters

To reduce the dedusting resistance of wet vibrating string grille precipitators during dedusting in mine ventilation roadways, we investigated the dedusting resistance characteristics of water fog and water film coupling and determined the relationship between dedusting resistance and spray pressure, vibrating grid filling rate, and wind speed. A mathematical resistance coefficient model is established using hydrodynamics theory and capillary mechanics. The theoretical relationship of dedusting resistance is deduced. The results show that when wind speed is constant, the spray pressure and dedusting resistance are higher and the resistance is smaller with a high filling rate compared with a low filling rate. Constant spray pressure allows faster wind speeds and reverse pressure gradient forces to increase when dust flows around the wet vibrating wire, which makes the pressure distribution asymmetrical around the steel wire and increases resistance. Dust removal resistance of the resonance chord with a high filling rate is substantially lower than that with a low filling rate under the same working conditions. On the basis of satisfying the dedusting efficiency, the resonance chord dedusting system does not affect normal production and resistance is low. The spray pressure is controlled at 0.3–0.7 MPa and the optimal wind speed is 3–4 m/s. According to the theoretical calculation and experimental data, the optimal filling rate of a vibrating string grid plate is 77.8%, spray pressure is 0.7 MPa, and wind speed is 3.5 m/s. Dust removal with low resistance and improved economic benefit can thus be obtained.

Overview on Hardfacing Processes, Materials and Applications

Hardfacing alloys are mainly obtained through atomization of powders and by determining of alloying elements in pure form or ferro alloys. They are widely used materials as weld overlay to improve wear and corrosion resistance in applications such as agricultural, construction, mining, etc. Wear is an important factor that controls life of any component. Different types of wear such as corrosion, impact, abrasion, metallic, etc are responsible for worn out of components. Many researches have been done to either reduce the wear or improve the wear resistant of the existing materials. Among these, hardfacing technique has made many developments since last few years. As in nuclear reactors, hardfacing of the grid plate through Laser cladding and Plasma Transferred arc welding, to improve the life of the components and resistance from wear and corrosion. Hardfacing involves applying a consumable material with desired wear properties over a soft base metal to enhance resistance to different wear mechanism. Using Calphad technique for development of desired composition and application of Schaffler diagram has been attempted successfully. In this paper a review of hardfacing processes and materials, highlighting the use of Laser cladding and Plasma transfer arc for overlaying hardfacing alloys has been attempted.

DESIGN OF NEUTRONIC PARAMETERS OF MTR REACTOR USING WIMSD-5B/BATAN-FUEL CODES

BATAN has three aging research reactors, so it is necessary to design a new, more modern MTR type reactor using high-density, low enrichment uranium molybdenum fuel. The thermal neutron flux at the irradiation position is an important concern in the design of research reactors. This analysis is performed using standard computer codes WIMSD-5B and Batan-FUEL. The purpose of this study is to analyze the effect of the core configuration with safety control rods and neutronic parameters using the diffusion method calculation. The reactor core consists of 16 fuel elements and four control rods placed in the 5 x 5 position of the grid plate and is loaded the reflector elements outside the core. The cycle length is also a concern, not less than 20 days, and the reactor can be operated safely with a power of 50 MW. The calculation results show that for the highest fuel loading, which is 450 grams of U7Mo/Al fuel with D2O as a reflector, it will provide the lowest thermal neutron flux at the center of the core irradiation position, namely 1.0 x1015 n/cm2s. The core fuel cycle length will be up to 39 days, meeting the expected acceptance and safety criteria.

Paschen curves and current–voltage characteristics of large-area short glow discharge with different electrode structures

In this work, the Paschen curves and current–voltage characteristics of three large-area short glow discharge structures with grid and solid plate electrodes are studied. The study of the Paschen's curves reveals that Paschen's law is broken for all three investigated electrode structures. It is shown that the experimentally measured Paschen curves are well approximated with a modified Paschen's law. A comparison of the current–voltage characteristics of the short glow discharge in the three types of electrode structures reveals that the use of grid electrodes allows for the increase in the discharge current. The effects of the electrode gap, which were varied from 1 mm to 7 mm, on the Paschen curves and current–voltage characteristics of short glow discharges are also investigated.

Prediction of distance to maximum intensity of turbulence generated by grid plate obstacles in explosion-induced flows

The interaction of unburnt gas flow induced in an explosion with an obstacle results in the production of turbulence downstream of the obstacle and the acceleration of the flame when it reaches this turbulence. Currently, there are inadequate experimental measurements of these turbulent flows in gas explosions due to transient nature of explosion flows and the connected harsh conditions. Hence, majority of measurements of turbulent properties downstream of obstacles are done using steady-state flows rather than transient flows. Consequently, an empirical based correlation to predict distance to maximum intensity of turbulence downstream of an obstacle in an explosion-induced flow using the available steady state experiments was developed in this study. The correlation would serve as a prerequisite for determining an optimum spacing between obstacles thereby determining worst case gas explosions overpressure and flame speeds. Using a limited experimental work on systematic study of obstacle spacing, the correlation was validated against 13 different test conditions. A ratio of the optimum spacing from the experiment, xexp to the predicted optimum spacing, xpred for all the tests was between 2-4. This shows that a factor of three higher than the xpred would be required to produce optimum obstacle spacing that will lead to maximum explosion severity. In planning the layout of new installations, it is appropriate to identify the relevant worst case obstacle separation in order to avoid it. In assessing the risk to existing installations and taking appropriate mitigation measures it is important to evaluate such risk on the basis of a clear understanding of the effects of separation distance and congestion. It is therefore suggested that the various new correlations obtained from this work be subjected to further rigorous validation from relevant experimental data prior to been applied as design tools.

Multi-objective design optimization of variable ribs composite grid plates

Grid structures are among the most lightweight elements for stiffening the plates and shells or as self-sufficient structures. There are different known grid patterns, which are composed of variable numbers of parallel ribs. Selecting an optimum pattern and geometries for a grid to achieve the minimum weight and maximum load-bearing capacity is a challenging procedure for designers. In the current study, a variable ribs model (VRM) is proposed to find the optimum architecture of a grid plate. Therefore, using a genetic algorithm process, a multi-objective optimization is implemented to maximize the axial or shear buckling loads at a minimum possible weight of a grid structure. Eleven geometrical parameters including thickness, width, and the number of ribs as well as the orientation of the grid plate are considered the design variables. The multi-objective optimization is carried out employing the e-constraint method. The buckling loads are obtained based on the first-order shear deformation plate theory using the Ritz method.

Enhancing Flow Field Performance of a Small Circulating Water Channel Based on Porous Grid Plate

Low-cost and high-efficiency circulating water channels are widely used in the hydrodynamic tests of an underwater device. The current research mainly focuses on obtaining a better velocity uniformity of the test section by optimizing the curve function of the boundary in the contraction section. While, for small underwater device, their hydrodynamic characteristics are sensitive to turbulence. Thus, the circulating water channel, which can obtain the required turbulence characteristics, is urgently needed. A small circulating water channel, which can reduce the turbulence intensity based on a porous grid plate and can be used to test the hydrodynamic characteristics of a small underwater device, is designed. The relationships between porosities and resistance coefficients of a porous grid plate are established. The effects of the honeycomb (porosity and thickness); screen (porosity, number of layers, and spacing); and pumping flow rate on the turbulent characteristics of the test section are studied. The relationships between the parameters and the turbulent characteristics of the test section are established, and the methods to achieve the required flow characteristics of the test section are proposed. Experiments are carried out, and the validity of the obtained results is verified. In this work, the turbulence intensity of the fluid field in the test section can be restrained to 0.0491, which is enough to meet the turbulence requirements for the hydrodynamic test of a small underwater device. This work can provide references for the construction of a hydrodynamic test platform for small underwater devices.

Development of methods for optimal assembly orificing design and application to a standing-wave Breed-and-Burn reactor

This work investigates different orificing strategies in sodium fast reactors and their application to a reference standing-wave Breed-and-Burn (B&B) core. Through analytic means, the standard method of static integral orificing is shown to be infeasible in the reference core. Using simplified physical models, a novel Mixed-Integer Linear Programming (MILP) formulation is proposed to design whole-core assembly-level orificing schemes according to constraints on various operating conditions, including peak and average temperatures, mass flowrates, flow velocities, and outlet temperature profiles. After highlighting the major assumptions employed and quantifying their impacts, the MILP formulation is used to assess two alternative methods of assembly orificing, namely static grid plate and variable orificing. These two methods of orificing are found to be suitable to B&B cores, and their sensitivities to various constraints are examined. Ultimately the use of variable orificing is found to be the most desirable from the perspectives of flexibility and ability to cope with difficult constraints, although it may be the most difficult of the three methods to implement in a realistic core design.

Multi-objective optimization of composite angle grid plates for maximum buckling load and minimum weight using genetic algorithms and neural networks

The present work describes an optimization process based on the ε-constraint method to find an optimum design to maximize the critical buckling load and minimize the structural weight of an angle grid plate. A comprehensive geometrical model is considered including all geometrical design variables of the grid. In order to achieve a precise and effective approximation of the buckling load, an artificial neural network (ANN) is employed. Training data for ANN is obtained by the Mindlin plate theory as well as the Ritz method. The ANN is combined with genetic algorithms (GA) to find the optimized design variables for an angle grid structure. The results provide a wide range of geometrical data for designers to choose the maximum buckling load at the minimum structural weight.

Management of Angle Mandible Fractures by 3D Rectangular Grid Plate: A Prospective Study.

This study aims to evaluate the clinical outcomes of treatment of mandibular angle fractures using 3D rectangular grid plate. A total of 10 patients with mandibular angle fractures with or without associated facial fractures requiring open reduction and internal fixation were included in the study. Fixation was done using 3D rectangular grid plate. The mean age of the patients in the study is 34.7 years. In all the cases, fracture was adequately reduced (100%) intraoperatively and confirmed through postoperative radiographs. The mean mouth opening by the end of 3 months is 38.60 mm. Four patients had paresthesia of inferior alveolar nerve pre- and postoperatively, and normal sensation was regained by the end of the third month. There were no reported cases of infection and hardware failure during the 9-month follow-up period. The results of the study suggest that 3D rectangular grid plate is a feasible alternative to conventional miniplate systems with good clinical outcome and fewer complications related to paresthesia, infection and hardware failure.

Fabrication of Laminated Composite Grid Structures Using VIP

In this study, the fabrication of laminated composite grids, as a new class of grid structures, is presented. These structures can be constituted from a various number of grid layers, with different patterns, fibers and orientations. This concept yields to a large variety of laminated grid configurations with different coupling effects compare to conventional grids. In the current study, the fabrication of a laminated grid plate, which composed of four orthogrid layers, is presented. The vacuum infusion process (VIP) is employed to manufacture the specimen. Moreover, a simulation is conducted using COMSOL Multiphysics software to determine the appropriate locations of resin inlet and air vent tubes. The degrees of cure and temperature profiles of the specimen are obtained in simulation and experimental studies. The results show, the simulation fits the experimental observations reasonably well and the VIP method is confirmed to be appropriate for manufacturing the high-quality laminated grid.

Externally generated turbulence by a vertically oscillating grid plate and its impact on sediment transport rate

ABSTRACTThe present paper concerns an experimental study of externally generated turbulence and its impact on the bed load sediment transport in an open channel flow. The external turbulence was generated by vertically oscillating a submerged grid, hereafter referred to as turbulence generator, in the flume with a clearance of 11 cm from the bed. Two kinds of experiments were performed: rigid flat-bed and plane sand-bed. One two-dimensional (2-D) LDA was set up to measure the velocity profiles for different values of flow discharge, amplitude and period of oscillations of the turbulence generator. The mean velocities, turbulence intensities, Reynolds shear stress, and their impacts on the rate of sediment transport have been analyzed. The fractional contributions of burst-sweep cycles to the Reynolds shear stress have also been studied. The turbulence generated due to a vertically oscillating-submerged grid is an analogous to the production of turbulence beneath the roller located on the front of broken wave, and the impact thus lies on the sediment transport. The Shields parameter was found to be correlated with the sediment transport rate, and the transport rate as a function of turbulence level is found to increase with turbulence level.

Experimental identification of pressure drop characteristics at the shell side of an intermediate heat exchanger inside a prototype generation-IV sodium-cooled fast reactor

The flow characteristics at the shell side of a prototype intermediate heat exchanger (p-IHX) in a prototype generation-IV sodium-cooled fast reactor (PGSFR) were investigated experimentally in this study. The shell side of the p-IHX consisted of an inlet window, tube bundles, grid plates, and an exit flow channel. Two different test facilities were newly constructed to identify the pressure drop characteristics due to the complicated configuration with minimized scaling distortion. An intermediate heat exchanger test loop for PGSFR (iHELP) was constructed to characterize the flow resistance of the tube bundle regions with the grid plates and inlet window. The iHELP test section with a slab-shaped cross section was manufactured with a 1/29.6 vol scale ratio by preserving the height of the p-IHX. The hydraulic diameter at the tube bundle regions, the porosity of the grid plates, and the configuration of the tube bundles were conserved. In addition, the Reynolds number was preserved, which determined the flow rate conditions for the iHELP experiments. To investigate the pressure drop characteristics of the exit flow channel (EC), an intermediate heat exchanger test loop for the exit flow channel (IEC) was built with a 1/5 linearly reduced length scale by preserving the geometry of the flow path based on the EC of the p-IHX. The Euler number was conserved with a 1/8 Reynolds number ratio corresponding to a 1/1 flow velocity ratio to the p-IHX for dynamic similarity. By using each test facility the experimental pressure drop data satisfying the experimental uncertainty requirements were obtained separately for the bundle and exit channel regions. The pressure drop at the shell side of the p-IHX under a wide range of flow rate conditions was determined by using the pressure drop results from the iHELP and the IEC test facilities, which would be useful in improving and validating the pressure drop correlations in the IHX design computational code (SHXSA).

Bubble image velocimetry with a field-deployable acoustic camera

This study explores performing bubble image velocimetry (BIV) analysis on images acquired from an acoustic camera (AC) to obtain measurements of the flow in the wake of a circular cylinder at two flowrates. The AC observes the returns from air micro-bubbles suspended in the flow which are used as tracer particles in PIV-style analysis. The size distribution of the micro-bubbles is measured with an acoustic bubble spectrometer (ABS). The AC BIV measurements of the wake agree well with the comparison measurements made by cross-stream arrays of acoustic Doppler velocimeters (ADVs) for the lower of the two measured flowrates. The AC BIV measurements of cross-stream profiles of the mean downstream velocities and the profiles of characteristics of the velocity fluctuations, such as the standard deviation of the downstream and cross-stream velocity fluctuations, the covariance of the horizontal velocity fluctuations, and the kinetic energy of the horizontal velocity fluctuations, all matched the ADV measurements well. However, the measurement technique is sensitive to bubble size distribution, as the higher flowrate AC BIV measurements struggled to replicate the ADV measurements, particularly the measurements of the velocity fluctuations. The higher flowrate experiment is revealed to have an order of magnitude more bubbles with size exceeding 15 present in the flow than the lower flowrate experiment. The increased bubble density caused increased noise in the AC images and a ‘flickering’ effect, with bubbles further away from the camera being intermittently obscured by those closer to the camera. The ability to make PIV-style measurements with an AC has ramifications for flow measurements in the field. ACs operate in turbid environments, do not require a laser and extensive optics, and do not require calibration with a grid plate to convert pixel space to physical space.