Slump Test: A New Empirical Model for High Yield Stress Materials

In order to decrease the fitting deviation between rheometrical measurements and empirical parameters using slump test, this paper proposes a new analytical method to evaluate the high yield stress of materials (cement pastes).In doing so, an experimental study was performed for measuring the empirical characteristics by cylindrical mold with different water to binder ratios (w/b) by aiming to increase the yield stress. Parallelly, experimental observations showed clearly the unyielded zone at flow stoppage of high yield stress samples. Based on these results, an idea was formed to applied metallic element at inlet of mold in order to push the spreading of paste. The obtained results of the model proposed in this paper were compared with the yield stress evaluated from shear flow curves using AR2000-rheometer with plate-plate geometry at rate-controlled. In fact, this study demonstrates the applicability and novelty of the present model in the process of relating the empirical parameters to yield stress.

Effects of Front Plate Geometry on Brush Seal in Highly Swirling Environments of Gas Turbine

Advanced brush seal technology has a significant impact on the performance and efficiency of gas turbine engines. However, in highly inlet swirling environments, the bristles of a brush seal tend to circumferentially slip, which may lead to aerodynamic instability and seal failure. In this paper, seven different front plate geometries were proposed to reduce the impact of high inlet swirl on the bristle pack, and a three-dimensional porous medium model was carried out to simulate the brush seal flow characteristics. Comparisons of a plane front plate with a relief cavity, plane front plate with axial drilled holes, anti-“L”-type plate and their relative improved configurations on the pressure and flow fields as well as the leakage behavior were conducted. The results show that the holed front plate can effectively regulate and control the upstream flow pattern of the bristle pack, inducing the swirl flow to move radially inward, which results in decreased circumferential velocity component. The anti-“L” plate with both axial holes and one radial hole was observed to have the best effect on reducing the swirl of those investigated. The swirl velocity upstream the bristle pack can decline 50% compared to the baseline model with plane front plate, and the circumferential aerodynamic forces on the bristles, which scale with the swirl dynamic head, are reduced by a factor of 4. This could increase the bristle stability dramatically. Moreover, the front plate geometry does not influence the leakage performance significantly, and the application of the axial hole on the front plate will increase the leakage slightly by around 3.5%.

THE EFFECT OF PLATE GEOMETRY OF FLAT PLATE SOLAR COLLECTOR UNDER VARIABLE HEAT FLUX

In the current study, the effect of different plate geometry namely smooth plate (traditional model) and V-corrugated plate (new model) on the output of the FPSC is conducted numerically and experimentally. The outdoor experimental work has been done in Baghdad- Iraq. All geometric models and the numerical simulations were carried out in the current study using the commercial CFD method, ANSYS 19. R3. The results indicated that the difference between numerical results and experimental findings is 8.12 % for average water temperature in a tank, while the working fluid temperature at the exist of riser pipe is about 8.36 %. The thermal performance for the new model is found higher than that for traditional model. The thermal performance of new model in terms of water temperature inside the tank was found higher than traditional model by 10.7 %. In addition, the overall thermal efficiency of collector for the new model has been increased about 9.9 % than traditional model.

COMPUTATION OF PLATE GEOMETRY OF DRIVE CHAIN FOR VALVE TIMING GEARS OF VEHICLES

The purpose of the study is to evaluate the geometric parameters of the plates of roller chains used in the supply of gas distribution mechanisms of motor vehicles. The method used is an analytical representation of the dependencies of the plate shape. The relevance of the proposed approach is justified by the great complexity of pre-design studies for choosing the type of drive chain of various mechanisms. Main results-dependences are proposed for determining the area of plates both with the "eight" type shape of the inner link of a standard roller (bushing) chain, and plates with straight side faces, and it is reasonable to choose the design of the drive chain for the specified operating loading conditions. Dependencies have a scientific novelty and practical significance when used in the production activities of employees of technological departments and design services of machine-building and auto repair enterprises.

Use of diffusive and empirical models to predict drying rate of acerola seeds (Malpighia sp.)

The thin layer drying process of acerola seeds was analyzed using a flat plate geometry diffusion model, Page's model, and a two-part model proposed based on the diffusion equation. These models were fitted to experimental drying kinetics data of acerola seeds for an air flow speed of 1.5 m/s, at temperatures of 40, 50, 60 and 70°C, using non-linear regression by Levenberg-Marquardt method. The diffusion model was used to determine the diffusion coefficients and activation energy. The predicted and experimental results were compared using the determination coefficient (R2) and mean square error (MSE) of the estimates as criteria. The results showed that the diffusion model is not suitable for predicting the drying rate of acerola seeds, while Page’s equation and the two-part proposed model can be safely used to predict the drying rates.

Size Effect on the Acoustic Emission Behavior of Textile-Reinforced Cement Composites

Acoustic emission (AE) is applied for the structural health evaluation of materials. It commonly uses piezoelectric sensors to detect elastic waves coming from energy releases within the material. Concerning cementitious composites as well as polymers, AE parameters have proven their potential to not only detect the existence of a defect, its location and the fracture mode, but also the developing strain field even before visible damage evolves. However, the wave propagation distance, wave dispersion due to plate geometry, heterogeneity and reflections result in attenuation and distortion of the AE waveforms. These factors render the interpretation more complex, especially for large samples. In this study, the effect of wave propagation on plain glass textile-reinforced cement (TRC) plates is investigated. Then, curved plates with different widths are mechanically loaded for bending with concurrent AE monitoring. The aim is to evaluate to what extent the plate dimensions and propagation distance influence the original AE characteristics corresponding to a certain fracture mechanism.

Analisa Pengaruh Bentuk Impingement Plate Terhadap Perpindahan Panas Pada Zona Desuperheating High Pressure Heater

High Pressure Heater (HPH) are tools that used to improve the efficiency of boiler. HPH utilizes hot steam from turbine extraction as heating medium before entering into the economizer in boiler. In the industry, High Pressure Heater is one of the tools that includes a heat exchanger. To prevent from several problems, some of the industries applying a plate that called impingement plate. This plate placed on the shell side Steam inlet of High Pressure Heater with the function to protect the tube facing the directly the shell side input flow. To determine the effect of adding impingement plates on heat transfer that occurs in the desuperheating zone, a simulation was performed using CFD software with variations of conventional flat plates, 4 plates, and inclined plates. From the simulation results using CFD software it is known that after the addition of the impingement plate, the largest heat transfer value in the desuperheating zone is found in the inclined plate geometry followed by the 4 plate geometry and conventional flat plate, with a q value of 9.54 MW; 7.93 MW; and 4.16 MW, respectively. Then for the inclined plate geometry pressure drop value has a small pressure drop plaing value, which is equal to 30.04 kPa.

SEISMOTECTONIC DEFORMATIONS IN THE PACIFIC AND OKHOTSK LITHOSPHERIC PLATES CONTACT ZONE

The seismotectonic deformations were determined in the Pacific and Okhotsk (Eurasian) lithospheric plates subduction zone based on 2458 mechanisms of earthquake foci data for 1977-2019. The deformation features of medium in different deep layers are shown. The deformation field uniformity in the depth range of 1-70 km and the deformation field inhomogeneity for the submerged plate deep parts (105-200, 200-400 and 400-700 km) are revealed. One of the deformations field change reasons is the influence of ascending and, especially, descending currents of thermogravitational convection in the upper mantle sublithospheric part, in particular, the convection structure influence on the subducting plate geometry

Concurrent Lamination and Tapering Optimization of Cantilever Composite Plates under Shear

The operational performance of cantilever composite structures can benefit from both stiffness tailoring and geometric design, yet, this potential has not been fully utilized in existing studies. The present study addresses this problem by simultaneously optimizing layer and taper angles of cantilever laminates. The design objective is selected as minimizing the average deflection of the tip edge subjected to shear loads while keeping the length and total volume constant. The plate stiffness properties are described by lamination parameters to eliminate the possible solution dependency on the initial assumptions regarding laminate configuration. The responses are computed via finite element analyses, while optimal design variables are determined using genetic algorithms. The results demonstrate that the plate aspect ratio significantly influences the effectiveness of stiffness tailoring and tapering as well as the optimal layer and taper angles. In addition, concurrent exploitation of the lamination characteristics and plate geometry is shown to be essential for achieving maximum performance. Moreover, individual and simultaneous optimization of layer and taper angles produce different optimal results, indicating the possible drawback of using sequential approaches in similar composite design problems.