A Study on the Influences of Abrasive Media's Viscoelasticity on Entrance Effect in Abrasive Flow Machining

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Haibo Wei ◽  
Xuanping Wang ◽  
Hang Gao ◽  
Can Peng ◽  
Xuyue Wang
Keyword(s):  
Numerical Simulation ◽  
Rheological Properties ◽  
Viscoelastic Model ◽  
Flow Channel ◽  
Experimental Results ◽  
Surface Finishing ◽  
Workpiece Surface ◽  
Abrasive Flow Machining ◽  
Entrance Effect ◽  
Simulation Results

Abrasive flow machining (AFM) is a nontraditional surface finishing method that finishes complex surface by pushing the abrasive media flow through the workpiece surface. The entrance effect that the material removal increases at the entrance of changing the cross-sectional flow channel is a difficult problem for AFM. In this paper, the effects of media rheological properties on the entrance effect are discussed. To explore the effects of the media's viscoelasticity on the entrance effect, two sets of media with different viscoelasticity properties are adopted to study their rheological and machining performances in the designed flow channel with a contraction area. The rheological properties are tested by frequency sweep and characterized by the Maxwell viscoelastic model and the Carreau viscous model. In the experiment, the variation of the profile height (ΔH) and the variation ratio of the roughness (ΔRa) on the workpiece surface are measured. Moreover, numerical simulation results under different constitutive equations are compared with the experimental results. It shows that the numerical simulation results of a viscoelastic model have a better agreement with the experimental results than the viscous model, and the increase of the viscoelasticity makes the entrance effect be exacerbated, which can be predicted by the viscoelastic numerical simulation.

scholarly journals Numerical Simulations of V-Shaped Plates Subjected to Blast Loadings: A Validation Study

2016 ◽  
Vol 10 (11) ◽  
pp. 203
Author(s):  
Mohd Zaid Othman ◽  
Qasim H. Shah ◽  
Muhammad Akram Muhammad Khan ◽  
Tan Kean Sheng ◽  
M. A. Yahaya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Variable Mass ◽  
Blast Loading ◽  
Experimental Results ◽  
Average Difference ◽  
Simulation Results ◽  
Blast Loadings ◽  
Carrier Vehicle ◽  
Good Agreement

A series of numerical simulations utilizing LS-DYNA was performed to determine the mid-point deformations of V-shaped plates due to blast loading. The numerical simulation results were then compared with experimental results from published literature. The V-shaped plate is made of DOMEX 700 and is used underneath an armour personal carrier vehicle as an anti-tank mine to mitigate the effects of explosion from landmines in a battlefield. The performed numerical simulations of blast loading of V-shaped plates consisted of various angles i.e. 60°, 90°, 120°, 150° and 180°; variable mass of explosives located at the central mid-point of the V-shaped vertex with various stand-off distances. It could be seen that the numerical simulations produced good agreement with the experimental results where the average difference was about 26.6%.

scholarly journals MEMS-Based Integrated Triaxial Electrochemical Seismometer

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1156
Author(s):  
Wenjie Qi ◽  
Bowen Liu ◽  
Tian Liang ◽  
Jian Chen ◽  
Deyong Chen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Ground Motion ◽  
Small Volume ◽  
Three Dimensional ◽  
Experimental Results ◽  
Good Prospect ◽  
High Symmetry ◽  
Noise Levels ◽  
Sensitivity Curves ◽  
Simulation Results

This paper presents a micro-electromechanical systems (MEMS)-based integrated triaxial electrochemical seismometer, which can detect three-dimensional vibration. By integrating three axes, the integrated triaxial electrochemical seismometer is characterized by small volume and high symmetry. The numerical simulation results inferred that the integrated triaxial electrochemical seismometer had excellent independence among three axes. Based on the experimental results, the integrated triaxial electrochemical seismometer had the advantage of small axial crosstalk and could detect vibration in arbitrary directions. Furthermore, compared with the uniaxial electrochemical seismometer, the integrated triaxial electrochemical seismometer had similar sensitivity curves ranging from 0.01 to 100 Hz. In terms of random ground motion response, high consistencies between the developed integrated triaxial electrochemical seismometer and the uniaxial electrochemical seismometer could be easily observed, which indicated that the developed integrated triaxial electrochemical seismometer produced comparable noise levels to those of the uniaxial electrochemical seismometer. These results validated the performance of the integrated triaxial electrochemical seismometer, which has a good prospect in the field of deep geophysical exploration and submarine seismic monitoring.

An Analysis of the Evaluation Methods for Thermal Transmittance of Curtain Wall System Based on Simulators

2017 ◽  
Vol 865 ◽  
pp. 383-389 ◽  
Author(s):  
Min Jung Bae ◽  
Yu Min Kim ◽  
Gyeong Seok Choi ◽  
Jae Sik Kang ◽  
Hyun Jung Choi
Keyword(s):  
Numerical Simulation ◽  
Evaluation System ◽  
Evaluation Methods ◽  
Experimental Results ◽  
Curtain Wall ◽  
Performance Evaluation System ◽  
Thermal Transmittance ◽  
Simulation Results ◽  
Primary Evaluation ◽  
Wall System

With the window rating system being enforced, window companies are required to assign window ratings to their products. As the window ratings is based on the experimental results of fenestration, they are required to spend a lot of time and money conducting laboratory tests in order to assign window ratings to all their products. Through the window performance evaluation system using simulation, the thermal transmittance of products calculated based on numerical simulation can be used in place of experimental results to obtain the window rating. To ensure the credibility of simulation results, it is necessary to use the correct evaluation methods and primary information derived from in use practice should be available for the numerical simulation. The purpose of this paper is to investigate the evaluation methods that the simulator actually uses for the thermal performance of fenestration in WINDOW/THERM. The evaluation methods used by twenty-one simulators were investigated using primary evaluation methods for numerical simulation as the criteria. This study found that most of the simulation results were not trustworthy even though they were similar to experimental results because the evaluation methods used by simulators are incorrect. Furthermore, to enhance the credibility of simulation results, the simulator should be provided with the detailed information used in practice related to the evaluation performance of numerical simulation.

Numerical Simulation and Experimental Study of Jet Distance in Abrasive Waterjet Polishing

2012 ◽  
Vol 472-475 ◽  
pp. 2037-2042 ◽  
Author(s):  
Jia Qiang Peng ◽  
Dan Lu Song ◽  
Liang Chao Li
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Theoretical Basis ◽  
Process Research ◽  
Physical Models ◽  
Abrasive Waterjet ◽  
Workpiece Surface ◽  
Cutting Machine ◽  
Simplec Algorithm ◽  
Simulation Results

In this paper, it introduces the work principle of abrasive waterjet polishing (AWJP) and analyzes the jet distance to the influence of the AWJP under a certain pressure, with a numerical simulation and analysis to the jet distance based on jet mechanics and fluid dynamics. By establishing the physical models of the different jet distance of the AWJP and adopting the Realizable k-ε model and the SIMPLEC algorithm, it gains the jet flow field of the AWJP with different jet distance models and the distribution of turbulence intensity and pressure and velocity on the workpiece surface. The numerical simulation results of the different jet distance were analyzed and compared, according to the AWJP to the characteristic requirement of the jet. By doing the polishing experiment with a abrasive waterjet cutting machine, it verifies that the best polishing distance range of AWJP is from 10 times to 13 times of the nozzle diameter, which provides the theoretical basis for the process research of the AWPJ in the future.

Flow Field Model Experiment Studies of a Bipolar Plates PEMFC

2013 ◽  
Vol 291-294 ◽  
pp. 581-584
Author(s):  
Bing Kun Jiang ◽  
Xin Jie Ji ◽  
Yong Zhong Li
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Field Model ◽  
Flow Distribution ◽  
Flow Channel ◽  
Bipolar Plates ◽  
Gas Utilization ◽  
Section Shape ◽  
Simulation Results ◽  
Gas Supply

The mode experiment is respectively done under condition of different amount of gas supply, different shape of gas admission room, different cross-section shape of flow channel. Results show that pressure descend of U shape cross-section slot is smaller than the rectangle cross-section slot in the equal fault stream section situation, so flow distribution characteristic of U shape cross-section slot is better. The experiment results are consistent with numerical simulation results. In addition, numerical simulation results also indicate that the mass of gas diffusing from U shape cross-section slot to the diffusion layer is over greater, and U shape cross-section flow channel has a higher gas utilization ratio.

Efficiency Metallic Leading Edge Structure Bird Strike Resistant Design

2011 ◽  
Vol 338 ◽  
pp. 84-89 ◽  
Author(s):  
Mei Ying Zhao ◽  
Jing Jing Li
Keyword(s):  
Numerical Simulation ◽  
Absorption Rate ◽  
Leading Edge ◽  
Experimental Results ◽  
Structural Quality ◽  
Bird Strike ◽  
Edge Structure ◽  
Simulation Based ◽  
Simulation Results ◽  
Resistant Structure

This article investigated a new metallic leading edge bird strike resistant structure, using corrugate board as its enhanced component to absorb more bird kinetic energy. This structure was called as Corrugate Board Leading Edge (CBLE) structure. To verify the structure’s bird strike resistant ability, numerical simulation based on the LS-DYNA was carried out, and succeeding experiments were performed. However, the experimental results were not exciting. They were not as the simulation results we expected. The reasons were analyzed through this article. Finally a rivet-relative model was created considering the influence of riveting. This model was proved to be accurate by comparing with experimental results. Based on the analysis above, an Optimized CBLE (O-CBLE) structure was used to optimize the bird strike resistant ability, the energy absorption rate of O-CBLE structure increased 11.4% while the structural quality was only slightly increased.

Vertical Riser VIV Simulation in Uniform Current

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Kevin Huang ◽  
Hamn-Ching Chen ◽  
Chia-Rong Chen
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Method ◽  
Cross Flow ◽  
Experimental Results ◽  
Critical Parameters ◽  
Outer Diameter ◽  
Higher Harmonics ◽  
Uniform Current ◽  
Simulation Results

Recently, some riser vortex-induced vibrations (VIVs) experimental data have been made publicly available (oe.mit.edu/VIV/) including a 10 m riser VIV experiment performed by Marintek, Trondheim, Norway, and donated by ExxonMobil URC, Houston, TX, USA. This paper presents our numerical simulation results for this 10 m riser and the comparisons with the experimental results in uniform current. The riser was made of a 10 m brass pipe with an outer diameter of 0.02 m (L/D=482) and a mass ratio of 1.75. The riser was positioned vertically with top tension of 817 N and pinned at its two ends to the test rig. Rotating the rig in the wave tank would simulate the uniform current. In the present numerical simulation the riser’s ends were pinned to the ground and a uniform far field incoming current was imposed. The riser and its surrounding fluid were discretized using 1.5×106 elements. The flow field is solved using an unsteady Reynolds-averaged Navier–Stokes (RANS) numerical method in conjunction with a chimera domain decomposition approach with overset grids. The riser is also discretized into 250 segments. Its motion is predicted through a tensioned beam motion equation with external force obtained by integrating viscous and pressure loads on the riser surface. Then the critical parameters including riser VIV amplitude (a) to the riser outer diameter (D) ratio (a/D), vorticity contours, and motion trajectories were processed. The same parameters for the experimental data were also processed since these data sets are in “raw time-histories” format. Finally, comparisons are made and conclusions are drawn. The present numerical method predicts similar dominant modes and amplitudes as the experiment. It is also shown that the cross flow VIV in the riser top section is not symmetric to that of the bottom section. One end has considerably higher cross flow vibrations than the other end, which is due to the nondominant modal vibrations in both in-line and cross flow directions. The computational fluid dynamics (CFD) simulation results also agree with the experimental results very well on the riser vibrating pattern and higher harmonics response. The higher harmonics were studied and it is found that they are related to the lift coefficients, hence the vortex shedding patterns. It is concluded that the present CFD approach is able to provide reasonable results and is suitable for 3D riser VIV analysis in deepwater and complex current conditions.

A Novel Method to Decrease Electric Field and SAR Using an External High Dielectric Sleeve at 3T Head MRI: Numerical and Experimental Results

2013 ◽  
Author(s):  
Bu S. Park ◽  
Joshua W. Guag ◽  
Leonardo M. Angelone ◽  
Sunder S. Rajan
Keyword(s):  
Numerical Simulation ◽  
Electric Field ◽  
Dielectric Materials ◽  
Boundary Region ◽  
Experimental Results ◽  
Head Model ◽  
Rf Coil ◽  
Mri Imaging ◽  
Simulation Results ◽  
High Dielectric

We present experimental and numerical simulation results showing that high dielectric materials (HDMs) located outside of a RF head coil decrease the electric field (E-field, |E|) with minimum change of the RF magnetic field (B1+) at 3T MRI imaging. Compared to previous research using HDMs located between the RF coil and sample, our method locating the HDM outside the coil allowed an increased sample size and more flexibility of HDM thickness optimization. Numerical simulation results showed more than 30% decrease in the local SAR at the boundary region of the head model. Validating experimental results showed a 21% decrease in the maximum |Etotal| using a HDM made of distilled water.

Numerical Simulation of Flow Field around DLR_F4 Using Meshless Method

2013 ◽  
Vol 681 ◽  
pp. 209-213
Author(s):  
Xin Jian Ma ◽  
Jun Jie Tan ◽  
Deng Feng Ren ◽  
Fang Wang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Turbulence Model ◽  
Meshless Method ◽  
Experimental Results ◽  
Fluid Viscosity ◽  
Force Coefficient ◽  
Simulation Results ◽  
Lift And Drag ◽  
Present Simulation

In order to investigate the calculation ability of meshless method and calculation precision for lift and drag force coefficient based on N-S equations with S-A turbulence model and Euler equations, numerical simulation of flow field around the DLR-F4 wing-body, supplied by the AIAA Drag Prediction Workshop, is employed using meshless method. Furthermore, the calculated results are compared with experiment results and Waller’s simulation results achieved by MGAERO software. It’s found that the present simulation results without consideration of fluid viscosity don’t agree well with Waller’s and experimental results. The present simulation results with consideration of fluid viscosity were found to be in good agreement with experimental results. These results indicate that meshless method coupled with S-A turbulence model could predict the natural flow characteristic around the DLR-F4 wing-body configuration well.

scholarly journals Особенности согласования нижнего электрода с высокочастотным генератором смещения при реактивно-ионном травлении массивных подложек

2021 ◽  
Vol 91 (4) ◽  
pp. 657
Author(s):  
С.Д. Полетаев ◽  
А.И. Любимов
Keyword(s):  
Numerical Simulation ◽  
Reactive Ion Etching ◽  
Experimental Results ◽  
Substrate Holder ◽  
Rf Power ◽  
Special Design ◽  
Reactive Component ◽  
Lower Electrode ◽  
Ion Etching ◽  
Simulation Results

This paper presents theoretical and experimental results on reactive ion etching of massive substrates in freon-14 with RF bias at the lower electrode. A hypothesis is proposed according to which a large-sized substrate violates the matching of the lower electrode with the RF generator by adding an additional reactive component to the impedance of the lower electrode. A numerical simulation of reactive ion etching with substrates of various sizes in a CF4 environment is performed . The simulation results showed a significant increase in the reactive component of RF power at the lower electrode if the substrate area exceeds 50% of the area of the lower electrode, which is consistent with the proposed hypothesis. It has been experimentally shown that the etching of massive substrates violates the matching of the lower electrode with the RF generator. A special design of the substrate holder for massive substrates has been developed. It is shown that such a substrate holder significantly improves the matching of the RF generator with the lower electrode, especially when adding 0.3-0.9 l/h argon to the plasma-forming mixture.

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