scholarly journals Research on the Manufacturing Quality of Co-Cured Hat-Stiffened Composite Structure

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2747
Author(s):  
Xiangwen Ju ◽  
Jun Xiao ◽  
Dongli Wang ◽  
Cong Zhao ◽  
Xianfeng Wang
Keyword(s):  
Composite Structures ◽  
Sound Pressure ◽  
Integration Method ◽  
Complex Geometry ◽  
Sound Field ◽  
Thickness Measurement ◽  
Curing Process ◽  
The Finite Element Method ◽  
Manufacturing Quality

The stringer-stiffened structure is widely used due to its excellent mechanical properties. Improving the manufacturing quality of stringer-stiffened structure which have complex geometry is important to ensure the bearing capacity of aviation components. Herein, composite hat-stiffened composite structures were manufactured by different filling forms and bladders with various properties, the deformation of silicone rubber bladder in co-curing process was studied by using the finite element method. The thickness measurement at different positions of the hat-stiffened structure was performed to determine the best filling form and bladder property. Moreover, in view of the detection difficulties in R-zone of stringer, numerical simulation was performed to get the sound pressure and impulse response of at the R-zone of stringer by Rayleigh integration method, and an effective equipment which could stably detect the manufacturing quality of R-zone was designed to verify the correctness of sound field simulation and realize the detection of stringer. With the optimum filling form and bladder properties, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process.

Case study: Measurement and treatment of severe flutter echo caused by a barrel-vaulted sanctuary ceiling

2019 ◽  
Vol 67 (5) ◽  
pp. 380-393 ◽  
Author(s):  
Heather L. Lai ◽  
Anne C. Balant ◽  
David Foote
Keyword(s):  
Impulse Response ◽  
Sound Pressure ◽  
Sound Field ◽  
Pressure Level ◽  
Reverberation Time ◽  
Frequency Range ◽  
Recommended Treatment ◽  
Before And After

This case study centers on a recently constructed church with a barrel-vaulted sanctuary ceiling exhibiting excessive reverberation times and flutter echo. Reverberation times in excess of 5 s in the speech frequency range were observed at locations along the tiled center aisle, along with correspondingly elevated sound pressure levels and a highly non-diffuse sound field. Preliminary measurements, which included covering the reflective center aisle, substantiated the hypothesis that the acoustical behavior was caused by the interaction between the center aisle and the barrel-vaulted ceiling. The proposed recommendations for retrofitting the space to improve intelligibility along the aisle were modified with a view toward attaining an acceptable reduction in the reverberation times while retaining the spacious acoustical quality of the sanctuary. Additional acoustical measurements were performed prior to and following the completion of the recommended treatment. This case study describes the series of measurements and presents results of the treatment, in terms of reverberation time, impulse response decay curves, impulse response time waveforms and spectrograms, and sound pressure level measures. The unique characteristics of flutter echo due to the barrel-vaulted ceiling before and after the successful acoustical treatment are described.

Towards Predicting Relative Belt Edge Endurance With the Finite Element Method

1990 ◽  
Vol 18 (4) ◽  
pp. 216-235 ◽  
Author(s):  
J. De Eskinazi ◽  
K. Ishihara ◽  
H. Volk ◽  
T. C. Warholic
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Shear Deformations ◽  
Element Analysis ◽  
Vertical Loading ◽  
Predicted Values ◽  
Element Method

Abstract The paper describes the intention of the authors to determine whether it is possible to predict relative belt edge endurance for radial passenger car tires using the finite element method. Three groups of tires with different belt edge configurations were tested on a fleet test in an attempt to validate predictions from the finite element results. A two-dimensional, axisymmetric finite element analysis was first used to determine if the results from such an analysis, with emphasis on the shear deformations between the belts, could be used to predict a relative ranking for belt edge endurance. It is shown that such an analysis can lead to erroneous conclusions. A three-dimensional analysis in which tires are modeled under free rotation and static vertical loading was performed next. This approach resulted in an improvement in the quality of the correlations. The differences in the predicted values of various stress analysis parameters for the three belt edge configurations are studied and their implication on predicting belt edge endurance is discussed.

Active control of the scattered radiation with a reflecting surface

2019 ◽  
Vol 67 (3) ◽  
pp. 190-196
Author(s):  
Ning Han
Keyword(s):  
Control System ◽  
Active Control ◽  
Scattered Radiation ◽  
Sound Pressure ◽  
Sound Field ◽  
Control Area ◽  
Mirror Image ◽  
Three Dimension ◽  
Control Effect ◽  
Reflecting Surface

Based on a prediction method of the scattered sound pressure, an active control system was proposed in previous work for the three-dimension scattered radiation, where all the relevant simulations and experiments were implemented in three-dimensional free sound field. However, for practical applications, such as the anti-eavesdropping system or the stealth system for submarines, the sound field conditions are usually complex, and the most common case is the one with reflecting surface. It is questionable whether the previous control system is still effective in non-free sound field, or what improvements should be operated to ensure the control effect. In this article, based on the mirror image principle, two methods of calculating the control source strengths are proposed for the scattered radiation control, and numerical simulations with one-channel and multi-channel system are implemented to detect the corresponding control effect. It is seen that the local active control for the scattered radiation is still effective, and the reduction of the sound pressure level as well as the control area is extended with the increasement of the error sensors and control sources.

Numerical implementation of finite-element method of control volume using irregular mesh

2010 ◽  
Vol 7 ◽  
pp. 98-108
Author(s):  
Yu.A. Gafarova
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Delaunay Triangulation ◽  
Complex Geometry ◽  
Control Volume ◽  
Test Case ◽  
The Finite Element Method ◽  
Irregular Mesh ◽  
Discrete Analogues ◽  
Element Method

To solve problems with complex geometry it is considered the possibility of application of irregular mesh and the use of various numerical methods using them. Discrete analogues of the Beltrami-Mitchell equations are obtained by the control volume method using the rectangular grid and the finite element method of control volume using the Delaunay triangulation. The efficiency of using the Delaunay triangulation, Voronoi diagrams and the finite element method of control volume in a test case is demonstrated.

Smoothed particle hydrodynamics versus finite element method for blast impact

2013 ◽  
Vol 61 (1) ◽  
pp. 111-121 ◽  
Author(s):  
T. Jankowiak ◽  
T. Łodygowski
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Smoothed Particle Hydrodynamics ◽  
Concrete Slab ◽  
The Finite Element Method ◽  
Particle Hydrodynamics ◽  
Mesh Density ◽  
Smoothed Particle ◽  
Element Method

Abstract The paper considers the failure study of concrete structures loaded by the pressure wave due to detonation of an explosive material. In the paper two numerical methods are used and their efficiency and accuracy are compared. There are the Smoothed Particle Hydrodynamics (SPH) and the Finite Element Method (FEM). The numerical examples take into account the dynamic behaviour of concrete slab or a structure composed of two concrete slabs subjected to the blast impact coming from one side. The influence of reinforcement in the slab (1, 2 or 3 layers) is also presented and compared with a pure concrete one. The influence of mesh density for FEM and the influence of important parameters in SPH like a smoothing length or a particle distance on the quality of the results are discussed in the paper

scholarly journals Mathematical modeling and experimental study on solid–liquid suspension separation in ultrasonic standing wave field

2021 ◽  
pp. 146134842110229
Author(s):  
Yajing Wang ◽  
Liqun Wu ◽  
Yaxing Wang ◽  
Yafei Fan
Keyword(s):  
Standing Wave ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Sound Field ◽  
Radiation Force ◽  
High Energy ◽  
Factors Affecting ◽  
Liquid Suspension ◽  
Ultrasonic Standing Wave ◽  
Solid Liquid

A new method of removing waste chips is proposed by focusing on the key factors affecting the processing quality and efficiency of high energy beams. Firstly, a mathematical model has been established to provide the theoretical basis for the separation of solid–liquid suspension under ultrasonic standing wave. Secondly, the distribution of sound field with and without droplet has been simulated. Thirdly, the deformation and movement of droplets are simulated and tested. It is found that the sound pressure around the droplet is greater than the sound pressure in the droplet, which can promote the separation of droplets and provide theoretical support for the ultrasonic suspension separation of droplet; under the interaction of acoustic radiation force, surface tension, adhesion, and static pressure, the droplet is deformed so that the gas fluid around the droplet is concentrated in the center to achieve droplet separation, and the droplet just as a flat ball with a central sag is stably suspended in the acoustic wave node.

scholarly journals Field Investigation and Rapid Deterioration Analysis of Heavy Haul Corrugation

2021 ◽  
Vol 11 (14) ◽  
pp. 6317
Author(s):  
Feng Jin ◽  
Hong Xiao ◽  
Mahantesh M Nadakatti ◽  
Huiting Yue ◽  
Wanting Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Cracks ◽  
Field Measurements ◽  
Field Investigation ◽  
The Finite Element Method ◽  
Rail Corrugation ◽  
Rapid Deterioration ◽  
Heavy Haul

In this study, the rapid growth of corrugation caused by the bad quality of grinding works and their wavelength, depth, and evolution processes are captured through field measurements. The residual grinding marks left by poor grinding quality lead to further crack accumulation and corrugation deterioration by decreasing plastic resistance in rails. In this case, the average peak-to-peak values of corrugation grow extremely fast, reaching 1.4 μm per day. The finite element method (FEM) and fracture mechanics methodologies were used to analyze the development and trends in rail surface crack deterioration by considering rails with and without grinding marks. Crack propagation trends increase with residual grinding marks, and they are more severe in circular curve lines. To avoid the rapid deterioration of rail corrugation, intersections between grinding marks and fatigue cracks should be avoided.

scholarly journals Noise at the time of COVID 19: The impact in some areas in Rome and Milan, Italy

Noise Mapping ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 248-264
Author(s):  
Rosa Maria Alsina Pagès ◽  
Francesc Alías ◽  
Patrizia Bellucci ◽  
Pier Paolo Cartolano ◽  
Ilaria Coppa ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Traffic Noise ◽  
Motor Vehicles ◽  
Acoustic Environment ◽  
Commercial Activities ◽  
Real Time Traffic ◽  
Italian Regions ◽  
Almost All ◽  
The Impact

AbstractThe COVID-19 pandemic was confirmed in Italy at the end of January 2020, when the first positive cases for the virus were identified. At the beginning of March, the virus had spread to all Italian regions and on 10 March 2020 the lockdown phase began, limiting the movement of people and prohibiting almost all commercial activities, businesses and non-essential industries. As a result, millions of people were forced to stay at home, causing a drastic drop in traffic volume, which significantly changed the acoustic environment and air quality of cities. On 4 May 2020, the lockdown was partially lifted and activities were progressively reopened. Therefore, traffic gradually started to increase and, consequently, the noise emitted by motor vehicles. This behaviour was confirmed by the data collected by the DYNAMAP system, an automatic platform developed within the LIFE DYNAMAP project, providing real time traffic noise maps in terms of sound pressure levels and impacts at receivers (people and dwellings exposed to noise level bands). In this paper traffic and non-traffic-related noise events in the cities of Rome and Milan from March to May 2020 are analysed and compared to the corresponding values in 2019 to evaluate the effects of the lockdown period.

scholarly journals Analysis of Composite Structures in Curing Process for Shape Deformations and Shear Stress: Basis for Advanced Optimization

2021 ◽  
Vol 5 (2) ◽  
pp. 63
Author(s):  
Niraj Kumbhare ◽  
Reza Moheimani ◽  
Hamid Dalir
Keyword(s):  
Composite Structures ◽  
Latin Hypercube Sampling ◽  
Vital Role ◽  
Optimization Techniques ◽  
Design Parameters ◽  
Curing Process ◽  
Input Variables ◽  
Transient Thermal ◽  
Prototype Design ◽  
Shape Deformations

Identifying residual stresses and the distortions in composite structures during the curing process plays a vital role in coming up with necessary compensations in the dimensions of mold or prototypes and having precise and optimized parts for the manufacturing and assembly of composite structures. This paper presents an investigation into process-induced shape deformations in composite parts and structures, as well as a comparison of the analysis results to finalize design parameters with a minimum of deformation. A Latin hypercube sampling (LHS) method was used to generate the required random points of the input variables. These variables were then executed with the Ansys Composite Cure Simulation (ACCS) tool, which is an advanced tool used to find stress and distortion values using a three-step analysis, including Ansys Composite PrepPost, transient thermal analysis, and static structural analysis. The deformation results were further utilized to find an optimum design to manufacture a complex composite structure with the compensated dimensions. The simulation results of the ACCS tool are expected to be used by common optimization techniques to finalize a prototype design so that it can reduce common manufacturing errors like warpage, spring-in, and distortion.

Study on Sound Field of High Intensity Focused Ultrasound with Short Focal Length

2012 ◽  
Vol 195-196 ◽  
pp. 364-369 ◽  
Author(s):  
Jin Hua Zhao ◽  
Li Li Yu ◽  
Chun Hui ◽  
Bin Feng Huang ◽  
Chao Li ◽  
...  
Keyword(s):  
Nonlinear Effect ◽  
Sound Pressure ◽  
Focal Length ◽  
Sound Field ◽  
High Intensity Focused Ultrasound ◽  
Beam Equation ◽  
Focal Region ◽  
Interface Position ◽  
Short Focal Length ◽  
Planar Wave

In this paper, numerical simulation of sound field with short focal length is performed, which is based on spheroidal beam equation (SBE) in frequency-domain for transducer with a wide aperture angle. And we made some experiments on vitro bovine liver to explore the characteristic of sound pressure and-3dB sound focal region at different positions of incident interface. It is found that with a fixed curvature radius if the focal length is shorter under the skin, the amplitude of sound pressure will be higher on the focus and the shape of-3dB sound focal region will be smaller. When the incident interface is in the range of planar wave, nonlinear effect is strong and the focus will change with the interface position. Especially when the position is near to transition location between planar wave and spheroidal wave, the nonlinear effect is lowered. While the focus is closer to the sound source so as to burn the scarfskin easily. When the interface is in the range of spheroidal wave, the focus position changes little but the side lobe effect due to refraction is obvious. And the focusing performance of transducer will be affected. The experimental results validate the accuracy of theoretical results. It is concluded that the position of incident interface should be selected reasonably with short focal length in the treatment of superficial tissue.

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