Simulation and experiment analysis of relationship between voids and permeability of composites

2021 ◽  
pp. 146442072110269
Author(s):  
Chenglong Guan ◽  
Lihua Zhan ◽  
Hanqiao Shi ◽  
Guangming Dai ◽  
Yu Xiao
Keyword(s):  
Low Temperature ◽  
Random Medium ◽  
Engineering Application ◽  
Permeation Rate ◽  
Theoretical Research ◽  
Element Analysis ◽  
Medium Theory ◽  
Technical Problems ◽  
Morphology Model ◽  
Curing Pressure

Due to the significant weight reduction advantage, aerospace composite tanks have become the focus of international competition of spacecraft. However, the permeation of small molecules at low temperature caused by the internal voids of composites is one of the key technical problems which restrict the engineering application of composite tanks. In this study, a combination of theoretical research and experimental research was adopted. By changing the curing pressures of the composites’ autoclave process, laminates with different porosities were prepared and tested for low-temperature permeability. Based on the grayscale processing and median filtering methods, a permeability prediction model with the true voids morphology of composite materials was established. Based on the random medium theory, the random voids model of composites was built to study the effect of void size and shape on the permeability of laminates. The results showed that the finite element analysis of composites, permeability based on the real voids morphology model was in good agreement with the experimental results, which proved the feasibility of this method. The permeation rate of laminates increased with the raised of porosity, and the internal porosity of the laminates could be diminished by improving the curing pressure so as to reduce the permeation of the composite components. Under the condition of a certain porosity, the laminates with small, stripe voids had a higher permeation rate than the laminates with large, circular voids.

Separation of Primary Stress in Finite Element Analysis of Pressure Vessel with the Principle of Superposition

2007 ◽  
Vol 353-358 ◽  
pp. 373-376 ◽  
Author(s):  
Bing Jun Gao ◽  
Xiao Ping Shi ◽  
Hong Yan Liu ◽  
Jin Hong Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Engineering Application ◽  
Total Stress ◽  
Principle Of Superposition ◽  
Element Analysis ◽  
Primary Stress ◽  
The Finite Element Analysis ◽  
Asme Code ◽  
Allowable Load

A key problem in engineering application of “design by analysis” approach is how to decompose a total stress field obtained by the finite element analysis into different stress categories defined in the ASME Code III and VIII-2. In this paper, we suggested an approach to separate primary stress with the principle of superposition, in which the structure does not need to be cut into primary structure but analyzed as a whole only with decomposed load. Taking pressurized cylindrical vessel with plate head as example, the approach is demonstrated and discussed in detail. The allowable load determined by the supposed method is a little conservative than that determined by limited load analysis.

On real-time creep damage prediction for steam turbine

2022 ◽  
pp. 014233122110689
Author(s):  
Yongjian Sun ◽  
Bo Xu
Keyword(s):  
Finite Element ◽  
Steam Turbine ◽  
Real Time ◽  
Creep Damage ◽  
Element Model ◽  
Turbine Rotor ◽  
Theoretical Research ◽  
Element Analysis ◽  
Damage Prediction ◽  
Time Calculation

In this paper, in order to solve the calculation problem of creep damage of steam turbine rotor, a real-time calculation method based on finite element model is proposed. The temperature field and stress field of the turbine rotor are calculated using finite element analysis software. The temperature data and stress data of the crucial positions are extracted. The data of temperature, pressure, rotational speed, and stress relating to creep damage calculation are normalized. A real-time creep stress calculation model is established by multiple regression method. After that, the relation between stress and damage function is analyzed and fitted, and creep damage is calculated in real-time. A creep damage real-time calculation system is constructed for practical turbine engineering. Finally, a numerical simulation experiment is designed and carried out to verify the effectiveness of this novel approach. Contributions of present work are that a practical solution for real-time creep damage prediction of steam turbine is supplied. It relates the real-time creep damage prediction to process parameters of steam turbine, and it bridges the gap between the theoretical research works and practical engineering.

Three-dimensional seismic structure of the lithosphere under Montana Lasa

1976 ◽  
Vol 66 (2) ◽  
pp. 501-524
Author(s):  
Keiiti Aki ◽  
Anders Christoffersson ◽  
Eystein S. Husebye
Keyword(s):  
Generalized Inverse ◽  
Random Medium ◽  
Three Dimensional ◽  
P Wave ◽  
Seismic Structure ◽  
Low Velocity ◽  
Medium Theory ◽  
Velocity Anomaly ◽  
Inversion Techniques ◽  
Teleseismic Events

abstract Using P-wave residuals for teleseismic events observed at the Montana Large Aperture Seismic Array (LASA), we have determined the three-dimensional seismic structure of the lithosphere under the array to a depth of 140 km. The root-mean-square velocity fluctuation was found to be at least 3.2 per cent which may be compared to estimate of ca. 2 per cent based on the Chernov random medium theory. The solutions are given by both the generalized inverse and stochastic inverse methods in order to demonstrate the relative merit of different inversion techniques. The most conspicuous feature of the lithosphere under LASA is a low-velocity anomaly in the central and northeast part of the array siting area with the N60°E trend and persisting from the upper crust to depths greater than 100 km. We interpret this low-velocity anomaly as a zone of weakness caused by faulting and shearing associated with the building of the Rocky Mountains.

scholarly journals Estimation of fastener pull-through resistance of composite laminates based on generalized regression neural network

2020 ◽  
Vol 29 ◽  
pp. 2633366X2096884
Author(s):  
Sheng Mingjian ◽  
Chen Puhui ◽  
Chen Cheng
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Composite Laminates ◽  
Engineering Application ◽  
Transverse Load ◽  
Generalized Regression Neural Network ◽  
Element Analysis ◽  
Research Attention ◽  
Generalized Regression ◽  
Pull Through

The fastener pull-through resistance is a key performance index of composite laminates used for engineering application, and increasing research attention is being paid to developing methods for its calculation or estimation. The currently available research methods mainly focus on the standard test and the finite element analysis for determining the pull-through resistance of composite laminates suffering transverse load by the fasteners. Based on the results of the fastener pull-through resistance experiment performed on X850 composite laminates, a model for estimating the maximum affordable load of composite laminates for the fastener pull-through resistance is proposed, using generalized regression neural network technology. The inputs of this model are simplified to six parameters: the proportion of the ±45° layer of the laminates, the number of the layers, the thickness of the laminates, the bolt head shape, whether the bolt has a washer or not, and the nominal diameter of the bolt; the Gauss function is used as the hidden layer function. The model uses a large portion of the experimental data to train for finding the optimal smoothness factor, which is used to reconstruct the model, and simulation is performed with the remainder of the experimental data. The comparison between the estimated results using the model and the experimental results shows that the generalization ability of the proposed model can meet the estimation requirements. Moreover, the pull-through resistance of composite laminates under transverse load from a fastener can be estimated with high accuracy after some standard fastener pull-through resistance tests of the composite laminates.

Theoretical Analysis and Engineering Improvement Test Verification of the Crack Problem in the Back Van of the Vehicle

2011 ◽  
Vol 121-126 ◽  
pp. 3431-3436
Author(s):  
Guo Quan Yang ◽  
You Qun Zhao ◽  
Jun Yan Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Theoretical Analysis ◽  
Crack Problem ◽  
Engineering Application ◽  
Reference Value ◽  
Element Analysis ◽  
Crack Problems ◽  
The Finite Element Analysis ◽  
Test Verification

This paper discussed the theoretical analysis and engineering improvement test verification of the crack problem in the back van of the vehicle. Causes that may result in the crack problem are firstly analyzed and then determined by the finite element analysis. Improvement are given and proved to be effective by the test verification of an improved vehicle. The method used in this paper will contribute to the analysis and solution of the crack problems in some parts of the vehicle and has reference value in engineering application.

Finite Element Simulating of C/SiC Composite Bolt

2012 ◽  
Vol 268-270 ◽  
pp. 3-6
Author(s):  
Tao Huang ◽  
Yi Yan Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Engineering Application ◽  
Contact Friction ◽  
Element Analysis ◽  
Valuable Data ◽  
The Finite Element Analysis ◽  
Sic Composites

A numerical investigation was conducted to determine the mechanical behavior of C/SiC composites bolt under room temperature and elevated temperature. The influence of the contact friction coefficient on the stress and displacement was considered in the finite element analysis. The FEA results provided some valuable data for the engineering application of C/SiC composites bolt.

Finite Element Analysis and Experimental Studies on the Thickness Resonance of Piezocomposite Transducers

1996 ◽  
Vol 18 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Wenkang Qi ◽  
Wenwu Cao
Keyword(s):  
Finite Element ◽  
Resonance Frequency ◽  
Electromechanical Coupling ◽  
Effective Medium Theory ◽  
Experimental Studies ◽  
Effective Medium ◽  
Electromechanical Coupling Coefficient ◽  
Element Analysis ◽  
Medium Theory ◽  
Resonance Frequencies

Finite element method (FEA) has been used to calculate the thickness resonance frequency and electromechanical coupling coefficient kt for 2–2 piezocomposite transducers. The results are compared with that of the effective medium theory and also verified by experiments. It is shown that the predicted resonance frequencies from the effective medium theory and the unit cell modeling using FEA deviate from the experimental observations for composite systems with a ceramic aspect ratio (width/length) more than 0.4. For such systems, full size FEA modeling is required which can provide accurate predictions of the resonance frequency and thickness coupling constant kt.

The Cleaning Performance Simulation of Rear Rolling Type Sweeper

2013 ◽  
Vol 385-386 ◽  
pp. 281-287
Author(s):  
Zhi Qiang Wang ◽  
Xue Liang Bian ◽  
You Ning Feng
Keyword(s):  
Theoretical Model ◽  
Simulation Analysis ◽  
Virtual Prototype ◽  
Ideal Theory ◽  
Contact Dynamics ◽  
Theoretical Research ◽  
Prototype Model ◽  
Prototype System ◽  
Working Process ◽  
Element Analysis

Through analyzed the cleaning process of rear rolling type sweeper, the theoretical model of waste particle trajectory was established during the sweeper working process by using the contact theory of modern contact dynamics, and the ideal theory track of waste particle was simulated and optimized by using MATLAB. The three-dimensional solid model of the working device was created by using UG software, and virtual prototype model was completed by using ADAMS software, and rigid brush was replaced by neutral file with brush features characterize that was generated by finite element analysis software, and contact relationship of waste particle during the working process was added by ADAMS contact order, and rigid-flexible coupling virtual prototype system was completed and kinematics simulation was run. Finally, compared the trajectory curve from ADAMS simulation with the theoretical path from MATLAB, the Theoretical model was proved correctness. The theoretical research and simulation analysis was made test and verify each other. Facilitate the development of the same type of products.

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