scholarly journals An Improved Beam Element for Beams with Variable Axial Parameters

2013 ◽  
Vol 20 (4) ◽  
pp. 601-617 ◽  
Author(s):  
Peng He ◽  
Zhansheng Liu ◽  
Chun Li
Keyword(s):  
Temperature Distribution ◽  
Power Series ◽  
Temperature Difference ◽  
Natural Frequencies ◽  
Beam Element ◽  
Elementary Matrix ◽  
Beam Elements ◽  
Stiffness Matrices ◽  
Axial Temperature ◽  
Matrix Series

The traditional beam element was improved to consider the variable axial parameters. The variable axial parameters were formulated in terms of a power series, and the general forms of elementary mass and stiffness matrices which depend on the power order were derived. The mass and stiffness matrices of the improved beam element were obtained in terms of an elementary matrix series. The beam elements for various tapered beams and a beam under linearly axial temperature distribution were derived. The vibrations of the beams with various taper shapes were studied and the variations of natural frequencies and modal shapes were investigated. A uniform beam under linearly axial temperature distribution was modeled and studied. The influences of axial temperature difference on the natural frequencies and modal shapes were investigated. Results show that the improved beam element could consider the variable axial parameters of beam conveniently.

Comparative Study on Different National Standards for Local Post Weld Heat Treatment of Pressure Vessels

2020 ◽  
Author(s):  
Fang Ji ◽  
Guide Deng ◽  
Linlin Duan ◽  
Cenfan Liu ◽  
Xiaonan Zhao
Keyword(s):  
Heat Treatment ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Temperature Difference ◽  
Pressure Vessel ◽  
Post Weld Heat Treatment ◽  
National Standards ◽  
Butt Weld ◽  
Axial Temperature ◽  
Weld Heat

Abstract In order to eliminate these welding residual stress which produced in the process of pressure vessel manufacturing and assembling, post-weld heat treatment is required for the weld structure. The Large size and complex structure pressure vessel which cannot integral post-welding heat treatment always implement local post-welding heat treatment. The reasonable heated band and insulated band are particularly important in the procedures of local post-welding heat treatment to meet the requirements of pressure vessel heat treatment. The recommended heated band and insulated band are given in different national standards. But the recommended width of heated band and insulated band are different in different national standards. In the paper, numerical simulation was carried out to compare and study the difference of temperature distribution in the holding temperature period when post-welding heat treatment of pressure vessel barrel butt weld. The result show that the temperature distribution on sock band is very closed when the barrel butt weld implements post weld heat treatment with the heated and insulated band recommended in ASME BPVC-VIII-2017 and EN 13445-4:2014. The axial temperature gradient on sock band is very small and the temperature difference almost comes from the temperature difference through the thickness. Compared with this, the axial temperature gradient is larger and the temperature difference through thickness is smaller when post weld heat treatment with the max recommended heated and insulated band given in GB/T 30583-2014.

scholarly journals Influence of temperature distribution on circular saw blade natural frequencies during cutting

BioResources ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 1076-1090
Author(s):  
Miran Merhar
Keyword(s):  
Temperature Distribution ◽  
Temperature Difference ◽  
Natural Frequencies ◽  
Point Of View ◽  
Cutting Edge ◽  
Circular Saw ◽  
Rate Of Increase ◽  
Circular Saw Blade ◽  
Saw Blade ◽  
Experimental Findings

When cutting wood, heat is generated in the cutting zone and in the gullet due to the friction between the teeth of the blade and the material that is being cut. Since the wood is hydrophilic, the saw blade cannot be cooled with liquids, as is usual when cutting metals. The only way to remove the heat from the source is by conductivity to the centre of the saw blade and then by convection into the air. This research presents an analytical model to calculate the natural frequencies of circular saw blades exposed to different temperature distributions. The model confirmed experimental findings of many authors, i.e. the heating of the saw blade cutting edge reduces its natural frequencies, the rate of the reduction depending on the temperature difference between the cutting edge and the rest of the blade and on the shape of the temperature distribution. In contrast, heating the centre of the saw blade increases its natural frequencies, the rate of increase depending on the temperature difference and the shape of the temperature distribution. With the presented model, the most favourable temperature distribution can be calculated from the point of view of the critical saw blade speed, which can be achieved by heating or cooling the centre of the saw blade.

Isoparametric Timoshenko Elements for Dynamic Analysis of Structures and Mechanical Systems

1995 ◽  
Author(s):  
Ahmad Smaili ◽  
Ismail Bagci ◽  
Muhammad Sannah
Keyword(s):  
Exact Solution ◽  
Aspect Ratio ◽  
Cross Section ◽  
Natural Frequencies ◽  
Circular Tube ◽  
Shear Locking ◽  
Various Boundary Conditions ◽  
Beam Elements ◽  
Stiffness Matrices ◽  
Thin Beams

Abstract This paper presents 4-, 5-, 6- and 7-node isoparametric Timoshenko beam elements for modeling constant and varying cross-section thick and thin beams with various boundary conditions. Numerical integration is employed to determine the mass and stiffness matrices to facilitate modeling of varying cross-section beams. The accuracy of each proposed element is illustrated by determining the natural frequencies of: Thick and thin beams with constant and varying cross-section; linearly tapered cantilever circular tube with small wall thickness; chimney structure; and of a four-bar mechanism. In all examples, the results obtained using the proposed elements are compared, whenever available, with exact solution and with solutions determined when other elements available in the literature are used. The proposed elements did not cause shear locking when tested on thin beams of aspect ratio 500.

Identification of the string boundary conditions using natural frequencies

2016 ◽  
Vol 11 (1) ◽  
pp. 38-52
Author(s):  
I.M. Utyashev ◽  
A.M. Akhtyamov
Keyword(s):  
Inverse Problems ◽  
Power Series ◽  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Boundary Value ◽  
External Environment ◽  
Direct And Inverse Problems ◽  
Symmetric Potential ◽  
Modified Method

The paper discusses direct and inverse problems of oscillations of the string taking into account symmetrical characteristics of the external environment. In particular, we propose a modified method of finding natural frequencies using power series, and also the problem of identification of the boundary conditions type and parameters for the boundary value problem describing the vibrations of a string is solved. It is shown that to identify the form and parameters of the boundary conditions the two natural frequencies is enough in the case of a symmetric potential q(x). The estimation of the convergence of the proposed methods is done.

scholarly journals Stator Non-Uniform Radial Ventilation Design Methodology for a 15 MW Turbo-Synchronous Generator Based on Single Ventilation Duct Subsystem

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2760
Author(s):  
Ruiye Li ◽  
Peng Cheng ◽  
Hai Lan ◽  
Weili Li ◽  
David Gerada ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Design Methodology ◽  
Large Scale ◽  
Synchronous Generator ◽  
Axial Direction ◽  
Scale Model ◽  
Element Analysis ◽  
Axial Temperature ◽  
Ventilation Duct

Within large turboalternators, the excessive local temperatures and spatially distributed temperature differences can accelerate the deterioration of electrical insulation as well as lead to deformation of components, which may cause major machine malfunctions. In order to homogenise the stator axial temperature distribution whilst reducing the maximum stator temperature, this paper presents a novel non-uniform radial ventilation ducts design methodology. To reduce the huge computational costs resulting from the large-scale model, the stator is decomposed into several single ventilation duct subsystems (SVDSs) along the axial direction, with each SVDS connected in series with the medium of the air gap flow rate. The calculation of electromagnetic and thermal performances within SVDS are completed by finite element method (FEM) and computational fluid dynamics (CFD), respectively. To improve the optimization efficiency, the radial basis function neural network (RBFNN) model is employed to approximate the finite element analysis, while the novel isometric sampling method (ISM) is designed to trade off the cost and accuracy of the process. It is found that the proposed methodology can provide optimal design schemes of SVDS with uniform axial temperature distribution, and the needed computation cost is markedly reduced. Finally, results based on a 15 MW turboalternator show that the peak temperature can be reduced by 7.3 ∘C (6.4%). The proposed methodology can be applied for the design and optimisation of electromagnetic-thermal coupling of other electrical machines with long axial dimensions.

scholarly journals Influence of CFRC Insulating Plates on Spark Plasma Sintering Process

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 393
Author(s):  
Alexander M. Laptev ◽  
Jürgen Hennicke ◽  
Robert Ihl
Keyword(s):  
Temperature Distribution ◽  
Spark Plasma Sintering ◽  
Energy Demand ◽  
Composite Powders ◽  
Fem Method ◽  
Plasma Sintering ◽  
Axial Temperature ◽  
Spark Plasma ◽  
Power And Energy ◽  
The Impact

Spark Plasma Sintering (SPS) is a technology used for fast consolidation of metallic, ceramic, and composite powders. The upscaling of this technology requires a reduction in energy consumption and homogenization of temperature in compacts. The application of Carbon Fiber-Reinforced Carbon (CFRC) insulating plates between the sintering setup and the electrodes is frequently considered as a measure to attain these goals. However, the efficiency of such a practice remains largely unexplored so far. In the present paper, the impact of CFRC plates on required power, total sintering energy, and temperature distribution was investigated by experiments and by Finite Element Modeling (FEM). The study was performed at a temperature of 1000 °C with a graphite dummy mimicking an SPS setup. A rather moderate influence of CFRC plates on power and energy demand was found. Furthermore, the cooling stage becomes considerably longer. However, the application of CFRC plates leads to a significant reduction in the axial temperature gradient. The comparative analysis of experimental and modeling results showed the good capability of the FEM method for prediction of temperature distribution and required electric current. However, a discrepancy between measured and calculated voltage and power was found. This issue must be further investigated, considering the influence of AC harmonics in the DC field.

Analysis on Coupling of Laminated Elastic Beam Element and the Shock Pressure of Surrounding Rock of Roadway

2012 ◽  
Vol 505 ◽  
pp. 429-433
Author(s):  
Jin Wei ◽  
Zi Ming Kou ◽  
Wang Wang
Keyword(s):  
Characteristic Curve ◽  
Impact Resistance ◽  
Elastic Beam ◽  
Present Situation ◽  
Beam Element ◽  
Tunnel Support ◽  
Beam Elements ◽  
Mine Roadway ◽  
Safety Production ◽  
High Support

Based on the rock pressure tunnel support present situation carries on the analysis, the laminated elastic beams of high support ability and impact resistance was designed.Therefore, through assumptions and establishment of mathematical model, and the application of viscoelastic beam dynamics equation, deformation and energy absorption of the laminated elastic beam elements,under the condition of rock burst, was deduced. According to the load - displacement characteristic curve, the coupling of laminated elastic beam elements and rockburst in coal mine roadway was analysed. This can provide a new method in the field of safety production of mining and roadway.

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