Experimental measurement of energy density of a vibrating beam

2016 ◽  
Vol 24 (24) ◽  
pp. 5735-5746 ◽  
Author(s):  
A Nokhbatolfoghahai ◽  
HM Navazi ◽  
Y Ghobaad ◽  
H Haddadpour
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Energy Density ◽  
Potential Energy ◽  
Vibrational Energy ◽  
Random Force ◽  
Measurement Procedure ◽  
Element Analysis ◽  
The Difference ◽  
Energy Finite Element Analysis

This paper presents a method for calculating vibrational energy density from experimental data in a uniform beam. The input excitation is a point random force that induces transverse vibration along the beam. Using finite difference method and four accelerometers, both translational and rotational terms of kinetic and potential energy densities are measured. Also, an energy finite element analysis based computer program is developed. The results of the measurements achieved by developed formulation are compared with those of energy finite element analysis results. It is found that there is a fair agreement between them at relatively lower frequencies. But, in high frequencies, the difference between analytical and experimental results increases which stems from occurrence of errors in calculation of potential energy density. Finally, a comparison between kinetic and potential terms of the energy density is done. It is concluded that an efficient and very simple measurement procedure can be used based on kinetic energy measurement only.

Development of Energy Finite Element Analysis in Vibration Analysis of Composite Laminate Plate Structures

2013 ◽  
Vol 470 ◽  
pp. 1020-1023
Author(s):  
Yang Yang ◽  
Xi Liang Chen ◽  
Wen Wu Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Energy Density ◽  
Vibration Analysis ◽  
Composite Laminate ◽  
Laminate Plate ◽  
Element Analysis ◽  
Plate Structure ◽  
Composite Laminate Plate ◽  
Energy Finite Element Analysis

The high frequency vibration analysis of a composite laminate plate structure subjected to impact loads was investigated by using method of energy finite element analysis (EFEA). The time and space averaged energy density was used as the primary variable to form the governing differential equations. The multilayer laminate plate is simplified to be equivalent isotropic plate using the average concept, such as the average damping loss factor and the average group speed. The global system of EFEA equations can be solved numerically and the energy density distribution within the whole system can then be obtained. The EFEA numerical results for composite laminate plate structure were validated through comparison with those of very dense conventional finite element analysis (FEA).

A Comparative Study on Mechanical Behavior of Pipe-Socket Threaded Joints With Taper-Taper Threads and Taper-Parallel Threads Combinations by Finite Element Analysis and Experiments

2018 ◽  
Author(s):  
Satoshi Nagata ◽  
Shinichi Fujita ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Service Condition ◽  
Internal Thread ◽  
Element Analysis ◽  
Strain Pattern ◽  
External Thread ◽  
Thread Length ◽  
The Difference

There are two types of combination between external and internal threads used in threaded pipe connections for pressure piping specified in industrial standards like JIS as well as ISO. One is the combination that taper external thread of pipe is engaged with taper internal thread of a fitting. The other is that taper external thread of pipe is engaged with parallel internal thread of a fitting. Taper thread is always used for external thread outside the pipe wall. Both taper thread and parallel one are applicable to internal thread inside the fittings. This paper evaluates the mechanical behaviors of threaded pipe-socket joints (or pipe-coupling joints) and the difference due to the thread type combinations by means of axisymmetric finite element analysis for 3/4” and 3” joints. The analysis shows that the taper-taper threads combination establishes the full-length contact over the engaged threads but the taper-parallel has only a pair of threads in contact at the 1st engaged thread from the end of socket, and the difference results in the different behaviors of the joints. Stress and strain pattern also completely differ due to the difference in the engaged thread length. No significant effect of the size has been found in the present analysis for 3/4”and 3” joints. Experimental tightening tests and pressure leak tests have also been carried out for 3/4” and 3” joints with taper-taper threads combination. The measured experimental stress for 3/4” joints has shown an agreement with the simulated one fairly well. The pressure leak tests have demonstrated that the taper-taper threaded pipe-socket joints can hold internal pressure without leakage without using thread seal tape or jointing compound under low-pressure service condition. The 3/4” joints have started leaking at 1–4MPaG of internal pressure. The 3” joints haven’t shown leakage even at 6MPaG of internal pressure applied.

Applying Incompatible Meshes for Modeling Structural-Acoustic Domains in Energy Finite Element Analysis

2014 ◽  
Author(s):  
S. N. Medyanik ◽  
N. Vlahopoulos
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Differential Equations ◽  
Computationally Efficient ◽  
Exact Matching ◽  
Element Analysis ◽  
Energy Finite Element Analysis ◽  
Accuracy Of Results ◽  
New Formulation ◽  
Acoustic Interface

The Energy Finite Element Analysis (EFEA) has been developed for modeling coupled structural-acoustic systems at mid-to-high frequencies when conventional finite element methods are no longer computationally efficient because they require very fine meshes. In standard Finite Element Analysis (FEA) approach, governing differential equations are formulated in terms of displacements which vary harmonically with space. This requires larger numbers of elements at higher frequencies when wavelengths become smaller. In the EFEA, governing differential equations are formulated in terms of energy density that is spatially averaged over a wavelength and time averaged over a period. The resulting solutions vary exponentially with space which makes them smooth and allows for using much coarser meshes. However, current EFEA formulations require exact matching between the meshes at the boundaries between structural and acoustic domains. This creates practical inconveniences in applying the method as well as limits its use to only fully compatible meshes. In this paper, a new formulation is presented that allows for using incompatible meshes in EFEA modeling, when shapes and/or sizes of elements at structural-acoustic interfaces do not match. In the main EFEA procedure, joints formulations between structural and acoustic domains have been changed in order to deal with non-matching elements. In addition, the new Pre-EFEA procedure which allows for automatic searching and formation of the new types of joints is developed for models with incompatible meshes. The new method is tested using a spherical shaped structural-acoustic interface. Results for incompatible meshes are validated by comparing to solutions obtained using regular compatible meshes. The effects of mesh incompatibility on the accuracy of results are discussed.

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