Search results

1 – 5 of 5
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 1 April 2003

Tadej Kosel, Igor Grabec and Franc Kosel

In Part I, an intelligent acoustic emission (AE) locator is described while the Part II discusses a blind source separation, time delay estimation and location of two continuous…

438

Abstract

In Part I, an intelligent acoustic emission (AE) locator is described while the Part II discusses a blind source separation, time delay estimation and location of two continuous AE sources. AE analysis is used for characterization and location of developing defects in materials. AE sources often generate a mixture of various statistically independent signals. A difficult problem of AE analysis is a separation and characterization of signal components when the signals from various sources and the mode of mixing are unknown. Recently, blind source separation (BSS) by independent component analysis (ICA) has been used to solve these problems. The purpose of this paper is to demonstrate the applicability of ICA to locate two independent simultaneously active AE sources on an aluminum band specimen. The method is promising for non‐destructive testing of aircraft frame structures by AE analysis.

Details

Aircraft Engineering and Aerospace Technology, vol. 75 no. 2
Type: Research Article
ISSN: 0002-2667

Keywords

Access Restricted. View access options
Article
Publication date: 1 February 2002

Tadej Kosel and Igor Grabec

Acoustic emission analysis (AE) is used for characterization and location of developing defects in materials. AE sources often generate a mixture of various statistically…

432

Abstract

Acoustic emission analysis (AE) is used for characterization and location of developing defects in materials. AE sources often generate a mixture of various statistically independent signals. One difficult problem of AE analysis is the separation and characterization of signal components when the signals from various sources and the way in which the signals were mixed are unknown. Recently, blind source separation (BSS) by independent component analysis (ICA) has been used to solve these problems. The main purpose of this paper is to demonstrate the applicability of ICA to time‐delay estimation of two independent continuous AE sources on an aluminum beam. It is shown that it is possible to estimate time delays by ICA, and thus to locate two independent simultaneously emitted sources.

Details

Aircraft Engineering and Aerospace Technology, vol. 74 no. 1
Type: Research Article
ISSN: 0002-2667

Keywords

Access Restricted. View access options
Article
Publication date: 1 February 2003

Tadej Kosel, Igor Grabec and Franc Kosel

The intelligent acoustic emission (AE) locator is described in Part I while Part II discusses a blind source separation, time delay estimation and location of two simultaneously…

537

Abstract

The intelligent acoustic emission (AE) locator is described in Part I while Part II discusses a blind source separation, time delay estimation and location of two simultaneously active continuous AE sources. Location of AE on complicated aircraft frame structures is a difficult problem of non‐destructive testing. In this article an intelligent AE source locator is described. The intelligent locator is comprised of a sensor antenna and a general regression neural network, that solves the location problem based on learning from examples. The locator performance was tested on different test specimens. The tests have shown that accuracy of location depends on sound velocity and attenuation in the specimen, the dimensions of tested area, and properties of stored data. The location accuracy achieved by the intelligent locator is comparable to that obtained by the conventional triangulation method. This is a promising method for non‐destructive testing by AE method of aircraft frame structures.

Details

Aircraft Engineering and Aerospace Technology, vol. 75 no. 1
Type: Research Article
ISSN: 0002-2667

Keywords

Access Restricted. View access options
Article
Publication date: 25 February 2014

Goran Visnjic, Dejan Nožak, Franc Kosel and Tadej Kosel

The purpose of this paper was to investigate and evaluate the influence of geometrical and structural design changes in order to reduce shear-lag and increase specific strength…

567

Abstract

Purpose

The purpose of this paper was to investigate and evaluate the influence of geometrical and structural design changes in order to reduce shear-lag and increase specific strength and stiffness of thin-walled composite I-beam wing spars.

Design/methodology/approach

A detailed FEM model of a cantilevered I-beam spar was used to investigate the influence of increased transition fillet radius and increased web sandwich core thickness on the shear-lag effect at different width to thickness ratios of flanges. Evaluation functions were used to assess specific strength and stiffness of different spar configurations.

Findings

Increased web core thickness has greater influence on normal stress distribution and the reduction of the shear-lag than fillet size. Additional weight of thicker core is not compensated enough through reduction of stress concentration. Increased transition fillet and web core thickness increase optimum flanges width to thickness ratio. Shear-lag reduces the strength of the spar more than the stiffness of the spar.

Practical implications

Findings in this study and detailed insight in the shear-lag effect are important for aircraft design when minimum weight of the airframe is of supreme importance.

Originality/value

This combined shear-lag and weight optimization study deals with composite I-beams and loads that are specific for aerospace engineering. This study does not only evaluate the shear-lag phenomena, but primarily analyses fine structural details in order to reduce it, and increases specific strength and stiffness of I-beam spars.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 2
Type: Research Article
ISSN: 0002-2667

Keywords

Access Restricted. View access options
Article
Publication date: 22 May 2007

Viktor Šajn, Dejan Nožak, Tadej Kosel and Franc Kosel

This paper aims to present an algorithm for local mesh refinement of finite elements in a two‐dimensional compressible fluid flow.

534

Abstract

Purpose

This paper aims to present an algorithm for local mesh refinement of finite elements in a two‐dimensional compressible fluid flow.

Design/methodology/approach

The algorithm works on a principle of maximum gradient of fluid variables, e.g. pressure, velocity and density. The simulation of two‐dimensional, transient, viscous, compressible, adiabatic flow of turbulent fluid through a De Laval nozzle was performed by the finite element method. The pressure gradient was used as a condition for mesh refinement.

Findings

With the gradient method faster numerical calculations can be obtained. Boundary layer separation and locations of normal shock waves can be described on locally refined mesh.

Research limitations/implications

Further development of the algorithm is required, especially the determination of the gradient criterion.

Originality/value

The paper provides a new approach to mesh refinement. The mesh is refined automatically. Calculation time and required computer memory are decreased.

Details

Aircraft Engineering and Aerospace Technology, vol. 79 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

1 – 5 of 5
Per page
102050