Assessing material densities by vibration analysis and independent component analysis

Hajar Razaghi,Amaka Offiah,Reza Saatchi,Nick Bishop,Derek Burke,Santosh Gautam

doi:10.11113/mjfas.v9n3.96

Abstract

The aim of this study was to investigate vibration analysis and independent component analysis (ICA) to assess the density of multiple materials making up a single structure. Density is important as it reveals information about physical properties of materials. The density of a single material can be determined from the relationship between its mass and volume. However, when a structure consists of multiple materials, identification of their individual densities from the structure is complicated. Vibration analysis is a technique that reveals information about an object’s physical properties such as its density. The investigation was carried out using a plastic test tube filled separately with three liquids of known densities; water, Chloroform and Methanol. Vibration was inducted into the tube, through an electronic system that produced a single impact at a predefined location on the tube. The resulting vibration signals were recorded using two vibration sensors placed on the tube. A signal source separation technique called ICA was used to obtain the vibration effects of the liquid and the tube. The power spectral densities (PSD) of ICA extracted vibration signals were examined. The frequency of the largest peak in the PSD was related to the liquid’s density under test. The study indicated that vibration analysis may be effective in assessing materials’ densities in a structure that contains multiple materials, however a larger study is needed to explore the findings.

Highlights

The density of materials is an important feature of their physical properties
The results indicated that the approach could be successfully applied to vibration analysis
Vibration signals were recorded from a plastic laboratory test tube, when it was empty and when it was individually filled with three liquids of known densities(water, Chloroform and Methanol)

Summary

INTRODUCTION

The density of materials is an important feature of their physical properties. It is a measure of the amount of a material’s mass in relation to its volume. It can be continuous in nature, for example when a vibration motor is attached to the object under test In the former, the vibration of object decays with time and the decay rate is an important feature of the object’s physical properties. An issue that complicates vibration analysis is that when the object consists of multiple elements of different densities, these elements vibrate differently and the vibration signals recorded are a mixture of vibrations from each element in the structure. A well-known signal source separation technique is independent component analysis (ICA). Bell and Sejnowski [6] proposed an information-theoretic based ICA algorithm that uses an unsupervised learning rule It finds a linear transformation within the data to make the separated signal components as statistically 'independent' as possible.

INDEPENDENT COMPONENT ANALYSIS

RESULTS AND DISCUSSION

CONCLUSIONS