Abstract
This paper presents a brief summary of the research results of the application of experimental and operational modal analysis (EMA and OMA) effectiveness for the assessment of the change in the condition of operating structures by modifying their dynamic characteristics. Special focus is given to the topicality of the operational modal analysis for the definition of the dynamic features of the structures (frequencies, modes and deformation) under near-natural conditions. The research was conducted using two operating laboratory models, when the first one imitated a part of a fuel/gas pipeline and the second – a helicopter blade. The results of finite-element model simulation, identification of natural mode and the influence of the two types of virtual defects on the changes in the dynamic properties are provided. The work describes the results of experimental research of the dynamic behaviour of the pipe model, using the methods of OMA and comparing them with the modelling results. The research results demonstrate how the modification of the condition of the large-scaled models impacts pipe and blade models when the defects of local and global nature are introduced.
Highlights
Structural Health Monitoring (SMH) as a way of scientific and technical activity has been formed in the last third of the 20th century, uniting in itself data acquisition, computing, valuation and data analysis in order to control the technical condition of structures throughout their life cycle (Hall 1999)
2) the opportunity to receive the dynamic characteristics of the whole structure, not just its individual components; 3) model characteristics are linearised due to a wide range of accidental excitations; 4) all or some parts of the measured degree of freedom can be used for reference purposes, which significantly increases the method resolution and helps to segregate the paired and closely located modes; 5) the role of OMA is not limited to being a refining tool for structural improvements, it proved to be useful for the vibration-based health monitoring (Zhang et al 2005)
For the practical application of Modal Analysis methods it is necessary to identify the major natural modes; an experimental phase was preceded by mathematical modelling using the finite-element technique (FET)
Summary
Structural Health Monitoring (SMH) as a way of scientific and technical activity has been formed in the last third of the 20th century, uniting in itself data acquisition, computing, valuation and data analysis in order to control the technical condition of structures throughout their life cycle (Hall 1999). Since the beginning of the 90’s, Operational Modal Analysis (OMA), referred to as the analysis of output data or of natural excitation, has attracted attention with regards to big civilian objects, and later aviation This method only uses the response of the stressed structure excited by the surrounding environment for the valuation of modal features. 2) the opportunity to receive the dynamic characteristics of the whole structure, not just its individual components; 3) model characteristics are linearised due to a wide range of accidental excitations; 4) all or some parts of the measured degree of freedom can be used for reference purposes, which significantly increases the method resolution and helps to segregate the paired and closely located modes; 5) the role of OMA is not limited to being a refining tool for structural improvements, it proved to be useful for the vibration-based health monitoring (Zhang et al 2005). Within the scope of the core task, the possibility of application of various types of SHM sensors – acceleration and deformation – was considered
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