PSI - Issue 37

Dmitrijs Serdjuks et al. / Procedia Structural Integrity 37 (2022) 555–562 Dmitrijs Serdjuks et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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displacement with high accuracy, a vision-based displacement measurement system was proposed (Hoksbergen (2013)). The system was composed of a uniquely designed marker and a camera, where relative translational and rotational displacement between the marker and the camera was estimated by finding a homograph transformation. Laser vibrometer, in which the natural resonance modes are measured excited by a shaker and measured using a laser interferometer, is routinely performed in 2D for out-of-plane displacement patterns on vibrating structures, and, with greater system complexity, in 3D for in-plane displacement measurements (Jeon et al. (2014)). Combining dynamic SHM methods using ultrasonic guided waves and vibrations with static strain-based sensors and sensors for environmental entities might yield a robust multi-sensor SHM approach based on data fusion (Castellini et al. (2006)). In order to determine structural damage to structures, mathematical models are often used to help identify structural damage and to help identify the location of the damage and the trends for further failure. However, it is not always possible to use a modelling approach, as the structures being assessed can be complex interacting elements where it is hardly possible to apply mathematical models. In such cases, an alternative approach based on non-model methods of analysis may be appropriate. In this case, non-model methods are used based on the analysis of experimentally obtained data to determine the correlations between the measured parameters in order to identify patterns inherent in different types and intensities of damage. The non-model approach is based on the use of numerical methods for processing the input data. The result is an empirical model which can be linked to specific scenarios of structural components damage. Non-model methods for analyzing assemblies and structures include methods for assessing the response of a structure or assemblies exposed to vibration. Current methods for evaluating vibration monitoring systems by non-model vibration analysis methods are summarised below: • Non-model-based damage identification using measured mode shapes • Non-model-based identification using a continuously scanning laser doppler vibrometer system • Vibration based damage assessment technique based on damage index (DI) method • Vibration-based damage detection based on combination of multiple reference impact test and finite element model The next chapter describes a non-model vibration analysis method for correlating coaxial accelerations , a measuring device with a description of its components and the main stages of applying the proposed method. 3. Materials and methods 3.1. Method of coaxial accelerations correlation for quality assessment of structural joints A non-model vibration analysis method of coaxial accelerations correlation is proposed. The method is based on the mathematical analysis of vibrations of structural joints in 3 spatial directions using 3D accelerometers, located at different parts of a joint and orientated coaxially. Analysis of vibration in 3D space enables to test the stiffness of joints of planar structures, such as a T-joint of the girder and additional beam. The developed measuring device and its major components are shown on the Fig. 2 (a). The method of verification comprised the following steps of data collection. A frequency sweep audio signal in a wide frequency range from 10 to 500 HZ and a duration of 0.5 second was applied to the tested structure. The obtained vibration record (Fig. 2 (c)) passed the Fourier transform and the maximum magnitude frequency of the spectrum was selected. A n ew signal of the selected frequency was applied the next. Several measurements were recorded at each condition of the joint stiffness.