In this article, the non-linear vibro-acoustic modulation technique is used for structural damage detection. A new experimental configuration and data processing strategy are proposed to improve the damage detection capability of the technique. The swept sine chirp excitation is used for both low-frequency vibration/modal and high-frequency ultrasonic excitations. The adaptive resampling procedure is then applied to extract information about modulation intensity that relates to damage. The proposed method is illustrated using numerical simulations and experimental tests. The latter involves crack detection in an aluminium beam. The results of the proposed method are compared with the classical approach based on single harmonic excitation, demonstrating that similar damage detection information can be extracted. However, the major advantage of the proposed method is simplicity and robustness since no a priori selection of excitation frequencies is needed. As a result, crack detection is more reliable and unambiguous.

The paper presents a new damage-detection method based on nonlinear crack-wave interaction. Low-frequency vibration excitation is introduced to perturb damage, and high-frequency interrogating wave is used to detect damage-related nonlinearities. However, in contrast to other crack-wave interaction approaches, localised wave packets are used for high-frequency excitation. The synchronisation of the low-frequency vibration with the interrogating high-frequency wave packets is a key element of the proposed method. Numerical simulations and simple experimental tests in cracked aluminium beams are performed to demonstrate the method. The results show that the proposed method can detect and localise damage-related and intrinsic nonlinearities, allowing for reliable damage detection. The method does not require baseline measurements representing an undamaged condition, and it is not sensitive to temperature variations.

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Signal processing method based on wavelet transform used in non-linear acoustic test is presented in the paper. The method is applied for sidebands identification in response signal acquired during vibro-acoustic modulation test of impacted carbon fiber reinforced plate (CFRP). The plate was impacted with known energy using drop-weight testing machine. The modulation effect in investigated specimen results from the interaction of low and high frequency excitation with damage. The paper investigates different than mono-harmonic low-frequency excitation usually used in non-linear acoustics tests. Application of aperiodic low-frequency excitation signal allows to omit the modal test, where natural frequency of the structure are estimated. However, this requires the use of dedicated signal processing methods.

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The aim of the paper is to present a recent development in the field of communication from the point of view of embedded machine condition monitoring system (CMS). Although the general purpose of CMS remains the same over years, various electronic innovations open new possibilities of enhancement, including lower price, smaller size, larger bandwidth, smaller energy consumption or larger distance for wireless transmission. The paper considers a general notion of an embedded monitoring system, which consists of a sensor, data acquisition and processing unit, storage peripherals, and a communication module for final data destination. For each of these defined parts, a detailed description of possible data transfer protocols and interfaces is given, including popular, and experimental ones.