High accurate flow measurement is important for process monitoring. The clamp-on ultrasonic flow meter is a type of non-invasive and non-intrusive flow measurement technique. However, the traditional used transit-time difference method in the clamp-on ultrasonic flow meters cannot achieve accurate measurement under small flow rates because the measurement accuracy is limited by the equipment’s sampling rate and system error. This article proposes a novel flow measurement method by using signal voltage amplitude difference (VAD). The transit-time difference information is converted into voltage amplitude difference information, therefore the measurement error due to sampling rate at small flow conditions can be eliminated and the measurement accuracy is improved. The analytical solutions of ultrasonic vibrations are analyzed and a new “M” shaped ultrasonic transducer design is introduced. The new transducer can generate and receive downstream and upstream ultrasonic signals simultaneously. In this scenario, the VAD method can be used for flow measurement. In addition, a variety of influencing factors are analyzed to further improve the measurement accuracy of the proposed method. Experimental results indicate that the combined uncertainty of the VAD method exhibits a 62.5% reduction compared to that of the transit-time difference method.

Angled shear vertical (SV) waves have been successfully employed in the non-destructive testing of welds, pipes, and railways. Non-contact meander-line coil electromagnetic acoustic transducers (EMAT) have many benefits in generating angled SV waves. The most important benefit is that the incidence angle of an SV wave can be controlled by the excitation frequency. However, the incidence angle of a traditional SV-wave EMAT is reported to be under 45 degrees in many cases. In this work, such cases are tested, and the problems of the received signal at large incidence angles are found to be due to wave interference and small signal amplitudes. An equivalent finite element (FE) model is established to analyze the problem, and the main reason is found to be the head wave. An alternative configuration of angled SV-wave EMAT with horizontal magnetization is proposed to reduce the influence of the head wave. Finally, the results from simulations and experiments show that the proposed EMAT has a larger signal amplitude and significantly reduced interference in large-incidence angle scenarios. Moreover, an incidence angle of an SV wave of up to 60 degrees can be achieved, which will help improve the performance and capability of nondestructive testing.

Electromagnetic acoustic transducers (EMATs) have significant potential for measuring stress in metallic materials due to their non-contact capability. Traditional stress measurement methods based on acoustoelastic theory require calibration, and their accuracy depends on precisely determining the relationship between acoustic time-of-flight (ToF) and stress. However, this relationship is difficult to establish directly because it is influenced by the specimen’s density, Second-Order Elastic Constants (SOECs), and Third-Order Elastic Constants (TOECs). In practical applications, extensive calibration is necessary to ensure measurement accuracy, and re-calibration is required whenever the specimen’s material changes. To address this limitation, this study proposed a calibration-free uniaxial stress measurement method for metallic materials using orthogonal shear-vertical (SV) EMATs. In this method, two EMATs generate SV waves propagating in perpendicular directions, while two additional EMATs receive these waves. Theoretical analysis demonstrated that uniaxial stress measurements depend solely on the ToF of the two orthogonal SV waves and are independent of factors such as SOECs and TOECs. The feasibility and effectiveness of the proposed method were validated through finite element analysis and experimental testing. Experimental results showed that the maximum relative error for calibration-free uniaxial stress measurements of aluminum alloy specimens was 9.29%.