Optimization Design of Surface Wave Electromagnetic Acoustic Transducers Based on Simulation Analysis and Orthogonal Test Method

The energy conversion of electromagnetic acoustic transducers (EMATs) is typically lower, which seriously restricts the application of EMATs in the field of non-destructive testing and evaluation. In this work, parameters of surface wave EMATs, including structural parameters and electrical parameters, are investigated using the orthogonal test method to improve the transducer’s energy conversion efficiency. Based on the established finite element 2-D model of EMATs, the amplitude of the displacement components at the observation point of a plate is the optimization objective to be maximized with five parameters pertaining to the magnets, meander-line coils, and excitation signal as design variables. Results show that the signal amplitude of EMATs is 3.48 times on in-plane and 3.49 times on out-of-plane, respectively, compared with the original model. Furthermore, a new material (amorphous nanocrystalline material of type 1K107) is applied to optimize the magnetic circuit of EMATs and enhance the eddy current in an aluminum plate to increase the signal amplitude. Finally, the signal amplitudes obtained from the three types of models, that is, the original one, the optimization one after an orthogonal test, and the optimization one with the addition of magnetic concentrators, are analyzed and compared, indicating that the signal amplitude, compared with the original one, is 6.02 times on in-plane and 6.20 times on out-of-plane, respectively.

Age-related changes in the viscoelasticity of rabbit lens characterised by surface wave dispersion analysis

The viscoelastic properties of the young and mature rabbit lenses in situ are evaluated using wave-based optical coherence elastography (OCE). Surface waves in the crystalline lens are generated using acoustic radiation force (ARF) focused inside the eyeball. Surface-wave dispersion is measured with a phase-stabilised optical coherence tomography (OCT) system. The Young's modulus and shear viscosity coefficient are quantified based on a Scholte wave model. The results show that both elasticity and viscosity are significantly different between the young and mature lenses. The Young's modulus of the lenses increased with age from 7.74 ± 1.56 kPa (young) to 15.15 ± 4.52 kPa (mature), and the shear viscosity coefficient increased from 0.55 ± 0.04 Pa s (young) and 0.86 ± 0.13 Pa s (mature). It is shown that the combination of ARF excitation, OCE imaging, and dispersion analysis enables nondestructive quantification of lenticular viscoelasticity in situ and shows promise for in vivo applications.

Similarity of lithospheric structure of central and northwestern part of the Indian Peninsula inferred from observed surface wave forms

Observed surface wave forms across the central part of the Indian Peninsula and across northwestern part of the Peninsula have been considered. In a previous work, using group velocity of surface waves across former religion revealed model lithosphere IP 11. Observed surface wave forms across these two regions have been compared with synthetic seismograms using model IP 11. Observed wave forms are found to agree with synthetic one. This suggests that the average lithospheric structure of central and northwestern parts of the Indian Peninsula is similar and the Lithospheric model IP 11 is an approximation to it

Dynamics and morphology of droplet penetrating a soap film

This work reports experimental observation and theoretical explanation of the dynamics and morphology of a droplet passing through a soap film. During the process, the film undergoes four sequential responses: (1) film deformation upon droplet impact; (2) drop–film detachment; (3) coalescence of the film shell with the drop; (4) peel-off of the film shell. Physical models and the corresponding analytical expressions are developed to reveal the underlying physics for the observed four responses. It is identified that the film is an elongated catenoid under continuous stretch by the droplet, and that they separate at the fixed height of 5.8 times of the droplet radius while the detach point is located at the centre of the height. After separation, the droplet is wrapped with a film shell, which is then punctured by the ring tip of the converging surface wave at the impacting Weber number range of [45, 225]. The film shell then coalesces with the droplet, falls off with a fixed velocity and is eventually ejected as a bubble leaving the droplet with a transplanted surface of the soap solution.