Effect Of Different Radii Research Articles

Phased array guided wave propagation in curved plates

For the monitoring of plate structures, phased array guided wave has great application prospects to effectively determine damage location and size. Locating damage via phased array focusing is a challenging task, especially in curved plates. Hence, a systematic understanding of the behavior of the phased array guided wave propagation in curved plates is needed. In this study, a phased array focusing method was proposed for the damage localization of curved plates. Different damage scenarios and phased array focusing schemes are investigated in the finite element plate models with different radii. A high-speed signal generation and acquisition system including PZT actuators and sensors is set up. Experimental tests are carried out on a curved aluminum plate with embedded piezoelectric elements to verify the finite element models. Parametric studies are then performed to evaluate the effect of different radii and damage scenarios on the behavior of phased array guided wave propagation in curved plates. Numerical simulations and experimental results show that the proposed PA method has the capabilities of wave focusing and damage identification in curved plates. The damage localization method using phased array guided wave has the potential to be applied to the real-time monitoring of structures with curved plates.

Numerical Investigations on Stresses and Temperature Development of Tool Dies during Hot Forging

Hot-forming tools are subjected to high thermal and mechanical stresses during their application. Therefore, a suitable design of the tool die is important to ensure a long tool life. For this purpose, numerical simulations can be used to calculate the occurring stresses and the temperature development in the tools during the course of a stroke or over several forging cycles. The aim of this research is to investigate the effect of different radii on the resulting stresses in the lower die of the forming tools. Furthermore, the temperature evolution over several cycles is analysed to determine their effect on the temperature. When investigating the stress, it was found that a larger radius leads to a reduction in stresses. In addition, it could be numerically proven that the base temperature of the die levels off after a certain number of cycles. These findings will be used in further research dealing with the service life calculation of dies subjected to thermo-mechanical alternating stresses.

Interlaminar stress fields in circular cylindrical cross-ply laminated shells subjected to transverse loadings

This paper aims at contributing to the field of efficient analysis methods by introducing a semi-analytical approach that enables the investigation of the three-dimensional stress fields in cylindrically curved cross-ply laminated shells subjected to different transverse loadings under consideration of the free-edge effect. The novel analysis method incorporates a closed-form elasticity solution that is superimposed with a layerwise approach, in which the three-dimensional displacement field is discretized with respect to the thickness direction. Lagrangian shape functions of various order are used to interpolate between the a priori unknown displacement functions in the discrete grid points of the numerical layers. Employing the principle of minimum total potential energy, yields a system of coupled ordinary differential equations which is solved by utilizing the state-space approach. The accuracy of the developed method is verified by comparison with existing analytical approaches in the literature and detailed three-dimensional finite element computations. In addition to a study of the out-of-plane stresses in a circular cylindrical fibre metal laminate (GLARE®), the effect of different radius to thickness ratios and length to thickness ratios on the distribution of the interlaminar stress field is investigated.

Subwavelength plasmonic liquid sensor using Fano resonance in a ring resonator structure

A plasmonic Metal-Dielectric-Metal waveguide-based sensor with a radius of 0.44 μm is designed by generating Fano resonance in the device which consist of a gap in the main waveguide which acts like a Fabry-Perot structure and a micro ring resonator coupled to the main waveguide. The increased sensitivity of 1200 nm/RIU is achieved by optimizing the device parameters for different kind of liquids. Finite Element Method is used for complete study of the design. For analyzing the transmission modes in plasmonic systems, the normalized Electric Field distributions are calculated. Effect of different gap sizes, different coupling distances between ring & main waveguide and effect of different radius of ring on transmission and sensitivity of device for different liquids is also investigated. A large tunability of 740 nm in Fano peaks is achieved by changing the radius of the ring. The device results are useful in designing nanoscale and highly sensitive sensors for different liquids.

New fatigue life design approach for metal sheets with discontinuities

The existing references of Wöhler data curves (S-Nf fatigue life) for fully reversed cycling loading fail to incorporate the discontinuities effect on metal sheets fatigue life. Experimental results show that the discontinuities, i.e., holes and notches weaken metal sheets and reduce fatigue life. The notch fatigue strength reduction factor (Kf) cannot incorporate the discontinuity effect into the fatigue life prediction models. This paper investigates a new method to study the discontinuity effect on metals fatigue life by applying the Discontinuity Stress Triaxiality (DST) factor to fatigue life prediction models. Three discontinuity geometries were studied in order to investigate the different effect of different radius. A simulation using ABAQUS FEA was used to export the stress triaxiality at the notch root element. The results show that this new method can help in predicting fatigue life for high-strength metals and metals with sharp notches, unlike the Kf factor. Also, the theoretical results show good correlation with the experimental results.

Fast and slow light generated by surface plasmon wave and gold grating coupling effects

We present here the results of a simulation of the effect of gold and graphene coatings on silicon micro-ring resonators. We studied the effect of different radii of graphene on the time delay, from which one an interesting aspect of light pulse behaviors, such as fast light, was numerically investigated. The obtained results indicate that the time delay can be varied, which is in good agreement with theoretical predictions. Fast and slow light pulse trains can be obtained by modifying the throughput port, which forms the gold grating length. The temporal gaps between the fast and slow light in the used graphene and gold are 140 and 168 fs, respectively, which can be tuned by varying the radius or grating length. The obtained results show that such a device may be useful in applications requiring fast and slow light pulse train pairs, such as optical switching, sensors, communications, and security applications.

Why intra-epidermal electrical stimulation achieves stimulation of small fibres selectively: a simulation study

The in situ electric field in the peripheral nerve of the skin is investigated to discuss the selective stimulation of nerve fibres. Coaxial planar electrodes with and without intra-epidermal needle tip were considered as electrodes of a stimulator. From electromagnetic analysis, the tip depth of the intra-epidermal electrode should be larger than the thickness of the stratum corneum, the electrical conductivity of which is much lower than the remaining tissue. The effect of different radii of the outer ring electrode on the in situ electric field is marginal. The minimum threshold in situ electric field (rheobase) for free nerve endings is estimated to be 6.3 kV m−1. The possible volume for electrostimulation, which can be obtained from the in situ electric field distribution, becomes deeper and narrower with increasing needle depth, suggesting that possible stimulation sites may be controlled by changing the needle depth. The injection current amplitude should be adjusted when changing the needle depth because the peak field strength also changes. This study shows that intra-epidermal electrical stimulation can achieve stimulation of small fibres selectively, because Aβ-, Aδ-, and C-fibre terminals are located at different depths in the skin.

Wave propagation in piezoelectric rings with rectangular cross-sections

The ring ultrasonic transducers are widely used in the ocean engineering and medical fields. This paper employs an extended orthogonal polynomial approach to solve the guided wave propagation in two-dimensional structures, i.e. piezoelectric rings with rectangular cross-sections. The extended polynomial approach can overcome the drawbacks of the conventional orthogonal polynomial approach which can be used to solve wave propagation in one-dimensional structures. Through numerical comparison with the available results for a rectangular aluminum bar, the validity of the present approach is illustrated. The dispersion curves and displacement and electric potential distributions of various rectangular piezoelectric rings are calculated, and the effects of different radius to thickness ratios, width to height ratios and polarizing directions on the dispersion curves are illustrated.

Wave Propagation in Piezoelectric Rods with RectangularCross Sections

The ring ultrasonic transducers are widely used in the ocean engineering and medical fields. This paper employs an extended orthogonal polynomial approach to solve the guided wave propagation in two-dimensional structures, i.e. piezoelectric rings with rectangular cross-sections. The extended polynomial approach can overcome the drawbacks of the conventional orthogonal polynomial approach which can be used to solve wave propagation in one-dimensional structures. Through numerical comparison with the available results for a rectangular aluminum bar, the validity of the present approach is illustrated. The dispersion curves and displacement and electric potential distributions of various rectangular piezoelectric rings are calculated, and the effects of different radius to thickness ratios, width to height ratios and polarizing directions on the dispersion curves are illustrated.

Measurement of Curved Surface Roughness by Polychromatic Speckle Method

The influence of curved surface on the method of polychromatic speckle autocorrelation measuring surface roughness is studied by introducing the curvature radius of surface. The rough surface, and the dichromatic speckle patterns, and trichromatic speckle patterns are simulated, and the effects of different radius of curved surface on speckle patterns and speckle elongation ratio are discussed. The results show that the larger curvature radius is, the larger speckle elongation becomes, and the smaller the deviation of measured surface roughness is. Therefore, influence of curvature of rough surface on measurement precision should be taken into consideration during measuring process.