• 비파괴검사학회지
• /
• 제31권6호
• /
• pp.656-664
• /
• 2011

In this work, a numerical model is proposed for the relation between the magnitudes and the depth residual stress with the velocity of Rayleigh wave. Three cases, stress-free, uniform stress and layered stress, are investigated for the change tendency of the Rayleigh wave speed. Using the simulated signal with variation of residual stress magnitude and depth, investigation of the parameters for fitting residual stress and velocity change are performed. The speed change of Rayleigh wave shows a linear relation with the magnitude and an exponential relation with the depth of residual stress. The combination of these two effects could be used for the depth profile evaluation of the residual stress.

• Nuclear Engineering and Technology
• /
• 제56권7호
• /
• pp.2563-2569
• /
• 2024

The monochromatic hyperbolic neutron density wave is conceived as a Rayleigh-like wave with mixed transverse and longitudinal components. It is proved for the first time that the absolute ratio of the longitudinal to transverse interfering components, varies, with increasing the frequency of this wave, from zero to 1. Such a limited variation is to be coined as vibrational enhancement of evolutionary one-speed neutron transport.

• 비파괴검사학회지
• /
• 제37권1호
• /
• pp.29-36
• /
• 2017

최근 KTX (Korean Train Express) 열차의 사고의 대부분은 기기의 오작동, 차량 부품의 노후와에 따른 고장 및 장애발생, 신호장치에 대한 인적오류 등이 주된 원인이였다. 특히, 차량부품 중 제동 디스크의 파손은 하부 차축 및 차륜에 충격을 가해 탈선의 우려와 고속 충돌 등 대형 인명 피해를 낳을 수 있다. 따라서 본 연구에서 KTX의 제동 디스크(Solid Type, Ventilation Type)를 형상화하고, 이를 동작시켜 균열을 측정하여 DB화 할 수 있는 균열검측시스템을 구축하였다. 제동 디스크의 표면균열을 검사하기 위하여 Rayleigh wave를 이용하였으며 수침기법으로는 제동디스크 장착상태에서 탐상의 어려움이 인하여 국부수침 탐상기법을 활용하여 제동디스크의 초음파 검사모듈을 개발하였다. 또한 제동디스크의 회전에 따라 측정된 균열을 저장할 수 있는 균열검측 자동화장치와 제동 디스크의 초음파 검사모듈을 이용하여 제동 디스크의 표면결함을 평가하였다.

• Structural Engineering and Mechanics
• /
• 제25권5호
• /
• pp.597-611
• /
• 2007

Many works have been done in classical theory of thermoelasticity in materials with memory by researchers like Nunziato, Chen and Gurtine and many others. No work is located in generalized thermoelasticity regarding materials with memory till date. The present paper deals with the wave propagation in materials with memory in generalized thermoelasticity. Plane progressive waves and Rayleigh waves have been discussed in details. In the classical theory of heat conduction it was observed that heat propagates with infinite speed. This paradox has been removed in the present discussion. The set of governing equations has been developed in the present analysis. The results of wave velocity and attenuation coefficient corresponding to low and high frequency have been obtained. For thermal wave the results show appreciable differences with those in the usual thermoelasticity theory.

• 비파괴검사학회지
• /
• 제30권6호
• /
• pp.578-586
• /
• 2010

This paper describes a theoretical model and acoustic analysis of hysteresis of contacting surfaces subject to compression pressure. Contacting surfaces known to be nonlinear and hysteretic is considered as a simple spring that has a complex stiffness connecting discontinuous displacements between two solid contact boundaries. Mathematical formulation for 1-D interfacial wave propagation between two contacting solids is developed using the complex spring model to derive the dispersion relation between the interface wave speed and the complex interfacial stiffness. Existence of the interface wave propagating along the hysteretic interface is studied in theory and discussed by investigating the solution to the dispersion equation. Unlike the linear interface without hysteresis, there can exist only one distinct mode of interface waves for the hysteretic interface, which is anti-symmetric motion. The anti-symmetric mode of interface wave propagates with the velocity faster than the Rayleigh surface wave but less than the shear wave depending on the interfacial stiffness. If the contacting surfaces are compressed so much that the linear interfacial stiffness is very high, the hysteretic stiffness does not affect the interface wave velocity. However, it has an effect on the speed of interface wave for a loosely contact surfaces with a relatively low linear stiffness. It is also found that the phase velocity of anti-symmetric wave mode converges to the shear wave velocity in despite of the linear stiffness value if the hysteretic stiffness approaches 0.5.

• 한국생산제조학회지
• /
• 제20권1호
• /
• pp.47-52
• /
• 2011

It is well known that stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates because the layup of composite laminates influences their properties. Ultrasonic NDE of composite laminates is often based on the backwall echoes of the sample. A pair of such transducers was mounted in a holder in a nose-to-nose fashion to be used as a scanning probe on composites. Miniature potted angle beam transducers were used (Rayleigh waves in steel) on solid laminates of composites. Experiments were performed to understand the behavior of the transducers and the nature of the waves generated in the composite (mode, wave speed, angle of refraction). C-scan images of flaws and impact damage were then produced by combining the pitch-catch probe with a portable manual scanner known as the Generic Scanner ("GenScan"). The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to fiber orientation of the CFRP composites, including low level porosity, ply waviness, and cracks. Therefore, it is found that the experimentally Rayleigh wave variation of pitch-catch ultrasonic signal was consistent with numerical results and one-side ultrasonic measurement might be very useful to detect the defects.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.68-71
• /
• 2001

This paper has been studied for a comparison of the propagation and noise characteristics between ultrasonic and electromagnetic wave for the high speed communication of the short range telemetry. We analyze the propagation depth of electromagnetic and ultrasonic wave by skin depth effect and by ultrasonic loss ratio. We also studied several effects such as near field effect in electromagnetic wave and Rayleigh scattering noise of ultrasonic wave, etc. We show the experimental results of their propagation loss and modulation experiments in water. The experimental results show that both method is good for the implementation of short range telemetry.

• Steel and Composite Structures
• /
• 제37권2호
• /
• pp.137-150
• /
• 2020

In this research work, the analytical rotating vibration for functionally graded shell with ring supports are restricted to some volume fraction laws based on Rayleigh-Ritz technique. The frequencies of functionally grade cylindrical shells have been investigated for the distribution of material composition of material with two kinds of material. Stability of a cylindrical shell depends highly on these aspects of material with ring supports. The frequency behavior is investigated with fraction laws versus circumferential wave number, length-to-radius and height-to-radius ratios. The frequencies are higher for higher values of circumferential wave number. The frequency first increases and gain maximum value with the increase of circumferential wave mode. Moreover, the effect of angular speed is also investigated. It is examined that the backward and forward frequencies increases and decreases on increasing the ratio of height- and length-to-radius ratios.

• Geomechanics and Engineering
• /
• 제19권3호
• /
• pp.241-254
• /
• 2019

A finite element approach is presented to examine ground vibration characteristics under various moving loads in a homogeneous half-space. Four loading modes including single load, double load, four-load, and twenty-load were simulated in a finite element analysis to observe their influence on ground vibrations. Four load moving speeds of 60, 80, 100, and 120 m/s were adopted to investigate the influence of train speed to the ground vibrations. The results demonstrated that the loading mode in a finite element analysis is reliable for train-induced vibration simulations. Additionally, a three-dimensional finite element model (3D FEM) was developed to investigate the dynamic responses of a track-ballast-embankment-ground system subjected to moving loads induced by high-speed trains. Results showed that vibration attenuations and breaks exist in the simulated wave fronts transiting through different medium materials. These tendencies are a result of the difference in the Rayleigh wave speeds of the medium materials relative to the speed of the moving train. The vibration waves induced by train loading were greatly influenced by the weakening effect of sloping surfaces on the ballast and embankment. Moreover, these tendencies were significant when the vibration waves are at medium and high frequency levels. The vibration waves reflected by the sloping surface were trapped and dissipated within the track-ballast-embankment-ground system. Thus, the vibration amplitude outside the embankment was significantly reduced.

• 한국정밀공학회지
• /
• 제18권2호
• /
• pp.146-151
• /
• 2001

The effects of slant interface in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity. The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamic stress field around the dynamically propagating inclined interface crack tip in the three point bending specimens. The dynamic load is applied by a hammer dropped from 0.08m high without initial velocity. The dynamic crack propagation velocities and dynamic stresses field around the interface crack tips are investigated. Theoretical dynamic isochromatic fringe loops are compared with the experimental reults. It is interesting to note that the crack propagating velocity becomes comparable to the Rayleigh wave speed of the soft material of a specimen when slant angle decreases.