Papers by Keyword: In-Plane Displacement

Abstract: The determination of dynamic characteristics of microelectromechanical system (MEMS) devices is of great importance. Currently, vibrometer techniques using a Laser-Doppler Vibrometer (LDV) are used for dynamic measurement of MEMS, utilizing an interferometer based on a stroboscope and high-speed cine photomicrography are used for MEMS. But, these methods can’t be used for 3D dynamic displacement measurement simultaneously because of their limitations. In this paper, an optical system for 3D dynamic displacement measurement of micro-components is presented using stroboscopic fringe projection and digital image correlation (DIC), which can measure both in-plane and out-of-plane motions simultaneously. In the system, stroboscopic fringe patterns are projected onto the surface of a vibrating specimen by a phase-shifting projector and stroboscopic illumination supplied with a pulsed laser diode. Synchronization between the stroboscopic laser and the driving signal for the specimen vibrating is achieved by the stroboscopic controller. For a certain vibration state, four deformed phase-shifting fringe patterns are captured by a high-resolution CMOS camera with a long working distance microscope. The images are processed by a phase-shifting technique to obtain the phase distribution. The surface pattern of the specimen without fringes could be obtained by certain phase-shifting algorithms. When stroboscopic pulses are delayed, the stroboscopic phase is changed and another vibrating status could be captured in the same way. Comparing the phase distributions of these two states, the out-of-plane displacement is achieved, which is the displacement of the specimen between these two states. The in-plane displacement could be obtained from the surface pattern without fringes by DIC. Adjusting the phase delay of illumination by stroboscopic controller, the motions of the specimen in the whole vibration period can be obtained.

Abstract: In the present work, thermal expansion coefficients of a number of organic coatings were studied by a non-destructive technique (NDT) known as shearography. An organic coating, i.e., epoxy, on a metallic alloy, i.e., carbon steels, was investigated at a temperature range simulating the severe weather temperatures in Kuwait especially between the daylight and the night time temperatures, 20-60 0C. The investigation focused on determining the in-plane displacement of the coating, which amounts to the thermal deformation (strain ) with respect to the applied temperature range. Along with the experimental data, a mathematical relationship was derived describing the thermal deformation of a coated film as a function of temperature. Furthermore, results of shearography indicate that the technique is very useful NDT method not only for determining the thermal expansion coefficients of different coatings, but also the technique can be used as a 2Dmicroscope for monitoring the deformation of the coatings in real-time at a submicroscopic scale.

Abstract: In this paper, we apply phase-shifting digital holographic interferometry to simultaneous measurement for out-of-plane and in-plane displacements by employing two beam illuminations for an object. Phase-shifted holograms before and after displacements of the object using each of two beams are recorded by a CCD camera, separately. The complex amplitude at each pixel of the CCD plane is analyzed from the holograms taken with phase-shifting. The complex amplitude of he object is reconstructed from the complex amplitude distribution on the CCD plane using the Fresnel diffraction integral. Each directional phase difference distribution is obtained by calculating the phases before and after deformation for each directional beam. The phase distribution for out-of-plane displacements is obtained by calculating the sum of the two phase difference distributions. The phase distribution for in-plane displacements is obtained by calculating the difference of the two phase difference distributions. The phase values provide accurate displacement distribution information. Actually, when the object deforms in both out-of-plane and in-plane directions, it is possible to analyze the displacement distribution in each direction. The theory and an experiment are shown.