An effective thermal deformation measurement technique for high power light emitting diode (LED) during emitting the light was developed using digital image correlation method (DICM) with spectrograph. Camera image detected by charge coupled device (CCD) during emitting light from LED was affected by two causes, an intensity of emitting light which depends on wavelength and a radiant intensity of exothermic heat which depends on temperature. Optimization of detected wavelength by band-path filter, in consideration of emission wavelength and surface temperature of the LED with the Plank's radiation law, was absolutely improved quality of CCD camera image. The measured thermal deformation of the encapsulation resin molded the LED on epoxy glass substrate was up to 30μm in z-axis displacement over 400K of exothermic heat temperature with 350mA by the developed technique.
Imaging based nondestructive monitoring systems are important to evaluate the integrity of large-scale infrastructures. This paper presents a novel accurate displacement measurement method based on imaging technique. The tile patterns existing on the surface of a monitored structure are utilized to measure the displacement distribution through the sampling Moiré method. In our proposed method, the displacement is calculated from the components of both fundamental and higher frequencies of the Fourier series of the tile patterns. Compared with the conventional sampling Moiré method where only the fundamental frequency component is considered, the developed method features high-resolution, accurate, fast, low-cost, and being easy to implement. The principle of in-plane displacement measurement method is presented. The effectiveness of this method was confirmed by displacement experiments performed in both indoor and outdoor. The displacement distribution with an accuracy of sub-millimeter could be evaluated from the picture taken more than 20 meters away from the measuring object.
In this study, a method for identifying the material characteristics of dissimilar materials from measured displacement fields is proposed. The virtual fields method is employed for determining the material characteristics. The principle for identifying the characteristics of the dissimilar materials characteristics is described. The appropriate virtual displacements for the identification are automatically determined for minimizing the effect of the measurement errors. A three-point bending test and tensile tests are performed for validating the proposed method. Displacement distributions on a specimen surface are measured using mesh-based global digital image correlation. Then, the inverse analyses of material characteristics from the displacements under various loads are carried out. Results show that the elastic material characteristics of the dissimilar materials can be identified by the proposed method.
This paper presents a new and convenient process for determining the material plasticity parameters of metal materials through an indentation test conducted using a Rockwell testing machine and FE analysis. Identified parameters almost coincide with practical values. The proposed method can be used to evaluate the characteristics of materials on the order of micro to millimeters. First, the P-h curves of the indentation are determined by experiment. Second, FE analysis of the indentation test assuming plastic hardening behavior in power-law hardening material is specified by the stress-strain curve. The FE model consisted of the test piece material and the indenter with a spring element considered the elastic deformation of the measuring system. The material parameters can be identified based on the curve fit using the polynomial function consisting of material parameters. The best solution is determined by using the response surface methodology. For identification example using steel and cupper alloy, the estimation of the plastic and elastic properties are possible for practical use.
For the purpose of a verification of an estimation method that material plasticity parameters are identified by using indentation test and FE analysis, experiment are carried out using the Rockwell testing machine on metal materials. The P-h curve obtained from the experiment and FE analysis, the characteristics of graph has almost the same curve. The material parameters can be identified based on the curve fit using the polynomial function consisting of material parameters. For example, steel metals using in the manufacturing process, the estimation of the work hardening parameters and the elastic properties were almost matched with the results of the tensile tests. Furthermore, the shapes of the actual drawing press and plastic deformation FE analysis using the material parameters of this identification are matched within the allowable range of profile error.
Injecting liquid downward into the stationary atmosphere from an oblong-orifice of 0.15mm x 1.3mm, the breakup behavior of the liquid jet was observed in detail by flash photography. Test liquids employed were water, ethanol and aqua-solutions of propylene-glycol. Liquid injection velocity was ranging from 1 to 20 m/s. It was found that the liquid jet deformed into chains of bamboo-leaf-like liquid films, the edges of the liquid film became thick rims due to the surface contraction, the threaded-beads-like wave of short wave-length appeared on the rims, and the liquid jet broke up regularly due to the wave. The resulting droplets were more uniform and smaller than those of liquid jet from circular-orifice. Satellite droplets were also formed, but the generating frequency was not so high. The characteristics of interfacial wave on liquid jet and the size distribution of droplets were investigated by image analysis. Based on the results, the mechanism of regular breakup of the liquid jet from oblong-orifice was discussed. The effects of liquid properties upon the suitable velocity range for regular breakup were also examined. It was supported that the regular breakup of liquid jet should be of use as a simple methodology for uniform-sized droplet production.