Papers by Author: Eisaku Umezaki

Abstract: A system was developed for simultaneously measuring stress and temperature in structures in time series. The stress and temperature were measured using the photoelastic technique in the form of phase stepping and the thermographic technique, respectively. Four phase-stepped photoelastic images were captured simultaneously using beam-splitting optics. A beam splitter was used for transmitting light in the visible range while simultaneously reflecting light in the infrared range. The system was applied to ultraviolet curing resin with a step part illuminated with ultraviolet rays, and the stress and temperature in the curing process were measured. Results showed that the stress and temperature in the curing process can be measured simultaneously in time series using the system. The step part of the resin affected the distribution of the stress and temperature

Abstract: This paper presents an application of a new point-wise technique for unwrapping the isoclinic parameter determined by a four-step color phase shifting. The unwrapping technique is based on a largest region in a binary image that corresponds to a largest visible-wrapped period of the computed isoclinic parameter. The largest region is obtained using an intersection operation between the extended ranges of the computed isoclinic parameter. The method uses four raw photoelastic fringe images. The technique is applied to a circular ring containing isotropic points subjected to diametral compression. Results show the method provides the correct isoclinic parameter in the true interval over the entire domain.

Abstract: The two-dimensional deformation of wood with different grains under shearing loads was measured using an electronic speckle pattern interferometry (ESPI) technique. The radical, tangential and end sections of Douglas firs (Pseudotsuga menziesii) were used as specimens. Results revealed that the deformation values significantly vary for every part of the specimens, and the ring directions of earlywood and latewood, which compose the annual rings, have an effect on the two-dimensional deformation of wood.

Abstract: A three-step phase shifting approach for automatic determination of the isoclinic parameter in photoelasticity is presented. Unreliable isoclinic values affected by the isochromatic parameter are solved using the white light. The method uses three fringe images digitally captured by a digital camera for three different configurations of the dark-field plane polariscope. For a circular disk under compression, results show the method permits the isoclinic parameter in the range -π/2 to π/2 with almost free of the isochromatic parameter and comparable with theory.

Abstract: The behavior of liquid in containers subjected to impact loads due to free fall was investigated using a visualization technique. Two types of containers were used. One consisted of a case made of transparent plastic plates and a liquid-packing bag made of transparent plastic films. The bag contained about 1,000 ml of liquid. The other was a case made only of transparent plastic plates. The case contained about 1,000 ml of water. The liquid consisted of water and ethanol. Polyethylene particles of about 3 mm in diameter were included in the liquid to visualize the movement of liquid in the containers. The containers were subjected to impact due to free fall, and photographs of the containers were taken using a high-speed camera. Results indicated that the behavior of liquid in the container with a liquid-packing bag is different from that of the container without a liquid-packing bag.

Abstract: The two-dimensional deformation of wood under shearing loads is measured using an electronic speckle pattern interferometry (ESPI) technique. The radical and tangential sections of Douglas firs are used as specimens in the longitudinal direction. Results reveal that large two-dimensional deformation of the wood can be measured using the ESPI technique, the deformation values significantly vary for every part of the specimens, and the ring directions of earlywood and latewood, which compose the annual rings, have an effect on the two-dimensional deformation of wood.