森田 昇

Wheel scribing techniques were commonly used for glass separation. We have studied on the internal stress field during/after wheel scribing using the photoclastic method. Internal stress data obtained by photoelastic method was integrated data of the light progression, and internal stress induced by a scribing wheel distributed three-dimcnsionally. This characteristic complicates the explanation of the photoclastic data. In this paper, we investigate two dimensional internal stress fields by the indentation of a wedge on a thin glass sheet. As a result, birefringence and azimuthal angle was obtained during/after the indentation. Internal stress by the plastic deformation was observed. First, median cracks were propagated after the indentation, then lateral cracks were propagated. The internal stress was released along with the crack propagation.

Recently, ultrasonic flaw detection among the non-destructive testing is used extensively. Generation laser scanning method is known as one of the ultrasonic flaw techniques, and it has an advantage that defects are easily visualized as a time-resolved damaged region image. In this study, we propose improvement methods of detection accuracy as follows; (i)extraction of A_0 signal from A-mode wave which is one of the Lamb waves, (ii)compensation of the attenuated intensity during wave propagation. In addition, the optimization of sensor position was carried out. For CFRP laminates and aluminum plates with surface/internal detects, the improvement of image quality was achieved by the combination of these methods.

In this study, I propose to improve the material features such as heat dissipation and water absorption by using a fractal on material structure for the purpose of surface area expansion. The usefulness of the fractal structure having a self-similar in part and whole was revealed in conjunction with the analysis. In the analysis, the improvement of the water absorption and heat transfer in the fractal could be expected. Unfavorable shape to simple diffusion as linear square fractal was present in the test specimen experiment. In addition to that, the results show that heat transfer inhibition caused by the formation of the boundary layer by convection in the triangular fractal. Therefore, selection of the optimal fractal structure according to the various purpose is required.

Photoelasticity is a method that enables experimental stress analysis in transparent materials by analyzing the photoeleastic fringes. In this paper, we propose a method to estimate phase difference correctly when the experimental stress is increased monotonously. The point of turning over the phase difference was estimated and photoelastic fringes were counted automatically. The developed program counted phase difference correctly.

Laser joining between two non-alkali aluminoborosilicate glass sheets was conducted using vanadate glass frit, which had lower melting point (m. p.) than substrates, as an insert material. In order to investigate the optimal joining conditions, the laser power and scanning speed were varied using circular and elliptical shaped laser beams in the joint experiment. Experimental results showed that the excess power irradiation produced a lot of babbles in the joint area, and insufficient power caused a rapid detachment just after joining. However, these defects were suppressed by elliptical beam irradiation. High-speed camera observations suggested that the elliptical beam irradiation contributed to the slower cooling of molten insert glass compared to the case of circular beam irradiation. Numerical calculation of temperature distribution around laser irradiated area was also carried out using finite difference method. Calculated results showed that the melting time in the case of elliptical beam was 2.5 times longer than that of circular beam. Therefore, the elliptical beam is more applicable to the sealing between two glass substrates.

The fiber laser joining between non-alkali glass sheets was conducted using vanadium-based low melting-point (m. p.) glass frit as an insert material, hi order to investigate the reason of blowhole formation in glass frit during laser irradiation, high-speed camera observation was carried out. As a result, it was found that the most of blowholes were derived from inherent voids contained in/on glass frit. For the suppression of blowhole formation, the thermal treatment of as-received glass frit in air/vacuum atmosphere was proposed. In the case of heat-treatment in vacuum atmosphere, the joint quality was improved because the contained voids in glass frit was surface-exposed before laser irradiation.

The crack propagation behavior was observed by high-speed camera during wheel scribing of non-alkali glass sheet. As a result, it was found that the propagation depth was largely influenced by the applied load to scribing wheel. In the case of glass sheet of 0.7 mm thickness, for example, a formed crack rapidly propagated to the depth direction when the applied load was 20 N. On the other hand, when the applied load was 10 N, a formed crack hardly propagated. In order to investigate the reason of difference between crack propagation behaviors, high-speed birefringence measurements were also conducted. The measurement from above of glass sheet showed that the characteristic patterns appeared in phase difference diagram depending on the applied load conditions.

The crack propagation behavior and the internal stress field during mechanical cleavage of non-alkali glass sheets (thickness: 0.7 mm) were visualized by high-speed imaging techniques. At first, the effect of scribing conditions on the fractured surface quality was investigated when the scribing wheel with surface asperities was used. It was found that the surface quality was strongly influenced by an applied load. In the case of low load conditions (?11 N), the fractured surface exhibited rugged patterns known as 'hackle', and it gradually changed to regular striped pattern known as 'ribmark' with the increase of applied load (12 N ?). In order to understand the reason why the surface quality changed with the applied load, the crack propagation behavior was observed using a high-speed camera. The results showed that the generated crack hardly propagated to thickness direction when the applied load was low, in contrast to the rapid propagation under the high load conditions. Because the crack propagation behavior was likely determined by the stress field around the generated crack, the phase difference measurement, which was proportional to the principal stress difference, was conducted using a high-speed polarization camera. The results showed that the phase difference gradually vanished, i.e. the stress relaxation occurred, with the crack propagation especially in the high load conditions. By the image analysis for obtained phase difference from the polarization camera, an in-process estimation method of fractured surface quality was proposed.