Wednesday  |  Salon 7  |  03:10 PM–03:30 PM

#15815, An Improved Method for Two-point Bending Stress Determination

The application of the ultra-thin glass plate has advanced the development of many high-tech industries. Necessary post-processing such as cutting, heating and impressing may cause the micro crack and residual stress in the ultra-thin glass plate. These micro crack and residual stress will reduce the strength of ultra-thin glass plate. Two-point bending test is a well-known approach to estimate the strength of ultra-thin glass plate and the quality of post-processing. However, by using the previous theories for two-point bending test [1, 2], only the bending stress on the profile center of the specimen can be determined. In other words, these previous theories [1, 2] are only established on the condition that the fracture is generated right on the profile center. Therefore, developing the theory for actually determining the two-point bending stress on the whole profile of specimen is imperative.

Recently, by combining the large deflection beam theory and the deflection beam profile equation, Sung et al. [3] proposed a method capable of determining the whole profile bending stress with any contact angle in two-point bending test except the 90 degree contact angle. In this study, the method was improved so that the whole profile bending stress can be determined not only in any contact angle but also in any compression displacement. An ultra-thin glass plate with 50μm thickness was bent with different contact angles and compression displacements. To verify the feasibility of this improved method, the measurement results of the profile and the compression forces of the ultra-thin glass plate were compared with the theoretical values.

[1] M. J. Matthewson, C. R. Kurkjian, S. T. Gulati, “Strength Measurement of Optical Fibers by Bending,” Journal of American Ceramic Society, Vol. 69, pp. 815-821, 1986.
[2] S. T. Gulati, J. Westbrook, S. Carley, H. Vepakomma, T. Ono, “Two point bending of thin glass substrate,” SID Symposium Digest of Technical Papers Vol. 42, No. 1, pp. 652-654, 2011.
[3] P. C. Sung, W. C. Wang, Y. W. Kuo, “Two-Point Bending Stress Determination of Ultra-Thin Glass Plates,” 2nd International Conference on Theoretical, Applied, Experimental Mechanics (ICTAEM2), Corfu Holiday Palace Hotel, Corfu, Greece, Paper No. 61, 4 Pages, June 23-26, 2019.

Po-Chi Sung   National Tsing Hua University
Wei-Chung Wang   National Tsing Hua University
Chih-Hao Chang   National Tsing Hua University