Research on collective cracks' strain field with digital real-time holography

R. X. Guo; H. T. Xia; Z. B. Fan; B. C. Yang; J. C. Li; T. C. He

doi:10.1117/12.828791

20 May 2009 Research on collective cracks' strain field with digital real-time holography

R. X. Guo, H. T. Xia, Z. B. Fan, B. C. Yang, J. C. Li, T. C. He

Proceedings Volume 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment; 72833T (2009) https://doi.org/10.1117/12.828791
Event: AOMATT 2008 - 4th International Symposium on Advanced Optical Manufacturing, 2008, Chengdu, Chengdu, China

Abstract

Cracks widely exist in material and the interaction among cracks plays an important role in the damage process of material. It is necessary, therefore, to pay much attention to the strain field of collective crack region. The elastic field for the region which contains collective cracks is different from that of the region without inclusions due to the existence of collective cracks. The variation of elastic field demonstrates the interaction among cracks. Different kinds of cracks are prefabricated on PMMA plates by mechanical fatigue or laser cutting in this paper. In order to measure the strain field of transparent plate under applied load, a digital real-time holographic measurement system developed by us is used and the holograms are reconstructed for different kinds of cracks with the help of this system. The shielding effect and amplification effect can be easily observed with the help of the magnitude and distribution of fringe in holograms. It can be seen from the hologram that distribution of elastic field is much different for different kinds of crack configures. It can be concluded from the distribution and the magnitude of interference fringes that the different interaction effect exists for elliptical holes and cracks at the same equivalent distance. The interference fringes always originate from the crack tip and spread to the up and down sides of crack with the increase of applied load. That means the originating position is the highest strain position. It is very helpful for us to determine the interference fringes level and the dangerous position for a complicate specimen. When the distance among cracks are not very close, the amplification effect among cracks will mainly lead to high strain field, vary the propagation path of crack and propel the connection among cracks. There exists gradient strain stripe among the elliptical holes. This will vary the emergence and the propagation of crack. The measurement results are also compared well with those obtained by numerical computation.

Citation Download Citation

R. X. Guo, H. T. Xia, Z. B. Fan, B. C. Yang, J. C. Li, and T. C. He "Research on collective cracks' strain field with digital real-time holography", Proc. SPIE 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 72833T (20 May 2009); https://doi.org/10.1117/12.828791

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