Early detection of crack initiation sites in TiAl alloys during low-cycle fatigue at high temperatures utilizing digital image correlation

In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.

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Experimental study on crack initiation and propagation of wood with LT-type crack using digital image correlation (DIC) technique and acoustic emission (AE)

Wood Science and Technology ◽

10.1007/s00226-020-01252-8 ◽

2021 ◽

Author(s):

Juncheng Tu ◽

Dong Zhao ◽

Jian Zhao ◽

Qi Zhao

Keyword(s):

Experimental Study ◽

Acoustic Emission ◽

Digital Image Correlation ◽

Crack Initiation ◽

Digital Image ◽

Image Correlation ◽

Crack Initiation And Propagation ◽

Initiation And Propagation ◽

Dic Technique

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Crack initiation and failure development in bimrocks using digital image correlation under dynamic load

Theoretical and Applied Fracture Mechanics ◽

10.1016/j.tafmec.2020.102688 ◽

2020 ◽

Vol 109 ◽

pp. 102688 ◽

Cited By ~ 1

Author(s):

Mansour Sharafisafa ◽

Zeinab Aliabadian ◽

Luming Shen

Keyword(s):

Digital Image Correlation ◽

Crack Initiation ◽

Digital Image ◽

Dynamic Load ◽

Image Correlation

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Experimental Study of Fatigue Crack Initiation and Strain Evolution around a Micro-Void by In Situ SEM and Digital Image Correlation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.754.75 ◽

2017 ◽

Vol 754 ◽

pp. 75-78 ◽

Cited By ~ 1

Author(s):

De Qiang Wang ◽

Ming Liang Zhu ◽

Fu Zhen Xuan

Keyword(s):

Fatigue Crack ◽

Digital Image Correlation ◽

Crack Initiation ◽

Digital Image ◽

Early Stage ◽

Fatigue Crack Initiation ◽

Image Correlation ◽

Dominant Factor ◽

Strain Evolution

Fatigue crack initiation stage occupies a large proportion of total fatigue life in modern engineering materials and structures which are often designed under lower service loading conditions. In this paper, the fatigue crack initiation behavior from a micro-void in a small-scale specimen was studied in-situ in SEM. Surface morphologies were monitored in-situ and images were taken during interrupted tests at selected number of cycles, and displacement and strain map around the void was calculated based on digital image correlation (DIC) technique. The results indicated that the strain evolution near the micro-void could be divided into stages, before crack initiation. The strain increasing rate was fast in the early stage and slower in the second stage. A critical cyclic strain value for fatigue crack initiation from the micro-void was obtained around 9%, and was believed to be the dominant factor for early stage of fatigue damage.

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