numero25

B. Moreno et alii, Frattura ed Integrità Strutturale, 25 (2013) 145-152; DOI: 10.3221/IGF-ESIS.25.21 151 Figure 8 : Superposition of the metal surface after being cleaned (i.e. with no paint) and vertical strain fields calculated by DIC after applying 33500 cycles. C ONCLUDING REMARKS rom the results obtained, the following conclusions can be drawn: - A new procedure based on Murakami’s ideas for enforcing the crack initiation at a specific location was successfully developed. - Electro-spray technique was effectively employed for producing a micro-speckle pattern that can be used by DIC technique combined with long-distance microscope to evaluate crack-tip displacement and strain fields. - Electro-spray technique for creating the speckle pattern required by DIC did not allow the monitoring of the crack length, since it obscures the crack. Better results could be obtained when monitoring the crack length by making the speckle paint film not continuous. However this would also imply a lower contrast and so further experiments are required to find a solution. A CKNOWLEDGEMENTS inancial support of Spanish Ministerio de Economía y Competitividad through grant reference DPI2012-33382 is greatly acknowledged. Experimental help by Mr F Sabarit is also much appreciated. R EFERENCES [1] ASTM E606 / E606M - 12 Standard test method for strain-controlled fatigue testing. (2012). [2] Murakami, Y., Metal Fatigue: effects of small defects and non metallic inclusions Oxford, UK: Elsevier, (2002) 35-56. [3] Sutton, M. A., McNeill, S. R., Helm, J. D., Chao, Y. J., Advances in two-dimensional and three-dimensional computer vision. In: Photomechanics, Topics in Applied Physics, Rastogi PK, editor., 77 (2000) 323-372. [4] Fonseca, J. Qd., Mummery,P. M. , Withers, P. J., Full-field strain mapping by optical correlation of micrographs acquired during deformation, Journal of Microscopy, 218(1) (2005) 9-21. [5] Yoneyama, S., Ogawa, T., Kobayashi, Y., Evaluating mixed-mode stress intensity factors from full-field displacement fields obtained by optical methods, Engineering Fracture Mechanics, 74 (2007) 1399-1412. [6] Roux, S., Hild, F., Stress intensity factor measurements from digital image correlation: post-processing and integrated approaches, International Journal of Fracture, 140 (2006) 141-157. [7] Lopez-Crespo, P., Shterenlikht, A., Patterson, E. A., Withers, P. J., Yates, J. R., The stress intensity of mixed mode cracks determined by digital image correlation, Journal of Strain Analysis for Engineering Design, (2008) 43. [8] Taylor, G. I., Disintegration of water drops in an electric field. Proceedings of the Royal Society – A, 280 (1964) 383- 397. [9] Deng, W., Gomez, A., Influence of space charge on the scale-up of multiplexed electrosprays, Journal of Aerosol Science, 38 (2007) 1062-1078. F F