PSI - Issue 2_B

Tomoya Kawabata et al. / Procedia Structural Integrity 2 (2016) 2772–2779 Kawabata et al/ Structural Integrity Procedia 00 (2016) 000–000

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4. Concluding remarks In this study, r p which is important part of CTOD calculation formula based on plastic hinge assumption is investigated with a final goal of establishment of the formula. 3D dynamic elasto-plastic FEM analysis for various a 0 / W conditions from 0.05 to 0.7 that was already validated by actual CTOD measurement by silicone casting

Table 2 Comparison of three methods for determination of r p Method Procedure advantage

Disadvantage

・ A little variation during the target loading range ･ Correspondence with actual deformation ･ Consistency from previous research which contributed to the first foundation of the formula.

Rotational deformation observation method

(a)

-

･ A lot of

Extended line drawing method Back calculation method using Edge displacement and CTOD

variation during the target loading range

(b)

･ A little variation during the target loading range

･ No physical background

(c)

method is used for deformation behaviour of three point bending specimen especially in mid-thickness plane which is important in the actual evaluation. Three methods for the determination of r p are investigated. Obtained result is listed below. 1) In every condition, it is clearly observed ligament area is rotationally deformed at a point. This can be the strong motivation for continuous use for plastic hinge type calculation formula in determination of CTOD. 2) It is also confirmed that under the a 0 / W of 0.2, deformation mode transit from rotation only in ligament to whole specimen rotation. 3) In method (a) where the actual coordination of rotational deformation is used, the r p is increased as the a 0 / W is decreased and close to 0.5 that is the neutral plane of pure bending in case of simple beam problem. Variation during the deformation is quite small this is advantageous point for establishment of calculation formula. 4) In method (b) where crack opening profile and its extended line is used, the r p is so varied during loading. Especially in case of small a 0 / W conditions under 0.2, the variation is significantly enlarged. This is thought to be because there are large amount of opening displacement in small a 0 / W condition due to transition to whole deformation mode. This method has been applied from the early date of set-up of CTOD philosophy because this is experimentally easy to conduct. 5) In method (c) where back-calculation method by known CTOD and V p is applied, r p are stable in targeted deformation level and especially by using coefficient f in which effect of YR is considered, r p is varied as a function only of a 0 / W . Reference Donato, G. H. B., Ruggieri, C., 2006. Estimation Procedures for J and CTOD Fracture Parameters Using Three-Point Bend Specimens 2006 International Pipeline Conference, Volume 3: Materials and Joining; Pipeline Automation and Measurement; Risk and Reliability, Parts A and B, Calgary, Alberta, Canada. Ingham, T. GR., Egan, D. Elliott, Harrison, TC., 1971. The effect of Geometry on the interpretation of COD test data, Inst. Mech. Engng. C54/71:200. Kawabata, T., Tagawa, T., Sakimoto, T., Kayamori, Y., Ohata, M., Yamashita, Y., Tamura, E., Yoshinari, H., Aihara, S., Minami, F., Mimura, H., Hagihara, Y., Proposal of a new CTOD calculation formula,Engineering Fracture Mechanics, accepted. Kayamori, Y., Inoue, T., Hagihara, Y., 2014. Plastic rotational factor calculation for shallow notched SE(B) specimen, Material Science Forum 783-786, 2322-2326. Kirk, M. T., Dodds Jr., R. H., J and CTOD Estimation Equations for Shallow Cracks in Single Edge Notch Bend Specimen Journal of testing evaluation 21, 223-238. Tagawa, T., Kayamori, Y., Ohata, M., Handa, T., Kawabata, T., Yamashita, Y., Tsutsumi, K., Yoshinari, H., Aihara, S., Hagihara, Y., 2010. Comparison of CTOD standards: BS 7448-Part 1 and revised ASTM E1290, Engineering Fracture Mechanics 77(2), 327-336. Tagawa, T., Kawabata, T., Sakimoto, T., Kayamori, Y., Ohata, M., Yamashita, Y., Tamura, E., Yoshinari, H., Aihara, S., Minami, F., Mimura, H., Hagihara, Y., 2014. Experimental measurements of deformed crack tips in different yield-to-tensile ratio steels, Engineering Fracture Mechanics 128, 157-170. Nishitani, H., Noguchi, H., Mori, K., 1986. Analysis of Single-Edge-Cracked Specimen under Three- or Four-Point Bending by Body Force Doublet Method, Trans.Japan Soc. Mech. Engrs., 52(474), 539.543. Shang-Xian Wu, S.X., Cotterell, B., Yiu-Wing Mai, 1988. Slip Line Solutions for Three-Point Notch-Bend Specimen, International Journal of Fracture 37, 13-29. Tanaka, H., Ando, K., Sakai, Y., Ogura, N., 1981. Brittle crack initiation from shallow notch and Hot strain embrittlement, The Society of Materials Science, Japan, Committee on Fracture Mechanics, Proceedings for Fracture Mechanics Symposium, 147-151. Tsukamoto, M., 1994. Effect of Initial Crack Length on Critical COD of Unstable Fracture with Stable Fibrous Crack Growth ･ Memoirs of the Faculty of Education, Kumamoto University. Natural science 43, 153-162.