Issue 41

M. Sakane et alii, Frattura ed Integrità Strutturale, 41 (2017) 16-23; DOI: 10.3221/IGF-ESIS41.03 23 C ONCLUSIONS (1) Strain multiaxiality dependence of cracking direction in tension-torsion multiaxial low cycle fatigue is discussed. The transition of cracking direction occurred at the principal strain range of about  0.70 for low alloy steels of SUS 304, SUS 316 and CrMoV and directionally solidified superalloy of Mar-M247 and Rene’80. Only conventional cast superalloy of Inconel 738 showed shear cracking in all principal strain ratios. (2) The specimen with the principal cracking showed slightly smaller low cycle fatigue life than that with the shear cracking fatigued at the same von Mises strain amplitude. (3) Notches and precracks changed the cracking direction in torsion low cycle fatigue. The specimen with large through hole and through precrack yielded principal cracks in the testing condition that the smooth specimen yielded shear crack. However, the specimen with a small through hole and a surface hole had a shear crack. (4) The strain ranges at which macro cracks transit the direction between the shear direction and the principal direction corresponded to the transition strain range at which the average crack length increase. (5) The aspect ratio of the shear crack was smaller compared with the principal crack. Finite element analysis revealed that the strain energy release of the shear crack was larger at high strain ranges but that of the principal crack was larger at low strain ranges. R EFERENCES [1] Forsyth, P.J.E., A two stage process of fatigue crack growth, Proc Crack Propag. Symp Cranfield, (1961) 74–91. [2] Sakane, M., Ohnami, M., Sawada, M., Fracture modes and low cycle biaxial fatigue life at elevated temperature, J. Eng. Mater. Technol., 109 (1987) 236–243. [3] Brown, M.W., Miller, K.J., Initiation and growth of cracks in biaxial fatigue, Fatigue Fract. Eng. Mater. Struct., 1 (1979), 231–246. [4] Sakane, M., Ohnami, M., Sawada, M., Biaxial low cycle fatigue of unaged and aged 1Cr-1Mo-1/4V steels at elevated temperature, J. Eng. Mater. Technol., 113 (1991) 244–253. [5] Nitta, A., Ogata, T., Kuwabara, K., Relationship between fracture mode and fatigue life under biaxial loading at 550  C in SUS 304 Stainless Steel, J. Soc. Mater. Science, Japan, 37 (1988) 334–339. [6] Cox, H.L., Field, J.E., The initiation and propagation of fatigue cracks in mild steel pieces of square section, Aeronaut. Q., 4 (1954) 1–18. [7] Isobe, N., Multiaxial creep-fatigue life evaluation for Inconel 738LC nickel base super alloy, Master Theses Ritsumeikan Univ., 1992. [8] Hirose, T., Multiaxial creep-fatigue life evaluation for Rene80 directionally solidified nickel base super alloy, Master Theses Ritsumeikan Univ., 1993. [9] Shirafuji, N., Shimomizuki, K., Sakane, M., Ohnami, M., Tension-torsion multiaxial low cycle fatigue of Mar- M247LC directionally solidified superalloy at elevated temperature, J. Eng. Mater. Technol., 120 (1998) 57–63. [10] Ohji, K., Ogura, K., Harada, S., Ohyama, S., Torsional fatigue behavior of anisotropic rolled steel plate in middle and high cycle fatigue ranges, J. Soc. Mater. Scinece, Japan, 25 (1976) 836–841. [11] Sakurai, S., Fukuda, Y., Isobe, N., Kaneko, R., Micro-crack growth and life prediction of a 1CrMoV steel under axial- torsional low cycle fatigue at 550  C, Fatigue Fract. Eng. Mater. Struct., 17 (1994) 1271–1279. [12] Sakane, M., Ohnami, M., Hamada, N., Biaxial low cycle fatigue for notched, cracked, and smooth specimens at high temperatures, J. Eng. Mater. Technol., 110 (1988) 48–54. [13] Ogata, T., Nitta, A., Blass, J.J., Propagation behavior of small cracks in 304 stainless steel under biaxial low-cycle fatigue at elevated temperature, in: D.L. McDowell, J.R. Ellis (Eds), Advances in Multiaxial Fatigue, ASTM STP 1191, (1993) 313–325. [14] Sawada, M., Bannai, K., Sakane, M., Crack propagation direction of type 304 stainless steel in torsion low cycle fatigue, J. Soc. Mater. Science, Japan, 54 (2005) 615–621. [15] Makabe, C., Socie, D.F., Crack growth mechanism in precracked torsional fatigue specimens, Fatigue Fract. Eng. Mater. Struct., 24 (2001) 607–615. [16] Bannantine, J, Socie, DF., Observations of cracking behavior in tension and torsion low cycle fatigue, in: H.D. Solomon, G.R. Halford, J.R. Kaisand, B.N. Leis (Eds), Low Cycle Fatigue, ASTM STP 942 (1988) 899–921. [17] Hiyoshi, N., Sakane, M., Nose, H., Crack propagation direction under reversed torsion test for SUS304 stainless/SCM435 steels and Al 1050 alloy, Trans. Japan Soc. Mech. Eng. A, 68 (2002) 81–87.