Issue 38

T. Morishita et alii, Frattura ed Integrità Strutturale, 38 (2016) 289-295; DOI: 10.3221/IGF-ESIS.38.39 295 C ONCLUSIONS (1) The failure life in proportional and non-proportional loading tests can be correlated by a unique life curve in the stress region over the fatigue strength. (2) The fatigue strength in the circle loading test is lower than that in the push-pull and the rev. torsion loading tests. In the circle loading test; the remarkable roughness can be observed in comparison with those in the push-pull loading test at each equivalent stress range. The surface roughness leads to earlier crack initiations and reducing fatigue strength. (3) In the circle loading test; non-proportional strain range tends to overestimate failure life in the high cycle fatigue region because the effect of non-proportional loading becomes weak. (4) The modified non-proportional strain range is the suitable strain parameter for life evaluation independent on strain path and strain level. R EFERENCES [1] Nitta, A., Ogata, T., Kuwabara, K., The effect of axial-torsional straining phase on elevated-temperature biaxial low- cycle fatigue life in SUS304 stainless steel, Journal of the Society of Materials Science, 36 (1987) 376-382. [2] Doong, S.H., Socie, D.F., Robertson, I.M., Dislocation substructure and nonproportional hardening, Journal of Engineering Materials and Technology, 112 (1990) 456-464. [3] Doong, S.H., Socie, D.F., Constitutive modeling of metals under nonproportional cyclic loading, Journal of Engineering Materials and Technology, 113 (1991) 23-30. [4] Itoh, T., Sakane, M., Ohnami, M., Ameyama, K., Effect of stacking fault energy on cyclic constitutive relation under non-proportional loading, Journal of the Society of Materials Science, 41 (1992) 1361-1367. [5] Wang, C.H., Brown, M.W., A path-independent parameter for fatigue under proportional and non-proportional loading, Fatigue & Fracture of Engineering Materials & Structures, 16 (1993) 1285-1298. [6] Itoh, T., Sakane, M., Ohnami, M., Socie, D.F., Non-proportional low cycle fatigue criterion for type 304 stainless steel, Journal of Engineering Materials and Technology, 117 (1995) 285-292. [7] Itoh, T., Nakata, T., Sakane, M., Ohnami, M., Nonproportional low cycle fatigue of 6061 aluminum alloy under 14 strain paths, European Structural Integrity Society, 25 (1999) 41-54. [8] Socie, D.F., Marquis, G.B., Multiaxial Fatigue, Society of Automotive Engineers International, (2000) 129-339. [9] Itoh, T., Sakane, M., Hata, T., Hamada, N., A design procedure for assessing low cycle fatigue life under proportional and non-proportional loading, International Journal of Fatigue, 28 (2006) 459-466. [10] Itoh, T., Sakane, M., Ozaki, T., Determination of strain and stress ranges under cyclic proportional and non- proportional loading, Journal of the Society of Materials Science, 60 (2011) 88-93. [11] Itoh, T., Yang, T., Material dependence of multiaxial low cycle fatigue lives under non-proportional loading, International Journal of Fatigue, 33 (2011) 1025-1031. [12] Itoh, T., Fukumoto, H., Hagi, H., Itoh, A., Saitoh, D., Evaluation of multiaxial low cycle fatigue strength for Mod.9Cr-1Mo steel under non-proportional loading, Journal of the Society of Materials Science, 62 (2013) 110-116. [13] Chamat, A., Azari, Z., Jodin, Ph., Gilgert, J., Dominiak S., Influence of the transformation of a non-proportional multiaxial loading to a proportional one on the high cycle fatigue life, International Journal of Fatigue, 30 (2008) 1189-1199. [14] Pejkowski, L., Skibicki, D., Sempruch, J., High-cycle fatigue behavior of austenitic steel and pure copper under uniaxial, proportional and non-proportional loading, Journal of Mechanical Engineering, 60 (2014) 549-560. [15] Morishita, T., Liu, S., Itoh, T., Sakane, M., Kanayama, H., Sakabe, M., Takeda, N., Fatigue failure life of SS400 steel under non-proportional loading in high cycle region, Advanced Materials Research, 891-892 (2014) 1385-1390. [16] Manson, S.S., Halford, G.R., Practical implementation of the double linear damage rule and damage curve approach for treating cumulative fatigue damage, International Journal of Fracture, 17 (1981) 169-172.