Evaluation and visualization of multiaxial stress and strain states under non-proportional loading

Abstract

This paper presents a simple method of determining stresses and strains and a severity of loading history under non-proportional loadings with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. Based on the method, non-proportional stress and strain ranges are derived and applicability of the range to the life evaluation for low carbon steel under non-proportional random strain paths are discussed. The strain range taking account of intensity of loading path reducing life can be suitable parameter for multiaxial fatigue life evaluation under multiaxial non-proportional loading. This paper also shows a method of visually presenting the principal stress and strain that assists designers to understand the loading mode whether proportional or non-proportional under 3 dimensional (6 stress/strain components) multiaxial loading.

Evaluation of Multiaxial Low Cycle Creep-fatigue Life for Mod.9Cr-1Mo Steel under Non-proportional Loading

“…5(b), the failure life of CI-FF was about half of that of PP-FF, which is consistent with the results of previous studies. 17,18) This is due to the fact that in the CI test, the principal axes of both stress and strain are continuously rotated by one rotation during one cycle, which increases the number of active slip systems compared to the PP test, and consequently the number of cracks. [19][20][21][22][23] The life of CI-SS was comparable to that of CI-FF.…”

Analysis of multiaxial low cycle fatigue of notched specimens for type 316L stainless steel under non-proportional loading

“…This model has been applied widely to hollow cylinder smooth specimens made by different materials, and its accuracy was verified comparing the results from proportional and non-proportional loadings. The results were successfully synthesized in a factor two band which suggested a good estimation of fatigue life and an accurate interpretation of the factors involved in the proposed model [28,29]. Recently, Itoh et al [30,31] The model is well supported by original finite element analyses that consider the cyclic stress and strain curves obtained experimentally.…”

Creep-fatigue life evaluation of high chromium ferritic steel under non-proportional loading

“…In multiaxial low cycle fatigue tests, it has been reported that the large reduction in the failure life has a close relation with strain path and material. Itoh et al [8][9][10][11][12][13] proposed a non-proportional strain range  NP for life evaluation under nonproportional loading defined by…”