A Simple Theory for Low Cycle Multiaxial Fatigue

The biaxial fatigue behaviour of two batches of a structural steel, termed isotropic and anisotropic batches, is examined. Tests were carried out using thin-walled hollow specimens subjected to axial load and internal and external pressure. The fatigue life of the isotropic batch is found to be about two to three times greater than the fatigue life of the anisotropic material. The ratio however is found to be dependent on the degree of biaxiality. Three equivalent strain parameters were used to correlate the fatigue lives, octahedral strain, Brown-Miller and Lohr-Ellison parameters. The difference between the theories are compared and the relation between the shear strain orientation and failure is discussed. NOMENCLATURE A, a = Manson-Coffin intercept and exponent B, p = Basquin intercept and exponent C = material coefficient in Brown-Miller and Lohr-Ellison parameters R, = cyclic strain ratio, minimum/maximum N, Nf = number of cycles and number of cycles to failure t, e, p = total, elastic and plastic notations z, r, 0 = axial, radial and tangential notations Au, A&, Ay = strain, stress and shear ranges 4 = surface principal strain ratio, smaller/larger v = Poisson's ratio E~, e2, = principal strains ( E~ > E~ e3) ymax = maximum shear strain y* =maximum shear strain on a plane-inclined 45" to the surface E, = normal strain on the ymax plane E,* = normal strain on the y* plane yoct = shear strain on the octahedral plane

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“…5. This is in agreement with earlier observations [8] supporting the hypothesis that c1 is independent of biaxiality [ 111.…”

Section: Correlation Of Datasupporting

confidence: 94%

High Strain Biaxial Fatigue of a Structural Steel

Shatil

Smith

Ellison

1994

Fatigue Fract Eng Mat Struct

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“…proportional (Kandil et al, 1982;Wang and Yao, 2004) − (1993) − + − Random, non-proportional (Smith et al, 1976;Wang and Brown, 1993;Kim and Park, 1999) − 5 Lohr and Ellison (1980) − + − Cyclic, proportional (Lohr and Ellison, 1980) − 6 Socie et al (1985) − + − Cyclic, non-proportional (Socie et al, 1985;Socie 1987)…”

Section: Discussionmentioning

confidence: 97%

A Review of Critical Plane Orientations in Multiaxial Fatigue Failure Criteria of Metallic Materials

2005

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The paper presents a review of multiaxial fatigue failure criteria based on the critical plane concept. The criteria have been divided into three groups, according to the fatigue damage parameter used in the criterion, i.e. (i) stress, (ii) strain and (iii) strain energy density criteria. Each criterion was described mainly by the critical plane orientation. Multiaxial fatigue criteria based on the critical plane concept usually apply different loading parameters in the critical plane whose orientation is determined by (a) only shear loading parameters (crack Mode II or III), (b) only normal loading parameters (crack Mode I) or sometimes (c) mixed loading parameters (mixed crack Mode). There are also criteria based on few critical plane orientations and criteria based on critical plane orientations determined by a weighted averaging process of rotating principal stress axes.

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“…For most metals and alloys, m p = 0.5, so the criterion becomes [41]. Lohr and Ellison investigated the biaxial fatigue behavior of tubular specimens under tension and torsion.…”

Section: Multiaxial Fatigue Criterion Based On Critical Plane Methodsmentioning

confidence: 98%