Fatigue & Fracture of Engineering Materials & Structures 

About: Fatigue & Fracture of Engineering Materials & Structures is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Fracture mechanics & Crack closure. It has an ISSN identifier of 1460-2695. Over the lifetime, 4576 publications have been published receiving 101774 citations. The journal is also known as: lethargy & fatigue (biological phenomena).

A critical plane approach to multiaxial fatigue damage including out-of-phase loading

Abstract: — A modification to Brown and Miller's critical plane approach is proposed to predict multiaxial fatigue life under both in-phase and out-of-phase loading conditions. The components of this modified parameter consist of the maximum shear strain amplitude and the maximum normal stress on the maximum shear strain amplitude plane. Additional cyclic hardening developed during out-of-phase loading is included in the normal stress term. Also, the mathematical formulation of this new parameter is such that variable amplitude loading can be accommodated. Experimental results from tubular specimens made of 1045 HR steel under in-phase and 90° out-of-phase axial-torsional straining using both sinusoidal and trapezoidal wave forms were correlated within a factor of about two employing this approach. Available Inconel 718 axial-torsional data including mean strain histories were also satisfactorily correlated using the aforementioned parameter.

The role of T-stress in brittle fracture for linear elastic materials under mixed-mode loading

Abstract: The purpose of this paper is to revisit the maximum tensile stress (MTS) criterion to predict brittle fracture for mixed mode conditions. Earlier experimental results for brittle fracture of polymethylmethacrylate (PMMA) using angled cracked plates are also re-examined. The role of the T-stress in brittle fracture for linear elastic materials is emphasized. The generalized MTS criterion is described in terms of mode I and II stress intensity factors, K I and K II and the T-stress (the stress parallel to the crack), and a fracture process zone, r c . The generalized MTS criterion is then compared with the earlier experimental results for PMMA subjected to mixed mode conditions. It is shown that brittle fracture can be controlled by a combination of singular stresses (characterized by K) or non-singular stress (T-stress). The T-stress is also shown to have an influence on brittle fracture when the singular stress field is a result of mode II loading.

A non‐linear continuous fatigue damage model

Abstract: — -A non-linear cumulative fatigue damage model proposed previously is applied to different steels and various loading situations, including two-level tests and block-programs. Its ability to describe all the main features of fatigue damage and the ease of its practical use for engineers are discussed and several examples cited. The relationship with other formulations are pointed out together with the main advantages of the proposed model. A generalization is proposed for both cyclic temperature and multiaxial loading conditions.

There is no infinite fatigue life in metallic materials

Abstract: Generally, the shape of the S-N curve beyond 10 7 cycles is unknown except in some statistical approaches, and this is also true for the fatigue limit. In the case of a statistical approach, the standard deviation applied to the average fatigue limit is certainly not the best way to reduce the risk of rupture in fatigue. Only the exploration of the life range between 10 6 and 10 10 cycles will create a safer basis for modelling. Today, some piezoelectric fatigue machines are very reliable, capable of producing 10 10 cycles in less than 1 week. We based our research on accelerated fatigue tests which were performed at 20 kHz in the gigacyclic fatigue regime in order to study several typical alloys from the aeronautical and space industries.

Factors influencing the mechanism of superlong fatigue failure in steels

Abstract: When the fatigue life N f of a specimen of 10 mm in thickness is longer than 10 8 cycles, the average fatigue crack growth rate is much less than the lattice spacing (∼0.1 A or 0.01 nm) that is 10 -11 to 10 -12 m/cycle. In the early stage of the fatigue process, the crack growth rate should be much less than the average growth rate, and accordingly we cannot assume that crack growth occurs cycle by cycle. In this paper, possible mechanisms for extremely high cycle fatigue are discussed. Of some possible mechanisms, a special focus was put on a newly found particular fatigue fracture morphology in the vicinity of the fracture origin (non-metallic inclusions) of a heat-treated alloy steel, SCM435, which was tested to N ≥ 10 8 . The particular morphology observed by SEM and AFM was presumed to be influenced by the hydrogen around inclusions. The predictions of the fatigue limit by the √area parameter model are ∼ 10% unconservative for a fatigue life of N f = ∼10 8 , though it successfully predicts the conventional fatigue limit defined for N = 10 7 . Thus, the fatigue failure for N ≥ 10 8 is presumed to be caused by a mechanism which induces breaking or releasing of the fatigue crack closure phenomenon in small cracks. In the vicinity of a non-metallic inclusion at the fracture origin, a dark area was always observed inside the fish-eye mark for those specimens with a long fatigue life. Specimens with a short fatigue life of N f = ∼10 5 do not have such a dark area in the fish-eye mark. SEM and AFM observations revealed that the dark area has a rough surface quite different from the usual fatigue fracture surface in a martensite lath structure. Considering the high sensitivity of high-strength steels to a hydrogen environment and the high hydrogen content around inclusions, it may be concluded that the extremely high cycle fatigue failure of high-strength steels from non-metallic inclusions is caused by environmental effects, e.g. hydrogen embrittlement coupled with fatigue.