Kinetics of fatigue failure of AT3 titanium alloy in air, distilled water, and a 3.5% NaCl aqueous solution

Ботвина, Л. Р.; Yarema, S. Ya.; Ostash, О. P.; Polutranko, I. B.

doi:10.1007/bf00721329

Cited by 5 publications

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“…For this reason, the features of the structure of fatigue grooves characterize the growth rate of microcracks, but they cannot directly define the growth rate of a macrocrack. That is why the distance between grooves, generally speaking, is not in agreement with the growth rate of a macrocrack [13,14]. Moreover, it is clear why the boundaries of the region corresponding to the conditional jump of the macrocrack, in fact, cannot be recorded on microfractograms.…”

Section: Model Of Growth Of a Fatigue Maerocrackmentioning

confidence: 91%

A unified model of initiation and growth of fatigue macrocracks. part 3. stage of growth of a macrocrack

Ostash¹,

Panasyuk²

1999

Mater Sci

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From a common viewpoint, fatigue fracture of materials is simulated by the process of initiation of an initial macrocrack of length a i = d* (d* is the constant of the material), which is successively (stepwise) repeated at the stage of its growth. As a result, the diagram "range of local stresses -period of initiation of an initial macrocrack" or "range of local strains -period of initiation of an initial macrocrack," which was determined for notched specimens, can be used for the construction of the diagram "growth rate of a macrocrack -range of the stress intensity factor" or "growth rate of a macrocrack -range of local strains," respectively, if the crack is presented as a sharp notch with effective rounded radius Peff = d* of the tip.For estimation of the endurance of a structural material, the endurance limits ~R and ~g of smooth and notched specimens, respectively, and the threshold of cyclic crack resistance Kth of specimens with a macrocrack are the most widespread characteristics. It often occurs that these characteristics correlate with other mechanical and physical parameters of materials in different ways. The reason for this lies in the fact that the characteristics are determined at various stages of fatigue fracture on the basis of fracture criteria for the limiting state of macro-or microvolumes of the material. At present, the opinion exists that the regularities of the processes of initiation and growth of a macrocrack are significantly different and, for this reason, are separately studied. To our mind, the process of fatigue of materials (the initiation of a macrocrack and its propagation) can be studied from a common viewpoint by using unified approaches and parameters and by interpreting the growth of a fatigue macrocrack as the stepwise repeated act of its initiation.In this context, it is worth noting the models of growth of fatigue cracks, which are based on the assumption that a crack can be regarded as a sharp notch [1, 2] with a rounded radius p = P* of the tip, where p* is the constant of the material [2]. The growth of a fatigue macrocrack is considered as a sequence of acts of its reinitiation in the vicinity of the tip of a sharp notch. This growth is described by the parameters that were found with smooth and notched specimens by using the well-known Neuber and Manson-Coffin approaches [1,2]. However, the parameter p* has no clear physical meaning, and methods for direct determination of its value are unknown up to now [2]. The problem of initiation of fatigue cracks was not considered in the works mentioned above.Let us postulate that the formation rate of the unit surface of a fatigue crack is a single-valued function of local strain both in the process of initiation of a macrocrack and in the course of its growth. From the viewpoint of the unified approach to initiation and propagation of fatigue macrocracks, investigations based on the above statement are of high priority. The structure of this function was established at the stage of growth of a macrocrack [3]. However, it w...

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Section: Model Of Growth Of a Fatigue Maerocrackmentioning

confidence: 91%