Relation between the Betti Number of Fatigue Fracture Surfaces and Stress Intensity Factors of Low Carbon Steel (JIS, S45C)

The study of fracture surfaces of materials is very important to understand failures in engineering elements, especially in structural products. However, it is not easy to evaluate fatigue fracture surfaces by using ordinary image analysis techniques. In this paper, we propose a new analyzing method to evaluate fatigue fracture surfaces from a view point of Homology.

A History of the Fractography of Brittle Materials

The evolution of the science of fractography of brittle materials initially was driven by failure analysis problems. Early analyses focused on general patterns of fracture and how they correlated to the loading conditions. Many early documents are simply descriptive, but the curiosity of some key scientists and engineers was aroused. Scientific or engineering explanations for the observed patterns gradually were developed. Advances in microscopy and flaw based theories of strength and fracture mechanics led to dramatic advances in the state of the art of fractographic analysis of brittle materials. Introduction: This author was drawn backwards in time as he researched the current state of the art of fractographic analysis of brittle materials for his fractography guide book.[ ] Others have written about how the fractographic analysis of metals evolved (e.g., [ , , , ]), but there is no analogue for ceramics and glasses. The key scientists, engineers, and analysts who contributed to our field are shown in Fig. 1. Other work done by industry workers who were unable or loathe to publish is now lost, inaccessible, forgotten, or even discarded. It is the goal of this paper to review the key publications and mark the noteworthy advances in the field. Some deem fractography as the study of fracture surfaces, but this author takes a broader view. Fractography is the means and methods for characterizing fractured specimens or components and, for example, a simple examination of the fragments and how they fit together to study the overall breakage pattern is a genuine fractographic analysis.

Fractographic Studies of Sapphire Fibers Using Laser Scanning Confocal Microscopy

Laser scanning confocal microscopy (LSCM) is a microscopic technique which allows for height discrimination. The ability to gather 3D data, along with adequate resolution (around 400 nm), makes the technique suitable for fractography; however, its applications in this area are not sufficiently explored. In this work, LSCM and SEM are applied to the study of fracture surfaces in sapphire and ruby fibers submitted to tensile stress in high-temperature conditions. The obtained qualitative and quantitative information demonstrates the validity of LSCM as a fractographical technique, allowing for clear identification of fractographical features and providing novel insight in the phenomenon of subcritical crack growth (SCG).

Characterisation of Portland Cement Hydration by Electron Optical Techniques

ABSTRACTIn the past the application of electron microscopy to cement hydration has been limited largely to the study of fracture surfaces in SEM, of ground cement in TEM and of polished sections in EMPA. Consequently the microstructure of bulk cement pastes is, as yet, ambiguous.The present work shows how techniques not previously used in the study of cement, an environmental cell on HVEM, preparation of ion beam thinned foils for STEM and BEI of polished surfaces in SEM, can give a more detailed view of the development of morphology in hydrating cement. Using a combination of electron optical techniques together with other methods a detailed characterisation of cement hydration can be made.

Paper 4: Electron Optical Techniques of Failure Investigation

Fractography, the study of fracture surfaces, is useful in failure investigations as the topography and characteristic markings of such surfaces are indicative of the mechanism of fracture which operated during the initiation of failure and crack propagation. Owing to the low depth of focus of the optical microscope, interpretation of some fracture surfaces may be difficult. The microscopic topography, and its relation to the causes and basic mechanisms of fracture, may be conveniently studied by electron microfractography using non-destructive replica methods. Replicas may be taken from selected areas of the fracture surface of large, unwieldy engineering components. Complementary electron optical techniques such as electron diffraction, scanning electron microscopy, and extraction replicas are used where possible to obtain additional fine-scale information of use in the elucidation of failure mechanisms. An explanation of the various techniques and examples of their use in the work of the National Engineering Laboratory in failure investigations is given. The investigations involve fatigue, brittle fracture, corrosion fatigue, stress corrosion, welding problems, and surface phenomena.