Search Results for quantitative fractography

Quantitative fractography (QF) is the examination and characterization of fracture surfaces of failed or broken-open components and specimens. This article provides examples of the application of QF to evaluate real-life fatigue failures and also a comprehensive guideline chart for detecting and measuring fatigue striations and progression markings, with examples.

The development of quantitative fractography (QF) parameters basically requires topological data of a fracture surface that can be derived from the stereological analysis of multiple projected scanning electron microscope (SEM) images; the profilometry-based techniques that measure the fracture surface profile along x-y sections of a fracture surface from metallographic sections or nondestructive techniques; and the three-dimensional reconstruction of the fracture surface topology using imaging methods such as stereo SEM imaging and confocal scanning laser microscopy. These three general methods of assessing fracture surface topology are reviewed in this article.

This article discusses several examples of fatigue load histories that intentionally create artificial fracture-surface markings during testing such that they are measurable by post-test quantitative fractography (QF). It reviews a number of methods for providing fatigue fracture-surface markers to aid QF of fatigue crack growth (FCG). These methods are based on load changes, including reordering the basic load histories and/or adding loads to them. The article also provides some guidelines for obtaining recognizable FCG markers for a variety of load histories and crack-growth regimes for coupons, components, and, particularly, full-scale fatigue tests.

The quantitative characterization of fracture surface geometry, that is, quantitative fractography, can provide useful information regarding the microstructural features and failure mechanisms that govern material fracture. This article is devoted to the fractographic techniques that are based on fracture profilometry. This is followed by a section describing the methods based on scanning electron microscope fractography. The article also addresses procedures for three-dimensional fracture surface reconstruction. In each case, sufficient methodological details, governing equations, and practical examples are provided.

This article describes the fatigue properties of particle-reinforced metal-matrix composites (PR-MMCs) in terms of mechanisms of crack initiation, fatigue life, and fatigue crack growth. It reviews specimen preparation and microscopic procedures that are used in fatigue testing of MMCs. It also describes the evaluation of the long fatigue crack growth behavior of MMCs by using the test methods and specimens that are used for unreinforced metallic alloys. Fractography of MMCs under plane-strain conditions is also described with information on the observed features of MMC fatigue fracture surfaces and their observation methods.

The principal objective of quantitative fractography is to express the characteristics of features in the fracture surface in quantitative terms, such as the true area, length, size, spacing, orientation, and location. This article provides a detailed account of the development of more quantitative geometrical methods for characterizing nonplanar fracture surfaces. Prominent techniques for studying fracture surfaces are based on the projected images, stereoscopic viewing, and sectioning. The article provides information on various roughness and materials-related parameters for profiles and surfaces. The applications of quantitative fractography for striation spacings, precision matching, and crack path tortuosity are also discussed.

This article reviews the historical development of fractography, from the early studies of fracture appearance dating back to the sixteenth century, and including the development of microfractography in the middle of the 20th century, to the current state-of-the-art work in electron fractography and quantitative fractography.

The purpose of fractography is to analyze fracture features and attempt to relate the topography of the fracture surface to the causes and/or basic mechanisms of fracture. This article reviews the historical development of fractography, from the early studies of fracture appearance dating back to the sixteenth century to the state-of-the-art work in electron fractography and quantitative fractography. It also describes the applications and limitations of scanning electron microscope and transmission electron microscope.

This article discusses the fractal characteristics of fracture surfaces as a means for describing and quantifying irregular, complex curves and surfaces of fractured materials. It describes the important relationship between the profile and surface roughness parameters that yield the surface area of irregular fracture surfaces. The article reviews the experimental procedures required to obtain profiles and measurements that are made. In addition, fractal equations that linearize all the experimental data and provide constant fractal dimensions are presented in the article. Modified fractal dimensions that result from these analyses appear to possess some generality for natural irregular nonplanar surfaces and their profiles.

Failure analysis is a process of acquiring specified information regarding the appropriateness of the design of a part, the competence with which the various steps of its manufacture have been performed, any abuse suffered by it in packing and transportation, or the severity of service under which failure has occurred. Beginning with a discussion of the various stages of failure analysis of glass and ceramic materials, this article focuses on descriptive and quantitative fracture surface analysis techniques that are used in the examination of glass and surfaces created by fracture and the interpretation of the fracture markings seen on these surfaces. Details are provided for the procedures for locating fracture origins, determining direction of crack propagation, learning the sequence of crack propagation, deducing the stress state at the time of fracture, and observing interactions between crack fronts and inclusions, etc. A separate fractography terminology is provided in this article.

This article provides a summary of the concepts discussed in the articles under the Section “Failure Analysis” in ASM Handbook, Volume 21: Composites. Most of the information in this Section is geared toward organic-matrix composites, although there is some information on failure analysis and fractography of ceramic- and metal-matrix composites.

Scanning electron microscopy (SEM) has unique capabilities for analyzing fracture surfaces. This article discusses the basic principles and practice of SEM, with an emphasis on its applications in fractography. The topics include an introduction to SEM instrumentation, imaging and analytical capabilities, specimen preparation, and the interpretation of fracture features. SEM can be subdivided into four systems, namely, illuminating/imaging, information, display, and vacuum systems. The article also describes the major criteria and techniques of SEM specimen preparation, and the general features of ductile and brittle fracture modes.

This article presents a basic overview of technology-driven advances in the imaging of primarily metallic fracture surfaces. It describes various types of microscopes, including scanning electron, dual-beam, ion source, and transmission electron microscopes, and their capabilities. It also covers other useful hardware, such as computer-aided tomography (CAT) and micro-computer-aided tomography (micro-CAT) instruments. The article introduces some of the fracture image postprocessing methods and software, including image registration or alignment, focus stacking, Z-stacking, focal plane merging, and image stitching.