Topic
Fractography
About: Fractography is a research topic. Over the lifetime, 5043 publications have been published within this topic receiving 86068 citations.
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TL;DR: In this article, the authors used modified wedge-opening-loading (WOL) specimens to investigate the susceptibility of bainite/martensite dual-phase high strength steel to hydrogen embrittlement.
Abstract: It is very imperative to improve delayed fracture properties of high strength steel, which may enlarge its usage. The published literature shows that the susceptibility to hydrogen embrittlement of a novel 1 500 MPa bainite/martensite dual-phase high strength steel is inferior to that of conventional quench-tempered high strength steel. The stress corrosion cracking (SCC) in a 3.5% NaCl solution for novel 1 500 MPa bainite/ martensite dual-phase high strength steel was investigated in this paper by using modified wedge-opening-loading (WOL) specimens. The experimental results show that KISCC for novel 1 500 MPa bainite/martensite dual-phase high strength steel is larger than 50 MPa·m1/2, exceeding conventional high strength steel. Its crack growth rate (da/dt)II is about 1×10−5 mm/s, which is less than that of conventional high strength steel. Hydrogen trapping phenomena in the steel were investigated by electrochemical permeation technique. The lath boundaries and stable retained austenite are beneficial hydrogen trap, slowing down the segregation of hydrogen on the crack tip, hence KISCC increases and crack growth rate decreases.
45 citations
TL;DR: In this article, the failure mechanism and interlayer microstructure of aerospace-grade structural composites reinforced with thin veils of carbon nanotube produced using an industrialised spinning process were studied.
Abstract: The introduction of nanostructured interlayers is one of the most promising strategies for interlaminar reinforcement in structural composites. In this work, we study the failure mechanism and interlayer microstructure of aerospace-grade structural composites reinforced with thin veils of carbon nanotube produced using an industrialised spinning process. Samples of unidirectional carbon fiber/epoxy matrix composites interleaved with different composition CNT veils were prepared using hot press method and tested for interlaminar fracture toughness (IFT), measured in Mode-I (opening) and Mode-II (in-plane shear), and for interlaminar shear strength (ILSS), evaluated by the short beam shear (SBS) test. The crack propagation mode could be directly determined through fractography analysis by electron microscopy and resin/CNT spatial discrimination by Raman spectroscopy, showing a clear correlation between interlaminar reinforcement and the balance between cohesive/adhesive failure mode at the interlayer region. Composites with full resin infiltration of the CNT veils give a large increase of Mode II IFT (88%) to 1500 J/m2 and a slight enhancement of apparent interlaminar shear strength (6.5%), but a decrease of Mode I IFT (−21%). A toughening factor, defined as the relative increase in toughness per interleaf-to-ply thickness ratio, give a record-high value of 15.8 for Mode II IFT. The results help establish the role of interlayer infiltration, interlaminar crossings and formation of a carbon fiber bridgings, for interlaminar reinforcement with interleaves.
45 citations
TL;DR: In this article, the effects of corrosion on the high cycle fatigue (HCF) strength of a high mechanical strength martensitic stainless steel (X12CrNiMoV12-3) that is used in aeronautic applications were addressed.
45 citations
TL;DR: In this paper, high-cycle fatigue tests were conducted on specimens machined from 50 sequentially cast instrument panels made from high-pressure die-cast (HPDC) AM60B magnesium alloy.
45 citations
TL;DR: In this paper, a fractographic study of delamination failures in a range of carbon fibre and glass fibre reinforced plastics has been performed, where fractographic features, including striations and matrix rollers, unique to fatigue failure, were identified on many of the mode II dominated specimens.
Abstract: A fractographic study of delamination failures in a range of carbon fibre and glass fibre reinforced plastics has been performed. Mode I (peel), mode II (shear), and mixed mode (I + II) interlaminar fracture surfaces, generated both statically and in fatigue, were examined. Intralaminar shear failures generated using a notched tension specimen were also studied. Fractographic features, including striations and matrix rollers, unique to fatigue failure, were identified on many of the mode II dominated specimens. As the mode I component of fracture was increased both the matrix rollers and striations were seen to diminish. While the features identified on the fatigue fracture surfaces enabled static fractures to be differentiated from fatigue failures, studies have shown that the use of these features for the determination of crack propagation directions and crack growth rates may be more limited. It appears that local variations in the stress state over the fracure surface tend to produce signific...
45 citations