1,721,291 research outputs found
Influence of grain structure and slip planarity on fatigue crack growth in low alloying artificially aged 2xxx aluminium alloys
Full text linkThe fatigue crack growth behaviour under constant amplitude loading of three low alloying artificially aged 2xxx aluminium alloys with distinct microstructures is analysed. Fatigue crack growth tests show a correlation between fatigue performance and the occurrence of crack closure. Fractography and fracture surface measurements show that rougher surfaces give higher closure levels suggesting a dominating influence of RICC in these alloys. The relationship between the crack path and the microstructure, i.e. grain structure and slip planarity, is assessed semi-quantitatively. A criterion to evaluate the propensity for slip band formation is derived and reasonable correlation is found between the fatigue fracture behaviour of the three alloys and this criterion. <br/
Micromechanical aspects of fatigue in a MIG welded aluminium airframe alloy. Part 2. Short fatigue crack behaviour
No full textShort crack fatigue behaviour of a metal inert gas (MIG) welded 2024-T351 aluminium alloy has been studied in terms of crack initiation and propagation, and the microstructural features of the weld. Extensive crack initiation was noted within the weld fusion zone. Relatively small interdentritic defects are seen to be more damaging (in initiating cracks) than the larger gas bubble defects that exist in this region. Cracks were also seen to initiate within the weld heat affected zone where tensile residual stresses were found to be high, however, rapid crack growth and coalescence within the fusion zone is seen to dominate failure. Multiple crack interactions are seen to have a significant effect on failure up to relatively large crack lengths (of the order of the fusion zone width), enhancing the variability in short crack growth. Secondary electron and back-scattered electron imaging, in association with electron back-scattered diffraction (EBSD) mapping, were carried out on failed samples to assess the associated microstructural interactions
The influence of toughening-particles in CFRPs on low velocity impact damage resistance performance
Full text linkThe role of particle-toughening for increasing impact damage resistance in carbon fibre reinforced polymer (CFRP) composites was investigated. Five carbon fibre reinforced systems consisting of four particle-toughened matrices and one system containing no toughening particles were subjected to low velocity impacts ranging from 25 J to 50 J to establish the impact damage resistance of each material system. Synchrotron radiation computed tomography (SRCT) enabled a novel approach for damage assessment and quantification. Toughening mechanisms were detected in the particle-toughened systems consisting of particle–resin debonding, crack-deflection and crack-bridging. Quantification of the bridging behaviour, increase in crack path length and roughness was undertaken. Out of the three toughening mechanisms measured, particle systems exhibited a larger extent of bridging suggesting a significant contribution of this toughening mechanism compared to the system with no particle
Sinclair, I M, NX55025
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/417097Surname: SINCLAIR. Given Name(s) or Initials: I M. Military Service Number or Last Known Location: NX55025. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 47822.239791
Item: [2016.0049.49358] "Sinclair, I M, NX55025
Sinclair, I A D, NX53074
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/417096Surname: SINCLAIR. Given Name(s) or Initials: I A D. Military Service Number or Last Known Location: NX53074. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 37629.239790
Item: [2016.0049.49357] "Sinclair, I A D, NX53074
Fatigue of friction stir welded 2024-T351 aluminium alloy
No full textFatigue failure characteristics of friction stir welds in 13mm gauge 2024-T351 plate have been assessed. Failure occurred from either the weld region (nugget/flow arm) or from the material immediately surrounding the weld. Fatigue failure from the surrounding material was essentially conventional, initiating from large S-phase intermetallic particles and growing in a macroscopic mode I manner. Corresponding fatigue lives were seen to be comparable to parent plate and results previously reported for similar welds in thinner plate. Failure over the weld region was identified with discontinuities in the macroscopic flow pattern of the weld flow arm. Subsequent crack growth showed pronounced macroscopic crack deflection around the ‘onion ring’ structure of the weld nugget. The bands making up the onion rings were identified with variations in local hardness levels, consistent with a mechanical contribution to the crack deflection process
Investigation of the response to low velocity impact and quasi-static indentation loading of particle-toughened carbon-fibre composite materials
No full textThis work investigates damage caused by low velocity impact and quasi-static indentation loading in four different particle-toughened composite systems, and one untoughened system. For impact tests, a range of energies were used between 25 and 50 J. For QSI, coupons were interrupted at increasing loading point displacement levels from 2 to 5 mm to allow for monitoring of damage initiation and propagation. In both loading cases, non-destructive inspection techniques were used, consisting of ultrasonic C-scan and X-ray micro-focus computed tomography. These techniques are complemented with instrumentation to capture force–displacement data, whereby load-drops are associated with observed damage modes. Key results from this work highlight particular issues regarding strain-rate sensitivity of delamination development and an earlier onset of fibre fracture associated with particle-toughened systems. These issues, in addition to observations on the role of micro-scale events on damage morphology, are discussed with a focus on material development and material testing practices
Observations of damage development from compression-after-impact experiments using ex situ micro-focus computed tomography
No full textThe development of damage mechanisms leading up to compression-after-impact (CAI) failure is studied in particle-toughened and untoughened systems. Microfocus computed tomography (?CT) enabled non-destructive monitoring of the internal damage development in three-dimensions (3D) by taking scans after impact, after an application of near failure compression loads and after coupon failure. In combination with ?CT work, mechanical CAI testing and ultrasonic C-scans were conducted to determine the effect of the projected damage area on residual CAI strength and to complement the observations made from ?CT scans. The important role of the undamaged “cone” of material immediately under the impact site for out-of-plane sublaminate stability is identified. The implication of delamination growth into this region is discussed. It was found that where particle-toughened systems suppressed delamination growth into this region, greater residual CAI strength was maintained on a like-for-like projected damage are
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