Nickel-base superalloy 718 films have been sputter deposited to thicknesses of 20μm. These as-deposited films were single-phase nanocrystalline solid solutions, which possessed tensile strengths of ...1GPa but negligible ductility. Standard 718 aging heat treatments resulted in modest grain growth, atypical precipitation behavior, significant ductility, and impressive strengths at both ambient (2GPa at 25°C) and elevated (750MPa at 700°C) temperatures. The density of grain boundaries was shown to have a dramatic effect on the precipitation pathways of this alloy.
•Exceptional room temperature strength (2GPa) and ductility after aging•Sputtered superalloy had a similar composition as the target.•Film was essentially quenched from the vapor forming a solid solution.•Heat treatment resulted in unique precipitation pathways.•Small grain size contributed to mechanical properties and precipitation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The in-plane shear strengths (IPSS) of copy paper, filter paper, and sack paper were obtained from an asymmetric four-point bending (AFPB) test. Rectangular tabs of medium-density fibreboard (MDF) ...were bonded to the paper specimen. The length of the clearance between the tabs was varied, and the influence of the clearance on the IPSS value was investigated. The IPSS obtained from the AFPB test was compared with that obtained from a 35° off-axis tension (OAT) test, which was proposed in a previous study. The IPSS values obtained from the AFPB tests on the copy paper and sack paper were significantly lower than those obtained from the 35° OAT tests because of the localised buckling caused by the negative principal stress. In contrast, the IPSS values obtained from the AFPB and OAT tests on the filter paper were in agreement when the clearance length was >5 mm because the buckling effect was excluded.
The flow and failure behaviour of replicated pure aluminium foams in the presence of holes and notches is explored, varying the pore size and the notch depth or hole radius. Flat dog-bone tensile ...specimens containing a cylindrical hole, and cylindrical V-notched samples of 400
μm and 75
μm pore size microcellular aluminium were tested. Both pore size foams exhibit a notch strengthening effect, i.e. the peak failure stress increases as the depth of notches in cylindrical samples increases. In dog-bone samples, the presence of a hole ranging from 0 to 4
mm in diameter (in a sample 9
mm wide) does not affect the net section peak failure stress of the 75
μm foam while the 400
μm pore size foam exhibits a slight increase in net section failure stress as the hole diameter is increased to 2
mm. Plastic flow curves for notched and hole-containing samples are accurately predicted by a finite-element simulation based on the Deshpande–Fleck Deshpande VS, Fleck NA. J Mech Phys Solids 2000;48:1253–83 flow law, showing that the observed trends in the data are predominantly mechanical in nature, and strongly linked to the presence of stress triaxiality at the centre of the notched samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A slightly Ni-rich NiTi–20Hf (at.%) alloy was aged for 3
h at 550
°C to form a homogeneous distribution of 10–20
nm precipitates. To determine the effect of such structures on the ...martensite–austenite transformation, preliminary load-biased shape-memory and superelastic properties were measured. The alloy exhibited reasonably high transformation temperatures, near-perfect dimensional stability and a work output as high as 18.7
J
cm
−3 during load-biased thermal cycling. Isothermal stress cycling of the austenite between 180 and 220
°C resulted in near-perfect superelastic behavior up to 3% applied strain.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Comparative study on
analytical method
,
simplified method
and
weight function approach
for determination the double-
K
fracture parameters using three-point bend and compact tension tests specimen ...geometries is presented in the paper. The input data required for numerical calculations are obtained using Fictitious Crack Model. The study reports that the double-K fracture parameters computed depends on factors such as initial-notch length/depth ratios, specimen geometry and size-effect. In addition, it is demonstrated that the use of weight function will further improve the computational efficiency without loss of accuracy.
We demonstrate that bulk nanoscale materials with high strength and high ductility can be synthesized by using long-range ordering in certain alloy systems. In the case of a Ni-18.6 atomic % Mo-15.1 ...atomic % Cr, a bulk nanoscale superlattice of Ni
2(Cr,Mo) isomorphous with Pt
2Mo has been synthesized by thermal aging at 700
°C. The superlattice is shown to have high strength and high ductility as well as high thermal stability. Although the yield strength is nearly doubled in the ordered state exceeding 800
MPa, the material is found to maintain about 70% of its initial tensile ductility corresponding to 42% engineering strain. This behavior has been related to the crystallography of the ordering transformation. Although most of the slip systems of the parent face-centered cubic lattice are suppressed by ordering, most of the twinning systems remain energetically favorable. Therefore, deformation in the ordered state is found to predominantly occur by twinning rather than by slip giving rise to the observed combination of high strength and high ductility.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Evaluation of interfacial toughness of sub-micron-thickness layers deposited on a ductile substrate is a challenging task which has motivated different experimental approaches. Fragmentation testing ...was used in the present study as a means of interface characterization of a silicon–nitride-coated polyimide substrate. During the test, after an initial rapid segmentation–cracking phase, the coating fragments developed edge delaminations which propagated in a stable manner with further increase in the applied strain. The debonding process was modelled by the finite element method incorporating a cohesive zone at the front of the interfacial crack. The edge cracks were found to be dominated by mode II loading. By fitting the predicted delamination evolution to the experimental data for coating fragments of differing geometry, the mode II critical energy release rate was estimated at 30
J
m
−2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
: New methods are emerging in the material characterisation field with the aim of exploiting innovative full‐field strain measurement techniques. Besides experimental issues, also numerical ...procedures for inverse problems should adapt to a new philosophy: the large amount of data referred to local strains should be used in an appropriate way to obtain as much benefits as possible. In this context, an experimental and numerical procedure for the characterisation of hyperelastic materials is proposed. Planar tension tests have been performed on flat rubber specimens of different geometries. Strain maps obtained by means of a 2D Digital Image Correlation system are used to implement the virtual fields method, to estimate material dependent parameters of two of the most known hyperelastic constitutive laws: Ogden and 2nd order Mooney‐Rivlin models. Numerical results and comparisons with experimental data are shown, analysing also aspects concerning implementation of the numerical procedures and computational efficiency of the algorithms.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
An overview is given of methods to determine the strength and fracture energy of concrete subjected to uniaxial tension. The test method is often erroneously––and persistently––referred to as the ...`direct tension test'. After a brief review of historical, mostly indirect methods, the paper focuses on more recent servo-controlled testing techniques. Assessment of effects like secondary bending, and rotation and/or translations of the loading platens, as well as size/scale effects and environmental effects on fracture seem important for a proper definition of tensile strength and fracture energy. Implications for modeling are debated. The methods can be transferred directly to studies of other quasi-brittle geo-materials like natural rocks, clay and ice, fired clay bricks, plaster and the like.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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