Biography:

In the past Z.W. Huang has collaborated on articles with S.P. Chiew and J.Y. Guo. One of their most recent publications is - Fatigue crack propagation of tubular T-joints under combined loads. Which was published in journal .

More information about Z.W. Huang research including statistics on their citations can be found on their Copernicus Academic profile page.

Z.W. Huang's Articles: (10)

- Fatigue crack propagation of tubular T-joints under combined loads

Publisher SummaryExperimental fatigue studies are conducted on three identical steel tubular T-joints subjected to in plane bending (IPB), combination of IPB and out-of-plane bending (OPB) and combination of axial loading (AX), IPB and OPB respectively. The fatigue performances of the joints subjected to these basic and combined load cases are investigated, and the Alternating Current Potential Drop (ACFD) technique is used to monitor their joint crack growth and crack shape developments. The test results confirm that the tubular joint fatigue design S-N curve which is based on single axis test data is still valid for T-joints subjected to combined load cases. The specimens are also simulated numerically using a modeling procedure which can include a semi-elliptical surface crack located at any position and any length along its brace-chord intersection within the joint finite element model. The numerical results are validated against those obtained from experiments using the Paris' law equations. Good agreement between these results confirms that the proposed modeling procedure is reliable and appropriate for fracture mechanics analysis.

Comparisons among contemporary glacial isostatic adjustment models

AbstractWe compare 14 glacial isostatic adjustment (GIA) models from different authors to assess how well the GIA effect could be removed from space geodetic data, such as those of the Gravity Recovery and Climate Experiment (GRACE) satellites, to study climate related and other mass changes within the Earth system. Direct comparisons of model outputs confirm unacceptably large discrepancies among models. Here we use two approximate relations within any GIA model without rotational feedback discovered by Wahr et al. (1995), i.e., an uplift–geoid relation and an uplift–gravity relation, to test the models for internal consistency. We find that all models without rotational feedback fit the relations reasonably well with only one exception, which still appears to fit the relations, but not as well. However, some models with rotational feedback fit the relations reasonably well, while some do not. As a result, the discrepancies arising from differences in formulations or computational methods, especially rotational feedback formulations, appear to dominate over those arising from differences in ice history and Earth rheology. We conclude that the accuracy and consistency of GIA models, especially agreement of results obtained using different formulations and computational methods, need to be substantially improved to full exploit contemporary space geodetic data, such as GRACE data, to enhance the constraints on ice-sheet mass balance and the mass component of global sea-level change.

Research paperBrittleness evaluation of the inter-salt shale oil reservoir in Jianghan Basin in China

Highlights•The elastic parameters of the inter-salt oil shale are quite different with that of the gas shale.•The mechanical brittleness index profile along the wellbore of the shale oil reservoir can be obtained.•The inter-salt oil shale is semi-brittle at the high level of confining pressure based on the full stress-strain curve theory.

Research paperAverage spectrum of cochlear activity: a possible synchronized firing, its olivo-cochlear feedback and alterations under anesthesia

AbstractAverage spectrum of electrophysiological cochlear activity (ASECA) recorded from the cochlea or the eighth nerve is related to firing of auditory neurons and has been used recently in search of an objective measure of tinnitus both in animal models and in humans. Little is known about neuro-sensory processes underlying the spectral features of ASECA. The present study used awake and/or anesthetized animals and investigated effects of various sounds presented contralaterally and ipsilaterally. Contralateral stimulation with noise bands at frequencies above about 8 kHz and below acoustic interaural cross-talk decreased the amplitude of the 1 kHz peak of ASECA. When presented ipsilaterally noises produced either an increase or a decrease of this spectral peak when the acoustic bandwidth was respectively above or below 1.5 kHz. Pure tones when presented contralaterally had no detectable effect. When presented ipsilaterally pure tones with frequencies higher than about 4 kHz decreased the 1 kHz peak of ASECA. The detailed time course of sound-induced variations of the 1 kHz peak was measured by time averaging. The resulting response patterns resemble PST histograms of the auditory nerve. Sedation and anesthesia deepened the 500 Hz trough of ASECA and shifted it towards 400 Hz. Sedation induced a diminution and anesthesia an almost complete suppression of the decrease of the 1 kHz peak induced by contralateral noise. Overall these data indicate that ASECA would reflect synchronized firings and they provide evidence for an influence of olivo-cochlear feedback sensitive to the state of awakeness.

Experimental study on horizontal wellbore cleanout by rotating jets

AbstractHorizontal wellbore cleanout by rotating jets has been developed rapidly in the past decades. To improve the sand cleanout efficiency, the strength of helical flow as one of the most important factors is necessary to be investigated and optimized. The flow rate, nozzle size, nozzle orientation and annular size have the major influence on the arising, performing and attenuating of annular helical flow. This paper presents the experimental results of a horizontal wellbore cleanout with varying nozzle assemblies in orifice size and orientation, tubing size, solid size, and flow rate. The tests of stationary circulation and wiper trip were carried out respectively. In the stationary circulation stage, there exists a critical length between sand bed and cleaning tool which results the two kinds of mechanisms to transport the sand. When the distance is shorter than the critical length, the primary mechanism of sand suspend is annular helical flow. As the distance is longer than it, the mechanism turns into straight annular flow which results in lower cleanout efficiency. In this study, the critical length increases rapidly with the increase of flow rate, tubing size and sand size. The sand bed moving velocity changing with the distance was also investigated and it is beneficial to optimize the wiper trip speed of cleaning tool. For the wiper trip stage, there exists the maximum wiper speed which can fulfill the requirement of completely sand cleanout when the tool is pulled out of the hole(POOTH), and it increases with the increase of flow rate and tubing size, and the decrease of sand size. The nozzle assembly is one of the most important factors to affect the helical flow profile and sand cleanout efficiency. The optimum lateral nozzle size and nozzle orientation were also obtained to get a best performance in annular helical flow and wiper trip speed. This study can contribute to the optimum design of nozzle assemblies, operation procedures and hydraulic parameters so that the highest efficiency of horizontal wellbore cleanout can be achieved.

Electronic structural, elastic properties and thermodynamics of Mg17Al12, Mg2Si and Al2Y phases from first-principles calculations

AbstractElectronic structures, elastic properties and thermal stabilities of Mg17Al12, Mg2Si and Al2Y have been determined from first-principle calculations. The calculated heats of formation and cohesive energies show that Al2Y has the strongest alloying ability and structural stability. The brittle behavior and structural stability mechanism is also explained through the electronic structures of these intermetallic compounds. The elastic constants are calculated, the bulk moduli, shear moduli, Young's moduli and Poisson ratio value are derived, the brittleness and plasticity of these phases are discussed. Gibbs free energy, Debye temperature and heat capacity are calculated and discussed.

On the role of thermal exposure on the stress controlled fatigue behaviour of a high strength titanium–aluminum alloy

AbstractFatigue specimens with four types of surface were assessed under three exposure conditions (no exposure, block exposure, individual exposure–oxidation at 700 °C for 10,000 h) to quantify the effects of surface roughness, stress concentration, oxidation and inner microstructural embrittlement on fatigue strength of a near lamellar γ-TiAl alloy Ti–44Al–4Nb–4Zr–0.2Si–1B. With the yield strength of σ0.1=621 MPa, S–N fatigue is found to be always conducted under a loading condition of σmax<σ0.1. Local plastic deformation is difficult to occur on the maximum-stressed surface. The surface quality with or without defects and residual stresses therefore becomes critical for fatigue performance. Introducing compressive-stressed layer by shot peening and removing tensile-stressed layer and defects by grinding-electropolishing can improve the fatigue strength significantly, and the latter is more capable than the former for the high strength alloy. It is found that the fatigue performances of all types of surface are deteriorated to some degree when subjected to block exposure, owing to exposure-induced embrittlement. On the other hand, exposure-induced fatigue strengthening occurs after individual exposure–oxidation. The relaxation of residual tensile stress and dissipation of bulk stress in warm-air environment are found to outweigh the negative effects of oxidation layer at surface and exposure-induced embrittlement inside specimen.

Electron microscopy characterization of the weld line zones of an inertia friction welded superalloy

AbstractMicrostructure in the weld line (WL) zone produced by inertial friction welding has been studied for a series of RR1000–RR1000 welds using transmission electron and scanning electron microscopy. A fully recrystallised fine grain structure was found to form throughout the WL zone, characterized by straight and smooth grain boundaries, high energy status and modified grain boundary chemistry due to very fast cooling after welding. Very fine γ′ particles with unimodal size distribution were reprecipitated in the WL zone. The fine γ′ particles are spherical in shape, high in number density and characterized by an imbalanced chemistry, containing less Al, Ti, Ni, Ta γ′-forming elements but more Cr, Co, Mo γ-forming elements than all types of parent γ′ particles. As a result, a hard and strong WL zone was produced by the inertial friction welding.

Thermal stability of Ti–44Al–8Nb–1B alloy

AbstractA fully lamellar γ-TiAl alloy Ti–44Al–8Nb–1B was exposed to the temperature of 700 °C in air for up to 5000 h. The changes in microstructure were investigated using scanning and transmission electron microscopies. The fine-grained lamellar microstructure produced by ingot-casting and hot-isostatic pressing is found to be thermodynamically unstable. Metastable α2 lamellae readily decompose and three types of phase transformation occur during the exposure. The first is α2 → γ, occurring with the parallel decomposition of coarse α2 laths. The second is α2 → B2(ω), occurring along single α2 laths. The third is α2 + γ → B2(ω), occurring on decomposing α2 + γ lamellae packets. The B2(ω) formed is found to be not very different from their parent phase(s) in composition. A widespread precipitation of B2(ω) therefore proceeds, causing segregation both at colony boundaries and inside lamellar colonies. The volume fraction of B2(ω) is almost doubled: from 3% in the as-cast condition to 5.8% after 5000-h exposure.

Thermal stability of an intermediate strength fully lamellar Ti–45Al–2Mn–2Nb-0.8 vol.% TiB2 alloy

Highlights•Dominant change during exposure was that the α2 lamellae thinned gradually.•α2 lamellae thickness reduced to a half and vol.% by 1/4 after 10,000 h exposure.•Tensile strengths remain unchanged and fatigue limit increases by 30% after 10,000 h.•Stability is attributed to near-equilibrium processing and low-alloyed composition.

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