Napier, New Zealand
Napier, New Zealand

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Cottle D.J.,University of New England of Australia | Baxter B.P.,SGS New Zealand Ltd.
Textile Progress | Year: 2015

This review explores research and development in wool metrology to date. In doing so, it highlights the research work undertaken by three organisations, in particular, to the development of wool and textile metrology research covering all of the important physical properties of wool. Three key wool research centres at the beginning of the twenty-first century were CSIRO's Division of Textile and Fibre Technology at Belmont near Geelong, Victoria, the School of Fibre Science and Technology, University of NSW at Kensington, NSW in Australia, and the Wool Research Organisation of New Zealand Inc. at Lincoln near Christchurch, New Zealand. Due to funding pressures between 1997 and 2007, these centres either ceased to operate or were absorbed into larger, non-wool-focused organisations. The substantial contribution to the world's wool metrology literature made by their staff and graduates, over the period when the three organisations had around 300-500 staff involved in wool-related research activities, is recognised. The review analyses the research undertaken on wool properties to identify gaps that might be exploited through the application of new or novel use of technologies by the next generation of wool metrologists. The analysis indicates that although the main fibre/fleece characteristics which currently affect the pricing and trading of Merino wool are able to be readily and accurately measured, there remains considerable work to be done in linking wool measurements to the prediction of performance both in processing and in the final product. © 2015 The Textile Institute.


The long-term (> 10 years) oxidation behaviour of stainless steels (SS) at high temperatures was previously unknown. The behaviour was studied through a case study of failure analysis. A fluidisation nozzle made of 304 austenitic SS. After over 100,000 h of service at temperatures of 790–820 °C in a biomass boiler, the nozzle fractured. Failure analysis pinpoints that the nozzle wall temperature fluctuation caused the oxide scale cracking, which intensified the oxidation. The brittle fracture was due to fully oxidization. The long-term oxidation behaviours are distinct from the short-term oxidation behaviours. XRD analysis indicates that the scale was mainly Fe+ 2Cr2O4 and (Fe0.6 Cr0.4)2O3. ESEM/EDS analysis indicates internal oxidation and sulfidation along the grain boundaries. The different diffusion rates of the Fe, Cr and Ni atoms formed a Ni-rich (48%) layer underneath the scale, and a Cr-rich (35%) core in the remained SS. A schematic is proposed to describe the diffusion mechanism of the internal oxidization and sulfidation behaviour. © 2016 Elsevier Ltd


Liu W.,SGS New Zealand Ltd.
Engineering Failure Analysis | Year: 2013

The premature failure of the economiser in a biomass fuel boiler was studied. On the internal oxide surface, three morphologies of iron oxides - aggregate oxide (Fe3O4), flower oxide (Fe3O4) and spherical oxide (FeO) have been discovered using ESEM/EDS. The oxidation and pitting occurred on the internal surface was trivial in comparison to the erosion-corrosion rate at outer surface of the economiser. The dominant abrasive SiO2 particles were partially cemented by the calcium compound particles in the biomass fly ash. The individual sharp abrasive SiO2 particles had been revealed with filtergram by dissolved the calcium compound particles in acid solution. The average size of SiO2 particles was approximately 100μm. Some SiO2 particles were up to 500μm. Study on the external scale found different oxide morphologies and the compositions, the flower-like oxide (Fe3O4) at the top and " mud-crack" FeO oxide at the flat sides. The wastage profile of 'V-shaped thickness thinning' can be explained by the mechanism proposed in this paper; the oxidation acting simultaneously with two-body abrasive wear by fly ash particle impingement. © 2013 Elsevier Ltd.


A dynamic creep mechanism has been proposed and verified through a case study. A secondary superheater tube burst occurred in a 43. MW coal-fired boiler. Microstructural examination indicates that the overheating temperatures reached 900. °C (above Ac3). The overheating duration was estimated to be 3. h by calculating with LMP formula. The 710. μm steam-side scale and 960. μm fireside scale built-up in the short time of overheating. The burst scenario was a short-term severe overheating on the basis of the long-term creep. The multilayer oxide scales on both sides have been studied with ESEM/EDS, indicating FeO. At 900. °C, full decarburization had gone throughout the tube. As the strength reduced due to the decarburization, the creep mechanism transformed from long-term intergranular creep to short-term transgranular rupture. The two types of dimples on the fractograph and two types of cracks in the microstructures confirmed the mechanism transformation. The overheating, the scale buildup and the decarburization constituted the full picture of the dynamic creep rupture. © 2015 Elsevier Ltd.


A repeat premature geartooth breakage occurred in a load gearbox of a 40. MW steam turbine. Fractographic examination indicated that the fatigue crack originated from the root fillet of the non-active flank and propagated to the active flank. The oil deposit on the fracture surface has been applied as an auxiliary fractographic method to distinguish the fatigue crack path. The root cause of the fatigue failure was the improper heat treatment, including the very coarse microstructures due to the direct quenching from the carburizing, plus the shallow case and the insufficient surface hardness by the post-quenching grounding. The solution was successful. Some butterfly characteristics in this case study contradicted to the previous theories. The butterflies initiated from neither non-metallic inclusion nor carbide. The butterfly cracks did not propagate into the martensitic matrix. A butterfly observed in the subsurface of the gear-root indicated that the butterfly formation was irrelevant to the Hertzian stress. © 2014 Elsevier Ltd.


Liu W.,SGS New Zealand Ltd.
Engineering Failure Analysis | Year: 2014

Bearing premature failures are prevalent in VFD (Variable Frequency Drives) motors. The three common symptoms of the modern bearing current appeared on the bearings of a group of pump motors. The bearing failure mechanisms have been studied from the tribological point of view. The natures of the three common symptoms have been uncovered. A hypothesis of the skin effect has been proposed to explain the three common symptoms. The discovery of the serial microcraters reveals the discharge with Fourier series features. The nature of the fluting patterns excluded the theories of both EDM (Electrical Discharge Machining) and discharge corrugation. VA (Vibration Analysis) detected the harmonics of the BPOR (Ball Pass Outer Ring) frequency which associated with the fluting on the outer raceway. This discovery may be applied to detect fluting in condition monitoring. © 2014 Elsevier Ltd.


Liu W.,SGS New Zealand Ltd
Engineering Failure Analysis | Year: 2014

A duplex stainless steel (2205) pipe in a new yacht suffered an extremely high corrosion rate (40mm/y) failure. ESEM/EDS and XPS analyses indicate that the failure mode was MIC. The bacteria attached preferentially on the austenite grains forming the colony "centre". The preferential corrosion on the austenite grains formed the "sponge" feature. The remaining ferrite grains became the "skeleton" structure. The sulphate detected by XPS suggests SOB involvement in the MIC. A hypothesis of SRB and SOB proliferating symbiotically proposed in this paper can explain the extremely high corrosion rate. SRB transferred sulphate from seawater to sulphide. SOB converted the sulphide to the extremely acid (H2SO4). SOB should be the main culprit of the failure through its high corrosion rate. The nitriding effect around the FZ had been confirmed by SES and EDS analyses. The high nitrogen contents attracted the bacteria to attach and proliferate. This finding may uncover the mystery of why weldments are susceptible to MIC. © 2014 Elsevier Ltd.


Hyperthermophiles are microorganisms that can thrive at high temperatures (80-122. °C). This article presents the study of hyperthermophilic influenced corrosion on an offshore pipeline (105. °C). Research with material science-based approaches found the multi-metal and sulphate reduction functions in the hyperthermophiles. ESEM/EDS (environmental scanning electron microscopy/energy-dispersive spectroscopy) analysis discovered different types of biofilms, microscopic bio-tubercles and bio-spherical particles. All of these findings confirm the MIC. There were two corrosion modes inside the pipe, uniform corrosion and localised severe corrosion. The localised severe pitting only occurred around the weld, suggesting the nitriding effect could attract the hyperthermophiles to proliferate. In the uniform corrosion, there were three layers in the cross section of the bio-oxide scale. In the middle layer, up to 38.94% of arsenic had been detected, indicating the strong arsenate-reduction capability. © 2014 Elsevier Ltd.


Liu W.,SGS New Zealand Ltd.
Engineering Failure Analysis | Year: 2014

The premature failure mode of the nozzle unit in the plastic injection moulding machines was discovered to be cavitation erosion, rather than corrosion. The microscopic features of the cavitation erosion on the soft aluminium alloy have its own distinct characteristics. Three types of erosion pits in different size order have been discovered: a large round pit with very smooth surface are in the size range of 1-2. mm, small round overlapping pits in the pattern of parallel line are approximately 100. μm, and micro erosion pits are about 5. μm. These different size order erosion pits might be associated with the different size order of bubbles imploding. The root cause of the bubble formation was the alteration in surface tension and the vapour pressures due to the dosing chemicals in the coolant. The solution to the cavitation erosion with substituting stainless steel to aluminium alloy has been successful. © 2013 Elsevier Ltd.


Liu W.,SGS New Zealand Ltd
Advanced Materials Research | Year: 2014

A repeat geartooth breakage occurred in a load gearbox of a 40MW steam turbine. Fractographic examination suggests that the breakage was a fatigue fracture. The oil deposit on the fracture surface has been applied as an auxiliary fractographic method. The root cause of the failure was due to improper heat treatment. The insufficient surface hardness and shallow case caused the case/core separation. The very coarse low carbon martensite in core caused cleavage fracture in final fast fracture. The fractographic morphology of the butterfly has been revealed. Hertzian stress and non-metallic inclusions are not the necessary condition of the butterfly formation. The microcracks within the butterflies did not actively play the role of the fatigue rupture. © (2014) Trans Tech Publications, Switzerland.

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