Publications
73 results found
Fox AB, Huang YY, Rafik D, et al., 2008, Increasing the life of flare tips, Pages: 88-95
Flare tips are essential for safety. Maintenance is difficult and costly. Flare tips are subjected to high combustion temperatures, thermal cycling, oxidation and marine corrosion. Following a number of flare tip failures an in depth study by Imperial College was carried out into the failure of a flare tip from a UK platform, looking for service life improvement. Materials selection and design solutions were considered. The study considered alternative materials and concluded that materials selection was the smaller part of the answer; design changes can double service life. This study used failure investigation, high temperature experimental and thermo-mechanical modelling analysis. The modelling process simulated two common flaring conditions and correctly predicted the observed failure of initiation and crack propagation from holes used to bolt on flame stabilizing plates to the top of the flare. The calculated thermal stress and strains enabled the low cycle fatigue life and minimum creep life to be predicted. It was concluded that service life could be improved by replacing Incoloy alloy 800HT (UNS N08800) with Inconel alloy 625 (UNS N06625), an alloy with attractive mechanical properties and improved high temperature corrosion resistance. Repositioning or eliminating bolt holes can double service life. Copyright 2008, Society of Petroleum Engineers.
Li P, Maijer DM, Lindley TC, et al., 2007, Simulating the residual stress in an A356 automotive wheel and its impact on fatigue life, Symposium on Simulation of Aluminum Shape Casting Processing - From Alloy Design to Mechanical Properties, Publisher: MINERALS METALS MATERIALS SOC, Pages: 505-515, ISSN: 1073-5615
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- Citations: 23
Li P, Maijer DM, Lindley TC, et al., 2007, A through process model of the impact of in-service loading, residual stress, and microstructure on the final fatigue life of an A356 automotive wheel, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 460, Pages: 20-30, ISSN: 0921-5093
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- Citations: 37
Bantounas I, Lindley TC, Rugg D, et al., 2007, Effect of microtexture on fatigue cracking in Ti–6Al–4V, Acta Materialia, Vol: 55, Pages: 1-11
Fatigue cracking in forged bar, unidirectionally rolled (UD) and cross-rolled (XR) plate product forms of Ti–6Al–4V subjected to high cycle fatigue with a stress ratio R = 0.3 was studied by examination of crack tips using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The bar and the UD materials were composed of macrozones 50–70 lm in width whereas the bands identified in the XR product were only a few grains thick (20 lm). The fatigue fracture surfaces observed were related to the macrozones in the underlying microstructure. EBSD analysis of the crack tips showed that cracks arrested when confronted by grains badly oriented for prismatic f10 10gh11 20i slip in both the bar and the XR materials. TEM foils were obtained from both the forward crack tip plastic zone and from the plastic wake, which showed that Æc+aæ slip operated in grains badly oriented for prismatic slip.
Li P, Lee PD, Maijer DM, et al., 2006, Through process modeling of aluminum alloy castings relating casting defects to fatigue performance, Pages: 661-668
There continues to be increasing interest in using cast aluminum alloy components in automotive applications with cyclic in-service loads. Predicting fatigue performance is a key issue in the design of these components and must consider the entire manufacturing route which typically involves casting, heat treatment and machining. A through process modeling methodology was used to predict fatigue life of one such component, an A356 automotive wheel. The technique tracks the microstructure and defect formation during the casting process as well as the residual stresses that arise due to heat treatment and subsequent finish machining. The micro structural features and the final residual stress state are used as input parameters to calculate the final cyclic stress state and in-service fatigue life. The pore size distribution and secondary dendrite arm spacing formed during casting were predicted using model-based constitutive equations run within a validated macroscopic heat flow model of the process. These constitutive equations were developed by regression fitting to results from an in-house mesoscale solidification model. The residual stresses formed during the quench stage of heat treatment and released during finish machining were simulated in a two-stage thermal stress model. A final stress/displacement model was developed to calculate the variation of the multi-axial stress state and the expected fatigue life of the wheel during cyclic in-service loading. Each of the model results shows good agreement to measurements taken at various stages of the manufacturing process. In particular, excellent agreement was attained for in-service strain. The fatigue performance was compared with full-scale fatigue test results to validate the suitability of the through process modeling for application to aluminum alloy wheels.
Yi JZ, Lee PD, Lindley TC, et al., 2006, Statistical modeling of microstructure and defect population effects on the fatigue performance of cast A356-T6 automotive components, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 432, Pages: 59-68, ISSN: 0921-5093
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- Citations: 67
Li P, Lee PD, Lindley TC, et al., 2006, X-ray microtomographic characterisation of porosity and its influence on fatigue crack growth, ADVANCED ENGINEERING MATERIALS, Vol: 8, Pages: 476-479, ISSN: 1438-1656
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- Citations: 28
Yi JZ, Gao YX, Lee PD, et al., 2006, Microstructure-based fatigue life prediction for cast A356-T6 aluminum-silicon alloys, METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE, Vol: 37, Pages: 301-311, ISSN: 1073-5615
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- Citations: 69
Lee PD, Li P, Maijer DM, et al., 2006, A validated through process model to predict the fatigue life of a cast A356 automotive wheel, 10th International Conference on Aliminium Alloys (ICAA-10), Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 1777-1782, ISSN: 0255-5476
Li P, Maijer DM, Lindley TC, et al., 2006, A validated model of the cyclic stress state of an A356 automotive wheel and its impact on fatigue life, Symposium on Simulation of Aluminum Shape Casting Processing - From Alloy Design to Mechanical Properties, Publisher: MINERALS, METALS & MATERIALS SOC, Pages: 73-+
Lindley TC, Li P, Maijer DM, et al., 2006, Prediction of fatigue performance in cast aluminum alloy components, Symposium on Simulation of Aluminum Shape Casting Processing - From Alloy Design to Mechanical Properties, Publisher: MINERALS, METALS & MATERIALS SOC, Pages: 289-+
Lee PD, Lindley TC, 2005, The influence of strontium and TiB<inf>2</inf> additions on the formation of porosity in aluminium castings and their effect on final fatigue properties, Foundry Trade Journal, Vol: 179, Pages: 216-219, ISSN: 0015-9042
The influence of altering both the processing conditions and minor alloying additions upon the formation of microporosity in aluminium castings was investigated using in situ, real time, radiographic observations and a posteri three dimensional x-ray micro-tomographic (XMT) techniques. The individual and interaction effects of eutectic modifiers (Sr) and grain refiners (TiB2) upon the size, distribution and three morphology of the pores formed was characterised. For each condition the fatigue behaviour was determined from heat treated samples. Using scanning electron microscopy, fractographic examination was performed, revealing that the fatigue cracks initiated at pores in almost all cases. The final fatigue performance was correlated to changes in microporosity and hence to the Sr and TiB2 additions. The results illustrate that the interaction of strontium and TiB2 is complex, affecting both the morphology of both the primary and eutectic phases which in turn influences the porosity. Further, the real-time radiographic observations suggest that the structure of the oxides formed is also affected, influencing both the nucleation and growth of pores.
Hamilton RW, Lee PD, Dashwood RJ, et al., 2005, Optimisation of a cast one-step forging operation by virtual processing, MATERIALS & DESIGN, Vol: 26, Pages: 29-36, ISSN: 0261-3069
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- Citations: 4
Lee PD, Lindley TC, 2005, The influence of strontium and TIB2 additions on the formation of porosity in aluminum castings and their effect on final fatigue properties, Warrendale, Symposium on shape casting of metals held in honor of John Campbell held at the 2005 TMS annual meeting, San Francisco, CA, 13 - 17 February 2005, Publisher: Minerals, Metals & Materials Soc, Pages: 225-234
Lee PD, Lindley TC, 2005, The influence of strontium and TIB2 additions on the formation of porosity in aluminum castings and their effect on final fatigue properties, Warrendale, Symposium on shape casting of metals held in honor of John Campbell held at the 2005 TMS annual meeting, San Francisco, CA, 13 - 17 February 2005, Publisher: Minerals, Metals & Materials Soc, Pages: 225-234
Yi JZ, Maijer DM, Gao YX, et al., 2004, Fatigue life prediction for cast A356 components, Pages: 9-17
The design of cast components for fatigue applications has traditionally been based on an extensive material property database together with experience from in-service performance. However, such an approach requires a significant number of fatigue tests to develop the S-N curves for conditions representing the in-service loading of the cast component and the large associated variation in microstructure and defect population. Furthermore, this approach does not incorporate the flexibility required for optimization of product design. In the present study, a new design methodology called Through Process Modeling is proposed to link the model predictions of microstructure and defects developed during the casting process and the residual stress introduced during heat treatment, with the in-service loading to predict the resultant fatigue properties of cast A356 aluminum alloy components. This methodology has been used to adequately predict the fatigue performance of a cast A356 brake caliper.
Yi JZ, Gao YX, Lee PD, et al., 2004, Effect of Fe-content on fatigue crack initiation and propagation in a cast aluminum-silicon alloy (A356-T6), MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 386, Pages: 396-407, ISSN: 0921-5093
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- Citations: 141
Gao YX, Yi JZ, Lee PD, et al., 2004, A micro-cell model of the effect of microstructure and defects on fatigue resistance in cast aluminum alloys, ACTA MATERIALIA, Vol: 52, Pages: 5435-5449, ISSN: 1359-6454
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- Citations: 114
Maijer DM, Gao YX, Lee PD, et al., 2004, A through-process model of an A356 brake caliper for fatigue life prediction, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 35A, Pages: 3275-3288, ISSN: 1073-5623
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- Citations: 21
Gao YX, Yi JZ, Lee PD, et al., 2004, The effect of porosity on the fatigue life of cast aluminium-silicon alloys, International Conference on Fatigue and Durability Assessment of Materials, Components and Structures, Publisher: WILEY, Pages: 559-570, ISSN: 8756-758X
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- Citations: 129
Conner BP, Lindley TC, Nicholas T, et al., 2004, Application of a fracture mechanics based life prediction method for contact fatigue, INTERNATIONAL JOURNAL OF FATIGUE, Vol: 26, Pages: 511-520, ISSN: 0142-1123
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- Citations: 23
Maijer DM, Gao YX, Lee PD, et al., 2004, A through-process model of an A356 brake caliper for fatigue life prediction, Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, Vol: 35 A, Pages: 3275-3288, ISSN: 1073-5623
The demand for low-cost, high strength-to-weight ratio components continues to drive the development of aluminum alloy castings for new applications. The automotive brake caliper, which has traditionally been made from cast iron, is one such component where aluminum alloys are being considered. The fatigue performance of the brake caliper is an important consideration in evaluating new designs. The use of aluminum alloys in cast components under cyclic loading conditions necessitates a design approach that, in addition to in-service loading, incorporates the impact of microstructural features on fatigue life, In this investigation, a through-process modeling approach has been employed to link a series of mathematical models describing the processing steps of (1) casting, (2) heat treatment, (3) machining, and (4) in-service performance for a preliminary design of a brake caliper made of aluminum alloy A356. Step (1) includes microstructural predictions (secondary dendrite arm spacing and maximum pore size), which are tracked through to the final component. The final lifing of the component combines the effects of these microstructural features with the complex stress state arising from the combined service loading and residual stresses. It was found that all three factors have a strong influence upon the component's fatigue performance.
Yi JZ, Gao YX, Lee PD, et al., 2003, Scatter in fatigue life due to effects of porosity in cast A356-T6 aluminum-silicon alloys, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 34A, Pages: 1879-1890, ISSN: 1073-5623
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- Citations: 163
Yi JZ, Gao YX, Lee PD, et al., 2003, Scatter in fatigue life due to effects of porosity in cast A356-T6 aluminum-silicon alloys, Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, Vol: 34 A, Pages: 1879-1890, ISSN: 1073-5623
Porosity is well known to be a potent initiator of fatigue cracks in cast aluminum alloys. This article addresses the observed scatter in fatigue life of a cast A356-T6 aluminum-silicon alloy due to the presence of porosity. Specimens containing a controlled amount of porosity were prepared by employing a wedge-shaped casting mold and adjusting the degassing process during casting. High-cycle fatigue tests were conducted under fixed stress conditions on a series of specimens with controlled microstructures (especially, the secondary dendrite-arm spacing), and the degree of scatter in the results was assessed. Stochastically, such scatter was found to be adequately characterized by a three-parameter Weibull distribution function. Large pores at or close to the specimen surface were found to be responsible for crack initiation in all fatigue-test specimens, and the resultant fatigue life was related to the initiating pore size through a relationship based on the rate of small-fatigue-crack propagation. With respect to the probabilities for the pores of various sizes and locations to initiate a fatigue crack, a statistical model was developed to establish the relationship between the porosity population and the resultant scatter in fatigue life. The modeling predictions are in agreement with the experimental results. Moreover, Monte-Carlo simulation based on this model demonstrated that the average pore size, pore density, and standard deviation of the pore sizes, together with the specimen size and geometry, are all of consequence regarding scatter in fatigue life.
Lee PD, Lindley TC, Cheong CWJ, et al., 2003, The effect of metallurgical variables and porosity on the high cycle fatigue behaviour of aluminium alloy 319, Vancouver, Light metals 2003 Mtaux lgers, 24 - 27 August 2003, Vancouver, Canada, Publisher: MetSoc, Pages: 457-472
Yi JZ, Gao YX, Lee PD, et al., 2003, The effects of microstructure and defects on fatigue properties in cast A356 aluminium-silicon alloy, Engineering integrity society; fatigue 2003 - fatigue & durability assessment of materials, components & structures, Publisher: EIS, Pages: 183-192
Lindley TC, 2003, Fretting wear and fatigue in overhead electrical conductor cables, ASTM Special Technical Publication, Vol: 1425, Pages: 403-422, ISSN: 0066-0558
Lindley TC, 2002, Keynote: fretting fatigue: experiments, modelling and applications, International fatigue conference, Publisher: EMAS, Pages: 2119-2130
Uzun H, Lindley TC, McShane HB, et al., 2001, Fatigue crack growth behavior of 2124/SiC/10<i>p</i> functionally graded materials, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 32, Pages: 1831-1839, ISSN: 1073-5623
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- Citations: 17
Venkatesh TA, Conner BP, Lee CS, et al., 2001, An experimental investigation of fretting fatigue in Ti-6Al-4V: the role of contact conditions and microstructure, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 32, Pages: 1131-1146, ISSN: 1073-5623
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- Citations: 56
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