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Publications
Publications (62)
Automated stereological methods are presented for approximating the 3D size distribution of unimodal or bimodal precipitate dispersions considering 2D and 1D measurements taken from polydisperse spherical non-penetrating particle dispersions. A method to quantify the uncertainty of the approximation as a function of the number of sampled particles...
A detailed microstructural characterisation of the emerging weld-line grain structure, for bead-upon-plate welds in Ti-6Al-4V (Ti64) of differing plate thickness, was performed. The microstructure studied was formed during both steady state and non-steady state sections within the weld path, with the non-steady state portion being taken from the en...
Metal powder bed fusion (MPBF) is not a standalone process, and other manufacturing technologies, such as heat treatment and surface finishing operations, are often required to achieve a high-quality component. To optimise each individual process for a given component, its progression through the full process chain must be considered and understood...
A theoretical treatment on the oxide-controlled dwell fatigue crack growth of a γ’ strengthened nickel-based superalloys is presented. In particular, this study investigates the influence of an externally applied load and variations in the γ’ dispersion on the grain boundary oxide growth kinetics. A dislocation-based viscoplastic constitutive descr...
The fluid dynamics of multi-component alloy systems subjected to high energy density sources of heat largely determines the local composition, microstructure, and material properties. In this work a multi-component thermal fluid dynamics framework is presented for the prediction of alloy system development due to melting, vaporisation, condensation...
A microstructural characterisation and computational modelling framework for simulating the coupled thermal-mechanical cycles with two different initial parent microstructures, and their impact upon the emerging microstructure features including β grain size and phase volume fractions during electron beam welding (EBW) of Ti-6Al-4 V (Ti64) alloy is...
Three-dimensional analysis of dendrites via automated serial sectioning using a Robo-Met.3D - Y. Lu, M. Wang, Z. Wu, I. P. Jones, M. Wickins, N. R. Green, H. C. Basoalto
Wind turbine gearboxes (WTG) have been suffering from premature failures and rarely live up to their designed lifetime. This study focuses on a better understanding of WTG failures. A finite element model of a gear pair was coupled with a constitutive model to quantify and predict damage, while also testing for different service conditions. A damag...
The precipitation kinetics of gamma prime in the nickel based superalloy RR1000 has been characterised after solid-solution heat treatments and isothermal aging conditions relevant to service conditions. Multi-modal precipitate dispersions are formed within the alloy. Numerical methods are presented for determining the three dimensional size of the...
The prediction of solidification microstructures associated with additive manufacture of metallic components is fundamental in the identification scanning strategies, process parameters and subsequent heat treatments for optimised component properties. Interactions between the powder particles and the laser heat source result in complex thermal fie...
Inertia friction welding has been used across the aerospace, automotive, and power-generation industries for the fabrication of complex axisymmetric components for over forty years. The process involves one axisymmetric piece being held stationary and another piece being brought into contact set to rotate about its axis of symmetry by a flywheel wi...
This paper presents a computational framework to study the differences in process-induced microvoid and precipitate distributions during selective laser melting (SLM) of two nickel-based superalloys representative of low (IN718) and high (CM247LC) volume fraction precipitate-strengthened alloys. Simulations indicate that CM247LC has a higher propen...
Wind turbine gearboxes are required to operate under adverse operational conditions over a long service lifetime. Unfortunately, gearbox designers are yet to achieve the reliability anticipated by wind turbine manufacturers and operators. The poor understanding of variable loading conditions has resulted in the majority of wind turbine gearboxes be...
![Fig. 1 whilst Azadian et al. [2] have measured area fractions as high](profile/Chinnapat-Panwisawas/publication/326219059/figure/fig10/AS:650015697539072@1531987227494/whilst-Azadian-et-al-2-have-measured-area-fractions-as-high_Q320.jpg)
A multi-phase, multi-component mean-field model has been developed for simulating the intermetallic precipitation kinetics in Inconel 718. The aim of this work is to develop predictive capability to aid in process optimisation and explore precipitation kinetics during additive manufacturing (AM). The model has been calibrated to available experimen...
A fluid dynamics approach to modelling of fusion welding in titanium alloys is proposed. The model considers the temporal and spatial evolution of liquid metal/gas interface to capture the transient physical effects during the heat source–material interaction of a fusion welding process. Melting and vaporisation have been considered through simulat...
Reliability issues associated with wind turbine gearboxes are yet to be resolved in full. Gearbox faults result in lower wind turbine availability reducing the maximum capacity factor that can be achieved by a wind farm. More serious are the effects of such faults in the optimised operation of offshore wind turbines. From the research and demonstra...
Over the last decade, the global wind power capacity was steadily growing at an annual rate around 20%, becoming the most important renewable energy source on a global scale, with the global total reaching 430 GW. Several thousands of industrial multi-MW wind turbines have been installed both onshore and offshore. However, the expansion of wind pow...
Although wind turbine gearboxes are designed to remain in-service for 20-25 years, this is not normally the case due to defects initiating and developing prematurely. A large number of gearboxes fail after 7 to 8-years in service. In offshore wind farms gearbox failures have been reported after only 1-2 years in service leading to noteworthy produc...
High energy-density beam welding, such as electron beam or laser welding, has found a number of industrial applications for clean, high-integrity welds. The deeply penetrating nature of the joints is enabled by the formation of metal vapour which creates a narrow fusion zone known as a “keyhole”. However the formation of the keyhole and the associa...
Inertia friction welding (IFW), a type of rotary friction welding process, is widely used across aerospace, automotive and power-generation industries. The process considers a specialist rotary friction welding machine, which asks for the critical process parameters of inertial mass, initial rotational speed and applied pressure, to complete the re...
A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-based superalloy IN718 is presented. Representative powder-bed particle distribution is simulated using the measured size distribution from experiment. Thermal fluid dynamics calculations are then used to predict melting behaviour, sub-surface morphology...
Finite element (FE) modelling of fusion welding methods has become an established numerical tool used by high-value manufacturing industries and academic communities, largely due to its capabilities to predict residual stress and distortion. However, a major drawback of this type of approach is the requirement to perform a test weld at the relevant...
A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-based superalloy IN718 is presented. Representative powder-bed particle distribution is simulated using the measured size distribution from experiment. Thermal fluid dynamics calculations are then used to predict melting behaviour, sub-surface morphology...
A mean field description of particle coalescence and Ostwald ripening is presented. The inclusion of particle coalescence events is shown to influence the evolution of the size distribution function and the time taken to reach the steady state particle coarsening regime. Nearest neighbour functions are used to represent the spatial arrangement of p...
A multi-component mean field model has been applied to predict the particle evolution of the γ′ particles in the nickel based superalloy IN738LC, capturing the transition from an initial multimodal particle distribution towards a unimodal distribution. Experiments have been performed to measure the coarsening behaviour during isothermal heat treatm...
Laser welding has become an important joining methodology within a number of industries for the structural joining of metallic parts. It offers a high power density welding capability which is desirable for deep weld sections, but is equally suited to performing thinner welded joints with sensible amendments to key process variables. However, as wi...
The mechanical behaviour of welded components is dependent on the microstructures produced during the joining process. This is particularly true for alpha-beta titanium alloy welds where the structure and properties are dominated by the phase transformation that occurs during the thermal cycle. In this work the mechanical properties of the weld met...
The presence of porosity inherited from a fusion welding operation degrades the mechanical properties of components during performance such as fatigue life. In this study, a physics-based model including heat transfer, fluid flow, interfacial processes and microstructure prediction via cellular automata has been developed and used to simulate poros...
Weld simulation methods have often employed mathematical functions to describe the size and shape of the molten pool of material transiently present in a weld. However, while these functions can sometimes accurately capture the fusion boundary for certain welding parameters in certain materials, they do not necessarily offer a robust methodology fo...
In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by
selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied
and correlated with the melt flow behaviour through both experimental and modelling approaches.
The as-fabricated samples were investigated us...
In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied and correlated with the melt flow behaviour through both experimental and modelling approaches. The as-fabricated samples were investigated us...
Thermal fluid dynamics and experiments have been used to study the evolution of pores during selective laser melting of Ti-6Al-4V. Scanning electron micrographs show that the morphology of pores changed from near-spherical to elongated shape as the laser scan speed increased. Computational fluid dynamics suggests that this is caused by the change o...
The industrial application of titanium alloys requires a critical understanding of the influence of microstructure on mechanical properties. The aim of this work is to develop a model of plasticity in titanium alloys that accounts for the microstructure and its evolution during deformation. The approach is based on a state variable framework. Lengt...
The conventional consensus has it that the magnitude of the strain rate sensitivity observed in superplastic materials is linked with grain boundary sliding. The grain boundary sliding mechanism is thought to theoretically produce a strain rate sensitivity exponent of 0.5, which is in good agreement with experimental data. The present paper argues...
A physical model for the creep deformation of single crystal superalloys is presented that is sensitive to chemical composition and microstructure. The rate-controlling step is assumed to be climb of dislocations at the matrix/particle interfaces and their rate of escape from trapped configurations; a strong dependence on alloy composition then ari...
The creep properties of different γ′-Ni3Al distributions in the Ni115 nickel superalloy produced by heat treatment have been examined. At the stresses and temperatures employed it is shown that particle bypass cannot occur by cutting or bowing and so presumably occurs by a climb-glide motion. The creep strength of Ni115 is very poor at 800 °C and 3...
Service lives for critical rotating parts in aero engine gas turbines are declared using deterministic lifing calculations based on fixed point values of key mechanical properties and factors to allow for the scatter. However, novel probabilistic lifing algorithms have been developed, which are able to take into account the degree of scatter in the...
The coarsening of γ′-Ni3Al precipitates in the nickel superalloy Ni115 has been examined and compared to the results of a numerical model based on LSW coarsening theory. Ni115 has a γ′ fraction of around 60%, and at the coarsening temperatures of interest the γ′ distribution is bimodal, with two populations ∼5nm and ∼90nm in radius. It is found tha...
The present paper is concerned with the development of multiscale modelling approaches for predicting the microstructural evolution and high temperature deformation characteristics of superalloys with special attention to creep and hot forming behaviour. A microstructure informed deformation model is presented that links rearrangements at the micro...
The need to drive down the operating cost of aero-engines has led to increased interest in failure prediction and life extension of components in gas turbines. The aim of this paper is to present a generic microstructure-based remnant life assessment method for nickel-based superalloys, built upon an understanding of the dominant damage micromechan...
Rolls-Royce has developed a hyperbolic tangent representation of creep, referred to as CT07 [1], which explicitly relates the accumulated creep strain to the current time, stress and temperature. Although, such an approach has been successfully applied to a number of nickel-based superalloys, it will be shown that it does not adequately capture the...
A novel continuum damage mechanics model for creep deformation prediction explicitly relating the model parameters to quantitative microstructural measures has been applied for aluminium alloy 2650-T8. A new database of constant-load tensile creep tests has been developed and was used together with data from other sources. The model related the cre...
Past approaches to modelling the creep behaviour of engineering alloys have been either totally empirical or, while having functional forms consistent with current understanding of deformation and fracture mechanisms, have been calibrated by comparison with an available creep database. They have not specifically included quantitative measures of th...
Life prediction procedures for single crystal superalloys are largely based on the interpretation of uniaxial creep and low cycle fatigue data although turbine blades experience significant multiaxial stresses in service. Several models that have been proposed to represent the anisotropic creep of single crystal superalloys have the potential of be...
The high temperature microstructural stability and good thermal-mechanical properties of single crystal superalloys has played a crucial role in the development of these materials for gas turbine blade application. A form of Continuum Damage Mechanics has been successfully developed over a decade or so, to model the anisotropic creep deformation of...
Most current life prediction approaches have origins in an appreciation of mechanisms of deformation and fracture; however, their implementation almost universally involves empirical fit to experimental data. The present work couples a quantitative model of creep in particle-strengthened alloys with the consequences of an evolving microstructure. S...
An understanding of the mechanisms controlling the anisotropic deformation of single crystal superalloys is a prerequisite for establishing reliable constitutive laws for engineering design. It is clear that the anisotropy in creep strength cannot be explained in terms of Schmid law concepts and the operation of a single slip system. A model, that...
The creep behaviour of the single crystal nickel-base superalloy CMSX-4 has been studied under multiaxial loading, using double Bridgman-notch specimens with and nominal axial orientations, at 850°C and net section stresses of 600 to 850 MPa. The creep lives measured were an order of magnitude greater than those obtained with the same load in uniax...
Projects
Projects (3)
The £4m CASiM2 project is a joint University of Birmingham / Rolls-Royce plc / Airbus / the MTC collaborative venture, sponsored by the European Regional Development Fund (ERDF), aiming to promote the use of computational modelling techniques within the West Midlands region and assist local Small-Medium Enterprise businesses (SME's) to better understand manufacturing methods by these computational modelling methods.
Fusion weld techniques have been widely used in industries such as aerospace, power generation, automotive and energy, to fabricate their structures with high-integrity joining methods. These fusion weld techniques are typically electron beam welding, laser welding, TIG welding, MIG welding, other arc welding methods or pulsed welding. However, all fusion welding applications will inevitably induce distortions and residual stresses in to the structure close to the weld line. Whilst traditional experimental techniques can be used to measure the quantities of these fields, a computational model based upon FE methods could offer a greater understanding.
The project aims to take the exisitng finite element methods for welding distortion prediction, and significantly develop them. These developments include the prediction of weld pool size and shape using computational fluid dynamics (CFD) methods within the open source software OpenFOAM, develop Cellular Automata (CA) calculations to link in to the Finite element models to predict grain structure during and after the welding operation, and link these to a plasticity code to develop models for the lifing of these critical parts.
The £4m Next Generation Modelling Project of Manufacturing Portfolio Programme is a joint University of Birmingham / Rolls-Royce plc / the Manufacturing Technology Centre (MTC) collaborative venture, financially funded by the Aerospace Technology Institute (ATI), Innovate UK and Department for Business Innovation & Skills.
Integrated computational materials science/engineering (ICME) initiative will be developed to understand the microstructure-property-processing-manufacture relationship of laser/electron beam fusion welding, (quantum) laser/electron beam fusion powder-bed additive manufacturing as well as lifing prediction in aerospace applications.
The Next Generation Modelling project started in April 2016 and will be finished in March 2020.
In addition, I have involved in the 'Design by science' collaborative programme between University of Manchester and University of Birmingham, funded by Engineering and Physical Science Research Council (EPSRC).
