Xijia Wu

• PhD
• Adjunct Professor at Carleton University

This research tackles the fundamental issue of computational fatigue studies by developing an effective approach that combines the crystal plasticity finite element method (CPFEM) with the Tanaka-Mura-Wu (TMW) model for crack nucleation and the Tomkins model for fatigue crack propagation, to provide Class-A predictions of the total coupon-fatigue l...

This research tackles the fundamental issue of computational fatigue studies by developing an effective approach which combines the crystal plasticity finite element method (CPFEM) with the Tanaka-Mura-Wu (TMW) model for crack nucleation and the Tomkins model for fatigue crack propagation, to provide Class-A predictions of the total coupon-fatigue...

Stellite 6 hardfacing is deposited on Haynes 282 and Inconel 740H via plasma transferred arc (PTA) welding. The fabricated hardfacing specimens are subjected to different post-welding heat treatments, and then aged at 760, 815 and 871 °C for a time length ranging from 1000 to 30,000 h. The microstructures of the hardfacings before and after long-ti...

Creep test is conducted on Haynes 282 weldment in a temperature range from 704 to 788 °C at different stress levels. The creep rupture data obtained from the creep tests are presented in a traditional Larson–Miller parameter (LMP) plot, together with a wide range of test data reported in the literature on both Haynes 282 base metal and weldment. Th...

To meet the requirements for materials used in the Advanced Ultra-Supercritical (A-USC) steam condition at an inlet temperature up to 760 °C which enables to increase the efficiency of coal-fired power generation and reduce its CO2 emission, a newly developed Tribaloy alloy T-400C is deposited on a Ni-based alloy Haynes 282 via plasma transferred a...

To advance the technology of Certification by Analysis (CbA), as called for by the aerospace industry, the fatigue problems of SAE keyhole specimens are analyzed to demonstrate a subcase of CbA. First, phenomena identification and ranking table (PIRT) analysis is performed. Second, modeling of the key phenomena is conducted, and finally, verificati...

Metal creep has been a subject of extensive study for more than 110 years because it affects the useful life of engineering components operating at high temperatures. This is even more true with ever-increasing operating temperatures of propulsion/power-generation systems and the environmental regulations to reduce greenhouse emissions. This review...

Metallic materials are crucial in engineering applications to bear complex loads in extreme environments, with fatigue being one of the critical failure modes. While basic material fatigue properties are still being assessed through physical testing in accordance with industrial standards, fatigue performance modeling and simulation are increasingl...

Metallic materials are crucial in engineering applications to bear complex loads in extreme environments, with fatigue being one of the critical failure modes. While basic material fatigue properties are still being assessed through physical testing in accordance with industrial standards, fatigue performance modeling and simulation are increasingl...

Metal creep has been a subject of extensive study for more than 110 years, because it affects the useful life of engineering components operating at high temperatures. It is even more so with ever-increasing operating temperatures of propulsion/power-generation systems by the environmental regulations to reduce greenhouse emissions. This review sum...

The creep behavior of Inconel 740H weldment at the temperature of 760 °C is investigated experimentally and analytically using the deformation-mechanism-based true stress (DMTS) model. The Inconel 740H weldment specimens are prepared with the gas tungsten arc welding (GTAW) technique. Creep testing is performed on the Inconel 740H weldment specimen...

Stellite 6 hardfacing is deposited on Haynes 282 and Inconel 740H via plasma transferred arc (PTA) welding. The fabricated hardfacing specimens are subjected to different post-welding heat treatments, then aged at 760 °C, 815 °C and 871 °C for a time length ranging from 1000 to 30000 h. The microstructures of the hardfacings before and after long-t...

Tribaloy alloy T-400C hardfacing deposited on Inconel 740H alloy via plasma transferred arc (PTA) welding has potential applications for high-temperature wear resistance of steam turbine components in the advanced ultra-supercritical (A-USC) operating condition. In this study, the T-400C hardfacing specimens via PTA welding are subjected to long-ti...

For nuclear power generation as a carbon‐neutral energy source, in‐vessel retention (IVR) must be implemented to maintain the structural integrity of nuclear reactor pressure vessel (RPV) for more than 72 h under severe accidental conditions. This technology requires accurate prediction of creep deformation and life of RPV material being operated u...

In this research, microstructure-based modeling is conducted to predict the fatigue crack nucleation life of a nickel-based alloy, Haynes 282, at different strain amplitudes from high cycle fatigue (HCF) to low cycle fatigue (LCF). A three-dimensional (3D) polycrystalline aggregate is constructed as the material representative volume element (RVE)...

Based on erosion coupon tests, a sand erosion model for 17-4PH steel was developed. The developed erosion model was validated against the results of compressor erosion tests from a generic rig and from other researchers. A high-fidelity computational fluid dynamics (CFD) model of the test rig was built, a user-defined function was developed to impl...

OBJECTIVES This session focuses on innovative and improved fatigue analysis/design methodologies and problem-solving techniques in the ground vehicle industry. The subjects of interest include studies and discussion on (1) customer usage development, (2) structural stress generation, (3) fatigue of metallic material including new lightweight metals...

This paper presents an overview of the self-heating phenomena and the continuum thermodynamics framework related to the damping and fatigue of metals. The self-heating process under cyclic loading generally undergoes three phases: Phase I with gradually increasing temperature to a stabilized or steady-state in Phase II, followed by Phase III with a...

In this research, the recently developed Tanaka-Mura-Wu (TMW) model is applied to common engineering materials including Ni-base superalloys Haynes 282 and Inconel 617, aluminum alloys 7075-T6 and 2024-T3, alloy steels SAE 4340 and SAE 1020, and titanium alloy Ti-6Al-4V, as well as a high-entropy alloy (HEA) CoCrFeMnNi over the full fatigue range c...

Additive manufacturing (AM) has drawn tremendous interest in engineering applications because it offers almost unlimited possibilities of innovative structural design to save weight and optimize performance. However, fatigue properties are one of the limiting factors for structural applications of AM materials. The recently developed Tanaka–Mura–Wu...

April 5-7, 2022 TCF Center, Detroit and Online SAE International's WCX is the premier global automotive technical conference and exhibition focused on virtually every facet of modern automotive mobility, including platform, system, subsystem, and component research & development, engineering, manufacturing, assembly, test and verification, certific...

The creep rate and life behaviors of different batches of Alloy 800 as reported in the reference paper are re-analyzed with the Deformation Mechanism based True Stress (DMTS) creep model. The delineation of deformation mechanisms leads to the conclusion that the Ti + Al content mostly affects intragranular dislocation glide (IDG). While IDG is resp...

Strain controlled thermo-mechanical fatigue (TMF) tests were conducted on a high Silicon ductile cast iron (SiMo) as the baseline material and a similar SiMo cast iron with aluminum addition (SiMoAl). The much improved fatigue life with aluminum addition is analyzed using the integrated creep-fatigue theory (ICFT) in combination with the metallurgi...

Fatigue and creep are major damage mechanisms/modes leading to material fracture, which are responsible for the failure of more than 90% of engineering components. Both subjects have been studied for more than 100 years. Today, more and more advanced materials are being developed, such as additively manufactured materials, nanocrystalline materials...

A general fatigue life equation is derived by modifying the Tanaka-Mura-Wu dislocation pile-up model for variable strain-amplitude fatigue processes, where the fatigue crack nucleation life is expressed in terms of the root mean square of plastic strain range. Low-cycle fatigue tests were conducted on an austenitic stainless steel. At 400 ? and 600...

The high-temperature oxidation and solid particle erosion of thermal barrier coating (TBC) system which consists of a 8 wt.% yttria-partially stabilized zirconia (YSZ) top coat and CoNiCrAlY bond coat deposited on Inconel 718 substrate via air plasma spraying (APS) process are studied experimentally. Isothermal oxidation tests of the APS-TBCs are c...

A general fatigue life equation is derived by modifying the Tanaka-Mura-Wu dislocation pile-up model for variable strain-amplitude fatigue processes, where the fatigue crack nucleation life is expressed in terms of the root mean square of plastic strain range. Low-cycle fatigue tests were conducted on an austenitic stainless steel. at 400°C and 600...

A microstructural fatigue crack nucleation model is developed for cast irons with graphite inclusions of different shapes, based on Eshelby’s solution for ellipsoidal inclusions and the Tanaka-Mura-Wu model for fatigue crack nucleation. This model is used to analyze ductile cast iron with nodular graphite microstructure, gray cast iron with flake-l...

Elements tungsten and molybdenum are the key constituents of Stellite alloys as solutes to strengthen the solid solution matrix. Meanwhile, they also promote formation of W-rich and Mo-rich carbides when present in large quantities in high-carbon Stellite alloys. Extensive studies on tungsten Stellite alloys, in particular, Stellite® 6, have been r...

In this study, the deformation-mechanism-based true-stress (DMTS) creep model is modified to include oxidation influence on the long-term creep performance of modified 9Cr-1Mo steels. An area-deduction method is introduced to evaluate oxide scale formation on the creep coupons, which is incorporated into the DMTS model formulated based on intragran...

The effect of hot streaks from a gas turbine combustor on the thermodynamic load of internally air-cooled nozzle guide vanes (NGVs) and shrouds has been numerically investigated under flight conditions. The study follows two steps: one for the high-fidelity 60° combustor sector with simplified ten NGVs and three thermocouples attached; and the othe...

Stress and temperature effects on the creep behaviors and mechanisms of a typical nuclear reactor pressure vessel material, SA508 Gr.3 steel, are investigated, over the temperature range of 450–750 °C and stress range of 10–400 MPa. Because of the importance of creep life prediction for nuclear reactor failure prevention, three creep models are ass...

This book walks you through the fundamental deformation and damage mechanisms. It lends the reader the key to open the doors into the maze of deformation/fracture phenomena under various loading conditions. Furthermore it provides the solution method to material engineering design and analysis problems, for those working in the aerospace, automotiv...

This paper presents an integrated creep-fatigue (ICF) theory to describe the non-linear creep-fatigue interaction during thermomechanical loading. The ICF theory recognizes the damage evolution as a holistic process consisting of nucleation and propagation of surface or subsurface cracks in coalescence with internally distributed damage, leading to...

A crack number density (CND) theory model is developed for air-plasma-sprayed thermal barrier coating (TBC), which describes the evolution of crack number and size distribution as function of exposure time. The model is compared in good agreement with experimental measurements from quasi-isothermal-cyclic oxidation tests. Both the CND model and exp...

Oxidation is a life-limiting factor for material durability. In this study, constant-load creep tests are conducted on modified 9Cr-1Mo steel (F91) with an oxidation-resistant coating, MCrAlY, to evaluate the coating effect on the creep behavior. The creep strain vs. time curves are compared with that of the uncoated material under constantload con...

Room-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550oC and 600oC, respectively. Microstructural and fractographic examinations on specimens with prior creep strain > 3% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep...

Based on Tanaka‐Mura's dislocation‐dipole pile‐up configuration, a formulation of mixed mode fatigue crack nucleation is derived using the Stroh formalism for generally anisotropic materials. The fatigue life is explicitly expressed as inversely proportional to the stored plastic energy, depending on the material's anisotropic elastic matrix F⁻¹, s...

Traditional engine maintenance, repair and overhaul (MRO) are geared toward fixed schedules. However, with on-line condition monitoring, assessments and prognosis, it is required that MRO be adaptive to the life consumption with respect to the actual usage of the engine to realize the benefit of prognosis. Shifting to this new paradigm, there are s...

Room-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550°C and 600°C, respectively. Microstructural and fractographic examinations on specimens with prior creep strain > 3% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep...

An integrated approach of constitutive modeling and life prediction is presented through introduction of the integrated creep-fatigue theory (ICFT). The ICFT is formulated based on participating deformation and damage mechanisms, which not only describes the cyclic deformation behavior, but also the life and fracture mode. Automotive exhaust system...

Tanaka-Mura's fatigue crack nucleation model is revisited. A dimensional problem is found in their cyclic plastic strain formulation obtained by integration of the displacement function, and hence, it is rederived based on the true strain definition. Using the corrected strain formulation, a new fatigue crack nucle-ation life expression is obtained...

The influence of Laves phase in the microstructure on the creep strength of a modified 9Cr-1Mo tempered ferritic steel, F91, is investigated in this research. Through additional aging heat treatment up to 5000 h, a pronounced increase of Mo-rich Laves phase is found around Cr-rich carbide M23C6, which is pinned on the prior-austenite grain boundari...

A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10⁻⁴ to 2 × 10⁻² s⁻¹.The ICFT formulates the material’s constitutive equation based on the ph...

In a recent paper published in Acta Materialia [Ravi Chandran, Acta Materialia 121 (2016) 85–103], the author assumed that crack initiates instantaneously to a size proportional to the applied stress minus the fatigue endurance limit over the range between the fatigue limit and the ultimate strength of the material. However, this relationship has n...

Nozzle guide vanes (NGV) of gas turbine engines are the first components to withstand the impingement of hot combustion gas and therefore often suffer thermal fatigue failures in service. A lifting analysis is performed for the NGV of a gas turbine engine using the integrated creep-fatigue theory (ICFT). With the constitutive formulation of inelast...

Description Get 20 peer-reviewed papers that will help you not only understand but also prevent fatigue and fracture. Access this new and diverse information regarding test planning, data acquisition and analysis, arranged into the following four sections As materials are increasingly being stretched to their limits by extreme conditions of tempera...

A deformation-mechanism-based true-stress creep model is proposed for studying the creep behavior of modified 9Cr-1Mo steel in this research. Constant-load creep test is conducted on modified 9Cr-1Mo steel in forged form (F91). The creep data obtained in the present study and those reported from the National Institute for Materials Science (NIMS, J...

Nozzle guide vanes (NGV) of gas turbine engines are the first components to withstand the impingement of hot combustion gas, and therefore often suffer thermal fatigue failures in service. A lifing analysis is performed for the NGV of a gas turbine engine using the integrated creep-fatigue theory (ICFT). With the constitutive formulation of inelast...

Low cycle fatigue (LCF) of 1.4848 austenitic steel was investigated through strain-controlled fatigue testing at strain rates of 0.02/s, 0.002/s, and 0.0002/s in the temperature range from room temperature (RT) to 900oC. Its cyclic behaviours were characterized in relation to deformation mechanisms. At room temperature, the material behaviour was r...

Deformation and damage accumulation occur by fundamental dislocation and diffusion mechanisms. An integrated creep-fatigue theory (ICFT) has been developed, based on the physical strain decomposition rule that recognizes the role of each deformation mechanism and thus relate damage accumulation to its underlying physical mechanism(s). The ICFT form...

Prognosis and health management (PHM) of gas turbine hot section components requires detailed 3D creep stress analysis using the finite element method (FEM) incorporated with material constitutive models, in order to assess the remaining useful life with regards to the complex mission usages. For this purpose, a nonlinear stress analysis was perfor...

In this paper, both standard and constrained thermomechanical fatigue (TMF) tests were conducted on a high silicon ductile cast iron (DCI). The standard TMF tests were conducted with independent control of mechanical strain, out-of-phase (OP) and in-phase (IP) strain, and temperature in the range from 300 to 800°C. The constrained TMF tests were co...

Thermomechanical fatigue (TMF) behaviors of ductile cast iron (DCI) were investigated under out-of-phase (OP), in-phase (IP), and constrained strain-control conditions with temperature hold in various temperature ranges: 573 K to 1073 K, 723 K to 1073 K, and 433 K to 873 K (300 °C to 800 °C, 450 °C to 800 °C, and 160 °C to 600 °C). The integrated c...

In order to assess the life of gas turbine critical components, it is essential to adequately specify their aerothermodynamic working environments. Steady-state analyses of the flow field and conjugate heat transfer of an internally air-cooled nozzle guide vane (NGV) and shrouds of a gas turbine engine at baseline operating conditions are numerical...

In this research, two new Stellite alloys containing high tungsten are developed for wear resistance application owing to the distinct beneficial effects of tungsten in Stellite alloys. The microstructures of these alloys are analyzed using a scanning electron microscope (SEM) with an EDAX energy dispersive X-ray (EDX) spectroscopy system and X-ray...

Strain-controlled low-cycle fatigue (LCF) tests were conducted on ductile cast iron (DCI) at strain rates of 0.02, 0.002, and 0.0002/s in the temperature range from room temperature to 1073 K (800 °C). A constitutive-damage model was developed within the integrated creep-fatigue theory (ICFT) framework on the premise of strain decomposition into ra...

This paper presents an integrated creep-fatigue (ICF) theory to describe the non-linear creep-fatigue interaction during thermomechanical loading. The ICF theory recognizes the damage evolution as a holistic process consisting of nucleation and propagation of surface or subsurface cracks in coalescence with internally distributed damage, leading to...

The residual life assessment of a turbine spacer from a gas turbine engine is presented. The spacer has been identified as one of the safety critical components of the engine, therefore the useful life of this component significantly affects economic operation of the fleet. Numerical analyses of fatigue crack propagation at one critical location of...

Strain-controlled low-cycle fatigue (LCF) experiments were conducted on ductile cast iron at total strain rates of 1.2/min, 0.12/min and 0.012/min in a temperature range of RT 800°C. An integrated creep-fatigue (ICF) life prediction framework is proposed, which embodies a deformation mechanism based constitutive model and a thermomechanical damage...

The durability of thermal barrier coatings (TBCs) is controlled by fracture near the interface between the ceramic topcoat and the metallic bond coat, where a layer of thermally grown oxide (TGO) forms during service exposure. In the present work, the influence of thermal cycle frequency on the oxidation performance, in terms of TGO growth and crac...

A true-stress creep model has been developed based on well-recognized deformation mechanisms, i.e., dislocation glide, dislocation climb, and grain boundary sliding. The model provides a physics-based description of the entire creep deformation process with regards to the strain-time history (primary, secondary, and tertiary creep), rupture strain...

In this study, compressive dwell (C-D) and no-dwell (N-D) low-cycle fatigue (LCF) behaviours of several single crystal Ni-base superalloys, including CMSX-4, LSC-11 and LSC-15, were studied under strain-controlled zero-compression (RE = -co) loading at 1100°C. LSC-11 and LSC-15 are new alloys developed by 1H1 Corporation, Japan with 0.8 wt% Re and...

This paper presents an analytical fracture toughness model for brittle coating/ductile substrate systems. The model considers a well-developed radial/median crack of semi-elliptical shape in proximity of the coating/substrate interface. It incorporates three critical factors to correct Lawn et al.’s formalism for monolithic materials: (i) an ellipt...

Cold gas dynamic spray (CGDS) has been considered a potential technique to produce the metallic bond coat for TBC applications, because of its fast deposition rate and low deposition temperature. This article presents the influence of spray processes for bond coat, including air plasma spray, high velocity oxy-fuel, and in particular CGDS, on the o...

This article presents an experimental study of the tribological behavior of a tin/bronze-based composite coating. The improved-ductility Tribaloy alloy (T-401) particles are selected as the reinforcement. This coating is made on the bushing of planet journals used in aerospace engines, deposited with the high velocity oxygen fuel (HVOF) thermal spr...

Crack-face closure occurs physically at the compressive edges when a shell is subjected to bending loads. However, in traditional shell theories, crack closure effects are not concerned when evaluating the stress intensity factor (SIF). In reality, crack closure effects influence significantly the SIF. This article presents the theoretical and nume...

This article presents a study of solidification behavior and the corresponding microstructure of Co–Cr–W and Co–Cr–Mo alloy systems using the differential scanning calorimetry technique. The influence of main constituents on the solidification behavior and associate microstructures of these alloys are investigated. It is found that chemical composi...

Single crystal superalloy turbine blades exhibit anisotropic behaviors, and the stress at the fir-tree root often reaches the yield stress of the material when the turbine operates at the peak rotational speed and at the maximum temperature. The nonlinear behavior of the material character at these operating conditions poses a significant challenge...

Wear j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w e a r a b s t r a c t Lead-containing tin–bronze is one of the materials commonly used for journal bearings. However, due to the inherent toxicity of lead, environmental regulations around the world have been targeted to eliminate the usage of lead-containing bea...

Cold gas dynamic spray (CGDS) utilizes a supersonic gas jet to accelerate fine solid powders above a critical velocity at which particles impact, deform plastically, and bond to the substrate material in the ambient environment. This process is potentially beneficial for thermal barrier coating (TBC) bond coat deposition because it would avoid oxid...

The first work on Retrogression and Re-Aging (RRA) was performed over thirty years ago by Cina and his colleagues in Israel, in an attempt to achieve high levels of both strength and stress-corrosion-cracking (SCC) resistance in 7075 aluminum alloy, thus combining the best features of the T6 and T73 tempers. Their process, however, involved such sh...

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This article presents a study of solidification behavior and associate microstructure as well as hardness of Co-Cr-W-Ni and Co-Cr-Mo-Ni alloy systems. The differential scanning calorimetry (DSC) technique is employed to determine the transformation temperatures of these alloys. The focus is on investigating the effects of each constituent of the al...

A framework of integrated creep-fatigue (ICF) modeling is proposed based on the deformation decomposition rule that the total inelastic strain (in a polycrystalline material) consists of intragranular deformation (ID) and grain boundary sliding (GBS). With consideration of the respective deformation mechanisms, the resulting constitutive laws are g...

A group of novel polytetrafluoroethylene (PTFE)-based composite materials are developed for sliding bearing applications. The reinforcements include the newly developed T-401 Tribaloy alloy, which possesses better ductility compared to conventional Tribaloy alloys, spherical bronze particles, chopped carbon fibers and milled graphite. The specimens...

The degradation of a thermal barrier coating (TBC) system is dominated by the formation and growth of a thermally grown oxide (TGO) layer between the ceramic topcoat and metallic bond coat, leading to a separation near the ceramic/bond coat interface during service. Crack propagation in a thermally sprayed TBC normally proceeds via the opening and...

The durability of a thermal barrier coating (TBC) system is dominated by fracture near the interface between the ceramic topcoat and metallic bond coat, where a layer of thermally grown oxide (TGO) would form during service exposure. Even though the formation of a continuous alumina scale would help to protect the bond coat from further oxidation,...

The fracture strength of five HVOF coatings, which are made of hard metals, Tribaloy alloy, and superalloys, respectively, coated on 1018 low carbon steel substrate, is studied under Vickers indentation, associated with FEA stress computation. The cross sections of the coating specimens are examined on a Hitachi Model S-570 scanning electron micros...

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Tin–bronze-based composites with the newly developed tribaloy alloy additive, T-401 with the chemical composition of Co–17Cr–22Mo–1.2Si, are developed for journal bearing applications. Two types of tin–bronze are employed, one is in a premixed state, the other prealloyed. Different from conventional tribaloy alloys, T-401 has better ductility owing...

Life prediction methods have been evolving for many decades. Application of these methods is very important for economic operation of gas turbine engine fleets. The challenges in life prediction for gas turbine components arise due to their severe operating environments, such as high-temperature environments and corrosive-erosive high-speed gaseous...