P. Bowen's research while affiliated with University of Birmingham and other places
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Publications (221)
Finite element (FE) analysis modelling of crack configurations was used to provide insights into the role of time-dependent deformation on dwell fatigue crack growth (DFCG) in turbine disc alloys. In particular, the potential influence of time-dependent deformation on fatigue crack growth rates observed during dwell holding periods and the potentia...
Four–point bend (4PB) samples with seven notch configurations and three–point bend (3PB) samples with four notch configurations have been designed and tested in this study to evaluate the fracture behaviour of virgin Gilsocarbon graphite with simulated keyway notches. The effective stress concentration factor for Gilsocarbon graphite with simulated...
ASTM standards for tensile tests define specific sample size requirements regardless of grain size of the material. However, sample size requirements for testing should be considered in conjunction with the number of grains within its reduced cross-sectional area. This is particularly important for in-situ Scanning Electron Microscope (SEM) tensile...
In this research, an experimental evaluation of creep properties of Alloy 709 in the temperature range of 750–850 °C was undertaken. Alloy 709 is a novel austenitic stainless steel with 20% Cr and 25% Ni by wt% that was developed for application in structural components of nuclear power plants. Creep rupture tests were conducted in an in-situ heati...
Strain accumulation ahead of the fatigue crack tip in the martensite lath of a medium-carbon steel was examined using a three-dimensional electron backscatter diffraction (3D-EBSD) technique. The objective of this study is to explain the crack propagation mechanism due to the activation of out-of-plane slips with their Burgers vectors having no com...
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...
Two high strength Al alloys AA2050 and AA7010 have been joined using linear friction welding (LFW) in this study. Microstructural evolution across the weld line developed during linear friction welding has been examined. Their effects on mechanical properties have also been evaluated. A clean weld region where there is free of microcracking, microp...
Alloy 709 is a novel austenitic stainless steel with high temperature creep strength, weldability, and corrosion resistance. These properties make the material suitable for applications in the structure of next-generation nuclear power plants. Enduring high temperatures for an extended period of time in the harsh environments of a nuclear power pla...
Fatigue crack growth resistance of an austenitic stainless steel Alloy 709 has been evaluated at temperatures of 550, 650 and 750 °C in air and vacuum. Tests were conducted at a frequency of 0.25 Hz and a stress ratio of 0.1. The linear elastic stress intensity factor range (ΔK) has been used to characterise fatigue crack growth resistance. A modes...
Two new alloy compositions for possible disk rotor applications have been examined. Both were intended to have higher γ′ content than the existing alloy, RR1000, and be produced using powder metallurgy and isothermal forging to enable forgings to show a consistent coarse grain microstructure. Small pancake forgings of the new alloys and RR1000 were...
Two new alloy compositions for possible disk rotor applications have been examined. Both were intended to have higher γ′ content than the existing alloy, RR1000, and be produced using powder metallurgyPowder metallurgy and isothermal forging to enable forgings to show a consistent coarse grain microstructure. Small pancake forgings of the new alloy...
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...
Ni-based superalloys IN718 and IN713LC have been joined through linear friction welding (LFW) in this study. The variation of microstructure across the weld line developed during linear friction welding and after post weld heat-treatment (PWHT) has been investigated. Their effects on microhardness have also been studied. A clean weld region which i...
The surface integrity characteristics of Udimet 720Li subjected to slight damage and damage machining conditions have been studied using a complementary range of techniques such as FIB-SEM, EBSD, TKD, TEM-EDS and nano-indentation. The results indicate the existence of nano-sized grains and no observable tertiary γ′ in regions of severe plastic defo...
DAT54 is a new near a heat resistant Ti alloy developed for disk applications in the compressor part of jet engines. DTA54 with bimodal microstructure shows a good balance of fatigue strength and creep life, and performs better than Ti-6242s up to 873 K. However, the influence of microstructure on properties, especially the effect of the morphology...
The effects of influential fatigue testing factors, including loading schemes (e.g., traditional load shedding and staircase load increasing), morphology of crack starters, and precracking approaches on the near-threshold fatigue crack growth behaviors for a near lamellar γ-TiAl alloy (Ti-45Al-2Mn-2Nb-1B) were investigated at room temperature and 6...
Short crack phenomena are considered important for lamellar structures in γ-TiAl alloys and have been thoroughly investigated in the past. However, the short cracks in the previous studies were nearly all introduced artificially. No particular investigations have looked into the initiation of fatigue short cracks. Therefore, naturally initiated sho...
The creep-resistant austenitic stainless steel Alloy 709 (Fe-20Cr-25Ni (wt%) based steel) is being investigated as a candidate structural material for the next generation fast neutron reactors at service temperature of 500–550 °C. However, the study of microstructural evolution of Alloy 709 during aging is lacking. In this study, thus, the microstr...
A comprehensive experimental evaluation of the creep-fatigue behavior of Alloy 709 at 750 °C is reported in this study. Alloy 709 is a 20Cr–25Ni austenitic stainless steel, with high temperature creep strength and corrosion resistance, which can potentially be used in structural components of nuclear power plants. Creep-fatigue crack growth (CFCG)...
Alloy 709 austenitic stainless steel is being investigated as a candidate structural material for the next generation fast neutron reactors at service temperature of 500–550 °C. However, the study of deformation mechanisms on Alloy 709 and of tensile response of aged Alloy 709 is lacking. In this study, thus, the tensile behaviour of as-received an...
Microstructural fatigue crack growth in Ti–6Al–4V lamellar colonies was examined using small compact-tension specimens, with post-fatigue-test transmission electron microscopy for a mechanistic understanding of the anisotropy. In colonies oriented favourably for prismatic slip in the α phase, the crack grew by alternating shearing on two symmetrica...
John Knott was a leading expert in materials, fracture and structural integrity applied particularly to the fields of nuclear power generation and aero-engine applications. He made significant contributions to the quantitative scientific understanding of fracture processes in metals and alloys and its applications in engineering. His early work elu...
This work investigates coarsening behavior of strengthening precipitates (g') in coarse-grained RR1000 after isothermal exposure for various times (50 to 500 hours) at 700°C and 750°C. The impact of these isothermal treatments is then studied by carrying out dwell (1 hour) fatigue crack growth tests at 700°C in air. Such dwell periods can increase...
In recent years, there have been several advancements in energy production from both fossil fuels and the alternate “clean” sources such as nuclear fission. These advancements are fueled by the need for more efficient systems that will optimize the use of the depleting fossil fuel reserves and shift the focus to cleaner sources of energy. The effic...
The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 an...
Micro-tensile tests on single-colony specimens of Ti–6Al–4V alloy with a fine lamellar microstructure revealed that the critical resolved shear stress of the basal slip was lower than that of the prismatic slip. This has been attributed to easier slip transmission within the habit plane at the α/β boundaries.
Fatigue crack growth resistance has been assessed in continuous SCS-6 fibre reinforced Ti-6Al-4V composites from unbridged defects at room temperature, 300 and 450 °C in air and in vacuum. The initial applied stress intensity factor range (ΔKapp) (on the unbridged crack depth) was used to quantify the crack arrest/catastrophic failure (CA/CF) trans...
The effects of compressive residual stress on short fatigue crack growth in Inconel 718 have been investigated. Using two different indentation procedures, controlled plane-strain compressive residual stress fields were applied to short through-thickness cracks, which had been generated by machining away wakes of long cracks that had been grown dow...
Micro-bending tests were performed on single-crystalline cantilever beams of long-period stacking ordered (LPSO) structures of Mg85Zn6Y9 alloy with and without a notch to study crystal plasticity and cracking behaviour under basal and non-basal slip conditions. The activation of basal slip induced load drops during the deformation of a plain cantil...
The variation of microstructure and microtexture across a Ti-6Al-4V (Ti64) linear friction weld was investigated using scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Pole figures and misorientations distribution obtained from α phase show four distinct regions within the weld, with different textural characteristi...
Additive manufacturing has potential to fabricate or repair complex, net-shaped metal components with material usage and cost benefits. One such scenario is repair of damaged blisks (integrated blades and disk) used in gas turbines. In this paper the microstructure and texture of the Direct Laser Deposition (DLD) coupons in Ti-6Al-4V are investigat...
This paper investigates the relationships between microstructure and fracture toughness for a metastable beta titanium alloy, Ti-5553. A step-quenching procedure, which includes beta annealing, quenching to and soaking at an intermediate temperature, and final ageing, is applied to tailor the microstructure for optimal fracture toughness, after hot...
Different workpiece surface and subsurface conditions from machining operations involving high speed milling, reciprocal surface grinding and creep feed grinding together with polishing are investigated relating to the fatigue life of Ti–25V–15Cr–2Al–0.2C wt% alloy, with particular emphasis on the mechanisms of fatigue crack initiation. Stress reli...
The effects of prior oxidation on the room temperature fatigue life of coarse-grained Ni-based superalloy, RR1000, have been investigated. High cycle fatigue tests were conducted, on both machined and pre-oxidised testpieces, at room temperature at an R ratio of 0.1. The oxidation damage was produced by pre-exposures at 700 °C for either 100 or 200...
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In this work, we have extended our earlier work on the concept of ratchetting strain as a crack driving force (Tong et al., 2013), to examine the crack growth of a nickel-based superalloy at selected temperatures in vacuum under both fatigue and fatigue-creep loading conditions. The parameters of a unified constitutive model were calibrated against...
The microstructure of direct laser deposited (DLD) IN718 has been investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that the dendrite core microstructure can be linked to the cooling rate experienced during the deposition. A ~ 100 μm wide δ partially dissolved region in t...
The influence of microstructure on the dwell fatigue crack growth behaviour of an advanced nickel-based superalloy was investigated at a temperature of 700 °C. Microstructural variations were induced by heat treatment variables: different cooling rates of quenching from super-solvus solution heat treatment, 0.7 and 1.8 °C s−1, and an addition of a...
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The deformation mechanisms associated with different fracture surface appearances of a fatigue tested lamellar TiAl-based alloy have been studied in detail by focussed ion beam and transmission electron microscopy. The results show that linear markings within translamellar plates correspond to twins and/or slip bands. The markings in interlamellar...
The effect of prior oxidation on the room temperature fatigue life of coarse grained Ni based superalloy, RR1000 has been performed at an R ratio of 0·1 with two pre-oxidation times: 100 and 2000 h at 700°C. These pre-exposures produce extensive oxidation damage. The room temperature high cycle fatigue life of the pre-oxidised specimens has been co...
Previous observations on Ni based superalloys, obtained through the use of focused ion beam (FIB) sample preparation and imaging, have reported the presence of subsurface voids after oxidation. In this present study, oxidised specimens of the Ni based superalloy, RR1000, were subjected to conventional sample preparation as well as both dual and sin...
RR1000 is one of an advanced class of nickel-based superalloys developed for disc applications. Under one hour dwell fatigue loading, complex crack growth behaviour has been observed especially in a coarse grained version of this alloy. At a temperature of 700 °C in air an increase of nearly two orders of magnitude in crack growth rates compared to...
At high temperatures in air, introducing a dwell period at the peak stress of fatigue cycles promotes time dependent intergranular crack growth which can increase crack growth rates by upto a few orders of magnitude from the rates of transgranular fatigue crack growth in superalloys. It is expected that time dependent intergranular crack growth in...
A study of the interfacial properties of a SiC (SCS-6) fibre reinforced Ti-6Al-4V metal matrix composite has been carried out using a fibre push out technique. Material in the as received condition, heat treated at 300°C, and some fatigue damaged conditions were considered. Fatigue was performed in 3-point bending at two initial ΔKapp levels at bot...
A comparison of literature data indicates that intergranular oxide intrusions formed in the nickel-based superalloy RR1000 ahead of stationary cracks grow at a rate higher than that observed on flat surfaces. This is attributed to the effect on vacancy equilibria of the tensile stress that exists at the tip of the intrusion. A stress-aided oxidatio...
Oxide intrusions which formed ahead of the crack tip in an advanced nickel-based superalloy after exposure to air at 650 °C have been investigated by (scanning) transmission electron microscopy equipped with energy-dispersive X-ray spectrometry. Three different cases were considered: (i) a fast growing crack; (ii) a stationary crack exposed to a 5...
The microhardness and microstructure of linear friction welded Ti–6Al–2Sn–4Zr–6Mo (Ti6246) alloys were studied, in both as-welded and post-weld heat-treated conditions. It has been found that the as-welded Ti6246 has a lower microhardness value of about 360 HV in the central weld zone than that of the base material of about 420 HV. Post-weld heat-t...
A study of the interfacial properties of a SiC (SCS-6) fibre reinforced Ti-6Al-4V metal matrix composite has been carried out using a fibre push out technique. Material in the as received condition, heat treated at 300°C, and some fatigue damaged conditions were considered. Fatigue was performed in 3-point bending at two initial ΔKapp levels at bot...
High temperature oxidation resistance is becoming increasingly important to component life as operating temperatures increase. Additionally, shot-peening is used to help extend the service life of high-duty components through inducing compressive stresses in the surface. The effect of shot-peening on oxidation resistance has not been examined in de...
One of the main obstacles to Friction Stir Welding (FSW) for the joining of Ti-alloys is the development of a tool material that can withstand the high temperatures (~>1000˚C) and stresses of the process without breaking. In addition it must be inert with Titanium. In this investigation, a number of tools of different materials were used to join Ti...
The α/β alloy Ti-6Al-4V (Ti-64) is extensively used in aerospace industry due to its good balance of properties, and being one of the most developed and tested titanium alloys. The application of linear friction welding (LFW) technology to join Ti-64 to itself has necessitated the mechanical assessments of fatigue and fatigue threshold of the welde...
Characterization of dissimilar linear friction weld (LFW) of Ti-alloys has been carried out. The microstructure of a Ti-64 with Ti-6246 weld was analyzed using scanning and transmission electron microscopy. The microtexture of the weld was examined using electron back-scattered diffraction (EBSD) and the microhardness was measured. The dissimilar L...
Small fatigue cracks in the aluminium alloys 2024-T351 and 8090-T8771 have been observed to grow by a heterogeneous process of three-dimensional slip band decohesion. Local, finely-divided crack path excursions at slip bands, the pull-out of small sections of decohered slip band and the formation of fatigue extrusions at slip bands produced micro-r...
Microstructure 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 st...
Fracture tests have been carried out on micro-sized specimens prepared from a fully lamellar γ-TiAl based alloy thin foil. Micro cantilever beam type specimens with dimensions = 50 × 10 × 20 μm were prepared from one lamellar colony of the thin foil by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 10 μm were also introdu...
A complex two phase γ-TiAl alloy, Ti-47Al-1Cr-1Mn-2Ta-0.2Si (at.%) in a fully lamellar condition, has been creep tested at a stress of 200MPa and a temperature of 700°C. This simulates the in-service operating conditions for several potential gas turbine aero engine applications where creep resistance is a design limiting material property. The res...
The fatigue crack growth resistance of a Ti–48Al–2Mn–2Nb (at.%) alloy with different lamellar spacings was investigated at room temperature in laboratory air. The crack growth resistance in the air-cooled specimen with a lamellar spacing of ∼0.9μm was essentially higher than that in the furnace-cooled specimen with a lamellar spacing of ∼3.8μm. The...
The inertia friction welding process is being extensively investigated for the joining of high strength titanium alloys for aerospace applications. Although it offers solid state joining, the thermal cycle and deformation involved results in microstructural inhomogeneity across the weld interface. In this paper, the fatigue crack propagation behavi...
The contact interface of an inertia friction weld made from a dissimilar material combination of Aermet 100 and SCMV is modelled as a high temperature thin film undergoing high shear rates that behaves as a non-Newtonian fluid. Flow stress data is used to characterize an Arrhenius relationship for the viscosity of the material. It is also used to e...
This paper presents a mechanism-based approach for modelling the thermomechanical behaviour of a Cr-Mo-V steel. A set of unified viscoplastic constitutive equations were employed to model dislocation density, recrystallisation and grain size during deformation. The evolution of dislocation density accounts for the build-up of dislocations due to pl...
Sequential synchrotron X-ray microtomography and diffraction have been applied to follow the growth of fatigue cracks and the associated load redistribution in a Ti/SiC fibre composite. A sequence of micron resolution tomographs reveal for the first time how the cracks progress from ply to ply around the fibres. Complementary high spatial resolutio...
The interfacial strength of β-Ti composites was increased via ageing, to investigate the effects of interfacial strength on
the crack opening. Prior to crack opening displacement (COD) measurements, the number and location of fractured fibres were
identified by acoustic emission and fibre probing techniques. This was later used to model the crack o...
Abstract— A three dimensional, elastic-plastic, finite element analysis of fatigue crack growth and plasticity-induced crack closure has been performed for a range of small, semi-circular cracks. Predicted crack opening displacements have been compared with data obtained from in-situ SEM measurements for a coarse-grained aluminium alloy 2024-T351....
Fatigue crack growth resistance of metastable β titanium composite was investigated in different heat treatment conditions. The effects of increased interfacial strength due to peak ageing on the fatigue crack growth, crack opening displacement and fibre bridging were examined and results of fibre fractures monitored by acoustic emission and fibre...
In the present study inertia friction welded RR1000 to IN718 joints have been investigated. Crack growth tests within 0·3 mm of the weld interface, conducted in air at 500 and 650°C, have shown that there is no difference in crack growth rate due to three different sets of welding parameters applied. The cracks were found to propagate from RR1000 t...
The high temperature fatigue performance of two dissimilar material joints made by inertia friction welding and linear friction welding is assessed in the present study. The fatigue strength of the welded joints is found to be comparable to that of the weaker parent material for the plainsided specimens. However, the fatigue crack growth resistance...
Electronic Speckle Pattern Interferometry (ESPI) is used in conjunction with a mechanical test rig to determine the tensile property response when loading cross weld tensile samples of Tungsten Inert Gas (TIG) and Electron Beam (EB) welded Inco718, which include the parent metal, Heat Affected Zone (HAZ) and weld metal. A comparison with cross weld...
In situ SEM measurements and observations of crack opening displacement (COD) have been made during unloading of small mode I and mixed-mode fatigue cracks in samples of the aluminium alloys 2024-T351 and 8090-T8771. Changes in COD with decreasing load were used to measure mode I and mode II crack closure levels. The cracks were self-initiated, sur...
This article describes a comprehensive microstructural characterization of an inertia friction welded joint between nickel-based
superalloys 720Li and IN718. The investigation has been carried out on both as-welded and postweld heat-treated conditions.
The detailed metallographic analysis has enabled the relation of hardness profiles across inertia...
Abstract Crack closure has been measured for a range of small, self-initiated fatigue cracks using in situ SEM loading. Cracks were grown at positive R ratios in the aluminium alloy 2024-T351 and at nominal ΔK levels that extend substantially below the corresponding long crack threshold. The crack closure stress of the small cracks decreased and th...
ABSTRACTγ-TiAl-based materials have the ability to provide superior creep strength, high yield strength and Young's modulus at temperatures as high as 700 °C. This has led to the consideration of γ-TiAl-based materials for use in microelectromechanical systems (MEMS) intended for application at elevated temperatures. One γ-TiAl-based material under...
Low-alloy steels serving for a long time at high temperature (∼500 °C) are very sensitive to temper embrittlement due to segregation
of various trace elements at prior austenite grain boundaries and/or carbide/matrix interfaces. This type of segregation in
combination with various environmental effects can adversely affect the fracture resistance a...
The effects of microstructure and prestraining and static strain - ageing have been assessed in terms of fracture toughness properties in A533B submerged - arc welds. Testpieces were machined carefully so that the fatigue pre - crack tip was located in as - deposited (AD) microstructure alone and reheated (RH) microstructure alone within a multi -...
Low alloy steels operating for long times at temperatures of ∼ 500°C may be sensitive to embrittlement owing to the segregation of various trace elements to prior austenite grain boundaries and/or carbide/matrix interfaces. This type of segregation can adversely affect the resistance of the steel to fracture; this is associated with a change in fra...
The goal of this work was to evaluate the effects of particle size, particle volume fraction, and matrix strength on the monotonic fracture properties of two different Al alloys, namely T1-Al2124 and T1-Al6061, reinforced with silicon carbide particles (SiCp). From the tensile tests, an increase in particle volume fraction and/or matrix strength in...
Specimens of both as-deposited and reheated submerged arc weld MnMoNi weld metal have been subjected to plastic deformation and static strain-aging treatments. These treatments were carried out in an attempt to simulate some aspects of the thermomechanical conditions occurring in pressurised water reactor components such as the ferritic pressure ve...
Samples of fully lamellar titanium aluminides with randomly orientated colonies were exposed to single and multiple overloads. Damage was monitored by acoustic emission to determine its extent, its microstructural location, and to consider how damage may be introduced under single and multiple loading. The samples were then exposed to cyclic fatigu...
Adhesively-bonded aluminium single lap shear joints were tested to failure under fatigue loading to ascertain the effects of surface pretreatment and moisture in both durability and fracture path. The aluminium substrate used was AA5754 with and without a silicon-based pretreatment. The adhesive used was a commercially available DGEBA-based epoxy r...
Samples of Ti–6Al–4V (wt.%) were tested to failure under low cycle fatigue (LCF), high cycle fatigue (HCF), and combined cycle fatigue (CCF), respectively, in order to ascertain the effects of the combined cycle situation upon the total fatigue life. The results indicate that the effect of the combined loading is variable and dependent upon the con...
In general, the low-temperature brittle fracture mode of unembrittled ferritic steel is transgranular cleavage. During temper embrittlement, impurity elements, such as sulfur (S), phosphorus (P), antimony (Sb), arsenic (As), and tin (Sn), segregate to prior austenite grain boundaries, which results in a decrease in the grain boundary cohesive stren...
The main aim of this work was to study the effects of particle size, particle volume fraction, and matrix strength on the
long fatigue crack growth resistance of two different grades of Al alloys (Al2124-T1 and Al6061-T1) reinforced with SiC particles.
Basically, it was found that an increase in particle volume fraction and particle size increases...
The fracture toughness of Al2124/Al2124+SiC bimaterials is affected by thermal residual stresses, elastic/plastic mismatch, precrack tip position, and failure mechanism. When the precrack tip is in the Al2124 side, final catastrophic failure occurs when ductile fracture of the Al2124 layer between the precrack tip and the composite side takes place...
The present study describes the fatigue crack growth behavior of [0/90]2s and [90/0]2s laminates of Ti–6Al–4V/SCS-6 composite containing either part-through thickness or through thickness defects under a constant load range at room temperature in air. This study also compares the effect of composite architecture on the fatigue crack growth resistan...
The aim of the paper is to study the partitioning of stress between bridging and broken fibres and the nearby matrix in the region around a fatigue crack in the matrix of a Ti–6Al–4V/SCS–6 SiC fibre composite. This was achieved by using synchrotron X-ray radiation to perform a combination of high spatial resolution tomographic imaging and strain ma...
In addition to the inherent fracture toughness of each bimaterial component, K
Q
(5 pct) values of the Al2124/Al2124 + SiC bimaterials are largely affected by the thermal residual stresses, the elastic/plastic mismatch, and the precrack tip position. Regardless of the precrack tip distance to the interface, K
Q
(5 pct) values are increased in gener...
Fatigue S-N (stress vs life) curve behavior for a powder metallurgy (PM) Ni-base superalloy UDIMET 720 in both polished and shot-peened surface
conditions was investigated at room temperature and 600 �C in air. Tests were carried out under four-point bending at a load
ratio of 0.1 and a frequency of 10 Hz. At 600 �C, an offset S-N curve was found f...
Fatigue S-N (stress vs life) curve behavior for a powder metallurgy (PM) Ni-base superalloy UDIMET 720 in both polished and shot-peened surface
conditions was investigated at room temperature and 600 °C in air. Tests were carried out under four-point bending at a load
ratio of 0.1 and a frequency of 10 Hz. At 600 °C, an offset S-N curve was found f...
The paper reviews published data which address the effect of machining (conventional and non-conventional processes) and the resulting workpiece surface topography/integrity on fatigue performance, for a variety of workpiece materials. The effect of post-machining surface treatments, such as shot peening, are also detailed. The influence of amplitu...
The fatigue crack growth of long and small surface cracks has been investigated in air under four-point bending conditions at a load ratio of 0.1 for a PM Ni-based superalloy, Udimet 720. Cracks were found to initiate from surface pores despite an increased level of inclusions introduced by doping. Attention has been focused on small fatigue crack...
An experimental study was carried out on cross-ply Nicalon/CAS-II glass–ceramic matrix composite under monotonic, static, cyclic and a combination of static and cyclic loadings. Tests were carried out at room temperature (20 °C) and 800 °C in air with varying levels of peak stress, stress ratio and loading history. At room temperature and 800 °C, t...