bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison Study of Different Reliability-Based Design Optimization Approaches
Authors: El Hami A. , Radi Bouchaib
Published: July 2011

In this paper, we present a new method based on Optimal Safety Factors (OSF) in the context of the Reliability-Based Design Optimization (RBDO) analysis of ultrasonic motors with traveling wave taking into account the contact between the different components (stator and rotor). We will underline also the different methods of the RBDO analysis and we highlight the advantage of our approach based on OSF. Numerical results are given to illustrate the proposed method.
Simulation and Analysis of the Structure of Laminar Premixed Flame
Authors: Renane R. , Serro-Guillaume Olivier , Nour A. , Allouche R.
Published: July 2011

The aim of our work is to contribute to the analysis of the structure of laminar premixed Methane-Air flames using two methods. This allows us to validate the chemical mechanisms, to know the fine structure of the flame front and to get, for a given pressure and temperature of fresh gases, the speed and the mass fractions of all chemical species of the combustion reaction. The first method is based on controlling combustion parameters of laminar premixed flame. The numerical resolution strategy used consist in the discretization of the balance equations completed by the transport properties and the thermodynamic variables expressions, as well as the kinetic mechanisms concepts of chemical reactions and boundary conditions, using the first-order finite difference spatial scheme technique. The final solution is obtained, thereafter, iteratively using a recursive method. The calculations stop when equilibrium is reached. The second method consists in the use of FDS (Fire Dynamics Simulator) in order to simulate the propagation speed of the flame for different equivalence ratio in the cylindrical combustion chamber. This geometry is used by Tahtouh et al. (2009), and Bouvet et al. (2010) in their experimental devices for calculating the flame velocity. This study examines the influence of temperature variation of unburned gases on the structure of the flame front, as well as the effect of equivalence ratio on the flame front speed, combustion products and pollutants formation that allows us to deduce which parameters ensure higher efficiency with less fuel consumption and fewer pollutants.
Delta Wing-Fuselage Interactions - Experimental Study
Authors: Boumrar I. , Ouibrahim A.
Published: July 2011

Experiments were conducted on thin delta wings to investigate, for subsonic flow, the effect of both privileged apex angle values and the wing-fuselage interactions on the aerodynamic characteristics, i.e. the distribution of the defect pressure on the extrados, the drag and the lift coefficients. For this purpose, several delta wing models of various apex angle (β = 75, 80 and 85°) were realized and tested without and with fuselages of cylindrical form, with diameters of 20 and 30 mm, downstream the apex and appropriately disposed on the extrados. The impact of the apex angle as well as the interaction on the defect pressure were specially considered along the apex vortices where the pressure defect is usually maximum. The above mentioned effects were investigated via the variations of the mean velocity in the wind tunnel and the incidence (attack) angle.
Aircraft Joints: the Interaction between Corrosion Protection and Structural Performance
Authors: Clark Graham , Tiong Ung Hing , Jaya Aditya
Published: July 2011

Aircraft joints feature prominently in aircraft structural degradation. Fatigue cracking and corrosion damage can reduce joint strength and degrade service life. Corrosion management can include use of paints and sealants and, increasingly, the application of Corrosion Inhibiting Compounds (CICs) which retard corrosion, by penetrating into crevices and cracks, and displacing water. A combination of coatings and CIC use can provide effective corrosion protection, but both interact - in different ways - with structural performance and overall system durability. This paper discusses the interaction between these two corrosion protection measures and fatigue performance of joints. The first issue relates to a reduction in the fatigue life of mechanically-fastened joints after application of CICs (or other lubricants) The lubricating properties of the CICs reduce the friction at the faying surface, which may change the load transfer characteristics of the joint. The paper discusses results from a test program assessing the fatigue life and failure mode of riveted lap joints; the results show a marked reduction in fatigue life for joints containing CICs, and the paper discusses the changes which may be responsible for the reduction. The second issue discussed is the degradation of protective coatings in service. Joints are key locations for coating cracking and failure, since areas such as sheet ends and fastener heads, where displacements are concentrated, will produce concentrated strain in coatings. So far, however, the potential influence of aircraft loading on coating degradation prognostics has received little attention. The paper discusses the role of joint displacement in service as a factor contributing to early degradation of aircraft coatings, and argues that this local strain effect, and indeed structural loading history, needs to be considered in predicting and assessing rates of coating degradation. It describes initial analyses of displacements in aircraft joints, to identify the levels of coating strain and the roles and relative contributions of the various deflections in the joints. The results indicate the potential for very large strains in coatings.
Influence of Heat Treatment on Fatigue Strength of Drawn Steel Tubes for Small-Sized Single Pass Boiler
Authors: Yonekura Daisuke , Fujie Yuta , Nishii Hayato , Yamakawa Hiroshi , Murakami Riichi
Published: July 2011

Tension-tension fatigue tests were performed to examine the influence of post drawing heat treatment on the fatigue properties of drawn specific steel tube (STB340) for small-sized single pass boiler. The untreated, as-drawn and post drawing heat treated series were prepared for fatigue tests. The hardness, grain size and residual stress were measured for each series. As a result, the change of grain size and residual stress was small after post heat treatment. The drawn series was softened by post heat treatment but the hardness was still higher than untreated samples. The fatigue strength of the as-drawn and the post drawing heat treated series was higher than that of untreated series. In addition, the difference of endurance limit was small between as-drawn and post drawing heat treated series.
Effects of Crack Size and Crack Face Interference on Shear Fatigue Crack Growth in a Bearing Steel
Authors: Shomura Naoya , Yanase Keiji , Matsunaga Hisao , Endo Masahiro
Published: July 2011

The near-threshold fatigue behavior of small, semi-elliptical surface cracks in a bearing steel was investigated under cyclic shear-mode loading in ambient air. Fully-reversed cyclic torsion was combined with a static axial compressive stress to obtain a stable shear-mode crack growth in the longitudinal direction of cylindrical specimens. Shear stress amplitude was gradually decreased with an increase in crack length and the crack finally became non-propagating. Abrasive wear on the crack faces was inferred by debris and also by changes in microstructure in the wake of crack tip. Further, it was found that these effects resulted in a significant decrease in the crack growth rate. In this study, we shed light on the important role of the crack size and crack face interference on the crack growth behavior.
Friction and Wear Characteristics of SUS304 and SUS630 after Ultrasonic Nanocrystal Surface Modification
Authors: Pyoun Young Shik , Park Jeong Hyeon , Suh Chang Min , Amanov Auezhan , Kim Jun Hyong
Published: July 2011

Owing to the superior properties of stainless steel it is pertinent to make use of it in various applications of automotive, aerospace, nuclear, chemical and cryogenic products. This paper describes a study of friction characteristics of SUS304 and SUS630 stainless steel disk specimens against silicon nitride Si3N4 ball in dry, grease-, and oil-lubricated conditions and wear characteristics in dry condition in sliding contact. The ultrasonic nanocrystal surface modification (UNSM) technology was applied to those disk specimens and its friction and wear properties were compared with polished one. The experiment was conducted with a pin-on-disk tribo tester using ball-on-disk contact geometry at room temperature. The experiment results show that in dry, greased- and oil-lubrication conditions the coefficient of friction of UNSM-treated specimens was lower and constant than polished specimens and in dry condition the wear rate was also smaller than polished one. Micro dimples made by UNSM treatment contribute those effects.
Improvement of Biocompatibility of Medical Ni-Ti Alloys through Forming TiO2 Thin Film
Authors: Kimura Yuji
Published: July 2011

Ni-Ti alloys have been investigated for applying to various surgical procedures. However, little is known about the toxicity of Ni-elements and the actual conditions of surface modification of Ni-Ti alloy for preventing the toxicity of Ni. In this study, the corrosion resistance of Ni-Ti alloys was improved through making TiO2 thin film by conducting in air oxidation and reactive sputtering. These thin films were characterized using FE-SEM, XRD, XPS and AFM. And judging from the polarization curves obtained by electro-chemical measurement in quasi-living body environment, corrosion resistance of Ni-Ti super elastic alloy was evaluated. From these considerations, some trials for establishing a method for TiO2 thin film formation on the surface of Ni-Ti alloy were conducted from the view point of improving biocompatibility.
A Model for the Cyclic Behaviour of Steel under Earthquake Conditions
Authors: Seal C.K. , Hodgson M.A. , Ferguson W. George
Published: July 2011

During the mid 1990s earthquakes in Northridge, California, and Kobe, Japan, illustrated a lack of understanding of the behaviour of structural steels exposed to seismic loads. Under this type of load regime, structural steel members are subjected to fully plastic load cycles and unexpectedly brittle failures resulted. This paper presents a simple, yet powerful, method for predicting the accumulation of damage in a steel element, based on its toughness. In addition the damage parameter chosen provides an accurate prediction of when failure of the element can be expected to occur. The damage accumulation model developed allows for the deconvolution of complex load histories, such as could be expected to occur during a seismic event, in a systematic, stepwise manner. This approach is ideally suited to automation and could readily be implemented into a finite element model.
Tool Wear Mechanisms during Machining of Alloy 625
Authors: Fusova Lenka , Rokicki Pawel , Spotz Zdeněk , Saksl Karel , Siemers Carsten
Published: July 2011

Nickel-base superalloys like Alloy 625 are widely used in power generation applications due to their unique properties especially at elevated temperatures. During the related component manufacturing for gas turbines up to 50% of the material has to be removed by metal cutting operations like milling, turning or drilling. As a result of high strength and toughness the machinability of Alloy 625 is generally poor and only low cutting speeds can be used. High-speed cutting of Alloy 625 on the other hand gets more important in industry to reduce manufacturing times and thus production costs. The cutting speed represents one of the most important factors that have influences on the tool life. The aim of this study is the analyses of wear mechanisms occurring during machining of Alloy 625. Orthogonal cutting experiments have been performed and different process parameters have been varied in a wide range. New and worn tools have been investigated by stereo microscopy, optical microscopy and scanning electron microscopy. Energy-dispersive X-ray analyses were used for the investigation of chemical compositions of the tool's surface as well as the nature of reaction products formed during the cutting process. Wear mechanisms observed in the machining experiments included abrasion, fracture and tribochemical effects. Specific wear features appeared depending on the mechanical and thermal conditions generated in the wear zones.
Effect of Pb and Sn Additions on the Ductility of Cast AZ61 Mg Alloy
Authors: Liu Hong Mei , Gao Wei
Published: July 2011

AZ61 alloy is an important magnesium (Mg) alloy which can be rolled at elevated temperature. However, the insufficient ductility of as-extruded alloys limits their design and applications. Pb or Pb+Sn additions lead to a high ductility (~18% at room temperature) and good tensile strength (~250 MPa). This paper discusses the mechanism of property enhancement and the influence of Pb addition on the solidification process of AZ61 alloy.
Fracture Toughness of Polyamide 6/ Maleated Styrene-Ethylene-Butylene-Styrene/Silicon Carbide Nanocomposites
Authors: Liao Cheng Zhu , Tjong Sie Chin
Published: July 2011

Polyamide 6 (PA6) based nanocomposites toughened with 20 wt% maleated styrene-ethylene-butylene-stryrene (mSEBS) reinforced with 1-7 wt% silicon carbide nanoparticles (SiCp) were fabricated via melt blending followed by injection molding. Tensile results showed that SiCp additions improve the Young’s modulus and tensile strength of PA6/mSEBS blends but decrease their tensile ductility and impact strength. EWF test revealed that the SiCp additions reduce both the specific essential work of fracture and specific non-essential plastic work of fracture. Thus SiCp additions are detrimental to the fracture toughness of PA6/mSEBS blend.
The Influence of Processing Parameters on the Void Content and Compressive Strength of Carbon Fibre-Epoxy Laminates
Authors: Yuan Xiao Wen , Bickerton S. , Bradley Samuel , Tapiheroe Arry , Little John
Published: July 2011

This research addresses the influence of various processing parameters on the post cure quality of carbon fibre composites. Four processing parameters were investigated in the study, in terms of their impact on void content and overall compressive strength. The first parameter distinguishes between laminates cured in a vacuum oven and those cured in an autoclave under high positive pressure. The second parameter describes the impact on voids of differing fibre architectures, comparing a unidirectional fibre structure to that of woven cloth. Thirdly, the influence of compaction during manufacture is analysed and lastly, variation in cure temperature was tested to determine its effect on final laminate quality. The quality of the cured laminate samples was assessed from visual inspection, and in terms of compressive strength and void fraction calculated by Micro-CT X-ray Tomography. The results show that autoclave-cured samples feature significant quality improvements in terms of void fraction and compressive strength when compared to oven-cured samples. Unidirectional laminates incur higher sensitivity to void inclusion than cloth laminates due to the influence of fibre wrinkling. Compaction has no effect on laminate strength; it does however reduce variability in certain cases. Temperature affects different fibre structures in different ways, these being highly dependent on curing method. Finally, it was discerned that curing by autoclave was the dominant processing parameter. Thus, regardless of other manufacturing techniques, the autoclave samples featured almost zero voids and were consequently of the highest quality.
An Artificial Neural Network Approach to Fatigue Crack Growth
Authors: Zarrabi K. , Lu W.W. , Hellier A.K.
Published: July 2011

This paper proposes a new three-layer artificial neural network (ANN) to predict the fatigue crack length under constant amplitude mode I cyclic loading. It is shown that the proposed model predicts the crack length with an error of less than 0.05%, and more accurately than the current commonly-used models.
An Analysis of Fatigue Strength of Notched Components
Authors: Shingo Toshiya , Yanase Keiji , Matsunaga Hisao , Endo Masahiro
Published: July 2011

Geometrical discontinuities in the engineering components, such as holes, fillets, grooves, and keyways, are unavoidable in design. In essence, they act as a stress-raiser that causes the fatigue cracks. Accordingly, the geometrical discontinuities trigger a significant amount of reduction for the fatigue strength. It is well known that the fatigue limit of the notched components is governed by either the initiation or propagation of a small crack at the root of a notch. Since the elastoplastic behaviors and the crack closure effect should be properly taken into consideration, the behavior of such a small crack cannot be characterized solely by linear elastic fracture mechanics. To overcome the difficulty mentioned above, in this study, a novel method is proposed to investigate the notch effect by making use of the McEvily method, which has been widely used for the analysis of small fatigue crack growth. Further, to modify the McEvily method, the plastic zone size of a crack is calculated based on the Dugdale model to incorporate the effect of the plastic yielding near the crack tip. Finally, the predictive capability of the proposed method is demonstrated by comparing our theoretical predictions with the available experimental data.
Experimental Investigation of PMMA Fracture under Mixed-Modes I, II and III Loading
Authors: Zarrabi K. , Karpour A. , Hellier A.K.
Published: July 2011

Fracture studies of components involving mode III loading are rare. This paper concentrates on mixed-modes I, II and III fracture testing of brittle PMMA material and summarises an extensive experimental investigation. Karpour and Zarrabi have developed a special pair of grips for which they have received a patent. These grips allow the application of various mixtures of modes, including mode III, using a universal testing machine. To measure the three-dimensional crack-tip opening and sliding displacements, Karpour and Zarrabi have also developed a novel stereo machine vision system whose description is included in the paper. The measured critical crack-opening displacements presented in normalised format with potential of being used to assess the integrity of any component against elastic fracture and they compare well with limited pertinent data available from literature.
Fracture Strengths of Mg Alloy AZ31B-H24 Friction Stir Lap Welds
Authors: Chen Zhan W. , Yazdanian Shamzin , Littlefair Guy
Published: July 2011

The effects of selected friction stir lap welding parameters on fracture strength of Mg alloy AZ31B-H24 welds have been studied. Rotation speed has been found to affect significantly the flow related hook size formation. Furthermore, fracture strength decreased almost linearly with hook size. A small amount of softening was detected in fracture location that was outside the nugget zone and thus this softening may only adversely affect the fracture strength slightly. Finally, simulation results are presented to show the uneven stress distribution in a lap geometry which together with the relative brittleness of the stir material must be the cause to have significantly reduced the fracture strength.
Microindentation of Microencapsulated Phase Change Materials
Authors: Rahman Asif , Adschiri Tadafumi , Farid Mohammed
Published: July 2011

Due to the small size of microcapsules (1-1000 µm) used in a large number of applications, the individual rupture force of an individual particle has been difficult to obtain. A new technique involving nanomechanical testing was used in this study. We propose a standard method of testing the individual rupture force of Micronal®DS5008 microcapsules with an average size of approximately 11.2µm. Microcapsules were subjected to compressive force testing to determine the amount of force required to rupture the microcapsules. In order to find the mechanical properties of these microcapsules a standard nanoindentation system was setup with a 10µm radius diamond head cone indentation tip and the individual microcapsules were compressed till rupture occurred.
Managing Potlife through Statistical Analysis
Authors: Lavoie Pascal
Published: July 2011

A significant portion of ongoing costs in aluminium smelters comprises of electrolysis cell reconstruction. The cells, also referred as pots, undergo different wear mechanisms and failure modes determining their finite lifespan. Smelters have to carefully manage all aspects determining potlife to maximize it while minimizing reconstruction costs. Pot design, materials and supplier selection, construction quality and electrolysis operations all affect potlife.
On-Chip Tensile Testing of the Mechanical and Electro-Mechanical Properties of Nano-Scale Silicon Free-Standing Beams
Authors: Bhaskar Umesh , Passi Vikram , Zulfiqar Azeem , Södervall Ulf , Nilsson Bengt , Petersson Goran , Hagberg Mats , Pardoen Thomas , Raskin Jean Pierre
Published: July 2011

A simple and versatile on-chip tensile testing method is proposed for the statistical evaluation of size effects on the mechanical strength of silicon thin films along with the simultaneous study of (from low to ultra) strain effects on the carrier transport. Mechanical results are presented on the fracture strength of micro-nano scale silicon beams, followed with a discussion on interface states and problems facing reliable nano-electronic and nano-electromechanical characterizations.
Non-Standard FinFET Devices for Small Volume Sample Sensors
Authors: Zaborowski Michal , Tomaszewski Daniel , Łukasiak Lidia , Jakubowski A.
Published: July 2011

The presented work is focused on development of silicon wire-based MOS devices. .The original fabrication method has been described. Electrical performances of a variety of devices have been measured and evaluated. As these devices will be used as a platform for detectors of biochemical molecules, also tests of device operation oriented towards sensor applications have been done.
Interface and Bulk Properties of High-K Gadolinium and Neodymium Oxides on Silicon
Authors: Gomeniuk Y.Y. , Gomeniuk Y.V. , Nazarov A. , Lysenko V.S. , Osten H.J. , Laha A.
Published: July 2011

The paper presents the results of electrical characterization of the interface and bulk properties of high-k Gd2O3 and Nd2O3 dielectrics epitaxially grown on silicon substrates. The limitations of the conductance technique for correct determination of the interface state density due to the presence of leakage currents through the dielectric are discussed. The charge carrier transport through the dielectric film was found to occur via the variable-range hopping conductance mechanism. The density of the interface states and their energy distribution for (100) and (111) Si orientation and the Gd2O3/Si and Nd2O3/Si interfaces were determined. The density and energy location of the bulk localized states in the band gap of the Gd2O3 and Nd2O3 dielectrics were estimated and a plausible nature of the observed defects was suggested.
Electrical Properties of High-K LaLuO3 Gate Oxide for SOI MOSFETs
Authors: Gomeniuk Y.Y. , Gomeniuk Y.V. , Nazarov A. , Hurley P.K. , Cherkaoui Karim , Monaghan Scott , Hellström Per Erik , Gottlob H.D.B. , Schubert J. , Lopes J.M.J.
Published: July 2011

The paper presents the results of electrical characterization of MOS capacitors and SOI MOSFETs with novel high-κ LaLuO3 dielectric as a gate oxide. The energy distribution of interface state density at LaLuO3/Si interface is presented and typical maxima of 1.2×1011 eV–1cm–2 was found at about 0.25 eV from the silicon valence band. The output and transfer characteristics of the n- and p-MOSFET (channel length and width were 1 µm and 50 µm, respectively) are presented. The front channel mobility appeared to be 126 cm2V–1s–1 and 70 cm2V–1s–1 for n- and p-MOSFET, respectively. The front channel threshold voltages as well as the density of states at the back interface are presented.
Electrical Properties Optimization of Ba0.9Sr0.1TiO3 Thin Films Deposited by Sol-Gel
Authors: Fasquelle D. , Mascot M. , Carru J.C.
Published: July 2011

This paper reports a study of Ba0.9Sr0.1TiO3films deposited on Pt/Ti/SiO2/Si substrates. The annealing temperatures were 750°C, 850°C and 950°C. An increase of the average size of grains was observed, from 60 nm at 750°C to 110 nm at 950°C, as well as an increase of the dielectric constant, remnant polarization and tunability. When the annealing time was decreased from 1 hour to 15 min, the dielectric constant and remnant polarization values have been increased. The optimized annealing conditions (950°C for 15 min) give the following results: εr= 780 and tgδ = 0.01 at 100 kHz, Pr = 13 µC/cm², Ec = 63 kV/cm and a tunability of 55%.
Synthesis and Characterization of Novel Polyurethanes Based on N,N'-1,2-Ethanediylbis-(4-Hydroxy-Pentanamide) and 4-Hydroxy-N-(2-Hydroxyethyl)-Pentanamide
Authors: Chalid Mochamad
Published: July 2011

As diols, N,N'-1,2-ethanediylbis-(4-hydroxy-pentanamide) (1) and 4-hydroxy-N-(2-hydroxyethyl)-pentanamide (2)) are versatile precursors for the manufacture of bio-polymers. Polymer design, by exploiting the variation in structure of both diol and di-isocyanate monomers, such as backbone structure and presence of functional groups, appears to be a promising biopolymer engineering pathway to synthesize polyurethanes. Both diols (1) and (2) were then polymerized by reaction with aliphatic and aromatic di-isocyanates at 140 °C in (N,N-dimethylacetamide (DMA) solvents using triethylamine (TEA) catalysts, to obtain novel polyurethanes. The products were characterized by FTIR, 1H-NMR, 13C-NMR, and Elemental Analysis. This working has created a new chance to synthesis bio-polyurethanes based on levulinic acid, as one of biomass compounds
Determination of Copper Dissolution Activation Energy in Concentrated Hydrogen Peroxide
Authors: Sofyan Nofrijon I.
Published: July 2011

Determination of copper dissolution activation energy in concentrated hydrogen peroxide used as a decontaminant agent on aircraft has been carried out. This work was performed in conjunction with the determination of the effect of hydrogen peroxide used as a decontaminant agent on selected aircraft metallic materials. The main idea of this work was to simulate the worst possible condition, i.e. spillage of the liquid concentrate due to operator abuse or conditions where large-scale condensation of the peroxide takes place due to the failure of decontamination process control. Due to inherent properties of the chemical used as a decontaminant agent, it possibly could affect the airliner metallic materials during or after the decontamination process, particularly copper. Since copper is one of the important alloying elements in the aluminum alloys, this work was performed to get the idea how fast the process takes place and so to help understanding the subsequent corrosion process, if any, on the aircraft’s flightworthiness at least qualitatively and ideally quantitatively. The results showed that the rate of copper dissolution increased for the first 15 minutes of the reaction time with an activation energy of 19 kJ/mol, and then the fraction of copper dissolved became constant. This constant dissolution was expected to be due to the formation of copper hydroxide, which was observed to precipitate after the solution settled for some time. However, because the final consumption of hydrogen peroxide was not controlled, the exact reason for this constant dissolution cannot be determined at this time. The value of activation energy is within the range of activation energy found in the literature for other dissolution process. The low activation energy for dissolution of pure copper correlates with the observation of dissolution of copper from intermetallic particles in the aluminum alloys.
Neural Networks with Radial Basis Function and NARX Structure for Material Lifetime Assessment Application
Authors: Hidayat M.I.P. , Berata Wajan
Published: July 2011

In the present paper, neural networks (NN) with radial basis function and non-linear auto-regressive exogenous inputs (NARX) structure is introduced and first applied for predicting fatigue lives of composite materials. Fatigue life assessment of multivariable amplitude loading linked to the concept of constant life diagrams (CLD), the well known concept in fatigue of material analysis and design, was investigated. With this respect, fatigue life assessment using the RBFNN-NARX model was realized as one-step ahead prediction with respect to each stress level-S corresponding to stress ratio values-R arranged in such a way that transition took place from a fatigue region to another one in the CLD. As a result, composite materials lifetime assessment can be fashioned for a wide spectrum of loading in an efficient manner. In addition, the produced mean squared error (MSE) values of fatigue life prediction results of the RBFNN-NARX model competed favorably, even better, with those of the MLP-NARX model previously obtained. The simulation results for different multidirectional laminates of polymeric-based composites and loading situations were presented and discussed.
Development of Steel Wire Rope – Reinforced Aluminium Composite for Armour Material Using the Squeeze Casting Process
Authors: Rahmalina Dwi , Sofyan Bondan Tiara , Suharno Bambang , Siradj Eddy S.
Published: July 2011

Steel wire rope – reinforced aluminium composite - has been developed to improve the ballistic properties and mobility of armour material. Critical to obtaining ballistic resistance is that the materials must be sufficiently hard and strong, especially at the surface where a projectile will first make impact. To obtain this resistance, aluminium alloys can be strengthened by adding Cu and Mg. This research studied the ballistic properties of aluminium composites with varied Cu and Mg content. The matrix used in this study was an Al-7Si master alloy with 0.08-1.03 wt. % Mg and 0.05-3.75 wt. % Cu, both independently and in combination. A high carbon steel wire rope was used as strengthening material. The samples were produced through the squeeze casting process with a pressure of 1 MPa at semi-solid melting temperatures of 590-610 °C. The slab was then rolled for 10 % reduction to increase the hardness. Ballistic testing was performed in accordance with ASTM F1233 by using a 9 mm calibre projectile and 900 direction. Micro structural observation was conducted in the as-cast and ballistic samples, performed with optical microscope and scanning electron microscope (SEM). The results showed that squeeze casting may improve interfacial wettability and reduce void. The increase in Mg resulted in the decline of interfacial voids, but Cu addition tended to increase them. The aluminium armour was able to withstand a 9 mm calibre projectile, although some cracks were visible. The wire rope was not effective in stopping the penetration of a 7.62 mm calibre projectile.
The Effects of Plates Position in Vertical Casting Producing Thin Wall Ductile Iron
Authors: Suharno Bambang , Soedarsono Johny Wahyuadi , Soemardi Tresna Priyana , Sulamet-Ariobimo Rianti Dewi
Published: July 2011

In the general rule of casting design the thickest part of the cast should be placed near to the ingate. This arrangement was meant to guarantee the completion of filling process. An unusual vertical casting design to produce plates with different thicknesses was established based on the idea that the heat from molten metal will always warm up its entire runner. In this design the thinnest plate is placed near to the ingate. The design was made for producing thin wall ductile iron. This research was conducted to see the effects of reverse thickness arrangement in casting design to the microstructure and mechanical properties of the plates. Plates produced by this design were compared to plates produced by the same design with general casting arrangement. Thicknesses of the plates produced in this casting were 1, 2, 3, 4, and 5 mm. The moulds used were made from furan sand. Beside experiment, casting design simulation with Z-Cast was also conducted to ensure the completion of filling process and to see the manner of solidification. Casting simulation showed that arrangement of plates gave different filling and solidification manners. Although there were some differences, the filling was successful for both arrangements of plates. Skin effect was found in both designs. Nodule counts and nodularity were higher in the new design while average nodule diameters were lower. The result gained in tensile and hardness test did not follow the correlations in the characteristic of graphite. Mechanical properties showed that position of plate, ignoring the thickness, influence tensile strength and hardness.
Characterization of Residual Stresses in 718 Turbine Discs by Neutron Diffraction and Finite Element Modelling
Authors: Staron Peter , Cihak Ulrike , Clemens Helmut , Stockinger Martin , Schreyer Andreas
Published: July 2011

The results of our investigations on residual stresses in commercially produced forged IN 718 compressor discs are reviewed. The residual stresses in the discs with a diameter of 320 mm and a thickness of up to 25 mm were studied using neutron diffraction to verify the predictions of a finite element simulation, which was used to model forging and cooling of the discs. In addition to the disc, a thin plate of the same material was also studied for testing the influence of specimen geometry on the model predictions. While the model results for the disc were not strongly influenced by the heat transfer coefficient, the stress distributions in the thin plate could only be predicted satisfactorily by using a temperature-dependent heat transfer coefficient that was derived from temperature measurements during quenching. Eventually, this led to an improvement of the FE simulation used for optimizing the production process.
Cooling Rate Dependent Morphology of the γ' Precipitates in Nickel-Base Superalloy Udimet 500
Authors: Savadkoohi Mohammad Khalili , Samadi Ahad , Salehi Rasoul
Published: July 2011

The morphology of the γ΄ precipitates during continues cooling of a nickel-base superalloy, Udimet 500, was studied using scanning electron microscopy and X-ray diffraction technique. The samples were full solutioned at 1200oC and then were cooled to ambient temperature under different cooling rates, 15, 1, 0.2, 0.05oC/min and air cooling. The unconstrained γ-γ΄ misfit values for each sample were calculated using the electrolytic extracted γ΄ precipitates. According to the results, by decreasing the cooling rate, not only the size, volume fraction and interparticle spaces of the  precipitates were increased, but also depending on the γ-γ΄ lattice misfits the corresponding  morphology was changed from spherical to cubic, then ﬂower-like and finally dendritic shape. The observations are discussed in view of the compositional changes of γ/γ΄ phases and elastic strain considerations of their interfaces which will be described in detail in the article.
Decorrelated Dislocation Movement in the γ-Matrix Channels of a Ni-Based Superalloy: Experiment and Dislocation Dynamics Simulation
Authors: Pettinari-Sturmel Florence , Douin Joël , Locq Didier , Caron Pierre , Coujou Armand
Published: July 2011

The mechanical behavior of the polycrystalline NR3 Ni-based superalloy has been investigated at the microscopic scale. The elementary deformation mechanisms have been analyzed using transmission electron microscope observations as well as in situ straining experiments. Under low stress and relatively low strain rate conditions, a large variety of shearing micromechanisms has been observed depending on the local microstructure and the local effective stress. The influence of the smallest precipitates on the creep behavior has been enlightened: they induce narrow channels which act as obstacle for the movement of the dislocations. In the case of the narrowest channel, the deformation can operate by the propagation of Shockley dislocations or else, by the only propagation of the leading partial resulting from the partial dislocation decorrelation. The occurrence of the observed micromechanisms has been quantitatively analyzed using a nodal dislocation dynamics simulation.
The Effect of Lattice Misfit on Deformation Mechanisms at High Temperature
Authors: Grant Benedict M.B. , Knoche Elisabeth , Preuss Michael , da Fonseca Joao Quinta , Daymond Mark R.
Published: July 2011

Understanding the relationship between deformation mechanisms and microstructure is essential if one wants to fully exploit the potential of advanced nickel base superalloys and develop future alloys. In the present work, the influence of the lattice misfit between  and ’ has been studied by means of in-situ loading experiments using neutron diffraction in combination with crystal plasticity modelling on RR1000 and Alloy 720Li. Both alloys were processed to generate three simplified uni-modal γ’ microstructures to allow determination of γ’ responses and experiments were carried out at 750°C. The results showed that a positive misfit strain increases the level of load partitioning from  to ’ during plastic deformation introduced by uniaxial tensile loading.
On the Oxidation Resistance of Nickel-Based Superalloys
Authors: Sato Atsushi , Moverare Johan J. , Hasselqvist Magnus , Reed Roger C.
Published: July 2011

In this paper, the factors influencing the oxidation resistance of superalloys are studied. A model is proposed by which the Al2O3-forming properties of a given composition can be estimated, based upon the thermodynamic and kinetic factors influencing scale growth. The numerical modelling is tested by experimental work on a number of compositional variants of the newly-developed SCA425+ superalloy, which contains appreciable quantities of Cr. The modelling is shown to be in broad agreement with experiment. The effects of Al, Cr and Si on the oxidation resistance of this class of alloy have been rationalised.
Evolution of Raft Structure during Creep Deformation of the Ni-Based Single-Crystal Superalloy TMS-138
Authors: Tsuno Nobuyasu , Sato Akihiro , Tanaka Katsushi , Inui Haruyuki
Published: July 2011

The evolution of the raft structure in the Ni-based single-crystal superalloy TMS-138 crept at 1100 °C and 137 MPa has been investigated quantitatively by the Fourier analysis of scanning electron microscope (SEM) images. This method of analysis quantifies the extent of tilting of the γ/γ′ interface during creep deformation. The analysis is carried out on two different crystallographic planes, (100) and (110), on which SEM observations of deformation microstructures are made, to see if there is any difference in the results of analysis depending on observation planes. The tilt angle of the γ/γ′ interface, which is deduced by the Fourier analysis, increases with the accumulation of creep strain. The rate of the increase in the tilt angle is significantly large in the tertiary creep stage. The result of analysis does not depend significantly on crystallographic planes on which SEM observations of microstructures are made.
Numerical Modelling of Stress and Strain Evolution during Solidification of a Single Crystal Superalloy
Authors: Panwisawas Chinnapat , Gebelin Jean Christophe , Warnken Nils , Broomfield Robert W. , Reed Roger C.
Published: July 2011

During the manufacture of turbine blades from single crystal nickel-based superalloys by investment casting, recrystallisation can occur during solution heat treatment. The introduction of grain boundaries into a single crystal component is potentially detrimental to performance, and therefore manufacturing processes and/or component geometries should be chosen to prevent their occurrence. In this work, numerical models have been designed to enable a predictive capability for the factors influencing recrystallisation to be constructed. The root cause is plasticity on the microscale caused by differential thermal contraction of metal, mould and core; when the plastic deformation is sufficient, recrystallisation can take place subsequently. The models take various forms. First, one-dimensional models based upon static equilibrium have been produced – our calculations indicate that plastic strain is likely to take place in two temperature regimes: by creep between 1150°C and 1000°C and by tensile (time-independent) strain below 650°C. The idea of a strain-based criterion for recrystallisation is then proposed. Second, more sophisticated three-dimensional calculations based upon the finite element method are carried out. Our predictions are compared critically with experimental information.
Modelling Texturised Cast Structures in the Forging of Superalloys
Authors: Terhaar Jan , Blaes Nikolaus , Bokelmann Dieter , Schafstall Hendrik
Published: July 2011

The main objective of remelting processes commonly used in the production of super¬alloys is to obtain a columnar dendritic solidification structure throughout the whole ingot. Besides reduced microsegregation, this cast structure features a preferred orientation, which is depending on the primary dendrites’ growth direction and therefore closely related to the ingot’s pool shape. As a result, non-isotropic material behaviour can be observed during initial forging operations. Since the correct prediction of material flow is a prerequisite for the further analysis of forging processes by means of numerical simulation, the solidification texture’s influence on plastic flow was accounted for by the application of an anisotropic material model. The model according to Barlat was used to scale the flow stress with respect to the crystal orientations observed in the examination of vacuum arc remelted alloy 718, thereby considering the flow stress’ dependency on strain, strain rate and temperature. The parameters defining the material's anisotropy could be determined by the upsetting of cylindrical specimen from a remelted ingot.
Simulation of the External Pressure Influence on the Micro-Structural Evolution of a Single Crystal Ni-Based Superalloy
Authors: Lopez-Galilea Inmaculada , Huth Stephan , Fries Suzana Gomes , Steinbach Ingo , Theisen Werner
Published: July 2011

The phase field method has been applied to simulate the microstructural evolution of a commercial single crystal Ni-based superalloy during both, HIP and annealing treatments. The effects of applying high isostatic pressure on the microstructural evolution, which mainly retards the diffusion of the alloying elements causing the loss of the orientational coherency between the phases is demonstrated by the simulation and experimental results
Application of a Multiscale Constitutive Framework to Real Gas Turbine Components
Authors: Tinga T. , Brekelmans W.A.M. , Geers M.G.D.
Published: July 2011

A multiscale constitutive framework for Ni-base superalloys has been developed, in which an efficient unit cell is adopted to describe the γ/γ’ microstructure morphology. The framework enables the prediction of the deformation and the creep and fatigue damage accumulation in CMSX-4 for a range of temperatures and stress levels. Moreover, the material microstructural degradation due to rafting and isotropic coarsening can be simulated, and the effects of this degradation on the alloy mechanical response can be quantified. The present paper focuses on the application of the model to real gas turbine components. A high pressure turbine blade finite element model is used to demonstrate the computational efficiency of the multiscale framework. Moreover, the location of critical regions and the life time are shown to differ from the results obtained from classical models that neglect the microstructure evolution.
Microstructure and Properties of Nanostructured Alloy 718
Authors: Valitov Vener , Mukhtarov Shamil Kh. , Lutfullin Ramil Ya. , Safiullin Rinat V. , Mukhametrakhimov Minnaul
Published: July 2011

Nickel-iron Alloy 718 is widely used for fabricating parts by superplastic deformation. Refinement of grains down to a nanostructure (NS) size improves the alloy’s processing properties. Thermomechanical treatment has been carried out to form a NS state in bulk alloy by multiple isothermal forging (MIF) at gradually decreasing temperatures. Investigation of superplastic properties and processing behavior of Alloy 718 has been performed. The alloy with a grain size of 80 nm displays superplasticity (SP) at a temperature which is lower than for a conventional fine grained alloy by about 350°C. The values of the relative elongation  and the strain rate sensitivity coefficient m are 350% and 0.37, respectively. The experimental data on the influence of grain size on solid-state weldability in the range of SP have been obtained. The application of the effect of low temperature SP yields lower temperatures of superplastic forming (SPF) and pressure welding (PW) as compared with conventional SP of fine-grained material. The experiment of the combined process of SPF and PW by counter-forming of two polished sheets, demonstrates its low temperature processing feasibility using NS specimens. The SPF processing of NS sheets in a cylindrical die has been investigated. It has revealed that macro-deformation is uniform in cross and longitudinal sections. Mechanical properties of Alloy 718 in NS condition and after strengthening heat treatment have been discussed.
Thermal Stability of a Ni-Cr-W-Mo Alloy - Long-Term Exposures
Authors: Pike Lee M. , Srivastava S.K.
Published: July 2011

HAYNES® 230® alloy, based on the Ni-Cr-W-Mo system, is extensively used in gas turbines and other applications at high temperatures. It is recognized that the microstructure of many alloys under long-term service conditions can change. Microstructural changes may affect mechanical properties which in turn may determine component design life in service. Given the importance and widespread usage of 230 alloy, a number of studies on its thermal stability have been conducted. This study will focus on the effect of long-term thermal exposures at temperatures ranging from 649 to 871°C (1200 to 1600°F) on the microstructure and properties of 230 alloy. Room and elevated temperature tensile, and room temperature Charpy impact toughness properties of thermally exposed material are determined and correlated to observed changes in the microstructure. Microstructural analyses were performed using extraction/X-ray diffraction together with optical and scanning electron microscopy. The mode of fracture was ascertained by fractography of the thermally-exposed and broken test samples. The paper presents previously unpublished results for long-term exposures with durations ranging up to 50,000 hours (~ 6 years).
Creep Rupture Strength of Re and Ru Containing Experimental Nickel-Base Superalloys
Authors: Heckl Astrid , Rettig Ralf , Singer Robert F.
Published: July 2011

The influence of Re and Ru on creep rupture strength has been investigated using a new in-house designed alloy-series comprising 9 experimental nickel-base superalloys with stepwise increased Re and Ru additions. The presented creep data reveals a significant increase in creep rupture strength by additions of Re. For additions of Ru an increase of creep rupture strength can only be found for low Re contents. The present article, which is part of an extensive and systematic investigation on Re and Ru influences, shows, that an improved creep resistance by an influence of Re and Ru on the γ’-solvus temperature is rather improbable. Likewise, the influence of Re and Ru on liquidus temperature is not expected to play an important role. However, the creep rupture strength is suggested to be highly modified by γ/γ’-microstructure changes.
Influence of Gamma Prime Evolution on the Creep Behaviour of SX Nickel Base Superalloys
Authors: Maldini Maurizio , Lupinc Valentino , Angella Giuliano
Published: July 2011

The objective of this paper is to critically analyse the effect of the ’ morphology evolution on the creep strain rate behaviour in the temperature range 900 - 1100°C where rafts form in superalloys for single crystal turbine blade and vane applications. A close examination of the experimental results has shown different regimes of strain accumulation depending on the value of the applied stress and temperature. The experimental results have been rationalised in terms of the ’ shape evolution during creep.