bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Incipient Heat Damage on the Fatigue Properties of Aircraft Composites
Authors: Ong Rachel , Wang Chun H.
Published: March 2014

This paper presents a preliminary investigation into the effect of incipient heat damage on the mechanical properties of a carbon-epoxy composite. Specimens were exposed to a range of temperatures varying from 0°C to 280°C for one hour and then tested to quantify the effects of this high temperature exposure on the short-beam shear, Mode I and II interlaminar fracture toughness, and the Mode I fatigue properties. The results showed that as the exposure temperature increased, the short-beam shear suffered a reduction, whereas the Mode I and Mode II fracture toughness increased after an initial reduction. The fatigue disbond growth rates were largely un-affected under heat exposure below 280°C. This complex behaviour in the degradation in fracture toughness is likely due to the increased fibre bridging brought about by the reduction in matrix strength.
Influence of Secondary Ageing on Fatigue Crack Propagation of the AA7050 Aluminum Alloy
Authors: Jacumasso Sheila Cristina , Ribas Lima Luis Otavio , Martins Juliana Paula , Moreira Carvalho André Luis
Published: March 2014

The AA7050 aluminum alloy is widely used due to its low specific combined with high strength and toughness obtained from the heat treatment which involves solution treatment and ageing. It produces the mechanism of precipitation hardening of a thin phase and disperses. In this context, the present study to investigated three ageing treatments, their influence on fatigue crack growth. In order to find a better condition of precipitation of η' phase, which may increase resistance to fatigue crack growth of AA7050 aluminum alloy. The T614-65 condition was chosen as an alternative treatment in relation to T7451 and T6 conditions of current use in the industry. The fatigue crack growth rate results have shown that T614-65 fatigue strength were up to 14% higher than the shown for T7451 temper.
Notched Fatigue Behavior under Multiaxial Stress States
Authors: Gates Nicholas R. , Fatemi Ali , Socie Darrell F. , Phan Nam
Published: March 2014

Most engineering components and structures contain stress concentrations, such as notches. The state of stress at such concentrations is typically multiaxial due to the notch geometry, and/or multiaxiality of the loading. Significant portions of the fatigue life of notched members are usually spent in crack initiation (crack formation and microscopic growth) and macroscopic crack growth. Synergistic complexity of combined stress and stress concentration has been evaluated in a limited number of studies. Available experimental evidence suggests the current life estimation and fatigue damage analysis techniques commonly used may not be capable of accurate predictions for such complex and yet highly practical conditions. This paper investigates notched fatigue behavior under multiaxial loads using aluminum alloys. Many effects involved in such loading conditions are included. These include the effects of stress state (axial, torsion, combined axial-torsion), geometry condition (smooth versus notched), and damage evolution stage (nucleation and micro-crack growth versus long crack growth).
Experimental and Modeling Study of the Effect of Corrosion Pitting on Fatigue Failure Locations in Aircraft Components
Authors: Crawford Bruce R. , Loader Chris , Liu Qian Chu , Harrison Timothy J. , Sharp P. Khan , Härkegård Gunnar
Published: March 2014

It is well established that corrosion pits reduce the fatigue life and structural integrity of aluminum alloy aircraft components. A great deal of research has been conducted in this area in the last 20 years. This problem is not unique to aluminum alloys or aircraft however. Similar problems have been observed in the steel components of other engineered structures such as steel pipelines and steam turbine blades. However the effect of pitting corrosion on the probable location of fatigue failures has been overlooked. This is problematic as corrosion pits have caused fatigue failures in locations and components where they were unexpected, such as the trailing edge flap lug of the F/A 18 fighter aircraft. DSTO have called this problem ‘Corrosion Criticality’.
This paper reports the development of Monte-Carlo models of how pitting corrosion affects the location of fatigue failures in two fatigue specimen geometries that have different stress concentration factors (kt). These specimens are a low-kt fatigue life specimen and a high-kt fatigue life specimen with three holes arranged along its centerline. The modeling results for the low-kt specimen are then compared with experimental results for that specimen. The low-kt model produces good estimates of fatigue life and of the probability of fatigue failure at any given location in the specimen’s gauge section. The process that will be followed to develop the high-kt model is outlined.
The paper includes a discussion of using the Corrosion Criticality models to reduce the cost of corrosion maintenance by (i) identifying areas in which corrosion inspections are critical and (ii) identify aircraft components for which pitting corrosion will not be a threat to airworthiness during the life of an aircraft.
Offshore Pile Foundation Subjected to Lateral Cyclic Load in Layered Soil
Authors: Basack Sudip , Banerjee Abhik Kumar
Published: March 2014

The pile foundations supporting offshore structures are required to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition produces progressive degradation in the pile-soil interactive performance which is likely to introduce significant reduction in bearing capacity with increased settlement and displacements. This paper is based on a numerical model developed by the Authors to study the response of pile foundation under lateral cyclic load in layered soil. The model is validated with a field test data and thereafter, parametric studies have been carried out. A brief description of the works conducted and the major conclusions drawn are highlighted in this paper.
Fatigue Strength of Machined and Shot Peened Grey Cast Iron
Authors: Lundberg Mattias , Peng Ru Lin , Ahmad Maqsood , Bäckström Daniel , Vuoristo Taina , Johansson Sten
Published: March 2014

A common opinion is that cast iron, especially grey cast iron, is not as notch sensitive as steel and has therefore not been treated by shot peening to suppress crack initiation. For a heterogeneous material that also is brittle, just like grey cast iron, the shot peening parameters needed to induce beneficial surface residual stresses can be problematic to identify. Fatigue testing under uniaxial loading with an R value of -1, on mechanically polished and shot peened specimens, has been performed to determine the fatigue strength at 107 cycles as well as complete Wöhler-curves. Two different types of specimen geometries were tested, one smooth and one notched specimen having kt equal to 1.05 resp. 1.33. With large shots and high peening intensity (heavy SP) the fatigue strength clearly decreased whereas small shots and low peening intensity (gentle SP) might have lowered the fatigue strength. A short annealing at 285° after gentle shot peening increased the fatigue strength. The results are discussed and explained based on x-ray diffraction (XRD) measurements, i.e. residual stress and full width at half maximum profiles, as well as microstructural investigations using scanning electron microscope (SEM).
Fatigue Crack Closure due to Surface Roughness and Plastic Deformation
Authors: Walker Kevin , Wang Chun H. , Newman Junior Jim C.
Published: March 2014

Crack closure is an important factor affecting fatigue crack growth in high strength alloy materials. Plasticity is known to be the main driver of closure, but in some materials and at some stages other mechanisms such as fracture surface roughness and debris accumulation are also important. Analytical models based on the plasticity induced closure concept have been very successful in correlating fatigue crack growth rates and lives for a range of materials under constant amplitude and spectrum loading. However, extreme values of plastic constraint factors, significantly lower than those determined from three dimensional finite element studies on similar geometry, are needed to achieve good correlation with experimental results, particularly for materials which exhibit rough and tortuous fatigue surfaces. One such material investigated here is β-annealed Ti-6Al-4V titanium alloy. The aim of this paper is to further develop, apply and evaluate a crack closure model which combines roughness and plasticity induced closure, incorporating experimental measurements of fracture surface roughness from tests on Eccentrically Loaded Single Edge-Notch Tension (ESE(T)) specimens. The model was first proposed by Zhang et al. 2002 for short cracks in 2000 series Aluminium Alloy. The model was evaluated here for physically longer cracks in the Titanium Alloy material. Accurate surface profile and roughness measurements were made using an optical 3-D profiler with a vertical resolution of better than 0.15 μm. Verification of the proposed model was carried out by comparing the model prediction with the closure measurements by back-face strain compliance using the pin-loaded ESE(T) specimens. Results from the roughness model were then compared with results from the FASTRAN analytical crack closure code. Analysis using this new approach, with plastic constraint factors more closely aligned with the values determined from independent classical and three dimensional finite element studies, provide a solid basis from which to implement the approach in FASTRAN.
On Thermo-Hydro-Mechanical (THM) Fatigue Damage of Historical Stone Buildings
Authors: Hoxha Dashnor , Belayachi Naima , Do Duc Phi
Published: March 2014

The efficient conservation, restoration and protection of stone historical buildings could not be dissociated from the researches of mechanism of stone decays. While various mechanisms of stone degradations are considered and studied in previous studies, in this paper is focused on the cumulative damage modeling of wall stones due to the fatigue induced from quotidian fluctuations of thermal and hydric conditions. The thermoporomechanics theory of partially saturated media is used to describe the behavior of stone wall and its interaction with climatic conditions. Further, the effective stress concept firstly introduced by Terzaghi is extended for partially saturated media providing a quite powerful tool for design and analysis [. The behavior of a typical stone wall from Chambord castle (Center region of France) is then simulated, taking into account the heterogeneity of the stone-mortar contacts. The climatic conditions are introduced in the model as boundary conditions. The records of temperature and humidity from meteorological stations close to castle are used to establish time-variation of condition with a time resolution of 6 hours. From performed numerical analyses, it is shown that variation of temperature and relative humidity leads to the variation and fluctuation of effective stress in the stone, more intensively on the outdoor. The contact of stone with mortar is a natural stress concentration center, but even there the stress is much lower than tensile strength of the white tuffeau stone. The fatigue of the stone due to the stress fluctuation induced by the variations of meteorological conditions seems to be a major factor of stone degradation. A model is used to assess the cumulative damage of the stone wall as a function of the time.
J-Integral Approach to Creep-Fatigue Crack Propagation in Lead-Free Solder under Various Loading Waveforms
Authors: Tanaka Keisuke , Fujii Takashi , Fujiyama Kazunari
Published: March 2014

Crack propagation tests of lead-free solder were conducted at room temperature in air using center-notched plates under load-controlled conditions with three waveforms: triangular pp waveform having fast loading and unloading rates, cp-h waveform having a hold time under tension, and cc-h waveform having a hold time under tension and compression. The J integral was evaluated from load-displacement curves. For fatigue loading of pp waveform, the crack propagation rate was expressed as a power function of the fatigue J-integral range. The creep component due to the hold time greatly accelerated the crack propagation rate. The creep crack propagation rate was found to be a power function of the creep J integral range for each case of cp-h and cc-h waveforms. The creep crack propagation rate for cp-h waveform was higher than that for cc-h waveform. Displacement-controlled tests were also performed under four triangular strain waveforms: pp, cp, cc and pc. For the case of pp waveform, the crack propagation rate was also expressed as the same power function of the fatigue J integral range as in the case of load-controlled tests. The creep crack propagation rate was expressed as a power function of the creep J integral range for each case of cp, pc and cc waveforms. Microscopic observations were conducted to clarify micromechanisms of creep-fatigue crack propagation.
Fatigue Behaviour of AZ91 Magnesium Alloy in as-Cast and Severe Plastic Deformed Conditions
Authors: Kunz Ludvík , Fintová Stanislava
Published: March 2014

Fatigue strength, crack initiation and microstructure were experimentally investigated in an as-cast AZ91 alloy and in ultrafine-grained (UFG) AZ91 alloy processed by equal channel angular pressing (ECAP). The microstructure after ECAP is bimodal, consisting of fine-grained regions and clusters of larger grains with lower density of intermetallic particles. It has been found that the ECAP substantially increases the tensile strength (factor of two), improves ductility (factor of five) and improves the fatigue strength in low-cycle fatigue region. The improvement of the endurance limit based on 107 cycles is weak. The cyclic slip bands, as sites of the fatigue crack initiation on material surface, were investigated. Focussed ion beam technique (FIB) was applied to reveal the surface relief and the microstructure in the vicinity of early fatigue cracks. No grain coarsening was observed in the close vicinity of the initiated cracks. Fatigue cracks in ultrafine-grained structure develop both in the regions of larger grains and also in the fine grained areas. Two types of crack initiation were observed.
Effect of Thermal Cycling on the Mechanical Properties of a Continuous Fibre Composite Used for Car Clutch Facings
Authors: Flament Camille , Salvia Michelle , Berthel Bruno , Crosland Gerard
Published: March 2014

In dry clutch systems, the clutch facing is an annular shaped continuous fibre composite with organic matrix (thermo set resins) which transmits the torque from the engine to the wheels. In use it is submitted to thermo-mechanical cycling. Due to the composite fibre organisation, the strain field under thermo-mechanical loading is not homogenous. Full field data is needed to describe the material behaviour. Digital Image Stereo-Correlation (DISC) was used to determine the coefficient of thermal expansion (CTE) of the material. To determine the effect of temperature and cyclic loading on the mechanical properties, the composite was subjected to different thermal cycles. The material properties are modified with increasing temperature and number of cycles. These results were confirmed by dynamic mechanical analysis which showed thermal ageing of the resin. The local information given by the strain fields revealed a non uniform evolution of the material properties with thermal cycling.
Cyclic Slip Localization and Crack Initiation in Crystalline Materials
Authors: Polák Jaroslav , Man Jiří
Published: March 2014

Cyclic plastic straining in crystalline materials is localized to persistent slip bands (PSBs) and results in formation of persistent slip markings (PSMs) consisting of extrusions and intrusions. Intensive plastic strain in PSBs results in dislocation interactions and formation of point defects. The extended model based on point defect formation, migration and annihilation is presented describing surface relief formation in the form of extrusion-intrusion pairs. Point defect migration and resulting mass transfer is the principle source of cyclic slip irreversibility leading to crack-like defects - intrusions. Fatigue cracks start in the tip of sharp intrusions.
Cyclic Deformation Response of Polycrystalline OFHC Copper under Pure Compression Fatigue
Authors: Hsu Tzu Yin Jean , Wang Zhi Rui
Published: March 2014

Systematic experimental investigation was carried out to examine the cyclic deformation response and study the crack nucleation mechanisms under pure compression fatigue condition using OFHC Cu. Results show that the cyclic stress strain response and micro-structural evolution of copper under pure compression fatigue exhibits rather dissimilar responses compared to those under general push-pull fatigue conditions. Both rapid hardening and the compressive cyclic creep were observed in all tested conditions. Like under all fatigue conditions, surface micro-structural changes were detected by optical, SEM, and specifically AFM. It was revealed that cyclic plastic strain accommodated by the sample was not in any major way through dislocation activities, as there was only moderate slip activities observed on the surface and no PSB features were detected from TEM observations. Instead, cyclic creep was observed to be the major form of plastic strain accommodation. In addition, the observed surface phenomenon was found to have led to the eventual crack nucleation when the applied stress amplitude was high.
AFM and FIB Study of Cyclic Strain Localization and Surface Relief Evolution in Fatigued f.c.c. Polycrystals
Authors: Man Jiří , Valtr Miroslav , Kuběna Ivo , Petrenec Martin , Obrtlík Karel , Polák Jaroslav
Published: March 2014

Atomic force microscopy (AFM) and focused ion beam technique (FIB) were adopted to study the early stages of surface relief evolution in 316L steel and polycrystalline copper fatigued with constant plastic strain amplitudes at different temperatures (316L steel at 93, 173 and 573 K; copper at 83, 173 and 295 K). Qualitative and quantitative data on the morphology and shape of persistent slip markings (PSMs), occurrence of extrusions and intrusions and the kinetics of extrusion growth are reported. They are discussed in relation with recent physically based theories of surface relief formation leading to fatigue crack initiation.
Failure Analysis to Blades of Steam Turbines at Normal Conditions of Operations and Resonance
Authors: Tejeda A.L. , Rodríguez J.A. , Rodríguez J.M. , Garcia J.C. , Basurto-Pensado M.A.
Published: March 2014

The need to provide quality services, accurate diagnosis, timely rehabilitation and improvement in materials and operation of the turbines, have given way to scientific research crack initiation and crack propagation, the impending fracture and estimating life of the turbine components at normal conditions and resonance. The L-1 stage blades suffer high alternating stresses, for its size, exposure to high temperatures, and mechanical loads under repetitive strain of cyclic load. The lasts stages of blades are also subjected to severe centrifugal loads stress that, when combined with the alternating stress, is responsible for fatigue failures. In this work, the last stage L-1 blades of a steam turbine under cyclic load or fatigue were analyzed, the first instance to observe and measure the initiation crack and propagation crack under normal conditions operation and conditions on resonance; making the comparison to estimate the life time of the blade at both conditions.
Fatigue Crack Propagation Limit Curves for High Strength Steels and their Application for Engineering Critical Assessment Calculations
Authors: Lukács János , Gáspár Marcell
Published: March 2014

There are different prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth. The research work aimed (i) to determine fatigue crack propagation limit curves for high strength steels and their welded joints, based on the Paris-Erdogan law; (ii) to use the determined limit curves for engineering critical assessment (ECA) calculations. Experiments were performed on different high strength steels and their welded joints; and the propagating cracks in the specimens represent the different possible locations of the real cracks in the structural elements. Fatigue crack growth tests were executed by ΔK-decreasing and constant load amplitude methods. The evaluation process consists of six steps, and by means of the selected values a statistical method can be proposed for determination of the limit curves. Engineering critical assessment calculations were performed on a welded structural element having crack like defects.
Thermal Cycling Fatigue of Thermal Barrier Coatings - Rig and Experiment Design
Authors: Eriksson Robert , Brodin Hakan , Johansson Sten , Östergren Lars , Li Xin Hai
Published: March 2014

Ceramic thermal barrier coatings are used for thermal insulation in gas turbines to protect metallic components from high-temperature degradation. The ceramic coating may, due to its different coefficient of thermal expansion, crack and spall off the metallic component, thus rendering the component unprotected against high-temperature. Thermal cycling rigs of various designs are used to evaluate the durability of thermal barrier coatings. The present paper reports the result from a round robin test including three thermal cycling rigs at different locations. To better understand the influence of rig design on the thermal cyclic lives of thermal barrier coatings, some test parameters, such as the material of the specimen table and the cooling rate, were varied in one of the rigs. Furthermore, two different specimen geometries, rectangular and disc-shaped, were tested. The specimen table material was found to greatly influence the cooling rate of the specimens, more so than variations in the cooling airflow. The rectangular specimens were found to be more sensitive to test setup than the disc-shaped specimens; under certain conditions, the rectangular specimens could be made to fracture from the long side, rather than the short side of the specimen edge, which shortened the thermal cyclic life of the coatings.
Improvement of Fatigue Properties in a Cast Aluminum Alloy by Roller Burnishing and Friction Stir Processing
Authors: Nakamura Yuki , Nakajima Masaki , Masuda Hiroaki , Kakiuchi Toshifumi , Uematsu Yoshihiko
Published: March 2014

Roller burnishing (RB) and friction stir processing (FSP) were applied to a cast aluminum alloy, AC4CH-T6 (equivalent to A356-T6), to improve the fatigue properties. In roller burnished specimens, Vickers hardness was increased until the depth of 60μm compared with that of the as-cast specimens, resulting in work-hardening by RB. The compressive residual stress on the surface of the roller burnished specimens was also increased from 35MPa to 132MPa. In order to investigate the effect of RB on the fatigue properties, rotary bending fatigue tests have been performed using the roller burnished and the as-cast specimens. The roller burnished specimens exhibited higher fatigue strength than the untreated specimens. It is due to the increase in hardness and compressive residual stress by RB. In addition, plane bending fatigue tests have been performed using the friction stir processed and untreated specimens. Fatigue strengths of the friction stir processed specimens were highly improved compared with untreated specimens as the results of the elimination of casting defects by FSP. However, the crack growth rates of the friction stir processed specimens were faster than those of untreated specimens. It is due to the softening of the material by heat input during the FSP.
F-35 Full Scale Durability Modeling and Test
Authors: Ball Dale L. , Gross Philip C. , Burt Robert J.
Published: March 2014

The F-35 Joint Strike Fighter program includes three aircraft variants, one of which has been designed and built according to US Air Force requirements, and the other two of which have been designed and built according to US Navy requirements. For all three variants, a system design and development (SDD) configuration aircraft is being subjected to a full-scale durability (FSD) test. In each case, the complete airframe is being subjected to two lifetimes of severe design spectrum loading, with maneuver, catapults/arrestments (carrier variant only) and buffet loads applied as separate, alternating 1000 flight hour blocks during the major test sequence. For the airframe tests, the buffet loads are applied quasi-statically; for the separate vertical tail component tests, they are applied dynamically. In addition, tests of doors and attachments (local tests) are conducted when the full airframe test is down for inspections (as required, for example, between the first and second lifetimes). In this paper, we describe the manner in which the airframe tests were designed, including fatigue spectrum development and test adequacy analyses. In addition, we provide a summary of the test findings to date, along with a description of the analytical simulation for a typical finding. The paper includes an analysis vs test correlation summary that provides an indication of the validity of the fatigue crack initiation (FCI) and fatigue crack growth (FCG) analysis methods used to design the aircraft.
Development of CGAP for Fatigue Damage and Crack Growth Analysis: Verification, Validation and Examples of Application
Authors: Wallbrink Chris , Hu Wei Ping
Published: March 2014

A computer program for fatigue life and crack growth analysis, entitled CGAP, has been developed at the Defence Science and Technology Organisation in support of the aircraft structural life assessment programs of the Australian Defence Force. The key objectives in developing this software platform were to provide a flexible, robust, economical, adaptable, and well verified and validated fatigue analysis tool. CGAP provides advanced capabilities for crack growth analyses, including crack growth in notch-affected plastic zones, and for probabilistic crack growth analyses. It also provides seamless interface to third-party models, such as FASTRAN and FAMS, enabling easy benchmarking against and collaborating with international partners. This paper summarises some of the recent developments in analytical and numerical fatigue damage and crack growth modelling, with emphasis on software verification and validation. Examples will be presented to illustrate its application.
Experimental Study on the Multistage Strength Degradation and the Associated Strain Energy Variation of S25C
Authors: Shi Zi Hai , Nakano Masaaki , Liu Cui Ping
Published: March 2014

The multistage strength degradation theory, which has recently emerged from studies on the material and structural behaviour of concrete, provides a clear description of the mechanism of fatigue. According to this theory, fatigue is caused by the sporadic sudden change of cracking behaviour in a system under cyclic loading, leading to intermittent strength reduction of the system and its eventual failure. As metal is the main engineering material plagued most by fatigue failure, this newly-established theory needs to be experimentally verified on metal, which is the aim of this study. The obtained test results present strong experimental evidence for the existence of multistage strength degradation processes in metals under cyclic loading, and the strength degradation is clearly triggered by the abrupt change of cracking behaviour. These tests confirm the relevance of the multistage strength degradation theory on metal fatigue, and the engineering implications of the study are discussed.
A Probabilistic Two-Scale Approach to Predict the High Cycle Fatigue Behaviour of Ti-Al6-V4 Parts Machined by High Pressure Water Jet Assisted Turning
Authors: Mella Pierre , Billardon René , Desmorat Rodrigue
Published: March 2014

The high cycle fatigue life of machined parts is affected by the so-called surface integrity induced by the machining process. To model the high cycle fatigue behaviour of turned parts a probabilistic two-scale continuum damage model is developed. While the macroscopic behaviour of the material is assumed to remain elastic during the fatigue loading, the fatigue prediction is based on the incremental evolution of micro-plasticity and damage. The non-standard initial mechanical state of the material in the sub-surface, viz. the plastic strains and residual stresses fields induced by the machining process are taken into account via an initial step prior to the fatigue loading. As far as the micro-geometry of the surface is concerned, an initial micro-crack distribution depending on the depth and shape of the micro-defects observed is introduced.
The Influence of Corrosion Pits and Cold Expanded Fastener Holes on the Fatigue Life Aluminium 7075-T651
Authors: Withy Benjamin , Campbell Stephen , Stephen Glenn
Published: March 2014

The Royal New Zealand Air Force (RNZAF) utilised the split sleeve cold expansion process to increase the fatigue life of fastener holes in the wings of the C130 transport fleet. As part of the validation of the fatigue improvements offered by the process the Defence Technology Agency conducted a series of fatigue tests on cold expanded fastener holes in aluminium 7075-T651, including specimens with corrosion induced after the cold expansion process had been performed. This research conducted an analysis of fatigue crack origins and modelled the stress concentration factors generated as a result of the corrosion pits. These results were used to explain the differing fatigue life and s-n curves produced by corroded and non-corroded fatigue specimens and the location of crack initiation sites around corroded cold expanded fastener holes.
Nanostructure and Fatigue Behavior of β-Type Titanium Alloy Subjected to High-Pressure Torsion after Aging Treatment
Authors: Yilmazer Hakan , Niinomi Mitsuo , Cho Ken , Nakai Masaaki , Hieda Junko , Todaka Yoshikazu
Published: March 2014

A novel β-type, Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ has been developed for biomedical applications. Its fatigue strength is one of the most important mechanical biocompatibilities of TNTZ because, in surgical applications, it will be used under cyclic loading conditions. The effect of the microstructural refinement by high-pressure torsion (HPT) on the fatigue behaviour of TNTZ is systematically investigated in this study. TNTZ subjected to HPT processing where the rotation number (N) is 20 (TNTZAHPT) after aging treatment (AT) shows a unique microstructure having ultrafine elongated grains (285 nm in length and 36 nm in width) with high-density dislocations, a large fraction of blurred and wavy boundaries consisting of non-uniform subgrains with high misorientation and nanostructured precipitated α phase. Remarkably, a good combination of high mechanical strength (1375 MPa) and low Young’s modulus (87 GPa), compared to that of Ti-6Al-4V (Ti64) ELI, is achieved for TNTZAHPT at N = 20. TNTZAHPT a great fatigue strength, which is comparable to those of (Ti64) ELI.
Calculating the Resistance of a Grain Boundary against Fatigue Crack Growth
Authors: Knorr Alain Franz , Marx Michael
Published: March 2014

One problem of the quantitative description of small fatigue crack propagation is the fluctuating crack growth rate induced by obstacles like grain or phase boundaries. Sometimes cracks stop completely for a large number of cycles sometimes cracks only decelerate, both resulting in an additional number of life time cycles. However, so far it is not clear, what actually determines the resistance of a grain boundary against fatigue cracks. Therefore we investigate small crack propagation through grain boundaries systematically by in-situ imaging in the scanning electron microscope and focused ion beam (FIB) crack initiation. By this unique technique, artificial stage I cracks with constant crack parameters can be observed while interacting with different grain boundaries which gives detailed information on the interaction mechanisms. We identified different useful aspects of the interaction between microcracks and microstructural barriers on the microscopic scale. 3D-tomographs revealed by serial sectioning and FIB give information about the transition process from the initial grain to the neighbouring one. The resulting purely geometrical consideration leads to a quantitative description of the blocking effect of grain boundaries and can be used to calculate the probability of a crack transfer from the orientation data of two neighboring grains only.
Improvement in Fatigue Strength of Friction Stir Welded Aluminum Alloy Plates by Laser Peening
Authors: Sano Yuji , Masaki Kiyotaka , Hirota Keiichi
Published: March 2014

Plane bending fatigue testing was performed to study the fatigue properties of friction stir welded (FSW) 3 mm thick AA6061-T6 aluminum alloy plates. Fatigue cracks propagated with bends and curves on the specimens, showing large deviation from a linear line. This might be reflecting the material flow and microstructure in the weld zone. The fatigue strength of the unwelded base material (BM) was 110 MPa at 107 cycles and FSW deteriorated it to 90 MPa. However, laser peening (LP) restored the degraded fatigue strength up to 120 MPa which is higher than that of the BM.
Fatigue Crack Retardation in LSP and Sp Treated Aluminium Specimens
Authors: Hombergsmeier Elke , Holzinger Vitus , Heckenberger Ulrike C.
Published: March 2014

Highly loaded aircraft components have to fulfill strict fatigue and damage tolerance requirements. For some components besides the crack initiation mainly the fatigue crack propagation behavior is the main design criteria. To improve the crack propagation behavior of a component several methods are known or have been described in literature. For thin aircraft panels i.e. the application of crenellations [1] or bonded doublers [2, 3] can be a solution. For thick structures mainly the introduction of compressive residual stresses is beneficial.

In this paper the potential of compressive residual stresses obtained by Laser Shock Peening (LSP) and Shot Peening (SP) is investigated. By means of Laser Shock Peening the residual compressive stress field can extend much deeper below the treated surface than that produced by conventional Shot Peening (i.e. with steel or ceramic balls) [4, 5]. The effect of such deep compressive stress profile results in a significantly higher benefit in fatigue behavior after Laser Shock Peening or after the combination of Laser Shock Peening and Shot Peening on top. The measurement of residual stresses as a depth profile has been performed by incremental hole drilling (ICHD) and contour method. Finally crack propagation tests have been carried out to validate the process technology approach.
Preparation of Magnetic Iron Oxide by Hydrothermal Method
Authors: Zhao Fu Yan , Li Ya Ling , Lv Chao , Li Lu Hai
Published: March 2014

Abstract. Iron oxide particles with spherical, date-pit like, or polyhedron morphology were obtained by hydrothermal method. The morphology, thermal analysis, crystal structure of the products was characterized by FESEM, thermogravimetry (TG), X-ray diffraction (XRD), respectively. The measured results reveal that the product of three different shapes is hematite (α-Fe2O3).
Nanosurface Modifacation of Biomedical β Titanium Alloy for Dental Implant and its Antibacterial Property
Authors: Qi Yu Min , Ma Bai Hui , Geng Yue Jiao , Deng Jia Yin , Cui Chun Xiang
Published: March 2014

The TiO2 nanotube array film was synthesized on the surface of Ti-Nb-Zr-Mo βTitanium alloy via anodic oxidation in single electrolytic solution only containing HF. The diameter of TiO2 nanotubes was 30-50nm, and the length was 240nm. Compared with the processing parameters (including anodizing voltage, reaction time, concentration and kinds of electrolytic solution) used for pure Titanium or Ti-6Al-4V alloy, the parameters was further optimized. The surface morphology and element compositions Ti-Nb-Zr-Mo alloy before and after anodic oxidation were observed and analyzed by a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX) spectrometer. The antibacterial property of TiO2 nanotube array film prepared with optimal conditions was evaluated by coculture in vitro between Actinomyces viscosus and materials tested. The results indicated that the TiO2 nanotube array film had very good antibacterial activity to resist Actinomyces viscosus. TiO2 nanotube array film/Ti-Nb-Zr-Mo βTi alloy biocomposite will be an more excellent dental implant owning good biomechanical adaptability, biocompatibility and antibacterial property.
Polypyrrole/Graphene Oxide Composite Electrodes for High Energy Density Supercapacitor
Authors: Yang Zhe Wei , Fan Xin , Guo Li Ang , Jiang Wang Xing
Published: March 2014

Polypyrrole/Graphene oxide composite material (PPy/GO) was synthesized using an in-situ chemical polymerization method. The formation of composite had been shown by the analysis of Fourier transfer of infrared spectroscopy and X-ray diffraction data. Scanning electron and transmission electron microscopy clearly showed sheet-like layered structure of graphite oxide surrounded by polypyrrole. Electrochemical properties were characterized by electrochemical station. We demonstrated the intercalation of conducting polypyrrole into the graphite sheets, and that as electrodes for supercapacitor, the PPy/GO composites (GO0.54) with PPy to GO mass ratio of 5:3 showed a competitive capacitance of 337 F g-1 at a scan rate of 2 mV s-1 than that of PPy alone. Given the electrical and electrochemical properties, we prospect that the PPy/GO composites should find applications in supercapacitors.
Effect of Binder on Wear Behavior of HVOF WC-Based Coatings
Authors: Yao Shun Hui
Published: March 2014

This study aimed to understand the effect of a binder on the wear performance of HVOF WC-based coatings. Three kinds of commercial feedstock powders were studied, i.e. WC-12Co, WC-10Co4Cr and WC-10Ni. Characterization was conducted using SEM, micro Vickers hardness test and XRD. It was found the WC-10Co4Cr coating showed the highest hardness, while the WC-10Ni coating the lowest. The WC-10Co4Cr coating showed very good wear resistance as compared with the widely used WC-12Co coating.
Well-Defined Blackberry-Like Polypyrrole Microspheres via Chemical Oxidative Polymerization in the Presence of Functional Floating Bead as In Situ Dopant
Authors: Lao Jia Ping , Yang Chao , Mo Hao Dao , Li Yu Ping , Zang Li Min , Liu Liang Qin
Published: March 2014

Functional floating bead (F-FB), prepared by anchoring the organic sulfonic acid on the surface of the blackberry-like structural FB, was used as both the inorganic substrate and the in situ dopant for the in situ chemical oxidative polymerization of pyrrole to obtain the plypyrrole/functional floating bead (PPy/F-FB) nanocomposite material. The composites possess high electrical conductivity at room temperature. Thermogravimetric analysis shows that the thermal stability of PPy/F-FB composites was enhanced and these can be attributed to the retardation effect of sulfonic acid-functionalized FB as barriers for the degradation of PPy. The morphology of PPy/FB composites showed the well-defined blackberry-like morphology.
A Comparative Study on the Fire Resistance of Ordinary Grade Structural Steels
Authors: Kwon In Kyu
Published: March 2014

Fire resistance of structural elements such as columns and beams has been evaluated by the fire test. However, needs of fire design based on analysis using a heat transfer theory and a stress analysis are increasing because the design can reduce not only the period of the fire test but the cost of it. The reliability of the analysis would be totally dependent on the mechanical, thermal databases of their structural steels. This paper evaluates the fire resistance of ordinary grade structural steels manufactured from Korea by examining the mechanical and thermal properties of SS 400, SM 400, and SM 490 at high temperature and comparing them with those defined in Eurocode 3. The results showed that the ordinary structural steel had almost the same characteristics as those in Eurocode 3.
Influence of SiH4 Flow Rate on GaN Films with In Situ SiNx Mask on Sapphire Surface
Authors: Li Zhong Hui , Peng Da Qing , Luo Wei Ke , Li Liang , Zhong Dong Guo
Published: March 2014

Sapphire substrate was treated by SiH4 under NH3 atmosphere before GaN growth and nanosize islands SiNx mask was formed on the substrate. Properties of GaN films were investigated by high resolution X-ray diffraction, photoluminescence and transmission electron microscopy. The results indicated that the SiH4 flow rate is an important factor affecting the size and density of SiNx mask besides SiH4 treatment time.The GaN films grown on the SiNx-patterned sapphire substrate revealed an epitaxial lateral overgrowth mode, which affected 3D to 2D growth time and the microstructures of GaN films. The lowest FWHM value of (102) rocking curve was 286 arcsec. as the SiH4 flow rate of 0.5sccm, with the calcultated edge-type dislocations density of 4.28×109cm-2.
Investigation on Finite Element Simulation of ECAE with Variable Back Pressure for 7075 Aluminum Alloy
Authors: Tan Xian Feng , Yu Cheng Long , Xie Bao Hua
Published: March 2014

The numerical simulation of equal channel angular extrusion (ECAE) with variable back pressure was researched by applying the commercial Deform-3D software, in which choosing the hard deformation materials of 7075 aluminum alloy, and comparing the traditional ECAE without back pressure process. The influence of back pressure on the mean stress and the effective strain rate in the shear deformation zone was studied. The results show that the extrusion force transformation laws were different in both load ways, with the increase of back pressure, extrusion force enhances increasingly, but the final load-time curves tended towards stability, but in ECAE without back pressure, the final load-time curves tended towards decreasing; thus the whole deformation process can be divided into different stages. In addition, the larger the absolute value of the hydrostatic stress at the corner, the more beneficial to refine grain and improve the plasticity. The back pressure makes the distribution of effective strain rate in plastic deformation area more uniform and improves the uniformity of deformation.
Application of Tracked Combine Harvester Step-Less Speed Regulated System
Authors: Lou Xi Yin
Published: March 2014

In this paper, Step-less speed regulation system using double reversible variable pump and double quantitative motor, since the middle of no other control valve, the hydraulic pump and hydraulic motor with high efficiency. To meet the tracked combine and walking machines because of their own characteristics has the advantages of compact structure, light weight, high efficiency, high reliability, and other requirements of the system..
Torsional Vibration of a Pile Embedded in Saturated Soil Considering Pile Construction Effect
Authors: Zhang Zhi Qing , Qin Rui Fu
Published: March 2014

The torsional vibration of an elastic supporting pile embedded in a radially inhomogeneous saturated soil due to construction disturbance is investigated. At first, the composite soil layer is divided into outer semi-infinite undisturbed and inner annular disturbed zones, and the inner disturbed zone is subdivided into N thin concentric annular sub-layers. Then, the complex impedance at the top end of the pile is derived by substituting the available analytical expression for the shear rigidity of the composite soil layer into the governing equation of the pile. Finally, selected numerical results are obtained to analyze the influence of the radial inhomogeneity of the surrounding soil on the torsional vibration characteristics of the pile.
Study on the Permeability Characteristics of Coarse-Grained Soil and its Permeability Rule
Authors: Li Wen Bo
Published: March 2014

The permeability of coarse-grained soil is influenced by many factors. The results of permeability tests in different conditions indicate the effects of coarse-grained soil dry density of , fines content P5,void ratio e and nonuniform coefficient Cu to the permeability coefficient. Analyzing the relationship between coarse-grained soil dry density , fines content P5, void ratio e, nonuniform coefficient Cu and permeability coefficient, thus there is a relational expression between coarse-grained soil dry density of soil , fines content P5, void ratio e, nonuniform coefficient Cu and permeability coefficient.
Study on the Anti-Seepage Reinforcement Scheme of Earth-Rock Dam for Changli Reservoir
Authors: Chai Xian Dun , Shen Zhen Zhong , Nie Bai Song
Published: March 2014

Seepage failure is an important factor in causing dam-break of earth-rock dam, so the study of anti-seepage reinforcement for dilapidated reservoirs is always an important topic to earth-rock dam. Changli reservoir, since the completion, soil flow and failure by piping occur in dam slopes, the safety of downstream residents has been threatened both in life and property. Based on the comparisons of the effects of anti-seepage reinforcement schemes,the result shows that, for this clay dam, concrete cut-off wall can improve the seepage state obviously and has a higher operational stability. Thus, the concrete cut-off wall is designated as the recommended anti-seepage scheme for Changli reservoir.
The Digital Design of Engine Connecting Rod Based on the CATIA
Authors: Zhang Kai Xing , Liu Xian Xi , Wang Yu Liang
Published: March 2014

Since it is too complex to make the engine connecting rod design digital and too amount of work to make mistakes, a method based on the CATIA to achieve the engine connecting rod digital design is proposed. Firstly, the parameterized modeling of connecting rod is completed based on secondary development of CATIA. And then, the finite element analysis is applied to the model. Finally, the analysis results verify the effectiveness of the proposed method.
The Design and Application of the Platen Roller Pressure Regulating Device of PROTOS1-8 Cigarette Machine
Authors: Zhang Xiao Hang , Liao Yan Pei , Lai Da Bing , Zhang Yi Lan
Published: March 2014

If the wear and the replace frequency of rubber platen rollers of PROTOS1-8 Cigarette Machine can be reduce, easily lead to the stable of the force of paper feed and reducing the time of maintenance and spare parts consumption. However, there is no a new device for adjusting pressure of platen rollers. To solve this problem, a new type of device for adjusting pressure of platen rollers is designed. The three movable reference wheels used to test and adjust the gap instead of the reference plane. Application results shows that using the new device can effectively solve the excessive wear of the rubber platen roller. The amount of rubber rollers for replacing is reduced to 6 compare of 22 before and the maintenance time is reduced to 19 hours compare of 115 hours before during the statistical time. It also improve the operating efficiency of this type of equipment.