bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Crack Growth Rate in Laser-Welded Web Core Sandwich Panels - Fatigue Crack Propagation in Welded Base Metal
Authors: Cernescu Anghel , Remes Heikki , Lehto Pauli , Romanoff Jani
Published: March 2014

The all-metal web-core sandwich structure consists of two face plates stiffened by one-directional system of web plates. These web core sandwich structures are used in many structural applications such as ship hulls, offshore platforms, bridge decks, and industrial platforms. However, the stress variation caused by the service loadings can be a determinant factor for crack initiation and growth until early failure of the entire structure. This paper presents an experimental study on fatigue crack growth rate in base material from a face plate after rolling and welding. The study is focused on the analysis of the stress ratio and crack closure effect on the fatigue crack growth rate in two directions. There is a significant stress ratio effect on fatigue crack growth rate, much more pronounced in the case of crack propagation in the longitudinal direction than in the transverse propagation. For all tests, the crack closure effect is more pronounced at low stress intensity factor range (in the threshold domain).
Scattering of the Fundamental Symmetric Wave Mode Incident at a Defect on the Blind Side of a Weep Hole in an Isotropic Plate
Authors: Vien Benjamin Steven , Nadarajah Nithurshan , Chiu Wing Kong , Rose L.R. Francis
Published: March 2014

The scattering of a fundamental symmetric wave mode by a notch on the blind side of weep hole is described in this paper. It will report on findings obtained from computational simulations to determine the effect and interaction of the impinging waves with the defect on the open hole located on the blind side of the incident wave. The finite element simulation results showed mode conversions of fundamental modes, leaky edge waves on the circumferential surface and source-like diffractions radiating from the tip of the notch and hole. These findings highlight the potential of applying this wave phenomenon to quantify defect located hard-to-inspect areas by positioning actuator and sensor in accessible regions of metallic structures and is relevant to the development and improvement of current techniques in non-destructive inspection of metallic structures
Detection and Monitoring of Fatigue Cracks in Metallic Structures Using Acoustic Emission: Routes to Quantification of Probability of Detection
Authors: Gagar Daniel , Foote Peter , Irving Phil E.
Published: March 2014

The performance and reliability of Structural Health Monitoring (SHM) techniques remain largely unquantified. This is in contrast to the probability of detection (POD) and sensitivity of manual non destructive inspection methods which are well characterised. In this study factors influencing the rates of emission of Acoustic Emission (AE) signals from propagating fatigue cracks were investigated. Fatigue crack growth experiments were performed in 2014 T6 aluminium sheet to observe the effects of changes in crack length, loading spectrum and sample geometry on rates of emission and the probability of detecting and locating the fatigue crack. Significant variation was found in the rates of AE signal generation during crack progression from initiation to final failure. AE signals at any point in the failure process were found to result from different failure mechanisms operating at particular stages in the failure process.
Retrofitting for Fatigue Cracks at Connection between the Main Girder Web and Lateral Girder Flange Using the Bolting-Stop-Hole Method with Attached Plates
Authors: Mori Takeshi , Sasaki Kazuya , Nakanuma Mitsuru
Published: March 2014

For the purpose of clarifying the fatigue strength of a main girder web connected to a lateral girder flange which is repaired by bolting-stop-hole method with attached steel plates, fatigue tests have been performed on girder specimens. In addition, fatigue tests have been also carried out on small scale plate specimens modeling the repaired parts in order to investigate the fatigue crack origin and fatigue strength of the repaired parts. Furthermore, the effect of the repair method has been compared with those of stop-hole method and/or bolting-stop-hole method through the fatigue tests. It has been confirmed that the fatigue strength of the repaired parts is considerably high and almost equal to that of friction type of high strength bolted connections.
High-Cycle Fatigue Behaviour of Pure Tantalum under Multiaxial and Variable Amplitude Loadings
Authors: Marechal David , Saintier Nicolas , Palin-Luc Thierry , Nadal François
Published: March 2014

Due to its specific mechanical properties, tantalum is often used in strength-demanding military applications. High-cycle fatigue (HCF) behaviour of pure tantalum, however, has been rarely reported and the mechanisms at stake to account for deformation under cyclic loadings are still badly understood. This paper aims at better understanding the fatigue behaviour of tantalum and at clarifying the mechanisms of damage formation encountered under such loadings. HCF experiments performed at room temperature on commercially-pure tantalum are presented. Mean stress effects were investigated in the aim of clarifying the interaction between fatigue and creep. Fracture mechanisms were observed to vary from intergranular to transgranular depending on applied stress amplitude and mean stress. Damage mechanisms were investigated under tension and torsion. Results are analyzed in the light of existing fatigue criteria, the limitations of which are discussed. Finally, complex sequential loadings, representative of in-service loadings, were applied to tantalum smooth specimens. The contribution of each loading sequence to the overall damage was quantified and analyzed in terms of linear or non-linear cumulative damage rule.
A New Criterion for Evaluating Multiaxial Fatigue Damage under Multiaxial Random Loading Conditions
Authors: Anes Vitor , Reis Luís G. , de Freitas Manuel
Published: March 2014

Generally, mechanical components or structures are subjected to random and a three-dimensional stress state; there are very few field loading paths which can be experimentally fully simulated in laboratory. Loading path parameters such as load sequence, stress level or proportionality/non-proportionality presences are unknown variables with unknown levels under random loading conditions which are impossible to modulate in laboratory because the load spectra is unknown. The load spectrum depends on numerous factors such as environmental, mechanical or user behavior. At design stages the fatigue life estimation is based on typical loading paths or typical loading spectra, however that assumption may be very different from the usage regime. From here it can be concluded that the random multiaxial fatigue issue is of utmost importance to monitoring the in-field damage accumulation. This work presents a proposal to estimate the accumulated damage resulted from multiaxial random loadings based on the SSF equivalent stress and SSF virtual cycle counting concept.
Fatigue Failure Life of SS400 Steel under Non-Proportional Loading in High Cycle Region
Authors: Morishita Takahiro , Liu Shu Li , Itoh Takamoto , Sakane Masao , Kanayama Hideyuki , Sakabe Masahiro , Takeda Norio
Published: March 2014

This study discusses fatigue properties of low carbon steel under multiaxial non-proportional loading and an evaluation of failure life. Multiaxial fatigue tests under non-proportional loading with various stress amplitudes were carried out using a hollow cylinder specimen in low and high cycle regions at room temperature. In the test, three types of strain/stress path were employed. They are a push-pull, a reversed torsion and a combined push-pull and reversed torsion loadings in which stress amplitudes used were constant and random. This study evaluates an effect of non-proportional loading on fatigue life in the high cycle fatigue region to discuss the applicability of ΔεNP proposed by Itoh et al. on life evaluations in the high cycle region and under random loading.
Initiation from Low Cycle Fatigue to Gigacycle Fatigue
Authors: Bathias Claude , Wang Chong
Published: March 2014

This paper is devoted to the initiation of fatigue crack in Armco iron from low cycle fatigue to gigacycle fatigue. It is shown that the basic mechanisms of initiation are very similar from a physical point of view: PSB and Grain boundary cracking. But the mechanical aspect is specific in LCF and in GCF.
Evaluation of Bonding between High Modulus CFRP Sheet and Steel after Environmental Exposure and Fatigue Loading
Authors: Liu Hong Bo , Borrie Daniel , Zhao Xiao Ling , Bai Yu , Singh Raman R.K.
Published: March 2014

This study investigated the effects of fatigue loading and corrosive environment on bonding strength and failure modes of Carbon Fibre Reinforced Polymer (CFRP)-laminated steel. A series of tests on CFRP bonded steel plate joints was conducted. The joints were immersed in the temperature controlled sea-water with a preload. After immersions for one and six months, they were subjected to cyclic loading for a pre-set number of cycles, and then tensioned to failure. The effect of fatigue loading alone was studied by the authors in the past. In the present study, the results of the cyclic and static loading tests were compared. The comparisons between the current and previous results have provided data on the durability of CFRP/steel joints under this environmental condition.
Fatigue Behaviour of Friction Stir Welded Steel Joints
Authors: Azevedo José , Infante Virgínia , Quintino Luisa , dos Santos Jorge
Published: March 2014

The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.
Effects of Carbon Fibre Geogrid Reinforcement on Propagation of Cracking in Pavement and Augmentation of Flexible Pavement Life
Authors: Dizaj Amir Barry , Ziari Hasan , Nejhad Mahmood Ahmadi
Published: March 2014

Most of the distresses in flexible pavement are due to cracking and rutting. Geogrids distribute the street and loads to adequate area and cause augmentation bearing capacity. This project surveys the function of carbon and Glass fiber Geogrids on Delay of Crack propagation in flexible pavement and placement configuration in pavement structure. Four point bending loading applied to beams with dimension 50.8*63.5*381 mm and 6.5 mm tolerance (AASHTO TP8-96). According to the received specimen from cutting slabs of case study toward chart fatigue life, for each condition reinforced and unreinforced beams 3 sample in 4-strain level were experimented. Simulatedrepeated loading with a frequency 10 Hz simulate high-speed traffic was applied to beam fatigue specimen. Based on definition (AASHTO T321-07) assumed achieving to 50% first bending stiffness for end of the fatigue life indicate a significant reduction in the rate of crack propagation in reinforced samples with carbon geogrids compared to unreinforced ones, augmentation service life is up to 3.5fold and placing the geogrid at a one-third depth of overlay thickness from the bottom provide the maximum service life.
Specimens for Simultaneous Mode II, III and II+III Fatigue Crack Propagation: Elasto-Plastic Solution of Crack Tip Stress-Strain Field
Authors: Horníková Jana , Šandera Pavel , Žák Stanislav , Pokluda Jaroslav
Published: March 2014

Determination of fatigue crack growth characteristics under shear-mode loading is a rather complicated problem. To increase an efficiency and precision of such testing, special specimens enabling simultaneous propagation of shear cracks under II, III and II+III loading modes started to be used rather recently. K-calibration of these specimens was performed and, after unique pre-crack and heat-treatment procedures, effective thresholds in several metallic materials could be measured. However, a description of crack growth rate in terms of appropriate fracture mechanics quantities demands a precise assessment of plastic zone size under various shear-mode loading levels. This contribution is focused on the numerical elasto-plastic analysis of stress-strain field at the crack tip in specimens made of a pure polycrystalline (ARMCO) iron. The results reveal that the small scale yielding conditions are fulfilled in the near-threshold region. Starting from ΔK values approximately two times higher than the threshold, however, the ΔKJ or ΔJ approach should already be utilized. Probably the most interesting result of the analysis lies in a simple procedure that enables us to separate individual loading components ΔKJ,II and ΔKJ,III, applied in the mixed-mode II+III part of the specimen, by comparing elasto-plastic and elastic solutions.
Crystal Plasticity Finite Element Simulations of Polycrystalline Aluminium Alloy under Cyclic Loading
Authors: Li Ling , Shen Lu Ming , Proust Gwénaëlle
Published: March 2014

A three-dimensional crystal plasticity (CP) finite element model is developed to reproduce the grain level stress concentration and deformation of polycrystalline aluminium alloy 7075 (AA7075) during fatigue experiments. The grains contained in the model possess the same size and crystallographic orientations obtained from electron back-scatter diffraction experiments. A modified CP constitutive model, which considers the backstress evolution, is employed to describe the mechanical behaviour of AA7075 under cyclic loading. A round-notched specimen from a fatigue test is simulated using the proposed CP model. Convergence studies in terms of mesh density and plastic deformation zone size are carried out to determine the appropriate conditions for the simulation. The simulation results are compared with those obtained using the elasto-plastic model and the CP model without grain morphology. The comparison indicates that with the embedded grain morphology, the proposed model can capture very well the local response induced by the microstructure features, which is vital to the accurate fatigue life prediction of aluminium alloys.
Wavelet-Based Feature Extraction Algorithm for Fatigue Strain Data Associated with the k-Means Clustering Technique
Authors: Putra Teuku Edisah , Abdullah Shahrum , Schramm Dieter , Nuawi Mohd Zaki , Bruckmann Tobias
Published: March 2014

The study presents the development of a wavelet-based segmentation algorithm for fatigue life assessment. Strain data was extracted using the Morlet family. The extraction process identified damaging segments, and it was able to shorten the original signal by 74.3%, with less than 10% difference with statistical parameters. The extraction algorithm was able to retain at least 97.9% of fatigue damage. The damaging segments drawn were clustered using the k-means method to provide three groups of segments, i.e., lower, moderate, and higher groups representing statistical values. The approach was suggested as an alternative method for evaluating and clustering fatigue strain signals.
The Effect of Ralstonia pickettii on Environmental Fatigue Crack Growth of 7xxx Series Aluminum Alloys
Authors: Galyon Dorman Sarah E. , Hoff Benjamin K. , Reid Timothy A. , Collins Sarah E. , Henning Daniel H.
Published: March 2014

As more industries and nations focus on environmental protection, the desire to develop non-toxic, sustainable coatings to protect against corrosion becomes a primary focus. One of the areas on the cutting edge of new coating development is the use of bacteria in corrosion prevention coatings. For many years the focus in the corrosion community was on microbial influenced corrosion with the assumption that all bacteria had negative consequences for corrosion and corrosion fatigue. More recently it has been documented that a variety of bacteria can protect against general surface corrosion. None of the work to date on bacteria preventing general corrosion has shown that the inhibitive effects could also be applied to corrosion fatigue. Researchers at the United States Air Force Academy discovered that a bacteria, Ralstonia pickettii, is capable of reducing the fatigue crack growth rate of AA7075-T651 and AA7475-T7351 in 0.06M NaCl to near that of chromate. In cycles to failure testing in 0.06M NaCl the sample life was extended approximately 5 to 6 times depending on the fatigue loading variables compared to samples in 0.06M NaCl without the bacteria. The mechanism behind the corrosion fatigue protection is being investigated in hopes that it could lead to the development of new coatings to reduce corrosion fatigue. The current theories behind how the bacteria slows corrosion fatigue crack propagation are (1) presence of a biofilm, (2) metal sequestration and replating on the crack surface, (3) desalination of the test solution, and (4) oxide layer development and repair.
The Explanation of Stress Ratio Effect and Crack Opening Corrections for Fatigue Crack Growth in Metallic Materials
Authors: Alderliesten Rene C.
Published: March 2014

This paper discusses the physical meaning of crack opening corrections in fatigue crack growth analyses proposed in the literature. To provide an explanation concerning the physical relevance of these corrections, an energy approach is proposed to evaluate fatigue loading conditions. Considering cyclic loading in terms of cyclic energy rather than in stress cycle, explains the origin of the crack opening corrections.
Influence of Martensitic Phase on Microcrack Propagation in a Ferritic-Martensitic Steel
Authors: Brueckner-Foit Angelika , Pitz Pascal , Zeismann Frank , Zellmer Lisa
Published: March 2014

Hard phases such as martensite regions affect micro-crack extension by blocking the plastic zone ahead of the crack tip, but also by changing the crack opening which can be taken as loading quantity for cracks. This paper deals with the measurement of crack opening for microcracks in a ferrite/martensite dual phase steel. The methods used are in-situ testing in the SEM, X-ray tomography, and digital image correlation. It was found that martensite regions affect the relative displacement of the crack phases both at the crack tip and in the crack wake.
Fatigue Crack Growth Behavior in the Threshold Region
Authors: Forman Royce G. , Zanganeh Mohammad
Published: March 2014

This paper describes the results of a research study conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question of the validity of threshold region test data. The validity question relates to the position held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R data fans out from the high R data. This fanning behavior or elevation of threshold values in the low R tests is generally assumed to be caused by an increase in crack closure in the low R tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure [1-3]. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is more a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning is caused by fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is eliminated when testing is performed in dry air.
Damage Evaluation of Ferrite and Ferrite-Pearlite Steel during Fatigue Crack Initiation by EBSD
Authors: Hayakawa Mamoru , Wakita Masayuki , Nakayama Eisuke
Published: March 2014

Orientation changes during fatigue crack initiation in ferrite and ferritepearlite steel were evaluated by electron backscatter diffraction (EBSD). Ferrite steel with different grain sizes and ferritepearlite steel with different carbon contents were prepared. EBSD measurements and fatigue tests were alternately performed using a small specimen. The tests on both ferrite and ferritepearlite steel suggest that the initial cracks were observed in the ferrite matrix. Thus, crystal rotation induced by fatigue in ferrite matrix is quantitatively evaluated by two misorientation parameters: grain reference orientation deviation, which is the misorientation between measuring points and the average orientation in each grain, and crystal misorientation at the same point before and after fatigue testing.
Fatigue Behavior of Ultrafine Grained Medium Carbon Steel with Different Carbide Morphologies Processed by High Pressure Torsion
Authors: Ruffing Christoph , Kerscher Eberhard
Published: March 2014

The increased attention that ultrafine grained (UFG) materials have received over the last decade has been provoked, not least, by their high strength in combination with remarkable ductility. The main focus of our investigation was the evaluation of the effect of different carbide morphologies in the initial microstructure on the fatigue behavior after high pressure torsion (HPT) treatment of SAE 1045 steel. In our case HPT increased the hardness by a factor of 1.75 - 3.2 compared to the initial states. The achieved hardness maximum was 726 HV. The amount of increase depended on the initial carbide morphology. By stress controlled cyclic four point bending tests with a load ratio of 0.1 endurance limits were determined for the initial and HPT states. The endurance limit increased linearly with hardness until 500 HV and independently of the carbide morphology. All fracture surfaces were investigated by SEM after the fatigue tests. They revealed pretty flat fatigue fracture surfaces with crack initiation at the surface or rather at non-metallic inclusions for the UFG states. Morphology and crack initiation mechanisms were changed by severe plastic deformation compared with the coarse grained initial state. Residual fracture surfaces with a spheroidal initial microstructure showed well-defined dimple structures also after HPT at high fatigue limits and high hardness values. In contrast, the specimens with initial tempered microstructure showed rather brittle and rough residual fracture surfaces.
Effect of Geometry and Distribution of Inclusions on the VHCF Properties of a Metastable Austenitic Stainless Steel
Authors: Grigorescu Andrei , Hilgendorff Philipp Malte , Zimmermann Martina , Fritzen Claus Peter , Christ Hans Jürgen
Published: March 2014

The effect of inclusions on the VHCF properties of a metastable austenitic stainless steel in undeformed and predeformed condition was studied. The material contains an inhomogeneous distribution of elongated oxide inclusions. TEM investigations of foils extracted by means of FIB technique show that the stress concentration at the inclusions is compensated by plastic deformation in the austenite phase preventing internal crack initiation in the VHCF regime for the non-predeformed, i.e., almost martensite-free condition. The effect of the spatial distribution and geometry of the inclusions on the VHCF strength was systematically investigated for the predeformed condition. Samples were monotonically predeformed at -80°C resulting in a martensite content of about 60% and then fatigued in high frequency testing machines. Since mechanical components are in practice subjected to complex cyclic loading situations, samples were tested both parallel and transversal to the rolling direction, in order to cover a broad field of applications. The higher notch sensitivity of the martensite phase leads to internal crack initiation from inclusions supported by the formation of a fine granular area (FGA). The change in testing direction perpendicular to the rolling direction reduces the number of cycles to failure due to the increased stress intensity factor at inclusions which leads to internal crack initiation without the formation of a fine granular area. These findings are discussed on the basis of a detailed microstructural characterization of the material focusing on the effect of martensite content, the inclusion morphology with respect to the rolling direction and the load axis applied
Fatigue Life Analysis of Specimens Subjected to Infrequent Severe Loading Using a Nonlinear Kinematic Hardening Cyclic Plasticity Model
Authors: Hu Wei Ping , Wallbrink Chris
Published: March 2014

For engineering structures subjected to cyclic load, fatigue failure normally occurs at geometrical discontinuities such as holes and notches. In aircraft structures, such locations may experience occasional severe loading that can cause appreciable local plastic deformation. This poses a significant challenge to fatigue life modelling. For such locations subjected to variable amplitude loading of a large number of cycles, the numerical analysis of fatigue life requires an accurate and robust model for cyclic plasticity, in order to reliably determine the stress and strain response. In this paper, we explore the potential of a nonlinear kinematic hardening model in improving fatigue life analysis. The work is motivated by the inability of an existing strain-life model to capture the difference in fatigue damages caused by an unclipped and clipped service load spectrum. Preliminary results show that the strain-life method based on the nonlinear kinematic hardening model was able to qualitatively demonstrate the trend in fatigue life for two critical locations analysed, and it was able to give much improved quantitative prediction for one location. Further work is under way to verify the model against more test data and to improve its capability in dealing with material cyclic softening or hardening behaviour.
An Overview of the Fatigue of Polychloroprene Rubber
Authors: Poisson Jean Louis , Lacroix Florian , Méo Stéphane , Berton Gaelle , Ranganathan Narayanaswami
Published: March 2014

Some fundamental studies carried in a synthetic rubber - Chloroprene CR29 are presented in the first part of the paper. A critical analysis of test results, shows that an energy based approach permits the determination of fatigue lives in this material. This aspect is further enhanced by biaxial fatigue tests in the same material. These tests covering a life range from 10000 to 1000000 cycles show that the energy based model is very efficient to describe the fatigue behavior. Some evidence of strain induced crystallization (previously observed in natural rubber) with associated life enhancement at high load ratios is also presented. A comprehensive model based on the determination of the constitutive laws taking into account the viscoelastic behavior is developed showing excellent correlation with experimental data.
In Situ Study of the Mechanisms of High Temperature Damage in Elastic-Plastic Cyclic Loading of Nickel Superalloy
Authors: Petrenec Martin , Polák Jaroslav , Šamořil Tomáš , Dluhoš Jiří , Obrtlík Karel
Published: March 2014

In-situ Low Cycle Fatigue test (LCF) at temperature 635 °C have been performed in SEM on flat specimen ofcast Inconel 713LC superalloy. The aim of the investigation was to studymechanisms of the fatigue damage during elastic-plastic cycling by theobservations of the characteristic surface relief evolution and theaccompanying internal dislocation structures. The selected locations on thesurface were systematically studied in-situ and documented by SEM and usingAFM. The surface relief in the first tensile half-cycle was formed by numerousslip steps on the primary slip planes (111). In the following compressionhalf-cycle additional opposite slip were formed. The relief was modified in thenext cycles but without forming additionally new slip traces in the primarysystem. The reorientation of two grains in the gauge area was measured usingEBSD. At the end of cyclic loading the relation between surface persistent slipmarkings and persistent slip bands in the interior of the material wasdocumented by TEM on lamella prepared by FIB. The early stages of extrusion andintrusion formation were documented. The damage mechanism evolution is closelyconnected with the cyclic strain localization to the persistent slip bands thatare also places of fatigue crack initiation.
Very High Cycle Fatigue in Pulsed High Power Spallation Neutron Source
Authors: Xiong Zhi Hong , Futakawa Masatoshi , Naoe Takashi , Maekawa Katsuhiro
Published: March 2014

Very high cycle fatigue degradation of type 316L austenitic stainless steel, which is used as the structural material of neutron spallation sources under intensive neutron irradiation environment, is investigated by using an ultrasonic fatigue testing machine. The strain rate imposed on the structure of neutron spallation source is almost equivalent to that produced in the testing machine. The temperature on the surface was controlled by the air-cooling. The effect of strain rate on the fatigue strength is recognized to increase the fatigue limit.
Investigation of Fatigue Crack Acceleration under Variable Amplitude Loading for a Structural Steel and Aluminium Alloy
Authors: Doré Matthew J. , Maddox Stephen J.
Published: March 2014

There are currently serious doubts about the accuracy of Miners rule for designing welded structures subjected to variable amplitude loading, particularly under spectra cycling down from a constant maximum stress. The deficiency has been attributed primarily to stress interaction effects that cause crack growth acceleration. In this paper the crack growth response of a structural steel and an aluminium alloy to a loading spectrum designed to promote fatigue crack acceleration is studied and the potential mechanisms responsible are evaluated.
Comparison of Tensile and Compressive Creep-Fatigue Damage Behavior of Cellular Composites
Authors: Diel Sergej , Huber Otto
Published: March 2014

The damage behavior of cellular composites under creep and cyclic tensile loading conditions is investigated. Tensile cyclic tests at 1 Hz and 20 Hz test frequency and creep tests are performed and compared to previous investigations under compressive loading. In contrast to the compressive loading, no frequency effect is identified in tensile loading and the fatigue curves have steeper slopes. The damage behavior is analyzed by means of scanning electron microscope (SEM) and high resolution 3D X-ray tomography. It is found that microcracks are forming in the glass foam granules first; the final failure is caused by a macrocrack passing through the glass foam granules and the matrix. The damage evolution is measured in terms of stiffness loss of the specimen and is found to have different behavior than in compression.
Nitriding Effect on Corrosion Fatigue Strength of Low Alloy Steel in 1% HCl Aqueous Solution
Authors: Ebara Ryuichiro , Fukushima Yuya , Nakagawa Shintaro , Ueji Rintaro
Published: March 2014

In this paper the emphasis is focused upon nitriding effect on corrosion fatigue strength of Cr-Mo low alloy steel in 1% HCl aqueous solution.Corrosion fatigue strength enhancement of Cr-Mo low alloy steel by nitriding is discussed on the basis of the corrosion fatigue testing results on gas and ion nitrided Cr-Mo low alloy steel plate specimen with 3.5mm thickness in 1%HCl aqueous solution. It can be concluded that residual compressive stress distributed on the nitrided specimen surface caused improvement of corrosion fatigue strength of Cr-Mo low alloy steel.
Analysis of Black Hawk Main Transmission Support Beam In-Service Fatigue Crack
Authors: Vine John , Jackson Phil , Hu Wei Ping
Published: March 2014

The Australian Defence Science and Technology Organisation (DSTO) was recently tasked with evaluating an in-service fatigue crack discovered in the primary structure of an Australian Army Black Hawk helicopter. This crack, discovered early in the affected components service life, was quite large and subsequent fractographic analysis generated substantial information with respect to its growth characteristics. Consequently, it was decided to use this in-service fatigue crack to test the ability of those methods and technologies being developed at DSTO to model and assess a ‘real’ example of helicopter airframe fatigue cracking. This paper details the process of analysing an in-service fatigue crack using methods and technologies developed and/or improved at DSTO in the areas of visualisation, fatigue spectra generation, load and stress analysis, and crack growth prediction. Results will highlight the effectiveness of the methods and techniques in modelling the observed fatigue damage and areas where further improvements are required.
Probabilistic Vibration Analysis of a Mistuned Integrally Bladed Disk
Authors: Chen Guang Xia , Hou Jian Fu
Published: March 2014

Abstract. The objective of this paper is to probabilistically evaluate the effects of mistuned sectors on the dynamic characteristics of an integrally bladed disk (blisk). Small blade to blade physical variation in a disk is termed as mistuning. In this study, the dynamic characteristics of the perfectly tuned blisk were firstly analysed as a baseline. Secondly, a probabilistic approach is used for the mistuning analysis of a blisk. A reduced-order method named as the subset of nominal modes (SNM) was used to generate modes for a mistuned blisk from a cyclic perfectly tuned FE model without creating the full model. Furthermore, as only the modes with natural frequencies close to the modes of interest were considered, a relatively shorter computational time and a much smaller model size than a full blisk model is used. Therefore, the dynamic characteristics of the forced response for random mistuned blisks were obtained.
The Effect of the Microstructure and Defects on Crack Initiation in 316L Stainless Steel under Multiaxial High Cycle Fatigue
Authors: Guerchais Raphaël , Morel Franck , Saintier Nicolas
Published: March 2014

The aim of this study is to analyse the influence of both the microstructure and defects on the high cycle fatigue behaviour of the 316L austenitic stainless steel, using finite element simulations of polycrystalline aggregates. High cycle fatigue tests have been conducted on this steel under uniaxial (push-pull) and multiaxial (combined in-phase tension and torsion) loading conditions, with both smooth specimens and specimens containing artificial semi-spherical surface defects. 2D numerical models, using a cubic elastic constitutive model, are created to determine the degree of heterogeneity of the local stress parameters as a function of the defect size. This has been done for one microstructure using several orientation sets generated from the initial texture of the material. The grains are explicitly modelled and the anisotropic behaviour of each FCC crystal is described by the generalized Hookes law with a cubic elasticity tensor. From the simulations carried out with different defect sizes and orientation sets that are representative of the real texture of the tested material, statistical information regarding mesoscopic mechanical fields provides useful insight into the microstructural dependence of the driving forces for fatigue crack nucleation at the mesoscopic scale (or the scale of individual grains). The results in terms of the stress fields and fatigue crack initiation conditions are determined at both the mesoscopic and macroscopic scales. The results from these FE models are used along with an original probabilistic mesomechanics approach to quantify the defect size effect. The resulting predictions, which are sensitive to the microstructure, include the probability distribution of the high cycle fatigue strength.
The Cyclic Loading as a Result of the Stick-Slip Motion
Authors: Karachevtseva Iuliia , Dyskin Arcady V. , Pasternak Elena
Published: March 2014

We investigate the influence of oscillating normal force on the frictional sliding. Frictional sliding in the case of a simple mass-spring model of Burridge and Knopoff type demonstrates stick-slip even when the friction coefficient is constant. Oscillations of the normal force in this case do not produce noticeable changes in the stick-slip sliding mode. A completely different picture is observed when the oscillations of normal force are applied to the system, which is in the state of steady sliding. In this case the normal oscillations turn the steady sliding into stick slip. A special case is observed when the normal force oscillates with the eigen frequency of the stick-slip motion. Then, no matter how small the amplitude of oscillations is the system reaches the same final stick-slip regime. The time required to reach this limiting regime is inversely proportional to the amplitude of oscillations of the normal force.
The Fracture Characteristic of Mode III Rock Crack under Different Temperature
Authors: Li Li Yun , Tang Tie Wu , Xu Zhi Qiang , Liu Wen Bin , Zhou Guo Yane
Published: March 2014

A series of torsion tests under different temperature were carried out with circumferential notched cylindrical rock specimens. By this kind of specimens, mode III rock crack propagation in real meaning was realized. The initiation torsion M of the mode III rock crack was measured under different temperature. The variation law of M v.s. temperature T was obtained. The initiation stress near crack tip under different temperatures was calculated by finite element method, and then, the mode III fracture toughness KIIIC of the rock was obtained by further calculation. The experiment and numerical results show that the mode III fracture toughness of the rock decreases with the temperature increase. The results of the paper can be used in the design of deep underground engineering ,disaster prevention and mitigation engineering.
Fretting Fatigue Behavior of Titanium Alloy Coated with Functionally Graded Ti/TiN Film
Authors: Nakatani Masanori , Shimizu Shota , Harada Yasunori , Uchida Hitoshi
Published: March 2014

The influence of functionally graded TiN coating on fretting fatigue behavior of titanium alloy was investigated. The coating was deposited using an ion beam assisted deposition technique. TiN film was fabricated by an electron beam evaporation of titanium and simultaneous nitrogen ion bombardment. An acceleration voltage of ion beam was set at 0.2 or 2.0 keV. The functionally graded layer was fabricated by varying the mixing ratio of nitrogen/argon ion beam. The mixed layer became thicker by an increase in acceleration voltage. The adhesive strength and wear resistance were improved with an increase in the acceleration voltage. Moreover, they were significantly improved by inserting the functionally graded layer. The fretting fatigue tests were conducted using a four-point bending fatigue testing machine. The fretting fatigue life of specimen coated with monolayer TiN film was longer than that of uncoated specimen. The TiN coating with functionally graded layer was the most effective to improve the fretting fatigue life.
Fatigue Lifetime and Crack Growth Behavior of WC-Co Cemented Carbide
Authors: Mikado Hiroko , Ishihara Sotomi , Oguma Noriyasu , Masuda Kenichi , Kawamura Shingo
Published: March 2014

It is well known that WC-Co cemented carbides have excellent wear resistance. However, information about their fatigue crack growth behavior and fatigue properties is limited. In the present study, rotating bending fatigue tests were carried out on a fine grained WC-Co cemented carbide to evaluate its fatigue lifetime and crack growth behavior. From observations of the micro-notched specimen surface during the fatigue process, it was revealed that most of the fatigue lifetime of the tested WC-Co cemented carbide is comprised of crack growth cycles. Using the basic equation of fracture mechanics, the relation between the rate of fatigue crack growth da/dN and the maximum stress intensity factor Kmax of the WC-Co cemented carbide was derived. From this relation, both the threshold intensity factor Kth and the fatigue fracture toughness Kfc of the material were determined. Fatigue lifetime of the WC-Co cemented carbide was estimated based on the fatigue crack growth law.
Laser Shock Peening to Repair, Design and Manufacture Current and Future Aircraft Structures by Residual Stress Engineering
Authors: Furfari Domenico
Published: March 2014

This paper will provide an overview on potential applications for the aerospace industry for repairing aircraft as well as to ensure salvage for identified hot spots in terms of fatigue and crack growth performance. Residual stress engineering is a field of engineering aiming to improve the economic and ecological impact of future aircraft structures by controlling the residual stresses induced by Laser Shock Peening (LSP). Managing the residual stresses for designing structures represents an innovative approach for next generation aircraft. Predicting crack turning induced via a LSP treatment and the optimization of the LSP treatment itself for reaching the crack growth design stress for the targeted weight benefit will be discussed. Advanced forming processes in aircraft manufacturing represent another potential area of interest and the benefits and challenges of applying laser peen forming in this context will be presented. The aeronautical industry requirements for future developments of the laser shock process will also be included for applications ranging from the repair environment to design and manufacturing of aircraft structures.
Influence of Catalyst on the Extinguishing Effect of Inorganic Salt Fire Extinguishant
Authors: Zhang Xiang , Yin Chao Lu , Li Ping Li , Zhang Fan
Published: March 2014

In this paper, the influence of catalytic on the extinguishing effect of inorganic salt fire extinguishant has been studied. Results of TG test and burning test indicated that catalytic synergist ammonium tungstate and sodium tungstate can effectively increase the fire extinguishing effect of the inorganic salt fire extinguishant, and sodium tungstate has a better catalytic synergistic effect than ammonium tungstate.
Effect of Aluminum on Mechanical and Frictional Properties of Copper Cladding Iron-Based Braking Material
Authors: Yang Ping , Fu Chuan Qi , Wang Zhou
Published: March 2014

Fe-20wt%Cu-Al braking materials were prepared by induction heating sintering method combined with the Copper cladding iron matrix with various aluminum elements. Effects of Aluminum on surface morphology, Mechanical and frictional properties of Cu-Fe-based Braking Material were analyzed by Scanning Electron Microscope (SEM), machine test and friction-wear test. Lastly suitable parameters of the process are decided. Meanwhile, wear mechanisms were discussed. The results showed that the prepared shaking materials with aluminum content of 3wt%, silicon carbide content of 5wt%, manganese and chromium content of 5wt% and copper cladding iron power content of 87wt% had excellent performance.
Preparation of Conductive Nanosilver Ink and its Application on RFID Tags
Authors: Fu Ji Lan , Li Ya Ling , Mo Li Xin , Wang Yu , Ran Jun , Pang Zhe , Ma Yan , Li Lu Hai
Published: March 2014

The recent dramatic progress in the printed electronics and flexible electronics, due to the universality of the substrates including the foldable and stretchable substrates, has opened a new prospect in the field of future electronics. In this paper, silver nanospheres in large-scale are synthesized, the nanosilver ink with 63.88% silver content are prepared and a new type of highly conductive and far identify distance RFID tags are manufactured. Especially there are no resin and other additives containing in our conductive ink which satisfy the rheological characteristics and process of screen printing. The tags exhibit the best radiation performance own to there is no high temperature sintering in need. The surface resistance of the tags could be 80 mΩ/, and the identify distance reach to 6.0m.
Keywords:silver nanoparticles, conductive ink, RFID tags
Effect Factors Study on Ultimate Strength of Aluminum Stiffened Plates under Cyclic Loading
Authors: Cui Hu Wei , Yang Ping , Zhou Liang , Shen Can , Chen Xiao Jing
Published: March 2014

Nonlinear finite element method is used in this paper to research the ultimate strength characteristics of aluminum stiffened plates under uniaxial tension-compression cyclic loading. This paper focused on the effect of the distribution mode of HAZ, the range of HAZ and different cyclic loading process on the ultimate strength of aluminum stiffened plates. The results obtained have a certain reference value to the design and manufacture of aluminum stiffened plates.
Studies on the Composition Characteristics of Pyrite from Dabaoshan Polymetallic Ore Deposit, Northern Guangdong Province
Authors: Fu Wen Chun , Pan Hui Bin , Kang Zhi Qiang
Published: March 2014

Pyrite composition characteristics can reflect its physical and geochemical formation backgrounds, also are the important parameters to further discuss the genesis of minerals and ore deposit. In this paper, major and trace elements of 13 pyrite samples from Dabaoshan polymetallic ore deposit were analyzed using EPMA, the results suggest that S/Fe atomic ratio of pyrite in dacitic porphyries were similar with reference standard value, however that ratio in granodioritic porphyries is 2.051, which is slightly higher than the reference standard value; trace elements Cu, Zn and Pb show the characteristic of high oxygen fugacity settings, the Co content in pyrite was significantly lower than that of Ni, and Co/Ni is far less than 1, all the evidences show the characteristics of sedimentation-reformation ore deposit.
Development of Edible Packaging Materials
Authors: Zhang Sheng , Gu Wen Chao , Cheng Zheng Yong , Li Ying , Gu Wen Juan
Published: March 2014

The development of edible packaging material was introduced in this paper. The concept, types and the characteristics of edible packaging material were expounded separately. The history and main representational technologies in the development of edible packaging material in China were recommended. And the developing direction in the world was also explained in detail. The future development of this kind material was discussed. And the prospect of edible packaging materials was brought forward.