bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Mechanical Properties of CNX and CPX Thin Solid Films
Authors: Broitman E. , Furlan A. , Gueorguiev Gueorgui K. , Czigány Zsolt , Högberg H. , Hultman L.
Published: September 2011

The inherent resiliency, hardness and relatively low friction coefficient of the fullerene-like (FL) allotrope of carbon nitride (CNx) thin solid films give them potential in numerous tribological applications. In this work, we study the substitution of N with P to grow FL-CPx to achieve better cross- and inter-linking of the graphene planes, improving thus the material’s mechanical and tribological properties. The CNx and CPx films have been synthesized by DC magnetron sputtering. HRTEM have shown the CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 °C and for a phosphorus content of 10-15 at.%. These films show better mechanical properties in terms of hardness and resiliency compared to those of the FL-CNx films. The low water adsorption of the films is correlated to the theoretical prediction for low density of dangling bonds in both, CNx and CPx. First-principles calculations based on Density Functional Theory (DFT) were performed to provide additional insight on the structure and bonding in CNx, CPx, and a-C compounds.
Elastic-Plastic FEM Modelling of the Single Overload Effect on the Fatigue Crack Front Shape
Authors: Materna Aleš , Oliva Vladislav
Published: September 2011

A 3D elastic-plastic FEM model for prediction of planar fatigue crack growth is presented. The model is based on the concept of local low-cycle fatigue of a small material volume in front of a high cycle crack. A local crack front advance is modelled by the successive release of finite element mesh nodes in the plane of propagation. The release of the nodes is controlled by the value of the Smith-Watson-Topper fatigue damage parameter in the surrounding elements. The effect of the single tensile overload on the fatigue crack growth and on the fatigue crack front shape is modelled.
Energy Principle in Crack Propagation
Authors: Song Hai Yan , Fan Tao
Published: September 2011

Fracture mechanics is an engineering discipline, which originated from Griffith energy-balance concept. The energy method is the most powerful analytical tool for fracture mechanics. Starting from energy principle in crack propagation, quasi-static governing equations and energy release rate of DCB specimen can be derived by energy principle in this paper. Finally, some correlative problems are discussed.
Infrared Thermographic Analysis of Railway Brake Disc during Braking
Authors: Kim Jeong Guk , Kwon Sung Tae , Yoon Sung Cheol , Goo Byeong Choon
Published: September 2011

The temperature monitoring on the surface of the railway brake disc was performed using high-speed infrared (IR) camera. The railway brake disc was developed for disc braking of maximum train speed of 180 km/h. The braking tests were conducted with a full scale dynamometer, and a high-speed infrared camera was employed to monitor temperature evolution on the brake disc during braking operation. The high-speed IR camera provides the measurement of temperature change during braking as well as the images of temperature contour on the brake disc surface. In general, the hot spot generation has been considered the main degradation mechanism in railway brake disc. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method.
Structure Buckling Reliability Analysis for the Underwater Super-Speed Supercavitating Vehicle
Authors: An Hai , An Wei Guang , Zhou Ling
Published: September 2011

An approach to the structure buckling reliability analysis for the underwater super-speed supercavitating vehicle is proposed in this paper. The circular ribbed part-cabin of the vehicle is simplified as the thin cylindrical shell with variable thickness. The critical buckling load coefficient of the thin cylindrical shell is solved by using semi-analytical FEM (finite element method). The structure buckling reliability index is obtained by SFEM (Stochastic Finite Element Method) combining Limit Step Length Iteration Method. A numerical example is given to analyze influences of the number of circular ribs, the coefficient of variation of elastic modulus and the coefficient of variation of the thickness of the thin shell on the structure buckling reliability index.
Corrosion Inhibition of Stress Corrosion Cracking and Localized Corrosion of Turbo-Expander and Steam/Gas Turbines Materials
Authors: Bavarian Behzad , Zhang Jia , Reiner Lisa
Published: September 2011

Stress corrosion cracking of 7050 aluminum alloys and ASTM A470 steel in the turbo expander and steam/gas turbine industry can cause expensive catastrophic failures, especially for turbo machinery systems performing in hostile, corrosive environments. Commercially available inhibitors were investigated for their effectiveness in reducing and controlling the corrosion susceptibility. Inhibitor effectiveness was confirmed with electrochemical corrosion techniques in different solutions. Polarization resistance increased with concentration of corrosion inhibitor due to film formation and displacement of water molecules. Cyclic polarization behavior for samples in the 1.0% and 5.0% inhibitors showed a shift in the passive film breakdown potential. The substantial increase in the passive range has positive consequences for neutralizing pitting and crevice corrosion cell chemistry. The strain to failure and tensile strength obtained from the slow strain rate studies for both alloys showed pronounced improvement due to corrosion inhibitor ability to mitigate SCC; the fractographic analysis showed a changed morphology with ductile overload as the primary failure mode instead of transgranular or intergranular cracking.
Interaction of Heat Checks in Aluminum Pressure Casting Dies and their Effect on Fatigue Life
Authors: Raninger Peter , Ecker Werner , Antretter Thomas , Leindl M. , Ebner R.
Published: September 2011

Pressure casting dies are exposed to harsh service conditions consisting of cyclic thermal and mechanical loading and thus undergo thermo-mechanical fatigue. Due to cyclic plastic deformation of the material near the surface of the dies the loading conditions gradually change because of the formation of tensile residual stresses which add to the stress field from external loading. This change in the stress field influences the nucleation and the growth of cracks. Typically after a few thousand casting cycles a network of heat checks forms. In such a network crack shielding has a big influence on the evolution of the crack array. Firstly, it influences the propagation rates of the cracks and secondly it may change the propagation direction compared to the case where no neighbors are present. The crack growth rate and the length at which the cracks stop growing are also influenced by the thermo-physical and mechanical properties of the die material. It was found that the shielding effects of neighboring cracks are of equal importance. Crack deflection caused by the presence of neighboring cracks can lead to break-outs at the surface ensued by fast degradation eventually necessitating the replacement of the die. Consequently, the focus in this work is put on the investigation of the interaction of cracks in a network and their effect on the fatigue life. The problem is tackled by means of an automated strategy based on the finite element method.
Dynamic J-Integral Evaluation of Three-Point-Bend Beams with Various Geometrical Dimensions
Authors: Gintalas Marius , Žiliukas Antanas , Kalniņš Kaspars
Published: September 2011

J-Integral is the main effective and commonly used tool for cracked elastic-plastic material resistance assessment. Determination of fracture toughness under impact loading conditions is related with problems of crack length measurement. Nevertheless, current experimental techniques restrict the specimen’s geometry taking into account span and height ratio, which is equal to four. Evaluation of fracture toughness estimation method which requires only experimental load-line displacement curve of single specimen is research object of dynamic fracture mechanics. This article proposes an approach of impact fracture toughness determination of elastic-plastic steel from single any size specimen test. Load-line displacement data obtained from three-point-bending tests of rectangular cross section specimens with V form single edge notch was used for J-integral calculation. Five series of specimens with different geometry were manufactured from ductile steel and tested.
Fracture Behavior of Directional TiAl Lamellar Structures
Authors: Zhang Ji
Published: September 2011

In order to assess the influences of macro- and microstructure as well as the cast flaw on the tensile properties, the fracture behavior of a number of ambient tensile TiAl specimens containing directional lamellar microstructure have been analyzed. It is found that all the fractures of tensile specimens are triggered by a critical Griffith crack. According to the desirable ambient tensile properties coincide with the initial cracking facets smaller than 600 mm, it is proposed that the detrimental effect of the random oriented lamellar colonies on the tensile properties can be eliminated through cast technology improvement.
Experimental Fracture Behavior of Polypropylene Fiber Reinforced Concrete Specimens with Variable Width
Authors: Cifuentes Héctor , Medina Fernando
Published: September 2011

This paper presents a study of the influence of polypropylene fiber reinforcement of concrete on the fracture behavior and edge effect in elements of variable width. Experimental results of fracture behavior of specimens with different cross sections are available. It has obtained more ductile behavior for specimens with trapezoidal sections (with increasing width) and inverted T-sections. Therefore, we analyze the influence of the fibers addition on the fracture behavior of these sections. Sections with gradual variation of wide and sudden change of width were analyzed. Results allow us to quantify the increase of ductility and fracture performance improvements produced by polypropylene fiber addition to concrete in these sections.
Analysis of Shear Strength of Wood
Authors: Štefić Tihomir , Jurić Aleksandar , Marović Pavao
Published: September 2011

This paper presents the analysis of different types of shear strength of wood which can differ very much due to its structure and different orientations of applied load. These combinations of wood structure and load orientations lead to different modes of fracture. The main aim of the paper is to find a relation among all types of shear strength of the wood and to reduce the number of shear tests. Furthermore, different shear strengths will be analyzed both experimentally and numerically, i.e. experimentally by testing appropriate specimens and numerically with the help of the finite element structural analysis solver Robot AutoDesk. The testing specimens will be loaded parallel and perpendicular to the wood fibres and the radial and tangential planes will be analyzed. The paper will also investigate the relation to other strengths of wood (i.e. tensile strength parallel and perpendicular to the fibres) in order to simplify the testing procedure for shear strength determination.
Application of Two Methods for Notch Fatigue Life Prediction
Authors: Negru Radu , Marsavina Liviu , Filipescu Hannelore , Caplescu Cristiana
Published: September 2011

The aim of this paper is the application of two methods for notch fatigue life assessment, methods which are based on finite element analysis: the theory of critical distances and the volumetric method. Firstly, un-notched and notched specimens (for three different geometries) were tested in tension under constant-amplitude loading. The use of theory of critical distances (TCD) to predict the notch fatigue life involves the determination of the material characteristic length L based on experimental results obtained for the un-notched and one type of notched specimens. For the others notched geometries, based on linear-elastic finite element analysis, the fatigue strength is predicted using the TCD. In order to apply the volumetric method, elastic-plastic stress field around notches are considered and notch strength reduction factor are determined. Finally, the predictions of the two methods were compared with experimental fatigue data for notched specimens.
FEA of Fretting Fatigue: A Comparison between ANSYS and ABAQUS
Authors: Abdel Wahab Magd , Hojjati Talemi R. , de Baets Patrick
Published: September 2011

Fretting fatigue occurs when two contact bodies undergo small oscillatory relative motion due to cyclic loading. It leads to fretting damage, which reduces the service life of the bodies in contact. This can be explained by the high stresses generated at the contact surface between the two bodies. Therefore, numerical analysis, such as Finite Element Analysis (FEA), would be useful to understand the fretting fatigue phenomenon and to investigate techniques to reduce its effect on fatigue lifetime of mechanical components. In this paper, FEA of fretting fatigue Aluminum specimen is carried out in order to study the stress distribution and crack initiation location. Two commercial FEA packages, namely ANSYS and ABAQUS are used to analyze the specimen. The stress distribution along the contact surface between the two bodies obtained using both codes is compared and analyzed.
Fatigue Behavior in Filled Natural Rubber: Study of the Mechanical Damage Dynamics
Authors: Munoz Luisa , Vanel Loïc , Sanseau Olivier , Sotta Paul , Long Didier , Guy Laurent , Odoni Ludovic
Published: September 2011

Rupture dynamics in reinforced elastomers is a much more complex process than in pure elastomers due to the intrinsic heterogeneous mixture of a rubber matrix with filler particles at submicronic scale. In the case of natural rubber, an additional source of heterogeneity is the strain-crystallization effect. How rupture dynamics and crack path are affected by filler particles and strain-crystallization is still a matter of debate. Actually, understanding how rupture dynamics and crack path are correlated to each other is probably an important key in order to improve long time resistance of reinforced rubbers.
Modeling Ductile Fracture Using the Discontinuous Velocity Domain Splitting Method
Authors: Ionescu Ioan R. , Oudet Edouard
Published: September 2011

Discontinuous velocity domain splitting method (DVDS) is a mesh free method which focuses on the strain localization and completely neglect the bulk deformations. It considers the kinematic variational principle on a special class of virtual velocity fields to get an upper-bound of the limit load. To construct this class of virtual velocity fields, the rigid-plastic body is splinted into simple connected sub-domains and on each such sub-domain a rigid motion is associated. The discontinuous collapse flow velocity field results in localized deformations only, located at the boundary of the sub-domains. In the numerical applications of the DVDS method we introduce a numerical technique based on a level set description of the partition of the rigid-plastic body and on genetic minimization algorithms. In the case of in-plane deformation of pressure insensitive materials, the internal boundaries of the sub-domains are parts of circles or straight lines, tangent to the collapse velocity jumps. In this case, DVDS reduces to the block decomposition method, which was intensively used to get analytical upper bounds of the limit loads. When applied to the two notched tensile problem of a von Mises material, DVDS gives excellent results with a low computational cost. Furthermore, DVDS was applied to model collapse in pressure sensitive plastic materials. Illustrative examples for homogenous and heterogeneous Coulomb and Cam-Clay materials shows that DVDS gives excellent prediction of limit loads and on the collapse flow.
Study on Quasi-Static Growing Crack Field in Visco-Elastic Compressible Material
Authors: Yang Yong , Wu Guo Hui , Tang Li Qiang
Published: September 2011

A mechanical model of the visco-elastic compressible material is established in order to investigate the viscous effect in quasi-static growing crack-tip field. The constitutive equations on the visco-elastic compressible material are deducted. Through asymptotic analysis, it is shown that in the stable creep growing stage, the elastic-deformation and the visco-deformation are equally dominant in the near-tip field, as r-1/(n-1). The asymptotic solutions of separative variable in the crack-tip field are aslo obtained. According to numerical calculation, the curves of stress, stain and displacement are given. The results indicate that the near-tip fields are mainly governed by the creep exponent ; the stress fields of mode I and mode II is slightly affected by the elastic compressible deformation; the strain and displacement fields of mode I are deeply affected by the elastic compressible deformation. However, the strain and displacement fields of mode II are less affected by the elastic compressible deformation. The asymptotic solutions of dynamic growing crack-tip field gained here can conveniently degenerate the incompressible case, when the Poisson ratio , named as HR field. The conclusions can provide the references for further studying the dynamic growing crack-tip field in compressible material.
Solving the Equivalent Function of Failure Mode Based on Multiple Correlation
Authors: Chen Wei Dong , Li Jian Cao , Yu Yan Chun
Published: September 2011

To solve the problem of equivalent functions of failure mode and low computational efficiency, the coefficient expression of equivalent functions has been derived based on equivalent principle. The concept of multiple correlation was introduced to the reliability analysis of failure mode , the correlation problem between several components and a component has been explained rationally. The display recursive expression of equivalent functions involved two-dimensional integral computation has been given. The high calculation accuracy and efficiency of solving recursive equivalent functions has been indicated according to numerical results.
Failure Conditions from Push-Out Tests of a Steel-Concrete Joint: Experimental Results
Authors: Helincks Peter , de Corte Wouter , Klusák Jan , Seitl Stanislav , Boel Veerle , de Schutter Geert
Published: September 2011

Steel-concrete joints can suffer from premature fail due to inadequate shear bond between the two surfaces. In this paper the shear bond strength between steel and self-compacting concrete (SCC) without mechanical shear connectors is evaluated through push-out tests. The test samples consist of two sandblasted steel plates (10 and 6 mm) and a concrete core, with connection between steel and concrete obtained by a 2-component epoxy resin, gritted with granulates. During the tests, the ultimate shear force is recorded as well as the slip between steel and concrete. All test members exhibited a concrete - adhesive failure, and indicate nominal shear bond stresses between 2.20 and 4.22 MPa. In addition, a substantial difference in measured shear bond stresses is found between the 6 and 10 mm steel plates, indicating unwanted secondary effects with the 6 mm plates. During testing, maximum slip values between 0.02 and 0.05 mm are recorded. In addition to the experimental tests, shear stress distribution in the epoxy – concrete interface is examined by finite element analysis (FEA). In this way, a non-uniform stress distribution between steel and concrete is found with the maximum shear value about 2.5 times higher than the nominal shear stress value. The FEA combined with the experimental results provide a reasonable understanding of the shear induced failure conditions at a steel-concrete joint, and create test data for a fracture mechanics approach.
Load-Rate Sensitivity in 1D Non-Linear Viscoelastic Model
Authors: Kožar Ivica , Ožbolt Joško , Pecak Tatjana
Published: September 2011

Load-rate sensitivity of material is important in impact and other dynamic loadings. It is assumed that the strain-rate sensitivity is not a material property but comes out naturally from dynamic equilibrium equations. Material is assumed non-linear, similar as used in the microplane model for quasi-brittle materials, and viscoelastic arranged into Kelvin scheme. The scheme is the simplest possible and consists of two Kelvin bars in series with an optional mass between them (Maxwell bars are considered in our previous paper). Loading is uniaxial tension with changing intensity in time, asymptotic or harmonic. The resulting differential equation (equations when a mass is present) is non-linear and stiff. Equations have been solved numerically using adaptive and Radau integration. For equal parameters nonsymmetrical (together with symmetrical) results could be obtained, meaning localization is possible without the localization initiator. System response is strongly influenced with the presence of a mass. Phase diagram show that some combination of parameters and loading demonstrate chaotic behavior.
Effect of Tensile Dwell on Low Cycle Fatigue of Cast Superalloy Inconel 792-5A at 800°C
Authors: Šmíd Miroslav , Obrtlík Karel , Petrenec Martin , Polák Jaroslav
Published: September 2011

Effect of tensile dwell on low cycle fatigue of cast Inconel 792-5A is studied in symmetrical strain cycling at 800°C. Cyclic hardening/softening curves, cyclic stress-strain curves (CSSC) and fatigue life curves were obtained in continuous cycling and in cycling with tensile dwells. Dwells have slight effect on hardening/softening curves at high strain amplitudes. CSSC in cycling with dwells is shifted to lower stress amplitudes. No significant effect of dwells on Basquin curves is observed. Density of slip markings in continuous cycling is significantly higher in comparison with cycling with dwells. Samples cycled with dwells are typical of high density of secondary cracks, although sporadic slip markings were also found.
Assessment of Existing Concrete Buildings
Authors: Nobile Lucio , Bonagura Mario , Bartolomeo Veronica
Published: September 2011

Assessment of concrete strength in existing structures is a very fundamental task today, because the mechanical characteristics are strictly connected to seismic protection and performance estimation of the material. To this aim, several compression tests has been carried out on drilled core samples in conjunction with different NDT methods. The activity presented in the paper is still under development and is intended as a reference in the choice of the methods and correlations for structural survey of existing buildings.
A Three Dimensional Graphical Aid for Fatigue Data Analysis
Authors: Atzori Bruno , Meneghetti Giovanni , Ricotta Mauro
Published: September 2011

The fatigue behaviour of materials is usually synthesised in terms of stress-life (S-N) curve or in terms of strain-life (e-N) curve, the latter being described by the so-called Manson-Coffin equation. It is known that the assumption of equality of the plastic and elastic components between the Manson-Coffin and the stabilised stress-strain curves leads to the so-called compatibility conditions which connect the equations theoretically. The material constants of the Manson-Coffin and of the stabilised stress-strain curve are commonly determined by best fitting separately the experimental data obtained from strain-controlled fatigue tests. As a consequence the compatibility conditions may not be fulfilled. In this paper a method for fatigue data analysis that ensures the compatibility conditions is proposed and validated against experimental data.
Impact Detection Using Artificial Neural Networks
Authors: Ghajari M. , Sharif-Khodaei Z. , M.H.Aliabadi Ferri
Published: September 2011

In this work, a number of impacts on a composite stiffened panel fitted with piezoceramic sensors were simulated with the finite element (FE) method. During impacts, the contact force history and strains at the sensors were recorded. These data were used to train, validate and test two artificial neural networks (ANN) for the prediction of the impact position and the peak of the impact force. The performance of the network for location detection has been promising but the other network should be further improved to provide acceptable predictions about the peak force.
Influence of Drawing Straining Path on Hydrogen Damage of Prestressing Steel Wires
Authors: Toribio Jesús , Lorenzo Miguel , Vergara Diego
Published: September 2011

Residual stress and strain states, produced during cold drawing, play a key role in hydrogen embrittlement (HE) of prestressing steel wires, because of hydrogen accumulation in certain places of the material is affected by stress and strains fields. Taking into account that the drawing straining path directly affects both residual stress and plastic strain distribution, the aim of the present paper is to clarify the influence of drawing straining path in the residual state and, consequently, its influence on the HE process of prestressing steel wires.
Meshless Local Integral Equation Method with Analytical Formulation and its Application to Computational Fracture Mechanics
Authors: Wen Pi Hua , M.H.Aliabadi Ferri
Published: September 2011

In this paper, the exact forms of integrals in the meshless local boundary integral equation method are presented and applications were demonstrated for fracture mechanics. A weak form for a set of governing equations with a unit test function or polynomial test functions is transformed into local integral equations. Each node has its own support domain and is surrounded by a local integral domain with different shapes of boundaries. The meshless approximation based on the Radial Basis Function (RBF) is employed for the implementation of displacements. For cracked plate, opening displacement on the crack surface can be obtained with satisfactory accuracy without special treatment for stresses singularities at crack tip.
Experimental Study to Verify the Fatigue Limit Found by Thermal Analysis of Specimen Surface in Mono Axial Traction Test
Authors: Risitano Giacomo , Clienti Carmelo
Published: September 2011

Following the first experimental results concerning the possibility to estimate the fatigue limit by semi-static tensile traction test, the authors are continuing the experimental thermo-analysis of the curve zone between the origin and the yield stress; that is rich of indication about the fatigue failure process. The tests carried out on the AISI 304 steel by thermal analysis, confirmed the good approximation between the values of the fatigue limit estimated by fatigue test and by the quasi-static test. The results shoed the importance of the thermo-analysis of the part of the stress-strain curve (distant from the yield point) where only in macroscopic terms the behavior is perfectly elastic.
Measurement of Deformation on Welding Specimen Using ESPI
Authors: Kim Kyeong Suk , Kim Dong Soo , Kim Kyung Su , Kee Chang Doo , Kim Jin Won , Na Mang Yun
Published: September 2011

The residual stress was measured through the proposed method with ESPI measurement system. The proposed measurement method as a basic study combined with theory and experiments applied for residual stresses prediction and developments of safety estimation technique.
Dynamic Characteristics of Composite Materials Body for Bi-Modal Tram
Authors: Kim Yeon Su , Chang Se Ky , Moon Kyeong Ho , Mok Jai Kyun
Published: September 2011

The car body of the bi-modal tram has been designed and built to have low floor to provide the old and the handicapped with easy access considering Korean physical standard, passenger capacity (standee, seated, handicapped), and bus and urban railway regulations in Korea. The car body has been composed of composite materials (light-weight sandwich constructions) with glass epoxy skins, aluminum honeycomb cores and aluminum inner-frames. This paper was aimed to evaluate dynamic characteristics of the car body while the bi-modal tram was running in the test track. Based on the results from vibration accelerations measured on the floor level of centers of car bodies and axle, dynamic characteristics of the composite materials car body were discussed in this paper.
Crystallographic Analysis of Specimens Used for Calibrate a Failure Model for an Al 6061 – T6 Alloy
Authors: Giglio Marco , Manes Andrea , Mapelli Carlo , Mombelli Davide , Baldizzone Claudio , Gruttadauria Andrea
Published: September 2011

Calibration and exploitation of failure criterion is at present a challenging field in the structural integrity scenario. Calibrated failure criteria allow the simulation/reproduction of damages using virtual approach and eventually further assessment of the residual integrity of the components. Therefore the increase of awareness in failure issues makes the numerical simulation an actual, useful and reliable tool for the analysis of complex structures under extreme loads, especially in aerospace field where full scale tests are often very expensive and difficult to carry out. With this aim, the constitutive relations of an Aluminium Al 6061-T6 alloy have been calibrated with dedicated focus on failure criterion. The results obtained have been discussed considering the crystallographic measurements that permit to point out the dissipative behavior on the basis of texture formation as a function of the load type. The final aim is to confirm and explain the different failure behavior depending on the different stress triaxiality.
The Measurement of Residual Stresses in Thermal Barrier Coated Model Aerofoils
Authors: Liu Dong , Flewitt Peter E.J. , Hallam K.R.
Published: September 2011

In this paper, we explored the relationship between thermal aging and the residual stresses developed within a thermal barrier coating (TBC) and the underlying thermally grown oxide (TGO). Superalloy model specimens (CMSX4) with a curved geometry designed to simulate key features of turbine blades coated with air plasma sprayed (APS) 7 wt.% Y2O3-stabilised ZrO2 applied to an Amdry 995 bond coat were oxidised in the temperature range 900°C to 975°C for various lengths of time. Stress measurements on both the TBC and the underlying TGO were made at positions of known curvature using Raman and photo-stimulated piezo-luminescence spectroscopy (PLPS). The residual stress values reflect the interaction between TGO and TBC, which has the potential to be used as an indicator of service lifetime. The results are discussed with respect to the origin of the stress changes and the long term integrity of the coating.
Crack Growth Rates and Corrosion Fatigue of Austenitic Stainless Steels in High Chloride Solutions
Authors: Vichytil Clemens , Mori G. , Pippan Reinhard , Panzenböck M. , Fluch Rainer
Published: September 2011

Purpose: Applications for highly corrosive environments and cyclic loading are often made out of austenitic stainless steels. Corrosion fatigue and crack propagation behaviour has been studied to determine failure processes and damage mechanisms. Approach: CrNiMo stabilized austenitic stainless steel and CrMnN austenitic stainless steel in solution annealed and cold worked condition are compared. S/N curves and crack propagation rate curves are recorded in 43 wt% CaCl2 solution at 120 °C, which resembles most severe potential service conditions. For comparison these experiments are also performed in inert glycerine. Additionally, the electrochemical behaviour of these materials has been studied. Findings: The CrMnN steels have excellent mechanical properties but are very susceptible to stress corrosion cracking in the test solution. The fatigue limit as well as the threshold for long crack growth are significantly reduced in corrosive environment. Moreover these steels exhibit a remarkable increase in the propagation rate, which is extremely pronounced in the near threshold region. This effect is enhanced by cold working. CrNiMo steels also show a reduction in the fatigue limit, but it is less pronounced compared to CrMnN steels. The threshold is significantly reduced in corrosive environment, but propagation rate is lower in corrosive environment compared to inert glycerine. Possible explanations of this surprising behaviour are discussed.
The Influence of the KHß Factor Determination Method  on the Evaluation of the Gear Tooth Surface Durability and Bending Strength
Authors: Krawiec Stanisław
Published: September 2011

The references concerning the strength analysis of gears include a few methods of calculating the value of the face load factor (KHβ). In the paper, discussed are the C2 ISO method [1, 2, 3] and a method presented in [4, 5]. The two methods differ mainly in the way the bending and torsional deformations in the shafts and gears are calculated. On the example of the calculations of the first stage in a two-stage helical gear presented schematically in Fig.1, the influence of the these two different approaches on the value of the safety factors for pitting (SH) and tooth breakage (SF) has been analysed. The influence of four accuracy classes used in the manufacture of gearing (5, 6, 7 and 8) on the value of the safety factors SHand SF has also been evaluated.
Methods of Increasing Loadability for the Plastic Cycloidal Gears
Authors: Biernacki Krzysztof
Published: September 2011

The working unit of the hydraulic gerotor machine consists in cycloidal gears. In the paper, ways of increasing the load limit for the plastic cycloidal gears have been presented . The objective has been achieved by means of structural and material methods. The modifications have been introduced on the basis of the theoretical analysis of stress and deformation that are generated in the cycloidals gears while in operation. The analysis has been carried out with the use of the finite elements method. The outcome of the analysis is determination of the maximum working pressure value at which the hydraulic gerotor machines featuring the plastic cycloidal gears can operate.
Radial Stiffness of Thrust Ball Bearings
Authors: Raczyński Andrzej , Kaczor Jaroslaw
Published: September 2011

The paper presents the unusual question of determining the dependency between the radial strength applied to the thrust ball bearing against the radial displacement of one ring to another. Contrary to appearances, the shift may occur in a standard bearing system and consequently it may lead to its premature wear and tear. The article depicts a method of determining this dependency (called ‘radial stiffness’) and shows the examples of calculation results obtained through a special computer program.
Simulation of Hot Extrusion of an Aluminum Alloy with Modeling of Microstructure
Authors: Ockewitz A. , Sun D.Z. , Andrieux F. , Müller Sören
Published: September 2011

In this work a numerical method for the simulation of extrusion processes with modeling of microstructure is presented. Extensive testing was done to provide a basis for the verification of simulation results. Circular rods of AA6005A were extruded by backward and forward extrusion with different extrusion ratios, billet temperatures and product velocities. The extruded rods were cooled either by water or at air to distinguish between dynamic and static recrystallization. Temperature and strain-rate dependent yield stresses were determined from hot compression tests. Special friction tests on cylindrical specimens under high hydrostatic stresses at high temperatures have been performed and the parameters of a friction model were identified from the experiments. The recrystallized volume fraction and grain sizes in the extruded rods were analyzed by means of optical micrographs. The obtained results were used to determine the parameters of a recrystallization model which was implemented in the FE code HyperXtrude. The transferability of the numerical model was checked by simulating forward extrusion tests using the model parameters obtained from backward extrusion tests.
Surface Quality Prediction in Aluminum Extrusion
Authors: de Rooij Matthijn , Ma X. , den Bakker A.J. , Werkhoven Robert J.
Published: September 2011

The surface quality of aluminium extrusion products can be hampered by undesired surface features like die lines and pickups. In particular the presence of pickups is considered as undesirable. Surface pickups appear as intermittent torn marks on the aluminium extrusion products, often terminated with a protruding lump rising above the surface up to hundreds of microns in height. Using a model calculating initiation, growth as well as detachment of the lumps on the die bearing surface, the surface quality of aluminium extrusion products can be predicted. The results of the model can be presented in terms of surface quality diagrams, where contour lines of the (normalized) calculated number of lumps are presented in terms of exit speed and extrudate surface temperature. These diagrams are unique for a certain combination of geometry of the extrudate and the aluminium alloy and can be used to optimise process conditions with respect to surface quality within a certain process window. In order to validate the model, the size and number of pickups on the surface of a labscale extruded strip of AA6063 have been measured. The results of the model are being compared to the experiments and show good agreement.
Processing of Wrought Magnesium Alloys to Produce Small Tubes for Biomedical Applications: Investigation about the Extrusion Process by a Laboratory Test Rig
Authors: Ge Qiang , Vedani Maurizio
Published: September 2011

Two commercial ZM21 and AZ31B alloys were extruded into small-size tubes at 410°C and strain rate 2.78·10-3 s-1 by a laboratory hot-extrusion system. The series of tubes, with outer diameter in the range of 8-4 mm and inner diameter from 6 to 3 mm were investigated considering microstructure and texture analysis. The tubes featured a homogeneous and refined equiaxed grain structure since dynamic recrystallization was clearly observed during the extrusion process. A typical ‘basal’ type texture was detected in extruded tubes by using EBSD technique.
The Process of Co-Extrusion – An Analysis
Authors: Kittner Kai , Awiszus Birgit
Published: September 2011

This paper provides an analysis of a co-extrusion process. The compound consists of the sleeve material, aluminum, and the core material, magnesium. It is imperative to produce impeccable compounds without cracks in the interface. Therefore, a simple indicating value for damaging effects during the process is necessary. In the numerical simulation the compound quality is noticeable by the current macro mechanical criterion of axial strain difference. A statistical analysis verifies this criterion as an adequate quality criterion. By means of this criterion it is possible to define a stable process window for the co-extrusion process.
Microstructure Characteristics of the Black-Glazed Shreds Excavated from the Qingliangsi Kiln
Authors: Liu Zi Wei , Zhang Zhi Gang , Li Hua , Wu Wei , Hua Jia Jie , Cheng Guo Feng , Lin Chu Cheng
Published: September 2011

The black-glazed shreds from Qingliangsi kiln were studied. The glaze and body micro- structures, compositions and crystal phases were observed and analyzed by field emission scanning electron, microscope multiple functions electron probe-energy spectrum instrument and ﬁeld emission transmission electron microscope. The iron oxide crystal in oil spot was mainly the ε-Fe2O3 in the orientation of the zone axis [001], and also few content of ε-Fe2O3 in the orientation of the zone axis [412]. The brown oil spots on the glaze surface were aggregations of a great deal of iron oxide hematite crystals. Bodies of black-glazed shreds have high Al2O3(26.47 % ~ 30.48%) and low SiO2 (62.77% ~ 66.20%), which pertained to the typical recipe of north porcelain bodies. The glaze are attributed to calcium-alkali glaze, and according to the ratio of Al2O3:SiO2, it belongs to the crystallization glaze.
Relationship between the Conductivity of Supernatant of 3Y-TZP Powder and Sintering Properties of its Ceramics
Authors: Wu Xiao Bo , Sun Da Zhi , Jiang Dan Yu , Xu Hai Fang , Huang De Xing , Xu Bing
Published: September 2011

The influence of conductivity of supernatant of 3Y-TZP powder on the sintering properties of its ceramics is evaluated. It is found that the conductivity of supernatant is helpful for the determination of the sintering activities. The sintering properties of 3Y-TZP ceramics are improved with the increase of the conductivity of supernatant. It is attributed to a large amount of unsaturated states in the powder.
Densification Mechanism of the Low Temperature Co-Fired Glass-Ceramic Substrate
Authors: He Qing , Geng Zhi Ting
Published: September 2011

In this paper, application of multilayered circuit substrates has been studied, the glass ceramic (50%Al2O3-50%glass) with low temperature co-fired and good performance as the raw material was used, by means of calculating the apparent activation energy of densification in the experiment and observing the SEM images of glass ceramic substrate section, the densification mechanism of glass ceramic substrate sintering is analyzed.
Estimate of Thermodynamic Indirect Measurement on the Electrocaloric Effect
Authors: Ding Kai , Bai Yang , Han Xi , Zhang Wen Jie , Qiao Li Jie
Published: September 2011

The thermodynamics indirect measurement based on Maxwell relation is one of the most popular methods for the studies on electrocaloric effect of ferroelectric material, including bulk ceramics, single crystals and thin films.However,recent reports indicated that the results obtained through this method did not agree with those from the direct measurements in many cases, such as nearTcor under high electric field. This paper discussed the applicability of thermodynamics indirect measurement and analyzed the reason why its calculated result may be different from the true value of electrocaloric effect. Because the thermodynamics indirect characterization depends on the measurement of polarization at different temperatures, the testing frequency ofP-Eloops, leakage current of sample and temperature resolution of measurement play the important roles in the accuracy measurement of electrocaloric effect.
The Influence of Specimen Grips on the Measurement of Micro-Tensile Bond Strength to Human Dentin
Authors: Zhao Xin Yi , Li Shi Bao , Gong Xu
Published: September 2011

To evaluate the effects of specimen grips on the measurement of the micro-tensile bond strength (mTBS) to dentin. Methods: Twelve extracted human molars were sectioned to expose mid-coronal dentin. Each surface was ground with 600-grit SiC paper. Four adhesives: Prime & Bond NT (Dentsply, USA), Contex (DMG, German), Adper Prompt (3M/ESPE, USA) and Clearfil S3Bond (Kuraray, Japan) were applied to the polished surfaces followed by creation of composite buildups. After 24 hr storage in 37°C water, the teeth were sectioned perpendicular to the adhesive interface to produce multiple beams of composite-bonded dentin, approximately 0.8 mm2in cross-sectioned area. Half of the specimens were attached to testing grips A which did not contain positioning pins and another half were attached to the testing grips B which contained positioning pins. All specimens were tested using a universal testing machine at a crosshead speed of 1.0 mm/min. Results: Specimens tested using the grips A presented lower mTBS than using the grips B (P<0.01). Many specimens tested using the grips A showed mix failure or cohesive failure within composite, and most of the failures were adhesive for specimens tested using the grips A. Conclusion: Specimen grips without positioning pins cannot accurately present mTBS and the grips with positioning pins can more accurately present mTBS.
Preparation and Characterization of Lead-Free Na0.54K0.42Li0.04NbO3 Nano-Powders by Sol-Gel Method
Authors: Gao Guang Zhi , Liu Yan Gai , Huang Zhao Hui , Fang Ming Hao
Published: September 2011

In this paper, Na0.54K0.42Li0.4NbO3 nano-powders were prepared by the sol-gel method, Na2CO3, K2CO3, Li2CO3and Nb2O5as raw materials, citric acid as coordination agent, ethylene glycol as esterifying agent, polyethylene glycol as dispersing agent. From the XRD, TG-DTA and TEM analysis, powders’ size, lattice constants and surface topography were studied. The results showed that under the condition of 600°C × 2h, nano-powders showed good dispersiveness and no reuniting, with pure orthorhombic perovskite structure and various grain sizes was 40.78 nm.
Synthesis and Electromagnetic Properties of Hollow Ceramic Microspheres
Authors: Xu Bao Cai , Wang Jian Jiang , Duan Rong Xia , Huo Xing Jian
Published: September 2011

The hollow ceramic microspheres were prepared by Self-reactive flame spraying method. The structural characteristics and morphology properties of the composite powders were obtained by XRD and SEM. The results show that the obtained particles are hollow ceramic microspheres. The average particle size is about 30μm. An analytical method for the determination of electromagnetic parameters (ε, μ) of materials under test is presented by the analysis of normalized general matrix of equivalent network of coaxial line filled with samples. The analysis of vector network analyzer show that reflectance of hollow composite microspheres could well absorb microwaves in 2-18 GHz. The reflection loss is less than -l0dB in the range of 12.4 to15.2GHz while the minimum reflection loss is -18.5dB at 13.6GHz.
Design and Calculation of Magnetic Liquid Seal with Rectangular Pole Teeth
Authors: Yang Xiao Long , Li De Cai , Yang Weng Ming , Xing Fei Fei
Published: September 2011

The principle of magnetic liquid seal with rectangular pole teeth structure is discussed in this paper, and the magnetic circuit design process of magnetic liquid seal with rectangular pole teeth structure is systematically discussed. Using the formula of pressure capability of magnetic liquid seal with rectangular pole teeth structure and equivalent magnetic circuit, the magnetic circuit of magnetic liquid seal with rectangular pole teeth structure was designed and calculated in detail according to the kirchhoff's law of the magnetic circuit. The design method of magnetic circuit in magnetic liquid seal with rectangular pole teeth structure proposed in this paper has important reference value to the design of magnetic liquid sealing device.
Characteristics of TiO2 Nanotube Arrays on Titanium Prepared by Anodization
Authors: Li Dan , Ning Cheng Yun , Tan Guo Xin , Zheng Hua De , Ge Yong Mei
Published: September 2011

Titania nanotube (NT) arrays with a length of 550nm were fabricated on the flat titanium substrate by anodization. The microstructure was identified by scanning electron microscope. The composition has been investigated with X-ray photoelectron microscopy. It also showed that, as compared with the flat surface, the density of Ti-OH groups on the NT surface has been increased. However, according to the contact angle goniometer, the hydrophilicity of the NT surface becomes worse than that of the flat surface. In addition, surface roughness was investigated by non-contact atomic force microscope. It demonstrated that the nano-roughness of NT arrays has been increased. More important is the relationship between contact angle and roughness factor have been analyzed based on the modified Young’s equation. These results indicate that the anodized NT structures may have provided an optimal surface roughness for promoting the bioactivity.
Discharge Relaxation of TiO2-WO3 Composite Nanotube Arrays
Authors: Zhuo Yu Qing , Ling Yun Han , Huang Liang
Published: September 2011

Smooth and aligned TiO2-WO3composite nanotube arrays (TiW-NTA) were successfully fabricated on a Ti-W alloy via an anodization process. The crystal phase and surface morphology of the nanostructured film were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The photoelectrochemical properties of the as-prepared samples were studied by measurement of the photocurrent response and open-circuit potential. The TiO2-WO3nanotube arrays were found to be capable of a more than 2.5h discharge relaxation due to its energy storage behavior.