bluuebunny/crossref_metadata_2025 huggingface dataset:
Cr-N Strain-Gauge-Type Precision Displacement Sensor for Measuring Positions of Micro Stage
Authors: Azuma Toyohiro , Niwa Eiji , Peng Yu Xin , Kaneko Junji , Shimizu Yuki , Ito So , Gao Wei
Published: November 2012

A strain-gauge-type precision displacement sensor, which is developed for a usage of micro-XY stage, is described in this paper. A thin-film strain-gauge element, which is made by Cr-N alloy, is directly fabricated on the base of the strain gauge. The direct fabrication and using the Cr-N element are expected to achieve higher sensitivity for displacement detection and better stability against the change of ambient temperature. In this study, several designs of the thin-film strain gauge, including both of two-gauge-type and four-gauge-type, are prepared to compare sensor performances such as sensitivity, stability and so on. The designed patterns of the strain-gauge element are directly fabricated on zirconia plates by using photolithography processes. The fabricated strain gauges are then evaluated as precision displacement sensors. At first, stability of the fabricated Cr-N strain-gauge-type displacement sensor was confirmed by comparing with the one made by a conventional strain gauge. Resolution of the fabricated Cr-N strain-gauge-type displacement sensors was then evaluated by comparing with a commercially-available laser displacement sensor, while giving sub-micrometer-order deformation to the strain-gauge-type displacement sensor. Details of the design, fabrication and evaluation results of the Cr-N strain-gauge-type displacement sensor are described.
Improvement of an Air-Bearing Displacement Sensor with Nanometric Resolution
Authors: Ito So , Lee Kang Won , Shimizu Yuki , Gao Wei
Published: November 2012

A contact stylus-type displacement sensor is proposed for a surface form measurement of micro-structures. The stylus is supported by an air-bearing, thus it can be moved smoothly without friction between the stylus and the air-bearing. In order to reduce the measurement force, a novel controlling technique of a contact force has been developed. During the measurement one edge of the stylus is maintained contact with the measured surface by its own weight. Another end of the stylus is connected with a counter weight by a string and the stylus is hanging on the string in order to reduce the contact force between the edge of the stylus and the measured surface. Measuring force is estimated to confirm the effectiveness of the counter weight. Surface measurement of a steel ball is carried out using the developed air-bearing displacement sensor.
Effect of Discharge Condition on Cavitations Behavior by Single Pulse Discharge
Authors: Akematsu Yoshiaki , Kageyama Kazuro , Mohri Naotake , Murayama Hideaki
Published: November 2012

This paper describes some experimental results on a fundamental phenomenon of the single pulse discharge. In electrical discharge machining (EDM), processing accuracy was effected by behaviors of fused material. Pressure was important for removing fused material. So, it was needed to clarify that the mechanism of pressure occurrence by electrical discharge. In this study, it was investigated that effect of discharge condition on cavitations behavior by single pulse discharge. Gap region medium viscosity was changed by medium and temperature. Electrical discharge current was changed by applied voltage. The optical fiber vibration sensor is located on an aluminum work-piece (cathode) plate. Pressure was measured by optical fiber sensor during single pulse discharge. As the results, burst acoustic emission (AE) wave was occurred during single pulse discharge. The occurrence of several times burst AE wave was caused by cavitations behavior. The condition on which bubble does not collapse has become apparent. It was found that cavitations behavior was mainly depended on discharge current except for the condition on which bubble does not collapse.
Buckling Reliability Analysis for the Cylindrical Shell with Initial Defects
Authors: An Hai , An Wei Guang , Gao Yuan Yin , Song Xiang Hua
Published: November 2012

in this paper, the asymptotic expression of the buckling critical load coefficient of the thin cylindrical shell with local axial symmetry initial defects under the axial loads is deduced by used the Karman-Donnel Equation. The buckling safety margin equation of the cylindrical shell with initial defects is constructed. Furthermore, the buckling reliability index is solved by used AFOSM (Advanced First-Order Second Moment) method. In the end, a numerical example is given to analyze the influence of the band width and amplitude of local axial symmetry initial defects on the structural buckling reliability index.
Repair and Service Safety Evaluation of a Fire Damaged Concrete Bridge
Authors: Wang Chun Sheng , Liu Lu Ping , Wei Mao Sen
Published: November 2012

The Yao Zhou downlink Viaduct damaged in a fire accident was repaired using steel plate and concrete composite strengthening (SPCCS) technique. After strengthening and servicing normally for 1.5 years, two loading tests, meanwhile, a three-day traffic information observation and dynamic strain monitoring were carried out. The static loading test and monitoring results all showed that the Yao Zhou downlink Viaduct had good service condition since reinforcement, which satisfying the safety requirement. In order to evaluate the effectiveness of the SPCCS technique in-depth, structural behaviour under the ultimate limit state (ULS) and the serviceability limit state (SLS) were analyzed. The SLS and ULC of the key sections before and after reinforcement were calculated using the simplified formula and the finite element models calibrated by filed test results. The post-evaluation results showed that the behaviour of the spans damaged in fire accident could be improved obviously under the SLS using SPCCS technique, as well as the bridge stiffness enlarged than the original bridge structure. The ultimate bearing capacity (UBC) of the key sections was improved about 75% using SPCCS technique, which was two times as the most disadvantageous load effect combinations. Whats more, the fatigue life of fire damaged box girders strengthened using SPCCS technique was evaluated based on monitoring strain data, and the further bridge maintenance suggestions were proposed based on the assessment results.
Experimental Investigation of the Influence of the Bond Conditions on the Shear Bond Strength between Steel and Self-Compacting Concrete Using Push-Out Tests
Authors: Helincks Peter , de Corte Wouter , Klusák Jan , Boel Veerle , de Schutter Geert
Published: November 2012

Steel-concrete joints are often provided with welded shear studs. However, stress concentrations are induced in the structure due to the welding. Moreover, a reduction in toughness and ductility of the steel and a decreased fatigue endurance of the construction is observed. In this paper the shear bond strength between steel and ultra-high performance concrete (UHPC) without mechanical shear connectors is evaluated through push-out tests. The test samples consist of two sandblasted steel plates with a thickness of 10 mm and a concrete core. The connection between steel and concrete is obtained by a 2-component epoxy resin. Test samples with a smooth adhesive layer are compared with those with an epoxy layer, which is applied with a toothed paddle and/or gritted with small aggregates. In this research, specimens prepared with river gravel, crushed stone, and steel grit are compared and also two different epoxy resins are used. During the tests, the ultimate shear force is recorded as well as the slip between steel and concrete. All test specimens exhibited a concrete-adhesive or concrete failure. Furthermore, test results show that the use of a more fluid epoxy resin improves the anchorage of the gritted aggregates in the adhesive layer, resulting in higher shear bond stresses. No significant difference is found between specimens, gritted with river gravel or crushed stone. Applying the adhesive layer with the toothed paddle in horizontal direction slightly improves the bond behaviour. Finally, the experimental results of the test members with a smooth epoxy layer without gritted aggregates, provide test data for a fracture mechanics approach, which uses a 2D numerical model of the test specimen, composed of steel, epoxy resin, and concrete.
Experimental Study of the Influence of the Initial Notch Length in Cubical Concrete Wedge-Splitting Test Specimens
Authors: Korte Sara , Boel Veerle , de Corte Wouter , de Schutter Geert , Seitl Stanislav
Published: November 2012

The wedge-splitting test (WST) is a frequently used test configuration for performing stable crack fracture experiments on concrete specimens, thus allowing to determine the fracture process and crack propagation in the heterogeneous material. However, there are no standard rules regarding the wedge-splitting specimens geometry, groove dimensions or notch length. This paper concentrates on the influence of the initial notch length in geometrically identical, cubical specimens, cast from vibrated concrete. The experimental results of nine WSTs under monotonic loading, including Fsp-CMOD curves - splitting force versus crack mouth opening displacement - and fracture energy Gf, are presented. An important effect of the starting notch length on the fracture properties is observed.
Nondestructive Evaluation of Polyurethane Materials Using Transient Thermography
Authors: Amarandei Mihaela , Berdich Karla , Szigyarto Izabella , Kun Lorand , Marşavina Liviu
Published: November 2012

The aim of this work is to investigate the potential of transient thermography in the nondestructive evaluation of structural defects of NECURON 1001 using the FLIR thermographic system. Necuron is a polyurethane material used for applications like: fixture and gauges, master and copy models, models with high mechanical stress, etc. Transient thermography is a thermographic method which implies the investigation of materials that are of a different (often higher) temperature than the ambient. The heat flow into the sample is altered in the presence of a subsurface defect or feature, creating a temperature contrast at the surface that is recorded by the infrared system. Results show that this method of evaluation can indicate, in necuron, defects of small sizes that can be overlooked in the manufacturing process. Also, it was shown that the transient thermography method presented can be an important tool in evaluating structural defects of materials.
Fracture Toughness of PIR Foams Produced from Renewable Resources
Authors: Andersons Janis , Spārniņš E. , Cabulis Ugis , Stirna U.
Published: November 2012

Rigid low-density closed-cell polyisocyanurate (PIR) foams are used primarily as a thermal insulation material. Traditionally, they are manufactured from constituents produced by petrochemical industry. Introducing renewable materials in PIR formulation brings definite economical and environmental benefits. Fracture toughness of PIR foams obtained from renewable resources (with the polyol system comprising up to 80% of rapeseed oil esters) and petrochemical PIR foams has been characterized experimentally, by compact tension tests, for mode I crack propagation along the rise direction of the foams.
Scattering of Anti-Plane SH-Wave by Multiple Cylindrical Inclusions in Elastic Semi-Space
Authors: Li Hong Liang , Yang Yong
Published: November 2012

Multiple circular inclusions exists widely in natural media, engineering materials and modern municipal construction. The scattering field produced by multiple circular inclusions determines the dynamic stress concentration factor around the circular inclusions, and therefore determines whether the material is damaged or not. These problems are complicated, because there are many factors influenced. Researchers solved these problems by analysis and numerical methods. It is hard to obtain analytic solutions except for several simple conditions. In this paper, the solution of displacement field for elastic semi-space with multiple cylindrical inclusions by anti-plane SH-wave is constructed. In complex plane, considering the symmetry of SH-wave scattering , the displacement field aroused by the anti-plane SH-wave and the scattering displacement field impacted by the cylindrical inclusions comprised of Fourier-Bessel series with undetermined coefficients which satisfies the stress-free condition on the ground surface are constructed. Through applying the method of multi-polar coordinate system, the equations with unknown coefficients can be obtained by using the displacement and stress condition around the edge of cylindrical inclusions. According to orthogonality condition for trigonometric function, these equations can be reduced to a series of algebraic equations. Then the value of the unknown coefficients can be obtained by solving these algebraic equations. The total wave displacement field is the superposition of the displacement field aroused by the anti-plane SH-wave and the scattering displacement field. By using the expressions, an example is provided to show the effect of the change of relative location of the cylindrical inclusions. Based on this solution, the problem of interaction of multiple cylindrical inclusions and a linear crack in semi-space can be investigated further.
Multiscale Simulation of the Size Effect of Nano-Indentation
Authors: Wang Zhen Qing , Meng Qing Hua , Yang Zeng Jie
Published: November 2012

In this paper, the size effect of copper, aluminum and silver nanoindentation has been studied by adopting the new multiscale method. According to the analysis and comparison of load-displacement cures for the three materials under the four specimens, the effects of various physical parameters on the dislocation nucleation have been discussed. For different specimen lengths, simulation results show the apparent size effect, especially in the initial elastic deformation stage, the difference of the curve slope is very obvious. Comparing these three kinds of metal materials of the load displacement curve, it can be found that the metal copper thin film and the metal aluminum thin film in the load process, only experience one time reduced the process, but the metallic silver thin film reveals a fluctuation.
Study on the Diffusion Coefficient in NGS under Low Tensile Stress
Authors: Qiao Ying Jie , Fu Hong Bo , Li Chun Kai
Published: November 2012

In this paper, the diffusion coefficient of vacancy-solute complex and diffusion coefficient of solute atoms, P, in non-equilibrium grain-boundary segregation under low tensile stress in steel 12Cr1MoV are calculated based on the model developed by Xu. Both the simulation and experimental kinetics curves are achieved. Results show that the calculated result with the kinetic equations perfectly fits with the experimental observations for phosphorus in steel 12Cr1MoV under low tensile stress. In the segregation process, the rate of phosphorus segregation is high due to a large diffusivity of the complex. In the de-segregation process, the level of phosphorus segregation decreases with increasing stress aging time. But the rate of phosphorus desegregation from grain boundaries to centre is slower compared with that in segregation for the diffusion coefficient of phosphorus atoms is far lower than the complexes.
Wear Failure Behavior of Steel Surface with Palygorskite Powders as Lubricant Additives
Authors: Wang Li Min , Xu Bing Shi , Xu Yi , Zhang Bo , Yu He Long , Li Qing Fen
Published: November 2012

Wear failure behavior of steel surface with palygorskite powders (Palys) as lubricant additives was investigated in this paper. Different content of Palys was added in different lubricating oils. The wear failure behavior of the steelsteel contact surfaces was studied by using an optimal SRV oscillating friction/wear tester. The elemental component and morphology on worn surface were analyzed by SEM and EDS. From the results of the friction/wear tests and analysis of the worn surfaces, we can see that specimens with Palys as lubricant additives exhibit excellent wear reducing properties and introduce a smooth and compact oxide layer on the worn surface. This may be attributed to the layer-chain fibrous crystal structure of palygorskite and the complex physicochemical nature in friction process.
Interaction of Elliptical Inclusion and Crack in Half-Space under SH-Waves
Authors: Yang Zai Lin , Xu Hua Nan , Hei Bao Ping , Yang Yong
Published: November 2012

The methods of Green's function, complex function and multi-polar coordinates are applied here to report interaction of an elliptical inclusion and a crack in half-space under incident SH-waves. Based on the symmetry of SH-waves scattering, the "conformal mapping" technology was developed to construct a suitable Green's function, a fundamental solution to the displacement field for the elastic half space containing elliptical inclusion while bearing out-plane line source load at arbitrary point, for creating a beeline crack with arbitrary length at any position combined with crack-division technology. The displacement field and stress field were then deduced while the inclusion coexists with the crack Lastly, numerical examples are presented to discuss the dependence of dynamic stress concentration factor (DSCF) around the elastic inclusion on different parameters.
Experimental Study on Residual Strength of Panels with Multiple Site Damage
Authors: Yan Xiao Zhong , Wang Sheng Nan , Wang Wen
Published: November 2012

The fatigue test of typical bolt-hole panels with five open holes in a line and the residual strength test of the panels with multiple site crack (MSD) were carried out. The crack initiation life of the test panels and the residual strength of the panels with different MSD crack sizes were obtained by the tests. The application of the net section yield criterion in the determination of residual strength of the panel containing multiple site damage was studied by comparing the calculated results with the test results. The conclusion is that the criterion meets the engineering accuracy requirement in the case of smaller MSD cracked area or smaller MSD crack sizes.
Damage Analysis of 2D Woven Composite Laminates Containing an Open-Hole under Tensile Loadings
Authors: Zhang Xiao Qiong , Guo Wei Guo , Kong De Shuan
Published: November 2012

In order to understand damage mechanism, the influences of lay-up construction of laminates and environgment on tension behavior of 2D woven composite laminates with an open-hole, which was manufactured by a new technology, uniaxial tension tests are performed in 3 different environments on 4 kinds of lay-up specimens, using a WE-50 electromechanical universal material testing machines. The fracture of specimens are analysed through micrographic observations. The result show that there is a large difference both in tensile strength and damage mechanism due to different kinds of lay-up specimens: 1) the tensile strength of specimens that only with ±45 degree laminated is much lower than other samples with different kinds of layup and its tensile stress-strain curves presents nonlinear; 2)The failure modes and damage mechanism determines the strength of specimens; 3)The change of environment had a certain effect on the mechanical behaviors of materials, in this paper, it will cause the tensile strength of speicmens decreasing.
A New Approach to Determine Dynamic Strength Model Parameters under Taylor Impact Test
Authors: Xu F. , Guo Wei Guo , Wang Q.J. , Zeng Zhi Yin
Published: November 2012

In this paper, to determine the dynamic strength model for steels, a new approach which does not rely on the Hopkinson bar test has been proposed. As the DH36 steel for example, using the results of Taylor impact test and the quasi-static compression test, the initial parameters of Johnson-Cook plastic strength model have been fitted out, then the initial strength parameters have been optimized using the optimization techniques of the sparse Taylor impact cylinder. It has been shown that the optimized results in numerical simulation are consistent with results of Taylor impact test, and the optimized Johnson-Cook model can also well describe flow stress curve fitted from the Hopkinson bar test.
The Simulation of Low-Velocity Impact on Composite Laminates with the Damage Model Based on Strain
Authors: Ma Chun Hao , Xu Fei
Published: November 2012

This paper proposed a composite damage model including the damage initiation and evolution based on strain to predict the composite intralaminar damage under impact loading. In the numerical simulation, the user material subroutine VUMAT and the cohesive-zone model are chosen to describe the composite damage model and the delamination of interfaces between different plies. ABAQUS software is used to simulate the low-velocity impact of different thickness composite laminates. It is found that the delamination shape and area, the contact force and the deflection of the impactor obtained by the numerically simulation agree well with the experimental results.
Numerical Analysis of Femoral Neck Angle Influence on Stress Distribution of Cemented Austin Moore Hip Prosthesis
Authors: Bogdan Lucian , Nes Cristian Sorin , Faur Nicolae , Amarandei Mihaela , Enkelhardt Angelica
Published: November 2012

This paper presents a finite element analysis regarding the stress distribution in a cemented Austin Moore type hip prosthesis. The 3-D model was obtained using a Roland PICZA 3-D laser scanner. The applied loads simulate the normal gait cycle. The prosthesis is made from stainless steel with a femoral head of 45mm diameter. The numerical analysis was performed using the ABAQUS code. The results showed that the stress level in the cement is sensitive to the femoral neck angle. Starting with a standard, 125° angle, and increasing the angle with up to 5°, the resulting stress can be reduced with more than 10%. The proposed angle increase produces a more uniform stress distribution in the cemented section, increasing the durability of the arthoplasty.
Extended Finite Element Method for Fracture Mechanics and Mesh Refinement Controlled by Density Function
Authors: Cen Yi
Published: November 2012

This paper discusses the combination of element enrichment by mesh refinement controlled by density function with the extended finite element method and its application in fracture mechanics. Extended finite element method (XFEM) is an effective numerical method for solving discontinuity problems in the finite element work frame. A numerical example of fracture mechanics is analyzed at the end of this paper to show the application of the above method.
Stress-Strain Analysis of Composite Propellant under Cyclic Temperature Loads
Authors: Zhang Chun Long , Ding Biao , Ai Chang Sheng , Huang Feng
Published: November 2012

Based on integral nonlinear viscoelastic constitutive relationship, stress-strain field was analyzed of composite propellant under cyclic temperature loads to ensure the stress-strain distribution and damageable locality. The simulation conditions were designed in the temperature range from-10 to 60 at three different rate-temperature. The results indicate that the stress and strain have the same trend of changing. Adhesive interphase is prone to failure because of the alternating stress.
Advanced Natural Stitched Composite Materials in Skin-Stiffener of Wind Turbine Blade Structures
Authors: Papadopoulos F. , Aiyappa D. , Shapriya R. , Sotirchos E. , Ghasemnejad H. , Benhadj-Djilali R.
Published: November 2012

In this paper the failure behaviour of natural stitched composite materials in the skin-stiffener of wind turbine blade structures are investigated. For this study, the laminated composite beams were stitched using Flax yarns before curing process. Two stiffener structures of T-beam and Box-beam are studied in this paper. These specimens were tested under quasi-static loading condition to compare the failure resistance of adhesive and stitched bonding methods. Furthermore, the cohesive zone modelling (CZM) which is known as a variation in the cohesive stresses with the interfacial opening displacement along the localised fracture process zone is used to predict bonding failure in the skin-stiffener of wind turbine blade structures.
High-Temperature Structural Analysis on the Small-Scale PHE Prototype
Authors: Song Kee Nam
Published: November 2012

PHE (Process Heat Exchanger) is a key component for transferring the high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for massive production of hydrogen. Korea Atomic Energy Research Institute has established a small-scale nitrogen gas loop for the performance test on VHTR components and has manufactured a small-scale PHE prototype made of Hastelloy-X of high-temperature alloy. A performance test on the PHE prototype is underway in the gas loop. In this study, in order to evaluate the high-temperature structural integrity of the PHE prototype under the test condition of the gas loop, structural analysis on the PHE prototype was carried out to gauge the stiffness of pipelines connected to the PHE prototype in the gas loop.
Diagnosis of Damage in a Steel Tank Model by Shaking Table Harmonic Tests
Authors: Burkacki Daniel , Jankowski Robert
Published: November 2012

Diagnosis of damage in civil engineering structures has recently become an important issue in the safety assessment procedure. Among a number of different approaches, a method of measuring the changes in natural frequencies is one of the most effective indicators of global damage. It has been successfully applied to relatively small structures, however, the tests on large structures are very difficult and the practical application of the method still requires further investigations. The aim of the present paper is to show the results of the shaking table experimental study concerning the diagnosis of damage in a model of cylindrical steel tank with self-supported roof which is filled with liquid. During the tests, the base of the structure was excited under the harmonic loading with variable frequency. The tests were repeated for different stages of damage, which was introduced in the model by easing the bolts of structural supports as well as by cutting the welds between the shell and roof as well as between roof elements. The results of the study show a characteristic decrease in the natural frequencies for the case of structural supports with reduced stiffness (global type of damage). On the other hand, cutting the welds (local type of damage) has lead to the considerable increase in the power spectral density values for higher vibration modes.
Crack Modelling Using the Material Point Method and a Strong Discontinuity Approach
Authors: Guiamatsia Irene , Nguyen Giang D.
Published: November 2012

Modern numerical techniques utilised to model crack propagation tend to be optimized for tracking the evolution of a single crack. Real fracture processes are however complex, involving the initiation and propagation of opening (activated) cracks, while other may close (deactivate) and undergo frictional dissipations. Accounting for the correct loss of energy (through debonding and friction) is essential to achieving a realistic description of the fracture process. One common strategy has been to make small adaptations to traditional techniques to tackle multiple cracking, in effect relying on extensive complicated computational algorithms. A typical example is the use of cohesive models in combination with the eXtended finite Element method where cracks, sometimes intersecting, need to be defined explicitly. In this study the Material Point Method is used for the analysis of fracture propagation. Crack states, as internal variables, are stored within the material points and mapped as strong discontinuities to the elements during the Lagrangian phase of the solution. Consequently, material points carrying cracks of different sizes and orientations are allowed to cohabit within the same element, yielding a natural description of the fracture/fragmentation process. The three-point bending test is used to demonstrate the features of the new approach.
Deterministic and Probabilistic Earthquake Scenarios for the Seismic Risk Analysis of URM Buildings
Authors: Avila-Haro Jorge Arturo , González-Drigo Jose Ramon , Vargas Yeudy Felipe , Pujades L.G. , Barbat A.H.
Published: November 2012

Barcelona, as well as a large number of cities in the Mediterranean basin, has a housing stock composed of a large number of unreinforced brick masonry buildings. Motivated by different factors, the enlargement of the city (Eixample in Catalan) was held from the second half of the 19th century and the beginning of the 20th, a period in which a large number of buildings of this type were built, many of which are still used as dwellings. Although the buildings were built individually, some of them are linked to adjacent buildings by the side walls. This feature leads to the analysis of the buildings as isolated structures and also as an aggregate. Barcelona is located in a seismic region of low to moderate hazard, with macroseismic intensity between the grades VI and VII of the European macroseismic scale EMS'98. Based on the deterministic and probabilistic response spectra for the different types of soils present in Barcelona obtained in the work of Irizarry (2004), the seismic risk of four individual buildings and an aggregate is evaluated. The buildings are modeled and analyzed using the TREMURI program and MATLAB routines under the guidance of RISK-UE project.
Dynamic Crack Problems Using Meshless Method
Authors: Wen Pi Hua , Aliabadi M.H.
Published: November 2012

A Meshless Approximation Based on the Radial Basis Function (RBF) Is Developed for Analysis of Dynamic Crack Problems. A Weak Form for a Set of Governing Equations with a Unit Test Function Is Transformed into Local Integral Equations. A Completed Set of Closed Forms of the Local Boundary Integrals Are Obtained. as the Closed Forms of the Local Boundary Integrals Are Obtained, there Are No any Domain or Boundary Integrals to Be Calculated Numerically in this Approach.
The Influence of the Epoxy Interlayer on the Assessment of Failure Conditions of Push-Out Test Specimens
Authors: Klusák Jan , Helincks Peter , Seitl Stanislav , de Corte Wouter , Boel Veerle , de Schutter Geert
Published: November 2012

Connection between steel and concrete parts is frequently required in constructions where the steel-concrete joints are often realized by welded shear studs. In order to avoid stress concentrations, corrosion proneness, and other negative consequences of the welding process, steel-concrete connection without welded mechanical shear connectors is sought nowadays.
Connection can be realized via an epoxy adhesive layer and gritted with granules. In the paper, the assessment of the push-out test configuration was performed from the generalized fracture mechanics point of view. The numerical-analytical modelling of a steel-concrete connection is performed without and with the epoxy interlayer, while 2D and 3D modelling is used. Thus conditions of crack initiation can be predicted from knowledge of the standard mechanical and fracture-mechanics properties of particular materials. The model of a bi-material notch with various geometry, and material properties is used to simulate various singular stress concentrators that can be responsible for failure initiation. Various manners of preparation of the epoxy interlayer are tested experimentally. Results of the fracture-mechanics studies are compared with each other and with experimental results. On the basis of the comparison, the 2D simulation of the steel-concrete connection without the epoxy interlayer is shown to be suitable for the estimation of failure conditions.
Influence of Adhesive Layer on Actuation of Lamb Wave Signals
Authors: Sharif-Khodaei Z. , Liu Qu , Aliabadi M.H.
Published: November 2012

In this work, Lamb wave generation and propagation have been modelled in composite plates. Actuation and acquisition of signals when the PZT transducers are tied to the structure or bonded with an adhesive layer are investigated. The effect of adhesive thickness and actuation frequency of Lamb wave have been examined.
Analysis of Stress Intensity Factor for Cracked Flattened Brazilian Disk: Part II – Mixed-Mode Crack
Authors: Dong Shi Ming , Wang Qing Yuan
Published: November 2012

This paper presents a new method to conveniently calculate the stress intensity factors for the cracked flattened Brazilian disks under mixed-mode loading. The finite-element method is employed to confirm an assumption that the formula of the stress intensity factors for the cracked Brazilian disk subjected to pressure can be directly used to calculate the stress intensity factors for the cracked flattened Brazilian disk. The calculated results show that the assumption is valid and reliable. The calculated results also confirm that the Saint-Venant’s principle is still valid in fracture mechanics. In addition, the present paper proposes a concept of optimum load distribution angle.
Recycling of Al-W-B Composite Material
Authors: Shishkin Andrej , Mironov Viktor , Goljandin Dmitry , Lapkovsky Vijacheslav
Published: November 2012

A waste of composite material (CM), containing boron-tungsten fibre and aluminium matrix (CM Al-W-B) is investigated. A method of grinding has been used for processing of Al-W-B CM waste. This method has been carried out in several stages in order to obtain a powder with determined particle size. The milled material contains aluminium matrix alloy, boron and tungsten. The morphology of CM Al-W-B particles is described. The mechanism of disintegration and relationship between energy spent for disintegration, and a degree of milling of CM Al-W-B powder, are described. Possible applications of Al-W-B composite powder as a source material for obtaining a new composite ceramics by self-propagating high-temperature synthesis (SHS) are noted.
Abrasive Wear Resistance of Recycled Hardmetal Reinforced Thick Coating
Authors: Kulu Priit , Tarbe Riho , Žikin Arkadi , Sarjas Heikki , Surženkov Andrei
Published: November 2012

The aim of the current study was to elaborate and compare abrasive wear resistance of thick coatings deposited with different hardfacing technologies. To produce metal matrix composite (MMC) coatings commercial iron and nickel based powders with recycled hardmetal content of 40 vol. % were studied. For deposition technologies plasma transferred arc (PTA) hardfacing, high-velocity oxy-fuel (HVOF) spraying were used. The microstructure of produced thick coatings was examined, including the distribution of hard phase and homogeneity of metal matrix. Micromechanical properties, including hardness and elastic modulus of features were measured by universal hardness measurements. Furthermore, behavior of coatings subjected to abrasive rubber-wheel wear (ARWW) and impact wear (AIW) tests were studied. Wear resistance of experimental PTA hardfacings at low velocity ARWW and AIW tests notably exceeds that of HVOF sprayed coatings. Wear mechanism dominating at abrasive wear in most cases is the removal of metal matrix due to lower hardness. Assignment of hardmetal waste as initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Results indicate, that the choice of matrix for the same reinforcements can also be as an important factor for combating abrasive wear. Fe-based thick coating, produced by PTA is more wear resistant compared to the Ni-based ones.
Effect of Strain-Hardening Induced Grain Refinement on Springback in Microtube Press Bending Process
Authors: Jiang Cho-Pei
Published: November 2012

Seamless stainless microtube (SUS 304L) was selected for a detailed investigation of the strain-hardening influencing grain refinement and microstructural evolution during processing by varying press bending angles. The problem was approached in three stages. First, the microtubes were annealed to examine the initial grain size and analyzed the effect of grain size on mechanical properties by performing a tensile test. Second, a microtube press bending system was developed to observe springback behavior. Third, the microstructure of the microtube with different press bending angle was observed to investigate the effect of strain-hardening induced grain refinement on springback behavior. As a result, the occurrence of grain refinement reduced the springback amount. The mechanism of microstructure development in the shear zone during the press bending process is needle like, twin band and equiaxed and small rounded grains sequentially.
Propagation of Random Waves in Elastic Media with Microheterogeneities
Authors: Belyaev Alexander K.
Published: November 2012

Propagation of elastic waves in heterogeneous linear 1-D media is considered. The scalar wave equation is transformed by the Liouville substitution and the Dyson integral equation is applied for a statistically homogeneous field of heterogeneities. The result is the mean wave field which is analysed in detail for the exponential correlation functions. The general case of the random elastic medium with an arbitrary heterogeneity of small scale is considered and simple closed form expressions for the mean field and attenuation are derived.
Some Mechanical Models of Chemical-Mechanical Polishing Processes
Authors: Goldstein Robert V. , Osipenko N.M.
Published: November 2012

Chemical-mechanical polishing (CMP)-a perspective technology in fabrication of micro-and nanoelectronics elements, devices and systems. The development of models of CMP processes remains to be the actual problem. It is pointed out that known CMP models do not account for the features of chemical and mechanical mechanisms of interaction of active fluid and particles with a polished surface as well as an interaction of a viscoelastic pad with the surface. A description of the elementary acts of such interaction are absent in the available models. On the base of the analytical review of the current state of the theory and problems of (CMP) modeling some approaches were suggested to the problem accounting for the complex of the phenomena of different scales determining the polishing rate such as diffusion of slurry into the surface layer and restriction of time of chemical treatment of the surface by a rough pad being under the action of a mechanical load. A model of the CMP process was developed. Within the framework of this model a dependence of the polishing rate on the loading parameters was derived. The dependence generalizes the empirical Preston law.
Bulk and Surface Stability of Materials
Authors: Morozov N.F. , Tovstik P.E.
Published: November 2012

Buckling modes of a linearly elastic compressed medium are discussed. Stability of a plate lying on a soft elastic foundation is investigated. To the plate surface a membrane with initial stresses is attached. The stresses in the membrane simulate difference of equilibrium distances between atoms of crystal lattices of a surface layer (membrane) and of a plate. Also the influence of force and thermal stresses is studied. The chessboard-like stable buckling mode appears on the membrane surface at the stability loss. The ways of control of the wave length of buckling mode are discussed.
Integrity Assessment of Power-Plant Structural Elements Using Fracture Mechanics
Authors: Lukács János
Published: November 2012

The research work aimed to present the usability of the cracked round bar (CRB) specimen type for the determination of the linear-elastic plain strain fracture toughness values (KIc or KQ) on steels; and to demonstrate the applicability of the testing results for the reliability assessment of structural elements having cracks or crack like defects. Micro-alloyed structural steel and heat resistant steel were tested at elevated temperatures, at 260 °C and 410 °C, respectively, using small-sized specimens with small diameters. Four different equations were used for the evaluation of the tests, and the determined fracture toughness values were compared with one another. Reliability assessment calculations were realised on two structural element models, critical crack sizes and safety factors were determined for all cases.
A Simplified Determination of Creep Properties of Steels by Measuring their Crack Opening Displacements (COD) at Elevated Temperatures
Authors: Palotás Béla
Published: November 2012

The testing of creep resistance (for example σ1%/100000 h) of metals has been required for a long time (about 10 years) and some methods have been worked out to decrease testing time. The application of these methods has some difficulties. Now we have worked out a new empirical method to reduce testing time, namely COD measuring at an elevated temperature. The paper presents this method, which makes it possible to determine creep properties by measuring the materials COD at an elevated temperature. To determine COD we use notched samples with different radii and we tear them at an elevated temperature. The determination of COD is based on the Czoboly Radon method. By opening three different radii notches we approximate to zero radius which gives the COD. Master Curves of COD and creep resistance connections were drawn at 500 °C, which is not dependent on materials and they can be used for determining Creep Properties from COD measured at 500 °C. This method can be used for the comparison of the creep resistance of materials and for that of the creep properties of different zones of welded joints. The method is found useful in technical practice.
The Experiences with a Travelling Magnetic Field (TMF) Stirrer
Authors: Rónaföldi Arnold , Kovács Jenő , Roósz András
Published: November 2012

An experimental stirring unit (inductor) using travelling magnetic field was tested for developing a solidification facility equipped with a magnetic stirrer. The investigations were performed by using an Sn50Pb alloy at temperature of 230°C. In the course of the experiments, the magnetic pressure developing in the metallic melt, the flow velocity of melt and the loss of flow were investigated using the TMF inductor.
Scaling Cellular Automaton Simulations of Short-Range Diffusion Processes
Authors: Gyöngyösi Szilvia , Barkóczy Péter
Published: November 2012

By applying the cellular automaton method the short-range diffusion processes in metals can be efficiently simulated. Several examples for the two-and three dimensional modeling of recrystallization and grain-coarsening are know at the literature. In some previous works, results have been performed concerning the two-dimensional, stochastic automatons of grain-coarsening, recrystallization and allotropic transformation. In order to use these simulations also in technological processes, it is necessary to scale the results reached by the simulation. The primary aspect of adapting the automaton in technological processes is the quick-operating simulation. The aim is to develop a most simplified, scalable cellular automaton by which scaling can be efficiently performed.
Development of Complex Analytical Model for Optimizing Software of Wire Drawing Technology
Authors: Kovács S. , Mertinger Valéria , Voith M.
Published: November 2012

In the manufacture of products requiring multi-step wire drawing, it is helpful to use software that can aid in planning and that can calculate the values needed for optimum performance. The model described by analytical closed/explicit formulas provides the shortest calculation time. The aim of this study is to create a model described by analytical closed/explicit formulas approximating the measured data in the best way. An objective mathematical procedure are defined for model selection, and the selected model is proposed for the development of software with a short calculation time that optimizes the technological parameters of multi-step wire drawing and plans the drawing technology.
Validation of New Mathematical Model of Flank Wear by Different Methods
Authors: Pálmai Zoltán , Takács Márton , Farkas Balázs Zsolt
Published: November 2012

Having reviewed the literature on cutting and based on the optical, electron-optical and morphological examinations of wear processes we have reached the conclusion that it is possible to describe the abrasive, adhesive and thermally activated diffusion, oxidation processes in a single mathematical model. The model is a non-linear autonomous differential equation, which can be solved by simple numerical methods. The complex wear equation was validated by the results of the cutting tests performed with P20 carbide on C45 carbon steel. If we have this data, we can calculate the activation energy of the process determining the nature of the wear process. The apparent activation energy of wear is Q=151,7kJ/mol. The model can even be used with changing technological parameters, and the data necessary for the constants of the wear equation may as well be determined even by measurements performed on the tool during industrial manufacturing. By the mean of this data, we can calculate the activation energy determining the nature of the wear process.
Effect of Supporting Roll Setting on the Inner Structure of Cc Slabs
Authors: Réger Mihály , Verő Balázs , Csepeli Zsolt , Szabo Zoltan , Jozsa Robert , Kelemen Tibor
Published: November 2012

Mathematical model was developed to estimate the flow rate and direction and of the expected porosity level in the centre part of a slab. Calculations show that centreline segregation is basically affected, at a given composition and cooling technology by the setting, deformation and eccentricity of the supporting rolls. Bulging of the strand between the supporting rolls can also play role.
Dependence of the Surface Roughness and Localization Factor Parameters on the Background Correction of AFM Images: A Thin Film Characterization Study
Authors: Bonyár Attila , Molnár Lászlo Milán , Harsányi Gábor
Published: November 2012

A novel parameter called localization factor was calculated on contact mode atomic force microscope (AFM) images taken on gold thin film surfaces and was compared with the surface roughness parameters (Ra, RRMS). The aim of the investigation was to examine the dependence of these surface describing parameters on the background correction (generally post processing) of the AFM image. We found that the proposed localization factor parameter shows less dependence on the background correction compared to the surface roughness parameters and that it gives an identically characteristic value for four different thin film surfaces on the (1-100 μm2) scan range.
Preparation of Microcapsules for Self-Healing Polymers
Authors: Czeller Anna , Czigány Tibor
Published: November 2012

In this paper, melamin-formaldehyde microcapsules filled with pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) or epoxy were prepared via oil-in-water emulsion polymerization method. Two different routes were chosen from literature, and applied with some changes. The effects of modification of reaction conditions on the resulting capsules were studied. It was found that too low pH value in the emulsion causes burst polymerization of the wall material, without microcapsule formation. When pH was set to 4.5 spherical microcapsules were formed. Optical microscopy was used to evaluate the microcapsules.
Preparation and Characterization of Multilayer Graphene by Mechanical Milling and Related Applications for Ceramic Composites
Authors: Kun Peter , Tapasztó Orsolya , Czigány Zsolt , Balázsi Csaba
Published: November 2012

As graphene nanomaterials present exceptional mechanical, thermal and electric properties therefore it can be an excellent reinforcement material for ceramic composites. The research of ceramic composites incorporated with carbon-based fillers has focused on carbon nanotubes until now. In this work silicon nitride-based nanocomposites have been prepared with different ammount (1 and 3 wt%) of multilayer graphene (MLG) made by mechanical milling-based method as well as exfoliated graphite nanoplatelets (xGnP) and nanographene platelets (Angstron) in comparison. The morphology and microstructure of the sintered samples were studied by scanning electron microscope and transmission electron microscope. Phase compositions were determined by X-ray diffractometer. The bending strength and elastic modulus of MLG-silicon nitride composites showed enhanced values compared to the other graphene reinforced silicon nitride ceramic composites.