bluuebunny/crossref_metadata_2025 huggingface dataset:
An Optimal Process for Ultrasonic Amplitude Transformer Design with FEM
Authors: Liu Guo Yue , Guo Zhong Ning , Li Yuan Bo , Wang G , Huang Z.G.
Published: September 2011

The amplitude transformer is one of the most important parts in ultrasonic work system. To amplitude transformer, the resonant frequency and location of flange are two crucial design objectives. For variable cross-section amplitude transformer design, the traditional theory calculation seems to be too verbose and sometime hard to get efficient solution. This paper focuses on using commercial FEM software-ANSYS to achieve an optimal design of amplitude transformer.
PSO Based Steel Rolling Process Optimization
Authors: Yang Jun Jun , Shi Jia Chuan , Zhang Wen , Liang Li Ping , Zhao Pei Jian
Published: September 2011

Based on the analysis of the rolling process in iron and steel enterprises, an optimal load distribution model is established for rolling mills. The objective function is to minimize the total energy consumption. The equipment and process constraints are considered. The particle swarm optimization (PSO) is employed to get the optimal rolling reductions. The simulation of a six-frame strip demonstrates the feasibility of the proposed method in Jinan Iron & Steel Group. The experimental result shows that the proposed method is efficiency in the optimal load distribution problems.
Design of Computer Simulation Model for the Analysis 0f Coupling Effects between Actuators of Hydraulically Driven 6 DOF Parallel Manipulators
Authors: Ogbobe Peter O. , Ye Zheng Mao , Jiang Hong Zhou , Yang Chi Fu , Han Jun Wei
Published: September 2011

This paper presents a computer simulation model to analyze coupling effects between actuators of a hydraulically driven six degrees of freedom parallel manipulators. The design is based on the multi-body dynamics model of the system built using Kane’s formulation and hydromechanics’ principles. Combining the two parts, an integrated computer simulation model is designed to analyze coupling effects using joint space inverse mass matrix. The designed computer simulation model was used to establish a coupling effects relationship between actuators. The simulation results in frequency domain show that the coupling effect is heavier between odd and even numbered actuators. The result further reveal that the dynamics coupling property of the system increase with the frequency and reach the maximum value at the natural frequency. At a frequency higher than the natural frequency the coupling property decreases. This study can assist to provide optimum methods for mechanism designers and can offer a basis for comparing and selection of design options. It can also lay a good foundation for studies on decoupling control strategies.
Study and Application of Virtual Remanufacturing
Authors: Zhu Sheng , Yao Ju Kun , Cui Pei Zhi
Published: September 2011

Virtual Remanufacturing is an important technology of remanufacturing engineering, which has a distinct benefit to improve remanufacturing development. On the base of definition and characteristics analysis of virtual remanufacturing, this paper puts forward the virtual remanufacturing framework, key technologies and development environment, and describes the main application fields of virtual remanufacturing, which will provide a reference for virtual remanufacturing exploitation and development.
A Three-Dimensional Model of Droplet Impinging, Solidification and Suspension on the Substrate
Authors: Zhu Sheng , Yin Feng Liang , Liu Jian , Liang Yuan Yuan
Published: September 2011

A three-dimensional model was built to study a molten metal droplet impact on an edge of the substrate in droplet deposition manufacturing process for the first time. The whole calculation domain, including the substrate, was described using same fluid conservation equations, which is to say that the remolding and solidification of substrate was considered also. Droplet free surface was tracked by volume-of-fluid (VOF) algorithm. The effect of surface tension on the droplet was taken into consideration by means of considering surface tension to be a component of the body force. The simulated results show that the droplet in liquid phase can keep suspending on the substrate at a role of surface tension. A too high impact velocity would make parts of droplet splash away the substrate which is not allowed in manufacturing process. The offset between edge of droplet and side edge of substrate influences dramatically the impact of the droplet.
Effect of Polypropylene Fiber on Strength and Flexural Properties of Concrete Containing Silica Fume
Authors: Wang Hong Wei
Published: September 2011

A designed experimental study has been conducted to investigate the effect of polypropylene fiber on the compressive strength and flexural properties of concrete containing silica fume, a large number of experiments have been carried out in this study. The flexural properties include flexural strength and flexural modulus of elasticity. On the basis of the experimental results of the specimens of six sets of mix proportions, the mechanism of action of polypropylene fiber on compressive strength, flexural strength and flexural modulus of elasticity has been analyzed in details. The results indicate that there is a tendency of increase in the compressive strength and flexural strength, and the flexural modulus of elasticity of concrete containing silica fume decrease gradually with the increase of fiber volume fraction.
Numerical Simulation of Blade-Wake Interaction of Vertical Axis Tidal Turbine
Authors: Li Zhi Chuan , Sheng Qi Hu , Zhang Liang , Cong Zhi Ming , Jiang Jin
Published: September 2011

To study the blade-wake interaction of vertical axis tidal turbine (VATT)，particles were placed in the flow field to trace blade wake during numerical simulation. Numerical simulations were conducted utilizing Euler-Lagrange model. In the simulations, the continuous phase was solved by Reynolds-averaged Navier-Stocks(RANS) equation combined with SST turbulence model and the particle trajectories of the dispersed phase were determined by momentum equation. Numerical results of predicting instantaneous blade forces and blade wakes showed good agreement with the test data. The model was also compared with previous classic free vortex model (V-DART), vortex method combined with finite element analysis (FEVDTM) and 2-D vortex panel model (VPM2D). It showed that the present model was much better than the former.
Research of Marine Diesel Engine’s State Prediction Based on Evolutionary Neural Network and Spectrometric Analysis
Authors: Wei Hai Jun , Wang Guo You
Published: September 2011

In this paper, an evolutionary neural networks model is proposed to predict the content of metal elements contained in marine diesel engine lubricating oil, by fusing genetic algorithms (GAs) and error back propagation neural network (BPNN) to offset the demerits of one paradigm by the merits of another. The input data of metal content was detected by spectrometric analysis. Genetic algorithms are used to globally optimize the weights and threshold of BP neural networks. Moreover, one case study was presented to illustrate the proposed method. The prediction accuracy of the novel method is compared with that of only BPNN method to illustrate the feasibility and effectiveness of the proposed method. The relative error on average of results is 1.52%, it can meet the precision request of state detecting in marine diesel engine.
Performance Simulation Analysis and Design of the Scale Model for the Earth Pressure Balance Shield
Authors: Chen Xu , Shao Zhu Feng , Tang Xiao Qiang , Feng Ping Fa
Published: September 2011

Referring to the Earth Pressure Balance (EPB) shield with the diameter of 6.25m, a new experiment station of EPB shield is proposed, which is loaded with mechanical structure instead of traditional soil box. The structure of the experiment model is designed for the performance analysis of the EPB shield. The mechanical loading device, which is called the soil simulator, can simulate different geological environments. The soil simulator is capable of realizing three work states, such as earth balance pressure, earth under pressure, and earth over pressure. By adopting virtual prototype technology, parametric model of the shield station is established and the co-simulation scheme is determined. Besides, the kinematic analysis as well as variation principles between the displacement and driving forces of the propulsion system are obtained, which build the foundation for optimization design and control of the shield prototype.
Parametric Optimization for a Tapered Deployable Mast in an Integrated Design Environment
Authors: Deng Zong Quan , Zhang Yang , Huang Hai Lin , Li Bing
Published: September 2011

Deployable mast has a wide range of applications in aerospace industry. As lower weight of deployable mast can greatly save the cost of launching and higher stiffness can improve the loading capacity. This paper aims at designing a tapered deployable truss with lower weight and higher stiffness. The conceptual design and mobility analysis of tapered deployable module are first introduced. Then finite element model is then presented. The proposed structure is optimized towards the goal of maximizing the fundamental frequency and minimizing the structural weight to enhance its stiffness. In the integrated design environment of iSIGHT, Non-dominated Sorting Genetic Algorithm (NSGA-II) is chosen as the optimum tool for this dual objectives optimization issue with four constraints. The Pareto optimal solutions of this optimum problem are found after optimization. Simulation shows that the optimum value of design variables have the capability of enhancing the fundamental frequency by 17% and reducing structure weight by 8%.
Topology Optimization on the Material Distribution of Track Segment for Heavy Machinery
Authors: Li Yong , Wang Guo Qiang , Yan Zhen Hua
Published: September 2011

To achieve the rational shape and structure of large or super-large track segment, this paper investigated the optimal material distribution law of the track segment with topology optimization by variable density method. In this method the element density of the optimal area is the design variable, the maximum stiffness between the track segment and the terrain is the object, and the material volume per centum of the optimal area is the constraint. In this study, we obtained the topology optimal results of a track segment for a certain heavy-machinery by OPTISTRUCT software. The paper also presented the transitional geometrical distribution law of the optimal material from solid state to hollow state at the same constraint of the material volume percentum and at the different terrain stiffness. Finally, the optimal shape was put into application.
The High Quality Technical Research of Road Concrete Recycled Coarse Aggregate
Authors: Mandula M. , Hu Xiao Yu , Chen Feng Jin , Zhang Wen Long
Published: September 2011

This paper studies the recycling of solid waste concrete of the foundational content. Through the experimental research on the use of recycled aggregate and recycled concrete powder, I propose recycled coarse aggregate, recycled powder of various physical and chemical characteristic and the powder mixed with cement slurry mixed with recycled coarse aggregate on the surface of the mechanical properties after treatment. The results show that the coarse aggregate crushing value after surface treatment, strength characteristics of concrete can meet the requirements of ordinary concrete.
Theoretical and Experimental Study on the Wave Propagation through a Micro Gap
Authors: Chen Xiao Yun , Yu Gui Lan , Cao Wei Wei , Qiang Wen Tao
Published: September 2011

In the present paper, a preliminary exploration which includes the theoretical analysis and experimental study on the wave propagation through a micro gap was carried out. Harmonic waves, normal incidence, smooth and flat interface were taken into account. The theoretical and experimental results both show that the initial gap width has significant influences on the harmonics. Their relations may be effective on nondestructive evaluation of a pre-existing gap.
Designing of Velocity Measuring System of Initiating Explosive Devices Based on Photoelectric Method
Authors: Li Shi Meng , Wang Jun , Yang Lin
Published: September 2011

This paper introduced a new method of designing on the velocity measuring system of initiating explosive devices. We designed multiple selectable targets using the principle of photoelectric conversion. When the object passed through the targets, two pulses would generate separately. Through counting the spacing interval of the two pulses, we could calculate the mean velocity of the object passing through the targets, and revise it into the muzzle velocity. This paper designed the structure of photoelectric targets and circuits of the measuring system, also processed revising and error analysis of the measurement result. The system designed in this paper has the features of simple, reliable, high accuracy, good dynamic response, easy to disassemble and maintain, and is suitable for various environment with the reducing of the errors and inconvenience of traditional velocity measurements.
The Design for WR-06 Corrugated Conical Horn Antenna and its Application in Emissivity Measurement of Microwave Radiator
Authors: Cheng Chun Yue , Li Fang , Wu C. B. , He W.
Published: September 2011

This paper presents the design for a corrugated conical-horn antenna working in WR06 frequency band and its application in emissivity measurement of microwave radiator. For a calibration target of microwave radiometer, we consider design the corrugated conical-horn antenna to satisfy its measurement requirements of the emissivity of calibration target. The antenna is designed with small flare angle and low VSWR in a frequency range of 150±10GHz. The measurement results for electrical properties of antenna and emissivity of microwave radiator are presented in this paper. The results show that the performance of antenna is fit to the emissivity measurement of radiator of radiometer calibration target.
Infrared Small Target Detection under Complex Background
Authors: Peng Gui Hua , Chen He , Wu Qiang
Published: September 2011

This paper presents an algorithm for detecting the small infrared target under complex background. An method, Local Mutation Weighted Information Entropy (LMWIE), is proposed to suppress background. Then, enhance targets’ gray value by calculating the local energy. For the problem that the gray value of noises is enhanced with the gray value improvement of targets, image segmentation bases on the adaptive threshold. Experiment results indicate that it is a robust and effective small target detection algorithm.
Identification of the Vehicle Noise Source by Sound Intensity Method
Authors: Li He , Zhao Qing Rong , Wen Bang Chun
Published: September 2011

In this paper, we analysed the level of radiation noise and distribution of noise sources of car’s engine and front panels by using sound intensity method. To get the nephogram of sound intensity and sound power spectrum, we used the sound intensity probe and Multi-channel Data Acquisition Regulation System B&K 3560-D and Pulse Data Processing Analysis Software. By analysing experimental results, we can conclude the location of noise sources of these parts. The measurement results will serve as a reference for the car noise reduction.
Simulation for Microwave Nondestructive Detection of Thickness and Delamination in Layered-Dielectric in Metallic Substrate
Authors: Yang Yu E , He Cun Fu , Wu Bin
Published: September 2011

Microwaves penetrate inside of low loss dielectric materials and they are sensitive to the presence of internal interfaces and non-uniformities. This allows microwave nondestructive inspection techniques to be utilized for inspecting dielectric in metallic substrate. This article simulated Microwave inspecting thickness and delamination in layered-dielectric in metallic substrate, using open-ended rectangular waveguide probe. Effective reflection coefficient of microwave is used in the detection and evaluation to thickness or delimination in the media. This paper optimized the detection frequency and standoff, which provide a reference for the experimental study.
Analysis of the Difference between Static and Dynamic Performance of Copper Cylinder Pressure Measurement and the Correcting Method
Authors: Kong De Ren
Published: September 2011

The serious static-dynamic discrepancy will be caused when the copper cylinders statically calibrated are used to measure the dynamic pressure. In this paper, the reasons for static-dynamic error caused are analyzed in detail. Taking φ3.5×8.15 copper cylinders for instance, the static-dynamic error’s change law of this type of copper cylinders is analyzed. Dimensional analysis and analogical theory are used to set up the correction equation which can be used to diminish the static-dynamic error. The correction equation to diminish static-dynamic error is testified to be effective through combining with the actual experimental data. This paper gives an effective way to decrease the measuring error of copper cylinders statically calibrated.
The Measurement of Three-Dimensional Road Roughness Based on Laser Triangulation
Authors: Li Xiao Qin , Lu Zhi Xiong , Zhao Lan Ying , Li Zheng Hao , Guo Bing , Bai Xue Feng
Published: September 2011

This article did some non-contact measurement by laser triangulation principle on the A level hard road roughness, based on CCD imaging principle,used scanning galvanometer, which improved the measurement speed and surface measurement range, , drew the three-dimensional surface roughness profile curve by interpolation and fitting,It was in accordance with the standard range of A-road height spectrum. This measurement method have important guiding significance on the hard road roughness measurement and practice of the design of the relatively flat three-dimensional contours.
Optimization Design of Turbine Flow Sensor in Hydrovalve
Authors: Shi Yun Xu
Published: September 2011

The water level in refrigerator must be controlled accurately in order to adjust the refrigerator’s temperature, namely, a flow sensor needs to be designed to measure the water flow into the flume precisely according to the hydro-valve’s structure. In this paper, the simulation analysis has been done using the software FLUENT on the basis of theoretical analysis of the sensor, and the optimization design of the flow sensor structure has been given according to the analysis results, the results show that the flow characteristics of the sensor has been improved.
The Electric-Hydraulic Servo Equipment for the Real Force and Motion Simulation of Pumping Unit
Authors: Feng Yong Jian , Hong Ming , Huo Xiao Wei
Published: September 2011

In this paper, new type electro-hydraulic servo equipment is given for testing the working feature on pumping unit. It is the key to get the real simulation of motion and loading of pumping unit. The equipment in paper can be used to repeat all kind of the real force and motion on pumping unit. In order to get better simulation results, the algorithm for self-adaptation control with Kalman filter, which is used for error-free estimate of motion state in order to obtain high accuracy, is applied to solve powerful motion error—surplus force in passive loading system . All algorithms can be used in computer. Last, the test results of pumping unit loading are given. By actual use，the results show that self-adaptation control model with Kalman filter are used for decreasing error by motion of loading system is feasible and the control model can automatically regulate coefficients of regulator.
Rolling Contact Fatigue Crack Growth Prediction by the Asperity Point Load Mechanism
Authors: Hannes Dave , Alfredsson B.
Published: September 2011

The crack path and growth life of surface initiated rolling contact fatigue was investigated numerically based on the asperity point load mechanism. Data for the simulation was captured from a gear contact with surface initiated rolling contact fatigue. The evolvement of contact parameters was derived from an FE contact model where the gear contact had been transferred to an equivalent contact of a cylinder against a plane with an asperity. Crack propagation criteria were evaluated with practically identical crack path predictions. It was noted that the trajectory of largest principal stress in the uncracked material could be used for the path prediction. The mode I fracture mechanism was applicable to the investigated rolling contact fatigue cracks. The simulated path agreed with the spall profile both in the entry details as in the overall shape, which suggested that the point load mechanism was valid not only for initiation but also for rolling contact fatigue crack growth. Different equivalent stress intensity factor ranges were used to estimate the fatigue life, which agreed with the life of the investigated gear wheels.
Development of a Low-Constraint SE(T) Toughness Test
Authors: Tyson W. R. , Shen G. , Gianetto J. A. , Park D.Y.
Published: September 2011

CANMET-MTL has developed a low-constraint test designed to reduce unnecessary conservatism in the measurement of toughness for use in the assessment of flaws in pipeline girth welds. The design is based on tension loading using fixed (clamped) grips of a single-edge-notched BxB SE(T) specimen, side-grooved to promote plane-strain conditions. Equations have been developed to derive J-integral, CTOD and crack growth from measurement of load and crack-mouth opening displacement. Loading conditions (essentially distance between the grips) have been chosen to reproduce the crack-tip constraint of a circumferential surface flaw in a pipe in service under tensile or bending loads. In this paper, the development of the test and the principal findings from its use will be described.
Modelling of Crack Bifurcation in Laminar Ceramics with Large Compressive Stress
Authors: Kotoul Michal , Ševeček Oldřich , Profant Tomáš
Published: September 2011

Ceramic laminates designed with strong interfaces have shown crack growth resistance (R-curve) behaviour through microstructural design (e.g. grain size, layer composition) and/or due to the presence of compressive residual stresses, acting as a barrier to crack propagation. The goal of the contribution is to model the mechanism of crack bifurcation in laminar ceramics with large compressive stress which still have not been satisfactory explained. Experimental observations of the crack path in the multilayered ceramics tested under several kinds of loading showed crack penetration (i.e. crack propagating normal to the layers followed by crack bifurcation when the crack propagated from the tensile to the compressive layer. Numerical results [1] show that the initiation of crack bifurcation can be explained by the near-tip J-integral, provided that micro-cracks exist near the crack tip. We revisit the problem using the concept of Finite fracture mechanics and the matched asymptotic expansion method in order to evaluate the energy release rate criteria describing the competition of the crack bifurcation and straight crack propagation near behind the bimaterial interface.
Finite Element Analysis of Composite Flywheel with Two-Layer Pre-Stressed Rotor Structure
Authors: Ren Zheng Yi , Liu Jing Na , Li Qing Fen , Li Ke Fei
Published: September 2011

In this paper, considering the material properties of the composite flywheel and the characteristics of the pre-stressed structure, stresses and strains induced by rotor rotation and interference fit were calculated by finite element (FE) method based on the plane stress hypothesis, in the commercial software ANSYS. Based on the given material properties and the main dimension with a certain speed of rotation, three 2D FE-models of hybrid composite flywheel rotors with two-layer rotor structure were built with the unit property of plane stress, axisymmetric and plane strain respectively. Followed, the radial stress, circumferential stress and radial displacement of the rotor were obtained. The three simulation results are almost accordant with the present theoretical results. It shows that the numerical analyses are reliable. It can be shown that is advisable to design and optimize the flywheel rotor.
Modeling Radiation Effects on the Fracture Process in Simplified Nuclear Glass
Authors: Kieu Le Hai , Delaye Jean Marc , Stolz Claude
Published: September 2011

Experimentally, the evolution of several mechanic properties (hardness, density, Young’s modulus, fracture toughness) is observed in nuclear glasses under irradiation. In this work, classical molecular dynamics calculations are performed to better understand fracture mechanisms in simplified nuclear glasses at atomistic scale and to explain the radiation effects. Fractures are simulated in more disordered glasses, representative of irradiated samples, to reveal radiation effects. We observe a lower elastic limit and a greater plasticity in the irradiated glass that can explain its larger fracture toughness.
Basic Modes of Crack Propagation through the Interface in a Polymer Layered Structure
Authors: Zouhar Michal , Hutař Pavel , Náhlík Luboš , Knésl Zdeněk
Published: September 2011

The multi-layered structure components of dissimilar materials are used in many engineering applications to protect the base structure from outer damage. Typical examples of coated structures are pipes with the dimensional addition of protective layers (multi-layer pipes). The purpose of this development is to protect the main (functional) part of the pipes from damages (e.g. surface scratches, internal crack propagation). In the contribution the attention is paid to cracks existing and propagating in inner protective layer. In many cases the cracks are stopped at the interface between protective and functional layers. The important task is to decide if they penetrate further through the interface in the bulk material and thus cause the failure of the system. The critical stress for the crack propagation through the interface depends on the relation between bulk and coating materials as well as on the crack geometry. All these important topics are taken into account and their effect on crack propagation is broadly discussed.
Dimensionless Stress Intensity Factors of an Annular Notched Shaft
Authors: Chen Bo , Li You Tang
Published: September 2011

The tip radius ρ, depth t and field angle α of notch and the geometrical sizes a and b of shaft are looked as descriptive parameters in the annular notched shaft. Taken the crack, blunt crack and notch as breach, the stress field and displacement field near the tip of breach which serve dimensionless factor fα(a/b) as descriptive parameter are obtained. The effects of parameters ρ, t and α to fα(a/b) are analyzed. The connections between stress intensity factor of crack and stress concentrator factor of notch, between sharp V-notch and crack, between V-notch and U-notch have been founded.
Modelling of Nonlinear Creep and Recovery Behaviour of Cortical Bone
Authors: Lovrenić-Jugović Martina , Tonković Zdenko , Skozrit Ivica
Published: September 2011

A new one-dimensional constitutive model for human cortical bone is proposed to simulate the viscoelastic–viscoplastic behaviour occurring during creep-recovery tests.The material parameters are determined by fitting experimental results of creep-recovery tests reported in the published literature. An efficient computational algorithm for the integration of the proposed constitutive model at the material point level is derived. The derived algorithm in conjunction with the Jacobian matrix is implemented in the finite element code ABAQUS. The model predictions are found to be in good agreement with the experimental data presented in literature.
Investigation into Damage of AL-Mesh Bumper under Hypervelocity AL-Spheres Impact
Authors: Guan Gong Shun , Bang Bao Jun , Niu Rui Tao
Published: September 2011

The aluminum mesh/plate bumper was designed by improving on AL-Whipple shield, and a series of hypervelocity impact tests were practiced with a two-stage light gas gun facility at Harbin Institute of Technology. Impact velocities of Al-spheres were varied between 3.5km/s and 5km/s. The diameters of projectiles were 3.97mm and 6.35mm respectively. The hypervelocity impact characteristics of 5052 aluminum alloy mesh bumper were studied through hypervelocity impact on aluminum mesh/plate bumpers. The fragmentation and dispersal of hypervelocity particle against mesh bumpers varying with material and specification were analyzed. It was found that the mesh wall position, diameter of wire and separation distance arrangement and mesh opening had high influence on the hypervelocity impact characteristic of aluminum mesh/plate shields. At similar impact velocity, hypervelocity impact characteristics comparison with aluminum sheet bumpers of equal areal mass was thrust. The optimized design idea of aluminum mesh/plate bumpers was suggested.
Variational Principle and Buckling Analysis of Functionally Graded Plate with Temperature Changes
Authors: Fan Tao
Published: September 2011

In this paper, the variational principle for the simply supported FGM plate is presented by the variational integral method. Then, the stationary value conditions are obtained with the derivation of the varitional principle. At last, the vibration governing equation is illustrated, which will be benefit for the numerical simulation with finite element method in further investigations. From the stationary value conditions deduced by the variational principle, it can be observed that the buckling characteristics of the simply supported FGM plate can be influenced by the temperature changes.
Fatigue Damage in On-Axis and Off-Axis Woven-Fiber/Resin Composite
Authors: Montesano John , Fawaz Zouheir , Behdinan Kamran , Poon Cheung
Published: September 2011

In this study the tensile static and fatigue behaviour of a woven-fabric laminate is investigated in both the on-axis and off-axis material directions. Emphasis is placed on the development of damage and its influence on the stress-strain behaviour of the laminate. The test results illustrate that there is a high degree of anisotropic behaviour due to anisotropic damage development, which is evident by the variation of the material behaviour between the on-axis and off-axis test specimens. The fatigue tests also suggest that the on-axis specimens exhibit noticeable stiffness degradation, while the off-axis specimens do not. The qualitative results provide significant insight into the type of damage mechanism responsible for the observed behaviour.
Combined Influence of Expansive and Shrinkage Reducing Admixtures on the Shrinkage Behavior of Ultra-High Performance Concrete
Authors: Park Jung Jun , Yoo Doo Youl , Kim Sung Wook , Yoon Young Soo
Published: September 2011

Since ultra-high performance cementitious composite (UHPCC) exhibits remarkable compressive strength and ductility, its application for structural member provides significant reduction of the section. The use of low water-to-binder ratio and admixtures with high fineness induce large shrinkage strain, leading to the possibility of large occurrence of shrinkage cracks due to the restraints of the form and reinforcing bars. Therefore, this study admixes a combination of expansive and shrinkage reducing agents as a solution to reduce the shrinkage of UHPCC. The eventual appropriateness is computed to evaluate the free shrinkage and restrained shrinkage behaviors. From the test results, the admixing of a combination of expansive and shrinkage reducing agents is seen to achieve a reduction of the free shrinkage by 30% to 50% at 28 days and a reduction of the strain of the external steel by about 19%.
Solutions for Impact over Aerospace Protection
Authors: Neckel Leandro , Hotza Dachamir , Stainer Daniel , Janßen Rolf , Lezana A. G. R. , Dias A. , Al-Qureshi Hazim Ali
Published: September 2011

New ballistic protection systems based on alternative materials have been recently developed. One of the industry’s objectives is to develop lighter and stronger defensive systems, which allow higher mobility and safety for both vehicles and humans. This work studies the behavior of an aerospace protection against a projectile impact, seeking an optimized construction. The Al-Qureshi et al. model suggests a ceramic-metal layer system and describes its behavior. The literature shows, due to the considered parameters, the erosion tax and the loss of velocity. The phenomenon is described in steps, presenting particular effects for each. The equations are not equal between the stages showing different properties. The present work searches for a solution that can show the expression for mass and velocity, for each stage of the phenomenon. The results from the numerical method used were plotted and analyzed. The treatment was performed using Maplesoft Maple software. As a result, graphs were generated, which allow a deeper analysis of the model. Finally, advance in the knowledge of fracture processes in materials by high velocity impact can be concluded. This fact permits developments in materials that can perform shock absorption.
Effect of YbCl3-Zn-Epoxy Coating on MIC Behavior of Low Alloy Steel
Authors: Fu Yu Dong , Li Qing Fen , Wang Jun , Li Chun Hui
Published: September 2011

In the present study, the rare earths element YbCl3 was added into the Zn-epoxy coating, and the MIC behavior of the low alloy steel specimen with YbCl3-Zn-epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated and compared with the specimen of Zn-epoxy coating. Experimental results show that both the YbCl3-Zn-epoxy and Zn-epoxy coating may offer effective protection for the basic low alloy steel. However, the corrosion potential of the specimen with YbCl3-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the YbCl3-Zn-epoxy coating may offer more favorable protection. Results of X-rays diffraction (XRD) and surface micrographs of specimens show that more sulfides and corrosion products of YbCl3-Zn-epoxy coating were produced which increased the shielding property of the coating. The mechanism about the effect of YbCl3-Zn-epoxy coating on MIC behavior was further discussed.
Improvement of MIC Behavior of Ship Plate Steel with LaCl3-Zn Epoxy Coating
Authors: Li Qing Fen , Wang Jun , Fu Yu Dong , Li Chun Hui
Published: September 2011

The MIC behavior of the ship plate steel specimen with LaCl3-Zn epoxy coating in the sulfate-reducing bacteria (SRB) solution was investigated in this paper. The variation of corrosion potential over time of different specimens in SRB solution show that the corrosion potential of the specimen with LaCl3-Zn epoxy coating was obviously higher than the Zn-epoxy coating, suggesting that the LaCl3-Zn epoxy coating may offer better protection. The variations of lgflg |Z|=4.5 and fh with time show that the property of anti-infiltration and corrosion resistance of LaCl3-Zn coating is much better than the ones of Zn-epoxy coating. Results also show that more sulfides and corrosion products of LaCl3-Zn epoxy coating were produced which increased the shielding property of the coating. The experimental results of XRD and SEM are in good agreement with the ones of Ecorr, and EIS, etc. They all show that the LaCl3-Zn epoxy coating exhibits more favorable corrosion resistance property than the Zn-epoxy coating. It is obvious that coating the ship plate steel with LaCl3-Zn epoxy is an effective and promising method against the attack of SRB in marine environment.
Computational Analysis of the AFM Specimen on Mixed-Mode I+II+III Fracture
Authors: Li Qing Fen , Zhu Li , Yan Sheng Yuan , Zhang Xiao Nan
Published: September 2011

The computational analysis of an all fracture modes (AFM) specimen on mixed-mode I+II+III fracture is presented in this paper. The separated energy release rates (SERRs) along the crack front of the AFM-model are calculated by the modified virtual crack closure integral (MVCCI)-method and the commercially available software ANSYS. A transition model is built by adopting several 3D elements of SOLID45 and one point element of MASS21 in the ANSYS program. Under the related constraint conditions, the separate force and moments are respectively applied on the point element of the transition model, so the corresponding desired reaction forces can be obtained. When the desired loads are superimposed and applied on the AFM-model, the mixed-mode I+II+III fracture can then be achieved. Thereby, the SERR results are calculated. The calculation results show that the facture behavior of GII and GIII appears complex due to the global deformation and Poisson’s ratio, although the distribution of SEERs GI is symmetrical with respect to the middle point along the crack front. The total SERRs, GTn-values increase along the crack front with the minim value at one corner and the maxim value at the other corner. It can therefore be predicted that the fracture will occur initially at one corner on the crack front of the AFM-specimen in this case.
Crack Initiation Predictions of the AFM-Specimen under Bend and Torsion Loading
Authors: Zhu Shi Fan , Zhu Li , Li Qing Fen
Published: September 2011

In this paper, the computational predictions of crack initial breakpoint and deflection angles under bend and torsion loading conditions are investigated in conjunction with the modified virtual crack closure integral (MVCCI)-method by using the all fracture modes (AFM) specimen and commercial software ANSYS. The separated strain energy release rates (SERRs) along the crack front are calculated and subsequently converted to the stress intensity factors (SIFs) by using Irwin´s equations. Based on the SIFs results, the crack initiation predictions are presented by the maximum principal stress σ1'-criterion. Results show that when the AFM-model under a series of combined proportional bend and torsion loading conditions, asymmetrical stress fields are produced along the crack front. The presented investigation also shows that the maximum principal stress σ1'-criterion in conjunction with the MVCCI-method provides a powerful numerical tool for general computational approach to the fracture analysis of complex loading conditions.
Influence of the Type of Silica Fume on the Rheological and Mechanical Properties of Ultra-High Performance Concrete
Authors: Koh Kyung Taek , Park Jung Jun , Kang Su Tae , Ryu Gum Sung
Published: September 2011

Ultra-high performance concrete (UHPC) is a new generation of concrete developed through microstructure enhancement techniques for cementitious materials. UHPC exhibits extremely high compressive and flexural strengths exceeding 180 and 30 MPa, respectively, and remarkable durability compared to normal concretes. The fabrication of UHPC requires very low W/B ratio reaching merely 0.2, the use of large quantities of fine binder and superplasticizer without coarse aggregates, and the incorporation of steel micro-fibers. This study investigates the effect of the type of silica fume on the rheological and mechanical properties of UHPC. The adopted silica fume presents various contents of SiO2 and surface areas. From the experimental results, UHPC using silica fume with 94% of SiO2 3% of ZrO2, and surface area of 80,000 g/cm3 shows better flowability than UHPC using silica fume with 98% of SiO2and surface area of 200,000 g/cm3 by lowering the viscosity of the cementitious composites without decreasing the compressive strength. Therefore, the fabrication cost of UHPC can be reduced by smaller dosage of superplasticizer when using silica fume with Zr content .
Performance of Nylon Based Polymer Foams at Elevated Temperature under Tensile Loading
Authors: Izzard V.G. , Bradsell C.H. , Hadavinia H. , Morris V.J. , Foot P.J.S. , Wilson L.M. , Hewson K.
Published: September 2011

One of the primary applications of polymer based cellular solids is to act as an energy absorbing material during impact where compressive strain rates may reach 500-800/s. In reality, impacts occur over a wide range of temperatures and velocities at different angles of incidence. Understanding and modelling the behaviour of the polymer foams requires characterisation of the material response in detail. The stress-strain response that covers both compressive and tensile behaviour for a wide range of strain rates and temperatures are needed to characterize the mechanical performance of polymer foams as polymeric foams are highly nonlinear materials that undergo large deformation in crashworthiness related cases. It is reported in literature that any increase or decrease in temperature over the glass transition region can cause changes by order of magnitude in elastic modulus of polymeric foams. However, creation of cross linking at high temperature can affect the elastic modulus. In this work, the behaviour of two, polyamide-6 (PA-6) based closed cell foams at elevated temperatures were investigated covering the glass transition temperature. This work presents the variation of elastic and tangent modulus of two low densities PA-6 and PA-6/polyolefin (Nylon alloy) based foams. Empirical equations have been proposed to allow the prediction of modulus over a temperature range of 23°C to 120°C for these materials.
The Effect of Mesh Density in Lattice Models for Concrete with Incorporated Mesostructure
Authors: Eliáš Jan , Vořechovský Miroslav
Published: September 2011

This paper shows that mesh density dependency in brittle element lattice models cannot be completely removed by incorporating material mesostructure. This is concluded as a result of a series of simulations of fracturing in concrete using a 2D rigid-body-spring network. In the case of notched beams loaded in three-point-bending (TPB), adding finer grain structure led to a significant reduction in the dependency of the peak force on the mesh density. However, the energy dissipated during the fracture simulation was still affected significantly by the mesh density.
Optimal Elastic Design of CFCs
Authors: Stasiuk Galyna , Piat Romana , Sinchuk Yuriy
Published: September 2011

The aim of the proposed studies is the development of the carbon/carbon composite with prescribed elastic properties. To achieve this, a microstructure optimisation problem for estimation of the microstructure with prescribed stiffness is formulated. The design variables of the posed problem are the local fibers distribution and porosity. The volume fractions of the fibers and pores in the whole microstructure are fixed. Material properties of the local microstructure of the composite are calculated using virtual models. Semi-analytical homogenization procedures were used for the development of these models. Modeling results are compared with elastic properties obtained experimentally by tension and compression test and ultrasonic studies of the bulk material. Approach to design microstructure for three point bending test is proposed.
A Role of Destructive and Non-Destructive Tests in Creep Damage Identification
Authors: Kowalewski Zbigniew L. , Szymczak Tadeusz , Makowska Katarzyna , Augustyniak B.
Published: September 2011

The paper presents relationships between strain level generated by creep process and two parameters determined form non-destructive tests, i.e. acoustic birefringence and amplitude of magnetoacoustic emission for three kinds of steel: 40HNMA, P91 and 13HMF. Moreover, the relationships between prior deformation level and selected mechanical parameters resulting from the standard tensile tests subsequently carried out at room temperature were established. As a consequence, this enabled to formulate mutual relationships between these mechanical parameters and parameters obtained from the ultrasonic/magnetic investigations.
Small Fatigue Crack Growth Behavior from Artificial Notch with Focused Ion Beam in Annealed 0.45% Carbon Steel
Authors: Sakamoto Junji , Takahashi Yoshimasa , Noguchi Hiroshi
Published: September 2011

The aim of this study is firstly to investigate the applicability of a sharp notch with Focused Ion Beam (FIB) as a crack for fatigue limit evaluation. Secondly we investigate a condition in which artificial defects (drilled hole, FIB notch) can be used as a crack for fatigue limit evaluation. To achieve the aim, the growth behaviors and the non-propagating crack sizes of small fatigue cracks initiated from a FIB notch and a drilled hole are carefully compared with those of an annealed fatigue crack which imitates an ideally sharp crack. The results show that a FIB notch can be used as a crack for fatigue limit evaluation under some conditions. The results also show that the condition which controls the applicability of an artificial defect as an ideal crack for fatigue limit evaluation is strongly dependent on the relation between (i) the length of a non-propagating fatigue crack and (ii) the crack length when the small fatigue crack growth behaviors from an artificial defect and an ideal pre-crack become almost the same. It is found that the length of (ii) can be obtained by the analyses using the number of cycles from a certain crack length to failure.
Cellular Automata Multiscale Model of Creep Damage for Metals
Authors: Nowak Krzysztof
Published: September 2011

Polycrystalline materials like metals fail in creep conditions due to development of inter- or intra-granular voids. The model of creep damage is proposed which simulates voids growth on microscale using Cellular Automata (CA) technique at RVE level, coupled with creep deformation on macroscale. It is assumed that experimentally observed creep deformation is a result of interaction between hardening and softening of a material. The softening process is mainly due to voids development and it is built in deformation model by weakening of effective stress by damage parameter calculated by CA part of the model. Parameters of model are based on primary and secondary stages of creep experiments. The results of simulations show that multiscale model predicts quite well times to failure and strains at failure.
Experimental Investigation of Fatigue Crack Growth in the Welding Nugget of FSW Joints of a 6060 Aluminum Alloy
Authors: Marcassoli Paolo , Longo Michela , D'Urso Gianluca Danilo , Giardini Claudio , Pastore T.
Published: September 2011

The work investigates the fatigue behavior of friction stir welded butt joints by means of fracture mechanics techniques. FSW joints of artificially aged AA6060 T6 aluminum alloy were studied. The welding was performed on 8 mm thick butt joined sheets by means of a CNC machine tool. Welding speed in the range between 117 and 683 mm/min and tool rotational speed between 838 and 1262 rpm were considered. Fatigue crack growth tests were performed according to ASTM E647 standard on CT specimens, under constant load amplitude conditions, at 0.1 minimum to maximum load ratio, with the notch placed in the dynamic recrystallization zone of weld nugget, oriented along the welding direction. The comparison of results demonstrates the crack growth rate is always equal or lower than the base material at low values of stress intensity range. At ΔK values above 12 MPa√m, crack growth rate was found to be higher than base material for high feed, low speed and high feed/speed ratio.
Peridynamic Theory for Damage Initiation and Growth in Composite Laminate
Authors: Oterkus Erkan , Madenci Erdogan
Published: September 2011

A recently introduced nonlocal peridynamic theory removes the obstacles present in classical continuum mechanics that limit the prediction of crack initiation and growth in materials. Furthermore, damage growth in composites involves complex and progressive failure modes. Current computational tools are incapable of predicting failure in composite materials mainly due to their mathematical structure. However, the peridynamic theory removes these obstacles by taking into account non-local interactions between material points. This study presents an application of the peridynamic theory for predicting damage progression from a central crack in fiber reinforced composite plates subjected to uniaxial tension loading.