bluuebunny/crossref_metadata_2025 huggingface dataset:
The Case Study on Model Reconstruction Method for Inner Un-Measurable Parts
Authors: Lu Bi Hong , Zheng Xiao Fang
Published: October 2009

Reverse Engineering (RE), as the important technology for learning and mastering the advanced technology, as well as shortening the period of product design and development, has already become the highlight in the manufacturing industry. But there are some inner un-measurable parts, like couplers. The inner form information of the coupler can not be fully captured without any cutting, which is one of the bottlenecks in RE. Therefore, an effective method needs to be explored for reconstructing lumen model. Taking model reconstruction of coupler lumen as a case, an assembly reverse method is proposed by analyzing the parts functions and restraint relations in coupler. The method in detail is that, firstly, all parts are assembled in the coupler body lumen, then, according to assembly relations and the enveloping space determined by movement scope of individual parts, the coupler lumen shape can be obtained. The method proposed is successfully applied in model reconstruction of heavy haul coupler, and which provides a common solution of model reconstruction for inner un-measurable parts.
TBM Motion Simulation: System Configuration, Motion Analysis and OpenGL Performer Based Realization
Authors: Yang Jian Yu , Li Gang , Cheng Jun , Wang Wan Shan
Published: October 2009

It’s necessary to apply numerical prototype technology in developing processes of a TBM, and the application of VR system can enormously enhance the simulation effect. In the article, hardware configuration of a VR system for TBM motion simulation was discussed and the module function was analyzed. According to the practical working condition, motion analysis of TBM key components was carried out, and motion model was formulated. A model processing method using Deep Exploration and Creator was introduced, for transforming numerical models from CAD software to VR environment, and for dealing with the accompanying data loss. The article also discussed scene graph constructing method based on OpenGL Performer and developed a TBM motion simulation program.
A Novel Approach to Hand Gesture Recognition for Virtual System Based on Adaptive Background Model
Authors: Tan Wen Jun , Wu Cheng Dong , Zhao Shu Ying , Xie Hua Long
Published: October 2009

The interactive approach to virtual system is a hot research topic. This paper presents a novel interactive approach based on hand gesture recognition. The hand gesture segmentation method is based on the adaptive background model. The method improves the ability of adaptation environment. And an improved algorithm of hand recognition is presented by using Fourier Descriptor and BP neural network. Experiment results indicate that the approach is flexible, realistic and exact.
A Framework of New Generation Intelligent CNC System
Authors: Wang Jun , Shu Qi Lin
Published: October 2009

In this paper, we present a conceptual framework for designing and implementing an intelligent CNC system. The architecture and functional modules are derived from requirement analysis, and they are designed to have a thinking capability before, during, and after the execution of the manufacturing task, so that the assigned task can be effectively executed while dealing with unexpected changes occurring on the shop floor. Also, the data model for supporting the architecture is addressed based on the STEP-NC data model or ISO 14649. The framework presented can be used as a paradigm for new generation intelligent STEP-compliant CNC.
Intelligent Control of CNC System Based on STEP-NC
Authors: Chen Xiu Sheng , Zhang Cheng Rui , Cao Shu Kun , Liu Ri Liang , Wang Qiang , Lan Hong Bo
Published: October 2009

In this paper, Data model used in intelligent CNC system based on STEP-NC is presented. A multi-agent architecture of the intelligent CNC system based on STEP-NC is proposed. The architecture consists of fourteen functional agents, such as interpreter agent, process planning agent, simulation agent, tool path planning agent, monitoring agent, expert system agent, etc. Some key technologies to implement the intelligent control including simulation, online inspection and expert system are discussed detailed. As a result, the architecture and key technologies proposed in this paper will aid the development work of the intelligent STEP-NC system.
Simulation of Splicing Cavity Shape Based on FLUENT
Authors: Chang De Gong , Li Heng , Xiao Zhi Juan
Published: October 2009

Based on the analysis of the compressed airflow within air splicer, the simulation of the splicing cavity was performed by using FLUENT and the air fluid field distributions of the aqueduct bodies with various shapes were obtained. The influence of the splicing cavity shape on yarn splicing quality was then analyzed and the satisfying splicing cavity shape was determined.
Design of Battlefield Weather Environment Automatic Collection and Processing System
Authors: Zhu Min , Li Hai Yan
Published: October 2009

Battlefield weather environment can’t be collected automatically in the existing artillery command automation system, and the response speed of this system is affected seriously. So, firstly, the new-style wind speed, wind direction, temperature and humidity sensor are used to convert these weather parameters into frequency, gray code, voltage. Then the PIC16C73 chip is adopted to translate the output such as frequency and voltage into binary code which is identified easily by computer. The gray code is input into computer directly, and be translated into azimuth by programming. Finally, GAL20V8 and tri-state buffer 74HC573 are used to connect the four kind weather parameters with computer respectively through different port. The automatic collection and processing of battlefield weather environment is realized, and real time and accurate information source for command automation is provided.
Research on Tool Cutting Monitoring System Based on Cutting Force and Workpiece Surface Image Texture
Authors: Wang Peng , Xin Jing Lei , Li Ji Xiang , Yin Shi Wei
Published: October 2009

Aim at the problem of tool cutting monitoring system between tool wear estimate by gradual information and judgment of tool failure by sharp signal, this study is to construct an integration measurement. It puts forward density parameter E of outline peak of machined surface image texture to estimate tool wear condition. It researches tool failure judgment with cutting force monitoring. Hence real-time monitoring of cutting process can be implemented to represent cutting-tool wear, failure and rationality of parameter selection in cutting state.
Garbage Crusher Fault Diagnosis Based on RBF Neural Network
Authors: Sun Yong Hou , Li Cong , Huang Mei Fa , Jing Hui
Published: October 2009

The garbage crusher is a new kind of crusher for garbage crushing when processing Municipal Solid Waste (MSW). With the development of automatic equipment and the complication of structure and properties of the garbage crusher, the fault diagnosis of garbage crusher is very important. In this paper, according to the fault symptoms and parameters, Radial Basis Function Neural Network (RBF NN) is used for fault diagnosis of the garbage crusher. The structure and inference of RBF NN are discussed in detail. The garbage crusher fault diagnosis model is established based on RBF network. At last, the fault of mechanical system is taken as an example of garbage crusher fault diagnosis. Training simulation results of the neural network are given base on MATLAB software. The result shows the RBF NN is suitable for fault diagnosis of garbage crusher.
The Analysis of Microrack Tip Plastic Zone Formed in Thin Films after LCF Tests of Austenitic Steel Used in NPP I
Authors: Eterashvili Tamaz , Dzigrashvili T. , Vardosanidze M.
Published: October 2009

The study deals with the TEM characterization of samples after low-cycle fatigue (LCF) tests of austenitic stainless steels used in nuclear power plants (NPP). Microcracks are observed in the TEM thin films prepared from standard cylindrical bulk samples. In plastic zones, at the tips of microcracks, several three-dimensional crystal structure defects are detected: 1. Arched extinction contours, 2. Zone of disorientations, 3. Deformation twins of different orientations, 4. Short micro cracks deviated from the main crack direction. The above defects have been studied using TEM, including micro-diffraction; trace analysis and dark-field techniques. It is shown that the microcrack and the created defects represent the means of relaxation of elastic stresses retained in the sample after LCF. It is also shown that redistribution of stresses leads to the nucleation of microcracks and subsequent creation of all the observed defects. A dislocation scheme of the stresses, detected by the extinction contours at microcrack tip, is proposed. The comparison of the proposed scheme of stress distribution with the TEM micrographs shows a good resemblance. Consequently, a topology of stress distribution at microcrack tip - before formation of plastic zone - is determined. The shape represents a three-leaved figure. Compliances and differences between the proposed scheme and the experimentally observed defects and plastic zone size are discussed based on crystallographic analysis of the respective electron diffraction patterns.
Effect of Specimen Configuration and Loading Types on Fatigue Life of an Annealed 0.42% Carbon Steels
Authors: Wang Xi Shu , Kawagoishi Norio
Published: October 2009

In the present study, a unified crack growth law based on the small fatigue crack growth law was investigated using specimens with different configurations and loading types for the annealed 0.42% carbon steel. Then, a convenient prediction method of fatigue life was proposed. This small fatigue crack growth rate was uniquely determined by the modified small crack growth law, , despite of changing for specimen configurations and loading types. The constants of can be estimated by an empirical equation of without stress/strain gradient. Considered the effect of stress gradient for different specimen configurations and loading types, the stresses under bending loadings and specimen configurations was calculated from that under push-pull loading. Therefore, the fatigue life of the specimens with different configuration and under different loading types can be simply estimated through the fatigue crack growth law based on the only tensile strength of carbon steels. The availability of proposed method was confirmed experimentally by the results of several carbon steels.
Finite Element Analysis for Concrete Damage under Freeze-Thaw Action
Authors: Mao Ji Ze , Wang Hong Ye , Zhang Zhi Yuan , Liu Zong Min
Published: October 2009

Freeze-thaw damage is one of the most representative damages in concrete durability. Commonly, freezing and thawing tests are conducted to investigate the freeze-thaw resistance of concrete, and the loss of dynamic modulus of concrete is regarded as the failure criterion. However, the research on the evolution of concrete strength during the damage process is still not enough when subjected to freezing and thawing. In this study, the concrete freeze-thaw deterioration was considered as isotropic elastic damage, and relative variation functions of dynamic modulus and Poisson’s ratio with freeze-thaw cycles were set up. Based on damage mechanics, the Ottosen failure surface model with four parameters was established to indicate the relationship between the concrete freeze-thaw failure surface and freeze-thaw cycles. Then the four-parameter failure surface model was set into ADINA finite element software program for secondary development to investigate the strength properties of concrete component under freeze-thaw action. The relationship between load and deflection of concrete was analyzed and simulated after 0, 25 and 50 freeze-thaw cycles. The simulated and experimental results are basically identical, which demonstrates that this finite element simulation is a feasible way to analyze and evaluate the performance of concrete structures in cold regions.
Analysis of Nonlinear Heat Transfer and Residual Stresses during Multi-Pass Welding of Penetration Assembly
Authors: Li Hong , Li Li
Published: October 2009

Welding residual plastic strains and stresses cause errors during the assembly and reduce the strength of the structure. Based on an elastic-plastic-model, a three-dimensional finite element numerical simulation of multi-pass butt welding of a representative penetration assembly is carried out in this paper. The nonlinear transient temperature field and the real-time dynamic stresses field during multi-pass butt welding with girth welds are obtained. In the end, the residual stresses of the complicated stainless steel penetration structure are calculated by FEM software ANSYS.
Experimental and Numerical Study on the Mode I Delamination Toughness of Z-Pinned Composite Laminates
Authors: Zheng Xi Tao , Gou Lin Hu , Han Shu Yun , Yang Fan
Published: October 2009

An experimental investigation was performed on mode I delamination of z-pinned double-cantilever-beams (DCB) and associate z-pin bridging mechanisms. Tests were performed with ten types of samples: (1) big-pin reinforced DCB (double-cantilever-beams) with three areal densities D=2.01%, 5.15%, 8.04%, respectively; (2) median-pin reinforced DCB with three areal densities D=0.85%, 2.17%, 3.40%; (3) small-pin reinforced DCB with three areal densities D=0.25%, 0.63%, 0.90% and (4) without pin reinforced DCB specimens. Delamination tests samples were prepared from unidirectional continuous carbon ﬁbre/epoxy prepreg (T300/TDE86), made into 3 mm thick unidirectional laminates with and without a block of Z-pins in the crack path. Fracture testing was carried out under Mode I (standard DCB test). Experiments have shown that increases in debond resistance and ultimate strength depend on the material, size, density, location of the pins and the mechanisms of pin deformation.
A finite element (FE) model is developed to investigate mode I delamination toughness of z-pin reinforced composite laminates. The z-pin pullout process is simulated by the deformation of a set of non-linear springs. A critical crack opening displacement (COD) criterion is used to simulate crack growth in a DCB made of z-pinned laminates. The toughness of the structure is quantified by the energy release rate, which is calculated using the contour integral method. The FE model is verified for both unpinned and z-pinned laminates. Predicted loading forces from FE analysis are compared to available test data. Good agreement is achieved. The numerical results indicate that z-pins can greatly increase the mode I delamination toughness of the composite laminates.
An Iterative FEA Scheme for Analysis of Micro-Pillar Compression Test
Authors: Kim Jae Hyun , Choi Hyun Ju , Jang Bong Kyun , Lee Hak Joo , Choi Byung Ik
Published: October 2009

In this study, we propose an interesting scheme for analyzing micro-pillar compression test results based on finite element method. It uses only load and displacement data measured by micro-pillar compression test, a framework of conventional incremental metal plasticity, and an iterative scheme for updating the material parameters. This is an inverse approach to determine the constitutive relation of materials based on experimentally measured load and displacement. As a demonstrative example, Ni-Co micro-pillars with a diameter of 10 ㎛ and a height of 20 ㎛ were fabricated by micro-machining process, and their load-displacement data were measured by a micro-pillar compression tester. Using the proposed scheme and the measured load-displacement data, the stress-strain curves for the Ni-Co micro-pillars were estimated.
Study of Dynamic Impact Behaviors and Ballistic Properties of Hybrid Composites
Authors: Guo Ying Nan , Sun Qin , Wu Ling
Published: October 2009

This paper deals with the ballistic properties of two kinds of hybrid composites: Kevlar/Carbon laminates and S-Glass/Carbon laminates. Twelve kinds of combinations of samples were made including various fibers; various fiber orientations and various target thickness. Air-gun tests were carried out to determine the response of these combinations of hybrid laminates subject to impact loading.
Compared with the test, an explicit finite element (FE) model was built with Pam-crash Code to simulate the impact process. The bullet was considered as a deformable body in contact with the composite shells. The Ladevèze model was used to describe the unidirectional properties of Carbon plies and Ladevèze fabric model was used to describe the homogeneous properties of the S-glass and Kevlar laminates. The influence of different parameters on the impact behavior of the two kinds of hybrid laminates was considered analytically. Results show very good agreement with the experimental data. Suggestions are also presented for the better hybrid mode to improve the ballistic properties.
On Numerical Analysis of Creep Fracture Behaviour of Medium Density Polyethylene
Authors: Skozrit Ivica , Tonković Zdenko
Published: October 2009

An implicit numerical algorithm for the integration of the primary/secondary creep constitutive law at the material point level is derived. For the presented constitutive model, the experimentally obtained material parameters for the medium density polyethylene (MDPE) are taken from literature. The derived algorithm in conjunction with the Jacobian matrix is implemented in the finite element (FE) code ABAQUS by using the user subroutine CREEP. The accuracy of the proposed algorithm is demonstrated.
Fracture Mechanisms of Metal Plates under Off-Centred Impact
Authors: Bivin Yu.K. , Simonov I.V.
Published: October 2009

Experimental results on the ballistic limits and failure mechanisms that lead to perforation in aluminum alloy target plates of 1-6 mm thickness by solid spherical projectile are presented. The projectile was launched between velocities of 150 m/s to 700 m/s by using the 10mm smooth bore gas gun. In this study, the attention was focused on the peculiarities of penetration process when the impact point approaches closely to the free or firmly fixed edge of the plate. The results were compared with the case of central impact and with others under changing the boundary condition, thickness and the target material properties.
Creep and Fatigue Damages of Ni-Base-Superalloy Caused by Strain-Induced Anisotropic Diffusion of Component Elements
Authors: Miura Hideo , Suzuki Ken , Ito Hiroyuki , Inoue Tatsuya
Published: October 2009

The mechanism of the directional coarsening of ' phases (rafting) of Ni-base superalloy under an uni-axial strain was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni3Al(001) interface structure, The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Pd was one of the most effective elements which restrain Al atoms from moving around the interface.
Detection of Delamination Damage in a Composite Laminate Beam Utilising the Principle of Strain Compatibility
Authors: Wildy Stuart , Cazzolato Benjamin , Kotousov Andrei G.
Published: October 2009

This paper presents an experimental investigation of a new method for damage detection based on the most fundamental concept in continuum mechanics: strain compatibility. Compliance with this principle implies a deformed material is free from discontinuities, which are indicative of many types of structural damage. Therefore the principle of strain compatibility, in its ability to identify discontinuities, is very promising as a new foundation for future research into non-destructive evaluation and structural health monitoring technologies. The proposed method has many advantages compared to existing damage detection techniques, such as its invariance to material properties, type and intensity of loading, and the geometry of the structure. In this paper, a proposed formulation of the strain compatibility equation for beam structures, which is invariant to loading intensity, is presented. An experimental investigation of the proposed algorithm was conducted on a delaminated cantilever beam, utilising a PSV-3D scanning laser vibrometer. The experiment demonstrated that the strain compatibility technique can accurately locate delamination damage in composite beam structures.
Numerical Interpretation of Bond Between Steel and Concrete in Presence of Corrosion and Cyclic Action
Authors: Giordano Luca , Mancini Giuseppe , Tondolo Francesco
Published: October 2009

Bond between steel and concrete in reinforced concrete structures plays a fundamental role. The stress transfer mechanism depends on the condition of the contact surface between the two materials, the mechanical characteristics of concrete near the rebar and on the available level of confinement. Corrosion of reinforcing bars in concrete structures modifies those three factors. Because of corrosion, on the rebar surface a granular oxide layer is present and with its expansion it generates a significant radial pressure; consequently tensile stresses grow till cracking of the concrete cover with a subsequent reduction of the confinement effect. Moreover the presence of a mechanical action modifies the resisting mechanism producing an increasing damage. In this study, a model is presented for the numerical simulation of experimental tests on r.c. ties subjected to mechanical action; furthermore some considerations on reinforced concrete ties subjected also to corrosion effect are reported. From those analyses it is possible to estimate a modified bond-slip law between the reinforcing bars and the concrete, in order to take into account the level of damage.
Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy
Authors: Fukudome T. , Kawagoishi Norio , Kariya K.
Published: October 2009

Ultrasonic and rotating bending fatigue tests were carried out using plain specimens and specimens with a small blind hole for an extruded and age-hardened Al alloy 7075-T6 in different environments in order to investigate the effect of humidity on fatigue strength and fracture mechanism. Fatigue strength was decreased by high humidity under both tests. The effect of humidity on fatigue strength was larger in ultrasonic fatigue. The humidity affected both of crack initiation and propagation processes. Crack propagated in tensile mode then changed to shear mode macroscopically in all environments under ultrasonic fatigue, though it was only in tensile mode under rotating bending fatigue. These differences in fracture mechanism related to the difference in environmental effect on fatigue strength in both tests.
Non Destructive Characterization of Concrete Joints Using the Scaling Subtraction Method
Authors: Antonaci Paola , Bocca Pietro G. , Bruno Caterina L.E. , Gliozzi Antonio S. , Scalerandi Marco
Published: October 2009

The evolution of concrete behavior in the proximity of a joint under the effect of varying external pressures is studied by means of a novel nonlinear ultrasonic technique denoted as Scaling Subtraction Method. The results obtained show that the proposed method is effective in describing the occurrence of micro-structural changes near the joint and detect potential conditions for crack opening and damage initiation.
Investigation of Effect of Additives on Adhesive Properties of Silicone Rubbers Sealant
Authors: Liu Jie Sheng , Wu Shao Peng , Mi Yi Xuan
Published: October 2009

Additives are always added into silicone rubber to improve properties. As a sealant, it is well known that the adhesion property is a key aspect of the sealant system. The effect of additives on the adhesion properties of silicone rubber sealant are discussed in this study. The results showed that the adhesive properties of samples with single coupling agent are lower than that with multiple coupling agents. The adhesive properties of sample first increase with increasing amount of coupling agent and then decrease linearly. The adhesion strength of SR sealant decreased with the amount of the plasticizer and filler added into the silicone rubber has little influence on the adhesion strength of silicone rubber.
Capillary Cohesion between Two Spherical Glass Particles
Authors: Hoornahad H. , Koenders Eddy A.B. , van Breugel Klaas
Published: October 2009

For developing a unique model in which the rheological performance of fresh concretes from zero-slump to self compacting concrete can be described, it is necessary to define workability in terms of fundamental physical entities. In order to achieve this, the concept of capillary cohesion from science of granular physics has been considered as the first step for investigation. In this paper, focus is on this concept and providing some preliminary achievements of the experimental work. In wet granular material the presence of liquid generates cohesion between particles and affects the mechanical properties of the granular media to a large extent. For the simulation of the behavior of this material by considering pendular state for liquid content, a discrete element method (DEM) is used. The cohesion between a grain-pair is expressed as an explicit function of local geometrical and physical parameters. In this study emphasis is on static and/or quasi-static situations. Since the cohesion dominates over other effects of the liquid, such as viscosity and lubrication, the effect of the size of particles on the cohesion arising from the liquid bridge is investigated explicitly. Based on experimental results, a closed-formula approximation is developed that can be used to calculate the capillary force acting between two glass spheres as a function of the separation distance for a given bridge volume.
Contact Damage of Curved Multi-Layered Ceramics: Prepared by Slip Casting Technique
Authors: Qasim Tarek , Wee Yeo Khee , Cai Wei Lun , Hu Xiao Zhi
Published: October 2009

Contact damage of curved multi-layered systems, consisting of a brittle zirconia (3Y-TZP)/Alumina (Al2O3) coating – prepared by slip casting – on a compliant polymeric substrate from indentation by a hard tungsten carbide sphere is investigated. The essence of this study is to compare the structural performance of layered ceramics, and monolithic ceramic in the brittle coating and compliant substrate of dental crown-like systems. The specimens are loaded at the axis of symmetry. The failure evolution to initiate cracking and final failure patterns in curved multi-layered specimens are compared to those of the single layer specimens of the same thickness and the same study are conducted again with the flat specimens. The onset of fracture is observed in situ using a video camera. It is demonstrated that in all specimens, cone cracking occurs prior to radial cracking, with the latter being defined as the primary mode of catastrophic failure. The multi-layered ZTA (Zirconia Toughened Alumina) specimens prepared by slip casting possessed a distinct final failure pattern in comparison with a single layer specimen. The results of this study provide useful guidelines for building brittle multi-layered coating systems with the functionally graded feature, and complex shapes with geometrical uniformity.
Effect of Wear on the Fatigue Life of Annular Notched Shaft Based on Product Lifecycle Management
Authors: Li You Tang , Rui Zhi Yuan , Yan Chang Feng
Published: October 2009

Anti-fatigue design is a key content in product lifecycle management and there are many factors to affect the fatigue life of parts. For designing the fatigue life of shaft with a circumferential notch exactly, the influencing factors have been analyzed completely. The mechanics model for assessing the fatigue life of shaft is set up. The assessment method of fatigue life for shaft is set up according to the traditional fatigue life estimation. The effect of wearing parameter to fatigue life is analyzed and the results show that the wear is an important factor to affect the fatigue life.
Effect of Cold Expansion on Crack Opening Displacement and Stress Intensity Factor
Authors: Liu Yong Shou , Gou Bing Wang , He Jie , Yue Zhu Feng
Published: October 2009

Two-dimensional (2D) finite element analyses have been carried out to study the crack opening displacement and stress intensity factor of a cracked centre-hole plate. With the different interference levels (2%, 4%, 6% and 8%) and acted by residual stress caused by cold expansion, the crack opening displacement, the stress intensity factor and J-integral around the crack tip is presented. With the different interference levels and acted by different applied loads , the crack opening displacement, the stress intensity and J-integral around the crack tip is also presented. The results of the 2D FEM analysis show, 1) with the different interference levels and acted by residual stress caused by cold expansion, the crack mouth is throughout closed and the middle part is open, but the opening displacement is constant; 2) under some applied loads, with the interference levels up, the stress intensity factor on the crack tip and J-integral, become weak gradually, then they keep constant values; 3) with the interference increases, the stress intensity factor and J-integral decreases. When the interference increases a certain value, the stress intensity factor and J-integral do not decrease and keep constant values.
Simulation of Delamination Using Discontinuous Galerkin Finite Element Methods and Cohesive Models
Authors: Stan Felicia
Published: October 2009

This paper presents a computational framework for simulation of delamination that combines the features of the discontinuous Galerkin methods with the versatility of the cohesive zone models. Within the finite element formulation of the discontinuous Galerkin methods, displacement discontinuities (jumps) are allowed across the element boundaries. Thus, the cracks are naturally included in the model without modifying the initial mesh. The displacement discontinuities across the element boundaries are used to compute the separations in the cohesive fracture law. The delamination initiation occurs when the traction across the element boundaries reaches its maximum; when the separation exceeds a critical value, total decohesion occurs. Numerical example is presented to illustrate the validity and effectiveness of the present methodology.
Cohesive Release Loads in a General Finite Element Model of a Propagating Crack
Authors: Fontana A. , Minotti M. , Salvini Pietro
Published: October 2009

High speed MODE I crack growth in elastic-plastic materials, involving large scale plasticity and dynamic effects connected to rapid propagation, is faced through a cohesive model to tune force nodal release. The stress resisting to the opening of the edges in the cohesive zone should account of effective stress field ahead crack tip. In this paper a reference value is accounted: it represents the maximum closing stress measured at the crack tip, where the cohesive effects begin.
A bi-parametric analytical formulation of stress distribution ahead the crack tip is suggested. The bi-parametric formulation is able to extrapolate the stress at the tip whatever is the T-stress (i.e. the stress acting in the direction of fracture propagation), thus completely defining the cohesive loads.
Size Effect of a Crack in a Micropolar Piezoelectric Medium
Authors: Huang Gan Yun , Yu Shou Wen
Published: October 2009

A crack problem in a micropolar piezoelectric solid is considered. By using simplified constitutive relations, the problem can be reduced to the solution of a set of Cauchy singular integral equations with the help of Fourier integral transform technique. Numerical results for stress intensity factors, couple stress intensity factors and electric displacement intensity factors show that micropolar theory can be expected to explain certain size effects in piezoelectric solids.
Fretting Damage of Contact Interfaces of CMSX 4 with and without T800 Coating
Authors: Lavella Mario , Botto Daniele , Gola Muzio M.
Published: October 2009

Fretting fatigue is a complex phenomenon that occurs at component interfaces undergoing low amplitude oscillation and high contact pressure. In turbomachinery fretting occurs also at the blade tip interfaces where shrouds are machined with the aim to reduce the blade resonant vibration amplitude. The aim of this study is to investigate the damage by fretting on CMSX4 superalloy interfaces with and without plasma sprayed T800 coating. The contact pair is a hemispherical surface on a flat surface. The hysteresis cycles, namely the contact force against the relative displacement, have been measured through the experiment. The worn surfaces have been characterized by three-dimensional optical interferometry and SEM analysis. After 3×106 and 10×106 fretting cycles the surface without coating shows surface cracks and large change in the contact parameters.
Damage Spectra for Performance Assessment of RC Bridges Subjected to Earthquakes
Authors: Zhao Guan Yuan
Published: October 2009

In this research, damage spectra to quantify the damage of reinforced concrete (RC) bridges under earthquakes are proposed. The spectra are computed for hundreds of horizontal ground motions recorded during past several earthquakes. The damage spectra proposed are promising for performance-based seismic assessment of existing RC bridges as well as performance-based design of new systems.
Fracture Analysis for Stiffened Aircraft Fuselage Subjected to Blast
Authors: Ju Jin San , Yao Xin Yu , Min Ding , Jiang Xiu Gen
Published: October 2009

This paper primarily presents the automation computational analysis techniques to determine the dynamic stress intensity factor for the stiffened damaged aircraft fuselage subjected to triangle blast load. 3-dimention panel models can be created using parameterization and the dynamic stress intensity factor can be obtained in the procedure of the blast automatically. A typical stiffened curved panel model which consists of 7 frames and 8 stringers is calculated. The calculation results show that the peak SIF value of the crack in the panel with strips under blast load is always smaller than that without strips for all longitudinal crack lengths; the strips can slow down the crack growth markedly and the effect of the strips on SIF is most obvious when the crack tips are close to the edge of strips; the blast load time has effect on the SIF peak value, and the effect is most significant when the load time is about 25 milliseconds for the panel with strips.
Effect of Partial Debonding on Response of Perforated Plates Repaired with Square Composite Patches
Authors: Rezaeepazhand Jalil , Sabori H.
Published: October 2009

The performance of perforated metallic plates repaired with laminated composite patches is presented in this study. A square aluminum plate with a central circular cutout is considered as a damaged structural element. Numerical studies using commercial finite element code were conducted to investigate the effects of variation in laminate parameters such as number of plies, fiber orientation, and stacking sequences on free vibration responses of the repaired plates. Particular emphasis is placed on the effect of imperfect bonding (patch debonding). A quantitative measure for the effectiveness of the composite patches parameters is taken to be the relative change in natural frequencies of the deboned patches compare to the patches with perfect bonding. The results presented herein indicated that, vibration response of a repaired perforated metallic plate is affected by the number of plies, stacking sequences of the patch and the quality of bonding between the patch and the base plate.
Deterioration and Thermographic Analyses of Electrical Units in Diesel Locomotive
Authors: Kim Jeong Guk , Baek Seung Koo , Lee Chang Young , Yoon Sung Cheol
Published: October 2009

The electrical units of diesel electric locomotives, which were used for over 30 years, were characterized for deterioration evaluation through insulation resistance measurement, degradation testing, and infrared thermography method. Especially, an infrared camera and thermocouples were employed for the evaluation. The thermocouples were attached on high-voltage cables connected to traction motors, for in-situ measurement of abnormal heating during test running. After test running, the thermographic images were obtained for the inspection of high-voltage cables using the infrared camera. The thermographic results were quantitatively analyzed, and compared with temperature changes during running. In this investigation, various analysis techniques for the safety characterization of diesel electric locomotives have been introduced, and the analysis results have been used to provide the deterioration or wear information in current locomotive systems.
Damage Tolerance in Civil Engineering Components: Implementation to an Anchorage
Authors: Gálvez Jaime C. , Elices Calafat Manuel , Olivares Miguel A.
Published: October 2009

The use of the damage tolerance concept is growing in the design of civil engineering structures. The aim of this paper is to provide some guides to help designing anchorages according to the damage tolerance concept. The paper shows the importance of the small defects, idealized like small cracks, in the structural integrity of these elements. The Stress Intensity Factors (SIFs) induced by small cracks in an anchor head of post-tensioned strand anchorage system are calculated. The study includes the evaluation of the influence of the shape of the anchor head on the SIF. The numerical predictions are compared with experimental results of ½ scaled specimens of Poly-methyl-methacrylate (PMMA).
Destructive Tests for the Determination of Masonry Performance
Authors: Nobile Lucio , Gentilini Cristina , Bartolomeo Veronica , Bonagura Mario
Published: October 2009

Several masonry panels are studied by means of destructive tests such as compressive, diagonal compression and shear-compression tests. The experimental research allows to characterize the mechanical properties of masonry walls in order to assess the masonry performance. Moreover, a brief recall of the most important experimental progress is presented in order to understand the state of the art of the research in the field of destructive tests.
Fatigue Behavior of Ni-Ti Alloy Endodontic Files under Ultrasonic Unconstrained Condition
Authors: Zhou Hui Min , Li Qing Fen , Zheng Yu Feng , Li Li
Published: October 2009

Nickel-titanium alloy are extensively used in engineering and biomedical fields for their excellent properties of shape-memory, super-elasticity and biocompatibility. Their fatigue performance has been attracted increasingly attention, because they are often used under cyclic conditions. In this paper, the ultrasonic fatigue behavior of nickel-titanium endodontic files under unconstrained condition has been studied using the self-designed ultrasonic fatigue testing equipment. The vibration and harmonious response properties of nickel-titanium endodontic files are also analyzed using finite element method. Experimental results show that the average ultrasonic fatigue life of nickel-titanium endodontic files under unconstrained conditions is more than 108. Fracture of the files always occurred at the position about 2 -3 mm near the file tip. Results of finite element analysis show that the maximum stress of the nickel-titanium endodontic files located at the position about 2 -3 mm near the file tip, where is prone to generate fatigue cracks. The results of finite element analysis are consistent with the experimental results. The scanning electronic microscope (SEM) results show that the ultrasonic fatigue cracks always initiated at the surfaces of the files, where the secondary phases or impurities existed and induced fatigue cracks under repeated stress.
Deep Cryogenic Treatment: Effects on Mechanical Properties of AISI 302 Stainless Steel and 18NiCrMo5 Carburized Steel
Authors: Baldissera Paolo , Delprete Cristiana
Published: October 2009

In this paper, the influence of deep cryogenic treatment (DCT) on mechanical properties of two commercial steels is analysed. Hardened AISI 302 stainless steel and 18NiCrMo5 carburized steel specimens were subjected to DCT after standard treatments. For both materials, the fatigue behaviour is a key property considering their usual applications requirements. Surface hardness, tensile properties and axial fatigue resistance of both materials were measured and compared with and without DCT. From the analysis of the experimental results and from their interpretation in the light of the previous literature, some useful indications are obtained about the DCT potential fallout on design and construction of structural components.
On Crack Propagation of I-II Mixed Mode Fracture in Concrete by Means of Photoelastic Coatings
Authors: Dong Wei , Wu Zhi Min , Zhao Yan Hua , Yi Fu Min
Published: October 2009

Investigation on crack propagation is important to understand mechanical behaviors and fracture mechanism in concrete. Till now substantial work has been done on crack propagation under mode-I loading, and mixed-mode fracture mechanics problems, however, are more common for actual crack growth. This study aims to systematically investigate the crack initiation, stable propagation and unstable failure of concrete under I-II mixed mode condition by using photoelasticity technique. For this purpose, reflective photoelastic coatings were applied to the surface of the four-point shearing notched concrete specimens with the maximum size of 2500mm×600mm×200mm. The resulting interference fringe on photoelastic coatings was recorded to reflect a complete crack propagation process. Based on the colored strain sequence, the strain profile around the crack tip could be determined and thereafter the load-crack extension curve. Then finite element analysis was performed to simulate the process of crack propagation and corresponding stress intensity factors were solved for every step. Experimental results show obvious stable crack propagation in concrete before unstable failure under I-II loading condition. The conventional failure criterion with the absence of this stable propagation quantity is therefore conservative. Besides, the fracture mode is ultimately I-mode even the specimen is subjected to I-II mixed mode loading condition, that is, the crack will extend in a direction perpendicular to the peak principal stress.
An Earthquake Loss Assessment Method to Buildings in Urban Zones and Its Application in Wenchuan Ms8.0 Great Earthquake
Authors: Sun Bai Tao , Chen Hong Fu
Published: October 2009

The national standard《Post-earthquake field works Part 4: Assessment of direct loss》 (GB 18208.4-2005) has been playing an important role in earthquake loss assessment, relief organization and homeland rehabilitation since it was issued in 2005 in China. The earthquake losses assessed are much less than other natural disasters (such as floods, drought) or foreign earthquake losses. How to assess seismic economic loss reasonably has been a key issue domestic seismic workers concern. In this paper, an earthquake-induced building decoration loss assessment method for urban zones is presented firstly. Then, based on statistical analysis of collected more than 600 pieces of cost data and 30 pieces of expert questionnaires, the distribution proportion of moderate–and–high–grade decoration building, the proportion of decoration cost and total structure cost, the loss ratio of decoration damage in small, Medium and big cities are given, respectively. The correction coefficients are also given depending on different economic development and use. Finally, its practical application in Sichuan Wenchuan Ms8.0 great earthquake loss assessment is introduced. Thus, some references and basis for further modifying and perfecting earthquake loss assessment standard in China are provided.
Analysis of Freeze-Thaw Damage of Lightweight Aggregate Concrete
Authors: Mao Ji Ze , Ayuta Koichi , Qi Hui , Liu Zong Min
Published: October 2009

Since lightweight aggregate usually accounts for a higher percentage of the concrete by volume, the properties of lightweight aggregate can significantly influence the properties of the resulting concrete. In this study, we investigated the effects of the water content of lightweight coarse aggregate (LCA) on freeze-thaw resistance of lightweight aggregate concrete (LC) and analyzed how to control the fatal frost damage - cracks in LC. The results showed that the freeze-thaw resistance of LC was determined by the water content of LCA. It is clear that lowering the water content of LCA below 17% is the key method to secure the freeze-thaw resistance of LC. The study showed that the higher the water content of LCA, the higher the weight loss and the larger pore volume of LCA, the bigger the length expansion and the lower the durability factors of LC after freezing and thawing. Internal cracks occurred only in the concrete specimens that contained LCAs with higher water content when subjected to freezing and thawing. Expansion pressure occurred easily in the higher water content LCAs and micro-cracks formed initially in the weak grains. Then micro-cracks enlarged and spread to the mortar as the number of freeze-thaw cycles increased. This process eventually caused LC expansion and damage.
The Microstructure Evolution in Fused Region and Taper Region of Fibre Coupler
Authors: Shuai Ci Jun , Peng Shu Ping , Qi Hu An , Qiu Qing Jun
Published: October 2009

The fused region and the taper region of the optical fibre coupler were tested by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The results indicated that the surface roughness increased after fused biconical taper (FBT), that is, the fused region possessed the highest toughness (about 70nm), the taper region is in a second position (about 40nm), and the bare fibre was relatively the lowest (about 10nm). Micro crystals were observed at the fused region and the amount of the micro crystals decreased with increasing the drawing speed. Micro cracks were observed at the taper region and the micro cracks became wide and deep with increasing the drawing speed. All these changes affected not only the optical performance such as excess loss and consistence, but also the reliability and stability. Therefore a fibre device with high quality required small drawbacks.
Stress Concentration Positions Determination of Ferromagnetic Material Based on Magnetic Test Method
Authors: Yu Feng Yun , Zhang Jing Chong
Published: October 2009

The magnetic field of ferromagnetic components under service load and geomagnetic field increases is induced by the residual magnetic induction and spontaneous magnetization. The stress concentration positions can be determination by detecting the magnetic field and the fracture can be avoided. The magnetic intensities of the demagnetized samples are tested by metal magnetic memory test method. By tensile test, the relationship between the magnetic memory signals and tensile load is studied, and the metal magnetic memory characteristics of the demagnetized samples under condition that the load keeps a fixed value are obtained. The test result indicates that the magnetic intensities of the samples change greatly after demagnetized; the change of the magnetic intensity of each test point are much different with different tensile displacement; in the later period of hardening phase and necking phase, the magnetic intensity about the side of the stress concentration positions increases along with the increasing of tensile displacement, however that of the other side decreases, that is the gradient of Fracture position increases obviously. Basing on this result by testing the parts of components emphatically where the fatigue failure and breakdown appear easily, the abrupt accident can be avoided.