bluuebunny/crossref_metadata_2025 huggingface dataset:
High Temperature Fatigue Behavior of 23Cr26Ni Heat Resistant Steel
Authors: Lee Hee Woong , Kwun S.I. , Jung Woo Sang
Published: November 2010

The influence of the cooling condition after solution treatment on the high temperature fatigue resistance of 23Cr-26Ni heat resistant steel was investigated. Two different cooling conditions were applied to the steel after solution treatment at 1230oC for 3 hours. One specimen was water quenched immediately after the solution treatment. The other one was furnace cooled at a rate of 0.5oC/min down to 750oC after the solution treatment. Then, both specimens were aged at 750oC for 5 hours. The low cycle fatigue (LCF) test was conducted to investigate the influence of high temperature on the LCF behaviors of the heat-resistant 23Cr26Ni alloy. Under two different heat treatment conditions, the LCF test was performed at total strain amplitudes ranging from ±0.4~0.9% at room temperature (RT) and 600°C. During the test, initial cyclic hardening occurred at both experimental temperatures. This phenomenon was attributed to the increase in the dislocation density due to cyclic deformation, which resulted in the interaction between the newly created dislocations and precipitates. Cyclic softening was observed in the later stages of the LCF test at RT. The formation of precipitates and increase in the dislocation density were observed using TEM. Also, the XRD and EDS techniques were used to verify the type and composition of the precipitates.
Mixed-Mode Fatigue Characteristics of Composite/Metal Interfaces
Authors: Baek Sang Ho , Kim Won Seock , Jang Chang Jae , Lee Jung Ju
Published: November 2010

For most of structural failure in engineering structures , fracture often takes place due to a phenomenon called fatigue. Therefore, many studies about the effect of the various mode-mixities on fatigue characteristics have been performed. However, most of the former studies are about metal/metal interface or delamination of composite. In this study, the fatigue characteristics of a composite/metal interface are investigated. The fatigue tests were performed using single-leg bending (SLB) specimens bonded with composite and steel using co-cure bonding method. This paper focuses on the fatigue characteristics depending on different mode ratios (GⅡ/GT). The overall results obtained in this study show that the crack propagation rate increases with the mode Ⅱ loading component.
Generalized Linear Elastic Fracture Mechanics: An Application to a Crack Touching the Bimaterial Interface
Authors: Náhlík Luboš , Šestáková Lucie , Hutař Pavel , Knésl Zdeněk
Published: November 2010

In the contribution the limits of the validity of classical linear elastic fracture mechanics are extended to problems connected with failure of composite structures. The work is focused mainly on the case of a crack touching the interface between two different materials, two different constituents. The approach suggested in the paper facilitates the answer to the question what is the influence of particle (in particulate composite) or layer (in laminates) on crack propagation through bimaterial interface. Different composite (bimaterial) structures are considered: layered composites and composites reinforced by particles. The presented approach follows the basic idea of linear elastic fracture mechanics, i.e. the validity of small scale yielding conditions is assumed, and has a phenomenological character.
Mixed-Mode Delamination Failure of Z-Pinned Hybrid Laminated Composites
Authors: Ghasemnejad H. , Thomas V. , Hadavinia H.
Published: November 2010

The mixed-Mode interlaminar fracture toughness, GI/IIC, of z-pinned hybrid laminated composites is studied to investigate the effect of 3D-composites on the crack propagation resistance of delaminated composite structures. In this regard, the mixed-Mode interlaminar fracture toughness, GI/IIC, was measured using asymmetric double cantilever beam (ADCB) test method. The hybrid ADCB and z-pinned hybrid composite beams were laid-up from [G0/C0]4, [G0/C90]4, [G90/C0]4 and [G90/C90]4 to study the effect of z-pinning on the interlaminar fracture toughness. From the obtained results from test it was found that the resistance of z-pin fibres against the crack propagation in z-pinned hybrid composites can significantly increase the mixed-mode interlaminar fracture toughness.
Numerical Simulations on Shape Memory Effect of Shape Memory Polymer
Authors: Zhou Bo , Zhao Shi Cheng , Qi Hui , Zhou Li Min
Published: November 2010

Shape memory polymer (SMP) is being used in many engineering fields due to its shape memory effect and the advantages of large recoverable strain, excellent manufacturability, light weight, low cost and bio-degradability. Therefore it is of practical interest to investigate its thermo-mechanical behaviors. In this paper, a numerical simulation method is supposed to simulate the thermo-mechanical behaviors of SMP using the finite element software of MSC Marc, which is good at simulating the thermo-mechanical behaviors of viscous elastic material. The comparisons between the numerical results and the experimental results by Tobushi et al. illustrate the supposed numerical simulation method well describes the thermo-mechanical behaviors of SMP during the thermo-mechanical processes realizing shape memory effect.
A Model of Steel Frame for Simulating Connection Fractures
Authors: Liu Hong Bo , Xu Long Jun , Li Shuang , Shao Yong Song
Published: November 2010

Following the 1994 Northridge earthquake, widespread damages were discovered in welded steel moment frame buildings. In order to accurately simulate the typical seismic damage of welded steel moment frame structures, a new simplified model is proposed for performing seismic evaluation of welded steel moment frame structures. In this model, the slabs effect is considered, as well as the effects of the slip between slabs and steel beams, deformation of panel zone and connection fractures. Fracture toughness demands were evaluated in terms of the mode I stress intensity factor. The model was employed in simulation of seismic damage of Blue Cross Building which experienced fractured connections in the Northridge earthquake. It indicates that the model can accurately predict the earthquake response of welded steel moment frame structures and estimate the level of damage. The approach proposed in this paper has important meaning to the research on seismic damage of steel frame which may experience fractured connections.
Finite Element Fracture Mechanics Study of Web Connections with Tapered Beam Flange Plates
Authors: Liu Hong Bo , Xu Long Jun , Li Shuang , Shao Yong Song
Published: November 2010

Brittle fracture was identified in many of prequalified weld joints in steel moment frames in the 1994 Nothridge earthquake. Then analyses of response and damage mechanism of beam-to-column connections under seismic load were widely studied in the world, but few people conduct the research on seismic-resistant behavior of beam-to-column web connections. To quantify the variation of stress intensity factor to weld root flaw sizes beam-to-column web connections with tapered beam flange plates, detailed 3D finite element analyses is used to study fracture toughness requirements in beam-to-column web connections, considering the large deformation, large strain, bolts pretension, bolt contact-slide, as well as material harden and soften. Fracture toughness demands are evaluated in terms of the mode I stress intensity factor. The stress intensity factor is calculated through a J-integral approach. The fracture toughness demands are studied for the flaw on the top of the beam flange and the bottom surface, respectively. Results indicate that the likelihood of top flange fractures is smaller than that of bottom flange fracture. Stress intensity factor is not uniform and is largest in the edge of beam flange. The fracture toughness in the edge of beam flange for web connections with step beam flange plates is 15% less than that for tapered beam flange plates.
Biocompatibility and Medical Application of Carbon Material
Authors: Xu Wen Feng
Published: November 2010

Carbon composites have good mechanical properties and preserve the inherent excellent biocompatibility of carbon, which make them great potential as orthopedic implants in human body. The present work reviews the biocompatible behavior and research situation of such materials for medical application. The mechanical properties, interface and surface modification problem of carbon composites are discussed in detail. Finally, the medical prospects and some problems needed to be solved of carbon composites are put forward.
Analysis on Coupling Damage of Liquid Rubber Based Concrete under Fatigue and Impact Loading
Authors: Liu Yi Ping , He Ting Hui , Tang Li Qun , Huang Xiao Qing
Published: November 2010

In this paper coupling damage behaviors of Liquid Rubber Based Concrete (LRBC) are studied experimentally. Compressive fatigue and impact alternant loading tests were carried out on cylindrical LRBC specimens. The elastic moduli were recorded before and after fatigue and impact tests. The quasi-static compressive stress-strain curves after fatigue and impact tests were obtained. According to the definition of dissipated energy, the cumulating of dissipated energy was used to define damage. The analysis on impact and fatigue damages during the loading processes show that fatigue and impact loading lead to the formation and development of inner damage. During the alternant loading process, impact and fatigue damages are coupled mutually, with the former affects the evolution of fatigue damage evidently.
Analytical Solution of Elastic-Plastic Buckling of a Square Steel Tube Column under Axial Compressive Load and Bending Moment
Authors: Niu Peng , Yang Gang , Jin Chun Fu , Wu Yi Xiong
Published: November 2010

Based on Ježek method of computing the elastic-plastic buckling of the member under the axial compressive load and the bending moment, the analytical expressions of calculating the ultimate load of buckling about the neutral axis with the moment of inertia for a square steel tube column are derived. By degenerated into the analytical expressions of the rectangular column and compared with the values of the finite element analysis (FEA) method, it shows that the analytical method in this paper is valid, which provides a new method of theoretical study for the elastic-plastic buckling of the member.
Evolution of Aggregate Surface Characteristics in Polishing Process
Authors: Chen Xian Hua , Steinauer B. , Wang Da Wei
Published: November 2010

This paper aims to investigate the evolution of aggregate-surface characteristics due to tyre polishing action. Three kinds of aggregates were polished by the Wehner/Schluze polishing machine. The evolution of dynamic friction coefficient, surface height profiles and their power spectral density in polishing process were characterized. Spectrum analysis is conducted to characterization the polishing effects on surface texture. The results reveal that the polishing action of rubber tyre plays an important role in the changes of micro-texture, and the evolution of friction of aggregate is governed by micro-texture changes due to differential removal of mineral components.
A Study on the Fracture Test in Running System of Railway
Authors: Yoon Sung Cheol , Kim Jeong Guk , Park Sung Hyuk , Baik Kwang Sun , Choe Kang Youn
Published: November 2010

This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.
Local Buckling Analysis for Large Diameter Underground Jacked Steel Tubes under External Load
Authors: Jin Chun Fu , Yan Shi , Niu Peng
Published: November 2010

Densely arranged underground steel tube system (DAUSTS) is a new kind of structure which can be usually used in constructing spacious underground structures such as metro stations. During the construction, the steel tube is horizontally forced into soil by jacks through a vertical well. The tube may generate local buckling phenomena under the compression force if the parameter of the tube and soil meet the buckling condition. In the paper, the soil perturbation mode and the deformation of the tube before local buckling are both analyzed, considering the possibly concerned buckling failure modes in practical engineering, the confine effect of the soil and interaction between the tubes. A nonlinear buckling analysis on tube-wall of the steel tube located in the most unfavorable place is developed by the arc-length method of the finite element method (FEM), considering the effect of the large deformation. The results of the numerical simulation matches very well to the real application and the key results of the analysis can be used as an estimation principle for the stability of the tube.
Molecular Dynamics Simulations of Pre-Crack Effects on Deformation and Failure Mechanisms for Pure Aluminum
Authors: Chen Hua Yan , Zeng Xiang Guo , Xu Shu Sheng
Published: November 2010

Micro-cracks which seriously affect the strength of metal materials always exist in metal or alloys during the manufacturing process. In order to investigate the pre-crack effects on deformation and failure mechanisms for pure aluminum at atomic scale, the plastic deformation processes of pure aluminum with face-centered cubic (fcc) crystal structure around the pre-crack tips at atomic scale were examined by means of molecular dynamics (MD) method. The Modified Embedded Atom Method (MEAM) potential was used to describe the interaction among atoms of pure aluminum. The crack propagation and failure processes for fcc structure were observed near the pre-crack tip zone. The calculation results reveal that the pre-crack blunting occurred at first, then the dislocation emitted at the pre-crack boundary and moved along with the specific direction obviously, eventually, cracks propagated along the crystallographic direction family of <110>. By means of VMD software, the graphic pictures of dislocation movement and crack propagation were obtained under different load conditions. The results and methodology given in this study are very significant for understanding more about plastic deformation and destruction at atomic scale for pure Aluminum with fcc structure.
Finite Element Analysis of Embedded Parts with Big-Diameter Reinforcing Bar under Shear Force
Authors: Zhu Yao Guo , Wang Qing Xiang
Published: November 2010

Nowadays embedded parts which connect steel members with concrete structures have frequently emerged in civil engineering; however the existing design code for embedded parts cannot satisfy the increasing demand of engineering as it was derived from limited experiments. In the paper, a finite element study on embedded parts with big-diameter reinforcing bars under shear force is conducted. The aim of the study was to fully investigate the mechanical performances of embedded parts under shear force using a three-dimensional finite element analysis with the help of a commercial software ANSYS. Cross-section internal force of anchor bar, embedded part deformation, interaction force between anchor bar and concrete, and friction force were investigated in order to well know the system response. The results show that the shear capacity of embedded part obtained from finite element analysis is conservative.
Comparative Analysis of Seismic Damage of the Earthquake Fortification and Non-Earthquake Fortification Masonry Buildings
Authors: Zhou Qiang , Sun Bai Tao , Yan Pei Lei
Published: November 2010

In this paper, the typical seismic damage of earthquake fortification and non-earthquake fortification masonry buildings are analyzed and the causes are illustrated, which are based on a large number of earthquake disaster survey data of Ms8.0 Wenchuan earthquake, Ms6.4 Baotou earthquake and Ms7.8 Tangshan earthquake and so on. According to the damage statistics data of several past earthquakes of China in recent years, the difference of damaging phenomenon and rate of earthquake damage of earthquake fortification and non-earthquake fortification masonry buildings in highly and lowly seismic regions are discussed and analyzed. Finally, based on the analysis conclusions, how to improve the seismic capacity of masonry buildings are discussed combining current seismic design code of China and some reasonable suggestions on the post-disaster reconstruction of masonry buildings have been given.
Typical Seismic Damage Analysis of the Single-Story Reinforced Concrete Industrial Buildings in Hanwang Town in Wenchuan Earthquake
Authors: Sun Bai Tao , Zhou Qiang , Yan Pei Lei
Published: November 2010

The Wenchuan earthquake occurred on May 12, 2008 (Beijing Time) caused great economical loss and large amount of buildings were destroyed. Many of single-story reinforced concrete industrial buildings in Hanwang town located in the highly seismic region were damaged, and the damaging phenomenons are very typical. According to the damage survey and analysis of typical seismic damage for the single-story reinforced concrete industrial buildings located in Hanwang town, the damage distribution and failure characters of these buildings are summarized in this paper. The single-story reinforced concrete industrial buildings which were designed according to current seismic design code have better earthquake resistant behavior than those old single-story reinforced concrete industrial buildings and the damaging phenomenon show some new features. Finally, combining current seismic design code of our country and the earthquake damage lessons, some reasonable suggestions on the work of seismic strengthening and earthquake resistant design of the single-story reinforced concrete industrial buildings have been given.
Experiment Research of Environment Effects on Fatigue Life of Carbon/Bismaleimide Composite Laminates with Central Hole
Authors: Zhang Jian Yu , Sun Chong Qiang , Zhao Li Bin , Peng Lei , Fei Bin Jun
Published: November 2010

The effects of humidity and ultraviolet radiation aging on fatigue properties of carbon/ bismaleimide composites and coating protection action were presented. Specimens with central hole are made of carbon/bismaleimide laminates. Compression-compression (C-C) fatigue tests under normal lab environment were operated respectively for four groups of specimen, (1) specimen under normal lab environment, (2) specimen under UV radiation aging with dryness, (3) specimen under UV radiation aging with moisture, and (4) specimen with coating under UV radiation aging with moisture. Variance analysis of experimental outcomes gave significances of the environment effects on C-C fatigue life of specimens. The results reveal that UV radiation have remarkable effects on the C-C fatigue life of the composite laminates under the same humidity, whereas combined action of UV radiation (300MJ/ m2) and humidity have no significant effects on the C-C fatigue life. Coating can provide effective protect the specimen from UV radiation aging.
Influence on Scattering of SH-Wave by Surface Ground Isosceles Triangular Hill in Right-Angle Plane with Circular Cavity
Authors: Jing Guo , Qi Hui , Yang Jie
Published: November 2010

The analytical solution to the problem of the scattering of SH-wave by isosceles triangular hill near the subsurface cavity in right-angle plane is given by using the idea of match up. Firstly, wave function was constructed by using the methods of complex function, multi-polar coordinate transformation and superposition principle, which satisfied the stress free boundary conditions at the free surfaces for the right-angle plane possessing a circular cavity. Secondly, transform the wave field from the right-angle plane to the half space by using the method of mirror image in order to obtain the total wave filed, which satisfied the boundary conditions. Finally, based on the conditions of the displacement continuity and stress continuity at the “common border” and the stress free condition at the subsurface cavity edge, a series of infinite algebraic equations were given and solved by truncation. Meanwhile, some examples and results are given and discussed.
Finite Element Analysis of Creep and Thermal Stress for Shape Memory Alloy Joint
Authors: Zhou Xue Feng , Zhi You Hai , Gou Bing Wang
Published: November 2010

The three-dimensional (3D) finite element model of shape memory alloy (SMA) joint system under a clamped-clamped support was established. Using the coupled thermal-mechanical transient state analysis, stress distributions of models under the different loads (internal pressure, temperature) were investigated. And the temperature field, thermal strain field, stress and creep of the joint system were obtained. The results show, 1) for the non-coat SMA joint system, the interface in middle region of the joint’s internal wall is the dangerous region. In this region, the joint’s adhesion failures easily occur and the crack easily initiate. The joint’s coat can improve the fatigue life of joint system. 2) There are higher levels of radial temperature gradient, temperature strain and temperature stress between the internal and external walls of the joint. The creep strain in the internal-external walls of the joint is the main reason for adhesion failure in middle interfaces between the joint and the pipe.
Fatigue Test and Stress Analysis of Threaded Connection of Arch Bridge Stainless Steel Suspender
Authors: Song Yu Pu , Liu Han Yong
Published: November 2010

This work presents a study of a fatigue test and a finite element analysis on an arch bridge stainless steel suspender with threaded connections. A suspender which had a diameter of 70mm was tested under axial tensile loads range from 430kN to 700kN. The suspender was sudden failure from the thread root of the first loaded tooth in the pin after 1546609 cycles. Then, a two-dimensional axisymmetric modeling ignoring the helix angle of the thread was established with finite element software ANSYS to perform a stress analysis of the threaded connection. The stress concentration factors (SCFs) at the root of the teeth of pin were investigated under the applied external loading. The conclusive results had been drawn from the analysis including the location and the value of maximum SCF in the pin. Finally, the location and the value of the maximum von Mises stress were given. The results showed that the location of the fracture surface was consistent with the location of the maximum von Mises stress.
Effect of Micro-Climatic Condition on Durability Performance of Concrete
Authors: Yoon In Seok
Published: November 2010

The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the topic have been accomplished, however, it is not easy to review literatures about environmental analysis, in particular micro-climatic condition of concrete under chloride laden environment. Since the durability of concrete depends on the properties of the surface concrete, micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The outcome will be combined with modules of material parameters such as chloride diffusivity, surface chloride content, and so on. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete at atmospheric zone or tidal zone.
Evaluating Damage of Concrete with Nonlinear Ultrasonic and Acoustic Emission Techniques
Authors: Shah Abid A. , Al-Salloumrs Yosef A. , Al-Syed Saleh H.
Published: November 2010

In this research, the non-linear ultrasonic and acoustic emission techniques were used to evaluating damages induced in concrete under compression loading. Cubic concrete specimens were produced with three different w/c. The nonlinear ultrasonic evaluation was based upon measuring the change in fundamental amplitude with increasing damage and output power level. In acoustic emission testing technique 4 sensors were used to record the AE events under various loading and unloading cycles. An increase in AE hits was observed with increasing damage. Since concrete contains microcracks even under initial loading stages, none of the test specimens exhibited clear signs of the occurrence of Kaiser Effect. Normalized values of Felicity Ratio were plotted and compared with the nonlinear ultrasonic test data. A correlation between acoustic emission and nonlinear ultrasonic techniques in assessing damage growth in concrete was investigated.
Experimental Investigation of Damage Characteristics in Steel Honeycomb Sandwich Beams
Authors: Lu Jie , Zou Guang Ping , Liu Bao Jun
Published: November 2010

In this work the fracture process of steel honeycomb sandwich beams has been investigate by situ acoustic emission(AE) technique. Pre-cracks were made both for L-direction and W-direction specimens subjected to out-plane three-points bending loads. Damage initiation sites were observed in the vicinity of the crack tip. A series of curves among the AE counts, AE hits, AE amplitude, AE energy and loading time were obtained. Damage characteristics were discussed based on the above parameters. The results indicate AE characteristic parameters can reflect the damage and failure process of specimens. A good agreement was found between the experimental and analytical results.
Compensation of FSI Analysis to Develop an Alarm System for a Container Crane
Authors: Han Dong Seop , Jang Hyo Pil , Han Geun Jo
Published: November 2010

This study is conducted to provide a compensation formula to design the stowing devices - a tie-down rod and a stowage pin - and an alarm system to prevent an overturning of a container crane under wind loads. Two method, namely FSI(fluid-structure interaction) analysis and wind tunnel test, are adopted in this investigation. In order to evaluate the effect of wind load on the stability of the crane, 50-ton class container crane widely used in container terminals is adopted for analytic model and 19-values are considered for wind direction as design parameter. First, the wind tunnel test for the reduced scale container crane model is performed according to the wind direction using an Eiffel type atmospheric boundary-layer wind tunnel. Next, FSI analysis for a full-scale container crane is conducted using ANSYS and CFX. Then, the uplift force obtained from FSI analysis is compared with that yielded by the wind tunnel test. Finally, a formula is suggested to compensate the difference between the FSI analysis and the wind tunnel test.
Damage Development in Hybrid Composite Laminates under Three-Point Bending at Cryogenic Temperatures
Authors: Miura Masaya , Shindo Yasuhide , Takeda Tomo , Narita Fumio
Published: November 2010

This paper studies the damage behavior and interlaminar shear properties of hybrid composite laminates subjected to bending at cryogenic temperatures. Cryogenic short beam shear tests were performed on hybrid laminates combining woven glass fiber reinforced polymer (GFRP) composites with polyimide films, and microscopic observations of the specimens were made after the tests. A progressive damage analysis was also conducted to simulate the initiation and growth of damage in the specimens and to determine the interlaminar shear strength based on the maximum shear stress in the failure region. The predicted load-deflection curve and damage pattern show good agreement with the test results, and the numerically determined interlaminar shear strength is higher than the apparent interlaminar shear strength.
Towards a Model for Fresh Granular-Paste Systems Based on Discrete Element Method
Authors: Hoornahad H. , Koenders Eddy A.B. , van Breugel Klaas
Published: November 2010

Modelling the rheological behaviour of fresh granular-paste systems is the main aim of this study. The research approach is based on a conceptual idea where the paste-interaction system is explicitly modelled by an interactive two phase particle system. As a first approach the cohesive force-displacement interaction was measured for two ideally shaped glass particles bridged by water. Later on, the water was replaced by cement paste and the attraction force acting on the glass particles was measured for increasing inter-particle distances. The results gave a very good impression of the cohesive forces acting on a granular paste system employed by the cementations material in its fresh state. The Discrete Element Method (DEM) is one of the computational techniques that is applied to simulate the granular-paste system. With this method, the fresh granular-paste system is divided into two phases (aggregate/paste) and is modelled by a single-phase or a double-phase system of DEM elements. At the first step, the interaction forces of the particle-paste system are compared with the experimental results achieved from the particle-liquid measurements and expressed as an explicit function based on local geometrical and physical parameters. Modelling and experimental results show good agreement.
Numerical Simulation of Stress Corrosion Cracking in a Pipe Using S-Version FEM
Authors: Kikuchi Masanori , Wada Yoshitaka , Shimizu Yuto , Li Yu Long
Published: November 2010

Fracture in heat affected zone (HAZ) in welding has been a serious problem for the integrity of machines. Prediction of fracture behavior due to the residual stress field in HAZ is important. In this paper, S-Version FEM(S-FEM) is applied to simulate the crack growth under thermal and residual stress fields. For evaluation of stress intensity factor, virtual crack closure integral method (VCCM) is employed. The residual stress data was provided by JAEA, Japan Atomic Energy Agency, based on their numerical simulation. SCC crack growth of a surface crack at inner suface of a pipe under thermal residual stress is simulated in three-dimensional filed. Distributions of residual stress is not axi-symmetric along pipe wall, and it affects the crack growth behavior. Ttwo cases, for axi-symmetric and non-symmetric thermal stress distributions, are assumed and crack growth behaviors are obtaiend and discussed.
Three-Dimensional Micro Flow-Stress-Damage (FSD) Model and Application in Hydraulic Fracturing in Brittle and Heterogeneous Rocks
Authors: Li G. , Tang C.A. , Li L.C.
Published: November 2010

In order to investigate the hydraylic fracture development of the specimens and simulate the cracks drived by fluid flow in rocks, a flow-stress-damage (FSD) model, implemented with parallel Rock Failure Process Analysis code (parallel -RFPA3D), is presented. The numerical code is based on linear elastic damage mechanics on mesoscopic scale and FEM. For simulating the complete progressive 3D failure and macroscopic mechanical behaviors of rock materials, rock properties such as elastic constants, peak strength, and poisson ratio are randomly distributed to reflect the initial random distributed weakness in mesoscopic scale. The FSD model is used to represent the permeability variation at the two stages, that is stress-dependent permeability for pre-failure and deformation-dependent permeability for post-peak stage of rock at the elemental scale. The results of the simulation with 680,000-element cylindrical rock specimen coincide well with reported experimental results and the process of crack from initiation to the instability extensions is captured vividly. The results and the process indicate that the FSD model works well and parallel-RFPA3D incorporated with FSD model is a valid tool of understanding the physical essence of the evolution of fracture with large-scale elements and fluid flows in rocks.
An Analysis of Non-Uniform Deformation of a Pantograph for Bellows Applications
Authors: Kim Jae Hyun , Jang Bong Kyun , Kim Kyung Shik , Kim Jung Yup , Choi Byung Ik , Jun Sang Hyun , Kim Jun Ho
Published: November 2010

In this study, an analytical model is developed to analyze non-uniform deformation of a pantograph. The analytical model is verified by comparing predicted deformations with experimentally measured deformations of a pantograph. The effects of total displacement and gaps on non-uniformity are numerically simulated to provide the physical insight into the deformation mechanism of a pantograph. Design guidelines are suggested to minimize non-uniform deformation of a pantograph, and hence also of an associated bellows.
A Numerical and Experimental Study of the RCF Behaviour of PVD-Coated Spur Gears
Authors: Baragetti Sergio , Cavalleri Stefano , Tordini Federico
Published: November 2010

In this work the rolling contact fatigue (RCF) behaviour of WC/C PVD-coated and uncoated case hardened transmission gears for competition motorcycles was studied both numerically and experimentally. Finite element models of the gears were processed and a theoretical-numerical procedure was applied to the numerical results to predict their RCF life. The presence of the coating and the residual stress fields induced by the surface treatments were simulated. Besides 16NiCr11, which is the actual material of the gears analyzed, the Ti-6Al-4V alloy was also considered with the numerical models. Preliminary RCF tests were carried in both dry and lubricated condition to observe the damage on the tooth flanks with and without the presence of the coating.
Analysing of Regularity Microseismic Technique for Warning Fractured Water Inrush in High-Head Mine Curtain
Authors: Liu Chao , Tang Chun An
Published: November 2010

In search for detecting the working status of curtain under high-head condition, finding fracture extension zone around curtain while the mine was extracted, particularly, pointing out possibly water inrush passageway along curtain mining sides. Microseismic monitoring system was established to monitor real-time and continuous microrupture of curtain region by the advanced mining dynamic disaster monitoring equipment in the Zhangmatun iron mine,and combining with the water amount changes at every mining levels and different observating holes, judging comprehensively the stability in curtain region. The monitoring results show that the two obvious fracture extension zones were found along curtain mining sides, diffusing distribution showed ray state from curtain inside to outside, the pit inflow of water was bigger than other site in this two regions, both microseismic monitoring and water amount changes results were anastomosous relatively. The fracture was developed in this two regions, the hydraulic relationship was also close, and the water inrush accident may occur, so the reinforcing curtain and plugging water inrush passageway should be took timely.
Effects of Torsional Plastic Deformation on Fatigue Strength in Copper and Aluminum
Authors: Makabe Chobin , Kuniyoshi K. , Fujikawa Masaki , Kondou Ryouji , Shinohara D.
Published: November 2010

If the crystal grain size of a metal is made smaller, its strength is higher. So, many methods of grain refinement have been proposed. In this study, from the viewpoint of basic plastic working, the variations of static ultimate tensile strength and fatigue strength after the application of plastic torsional deformation on face centered cubic crystal metals, that are, aluminum and copper, were investigated. Tensile test, Vickers harness test and Rotating bending fatigue test were performed. The hardness of the materials varied from surface layer to center section in cross sectional area. In the case of aluminum, the tensile strength and fatigue limit were improved after application of torsional deformation. However, in the case of copper, the fatigue limit was not improved. This is strongly related to hardness distribution around the surface layer of the specimen. Also, it was found that the crack growth mode was changed by applying the pre-strain. From these results, one of an idea for improvement of material strength will be considered.
Hole Expansion by Using Al-Alloy Specimen and 0.45% Carbon Steel Specimen
Authors: Rana Muhammed Sohel , Ferdous Md. Shafiul , Makabe Chobin , Fujikawa Masaki
Published: November 2010

The enhancement method of fatigue life and the crack initiate and growth behavior of a holed specimen was investigated by using the 2024 Aluminum alloy and 0.45% Carbon steel. The purpose of present study is to propose a simple technical method for enhancement of fatigue life in a notched specimen. Also, the effect of local plastic deformation by cold work on fatigue crack initiation behavior was examined. This paper presents a basic experimental kinematic cold expansion method by inserting and removing a pin through the specimen hole. The shape of cross-section of pin was a circle or an ellipse. It was shown that the fatigue life of the specimen with the cold-worked hole was longer than that of the specimen with non-cold-worked hole for the case of same stress level in aluminum alloy and carbon steel. Also, the fatigue strength was higher in the case of the cold expanded hole. In this study, a methodology of lengthening of fatigue life of holed specimen is shown. Also, the improvement conditions of fatigue life were significantly affected by shape of pin, local hardening and residual stress conditions. The fatigue life improvement of the damaged component of structures was studied.
Fatigue Life Prediction Based on FS Criterion for Multi-Axial Loading
Authors: Jin Dan , Fu Hai Ling , Lin Wei
Published: November 2010

The Fatemi–Socie criterion is evaluated using the combined axial torsion fatigue testing results obtained from extensive experiments on thin-walled tubular specimens made from 304 stainless steel. The Fatemi–Socie criterion combines the maximum shear strain amplitude with a consideration of the normal stress on the critical plane. Rainflow cycle counting and Morrow’s plastic work interaction rule are used to calculate fatigue damage. The fatigue life prediction is conducted by using the maximum shear strain plane as the critical plane by considering the weight function and the maximum damage plane as the critical plane. It is concluded that the results gained by two approaches are both acceptable for the case examined.
Fatigue Characteristics of Bolted Joint under Transverse Vibration ~Influence of Bolt Tightening Conditions on Transverse Fatigue Strength~
Authors: Hashimura Shinji , Kurakake YU , Umeno Shinichi
Published: November 2010

Fatigue tests under transverse vibration were performed for three separate tightening conditions to investigate the grip length and the engaging thread length in this study. The relationships between the apparent fatigue limit (the highest amplitude of transverse vibration force which can be applied to the bolted joint without generating fatigue) and the real fatigue limit of bolt material also were investigated. Results showed that apparent transverse fatigue limit decreased if the grip length was long. And relationships of the apparent fatigue limit and the real fatigue limit were different in each tightening conditions depending on the bending moment at the root of the first thread.
Flexural Behavior of Void RC and PC Slab with Polystyrene Forms
Authors: Kim Seung Hun
Published: November 2010

Where the self weight of the overall RC(Reinforced Concrete) or PC(Precast Concrete) floor system needs to be considered, the quantity of in-situ concrete required can be reduced by the application of polystyrene void forms to slab. In this study, flexural behaviors of void RC and PC slab with polystyrene form were evaluated to understand the effect on the self weight reduction of the slab. This paper presents experimental works and finite element analysis on the bending of the void slabs. Six specimens were tested. The main parameters of experiments were the slab types (RC and PC), the types and arrangement details of polystyrene form, and the thickness of slab. Structural behaviors of void slabs were evaluated on the basis of failure mode, load-displacement curve, and ultimate strengths. Test results indicated that nominal strengths by ACI code agreed well with experimental results. The results of analysis were compared with the results of test for estimating the validity of analysis model.
A Constitutive Model for Ductile Damage Evolution
Authors: Wallin Mathias , Ristinmaa Matti , Olsson Mattias
Published: November 2010

A constitutive model for ductile porous material is formulated within the thermodynamic framework. A yield function based on the lower-bound solution for a cylindrical void model embedded in a plastic matrix is proposed. The new yield function is compared to the classical Gurson yield function using cell model calculations. The results reveal that the proposed yield function agreed well with the plastic region found from the cell model calculations.
In addition to the influence of the void-volume ratio, the elastic part of the free energy is dependent on a scalar damage field which allows the elasticity to be influenced by the void-volume fraction. The degradation is controlled by a scalar valued damage field and enters the formulation via the Helmholtz's free energy. This dependence allows the elastic properties to naturally depend upon the damage accumulation. The numerical treatment of the model is derived and the capability of the model is demonstrated via numerical simulation of the necking of an axi-symmetric bar.
Analysis of Crack-Tip Field of Particulate-Reinforced Composites Taking Account of Particle Size Effect and Debonding Damage
Authors: Fujii Tomoyuki , Tohgo Keiichiro , Itoh Yu , Kato Daisuke , Shimamura Yoshinobu
Published: November 2010

This paper deals with an analysis of a crack-tip field of particulate-reinforced composites which can describe the evolution of debonding damage, matrix plasticity and particle size effect on deformation and damage. Numerical analyses were carried out on a crack-tip field in elastic-plastic matrix composites reinforced with elastic particles by using a finite element method developed based on an incremental damage theory. The particle size effect on damage is described by a critical energy criterion for particle-matrix interfacial debonding. The effect of debonding damage on a crack-tip field is discussed based on numerical results. The debonding damage initiates and progresses ahead of a crack-tip. The stress distribution shifts downward in the debonding damage area. It is concluded that a crack-tip field is strongly affected by debonding damage.
Crack Width Analysis of Reinforced Self-Compacting Concrete Beams
Authors: de Corte Wouter , Boel Veerle
Published: November 2010

Self compacting concrete is a concrete mixture specifically designed not to require external energy for compaction. This property results in many advantages for precast as well as ready-mix concrete applications. Especially, dense reinforcements or slender elements can be achieved. However, in current design codes this concrete is treated as traditional concrete although the mix composition is substantially different. Due to a decrease in coarse aggregates, combined with a higher amount of chemical and mineral admixtures, the overall mechanical behavior may differ from that of traditional concrete even when the compressive strength of both mixtures are equal. This is especially visible in the crack formation in the tensile zone of concrete beams. This paper presents results of an analysis of crack formation, distribution and width on reinforced concrete beams with varying reinforcement ratios. Differences in crack properties, favoring self-compacted over traditional concrete are found for all considered reinforcement ratios, although the results are less pronounced for the higher ratios. The results may allow a favorable serviceability limit state criteria for this material.
Fatigue Properties of Dynamically Loaded Self-Compacting Concrete
Authors: de Corte Wouter , Boel Veerle
Published: November 2010

Many civil structures are subjected to dynamic loading with load cycles exceeding 100.000 to 100.000.000 or more depending on the type of structure. At such high amounts of load cycles concrete can fail due to fatigue damage. The phenomenon is well understood and documented in the literature for traditional concrete. It remains unclear whether these conclusions can be transferred to self-compacting concrete (SCC), due to changes in concrete composition, decrease in the size of the coarse aggregates in combination with the addition of filler and superplasticizer. For this paper several reinforced concrete beams with varying reinforcement ratios are subjected to dynamic loads in a four point bending rig until failure. The imposed stress levels for the dynamic loading range between 0,80fcc and 0,85fcc. The main conclusions of the experimental tests are (1) clearly different failure mechanisms determine the static and dynamic loading for a single type of beam, (2) SCC appears to have a somewhat lower shear resistance during fatigue, (3) the differences in flexural degradation between SCC and TC beams are rather small.
Modeling of Crack Behavior in Austenitic Steel Influenced by Martensitic Phase Transformation
Authors: Hallberg Håkan , Ristinmaa Matti
Published: November 2010

A thermomechanically coupled constitutive model for finite strain elasto-plasticity is formulated and numerically implemented. The model gives a physically sound description of an initially austenitic material influenced by martensitic phase transformation. The heat dissipated by plastic slip deformation and by phase transformation is allowed to influence the material behavior and appears as a key influencing factor on the growth of the martensitic phase. The model is calibrated using a common stainless steel as prototype material, allowing numerical simulations of crack propagation to be performed. Alterations of the crack growth behavior are observed as different simulation scenarios are compared.
The Relationship between Shear Bands and Crack Growth Behavior in Ultrafine Grained Copper Processed by Severe Plastic Deformation
Authors: Goto Masahiro , Han S.Z. , Yokoho Yuji , Nakashima Kazuya , Kim S.S. , Euh Kwang Jun
Published: November 2010

Fatigue life of smooth specimens is approximately controlled by the growth life of a small crack. This means the growth behavior of small cracks must be clarified to estimate the fatigue life of plain members. However, there are few studies on the growth behavior of small cracks in ultrafine grained (UFG) metals. In the present study, fatigue tests for UFG copper have been conducted. The formation behavior of shear bands (SBs) and growth behavior of a small crack have been monitored to clarify the effect of SBs on the growth behavior of a major crack.
Fracture Analysis and Fatigue Remaining Life Prediction of Concrete Structural Components Accounting for Tension Softening and Size Effects
Authors: Murthy A. Rama Chandra , Palani G.S. , Iyer Nagesh R.
Published: November 2010

This paper presents methodologies for fracture analysis and fatigue remaining life prediction of concrete structural components with and without accounting for tension softening and size effects. Stress intensity factor (SIF) is computed by conducting finite element analysis (FEA) and compared with that obtained by using analytical approach. The domain integral method has been used to calculate the strain energy release rate (SERR) and SIF by post-processing the FEA results. Nonlinear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Details of size effect in the computation of SIF and remaining life prediction have been presented. Size effect has been accounted for by modifying the Paris law, leading to size adjusted Paris law. Numerical studies have been conducted for fracture analysis, crack growth studies and remaining life prediction. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature.