bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation for Expansive Strain of Degraded Mortar with Damage Mechanics Model
Authors: Yamamoto Kiyohito , Kobayashi Akira
Published: November 2010

In this study, specimens were prepared by mixing expanded polystyrene (EPS) beads with mortar to simulate degradation, and sound specimens include no beads. Measurement of acoustic emission (AE) was performed using an AE transducer. The changes in AE behavior with increase in strain were measured for a uniaxial compression test and a splitting test. The behaviors were investigated in comparison to the change in the damage variable. The AE parameters (rise time, reverberation frequency and average signal level (ASL) ) were evaluated by the average every ten seconds.
Analysis on Fire Resistance of Reinforced Concrete Beams Base on the Failure Probability
Authors: Wang Zhen Qing , Xue Zhi Cheng , Qiao Mu
Published: November 2010

For the mechanical properties of reinforced concrete under high temperature with large deterioration, the reliability of reinforced concrete beams have been largely discounted. A calculation of fire resistance based on failure probability is given by this paper. Reinforced concrete beam is usually working with cracks. Since each section with cracks has possibility of destruction, the reliability of the beam is calculated by the minimum value of n crack-sections’ resistance. The plastic zone resistance of concrete under high temperature is considered in this paper. A simple and feasible time-variant model of the resistance of reinforced concrete beams under fire and a reliability index analysis method of reinforced concrete beams under fire has been given. The action of ISO834 temperature rising curve on the reliability index of different specifications of concrete beams at different time is analyzed. The action of main parameters on the reliability index changes with time is shown. The fire resistance considers the failure probability is given. The results show that increase the reinforcement ratio and concrete cover thickness appropriately are effective measures to improve the fire resistance limit of reinforced concrete beams.
Comparison between Fatigue Life of Autofrettage and Nonautofrettage Cylinders Using Stress Intensity Factor (KΙ)
Authors: Farhangdoost Khalil , Aliakbari K.
Published: November 2010

This paper provides approximate fatigue life estimates for aluminum cylinders with a constant ratio of outer to inner radii 2.2 which were subjected to autofrettage pressure. Experimental tests of cylinders made of aluminum alloy are part of this article. Numerical simulations of the cylinders were also performed using the finite element code, ABAQUS. The resulting stresses are then used to calculate stress intensity factors to determine fatigue life. Using standard fatigue crack growth relationship, life of the cylinder is then calculated based on recommended initial and final crack length. The results show that the fatigue life due to autofrettage is more than nonautofrettage cylinder between Py1 and Py2 where, Py1 is the pressure required at the onset of yielding which occurs at the inner surface of the cylinder and Py2 is the sufficient pressure to bring the outer surface of the cylinder to yielding, i.e. the wall of cylinder becomes fully plastic.
The Approach on Making Empirical Earthquake Damage Matrix Complete Using Beta Distribution
Authors: Hu Shao Qing , Sun Bai Tao , Zhang Yong Li
Published: November 2010

In recent years, many earthquakes occurred in our country. Some is big, but most are small or middle earthquakes. Usually earthquake damage ratio of buildings in low intensity area can be attained from on site survey. But it is important that how to evaluate the seismic performance of existing building stock subjected to high intensity in earthquake-affected area. In this paper, the expectation and variance value of damage probability in known intensity is calculated by making the probability disperse. Supposing that the damage probability in each intensity obeys to Beta distribution. The expectation and variance value of damage probability in other intensity is given by comparing to that of criterion earthquake damage matrix. So the parameter of Beta-distribution function is calculated from the expectation and variance in other intensity. Then the probability of each damage grade in other intensity is gained. This approach makes the damage matrix which is suitable for this region complete and provides the reference for earthquake damage prediction and earthquake economic loss evaluation. The result showed that this approach is feasible.
Effectiveness of Linear Notch Mechanics under the Condition of Small Scale Yielding
Authors: Teranishi T. , Nisitani Hironobu
Published: November 2010

The linear notch mechanics (LNM) was proposed by H. Nisitani in 1983. The concept of LNM can assure the occurrence of the same phenomena in a notched specimen and a real object. The effectiveness of LNM under the condition of small scale yielding has not been confirmed sufficiently. In this paper, the effectiveness of LNM under the condition of small scale yielding is discussed based on the results of FEM elastic-plastic analyses.
The Application of Statistical Regression Method on the Seismic Building Economic Loss Evaluation of Yunnan Province
Authors: Zhang Yong Li
Published: November 2010

More than 30 earthquake loss assessment reports in Yunnan Province in 1993 – 2003 are collected. And the building loss in each intensity recalculated based on the all building area, destruction ratio, loss ratio and replacement cost which are listed in the reports. The relation curves of building loss versus affected population, affected area in each intensity are studied respectively using statistical regression method. After regression significance test, it is found that the relation of building loss and affected population is high; however, there is no obvious relevance of building loss versus affected area. So in this paper, the quantitative relation between the housing loss and earthquake-affected population in each intensity area is established in Yunnan Taking four earthquakes during 2004 ~ 2005 in Yunnan as examples; we estimated their earthquake building economic loss and compared them with the values taken from field investigation. The result shows this regression equations are useful and applicable for evaluating the building loss caused by earthquake.
A Method for Earthquake Damage Prediction of Building Group Considering Building Vulnerability Classification
Authors: Hu Shao Qing , Sun Bai Tao , Wang Dong Ming
Published: November 2010

In this paper, the vulnerability of the multi-storey reinforced concrete is classified and analyzed according to three control factors: construction age, story and uses. And the different categories vulnerability matrices of multi-story reinforced concrete are obtained from the monomer sample buildings which are already evaluated. The proportion of construction area of different categories can be attained from buildings census statistics. Then the vulnerability matrix of concrete building group in study region can be established by sum-product of construction area ratio of each vulnerability class in study region and each class vulnerability matrix. Finally, the vulnerability matrix of reinforced concrete structure of Xi'an Yanliang District was obtained using this approach. After comparing with the traditional earthquake damage prediction method, it is shown that this method is feasible, simple idea and high reliable and can be used for rapid assessment of post earthquake.
Thermal Stress Analysis for Shrink Fitting System Used for Ceramics Conveying Rollers in the Process of Separation
Authors: Li Wen Bin , Noda Naoaki , Sakai Hiromasa , Takase Yasushi
Published: November 2010

Steel conveying rollers used in hot rolling mills must be exchanged very frequently at great cost because hot conveyed strips induce wear on the surface of roller in short periods. In this study, new roller structure is considered which has a ceramics sleeve connected with two short steel shafts at both ends by shrink fitting. Here, the ceramics sleeve may provide longer life and reduces the cost for the maintenance. However, sometimes the steel shaft has to be pulled out for exchange. Simply, heating outside surface and cooling inside surface of the shaft are necessary for separation. However, attention should be paid to the maximum thermal stress of the ceramics sleeve in the process of separation. In this paper, finite element method analysis is applied to the structure and thermal stress has been calculated with the varying dimensions of the structure. Also several effects on thermal stress have been investigated, such as the effect of shrink fitting ratio, outside diameter, the fitted length, thickness of shaft, materials an so on. Finally the most appropriate thermal conditions to reduce maximum stress and make separation easy have been discussed, which is very useful for designing of new rollers.
Bending Fatigue Strength Evaluation of Notched Structural Steel Sheet Repaired by Bolt
Authors: He Li Sha , Hattori Nobusuke
Published: November 2010

The present investigation attempts to evaluate the improvement of working by bolt on the fatigue limit of structural steel sheets with drilling a circular hole. The material used in this study is structural steel (JIS SM400A). And the specimens are identified to two types of the non-worked specimen and the worked specimen. The results obtained in this study can be summarized as follows: (1) The fatigue limit of worked specimens increases than that of non-worked specimen. Futhermore, there has a suitable value of the torque for improving the fatigue limits. (2) The reasons of enhancing the fatigue strength of the worked specimens are due to the elastic deformation, the plastic deformation and the changing of stress concentration part. Our investigations confirm the advantages of this working method which repaired the structural steel sheets by bolt.
A New Damage Variable and its Evaluation Law for Structured Soil
Authors: Liu Yuan Xue , Li Zhong You , Zhou Jian Ting , Sun Shu Guo
Published: November 2010

Set out from a basic idea that damage is a course of energy dissipation, a new damage variable is present. The damage variable is obtained for arbitrary strain state of soil according to the superimposing principle of compatible probability event for volumetric strain and shear strain. Through the analysis of a series of triaxial experimental results of structured soil, a new damage evaluation equation is put forward. The computation results tally with the experimental data show it is reasonable that this new damage variable and its evaluation law for structured soil.
Molding Conditions and Mechanical Properties of Jute Fiber Reinforced Composite
Authors: Takemura Kenichi
Published: November 2010

In this study, molding condition and tensile properties of jute fiber reinforced composite were examined. PVA resin was used as matrix which is one of the biodegradable resin. Before tensile test, specimens have an offset twist. The tensile test after twist of jute fiber cloth was also conducted. As a result, following results were obtained. In the case of jute fiber cloth, the effect of twist deformation to tensile strength is not great. The reason is thought that the fiber cloth is flexible and easy to deform in this form. In the case of composite, molding time has an effect to the tensile properties. As the molding temperature increases, the tensile strength increases. So, the diffraction intensity was measured. The reason of effect to the strength is thought that the crystallization occurred in the matrix. When the molding temperature is so high, fiber has degradation, and the strength of the composite decreases. As the degree of twist increases, the strength decreases. The reasons are the delamination between layers and debonding between fiber and matrix.
Low Cycle Fatigue Behavior of Cast Superalloy Inconel 713LC with Al Coating at 800 °C
Authors: Obrtlík Karel , Hutařová Simona , Juliš Martin , Podrábský Tomáš , Polák Jaroslav
Published: November 2010

Cylindrical specimens of Inconel 713LC in as-cast condition and with Al diffusion coating by the CVD technique were cyclically strained under total strain control at 800 °C. Hardening/softening curves, cyclic stress-strain curves, and fatigue life curves are obtained. The coating has a beneficial effect on the Manson-Coffin curve while the fatigue life is reduced in the Basquin representation. The stress response of the coated material is lower in comparison with the uncoated one. Sections parallel to the specimen axis have been examined to study fatigue damage mechanisms.
Dynamic Stress Intensity Factor for a Radial Crack on a Circular Cavity in a Piezoelectric Medium
Authors: Song Tian Shu , Li Dong , Lv Ming Yue , Zhang Ming Ju
Published: November 2010

The problem of dynamic stress intensity factor is investigated theoretically in present paper for a radial crack on a circular cavity in an infinite piezoelectric medium, which is subjected to time-harmonic incident anti-plane shearing. First, a pair of electromechanically coupled Green’s functions are constructed which indicate the basic solutions for a semi-infinite piezoelectric medium with a semi-circular cavity. Second, based on the crack-division technique and conjunction technique, integral equations for the unknown stresses’ solution on the conjunction surface is established, which are related to the dynamic stress intensity factor at the crack tip. Third, the analytical expression on dynamic stress intensity factor at the crack tip is obtained. At last, some calculating cases are plotted to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the geometry of the crack and the circular cavity influence upon the dynamic stress intensity factors. While some of the calculating results are compared with the same situation about a straight crack and with static solutions.
Stochastic Microscopic Stress Analysis of a Composite Material via Multiscale Analysis Considering Microscopic Uncertainty
Authors: Sakata Seiichiro , Ashida Fumihiro
Published: November 2010

This paper discusses a stochastic microscopic stress analysis of a composite material for a
microscopic random variation. The stochastic stress analysis is performed via a stochastic
homogenization and multiscale analysis. The homogenization method is employed for the multiscale
analysis and the Monte-Carlo simulation or perturbation-based method can be employed for the
stochastic analysis. In this paper, outline of the analysis and some numerical results are provided.
The Dynamic Mechanical Properties of CBF Composite Plate and its Sandwich Structure with Aluminum Foam Core
Authors: Chang Zhong Liang , Zou Guang Ping , Zhao Wei Ling , Cao Yang , Wang Rui Rui
Published: November 2010

The continuous basalt fiber (CBF) as inorganic fiber obtained from the basalt melt. It has high elastic modulus, low bulk density, low thermal conductivity, low moisture absorption rate and excellent alkali resistance, etc. In this paper, the split Hopkinson pressure bar (SHPB) technique is used for testing the CBF composite plate and its sandwich structure with aluminum foam core dynamic mechanical properties, and then to study the dynamic properties of CBF composite plate and its aluminum foam sandwich structure under different high strain rate. From the test results we can see that the CBF-foam aluminum sandwich structure has superior energy absorption properties, and also from the experiment results we can obtain that the sandwich structure dynamic stress-strain curves has a typically "three-phase" characteristics and strain rate effect.
Effects of Grain Size on Fatigue Crack Propagation in Copper Film
Authors: Shimizu Kenichi , Torii Tashiyuki
Published: November 2010

Using a fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover a circular through-hole in a base plate subjected to cyclic loads, annealed copper films of 100m thickness with different crystal grain sizes were fatigued. The fatigue crack propagation in the film with large grains was often decelerated, so the crack propagation rate of the film with the large grain was lower than that of the film with the small grain. When the crack propagation was decelerated, the crack opening displacement obtained from the film with large grain size was smaller than that obtained from the film with small grain size. The relationship between the fatigue crack propagation rate and the stress intensity factor estimated from the crack opening displacement was identical for the cracks in the film with the large grain and the small grain.
Acoustic Fatigue Crack Growth Prediction in Coupled Air Structures
Authors: Hosseini-Toudeshky Hossein , Karimi M. , Mohammadi Bijan
Published: November 2010

In this paper, crack growth of thin-walled cylinders containing an initial crack under acoustic plane wave is analyzed. A coupled air-structure modeling is considered for the analyses. For this purpose, a methodology for computational modeling of the fatigue crack growth in cracked cylinders using finite element method is presented. Effects of various parameters such as crack length increment and boundary conditions on the crack growth rate are investigated.
The Effects of Trabecular Bone Microstructure on Compression Property of Bovine Cancellous Bone
Authors: Tanaka Kazuto , Tanimoto Yusuke , Kita Yusuke , Enoki Shinichi , Katayama Tsutao
Published: November 2010

To establish clinical bone assessment for osteoporosis, it is necessary to evaluate not only bone density but also trabecular bone microstructure and mechanical properties of bone. Therefore relationship between the micro-structural parameters and the mechanical properties of the cancellous bone of bovine distal femur was investigated. Compression test was carried out using universal testing machine to measure Young’s modulus and the ultimate strength. X-ray CT was used to obtain 3D image of specimens. Bone trabecular orientation was obtained from fabric ellipse by the MIL (Mean Intercept Length) analysis. Young’s modulus and ultimate strength had a high correlation with bone density respectively; furthermore ultimate strength had a high correlation with Young’s modulus.
Mechanical Behavior of Environment-Friendly Green Composites Fabricated with Starch-Based Resin and Short MAO Fibers
Authors: Takagi Hitoshi , Netravali Anil N.
Published: November 2010

Environmentally friendly green composites were fabricated from a natural cellulosic fiber (MAO fiber) and a biodegradable starch-based resin through hot-pressing. The effects of fiber length and alkali surface treatment on mechanical properties of the green composites were investigated. Fiber lengths of 2.5, 5, 10, and 20 mm were used and fiber weight content was adjusted to 56%, to obtain short fiber composites with random orientation. Ultimate tensile strength increased with increasing the fiber length up to 10 mm and remained almost constant for further increases in fiber length. Fracture strain for the composites fabricated with fiber length of 2.5 mm showed the smallest value of approximately 2 %, which is less than that of MAO fiber. This might be attributed to the debonding at the fiber/matrix interface. Fracture strains of the green composites with fibers longer than 2.5 mm were almost constant and were comparable to the fracture strains of MAO fiber indicating that the fracture properties were controlled by the fiber. Both tensile strength and Young’s modulus values were increased by alkali surface-treatment for MAO fibers. The reason for this behavior seems that alkali treatment increases the fiber/matrix interfacial adhesion strength primarily by removing lignin.
Fatigue Analysis of Penetration Assembly Joined by Multi-Pass Welding
Authors: Li Hong , Li Li , Wang Ren Fu
Published: November 2010

Due to high centralized instantaneous heat input in the process of the welding, a great deal of residual stresses and distortions should be brought in the welded structures, which can heavily influence the capability and reliability of the structure. Residual stresses and welding fatigue behaviors of stainless steel penetration assembly joined by multi-pass welding are studied in this paper. The distribution of transient temperature field and real-time dynamic stresses field in the welded region must be calculated first. Based on the residual stresses, the random wave load putting on the structure and fatigue factors, according to Miner fatigue damage law, some fatigue behaviors such as fatigue life and remaining life are obtained.
On Electrochemical Polarization Curve and Corrosion Fatigue Resistance of the AZ31 Magnesium Alloy
Authors: Ishihara Sotomi , Nan Z.Y. , Namito Tomonori , Goshima Takahito , Sunada Satoshi
Published: November 2010

Recently, due to increasing popularity of the magnesium alloys, many studies on corrosion resistance of the magnesium alloys have been reported to improve their corrosion resistance. However, it is not clarified yet whether an electrochemical polarization curve or a corrosion rate is a good measure for the corrosion fatigue resistance or not. In the present study, corrosion fatigue tests, the weight loss test, and measurement of the electrochemical polarization curve were performed in 3% sodium chloride solution using both the extruded and the rolled Mg alloys. It was clarified that there are no differences in the corrosion fatigue lives between the extruded and the rolled Mg alloys, though they have different corrosion resistance. So, it was concluded that the corrosion fatigue characteristic does not correspond well with the trend in corrosion resistance.
Fatigue Crack Propagation Rate in EUROFER 97 Estimated Using Small Specimens
Authors: Hutař Pavel , Náhlík Luboš , Ševčík Martin , Seitl Stanislav , Kruml Tomáš , Polák Jaroslav
Published: November 2010

The proposed paper describes fatigue damage evolution in Eurofer 97 reduced activation ferritic-martensitic steel. The short crack growth study was performed on small cylindrical specimens using an MTS 880 servohydraulic machine at constant strain amplitude. Based on the fatigue crack growth data obtained and corresponding 3D finite element analysis Paris law region of the fatigue curve were estimated. The results obtained were compared with standard determination of the fatigue crack growth rate according to ASTM using CT specimens. The presented results can help to transfer experimental data measured on small specimens to large structures and vice versa.
Scattering of Out-of-Plane Line Source Load by Shallow-Embedded Circular Lining Structure and Crack in Half Space
Authors: Yang Zai Lin , Xu Hua Nan , Xu Mei Juan , Sun Bai Tao
Published: November 2010

In this paper, we study the problems of scattering of out-of-plane line source load by half-space shallow-embedded circular lining structure and a crack in the field of linearly elastic dynamic mechanics. This is an essential solution to the displacement field for the elastic space possessing shallow-embedded circular lining structure and a crack while bearing out-of-plane harmonic line source load at arbitrary point. The wave function of scattering of shallow-embedded circular lining structure impacted by incident steady SH-wave is constructed based on the symmetry of SH-wave scattering and the method of multi-polar coordinates system. Then a crack is made out using the method of “crack-division”. Thus expressions of displacement and stress are established when shallow-embedded circular lining structure and a crack are both in existent. Finally, with two different dimensionless parameters, numerical results of scattering of out-of-plane line source load by half-space shallow-embedded circular lining structure and a crack are obtained and numerical examples are provided to show the influence of wave number ratio, shear modulus ratio, thickness ratio and the ratio of distance between the center of the different cavity and ground surface and the radius of the circular lining structure upon the dynamic stress concentration factor(DSCF) and dynamic stress intensity factor(DSIF) at crack tip.
Life Time Estimation of the Multilayer Plastic Pipes
Authors: Zouhar Michal , Vallet Laura , Hutař Pavel , Náhlík Luboš
Published: November 2010

In the contribution solution of special fracture mechanics problems connected with multi-layer plastic pipes was investigated. The assumptions of linear elastic fracture mechanics were accepted. A complex three-dimensional numerical model of multi-layer pipe system consisting of main (functional) pipe and protective layers has been suggested and numerically solved by finite element method. Two basic problems connected with lifetime expectation of multilayer pipe system have been considered and discussed, namely: question of fracture mechanics description of multilayered pipe system and corresponding measurements of the material properties. The suggested approach can help for more accurate estimation of the multilayer pipe damage.
Calculation on High Stress Concentration Field of Elliptical Hole Problems by the MFS Using Dissimilar Allocation of Source Loads
Authors: Fujisaki Wataru
Published: November 2010

It is well known that the MFS based on the collocation method can be implemented easily and gives good accuracy in most cases[1,2,3]. The stability of the accuracy, however, depends on the source location. Recently, Karageorghis et.al. calculated SIF of a central crack in a rectangle plate using a similar shape of uniformly distributed points[4]. Gorzelanczyk et.al. made some remarks concerning the shape of the source contour with application of the MFS to elastic torsion of prismic rods. It is reported that the accuracy is better when the source contour is geometrically similar to the boundary of the region in comparison to the source contour with a shape of a circle[5].
Numerical Simulation on Ultimate Bearing Capacity of FRP Reinforced Concrete Notched Beams
Authors: Xia Pei Xiu , Zou Guang Ping , Lu Jie
Published: November 2010

: In this research, some concrete three-point bending specimens (beams) reinforced by FRP are used in numerical simulation to study the influence of the reinforcement on fracture mechanism and the extreme load-bearing capacity of the specimens. The numerical simulation results show the propagation of the crack in concrete is controlled by using FRP. Meanwhile the load-bearing capacity is increased greatly and failure modes are changed.
Image Based Displacement Vector Estimation Method around the Fatigue Crack Tip
Authors: Moriyama Masao , Ushijima Daisuke , Katsuta Junichi
Published: November 2010

To clarify the instantaneous strain field during the fatigue crack propagation test, an attempt is made to estimate the displacement vector of the small area of the crack tip from the high speed movie. The key theory of the estimation is Particle Image Velocimetry (PIV) which is frequently use in the fluid dynamical data analysis. PIV means the area based correlation matching between the sequential image pair. At first the earlier image divided into the small subareas, and on the later image most correspondent position to the subarea is searched. The each displacement of the subarea position between earlier and later image means the local deformation of the crack tip.
Through the numerical simulation, the subarea size and search area size are defined to get the realistic result. To make the instantaneous deformation within a cycle of the fatigue crack propagation test, high-speed camera with high-power camera is used. The frame rate is beyond 1000Hz and shutter speed is 1/8000 second. By using the such camera and optimized PIV algorithm, the instantaneous strain field can be estimated and this will analyze the phenomenon of fatigue crack propagation.
Arcan-Richard Specimens: Is there a Pure Shear Mode?
Authors: Seitl Stanislav , Hutař Pavel , Canteli Alfonso Fernández
Published: November 2010

Traditionally, applications of fracture mechanics have been mainly focused on cracks growing under the opening or mode I mechanism (three point bend specimen, middle tension specimen, crack tension specimen, etc.). When investigating instability under mixed mode loading conditions, three different alternatives can be envisaged consisting of: a) machining a hole in standard specimens, b) creating a crack oriented under a given angle, and c) using non-standard Arcan-Richard specimens. In this work, finite element calculations are performed to analyze the initial values of the fracture parameters in Arcan-Richard specimens. First, the influence of the normal stress mode to the shear stress mode ratio is analyzed, then the effect of the constraint level is discussed, and finally, the initial propagation angle of the daughter crack is derived.
Experiment Study on Size Effect of Concrete Compress Damage Parameters
Authors: Wang Xiang Dong , Deng Ai Min , Zhu Wei Xuan , Wang Yue Feng , Liu Fang Chao
Published: November 2010

The bearing capacity decreases continuously along with the deterioration of material property under the action of external effects. It is important to evaluate the damage of concrete, and the damage parameter plays an important role in this process. An experimentation method has been designed, which can simulate the initial damage by mixed initiator into concrete. Using the elastic modulus of axial compression experimentation, the initial damage D0 and damage threshold value Df have been gained. The Size effect of concrete compress damage parameters is verified.
Numerical Analysis of the Effect of Cope Hole on the Fatigue Strength of Corrugated Web Girders
Authors: Wang Z.Y. , Ouyang W.X. , Wang Qingyuan , Chen Y.Y. , Jiang Rui Juan
Published: November 2010

A common means of facilitating cross welding on the girder flange is to use cope hole on the girder web. This paper presents a study on the fatigue strength of the corrugated web girders with the cope hole using numerical analysis. Typical stress concentration behaviours are discussed relative to reported experimental results, and parameter variations are then used to study the stress gradient on the corrugated web as the influence of the cope hole. Based on the simplified cumulative fatigue summation implemented in fatigue post-processor, fatigue life predictions are presented with codified curves of AASHTO LRFD.
Linear Viscoelastic Modelling of Damage-Involved Structural Pounding during Earthquakes
Authors: Mahmoud Sayed , Jankowski Robert
Published: November 2010

Damage-involved structural pounding during earthquakes has been recently intensively studied using different impact force models. The results of the previous studies indicate that the linear viscoelastic model is relatively simple yet accurate in modelling pounding-involved behaviour of structures during earthquakes. The only shortcoming of the model is a negative value of the pounding force occurring just before separation, which does not have any physical explanation. The aim of the present paper is to verify the effectiveness of the modified linear viscoelastic model, in which damping term (related to modelling of damage effects) is activated only during the approach period of collision therefore overcoming this disadvantage. The accuracy of the model is checked in a number of comparative analyses, including the comparison with the results of impact experiments and shaking table experiments on pounding between two steel towers. The results of the study indicate that the use of the modified linear viscoelastic model leads to very similar pounding-involved responses as in the case of the linear viscoelastic model.
Test Study of Shear Strength of High Strength Stone Masonry
Authors: Hu Da Lin , Cheng Feng , Chen Long Gang
Published: November 2010

In China many long span stone arch bridges were built in the last 5 decades, most of these bridges were built with micro-aggregate concrete joint masonry. However, the mechanical properties of this kind masonry have been seldom studied. Based on 5 groups of specimens with C30 or C40 micro-aggregate concrete joints and dressed blocks, shear strength of the masonry is tested and analyzed, friction coefficients and empiric formulas of shear strength of the masonry are presented in this paper, design value of shear strength of the masonry is assessed and discussed.
Expanded Uncertainty in Measurements of Vertical and Lateral Behaviors for the Rubber-Tired Light Rail Vehicle
Authors: Kim Yeon Su
Published: November 2010

In the public transport vehicle, vertical and lateral behaviors have a significant effect on ride comfort and safety of passengers on curved track. Based on vertical and lateral vibration accelerations measured on floor level in passenger compartment when the K-AGT ran on the minimum curvature of the 2.4km-test track in driverless mode, expanded uncertainties in measurement were estimated statistically. In addition, vertical and lateral dynamic behaviors of the K-AGT were discussed in this paper.
Fatigue and Fracture Behaviour of Closed Cell Aluminium Foam
Authors: Dattoma Vito , Giannoccaro N.I. , Messina Arcangelo , Nobile Riccardo
Published: November 2010

Aluminium foam represents a new class of materials characterized by a large variability due to its porous structure. A simple and easy-to-use indicator of foam inhomogeneities is represented by apparent density, but this parameter does not give indications about differences existing in structural stiffness. To overcome this limit, the variability of natural frequency has been considered in this work in the case of commercial closed-cell aluminium foam. Moreover, fatigue and fracture properties of aluminium foam are not well studied. In this work standard three-point bend specimens SE(B) have been used to determine critical Crack-Tip Opening Displacement. The pre-crack phase, consisting in the application of appropriate fatigue load, has been monitored through modal analysis. Experimental results confirm the possibility of using this technique also in the initial step of fatigue failure process to quantify the amount of fatigue damage induced by repeated loads.
Damage Evolution of Composite Laminates with Digital Image Correlation
Authors: Giancane Simone , Nobile Riccardo , Panella Francesco W. , Dattoma Vito
Published: November 2010

DIC (Digital Image Correlation) based methodology gives full field measure of the displacement using a well defined algorithm for matching the images of loaded and load free component, so that displacement in a plane can be evaluated for a certain number of grid reference points on the analysed surface. In this work, the authors present an application of DIC technique to analyse fatigue damage phenomena in two notched GFRC laminates under tensile load. Damage analysis based on optical DIC technique has been performed to detect the damaged areas on the specimen surface. The damage evolution and failure mechanism has been followed monitoring two parameters: the local hysteresis area of stress-strain cycles, the local stiffness variation.
Numerical Investigation on Polar Effects in Localized Shear Zone
Authors: Ebrahimian Babak , Noorzad Asadollah
Published: November 2010

Numerical simulations related to polar effects in an infinite extended granular layer under shearing movement and constant vertical pressure are presented. The mechanical behavior of cohesionless granular soil is described within the framework of micro-polar (Cosserat) continuum and using an elasto-plastic constitutive relation. The influence of Cosserat rotations and couple stresses are taken into account using the mean grain size as characteristic length. Finite element method in Updated Lagrangian (UL) frame is used to consider large deformations during calculations. The numerical results demonstrate that for large shearing movement, the shear deformations within the granular layer are localized into a narrow zone. The FE-calculations indicate that the polar effects manifest by the appearance of noticeable grain rotations, high void ratios, pronounced volume changes within the localized shear zone.
Experimental Investigation and Numerical Simulation of Porous Volcano Rock Hypervelocity Impact on Whipple Shield of Spacecrafts
Authors: Jia Bin , Liao Gao Jian , Gong Hai Peng , Pang Bao Jun
Published: November 2010

All spacecrafts in earth orbit are subject to hypervelocity impact by micro-meteoroids and space debris, which can in turn lead to significant damage and catastrophic failure of spacecraft. Porous volcano rock was adopted as one of micro-meteoroid material due to their similar physical and geometric features. Two-stage light gas gun experiments were carried out for a 6mm diameter volcano rock projectile impact on an Al-Whipple shield within the speed range from 1 km/s to 3 km/s. An ANSYS/LS-DYNA software was employed and justified by experimental results, in which a porous geometrical model was established for volcano rock projectile. The higher speed range was extended from 3 km/s to 10 km/s by numerical simulation. The results of experiments and numerical simulation indicated that major damage on rear wall of the Whipple shield impacted by volcano rock projectile is caused by the fragments of bumper of the shield, which is different from that of aluminum projectile. And 5.5km/s is the critical speed of a 6mm diameter volcano rock projectile impact on the Whipple shield investigated.
Analysis of Fracture Behavior in Polymer Matrix Composites by Infrared Thermography
Authors: Kim Jeong Guk , Yoon Sung Cheol , Kwon Sung Tae
Published: November 2010

The tensile fracture behavior of polymer matrix composite materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, E-glass fiber reinforced epoxy matrix composites, which are applicable to bogie materials in railway vehicles to reduce weight, were used for this investigation. In order to explain stress-strain behavior of polymer matrix composite sample, the infrared thermography technique was employed. A high-speed infrared (IR) camera was used for in-situ monitoring of progressive damages of polymer matrix composite samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of polymer matrix composite materials during monotonic loadings.
Novel Methods for Assessment of Three-Dimensional Constitutive Properties for Composites
Authors: Carpentier Paige , Makeev Andrew
Published: November 2010

Accurate three-dimensional stress-strain constitutive properties are essential for understanding of complex deformation and failure mechanisms for glass-fiber and carbon-fiber reinforced polymer-matrix composites. A large number of different methods and specimen types, which are currently required to generate three-dimensional allowables for structural design, slow down material characterization. Also, some of the material constitutive properties are never measured due to prohibitive cost of the specimens needed. This work shows that simple short-beam shear specimens are well-suited for measurement of 3D constitutive properties for composite systems. In particular, a methodology to measure tensile and compressive material properties, generate shear stress-strain curves and measure the shear strength in a simple short beam shear test will be presented. The methodology is based on the Digital Image Correlation (DIC) full-field deformation measurement. Short-beam and curved-beam tests are accomplished to generate 3D stress-strain response for glass/epoxy and carbon/epoxy tape composite material systems. Accuracy of constitutive properties is also verified using standard methods and data available in the public domain.
Accurate Solutions of Stress Intensity Factors of Standard Fracture Test Specimens
Authors: Saimoto Akihide , Motomura Fumitaka , Nisitani Hironobu
Published: November 2010

Practically exact solutions of stress intensity factor for several two-dimensional standard specimens were calculated and shown in numeric tables. The solutions were confirmed to converge until 6 significant figures through a systematical computation of discretization analysis. The convergence analyses were carried out by using a general purpose program based on a body force method.
Temperature and Geometry Dependence of Fracture Toughness in "Euro Fracture Dataset"
Authors: Akbarzadeh P. , Hadidi-Moud Saeid
Published: November 2010

Reliable prediction of fracture conditions is a major concern in the integrity assessment of structural components. This is specifically critical within the transition regime where there is a significant scatter in fracture test data. In recent years local stress based approaches that use a "Weibull distribution function" have been examined to predict probability of cleavage fracture at lower shelf temperature. Furthermore the role of constraint in toughness prediction has been noted. An extensive experimental programme known as "Euro fracture dataset" aimed at characterisation of the "Ductile-to-Brittle" transition (DBT) behaviour of ferritic steels. Recently this data set was used by authors to propose a set of "Global" equations for determination of temperature and thickness dependence of Weibull distribution parameters. In this paper finite element simulations of fracture tests are carried out firstly to verify the experimental findings and secondly to examine and validate the proposed "Global" equations. This objective has been achieved through the comparison between the experimental data, predictions of "Global" curves and the results of performed finite element simulations.
An Analytical Solution for Dynamic Stress Intensity, Kd, under Impact Loading
Authors: Malekzadeh A. , Hadidi-Moud Saeid
Published: November 2010

Characterisation of failure of components subjected to impact fatigue has received much interest in recent years. Critical stress intensity factor, i.e. fracture toughness, is a characteristic parameter for fracture conditions. Evaluation of this parameter is therefore of primary importance in the study of structures containing cracks. Due to its significance numerous research work have been carried out to provide dynamic stress intensity descriptions under cyclic, impulse and impact loading conditions. These methods are mainly based on numerical analyses and / or experimental techniques led to a range of approximate models. This paper firstly provides a review of fatigue failure due to impact loading and explains the principles of impact mechanics concepts including impact loading, stress wave equation and resulting stress distributions. Then, based on available experimental studies on developing and propagating cracks under impact loading, suggests a simple model leading to an approximate analytical solution for determination of dynamic stress intensity factor, kd under high strain rate loading. Calculated values based on the suggested solution compare well with the experimental data.
Crack Width Evolution of R/C Structures Subject to Corrosion and Fatigue
Authors: Giordano Luca , Tondolo Francesco
Published: November 2010

Corrosion modifies the steel-concrete interface in reinforced concrete structures. Moreover in structures subjected to cyclic load, a simultaneous mechanical deterioration due to the load is present. Both phenomena can lead to an evolution of cracks width during the service life. In order to evaluate the crack openings increase, an experimental campaign on reinforced concrete ties subjected to simultaneous loading and corrosion have been realized. Transversal crack opening, initially due to loading and longitudinal corrosion cracks evolution is monitored. Results highlight the differences in terms of corroded and uncorroded specimens, static and cycling test and also different loading amplitude. Finally it can be observed as the growing of the damage is significantly different when a cycling action, combined with a chemical attack is present.
Low Cycle Fatigue of Cast γ-TiAl Based Alloys at High Temperature
Authors: Petrenec Martin , Šmíd Miroslav , Kruml Tomáš , Obrtlík Karel , Polák Jaroslav
Published: November 2010

The low-cycle fatigue properties of cast nearly lamellar TiAl alloys with diverse Nb content at room temperature and 750°C were compared. Monotonic tensile curves, cyclic stress-strain curves (CSSC) and combined fatigue life curves were obtained at both temperatures. After cyclic straining the surface relief and the fracture surfaces were observed using scanning electron microscopy. The increase in Nb content significantly improves tensile properties and CSSCs at both temperatures. The combined fatigue life curves especially at 750 °C are shifted to higher fatigue lives. The effect o Nb content on the tensile and cyclic strength is discussed in relation to the thickness of the lamellae. Persistent slip markings formed along interlamellar interfaces were predominant locations for fatigue cracks. At both temperatures and materials showed similar crack initiation and propagation behavior. The cracks initiated at surface or in sub-surface region creating smooth flat areas corresponding to the persistent slip bands.
Determination of Fracture Parameters for Non-Standard Wedge Splitting Specimen of Concrete
Authors: Zhao Yan Hua , Zhang Hua , Dong Wei
Published: November 2010

The wedge splitting (WS) test is now a promising method to perform stable fracture mechanics tests on concrete-like quasi brittle materials. Fracture parameters, such as fracture toughness and critical crack opening displacement and et.al, are however not easy to determined since formulae available from stress intensity factor manual are restricted to standard specimen geometry. The paper attempts to compute expressions for commonly used fracture parameters for a general wedge splitting specimen. By means of finite element analysis program, test simulation was performed on non-standard wedge splitting specimen with different depth and initiation crack length, and thereafter expressions were proposed for stress intensity factor at the pre-cast tip and crack mouth opening displacement on the load line. Based on the work above, size effect on the unstable fracture toughness and crack extension were investigated, and the consistency of fracture toughness data for various specimen depth as well as initiation crack length is demonstrated. The crack extension is little sensitive to the initiation crack length, it increases with the depth of specimen, which can be explained by the boundary influence of the specimen.
Investigating Faulty Gear-Unit Vibration
Authors: Belšak Aleš , Flašker Jože
Published: November 2010

A crack in the tooth root is probably the least desirable problem in gear unit operation; it often leads to failure. Signals produced by a gear with a crack in the tooth root, produced through real operating conditions, and signals caused by a faultless gear are used for the analysis. By monitoring vibrations it is possible to detect the presence of a crack. A fatigue crack in the tooth root brings about significant changes in tooth stiffness. Other faults are usually linked with modifications of other dynamic parameters. Time Frequency Analysis tools, e.g. Wavelets Analyses, are used to analyse a non-stationary signal. The wavelet transform is chosen for the analysis. The wavelet function similar to the dynamic reaction of the crack in the tooth root is selected. By means of the methods and the analysis presented in this paper, the reliability of determining modifications in signal vibrations is improved.