bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality Control in the Fabrication of Hanging File Stent Components of Automotive Transmission
Authors: Zhu Jin , Zhu Chun Dong
Published: October 2009

Hanging file stent components (HFSC) of automotive transmission require high reliability, because the assembly quality has direct influence on the whole vehicle performance, especially in the area of security. But it is easy to make mistake in assembling it, and it is hard to detect errors, because the HFSC has many different parts, which have similar shape. This paper analyzes the geometrical features of the hardware of HFSC, and helps to find out those parts needing inspection through researching the possible mistakes. According to the results of the analysis, an automatic inspection system which is controlled by microcontrollers for HFSC quality measurement is designed. This system uses a new sensor designing according to the necessary of detection, and a suitable sensor planning program is presented. After the accomplishment of this system, it is proved flexible and effective through half year of practice.
The Promotion of Software Reliability for Vehicle Navigation System
Authors: Xie Shang Fei , Sun Zhi Li , Zhao Liang
Published: October 2009

Software reliability is an important attribute of software quality. Based on the concept of software reliability and reliability indicator, this paper presents the analysis techniques of software reliability for the vehicle navigation system, obtains the appropriate forecasting model of vehicle navigation software reliability through tests and calculation, and puts forward suggestions for promoting the vehicle navigation software reliability.
Research into the Quality Control Technology in Machining Process of Enterprise Alliances Based on Procedure Oriented Parameter
Authors: Zhao Ming Guang
Published: October 2009

In network-based manufacturing, an enterprise alliance has such characteristics as: information, integration, globalization and variation, which put forward new requests for the conventional quality control technology. Exploring the new quality control technology in machining process for enterprise alliances based on process parameter, this paper brings forward a sort of system architecture and implementing plan, which is composed of equipment layer, distributing information disposal layer, network truss layer and decision-making layer. The disposal method of data losing and time delay are also presented.
A Study on Structural Strength in Carbody Structure of an Express Train
Authors: Yoon Sung Cheol , Kim Jeong Guk , Jeon Chang Sung , Kim Won Kyung , Choe Kang Youn
Published: October 2009

In this paper, we describe a carbody structural analysis and the result of its stress test. The purpose of this study is to evaluate the safety and functionality of the body structure operating under maximum load. The body structure was made of aluminum alloy and consisted of the side frame, under frame, roof frame, and end frame. Of these components, the side frame and under frame were the most important components in consideration of the vehicle and passenger loads. Both the structural analysis and stress test were performed under the condition that was based on the "Performance Test Standard for Electrical Multiple Units." The test results showed that the body structure is safe and stable under the condition of the designed load.
Crack Tip Damage Mechanism under Monotonic and Cyclic Loading Conditions
Authors: Roy Himadri , Sivaprasad Seetharaman , Tarafder S. , Ray Kalyan Kumar
Published: October 2009

Fracture resistance of AISI 304LN stainless steel has been examined by monotonic and cyclic J-integral tests, the latter being carried out using periodic unloading as per pre-determined R-ratio. The cyclic fracture resistance is found to be almost 1/5th of its corresponding monotonic value. The deterioration of fracture resistance under cyclic loading has been attributed to crack tip resharpening due to smearing and smashing of voids owing to rubbing of adjacent crack surfaces in the compressive load cycles.
Influence of Material Parameters on Plasticity Induced Crack Closure
Authors: Rodrigues Dulce Maria Esteves , Antunes Fernando , Branco R.
Published: October 2009

Plasticity Induced Crack Closure (PICC) is an important fatigue phenomenon affecting crack growth under cyclic loading, which makes important to consider it in the design of components. In this paper a parametric study that correlates elastic-plastic material parameters with plasticity induced crack closure (PICC) is presented. Yield stress and hardening coefficient were selected as the material parameters of interest and a sensitivity analysis was developed. The influence of the different parameters on PICC is explained based on the analysis of crack tip micromechanisms for plastic deformation.
Modelling of Damage Development and Strain Ratchetting Using a Viscoplastic Constitutive Formulation
Authors: Cornet Christophe , Zhao Li Guo , Tong Jie
Published: October 2009

Simulation of both damage development and strain ratchetting in uniaxial loading conditions has been presented for a nickel-based superalloy at 650°C using the unified Chaboche viscoplastic model. A third kinematic hardening component was employed to simulate strain ratchetting; and a damage variable, based on plastic strain development, was also incorporated to simulate the damage evolution behaviour. Good agreement between the model predictions and the experimental results was obtained for both damage evolution and strain ratchetting. The model was then utilised to investigate the cyclic deformation behaviour near a crack tip for a single edge notch tension (SENT) specimen. Finite element analyses showed that strain ratchetting is seems to be a characteristic of the fatigue crack tip, which has been used as a criterion to predict the crack growth rates.
Failure Analysis of a High Pressure Orifice Flange of an Oil Refinery during Operation
Authors: Hadianfard Mohammad Jaffar , Hadianfard M.A.
Published: October 2009

Structural failure of a high pressure orifice flange of an oil refinery is studied by using visual inspection, optical and electron microscopy, tensile tests, fractography and stress calculation. This flange was located at a high pressure (2700 KPa), elevated temperature (370 C°) feeding pipe line. Failure observed during a startup at the time of increasing pressure and temperature. The results of the analysis show that brittle fracture has acted as a main factor for failure of the structure and stress concentration together with corrosion have provided minor sources for the failure. These results indicate that brittle behavior of this flange can attribute to hydrogen embrittlement of the steel material.
Modelling the Effect of Microstructural Randomness on the Fracture of Composite Laminates with Stochastic Cohesive Zone Elements
Authors: Khokhar Zahid R. , Ashcroft Ian A. , Silberschmidt Vadim V.
Published: October 2009

Fibre reinforced polymer composites (FRPCs) are being increasingly used in structural applications where high specific strength and stiffness are required. The performance of FRPCs is affected by multi-mechanism damage evolution under loading which in turn is affected by microstructural stochasticity in the material. This means that the fracture of a FRPC is a stochastic process. However, to date most analyses of these materials have treated them in a deterministic way. In this paper the effect of stochasticity in FRPCs is investigated through the application of cohesive zone elements in which random properties are introduced. These may be termed ‘stochastic cohesive zone elements’ and are used in this paper to investigate the effect of microstructural randomness on the fracture behaviour of cross-ply laminate specimens loaded in tension. It is seen from this investigation that microstructure can significantly affect the macroscopic response of FRPC’s, emphasizing the need to account for microstructural randomness in order to make accurate prediction of the performance of laminated composite structures.
An Experimental Study on the Mechanical Performance and Damage Evolution of Woven Fabric E-Glass Fiber Reinforced Epoxy Composite
Authors: Wu Ling , Guo Ying Nan , Li Yu Long
Published: October 2009

The present study focuses on the mechanical performance and damage evolution of woven fabric E-glass fiber reinforced epoxy composite (7781/F155-glass/epoxy). For the identical behavior in the 0o and the 90o directions of the tested material, the mechanical experiments were performed with 0o and 45o specimens. Three kinds of tests were implemented respectively: tension test with 0o specimen, compression test with 0o specimen, and tension test with 45o specimen which represents the in-plane shear test. Tension, compression and in-plane shear damage, which are defined as the decreasing ratio of modulus, were calculated from the data of quasi-static cyclic tests. The influence of loading rate on material behaviors were investigated under three different loading rates. Although all of the three loading rates are low, it showed that the strain rate has obvious effects on the ultimate strengths and moduli of the glass fiber reinforced epoxy composite.
On Three Dimensional Curved Crack Propagation Based on Configurational Forces
Authors: Schütte Henning
Published: October 2009

A numerical scheme is presented to predict crack trajectories in three dimensional components. First a relation between the curvature in mixed-mode crack propagation and the corresponding configurational forces based on the principle of maximum dissipation is reviewed. With the help of this, a numerical scheme is presented which is based on a predictor-corrector method using the configurational forces acting on the crack together with their derivatives along real and test paths. It is outlined how to extend the approach to three dimensional problems. With the help of this scheme it is possible to take bigger than usual propagation steps, represented by splines. Essential for this approach is the correct numerical determination of the configurational forces acting on the crack tip. An approach valid for arbitrary non-homogenous and non-linear materials with mixed-mode cracks is presented. Numerical examples show, that the method is able to predict the crack paths in components with holes, stiffeners etc. with good accuracy, saving much computational effort.
Green's Function Solution of the Semi-Space with Double Shallow-Buried Cavities
Authors: Li Hong Liang , Zhang Cun
Published: October 2009

In mechanical engineering and modern municipal construction, shallow-buried cavity structure is used widely. In this paper, Green's Function is studied, which is the solution of displacement field for elastic semi-space with double shallow-buried cavities while bearing anti-plane harmonic line source force at any point. In the complex plane, considering the symmetry of SH-wave scattering , the displacement field aroused by the anti-plane harmonic line source force and the scattering displacement field impacted by the circle cavities comprised of Fourier-Bessel series with undetermined coefficients which satisfies the stress-free condition on the ground surface are constructed. Through applying the method of multi-polar coordinate system, the equations with unknown coefficients can be obtained by using the stress-free condition of the circle cavities in the radial direction. According to orthogonality condition for trigonometric function, these equations can be reduced to a series of algebraic equations. Then the value of the unknown coefficients can be obtained by solving these algebraic equations. Green's function, that is, the total wave displacement field is the superposition of the displacement field aroused by the anti-plane harmonic line source force and the scattering displacement field. By using the expressions, an example is provided to show the effect of the change of relative location of the circle cavities and the location of the line source force. Based on this solution, the problem of interaction of double circular cavities and a linear crack in semi-space can be investigated further.
Analysis of Stress Intensity Factor for Interfacial Crack in Bonded Dissimilar Plate under Bending
Authors: Kakuno Hatsuki , Oda Kazuhiro , Morisaki Tetsuya
Published: October 2009

This paper presents the simple method to determine the complex stress intensity factor of interface crack in bi-material plate under bending. In the present method, the stress values at the crack tip calculated by FEM are used and the stress intensity factors of interface crack are evaluated from the ratio of stress values between a given and a reference problems. A single interface crack in an infinite bi-material plate subjected to tension and shear is selected as the reference problem in this study. The accuracy of the present analysis is discussed through the results obtained by body force method. As the result, it is confirmed that the present method is useful for analyzing the interface crack under bending.
Effect of Water Absorption on Mechanical Properties of Hemp Fiber Reinforced Composite
Authors: Takemura Kenichi
Published: October 2009

In this study, the effect of water absorption on mechanical properties of hemp fiber reinforced green composite(HGC) was examined. Plain woven hemp fabric was used as reinforcement. Emulsion type biodegradable resin was used as matrix. The composite was made by compression molding method. Water absorption rate and the effect of the ratio on the mechanical properties were examined. Following results are obtained. The water absorption rate increased with an increase of absorption time. The water absorption rate had an equilibrium state within 30 days. The duration was not dependent on fiber content. In the case of that specimen was kept in water 182 days, the strength decreased 70% of the ultimate one. But in the case that the specimen has dry process after water absorption process, the strength recovered 57%. The recovery ratio is not dependent on water absorption time. The strength reduction rate after dry process is not dependent on fiber content. The strength of resin decreased 62%, and the strength of fiber decreased 13% by water absorption. So the strength reduction of the composite is due to the effect of matrix.
Inspection of the Internal Cracks on a Pipe Using a Cylinder-Type Magnetic Camera
Authors: Kim Jung Min , Lee Jin Yi
Published: October 2009

Two important factors in damage tolerance engineering are the damage size that can be tolerated and the use of applied nondestructive testing (NDT) technique for detection of defects. Generally, NDT of large mechanical structures, such as vessels and pipes in nuclear power plants, is carried out according to national codes, and the damaged mechanical parts detected during periodic NDT are repaired or replaced after the evaluation. However, unexpected accidents can occur if cracks in the structure grow and exceed the tolerance limit during operation. Therefore, there is a need to develop NDT techniques that can detect micro-damage in the vessels and pipes. In this paper, we propose a cylinder-type magnetic camera to fill this need. We use a cylindrically integrated Hall sensor array (CIHaS) as a magnetic sensor to create magnetic images, and we use a solenoid coil as the source of the magnetic field detected by the magnetic camera in order to achieve high crack-detection ability. The proposed method is tested with an examination of the cracks on a prepared pipe sample.
Magnetic Images and NDT of the Express Train Wheel Using a High Speed Scan-Type Magnetic Camera
Authors: Hwang Ji Seong , Lee Jin Yi
Published: October 2009

Wheels are essential parts of an express train, as they support the train’s weight, but because of the limited time available for testing and repair in the maintenance factory, the 1000 wheels of each high-speed train must be tested within 1 h. Therefore it is essential to develop a new NDT system that is able to (a) detect cracks quickly and (b) provide high crack-detection ability regardless of the state of the materials. In this paper we propose a scan-type magnetic camera to satisfy this need. We use a linearly integrated Hall sensor array (LIHaS) as a magnetic sensor to make high-speed testing possible, and we use a small, yoke-type magnetizer as the magnetic source for the magnetic camera to assure high crack-detection ability. We tested the method by examining the cracks on a sample wheel traveling at 27.5km/h.
Numerical Simulation of Automotive Crash-Box Subjected to Low Velocity Frontal Impact
Authors: Li Qing Fen , Liu Yan Jie , Wang Hai Dou , Yan Sheng Yuan
Published: October 2009

Thin walled tubes, particularly those of square or circular cross-section, are the common types of automobile crash-box, which equipped at the front end of a car, is one of the most important automotive parts for crash energy absorption. In the present work, energy absorption characters of square and circular cross-section thin walled tubes at low-velocity frontal impact are investigated respectively by using finite element (FE) method. The numerical simulations were carried out using the software LS-DYNA. The tubes were modeled using shell element of designation Belytschko-Tsay, which is suitable for large strain analyses. The FE model of the tube was validated by comparing the theoretical calculation results, experimental results and FE model results. Results show that on average the difference of these results was within 10%. The good correlation of results obtained show that the numerical analyses are reliable.
A Study of Delamination Mechanism of Thermal Barrier Coating under Thermal Cycling and Aging Condition by Residual Stress History
Authors: Waki Hiroyuki , Kobayashi Akira
Published: October 2009

Thermal barrier coatings (TBCs) have been employed for the insulation of substrates from high temperature in gas turbine plants. The TBC system consists of ceramic top coating, metallic bond coating and substrate. Delamination of the ceramic coating is important problem in TBC systems. In this paper, the delamination mechanism was studied by residual stress history under thermal aging and thermal cycle conditions. In-plane residual stress histories of ceramic coating and bond coating after thermal aging and cycling were measured by X-ray diffraction method. The residual stress under thermal cycling was also calculated by FEM analysis. The results obtained were as follows: (1) in-plane surface residual stresses of the coatings scarcely changed regardless of the increase of thermally grown oxidation (TGO). (2) high compressive thermal stress, residual stress at room temperature, in ceramic coating induced by thermal stress did not occur. It was found that stress of ceramic top coating was relaxed by micro cracks and driving stress of delamination was in-plane high compressive stress.
Pressure Reversal of Pipe during Hydrostatic Testing
Authors: Duan Qing Quan , Zhang Hong , Ji Ya Feng
Published: October 2009

The purpose of this paper is to discuss the plastic deformation and pressure reversal of pipe during hydrostatic testing. The higher the test pressure, the smaller the number of defects that remain undetected. In order to study the effect of hydrostatic testing, full scale burst experiments were carried out with API 5L X65 SSAW pipes of 660mm outside diameter and 12.5 mm wall thickness. Nine spiral oriented deflects had been machined in the weld. Deformations of deflects were measured. The pressure reversal was computed. It can be concluded that if a hydrostatic test can be successfully accomplished without the failure of any defect, the likelihood of a pressure reversal will be extremely small.
Evaluation of Structural Strength in Body Structure of Freight Car
Authors: Yoon Sung Cheol , Kim Jeong Guk , Jeon Chang Sung , Choe Kang Youn
Published: October 2009

To check the structural strength of the body of the newly–made container freight car, load was added to the underframe of the container freight car. The objective of this study is to evaluate whether or not the underframe of a freight car under the maximal strength is safe. A freight car for transporting railroad freight is usually designed and made of SM490YA steel and SM490Y steel. The carbody of rolling stock is a principal structure that supports major equipment of the underframe and the container freight. Therefore, the strength evaluation of this structure is important. Both structural analysis and loading test were performed under the loading condition. Prior to the evaluation of structural strength, finite element method software was used for structural analyses on stress distribution in a carbody of a freight car. The strain gauges were attached on the carbody based on FEM results. The actual vertical loading test and horizontal compression loading test were conducted
Study of Breakage at Bottleneck Seal of Liquid Packaging Bags
Authors: Shimamoto Akira , Aoki Hiroyuki , Futase Katsunori
Published: October 2009

The shapes and types of containers for foods, drugs and medicines, and cosmetics and detergent refills are diverse: glass bottles, cans, PET bottles and laminate-film liquid packaging bags are examples. In recent years, to increase the ease of pouring out the contents of laminate-film liquid packaging bags, the shape of the heat seal has been changed from a flat seal to a bottleneck seal. However, the large number of bottleneck seal ruptures of liquid packaging bags due to impact load during the transport, loading and unloading of packaged products has been a problem. In our previous study, we investigated impact peel strength in the heat-sealed area of a laminate film; however, the effects of the bottleneck seal shape and heat-sealed area width on impact peel strength and rupture occurrence have not yet been clarified. In this study, experiments were carried out to clarify the effects of the flat and bottleneck seal shapes, as well as heat-sealed area width, on impact peel strength and bag rupture occurrence. The following two films were used : (1) a multilayered laminate film with barrier characteristics against oxygen and water vapor, which is frequently used for liquid packaging bags owing to its high efficacy in food quality preservation, and (2) a multilayered laminate film without barrier characteristics. On the basis of the results obtained, we established, for the first time, a new standard regarding bottleneck seal shape and heat-sealed area width.
Investigation of Thermo-Mechanical Properties of Slurry Based Thermal Barrier Coatings under Repeated Thermal Shock
Authors: Nguyen Phuc , Kotousov Andrei G. , Ho Sook Ying , Wildy Stuart
Published: October 2009

Thermal Barrier Coatings have existed for over 40 years, and with in the last 15 years their use in industrial applications has dramatically increased. Thermal Barrier Coatings (TBCs) are currently used in gas turbines, diesel engines, throughout aerospace and nuclear power industries. The purpose of TBC is to reduce temperature and thermal stresses, and, as a result, increase the reliability and life of load-bearing components subjected to high temperature or temperature flux. However, TBCs often fail under thermal cyclic loading with reliability still being the major issue impeding their wide-spread applications.
The focus of this work is on experimental investigations of zirconia/nickel graded TBC system, subject to thermal shock loading. The graded TBC systems were fabricated utilising a recently developed slurry spray manufacturing technique. This is a robust technique, and is able to cover large and curved surfaces at low cost, and provides many advantages in comparison with its alternatives. This paper describes the developed technique and presents selected results of thermo-mechanical and fracture testing of the TBCs including graded coatings fabricated using this new technique.
Effect of Plate Thickness and Load History on Fatigue Crack Growth
Authors: Codrington John , Kotousov Andrei G. , Wildy Stuart , Ho Sook Ying
Published: October 2009

A new theoretical approach is presented for investigating fatigue crack growth in plates of finite thickness. The developed approach utilizes a modified strip-yield analysis and the concept of plasticity-induced crack closure. A number of typical fatigue crack growth phenomena are investigated including the thickness effect on constant amplitude fatigue crack growth, retardation due to a tensile overload cycle, and short crack growth from sharp notches. Theoretical predictions are compared with experimental data and are found to be in very good correlation.
Effect of Radical Nitriding on Fatigue Strength of Ni-Base Superalloy
Authors: Morino Kazuhiro , Kawagoishi Norio , Yamane K. , Fukada K.
Published: October 2009

In order to investigate the effect of nitriding on the crack initiation and propagation behavior of Ni-base super alloy, Alloy 718, rotating bending fatigue tests were carried out until 108 cycles at room temperature. By nitriding at 500°C for 12h, compound layer of about 5μm in thickness was formed and the initiation of a fatigue crack was strongly suppressed causing the increase in fatigue strength. A crack initiated in brittle manner at the compound layer in all of fractures. However the crack propagated in ductile manner controlled by the property of the base alloy. That is, there is no or little influence of nitriding on the crack growth rate of the alloy.
Ultrasonic Fatigue of Radical Nitrided Ni-Base Superalloy
Authors: Yamane K. , Kawagoishi Norio , Morino Kazuhiro , Fukada K.
Published: October 2009

Ultrasonic and rotating bending fatigue tests were carried out for aged and nitrided Ni-base super alloys to investigate the effects of loading frequency and nitriding on fatigue strength. Loading frequencies were 19.5 kHz under ultrasonic and 50 Hz under rotating bending, respectively. Fatigue strength under ultrasonic was higher than that under rotating bending in both alloys. Moreover, in both tests, fatigue strength was improved by nitriding. The increase in fatigue strength by nitriding was large in ultrasonic fatigue. These results were discussed through the successive observation of fatigue process at specimen surface and fracture surface observation.
Molecular Dynamics Simulation on Crack Propagation for Magnesium
Authors: Xu Shu Sheng , Zeng Xiang Guo , Chen Hua Yan
Published: October 2009

The crack propagation for pure Magnesium at an atomic scale level under external loading was carried out by using a molecular dynamics method. In this study, the Modified Embedded Atom Method (MEAM) was used to characterize the interactions of atoms and the Newtonian equations were solved by Velocity-Verlet algorithm. The crack propagation and failure processes were observed around the crack tip. The calculation results reveal that vacancies were formed near the crack tip during the failure processes for pure Magnesium, and the coalescence between crack tip and vacancies induced the crack growth with the increase in loading.
On Buckling of Long Interface Cracks
Authors: Kotousov Andrei G. , Harding Steven
Published: October 2009

The paper deals with the buckling instability of long interface cracks subjected to shear and tensile (compressive) loading parallel to the interface. A simplified mathematical model is developed within the Kirchhoff’s plate bending theory; and a general semi-analytical solution is obtained based on the classical strategy for solving for the Euler buckling load. Asymptotic solutions are derived for extreme cases of the applied shear to tensile (compressive) load ratios. The obtained results correlate well with previous numerical studies and can be used to analyze many traditional problems in composite as well as many others, for example, the problem of triggering snow avalanches.
A Consideration of the Measurement of Macro-Stresses in Non-Metallic Materials
Authors: Nakhodchi S. , Hilson Gabrielle , Smith David John , Flewitt Peter E.J.
Published: October 2009

In this paper the challenges associated with the determination of within section macrostresses in the non-metallic materials porous reactor core graphites, glasses and thermally grown oxides, will be considered, with respect to the length-scale over which such measurements are required. Examples are briefly presented to demonstrate the capability of the methods selected, which include deep hole drilling and photoluminescence and Raman spectroscopy. These techniques span the length-scale from micro-metres to tens of millimetres. The measured values will be discussed with respect to the confidence with which these techniques may be applied and hence benefits for life/integrity evaluation.
High Cycle Fatigue Behavior of Cold Forging Die Steel
Authors: Ebara Ryuichiro , Nohara R. , Ueji Rintaro , Ogura A. , Ishihara Y. , Hamaya S.
Published: October 2009

High cycle fatigue behavior of the representative cold forging die steel, YXR3 with Rockwell C scale hardness number of 60.0 is investigated. Axial fatigue strength of plane and notched bar specimens with stress concentration factor, Kt of 1.5, 2.0 and 2.5 is presented. The emphasis is placed upon the subsurface crack initiation observed on notched specimens failed at number of cycles over than 106 cycles. Crack initiation and propagation mode of cold forging die steel is discussed with respect to fracture surface morphology.
Study on Structural Vibration Control by Using Shape Memory Alloy
Authors: Zhou Bo , Liu Yan Ju , Zou Guang Ping , Leng Jin Song
Published: October 2009

Shape memory alloy is a good candidate for realizing the passive control of structural vibration due to its excellent characteristic of energy dissipation. In this paper, the damping characteristic of shape memory alloy is quantitatively described based on Liang’s phase transformation model and thermo-mechanical constitutive equation for shape memory alloy. The vibration performances of a beam structure with shape memory alloy damper are investigated based on basic knowledge of vibration theorem. Numerical calculations show that the vibration of beam structure is well reduced by using the shape memory alloy damper.
Numerical Computation of the Overall Moduli of Two Dimensional Infinite Media with Cracks
Authors: Yin H.P.
Published: October 2009

The overall elastic moduli of a solid are changed when the solid is damaged by cracks. For a finite solid, the size influence has been investigated and it has been found that for a given crack density, increasing crack size reduce the overall moduli [1]. For an infinite solid, it is obviously impossible to make the computation with all cracks. Classical methods suggest computing the overall moduli with the solution of the crack opening displacement of one single crack. The interaction between cracks is neglected or taken into account approximately. In this paper, the overall moduli of two dimensional infinite solids with cracks are computed numerically. From numerical simulations, it has been found that the interaction between cracks can be neglected if the distance between them is three times larger than the crack size. So one can compute the opening displacement on one crack with the presence of cracks nearby and use the crack opening displacement to compute the overall moduli. The numerical values are smaller than those of the method of diluted distribution but greater than those of the differential scheme and the self consistent method. They are also slight greater than the numerical results of bounded cracked solids. For small values of crack density however, the numerical results of both infinite solids and bounded solids are close to the estimation of the differential scheme.
On the Use of the Theory of Critical Distances to Estimate KIc and ∆Kth from Experimental Results Generated by Testing Standard Notches
Authors: Susmel Luca , Taylor David
Published: October 2009

The present paper is concerned with the use of the Theory of Critical Distances (TCD), applied in the form of the Point Method (PM), to estimate the range of the threshold value of the stress intensity factor, Kth, as well as the plane strain fracture toughness, KIc. In more detail, by reanalysing a large amount of experimental data taken from the literature, it is proved that Kth can successfully be evaluated through the plain fatigue limit and another fatigue limit generated by testing samples containing a known geometrical feature, whereas KIc is suggested here as being estimated by using experimental results generated by testing samples weakened by notches of different sharpness. The validation exercise summarised in the present paper fully confirms that the TCD is not only a reliable method suitable for performing the static and fatigue assessment of real components, but also an efficient experimental strategy capable of accurately estimating the classical Linear Elastic Fracture Mechanics (LEFM) material properties.
Fatigue Crack Propagation in Thin Structures
Authors: Hutař Pavel , Seitl Stanislav , Náhlík Luboš , Knésl Zdeněk
Published: October 2009

The influence of specimen thickness on fatigue crack behaviour has been investigated. To this aim the fatigue crack propagation rate has been measured on two different types of test specimens with varying thickness. The change of stress singularity exponent for the crack front due to vicinity of the free surface is considered. To explain the effect of stress singularity changes on obtained experimental results a methodology based on generalized stress intensity factor and strain energy density concept has been used. It is shown that for materials with Poisson’s ratio of about 0.3 the free surface effect does not play a decisive role for specimens with a low level of in-plane constraint but can influence fatigue crack propagation rate in the case of geometries with a high level of the constraint.
Numerical Scheme for Micro-Damage Mechanism of Composite Propellant
Authors: Zhao J.L. , Qiang H.F.
Published: October 2009

HTPB propellant is the high filled particulate elastomeric matrix composite. Debonding of particle/matrix interfaces can significantly affect the macroscopic behavior of composite propellant. How to model the propellant material and describe damage processes to discover damage mechanism has been a long-standing question. This paper used the bilinear cohesive law with different parameter values for particle/matrix interfaces to study interface debonding. By analyzing the damage evolution in two model particulate composite systems with finite element method, the scheme was shown to capture effects associated with the interface strength and the interactions between particles.
Numerical Modelling of Viscoelastic/Damage Behaviour of Cortical Bone
Authors: Lovrenić-Jugović Martina , Tonković Zdenko , Skozrit Ivica
Published: October 2009

An efficient computational algorithm for the integration of the viscoelastic/damage constitutive model at the material point level is derived. For the presented constitutive model, material parameters, obtained experimentally for human cortical bone, are taken from literature. The derived algorithm in conjunction with the Jacobian matrix is implemented in the finite element (FE) code ABAQUS by using the user subroutine UMAT. The accuracy of the proposed algorithm is demonstrated.
Numerical Analysis of Fracture Parameters of Multiple Interacting Cracks
Authors: Liu Yong Jie , Wang Qing Yuan , Zeng Xiang Guo , Lv Da Li
Published: October 2009

Multiple interacting crack problems for 3-point bending specimen were studied in this article. Two symmetrical minor cracks were placed in the structure, besides a main crack at the middle, and using the finite element method program ABAQUS, the energy release rate (G) and the stress intensity factor (SIF) were evaluated based on the virtual crack closure technology（VCCT）in conjunction with finite element analysis(FEA). Then, effects of variation in relative lengths and locations of the minor cracks on the stress intensity factors of the main crack were obtained and analyzed. Finally, the approach was applied to dynamic analysis, and influences of interacting effects among the cracks on dynamic fracture parameters were also studied.
An Investigation on Low Cycle Lifetime of Al2024 Alloy
Authors: Vyshnevskyy Andriy , Khan Shehzad , Mosler Joern
Published: October 2009

One of the important considerations in the design of components is the estimation of cyclic lifetime and analysis of the critical regions of a construction. The local approach of lifetime estimation using continuum damage mechanics (CDM) has shown a great potential in predicting material failure not only for monotonic, but also for fully reversed loadings. In this paper, the CDM model of Desmorat-Lemaitre [1] was investigated regarding the prediction of cyclic lifetime. A series of experiments on tension specimens with different geometries were performed. The latter were used for the determination of model parameters as well as for the validation of the predictive capability of the model.
Improvement of Corrosion Behavior of the Cu-Ni Alloy with Electroless Ni-P Plating
Authors: Li Qing Fen , Fu Yu Dong , Wang Hai Dou , Wang Jun
Published: October 2009

The microbiological influenced corrosion (MIC) behavior of the Cu-Ni alloy with or without Ni-P plating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the uncoated specimens in both the sterilized medium and the SRB solution when the specimens coated with Ni-P plating were still in good condition. Since the Ni-P plating may offer both barrier and cathodic protection to the base metal. Besides, the structures of Ni-P plating and the passive film on the surface of the Ni-P plating are high uniform and amorphous without any structure defects. The non-crystalline structure may improve the corrosion resistance because it does not have crystalline defects such as dislocation, grain boundary, twin and so on which may cause corrosion easily. It is concluded that corrosion behavior of the Cu-Ni alloy with electroless Ni-P plating was improved greatly.
Linking Elastic Nonlinearity and Cracks Growth in Mortar Samples
Authors: Bruno Caterina L.E. , Antonaci Paola , Bocca Pietro G. , Gliozzi Antonio S. , Scalerandi Marco
Published: October 2009

One of the signatures of the presence of cracks in a sample is the nonlinearity in its elastic response to an impingent ultrasonic wave. The Fourier analysis is often inadequate to monitor the evolution of nonlinearity, since the signal-to-noise ratio of higher order harmonics is very low. In order to overcome this drawback, we suggest an alternative procedure to extract nonlinearity indicators from a recorded ultrasonic signal, based on the amplitude dependence of the response of the system. The procedure is first described and then used to analyse the evolution of the nonlinearity due to cracks induced by a quasi-static loading in mortar samples. Our approach allows to distinguish the compaction phase from the micro-damage progression and the pre-rupture phases.
The Configurational Force Concept in Elastic-Plastic Fracture Mechanics−Instructive Examples
Authors: Schöngrundner R. , Kolednik Otmar , Fischer Franz Dieter
Published: October 2009

This paper deals with the determination of the crack driving force in elastic-plastic materials and its correlation with the J-Integral approach. In a real elastic-plastic material, the conventional J-integral cannot describe the crack driving force. This problem has been solved in Simha et al. [1], where the configurational force approach was used to evaluate in a new way the J-integral under incremental plasticity conditions. The crack driving force in a homogeneous elastic-plastic material, Jtip, is given by the sum of the nominally applied far-field crack driving force, Jfar, and the plasticity influence term, Cp, which accounts for the shielding or anti-shielding effect of plasticity. In this study, the incremental plasticity J-integral and the crack driving force are considered for a stationary and a growing crack.
Crack Behaviour in Laminar Ceramics with Strong Interfaces
Authors: Náhlík Luboš , Šestáková Lucie , Hutař Pavel
Published: October 2009

The paper deals with crack propagation in ceramic laminates. Assumptions of linear elastic fracture mechanics and small scale yielding are considered. Crack behaviour in a ceramic laminate body under external loading is investigated. Strong residual stresses due to different coefficients of thermal expansion of individual material layers are taken into account in finite element calculations. The change of crack propagation direction at the material interface is estimated on the base of the strain energy density factor and maximum tangential stress criteria. The influence of thickness of laminate layers on crack propagation direction is estimated. The stepwise crack propagation through the Al2O3-ZrO2 ceramic laminate is numerically estimated. It can be concluded that good agreement between the estimated crack path and experimental data was found.
A New Methodology for Estimating Fracture Criterion of Thin Sheets
Authors: Ray Kalyan Kumar , Patra Ashmita , Bhattacharjee Debashish
Published: October 2009

A simple and reliable method has been proposed for determining fracture toughness of thin sheets. The principle of the method considers that critical crack opening displacement (c) corresponds to a specific amount of load drop during fracture toughness tests. The suggested technique yields c value for an interstitial free (IF) steel as 2.04 mm in excellent correspondence with an indirect estimate of 1.97 mm from the popular energy extrapolation technique. The magnitude of c for IF steel sheets is found to decrease with decreasing thickness in agreement with the expected variation of this criterion with specimen thickness in gross yielding fracture mechanics (GYFM) regime.
Rolling Contact Fatigue of White Etching Layer on Pearlite Steel Rail
Authors: Seo Jung Won , Kwon Seok Jin , Jun Hyun Kyu , Lee Dong Hyung
Published: October 2009

White etching layer(WEL) is a phenomenon that occurs on the surface of rail due to wheel/rail interactions such as excessive braking and acceleration . Rolling contact fatigue(RCF) cracks on the surface of rail have been found to be associated with the WEL. In this study, we have investigated RCF damages of white etching layer in the laboratory using twin disc testing. These tests consist of wheel flat tests and rolling contact fatigue tests. The WEL has been simulated by wheel flat test. It has been founded that the WEL with a bright featureless contrast is formed on the surface of specimen by etching. Rolling contact fatigue test was conducted by using flat specimens with the WEL generated by the wheel flat test. It has been observed that two types of cracks occur within the specimen, the first initiated at the interface between the WEL and the undeformed area, the second initiated at the center of the WEL.
Analysis of Hot Spots Evolution on Brake Disc Using High-Speed Infrared Camera
Authors: Kim Jeong Guk , Kwon Sung Tae , Yoon Sung Cheol
Published: October 2009

The hot spot generation has been considered as the main degradation mechanism in railway brake disc. Therefore, the understanding of hot spots, also called hot judder, which is undesirable low frequency vibrations developed by non-uniform contact area between brake pad material and brake disc, is important for a better understanding of material design as well as enhancement of materials properties in railway brake disc. Also, infrared (IR) thermography is a powerful NDE technique for the characterization of thermal phenomenon in engineering components and/or systems including engineering materials. The high-speed IR camera provides the measurement of temperature change during brake operation as well as the images of temperature contour on the brake disc surface. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. Moreover, based on obtained thermographic images of hot spots, the hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed.
Fatigue Resistance and Crack Initiation Mechanisms in High-Thickness Aircraft Al-Alloy and Steel Sheets after Water Jet Cutting
Authors: Černý Ivo , Mikulová Dagmar
Published: October 2009

Water jet cutting is an advanced technology of separating and machining materials. It is well known, however, that fatigue properties are particularly strongly affected by surface conditions and quality of surface layer. Water jet cutting was applied to two types of aircraft sheets, namely Al-alloy sheet of fairly high thickness 50.8 mm and steel sheet of thickness 25 mm. Fatigue resistance and crack initiation mechanism of the materials after the cutting were compared with those studied using a reference batch of specimens manufactured by fine milling and grinding, respectively. Character of surface damage caused by water jet cutting resulted in a considerable reduction of fatigue strength in comparison with milled or ground surface, respectively. The results are evaluated considering effects of microscopic character of surface conditions, like numerous micronotches caused by the technology used, on fatigue initiation process, as well as effects of subsurface inclusions on fatigue crack initiation and early growth.
Simulation of Stress-Corrosion Cracking by the Cohesive Model
Authors: Falkenberg Rainer , Brocks Wolfgang , Dietzel Wolfgang , Schneider Ingo
Published: October 2009

The effect of hydrogen on the mechanical behaviour is twofold: It affects the local yield stress and it accelerates material damage. On the other hand, the diffusion behaviour is influenced by the hydrostatic stress, the plastic deformation and the strain rate. This requires a coupled model of deformation, damage and diffusion. The deformation behaviour is described by von Mises plasticity with pure isotropic hardening, and crack extension is simulated by a cohesive zone model. The local hydrogen concentration, which is obtained from the diffusion analysis, causes a reduction of the cohesive strength. Crack extension in a C(T) specimen of a ferritic steel under hydrogen charging is simulated by fully coupled diffusion and mechanical finite element analyses with ABAQUS and the results are compared with test results.
Simultaneous Edge Debonding Monitoring and Repair of Dynamically Loaded Concrete Structures Strengthened with Smart Composite Materials
Authors: Providakis Costas P.
Published: October 2009

The present work considers the possibility of simultaneous health monitoring and active repair of the edge debonding in dynamically loaded smart concrete structures strengthened with fiber reinforced plastic (FRP) composite materials. This is achieved by using local piezoelectric (PZT) actuators/sensors, the electro-mechanical admittance concept and extreme value statistics.
Fatigue Behaviour of a Stainless Steel Based on Energy Measurements
Authors: Atzori Bruno , Meneghetti Giovanni , Ricotta Mauro
Published: October 2009

In this paper the low cycle fatigue behaviour of an AISI 304L stainless steel is analysed on the basis of energy concepts. In particular during the fatigue tests different forms of energy in a unit volume of material per cycle involved in the fatigue process were measured: the mechanical energy expended was evaluated from the area of the hysteresis loops, while the energy released as heat by the specimen to the surroundings was estimated from surface temperature measurements by means of an infrared camera. By subtracting the mechanical input energy and that released as heat, the energy stored in a unit volume of material at fracture was calculated for each tested specimen. The mean value obtained from different specimens is in agreement with the energy absorbed by the material in a static test.