bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Fabrication of a Piezoelectric Bend Mode Drop-on-Demand Inkjet Printhead with Interchangeable Nozzle
Authors: Wu Sen Yang , He Yong , Fu Jian Zhong , Shao Hui Feng
Published: September 2013

The drop-on-demand (DOD) inkjet printing technology has been widely used in many fields and several types of droplet generators are developed. This paper presents the design, fabrication and tests of a piezoelectric bend mode drop-on-demand inkjet printhead with interchangeable nozzle. A disk-type PZT is actuated to push the liquid out of inkjet printhead by a function generator, and a droplet is formed because of surface tension. The interchangeable nozzle design enables the same printhead to be fitted with nozzles of different orifice size, thus a clogged nozzle can be easily removed for cleaning or replacement. An experimental platform for micro-droplet jetting is built in this paper. The droplet formation is recorded by a CCD camera as pictures, which can be used to measure the droplet dimension. The experiments are carried out by using the self-developed bend mode piezoelectric inkjet printing system. The influence of the drive parameters on the droplet quality is also studied by dispensing water.
The Optimal Design of the Plasma Discharge Structure of the Far Zone of the Hollow Cathode
Authors: Wen Yi Fang , Rui Yan Nian , Chen Chuang , Wang Hong Wei
Published: September 2013

The discharge of RF hollow cathode far zone plasma has advantages of high ion concentration, easy to implement the processing of a large area, given more and more attention. The characteristics of hollow cathode plasma flow have a great relationship with the hollow cathode nozzle structure. How to design the hollow cathode nozzle discharge structure accurately and conveniently is the key problem of the hollow cathode far plasma surface treatment. This article builds a hollow cathode plasma discharge self-consistent model; derive the relationship between the discharge current of the hollow cathode plasma and the hollow cathode nozzle structure. Optimize the design of the hollow cathode discharge structure using discharge particle simulation software, to achieve a fast and accurate design and the purpose of efficient plasma surface modification.
Topology Optimization of Suspension of the Hard Disk Drive Based on SIMP Method
Authors: Yang Shu Yi , Li Hong , Ou Yang Bin
Published: September 2013

in order to guarantee the reliability of the hard disk drive data read/write and slider positioning accuracy, the suspension first order bending frequency, first order torsional frequency, first order sway frequency single objective topology optimization model which were based on solid isotropic elastic material penalty (SIMP) method were put forward, and the suspension multi-objective topology optimization model was defined by using the weighted method. Through the topology optimization design the hard disk drive suspension new topological structure was obtained. The results show that hard disk drive suspension single objective and multi-objective topology optimization design objective frequency are large promote than that of the initial design.
Unified Modeling for Input Forces and Input Vectors for Two Scissor Lifting Mechanisms
Authors: Zhang Wei , Zhang Xue Fei , Yan Chao
Published: September 2013

Scissor lifting mechanisms are widely equipped on airport ground support facilities, in this paper, we propose a unified modeling process for two special SLMs by establishing the expression of input motion vectors and input force vectors and test the results by three proposed cases. A characteristic triangle and corresponding parameters are introduced for any configuration. The presented method provides a reference mode for studying scissor lifting mechanism.
Methods of Gear Damage Assessment Based on Modal Parameter Identification
Authors: Ma Jin Bao , Zhang Jian Yu , Liu Xin Bo
Published: September 2013

With the evolution and degradation of mechanical fault, changes of the structural inherent characteristics will directly affect the overall response of system. Spur gear, which worked as the research object, is to be explored on the changes of modal parameters under different damage state. Optimum driving-point mobility and modal parameter identification is achieved by comprehensive utilization of experimental modal analysis and finite element analysis. is used to determine the experiment results is whether accurate or not. Then comparing with the differences of modal parameters, the preliminary judgment of gear damage can be made. According to the experimental data of different gears, theis taken to complete the correlation analysis and to judge the degree of the damage. The results shows that provide an effective basis for the identification of vibration mechanism and vibration characteristic of fault gear.
The Production System Automatic Layout Based on Simulation
Authors: Lv Chao , Liu Shuang , Wang Shi Ming , Cai Bei
Published: September 2013

The U-Shaped layout and function of production system is studied, the purpose is showing how the layouts and their main function influence each other, thus to provide enlightenments and references to improve the design of the production system layout. The simple automatic arrangement system is presented based on Plant Simulation software and focused on an equipment layout problem. The automatic layout system is an automatic layout system of workshop layout according to data; adopt the method of simulation modeling combined with optimization of the workshop layout. According to the different optimization objectives, the user can get a different optimal solution. Through simulation, we can get the default layout of the carrying amount, size and arrangement, combined with the enterprise's actual situation. The appropriate adjustments and production efficiency of production workshop are improved, and the operation time of manual modeling is shortened.
Numerical Simulation of Nonlinear Sloshing in a 2D Vertically Moving Container
Authors: Zhang Hai Tao , Sun Bei Bei
Published: September 2013

Nonlinear liquid sloshing problems in a vertically excited tank are numerically simulated by using a finite difference method. First, the irregular liquid domain is mapped onto a rectangular area by σ-transformation. Then, in the process of time iteration, the free surface is forecasted to estimate the boundary of the next time layer; and some nonlinear terms are approximated to derive linear equations. Free surface elevation and sloshing forces in the vertical sloshing process can be calculated precisely by this method.
Precision Straightening Method of Thin-Walled Seamless Steel Pipes
Authors: Li Lian Jin , Yang Jia
Published: September 2013

With the highest product performance, quality and reliability requirements, oil casing is the most demanding service conditions in the oil and gas fields. However, when solving with thin-walled seamless steel pipes by the existing straightening theory, the cross section distortion phenomenon shall not be considered, and when the proportion of diameter to wall thickness increases, an ideal straightening effect can't be obtained. With the elastic-plastic bending straightening theory, this paper analyzes straightening process of thin-walled seamless steel pipes, studies the relationship of the flattening rate, deflection and straightening force in thin-walled pipes straightening, deduces the best reduction calculation method in the practical six roller skew rolling straightening machine, and in the meantime, results of several steel pipes flattening rate are compared.
Simulation and Experimental Study on Rear Frame Strength of Winch Lashing Car
Authors: Yue Jing Tao , Pu Hui , Tao Xiang He
Published: September 2013

Heavy general transport vehicles are recommended as lashing points during rescue operations of winch. Taking SX2190 heavy transport vehicles frame as the experimental object, this paper introduces contents and methods of the test, and gets evaluation result of the rear frame through finite element simulation and experimental validation of the real frame-towing hook system for winch lashing car.
Shape Controllable Preparation of PbS Crystal by a Simple Solvothermal Method
Authors: Zhao Zhong Biao , Wang Peng , Fan Li Bo , Chen Zi Fa , Wang Chun Meng
Published: September 2013

Hierarchical eight-arm, star-shaped lead sulfide (PbS) crystals have been successfully synthesized by a simple hydrothermal method. When pyridine was used as solvent, candy-like PbS crystal was obtained. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform-infrared (FT-IR) measurements.
Effect of Buffer Layer Thickness on Fatigue and Residual Stress of Welded High-Strength Low-Alloy
Authors: Zhang Chun Guo , Lu Peng Min , Li Jun Hong
Published: September 2013

The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.
Welding Defects Classification Based on Multi-Weights Neural Network
Authors: Hua Liang , Xue Peng , Tang Jin Ping , Jin Hui , Zhang Qi
Published: September 2013

Incomplete fusion and incomplete penetration are two types of damage serious welding defects. These two kinds of defects have the similarity in the features in X-ray imaging. Identifying the two kinds of defects automatically and accurately can improve the welding technology and improve the quality of welding effectively. The causes of defects and features of X-ray images are described in the paper. The welding defects calssification method based on multi-weights neural network is put forward in the paper. The multi-weights neural network based on graphic geometry theory is introduced, which uses the geometrical shape in high dimensional space to cover the same class defect samples via constructing multi-weights neural network. The experimental results proved the effectiveness of the algorithm.
The Influence of Material Parameters on Penetrator Embedding Pre-Perforated Steel Plate Vertically
Authors: Zhao Jing , Du Zhong Hua , Zhong Kun , Wang Xian Zhi
Published: September 2013

In this paper, the fracture analysis model about the penetrator embedding pre-perforated steel plate vertically is set up. The threshold target impact velocity expression (if the penetrators fracture failure occurs) is obtained. In addition, the influence of the penetrators material parameters on the fracture failure, that is, the threshold target impact velocity, are listed and analyzed, such parameters including materials yield stress, tangent modulus, density and failure strain. The results show that the threshold velocity increases along with the material yield stress, tangent modulus and failure strain, inversely along with the material density. This study would provide strong theoretical and engineering basis for the penetrator design and analysis.
The Simulation of Stem Cutting and Parameter Optimization for Power Station Valve
Authors: Zou S.H. , Wang H.L. , Yang C.X. , Shi Y.P. , Ge J.H.
Published: September 2013

We expound the finite element simulation and the key points of metal turning by the material properties of the stem in this paper, and select the proper material constitutive equation, then use the adaptive meshing technique, and then finite element modeling was carried out on the valve stem in the professional finite element software Advantedge FEM. The optimization scheme we designed of finite element simulation for the valve stem through the finite element software Advantedge FEM, and we research the influence of the amount of feed and speed cutting process about the cutting force and the cutting temperature.
Research and Application of Electromagnetic Field Strength in Metallic Mineral Separation
Authors: Sun Yu Feng , Che Jun Hua
Published: September 2013

The paper established the mathematic model with the help of computer to analyze the impact of electromagnetic field strength in metallic mineral separation. And then using Finite Element Method of electromagnetic partial differential equations solved the model. The relationship between current density and magnetic field strength was obtained. Finally, analysis results were applied to the actual study for the dry magnetic separation equipment and research results demonstrated the feasibility of this approach.
Analysis of Characteristics of Dynamic and Static Component of the Cutting Force Signal in Turning
Authors: Jin Yu Rong , Ren Xiao Zhong , Li Bin
Published: September 2013

The characteristics of dynamic and static component of the cutting force signal were analyzed when the coated tool was used to cut gray cast iron. It is found that the whole and local of dynamic cutting force signal has self-similarity. Then the dynamic fractal dimension D was extracted by means of fractal theory, and the feature quantity M was extracted from the static cutting force signal. Research shows that the dynamic fractal dimension D of cutting force signal and static characteristic quantity M are varied with the cutting time. Their varying laws can be used to monitor the wear condition of coated tool effectively.
Simulation Analysis on Selection of Laser Cladding Repair Material for the Diesel Engine Crankshaft Crack
Authors: Ren Hui Fang , Ren Jia Long , Zhao Li Gang , Wang Qing Xian
Published: September 2013

For solving the crack in crankshaft, laser cladding remanufacturing was involved. There were three key points about laser cladding remanufacturing discussed in this paper.The three key points included process flow , process environment and laser cladding materials selection . Using the ANSYS analysis software, the simulated analysis of the temperature field , stress field and the residual stress of the three kinds of cladding layer have been carried on, the best cladding materials for single-throw crankshaft crack of base material 45# is determined by studying the repaired results about Iron-based,Cobalt-based,Nickel-based self-fluxing alloy powder cladding materials.
Thermal Simulation on Coarse Grained Region of L415 Pipelines in High Sour Gas Field
Authors: Xu Xiao Long , Yang Jun , Cui Yun Long , Zhu Zhong Tao , Chen Hui
Published: September 2013

corrosions on gathering and long-distance pipelines in high sour gas field are often found on the HAZ, coarse grained region is the weakest region in the HAZ. We got L415 Pipelines coarse grained region of different heat inputs and post-treatments by welding thermal simulation, researched microstructures, hardness, impact energy and fracture, the result showed that, when the heat input is 25KJ/Cm, followed by annealing treatment with temperature 700°C for 1 hour, we can get good mechanical properties of coarse grained region.
Dynamical Identification Model of Laser Cladding Width in Metal Parts Laser Shaping Process
Authors: Jiang Shu Juan , Yu Fei Fei , Fu Mao Zheng
Published: September 2013

The dynamical model of laser cladding width is identified by the method of step response experiments. Mathematical models between the cladding width and the laser power, the scanning speed, or the powder flowrate are established respectively according to corresponding experimental results. Simulating experiment results verify the validity of these models. The dynamical identification lays foundation for the closed loop control in laser shaping process so as to improve the quality of the laser formed parts.
Analysis of Temperature and Residual Stress Distribution in Laser Welding for Ta/Mo Lap Joints Using FEM
Authors: Jin Liang , Song Fang Fang , Wei Guo Qiang , Guo Qi
Published: September 2013

A nonlinear transient three-dimensional finite element model for the laser welding process is developed to investigate the temperature and residual stress distribution. All the major physical phenomena associated to the laser welding process, including temperature dependent thermo-physical and mechanical properties are taken into account in the model. The heat input to the model is assumed to be a Gaussian heat source. Results show that the temperature distribution of laser welding is consistent with the actual, and along-welding line longitudinal stress and transverse stress are retained in the weld zone after laser welding and cooling to the room temperature.
A PbS Film Synthesized by Ultrasonic Wave Assisted Chemical Bath Deposition Method and its Application in Photoelectrochemical Cell
Authors: Zhao Zhong Biao , Wang Peng , Fan Li Bo , Chen Zi Fa , Yang Dong Luo
Published: September 2013

A Lead sulfide (PbS) film synthesized by ultrasonic wave assisted chemical bath deposition (CBD) method. The as-deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements. The photoelectrochemical (PEC) cell, with PbS/ITO/glass as a photo cathode and Na2SO4 (0.10 M) solution as an electrolyte, was constructed and investigated for PEC properties. The film shows a p-type conduction mechanism.
Microstructure and Properties of MoFeCrTiW High-Entropy Alloy Coating Prepared by Laser Cladding
Authors: Zheng Bo , Liu Qi Bin , Zhang Ling Yan
Published: September 2013

To obtain high-entropy alloys (HEAS) coating with excellent properties on Q235 steel, a kind of HEAS powders was designed. The HEAS coating was prepared uniformly on Q235 steel by laser cladding. By means of OM, XRD and microhardness tester, the microstructure and properties of the high-entropy alloy layer were investigated. The experimental results indicate that the phases in the high-entropy alloy coating is mainly MoFeCrTiW with simple BCC, whose lattice parameter is a-3.1256Å. The microstructure in the coating is mainly cellular crystal, on which dispersion precipitates exist. And in the near bottom of the coating, there is few precipitates, in the middle part of coating, the precipitates are larger than that of bottom coating, while in near top of coating, dispersion precipitates become largest. The maximum microhardness value of coating reaches 800HV0.98.
Investigation on the Thermal Stability of the Compounds Y3Fe29-xCrx
Authors: Wang Xiao Hua , He Wei , Zeng Ling Min
Published: September 2013

Binary compound Y3Fe29cannot be directly formed by rare earth Y and Fe and the third element M (non-iron transition elements) must be introduced to form ternary compound Y3(Fe,M)29. In this work, six alloys with compositions of the Y3Fe29-xCrx(x=1,2,3,4,5,6) were prepared and investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and differential thermal analysis (DTA). The study on the thermal stability of these compounds points to that the compoundY3(Fe,Cr)29is a high temperature phase and exists above 1100K. The alloys with single-phase of Y3(Fe,Cr)29was decomposed into Y2(Fe,Cr)17and Y(Fe,Cr)12annealed at high temperature 1100K.
Stopping Power for Ions Moving in Magnetized Plasma
Authors: Wang Gui Qiu , Chi Xiao Jiao
Published: September 2013

Stopping power of test ions in magnetized plasmas is investigated by means of linearized Vlasov Poisson theory. The influences of the magnetized field, the angle between the test particle velocity and magnetized field, and certain plasma densities and temperatures on the stopping power are studied. Simulation results show that the stopping power emerges a peak around the plasma thermal velocity due to the electron excitation. When the magnetized field is strong, the stopping power is strengthened; while when the magnetized field is weak, the stopping power is weakened.
Effects of Variable Loading on Residual Fatigue Life of the Railway Wheelset
Authors: Pokorný Pavel , Náhlík Luboš , Ševčík M. , Hutař Pavel
Published: September 2013

The paper deals with the effects of variable loading on residual fatigue life of the railway wheelset. The railway wheelsets can include some cracks created during manufacturing process or during previous operation. Therefore, it is important to know how the existing cracks will behave during further service of the train. The experiments show that the fatigue crack growth rate depends not only on size of the load amplitudes in a loading spectrum, but it depends also on the sequence of load amplitudes. Taking into account interaction effects of overloading cycles requires use a method that calculates increments of crack length in each cycle, i.e. cycle-by-cycle. One of such methods represents generalized Willenborg model. This model was used for residual fatigue life time estimations of railway wheelset and results obtained were compared with classical approach, which did not take into account interaction effects. Results obtained can be used for establishing of service intervals of railway wheelsets.
Application of the Monkman-Grant Relationship for Ultrafine-Grained Metallic Materials
Authors: Kvapilová Marie , Dvořák Jiří , Král Petr , Svoboda Milan , Sklenička Václav
Published: September 2013

The applicability of the Monkman-Grant relationship was analyzed and validated for ultrafine-grained metallic materials under investigation. A special attention has been given to the creep damage tolerance factor which is defined as the ratio of the strain to fracture to the Monkman-Grant ductility and which describes the coupling between creep deformation and damage based on continuum creep damage approach. It was found, that ultrafine-grained materials generally obey the Monkman-Grant relationship, however, the relationship is especially suitable for materials exhibiting short secondary creep and long tertiary creep stages when dislocation-controlled creep is dominant.
Flexural and Shear Capacity Evaluation of Reinforced Ultra-High Strength Concrete Members with Steel Rebars
Authors: Bae Baek Il , Choi Hyun Ki , Choi Chang Sik
Published: September 2013

High-strength concrete is widely used in construction field. The growth has been possible as a result of recent developments in material technology and a demand for high-strength concrete. High-strength concrete has different mechanical properties from normal-strength, as many researches mentioned about. However, the existing equations and procedures for prediction of ultra-high strength concrete are based on tests using normal-strength concrete, yet. In this study, experiments on ultra-high-strength steel fiber reinforced concrete beams with 2% volume fraction of steel fiber and 200MPa of compressive strength have been conducted. Test was conducted by two point loading with 2,000kN actuator for slender test specimen which have varied shear-span to depth ratio. Using test results with several assumptions, an empirical equation for flexural strength and shear strength of ultra-high-strength steel fiber reinforced concrete beams have been proposed.
Grain Boundary Fracture Behavior and Segregation of P under Low Tensile Stresses in Steel 2.25Cr1Mo and 12Cr1MoV
Authors: Fu Yu Dong , Li Qing Fen
Published: September 2013

Experimental investigation about the grain boundary fracture behavior and segregation behavior of phosphorus under low tensile stresses in steel 2.25Cr1Mo and 12Cr1MoV was carried out in this paper. AES (Auger electron spectroscopy) experiments and dynamic analyses on the non-equilibrium grain-boundary segregation (NGS) of phosphorus and the SEM photos of grain boundary fracture in Auger specimens of both steels were obtained. The variation of phosphorus segregation level in grain boundary at different aging time was studied. Results show that the non-equilibrium segregation of phosphorus occurred at the grain boundaries in the two steels while subjected to a tensile stress of 30MPa and held at 500°C. The corresponding critical time was about 1 hour for steel 2.25Cr1Mo and 3.5hour for steel 12Cr1MoV respectively. SEM photos of grain boundary fracture in Auger specimens of the test steels show that the grain boundary fracture rate increased with increasing concentration of phosphorus, and that the fracture toughness of steel 12Cr1MoV is much lower than the one of steel 2.25Cr1Mo.
Fracture Toughness and Cracking Behaviour of SCC Compared to VC
Authors: Korte Sara , Boel Veerle , de Corte Wouter , de Schutter Geert
Published: September 2013

Vibrated concrete (VC) and self-compacting concrete (SCC) have a substantially different composition, resulting in dissimilar mechanical properties regarding cracking behaviour. The critical value of the mode I stress-intensity factor KIC is an appropriate fracture parameter for evaluating fracture toughness and can be obtained from three-point bending tests (3PBT) on small, notched specimens. Subsequent determination of the energy release rate thus allows to examine the crack propagation and fracture process of both concrete types. This paper describes the results of such 3PBTs on samples, made from VC and SCC. Evaluation of the cracking behaviour, derived from these results, reveals remarkable differences.
Evolution of Shear Localization in an Elasto-Plastic Cosserat Material under Shearing
Authors: Ebrahimian Babak
Published: September 2013

Numerical investigations of shear localization evolution within a layer of granular material under large monotonic shearing are presented. Here, micro-polar (Cosserat) continuum approach is applied within the framework of elasto-plasticity to remove the numerical difficulties of localization modeling encountered in classical continuum. The micro-polar kinematical boundary conditions are used to model the rotation resistance of soil grains along the interface between granular layer and surface of adjoining structure. The finite element results show that shear localization takes place from the beginning of shearing and appears parallel to the direction of shearing, close to the boundary with less restriction of particle rotation. Furthermore, the state variables tend towards asymptotical stationary condition in large shear deformations.
Fatigue Behaviour of Thin Coated Al 7075 Alloy with Low Temperature PVD Coatings
Authors: Baragetti Sergio , Gerosa Riccardo , Villa Francesco
Published: September 2013

7075-T6 is one of the most performing aluminium alloys, considering its mechanical properties and good fatigue behaviour. In this work the influence of WC/C and DLC PVD coatings on the fatigue behaviour was investigated by rotating bending tests at 2·105 cycles. The fatigue behaviour of polished and untreated specimens was considered as reference. In order to decouple the effect of the deposition temperature from the coating one, some uncoated specimens were submitted to the thermal cycles of the WC/C and DLC processes and then tested under fatigue loading. Fatigue life was determined using a step-loading technique. SEM micrographs of the fracture surfaces were taken in order to characterize the fatigue mechanisms of coated and uncoated specimens.
Dislocation Clusters and Microcracks in Thin Films of LCF-Tested Austenitic Steel
Authors: Eterashvili Tamaz , Dzigrashvili T. , Vardosanidze M.
Published: September 2013

Austenitic chromium-nickel stainless steel CrNiNb 18-10 was studied using TEM technique. Characterizations of thin films prepared from bulk cylindrical samples after low-cycle fatigue (LCF) tests were conducted. Focus was made on the dislocation clusters, slip bands, defects and microstructure changes taking place in the steel during LCF. It is shown that microcracks occur in slip bands. Stereographic and trace analyses revealed the microcrack propagation directions. Two types of microcracks were observed: wedge-shaped and with parallel sides. The obtained results on possible reasons and mechanisms of microcrack formation in the above places are discussed in line with the theoretical assumptions and the existing literature.
Determination of Triaxial Tensile Failure Surfaces for Curing Epoxy Resins
Authors: Gross Todd , Kusch Jordan , Tsukrov Igor
Published: September 2013

Microcracking is often observed in the resin pockets of as-cured 3D woven composites with significant through-the-thickness fiber constraint. The resin is subjected to a triaxial tensile stress during cooling due to thermal expansion mismatch and shrinkage during curing. However, the temperature dependence of the failure surface for resins subjected to triaxial tensile stress is not known and there is no standard measurement method for applying a triaxial tensile stress. We have developed a novel method for measuring the triaxial tensile failure stress surface by confining the shrinkage of the resin to tubes of different thicknesses and made of materials with different thermal expansion coefficient. The difference in thermal contraction and shrinkage between the resin and the confining tube subjects the resin to a triaxial tensile stress during cooling and curing. We vary the stress-temperature state by selecting tubes with different coefficient of thermal expansion. We infer the stress in the resin from the deflections of the tube measured by a high resolution dilatometer assuming that the tube is a linear elastic, thick-walled pressure vessel.
Principle of Universality in Crack Incubation and Propagation
Authors: Aberšek Boris , Kralj Samo , Flašker Jože
Published: September 2013

The classical methods of solid mechanics assume that the homeomorphism of deformation sometimes does not provide an adequate description of the theological behaviour and fracture of real materials, while irreversible macro deformation and the fracture of solids are predetermined by material behaviour in nanoscale. When we talk about crack propagation, we must talk at least about four phenomena, namely about crack incubation, initiation, and crack propagation must be sleeted in two parts, to growth of short crack and to growth of linear elastic or long crack.
Simulation of Adhesion Performance of Mortar-Mortar Interface with Varied Fractographic Features
Authors: Satoh Ayumi , Yamada Kanji , Shinohara Yasuji
Published: September 2013

This paper aims at revealing the relationship between fractographic parameters of the mortar-mortar interface and the mechanical properties of such interface in terms of flexural strength and fracture energy. The FEM simulation was conducted where 8 cases of the combination of material properties were applied for all 7 interface models. The fractographic parameters evaluated on each interface model were six. Among them, both Sd (standard deviation of the height) and RL (ratio of the real length of the crack path to the projected length) are closely related to the mechanical properties.
Propagation Behavior of Naturally Initiated Small Crack in Austenitic Heat Resistant Steel under Thermo-Mechanical Fatigue Loading
Authors: Yamazaki Yasuhiro , Fujiki Wataru , Hara Yutaro
Published: September 2013

In this paper, the crack propagation behavior of naturally initiated small crack in in low-carbon/medium-nitrogen 316 stainless steel under thermo-mechanical fatigue loading was investigated. The experimental results indicated that the importance of the investigation of small crack propagation behavior because the information on the basis of physically long crack growth rate provides a dangerous evaluation on reliability to actual components. The small crack exhibits high growth rate under the In-phase TMF loading because of irreversible creep and plastic strains. However, the growth rates of small crack under the Out-of-phase TMF loading were lower because the effect of creep deformation became negligible in such condition.
Numerical Investigation on LEFM Limits under LSY Conditions
Authors: Caputo Francesco , Lamanna Giuseppe , Lanzillo L. , Soprano Alessandro
Published: September 2013

In this work, a parametric numerical investigation on the plastic zone size and shape at the crack front of a through crack in a plate is presented. The thickness of the plate, the size of the crack and the applied remote load values are considered as parameters. The obtained results allow assessing the limits of the linear elastic fracture mechanics in presence of an extensive material yielding at the crack front and the relationship between the plastic zone size and other parameters of the elastic-plastic fracture mechanics theory is highlighted.
A Synthesis of the Fatigue Behavior of Stainless Steel Bars under Fully Reversed Axial or Torsion Loading by Using the Specific Heat Loss
Authors: Meneghetti Giovanni , Ricotta Mauro , Negrisolo L. , Atzori Bruno
Published: September 2013

In previous papers, the energy dissipated to the surroundings as heat in a unit volume of material per cycle, Q, has been successfully applied to correlate experimental data generated from push-pull, stress- or strain-controlled fatigue tests on AISI 304 L stainless steel plain and notched specimens. In this paper the fatigue behaviour of AISI 304 L un-notched bars under fully-reversed axial or torsional loading was investigated. By using the Q parameter it was found that the experimental data collapse into the same energy-based scatter band previously determined with the push-pull tests. The results found in the present contribution are meant to be specific for the material investigated.
Selecting a Suitable Specimen Shape with Low Constraint Value for Determination of Fracture Parameters of Cementitious Composites
Authors: Seitl Stanislav , Korte Sara , de Corte Wouter , Boel Veerle , Sobek Jakub , Veselý Václav
Published: September 2013

The stress intensity factor and the T-stress describing the near-crack-tip fields for selected specimen shapes of a test geometry based on wedge splitting and three point bending tests with several variants of boundary conditions are computed using finite element software ANSYS. The test configuration in question is expected to be a convenient alternative to classical fracture tests (especially the tensile ones) for investigation of the quasi-brittle fracture of building materials, when low constraint is requested. These specimens are investigated within the framework of two-parameter fracture mechanics; near-crack-tip stress field parameters are determined and compared with those of the wedge splitting test due to their shape similarity. The sensitivity of the values of these parameters to the boundary conditions is also shown. Suitable choice of the shape of the specimens is discussed.
A Study on Impact Damage Analysis of Composite Propeller Blade of Turboprop Aircraft
Authors: Park Hyun Bum
Published: September 2013

Recently, the development need of environmental and fuel efficient aircrafts has been emphasized as an eco-friendly requirement in response to high oil prices. Accordingly, it is necessary to develop the next-generation eco-friendly and high fuel efficiency engine technology to enhance the fuel efficiency and aerodynamic performance of aircrafts for the purpose of reducing carbon dioxide emission amount prior to collecting and dealing with air pollution substances being discharged. In this study, development of the turboprop propeller blade for turboprop engine including aerodynamic and structural design and analysis was performed. The proposed propeller will be used as a candidate propeller for a regional aircraft which has been developed in Korea. Because the propeller for the target aircraft must endure the high bending and twisting moment loads during the flight operation, the high stiffness and strength carbon/epoxy composite material is used as a major structure materials. As a design procedure for the present study, firstly the structural design load is estimated through the aerodynamic load case analysis, and then flanges of spars from major bending loads and the skin from shear loads are initially sized using both the netting rule and the rule of mixture. In order to investigate the structure safety and stability, the structure analysis is carried out by finite element analysis using commercial code, MSC. NASTRAN. In addition, because the propeller should be safe against the bird strike, the bird strike phenomenon is analyzed using a commercial code, ANSYS.
The Cohesive Crack Model Applied to Notched PMMA Specimens Obeying a Non Linear Behaviour under Torsion Loading
Authors: Cendón David A. , Berto Filippo , Lazzarin Paolo , Elices Calafat Manuel
Published: September 2013

This article presents a new material model developed with the aim of analyzing failure of blunt notched components made of nonlinear brittle materials. The model, which combines the cohesive crack model with Hencky's theory of total deformations, is used to simulate an experimental benchmark carried out previously by the authors. Such combination is achieved through the embedded crack approach concept. In spite of the unavailability of precise material data, the numerical predictions obtained show good agreement with the experimental results.
Large Deformation and Failure of Thin-Walled Film at the Post-Buckling Delamination
Authors: Pavelko Vitalijs , Pavelko Igors , Smolyaninov Maxim
Published: September 2013

An accurate 1D model of post-buckling deformation of a thin sub-laminate of layered composite is develloped using nonlinead theory of slender plate. The strain energy realize rate at delamination propagation is obtained via the elliptical integrals. A model of fracture buckled sub-laminate is implemented and used for general analysis of progressive damage of composite
Stress Corrosion Cracking in Pipeline Steels
Authors: Plumtree Alan , Lambert Steve B.
Published: September 2013

Clusters of fine stress corrosion cracks on the external surface of buried steel natural gas pipelines in contact with groundwater have been examined and studied. The growth rates of transgranular stress corrosion cracks have been modeled and determined by conducting laboratory tests under similar conditions to those recorded in practice. The steel samples were immersed in an anaerobic dilute, near neutral solution with an open circuit potential for various times under stress. Metallographic examination of the resulting stress corrosion cracks was then conducted. Transgranular fracture, similar to that observed in the field, was observed following tests carried out under low frequency cycling in combination with a high stress ratio (R= minimum load/maximum load). A quantitative relationship between the frequency and stress ratio was developed giving crack growth rates similar to those observed in practice. Also, a superposition model was developed and applied to the experimental data which gave very good agreement between the actual and predicted crack growth rates. Applying the superposition model to the operating natural gas pipeline data showed that realistic predictions of crack growth result when taking interaction of the cracks into account.
The Danger of Self-Organizing Structures in Materials Subjected to Dynamical Non-Equilibrium Processes
Authors: Hutsaylyuk Volodymyr , Śnieżek Lucjan , Czausow Mykola , Berezin Valentin , Pylypenko Andriy
Published: September 2013

Researched the effect of DNP on mechanical properties of materials with a coarse-grained and fine-grained initial structure of aluminum alloy 2024 - T3, D16 and nano-crystallite titanium VT1-0. It has been shown that self-organization of structures at dynamic non-equilibrium processes is a critical parameter for materials with a nano-structures, since it significantly reduces the strength at the subsequent loading.
Failure of the Crude-Oil Tank Induced by Two Independent Corrosion Processes
Authors: Sís Jiří , Votava Bedřich
Published: September 2013

Corrosion processes are frequent reasons of failure of materials in many applications. Results of failure analysis of the crude-oil tank after more than 30 years of service are summarized in this work. The failure was caused by two different and independent corrosion processes – corrosion in crude oil inside the tank and corrosion from concrete base under the tank. Both corrosion processes usually occur equally over the whole surface. In this case, however, both the corrosion processes occurred with distinctly higher corrosion rate in basic material alongside of heat affected zone of weld joint as well. The crack with length about 420 mm was the final result of these processes. The effect of low-cycle fatigue from filling and draining of crude oil is usually significant and was discussed as well.
Numerical Analysis of the Damage in a Flanged Joint
Authors: Vergani Laura , Gobbi Giorgia , Colombo Chiara
Published: September 2013

Flanged joints arefundamental components of pipelines and they must be optimized to avoid leaks,bolts overstress and flanged joints damage. Overcoming standards indications asover-torqueing, and combination of different parameters, as difference in hardnessbetween flanges and gasket, can cause groove impressions. Aim of this study isto provide an efficient tool to optimize the choice of characteristicparameters of flanged joints, by numerical simulations. Geometries of a realtest case are simulated by FE models, considering different values of flangeand gasket hardness, as well as tightening torques, in order to cover possibleranges. From the analyses, it is possible to highlight that a particularcombination of hardness difference and over-torque is responsible for permanentflange impression.
Numerical Simulation on Failure Process of Rubber-Sleeved Headed Stud Shear Connector
Authors: Xu Xiao Qing , Liu Yu Qing , He Jun , Luo Jie
Published: September 2013

Rubber-sleeved headed stud shear connector is flexible shear connector used in steel-concrete composite structures. In this work, nonlinear finite element model has been developed to simulate the failure process of the shear connector under shear loading. The stress distribution, deformation, crack propagation and failure mode were analyzed. The material nonlinearities of rubber, headed stud, concrete were considered in the material model. The rubber was assumed as a perfect material with no defect, and a modified reduced polynomial form of strain energy including an energy limiter and a new constant was introduced into the user material subroutine VUANISOHYPER-INV of ABAQUS software. Damaged plasticity model was used to model the concrete material. A tri-linear elastic-plastic curve was used in stud material model. Comparing the results obtained from the finite element analysis with those from push-out test, good agreement is highlighted in the capacity, ductility and failure mode of rubber-sleeved headed stud shear connector.
Research of Performance about Ceramic Coating on Aluminum Bumper to Resist Hypervelocity Impact
Authors: Guan Gong Shun , Bi Qiang , Zhang Yu
Published: September 2013

Shield structure based on ceramic coating on aluminum bumper was designed, and a series of hypervelocity impact tests were practiced with a two-stage light gas gun facility. Impact velocities were varied between1.5km/s and 5.0km/s. The diameter of projectiles were 3.97mm and 6.35mm respectively. The impact angle was 0°. The damage of the ceramic coating on aluminum bumper under hypervelocity impact was studied. It was found that the ceramic coating on aluminum bumper could help enhancing the protection performance of shield to resist hypervelocity impact. The results indicated when the ceramic coating is on the front side of aluminum bumper, it was good for comminuting projectile and weakening the kinetic energy of projectile. For a certain aluminum bumper, existing a critical thickness of ceramic coating in which capability of Whipple shield to resist hypervelocity impact is the best. On this basis, the proposal of the optimum design for ceramic coating on aluminum bumper was made.
Closed Crack Detection with Nonlinear Instantaneous Baseline
Authors: Wu Wei Liang , Qu Wen Zhong , Xiao Li
Published: September 2013

Closed cracks, which stay in contact unless the excitation exceeds a certain threshold, exist as great menace to structures. Since nonlinear response is more sensitive to micro damage than conventional linear approaches, analyzing the nonlinear part of the collected response of structures to an input ultrasonic excitation is more promising in damage detection. In this paper, in order to image the location of a closed crack, an instantaneous baseline measurement is adopted and the nonlinear response is extracted by using scaling subtraction method. A three-dimensional finite element model of a plate with a closed crack is developed and the behavior of the closed crack is simulated with nonlinear springs at the crack interfaces. A network of actuators and sensors which constitutes of two arrays of surface-bonded piezoelectric transducers is built. The instantaneous baselines of each path are collected when the model is excited with low amplitude excitation. To diagnose the closed crack, a higher amplitude excitation over the threshold is applied to the model and the response signals of each path are recorded. The result shows that the differences caused by the crack can be observed from the scaling subtraction of these two recorded responses and the location of closed crack can be accurately imaged.
Corrosion and Wear Behavior of CAE Deposited CrN-PVD Coatings
Authors: Montesano Lorenzo , Petrogalli C. , Pola A. , Gelfi Marcello , Sisti V. , La Vecchia G.M.
Published: September 2013

Corrosion and wear resistance of Cathodic Arc Evaporation (CAE) CrN coatings deposited on a tool steel were investigated considering the effect of the number of layers (mono or double) and the influence of defects. The CrN coatings were characterized for mechanical (scratch, nanoindentation test), corrosion behavior (polarizarion tests) and tribological properties (pin-on-disk tests). Scanning Electron Microscope analyses on samples before and after the tests were also made in order to identify the type of the defects and the role they play in the coating damage. Monolayer coating shows a good wear behavior with a stable and low friction coefficient, but its corrosion performance is poor. On the contrary, the presence of an interface into the double layer improves the corrosion resistance, but it is a weak point for the coating delamination during wear tests.
Analysis of Thermal Residual Stresses Distribution in Circular and Elliptical Bonded Composite Repair of Metallic Cracked Structures
Authors: Albedah A. , Mhamdia Rachid , Benyahia F. , Bachir Bouiadjra B. , Serier B.
Published: September 2013

In this study, the distribution of the thermal residual stresses due to the adhesive curing in elliptical and circular bonded composite repairs is analyzed using the finite element method. The computation of these stresses comprises all components of the structures: cracked plate, composite patch and adhesive layer. In addition, the influence of these residual stresses on the repair performance is highlighted by analyzing their effect on the stress intensity factor at the crack tip. The obtained results show that the normal thermal stresses in the plate and the patch are significant.. The presence of the thermal stresses increases the stress intensity factor at the crack tip which reduce the repair efficiency.