bluuebunny/crossref_metadata_2025 huggingface dataset:
Crack Growth Modeling in a Specimen with Polymer Weld
Authors: Ševčík Martin , Hutař Pavel , Náhlík Luboš , Lach Ralf , Knésl Zdeněk , Grellman Wolfgang
Published: September 2011

Secure and cost effective joining methods are key points for practical applications of plastic pipelines. The morphology and material structure of welded joints are complicated in comparison with the base pipe material. The formation of the weld is highly dependent on both thermal history and stress state. Consequently, the material parameters characterizing the weld joint and corresponding heated zone influence the reliability and safety of the welded pipe system as a whole. In the contribution a welded polymer-polymer butt joint is considered and its possible damage caused by slow crack growing in the weld zone is numerically analyzed. The numerical model takes into account the geometry of the bead and changes in material properties inside the weld zone. The results obtained from welded specimens are compared with those for a smooth specimen from the base material. The conclusions described in the paper can be used for a better transfer of fracture mechanics characteristics between laboratory specimens and real pipes.
Fracture Analysis of a First Stage Turbine Blade by FRANC3D
Authors: Asadikouhanjani Saeed , Ghorbani Reza
Published: September 2011

The premature failure of a blade occurred after a service life of 8127 EOH operation houre. This paper presents the fracture analysis of the first stage blade through fractographic and mechanical analysis. Crack growth mechanisms were evaluated based on the microscopic observations of the fracture surfaces by SEM. The analysis of the different region of the fracture surface shows that crack propagation is mainly related with fatigue mechanism. The crack propagation occurred in the pressure-suction side direction. The dynamic characteristics of the blade were evaluated by FEM in order to identify the cause of blade failure. The result depicts that the second mode of vibration might be excited and the vibratory stresses cause to HCF damage of the blade. Eventully fracture analysis of the blade under the presence of a fatigue crack was analyzed by FRACNC3D software.
Finite Element Analysis by Using Hyper-Elastic Properties for Rubber Component
Authors: Woo Chang Su , Park Hyun Sung , Shin Wae Gi
Published: September 2011

The material modeling of hyper-elastic properties in rubber is generally characterized by the strain energy function. The strain energy functions have been represented either in term of the strain in variants that are functions of the stretch ratios, or directly in terms of the principal stretch. Successful modeling and design of rubber components relies on both the selection of an appropriate strain energy function and an accurate determination of material constants in the function. Material constants in the strain energy functions can be determined from the curve fitting of experimental stress-strain data. The uniaxial tension, equi-biaxial tension and pure shear test were performed to acquire the constants of the strain energy functions which were Mooney-Rivlin and Ogden model. Nonlinear finite element analysis was executed to evaluate the behavior of deformation and strain distribute by using the commercial finite element code. Also, the fatigue tests were carried out to obtain the fatigue failure. Fatigue failure was initiated at the critical location was observed during the fatigue test of rubber component, which was the same result predicted by the finite element analysis.
Assessment of Thermal Damage for Railway Wheel of Long-Term Running
Authors: Kwon Seok Jin , Seo Jung Won , Lee Dong Hyung , Kwon Sung Tae
Published: September 2011

The railway wheel in long-term running had experienced the wheel damage due to fatigue crack and shelling. The damaged wheel in railway vehicle would cause a poor ride comfort, a rise in the maintenance cost and even fracture of the wheel, which then leads to a tremendous social and economical cost. It is necessary to evaluate long-term damage of railway wheel in order to ensure the safety of wheel. To evaluate the damage for railway wheels, the measurements for the replication of wheel surface and residual stress of railway wheel using x-ray diffraction system were carried out. The result shows that the residual stress of wheel is depend on the running distance and thermal gradient during brake application also that the replication test can be applied in new evaluation method of wheel damage.
Dynamic Antiplane Behavior for a Quarter Infinite Piezoelectric Medium with a Subsurface Circular Inclusion
Authors: Song Tian Shu , Li Dong , Merhej Tammam
Published: September 2011

Dynamic antiplane behaviors are investigated theoretically in this paper for a quarter infinite piezoelectric medium with a subsurface circular inclusion. Based on complex variable and mirror image method, the expressions are obtained on dynamic stress concentration factor (DSCF) and electric field intensity concentration factor (EFICF) at the inclusion’s edge caused by the interaction between the inclusion and the right angle edge under time-harmonic anti-plane shearing. While some calculating cases are plotted, so as to show how the frequencies of incident wave, the piezoelectric material’s parameters and the structure’s geometry influence on DSCF and EFICF. The calculating results indicate that dynamic analyses are important to a quarter-infinite piezoelectric medium with defects at the surface vicinity.
Study on Welding Deformations of Shipboard of Container Vessel
Authors: Li Hong , Qiu Da Lu , Li Guang Lei , Ren Hui Long
Published: September 2011

Residual plastic strains of the shipboard are the product of nonlinear behaviors during welding. Deformations of a welded shipboard injure the beauty of appearance of the ship, cause errors during the assembly of the shipboard and reduce the strength of the ship. Residual welding deformations of shipboard of a container vessel are studied in this paper. Nonlinear three dimensional transient temperature fields are analyzed by FEM first. The heat source is modeled as a moving heat flux following a Gaussian distribution. Then, applying the equivalent loads induced by the inherent strain on the shipboard, the final in-plane shrinkage and out-of-plane deformations are calculated. Being compared with the experimental results of deformations, the simulated results show mostly conformity.
Effect of REM Finishing on Fatigue Behavior of a Shot Peened Low Alloy Steel
Authors: Bagherifard Sara , Ghelichi Ramin , Guagliano Mario , Bandini M.
Published: September 2011

The effect of slight surface REM finishing, that is a chemically accelerated polishing process, in order to reduce surface roughness after shot peening has been studied on different series of specimens shot peened by varied peening parameters. Room temperature rotating bending fatigue tests have been performed on the shot peened series and the series subjected to shot peening and successive REM finishing process. The results represent how REM finishing affects the final fatigue behavior of differently treated specimens in two ways: decreasing surface roughness and removing a thin layer of material with compressive residual stresses.
Micromechanical Modeling of Heterogeneous Materials with Irregularly Shaped Pores
Authors: Tsukrov Igor , Drach Borys
Published: September 2011

An approach to predict the overall mechanical properties of materials containing pores of irregular shapes is described. Micromechanical modeling is performed by evaluating cavity compliance contribution tensors of individual pores [1] which are then used as an input for well-developed homogenization models. The cavity compliance contribution tensor can be found either analytically or numerically depending on the pore geometry and the level of anisotropy of the surrounding material. The results of numerical analysis can be used to compare the ability of differently shaped pores to initiate fracture.
Edge-Strengthening of Structural Glass with Protective Coatings
Authors: Lindqvist Maria , Louter Christian , Lebet Jean Paul
Published: September 2011

In modern buildings, glass is increasingly used as a load-carrying material in structural components, such as glass beams. For glass beams especially the edge strength of glass is important. However, the strength of glass is not a material constant but depends on various parameters, which makes glass, amongst other things, a challenging building material. One of the parameters influencing glass strength is the combination of humidity and stress, which may cause stress corrosion. The aim of the current study is to limit the effect of humidity at the glass edge. This is done by the application of a protective coating. In this exploratory study several coating solutions are tested applying the coating at the edge of glass specimens. These specimens are then subjected to in-plane four-point bending tests to determine their failure strength. The effects of the coatings on the edge strength are analyzed using the failure strength data from the bending tests. The results indicate that only one of the tested coatings has an effect on the glass edge strength.
Experimental Study on Polymer Mass Used to Repair Damaged Structures
Authors: Falborski Tomasz , Jankowski Robert , Kwiecień Arkadiusz
Published: September 2011

A new method of repairing damaged structures by injecting the cracks with specially designed polymer mass (flexible two-component grout based on polyurethane resin) has been recently proposed. The technique is mainly dedicated to damaged masonries, especially historical structures where minimum intervention is permitted. The cracks are filled with the special injection, forming the flexible joints bonding the disrupted structural elements. The aim of the present paper is to show the results of the experimental study focused on properties of the polymer mass used for the injections. First, the material has been subjected to static compression tests. Then, the polymer mass has been examined dynamically under harmonic excitations with different frequencies and strain levels. The results of the study indicate that the tested polymer mass shows highly non-linear behaviour with relatively low resistance under small displacements and stiffening effect for higher strain levels. Moreover, it is substantially dependent on the strain rate having higher initial deformation modulus for higher strain rate values. Finally, the observed hysteretic behaviour of the material confirms its potential to dissipate the energy during vibrations preventing from further structural damage in the case of dynamic loading.
Inelastic Dynamic Analysis and Non-Linear Static Analysis (Push-Over) of 3-Story and 6-Story RC Buildings of Ductile Frames
Authors: Avila Jorge A. , Manzano Julio C.
Published: September 2011

With 3-story and 6-story RC buildings of ductile frames, previously designed, non-linear static analysis with increased monotonically lateral loads (Push-over) are made in order to determine its collapse and their responses against the inelastic seismic analysis results with the SCT-EW-85 record are compared. It is designed with the Principal Body and with the Appendix A conditions of the Seismic Technical Norms of the Mexico City Code (RDF-04), satisfying the maximum story distortion limits of the service and collapse conditions; the buildings (offices) are in the IIIb compressible seismic zone. The non-lineal responses were determined with nominal resistance and over-resistance effects. For the non-linear static analysis with increased monotonically lateral loads, was important to select the type of lateral forces distribution. The comparison were made with base shear force–roof lateral displacement relations.
Simulation of a Strategy for the Assessment of Damage in Human Bones by Using FEM and Signal Processing
Authors: Miniaci Marco , Marzani Alessandro , Viola Erasmo
Published: September 2011

The aim of this work is to propose a non-invasive technique aimed at assessing the evolution of damage in elongated bones that could be caused, for instance, by metabolic diseases. The technique exploits signals related to mechanical guided waves traveling along the bone to characterize its mechanical properties in a total non-destructive manner. Such properties can be used as an indicator of the damage level present in the bone. The preliminary results motivate future studies
Crack Propagation from Bi-Material Notches – Matched Asymptotic Procedure
Authors: Klusák Jan , Profant Tomáš , Ševeček Oldřich , Kotoul Michal
Published: September 2011

The methods based on the properties of the two-state integrals allow one to calculate the amplitude of singular and the other terms of the Williams’ asymptotic expansion. The paper is focused on the use of the Y-integral, whose application is conditioned by the knowledge of the so-called auxiliary solution of the solved problem. On the other hand, the Y-integral can be applied to the analysis of the problems with various geometries, e.g. the analysis of the bi-material notches. The application of the Y-integral can be also extended to the matched asymptotic procedure, which allows one to predict the behavior of the cracked notches or following crack growth near the bi-material interfaces.
Slow Crack Growth by Grain Boundary Dissolution of Hydroxyapatite in Water
Authors: Seo Dong Seok , Hwang Kyu Hong , Lee Jong Kook
Published: September 2011

Mechanical degradation of hydroxyapatite ceramics due to the slow crack growth was observed in water. Microstructural crack on the surface of hydroxyapatite initiated by grain boundary dissolution in liquid environment resulting in particle loosening and microstructural-level degradation, followed by a drastic decrease of mechanical properties. In this study, slow crack growth by the dissolution behavior of hydroxyapatite ceramics was investigated based on microstructural observation by field emission microscopy. The crack growth and morphological change of hydroxyapatite surface, especially at the initial stage of dissolution and related surface roughness were observed with immersion time. The surface dissolution occurred from the initial stage of immersion showing increase in surface roughness. Following certain period of immersion time, the surface dissolution initiated at grain boundaries and generated many separated grains.
Fatigue Fracture Mechanism of Extruded Al Alloy 7075-T6 in High Humidity
Authors: Kariya K. , Kawagoishi Norio , Maeda H. , Chen Q. , Goto Masahiro , Nu Yan
Published: September 2011

Effect of high humidity on growth mechanism of a fatigue crack was investigated for an extruded bar of an age-hardened Al alloy 7075-T6 which had the marked texture of plane (111). Fracture in high humidity occurred by the growth of a shear mode crack under high stress levels, though a crack propagated in a tensile mode under low stress ones, macroscopically. Many voids and slip planes were observed on the fracture surface yielded by the shear mode crack. Especially most of the fracture surface was occupied by voids where the crack was small. The void percentage decreased with increasing in the crack depth. Fracture surface yielded by the shear mode crack was a plane (100). The growth direction of the shear mode crack to the cross section of specimen was about 55° corresponding to the angle composed by this plane and the texture of plane (111). These results suggest that the shear mode crack was related to microstructure, stress and environment. The growth mechanism of the shear mode crack assisted by hydrogen was proposed based on the results of the acceleration of crack growth and the formation of voids in high humidity.
Validation of Modified Lemaitre’s Anisotropic Damage Model with the Cross Die Drawing Test
Authors: Niazi M.S. , Wisselink H. H. , Meinders T.
Published: September 2011

Dual Phase (DP) steels are widely replacing the traditional forming steels in automotive industry. Advanced damage models are required to accurately predict the formability of DP steels. In this work, Lemaitre’s anisotropic damage model has been slightly modified for sheet metal forming applications and for strain rate dependent materials. The damage evolution law is adapted to take into account the strain rate dependency and negative triaxialities. The damage parameters for pre-production DP600 steel were determined. The modified damage models (isotropic and anisotropic) were validated using the cross die drawing test. The anisotropic damage model predicts the crack direction more accurately.
Defect Size Measurement of Wall Thinned Pipe Using Shearography and Digital Image Correlation
Authors: Kim Kyeong Suk , Park Chan Sik , Hong Dong Pyo , Choi Man Yong , Chang Ho Seob , Jung Hyun Chul
Published: September 2011

Defect size of wall thinned pipe is measured by using Speckle Shearing Interferometry (SSI) and Digital Image Correlation (DIC) techniques. A wall thinned defect of a carbon steel pipe was typically caused by flow accelerated corrosion (FAC). As wall thinned pipe can cause a huge accident at the nuclear power plant (NPP), a wall thinned defect should be detected for structure safety. SSI is one of the optical nondestructive techniques and can provide to inspect in real-time and to measure on the whole visible area at a time. DIC is a kind of the visual testing method. This method which uses a stereo vision system can measure the deformation or strain/stress of a structure in 3D. In this paper, ASTM A106 Gr.B carbon steel pipe is used as specimen. When the pressure load is provided by the pressure pump, the out-of-plane deformation along the longitudinal direction of a pipe can be detected quantitatively. Both results of SSI and DIC experiments are compared.
Developed Random Tessellation for Modeling of Microstructure
Authors: Farhangdoost Khalil , Rahnama S.
Published: September 2011

The concept of random tessellation is extensively used in wide area of natural sciences, especially material sciences. In this paper a simple but complete explanation of the random tessellation and mathematical tools requirements is presented. Then introducing the algorithm and the program for display random tessellation diagram was written. This program, with high speed and simple algorithm for random tessellation has the ability to change the level of statistical parameters such as number, mean, variance of the area of the grain. The ability to model microstructures of metals and grains for mechanical application, such as estimation of mechanical properties and crack propagation model in microstructure scale is very important. Finally, the microstructure produced by this program show good fitness of random generation with real microstructure.
Numerical Investigation into Dynamic Fracture of PCBN
Authors: Carolan Declan , Ivanković Alojz , Murphy Neal
Published: September 2011

Polycrystalline Cubic Boron Nitride (PCBN) is a super-hard material, which is used in some of the most demanding material removal operations today. PCBN cutting tools are employed in turning of hardened steels as well as machining of other abrasive and aerospace grade alloys. In these applications the tools are subjected to high operating temperatures, abrasive and impact loading. Impact loading can lead to the sudden fracture and hence failure of the tool. Much of the recent developments in this industry have been focused on improving the fracture toughness of the PCBN compact. In this work a hypothesis based on induced thermal stresses at the crack tip has been put forward to explain the observed rate sensitivity of PCBN. The results show that the fracture toughness of PCBN is closely linked to the CBN grain size and that the rate sensitivity can be explained in part by induced thermal stresses at the crack tip at high rates of loading.
A Methodological Approach to the Tolerance Problems during the Assembly Process of Deformable Bodies
Authors: Caputo Francesco , Lamanna Giuseppe , Pannullo F. M. , De Angelis G.
Published: September 2011

The variations in shape compared to the initial project affect the performance and the appearance of any mechanical assembly. There are many commercial software that allow to conduct an analysis of tolerances but most of these are based on the assumption that the elements analyzed are rigid. This assumption is not found in many industrial processes. This is the typical case of the automotive industry, which widely uses assemblies of sheet metal elements, which are flexible. The major concern is how much variation (the output) of the assembly will be, as “staked-up” from possible sources of variation (the input). The sources of variation in the assembly process include parts variation, tooling variation, and their interactions. For clarity, only part variation is considered as the input in this paper. The present work aims to perform analyses of tolerances in presence of flexible elements; the analyses involve the finite element method.
Effects of Tolerances on the Structural Behavior of a Bolted Hybrid Joint
Authors: Caputo Francesco , Lamanna Giuseppe , Soprano Alessandro
Published: September 2011

In this work, results from a study on bolted joints made of unidirectional, quasi isotropic Carbon Fiber Reinforced Polymer (CFRP) composites, subjected to tensile loads, are reported. CFRP composite materials are widely used in the mechanical industry, such as that of aerospace, where requirements of weight reduction and structural high performances are very compelling. Composite materials generally present a high resistance to fatigue and corrosion; however, the presence of joints produces the major problems and a poor design of joints leads to a drastic reduction of the reliability of structures made of these materials. A hybrid bolted joint involving a metal plate, made of aluminum alloy, and a CFRP composite plate has been considered; the plates are held together by a titanium bolt. Experimental results from literature are compared with those obtained through a numerical analysis developed with Abaqus code. Once the CFRP composite has been analyzed and the numerical model validated through numerical-experimental correlations, other possible configurations have been numerically analyzed in order to ensure the highest strength of the examined hybrid joint. Afterwards the effects of bolt-hole clearance on the stiffness and strength of the same joint have been investigated.
Spatial Statistical Analyses for Time-Dependent Corroded Surfaces of Uncoated Weathering Steel Plates in Various Corrosive Environments
Authors: Kainuma Shigenobu , Jeong Young Soo
Published: September 2011

To ensure the safety of steel structures, it is important to evaluate the time-dependent corrosion behavior. The purpose of this research is to develop a method of predicting time-dependence of the corrosion surfaces of uncoated weathering steel plates in various corrosive environments. Atmospheric exposure tests were carried out on the uncoated steel plates for 0.5, 1, 2 and 4-years in Okinawa Island, Japan. Spatial statistical analyses were carried out on the corrosion surfaces of the tested specimens. In addition to this, the time-dependence of the corrosion surfaces were simulated by the spatial statistical technique.
Simulation of Rubber-Coated Fabric Material Damage
Authors: Derewonko Agnieszka , Baranowski Pawel , Rudnik Dariusz
Published: September 2011

The objective of this work is to describe part of the selecting process of a rubber-coated fabric material model. The material is used to construct an air cushion that is a carrying element of the cassette pontoon bridge unit. During operation the air cushion is permanently in contact with a metal component, fresh water and air. Therefore various interactions, such as a contact problem, flow of medium and thermodynamics can occur. The basic material model for numerical simulation was selected based on the uniaxial tensile test. The simple method was used to describe time-dependent material properties for numerical analysis, which allows computation to take a reasonable time. In order to assess the usefulness of the selected material model the impact puncture test was modelled with the same conditions and properties as in the laboratory testing machine called Instron. Moreover, an attempt of simulating the damage process is described. The energy absorbed by the material was registered during the laboratory test which was compared with the results of numerical analysis. An acceptable compatibility of the results is noticed.
Finite Element Analysis of Secondary Cracks at a Crack Front under Pure Mode III Loading
Authors: Ressel Matthias , Theilig Holger
Published: September 2011

Several hypotheses and concepts exist for the prediction of crack deflection angles from the analysis of the undisturbed stress distribution at the crack front. In this paper, a finite element analysis of small penny shaped secondary cracks with deflection angles ψ0 = π/4 at a pure mode III loaded crack front is presented. The results are compared with the solutions of the well-known 3D fracture criteria. The fracture mechanical analysis is performed by the highly effective MVCCI-method.
Analysis of the Influence of Microstructure Heterogeneity and Mechanical Properties of Welded Joint Constituents on Fracture Toughness for Plane Strain, KIc
Authors: Čamagić Ivica , Vasić Nemanja , Burzić Zijah , Sedmak Aleksandar
Published: September 2011

The problem of fracture toughness, KIc, determination at a crack tip localized in a welded joint is placed in principle because fracture mechanics assumes homogenous material, not only around the crack tip but on a distance from it, in order to maintain valid theoretical assumptions and importance of the fracture toughness as the property measured by some of the fracture mechanics methods. Welded joint, as an integral part of a structure, represents inhomogeneity by microstructure and mechanical properties, often by geometrical form, and by the stress field as well, which are affected by various factors as well as residual stresses after welding [1]. However, these general difficulties did not disenable experimental determination of the fracture toughness under plane strain, KIc, in certain critical areas of a welded joint, or welded joint as a whole, but rather there are difficulties in interpreting the meaning of the measured values. Specimens for the fracture mechanics parameters determination are specimens with cracks, and cracks appears in welded joints as the most critical defects.
R-Curve and Size Effect in Quasibrittle Fracture: A Rewriting of the Bazant’s Size Effect Law
Authors: Morel S. , Dourado N.
Published: September 2011

The recent rewriting of the Bazant's Size Effect Law which has suggested the existence of an additional asymptotic regime for intermediate structure sizes is compared to numerical simulations of fracture of geometrically similar notched structures of different sizes. The quasibrittle failure is simulated through Cohesive Zone Model (bilinear softening) using a constant set of cohesive parameters whatever the specimen size. The different asymptotic regimes expected for the size effect on the nominal strength are shown in fair agreement with the size effect observed on the results obtained from numerical simulations. The existence of the new asymptotic regime expected for intermediate structure sizes is, in particular, clearly revealed by this comparison.
Failure Mechanisms and Energy Absorption in Composite Elements under Axial Crush
Authors: Johnson Alastair F. , David Matthew
Published: September 2011

Test methods are presented to determine failure modes and energy absorption properties of composite crash structural elements from quasi-static tests on chamfered carbon fabric/epoxy tube segment specimens under axial compression loads. High speed film and CT scans of failed specimens are used to identify trigger mechanisms, failure mode evolution at the crush front and failure processes during steady crushing. FE models of failure were developed which could be the basis for materials selection and design procedures for crashworthy composite structures. These are based on meso-scale composites ply damage models combined with cohesive interfaces to represent delamination failures, which damage and fail when the interface fracture energy is reached. The models are implemented in an explicit FE code and parameters for the ply damage and delamination models were obtained from related materials test programmes. The FE models were applied to simulate axial crushing in tube segments and C-channels, showing good predictions of measured peak forces at failure initiation, steady crush forces and total energy absorption.
Influence of the Wall Thickness on the Allowable and Failure Pressures of Two- and Tree-Way Globe Valve Bodies
Authors: Opalić Milan , Galić Ivica , Vučković Krešimir
Published: September 2011

A globe valve is a linear motion valve used to shut off and regulate fluid flow in pipelines. Depending on the number of process connections, they are produced as two‑ or three-way valves. The main valve component carrying the internal pressure is the valve body. For safe exploitation, the valves are designed with the allowable internal pressure taken into consideration. The aim of this paper is to investigate the influence of the wall thickness on the allowable and failure pressures of two- and tree-way globe valve bodies, DN50 and DN100 respectively. Twice-elastic-slope (TES) and the tangent‑intersection (TI) methods are used to obtain the plastic collapse pressures at the critical location which was determined (Fig. 1a and 1b) at the location where maximum equivalent plastic strain throughout the valve body thickness reaches the outer surface. Obtained values are used afterwards to calculate corresponding allowable pressures according to the limit design method, while the failure pressure at the same location was determined as the highest point from the load-maximal principal strain curve. Calculated allowable pressure values, for both valve bodies, are compared with the corresponding ones obtained using the EN standard.
Fatigue Life Prediction Investigation on Steel Honeycomb Sandwich Beams at High-Temperature
Authors: Lu Jie , Zou Guang Ping , Cao Yang
Published: September 2011

The aim of this work is to investigate the fatigue behaviors of the steel honeycomb sandwich beams at 400°C through three point bending experiments. A stiffness reduction approach was adopted which was further based on the interpolation by the empirical functions of experimental results. For load control fatigue experiments, the evolution relations between number of cycles and displacement were obtained through real-time deformation monitoring of the specimens. A method based on exponential function fit was adopted in the further analysis, whose coefficients depended on the material properties, loading levels and high temperature conditions. This approach allowed us to predict the high temperature fatigue life of specimens while avoiding a large number of experiments. The results showed that experimental and prediction results were in a good agreement.
Sensitivity Analysis for the Stiffened Plate Structure System with Crack Defects
Authors: An Wei Guang , An Hai , Song Xiang Hua
Published: September 2011

The influence of crack defects on the ultimate strength of stiffened plate is analyzed, and reliability calculation and sensitivity analysis expressions of stiffened plate elements are given in this paper. An approach to sensitivity analysis for the global reliability index are proposed for the structure system which consists of stiffened plate elements with crack defects, providing the base for analyzing the contribution of design variables to the system reliability and seeking conveniently weak elements which reduce the reliability index of structure system. Finally, the validity of the approach is verified by taking a numerical example of a cabin section of the ship structure. The approach proposed in this paper provides an applicable reference for the safe design and maintenance of structure system.
Failure Conditions from Push Out Tests of a Steel-Concrete Joint: Fracture Mechanics Approach
Authors: Klusák Jan , Seitl Stanislav , de Corte Wouter , Helincks Peter , Boel Veerle , de Schutter Geert
Published: September 2011

In order to evaluate the shear bond strength of a steel-concrete joint using an epoxy adhesive interlayer, push-out tests were carried out. The test samples consisted of two sandblasted steel plates and a self-compacting concrete sample, with the epoxy layer applied on the steel plates and gritted with granulates. During testing, an external force was applied to the concrete core and continuously recorded. To investigate the failure mechanism in detail, a fracture mechanics approach is required. In this paper theoretical-numerical assessment of the push-out test is performed. Regarding the finite element calculations, the locations suitable for failure initiation match bi-material (steel-concrete) notches. The most dangerous locations are evaluated from a generalized linear elastic fracture mechanics point of view. The critical load corresponding to the conditions of failure initiation is estimated and compared with the experimental results.
Overview of the Methods for Service Life Prediction on Gears
Authors: Aberšek Boris , Flašker Jože
Published: September 2011

For designing machines and devices the dimensioning with respect to service life is increasingly taken into account. This applies also for gearing which are still today one of very important components of almost all machines. The problem of determination of the service life of gearing is directly related to geometry of gears, multiaxial loadings, materials and appropriate models for prediction of the crack propagation. Obviously gears and gearing belong to the real complex structure, by correctly selected and carefully planned experiments we obtained results with which we can confirm and justified the mathematical model for calculating different parameters, i.e. service life.
Taking Full Advantage of Nominal Stresses to Design Notched Components against Variable Amplitude Multiaxial Fatigue
Authors: Susmel Luca , Taylor David
Published: September 2011

The present paper is concerned with the use of the Modified Wöhler Curve Method (MWCM), applied in terms of nominal stresses, to estimate lifetime of notched components subjected to variable amplitude multiaxial fatigue loading. The MWCM is applied by defining the critical plane through that direction experiencing the maximum variance of the resolved shear stress: since the shear stress resolved along the above direction is a monodimensional quantity, fatigue cycles are directly counted by the classical Rain-Flow method. The performed validation exercise, based on an extensive experimental investigation, seems to strongly support the idea that the MWCM applied along with the classical nominal stress based approach is capable of accurately estimating fatigue damage also in notched components subjected to variable amplitude multiaxial load histories.
Failure Analysis of Bolted Composite Joint Based on Extended Finite Element
Authors: Wang Zhen Qing , Zhou Song , Zhou Jian Sheng , Wu Xiao Di
Published: September 2011

In this paper, the influence of geometrical parameters on failure load of bolted single-lap composite joint was investigated. The composite laminate was manufactured from HTA/6376, a high-strength carbon fiber–epoxy material currently used in primary structures in the European aircraft industry. Two geometrical parameters which were plate width-to-hole diameter ratio (W/D), and the edge-to-hole diameter ratio (E/D) were analyzed. To avoid modeling each ply of the laminates discretely, the laminates were modeled using equivalent linear elastic properties. the failure analysis was modeled by Extend Finite Element Method (XFEM) in ABAQUS. Maximum principal stress criterion (Maxps) was used to determine the failure load.
Structural Integrity of CO2 Transport Pipelines – A Review
Authors: Chahardehi Amir
Published: September 2011

A recent trend in the development of CO2 pipelines is the shift from the predominance of transport of CO2 for enhanced oil recovery (EOR) to the transportation of CO2 as part of the carbon capture and storage (CSS) process for global warming mitigation. Among the processes of capture, transport, and storage, less attention has been paid to transport as it is assumed to be for granted, existing technology. This paper presents a focused analysis of the problem of structural integrity of CO2 pipelines through reviewing the state-of-the-art literature and practice, and highlights the need for a unified code of practice for the modelling of integrity and, due to the potentially hazardous nature of CO2, safety, in these pipelines.
Numerical Model of Bevel Gears Cutting by Duplex Helical Method
Authors: Pisula Jadwiga , Płocica Mieczysław
Published: September 2011

In the paper it was presented a mathematical model of tooth generating of spiral bevel pinion and gear. Geometry as well as kinematic functions of the 116 machine tool were defined and mathematical model of the technological gear was built, which allows for the simulation of tooth generating.
The Method of Finite Differences in Solutions Concerning Circular Plate
Authors: Sabiniak Henryk G.
Published: September 2011

Finite difference method in solving classic problems in theory of plates is considered a standard one [1], [2], [3], [4]. The above refers mainly to solutions in right-angle coordinates. For circular plates, for which the use of polar coordinates is the best option, the question of classic plate deflection gets complicated. In accordance with mathematical rules the passage from partial differentials to final differences seems firm. Still final formulas both for the equation (1), as well as for border conditions of circular plate obtained in this study and in the study [3] differ considerably. The paper describes in detail necessary mathematical calculations. The final results are presented in identical form as in the study [3]. Difference of results as well as the length of arm in passage from partial differentials to finite differences for mixed derivatives are discussed. Generalizations resulting from these discussions are presented. This preliminary proceeding has the purpose of searching for solutions to technical problems in machine building and construction, in particular finding a solution to the question of distribution of load along contact line in worm gearing.
The Numerical Methods in Geometric Construction Mapping
Authors: Sabiniak Henryk G. , Cichowicz Robert
Published: September 2011

A dynamic development of numerical methods enables even so complicated geometrical modelling as modelling of hypoidal teeth, and in particular of worm teeth. Building on the basis of the finite element method of this type of geometrical mathematical model enables observing and analysing physical phenomena taking place in the teeth, e.g. changes of pressure distribution along the contact lines depending on the phase of meshing for particular cooperating pairs of teeth. Due to limited technical possibilities and mathematical apparatus such analyses were carried out only on the basis of the theory of plates with constant thickness. An unquestionable advantage of such numerical modelling is a short time needed to obtain final results, which enables profound analysis of the transmitted load. The knowledge of course of pressure distribution along the contact lines of particular pairs of intermeshing teeth in worm gears already in the design phase enables taking into consideration in adequate correction or even modification of the working surface of teeth, with the aim to equalise the distribution of pressure.
Compensation of Pressure Peaks in PWK-Type Hydraulic Pumps
Authors: Osiecki Leszek , Patrosz Piotr , Zawistowski Tomasz , Landvogt Bettina , Piechna Janusz , Żyliński Bartek
Published: September 2011

Hydraulic axial pumps equipped with cam-driven commutation unit (PWK pumps) proved their high efficiency up to 55 MPa and ability to work self-sucking, even at high speed. Displacement of PWK pump may easily be changed by moving its control cam. Full discharge from hydrostatic forces makes such control possible by direct action of a low-energy actuator like proportional electromagnet or stepping motor. That eliminates heavy and costly hydraulic servomechanism, necessary in other variable displacement machines. Such a control mechanism was positively evaluated in prototype tests in Department of Hydraulics and Pneumatics of Gdańsk University of Technology. The new commutation unit generates however harmful pressure peaks. The paper presents the compensation method for pressure peaks by use of the elastic compensation chamber. It shows also results of multidisciplinary FEA and CFD analysis necessary to properly design the compensation chamber.
Designing of High-Speed Machine Shafts of Carbon Composites with Highly Nonlinear Characteristics
Authors: Dąbrowski Zbigniew , Deuszkiewicz Piotr
Published: September 2011

Carbon composites (carbon-aramide) constitute modern “Hi-Tech” materials of an extremely favourable ratio of load to mass transfer. Thereby the idea of using them for long transmission shafts seems to be very attractive, specially in aviation and sailing. Unfortunately structures made of carbon-aramide composites are characterised by a strong anisotropy and in effect by non-linearity of elastic characteristics, due to which they have significantly different dynamic influences than steel structures. To this end there is a need of application of different calculation algorithms than the ones widely used in Construction Engineering. It requires taking into account the coupling between transverse and torsional vibrations, which essentially projects onto the possibility of the critical states occurrence. This is indispensable since shafts made of expensive composite materials are profitable in places where their low elementary mass is essential (long high-speed transmission systems). The paper presents the theoretical discussion of this problem, empirical investigations of nonlinear characteristics as well as the proposition of designing methods.
Numerical and Experimental Study on Seam Welding Behavior in Extrusion of Micro-Channel Tube
Authors: Tang Ding , Zhang Qing Qing , Li Da Yong , Peng Ying Hong
Published: September 2011

Micro-channel tube with submillimeter-diameter channels is a kind of newly developed heat transfer tube based on theory of micro-scale heat transfer. As the micro-channel tube has multiple welding points and work under high pressure condition, welding strength is one of the key problems for the extrusion process. This paper presented a new method in evaluation of the seam welding strength formed in the extrusion process. Firstly, FE simulation is carried out for the status of the billet in the welding chamber during the extrusion process. Then, thermo mechanical experiment is done for the relationship between the welding strength and three key factors. Combining the relationship with the numerical results, welding strength of the micro-channel tube can be evaluated. Pressure bearing test shows that the evolution method is reliable. The study is helpful for the optimization the extrusion process and improvement of the seam weld quality.
Preparation of Si-C-N-O Amorphous Films from a Polysilazane by Heat Treatment at High-Temperatures
Authors: Hou Guang Lei , Peng Zhi Jian , Fu Zhi Qiang , Yue Wen , Wang Cheng Biao
Published: September 2011

Si-C-N-O amorphous films were fabricated at about 800°C by pyrolysis of poly- vinylsilazane precursor films in a vacuum oven under N2 flow. The polymer precursor films were prepared onto Si wafers by spinning from a solution of the polymer. The compositions of the as-prepared films were confirmed by X-ray diffraction, Fourier transformation infrared spectroscopy, and x-ray photoelectron spectroscopy. SEM analysis indicated that the films can be formed with thickness more than several micrometers, and very smooth surfaces. Such films will be promising in application of protecting equipments in high-temperature, corrosive and wear environments.
Representation Methods for Microwave Absorption Ceramics
Authors: Zeng Zhao Yang , Liu Heng , Lu Ming
Published: September 2011

Two methods are widely used to represent the microwave absorption properties of ceramics: measuring the values of electromagnetic parameters such as permeability and permittivity, or directly measuring the reflection rate of a metal-backed slab sample made of this material. However, do these two methods coincide with each other? If not, which method should be used as right way to represent this kind of ceramics? To answer these questions, both methods are carried out on the same ceramics, of which the results are compared. Distinct difference between these measured results is found, and the possible reasons for the difference are also discussed.
Electrical Characteristics and Microstructures of Dy2O3-Doped Bi4Ti3O12 Thin Films
Authors: Chen Min , Mei X.A. , Cai A.H. , Liu J. , Huang Chong Qing
Published: September 2011

Dy2O3-doped bismuth titanate (Bi4-xDyxTi3O12: BDT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the structures and ferroelectric properties of the films were investigated. XRD studies indicated that all of BDT films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. The remanent polarization (Pr) and coercive field (Ec) of the BDT Film with x = 0.8 were 20 μC/cm2and 60 KV/cm, respectively. After 3 × 1010switching cycles, 20% degradation of Pris observed in the film.
Influence of Multiple Firing on the Bending Strength of Zirconia/Porcelain Bilayered Dental Ceramics
Authors: Lu Rong Jian , Ma Ting Ting , Yi Yuan Fu , Shao Long Quan , Tian Jie Mo , Hou Kang Lin , Wen Ning , Deng Bin
Published: September 2011

Bilayered three-point bending strength specimen of KAVO zirconia-Vita VM9 veneering porcelain were made according to ISO6872 standard, the core to porcelain thickness ratio was 1:1. Specimens were subjected to multiple dentine porcelain firing cycles. Three-point bending strength were tested, SEM was used to observe the characteristics of the failure mode. Results show that there was no influence on the bending strength by multiple firing, the three-point bending strength were 996 ~ 1020 MPa after multiple firing, and no obvious defects was found at the interfaces. In all bilayered specimen, the bulk fracture initiated at the tensile surface of the core material and was consistently accompanied with porcelain crush and delamination at the interface.
Synthesis of ZnO/MWCNT Heterostructure via the Self-Assemble Route and its Property
Authors: Zhang Na , Zhang Cheng , Xu Hai Fang , Li Yu Lin , Li Qiang
Published: September 2011

Multi-walled carbon nanotubes (MWCNT) attached on ZnO quantum dots named ZnO/MWCNT composites were synthesized by a multi-steps wet chemical self-assembling technique. The morphology of ZnO/MWCNT was also studied in details. The as-prepared ZnO and ZnO/ MWCNT composites had been characterized by XRD, SEM and TEM. It was found that the co-existence of MWCNTs and ZnO in ZnO/MWCNT sample. Monodispersed ZnO nanoparticles and the MWNTs/ZnO conjunction structure can be vividly observed from TEM image. TEM image also indicated that the decoration of MWCNTs did not cause any damage to the tubular shape and the conjunction occurred at the outershell of MWCNTs. Moreover, to assess the optoelectronic properties, photoluminescence (PL) spectra were also compared between monodispersed ZnO QDs and the ZnO /MWCNT composites. The relationship between PL spectra and structure was discussed. It was shown that the particular PL behavior of ZnO in the ZnO/MWCNT had been quenched, which meant the electron transformation between the ZnO and MWCNT had happened.