bluuebunny/crossref_metadata_2025 huggingface dataset:
Detecção de Staphylococcus spp. Meticilina Resistente em Centro Cirúrgico de Grandes Animais
Authors: Bazílio Lucas Emanuel Pereira , Bordin Jéssica Tainá , Granemann Myrian Carla , Sfaciotte Ricardo Antonio Pilegi , Vignoto Vanessa Kelly Capoia , Osaka Sílvia Cristina , Munhoz Patrícia Marques , Wosiacki Sheila Rezler
Published: October 2016

O objetivo deste estudo foi identificar Staphylococcus spp. Resistente à Meticilina (MRS) em um Centro Cirúrgico de Grandes Animais. Foram coletadas 24 amostras deste local, em pontos estratégicos, antes e após limpeza e desinfecção. A detecção de MRS foi realizada pela técnica de disco-difusão com discos de penicilina, oxacilina e cefoxitina. Os resultados das coletas feitas no ambiente sem desinfecção mostram a presença de Staphylococcus spp. em 58,3% das amostras, sendo 85,7% destas MRS. Dentre as seis amostras oxacilina-resistentes, todas foram resistentes a penicilina e duas foram resistentes a cefoxitina. Na coleta após a desinfecção foram identificados estafilococos em 33,33% das amostras, sendo dois MRS. Com este estudo pode-se concluir que a presença de MRS é uma realidade na Medicina Veterinária Hospitalar, semelhante ao ocorrido em Hospitais Humanos. Trata-se de um patógeno de fácil transmissão, devendo-se tomar medidas profiláticas, como limpeza de mãos e utensílios médicos para evitar sua disseminação, além do uso correto da antibioticoterapia.
INSUFICIÊNCIA RENAL E CISTITE ASSOCIADOS À RABDOMIÓLISE EM UM EQUINO – RELATO DE CASO
Authors: Camargo Mauro Henrique Bueno , Ferreira Heloisa , Dias Lucas Lopes Rino , Ribeiro Max Gimenes
Published: October 2016

O objetivo desse trabalho foi relatar o caso de um equino, da raça Quarto de Milha, de seis anos de idade, apresentando sinais clínicos de dor indicativo de afeções do sistema urinário, sendo essas a insuficiência renal crônica e cistite, associadas ao histórico do animal de Rabdomiólise. Foram realizados exames para avaliação do perfil bioquímico renal e urinálise do paciente e implantado tratamento no Hospital Veterinário.
The Role of Prior Fabrication and in Service Thermal Ageing on the Creep Life of AISI Type 316 Stainless Steel Components
Authors: Martinez-Ubeda Ana Isabel , Warren Xander , Griffiths Ian , Flewitt Peter E.J.
Published: October 2016

A significant factor that influences the creep life of AISI Type 316H austenitic stainless steel components such as headers, and tubes is the initial microstructure. These components typically have a comparable specified composition but different thermo-mechanical fabrication histories. The variations in composition within the nominal range result in initial microstructures which become increasingly divergent during ageing. In this paper we explore effect of these contributions on the long term service aged microstructure and discuss the resulting impact on the overall creep life of these components. The microstructure of specific regions has been characterised with a range of techniques, including high resolution transmission electron microscopy imaging and chemical analyses undertaken using a JEOL ARM instrument operating at 200 KeV fitted with an energy dispersive spectrometer. This provides a unique identification of the service aged precipitates and the distribution of alloying and impurity elements. The results are discussed with respect to the initiation of creep cavities and the associated creep damage accumulation in the context of lifetime assessment of these AISI Type 316H austenitic stainless steel boiler components.
Determination of the Impact Location and Damage Characterization Based on Guided Waves
Authors: de Luca A. , Sharif Khodaei Zahra , Caputo Francesco
Published: October 2016

The aim of this paper is to understand the effects of the damage criteria modelling on the training phase (performed by means of Finite Element simulations) of an artificial neural network (ANN) enabled to locate impacts onto a CFRP laminate. The developed FE models have been also used to investigate the intra-laminar damage mode, which, among different ones, has the most effects on the residual strength of the panel.
Development and Numerical Implementation of an Anisotropic Continuum Damage Model for Concrete
Authors: Hartikainen Juha , Kolari Kari , Kouhia Reijo
Published: October 2016

In this paper, a thermodynamic formulation for modelling anisotropic damage of elastic-brittle materials based on Ottosen's 4-parameter failure surface is proposed. The model is developed by using proper expressions for Gibb's free energy and the complementary form of the dissipation potential. The formulation predicts the basic characteristic behaviour of concrete well and results ina realistic shape for the damage surface.
Determination of Initial Stages of Fatigue on the Basis of Fatigue Tensile and Fatigue Bend Testing
Authors: Gubeljak Nenad , Cvetić M.
Published: October 2016

Fatigue crack initiation usually starts from defects or inclusion (s) in the material in the zone of stress concentration. The stress concentration zone can be at the surface of the specimen or inside the material. The fatigue crack starts to propagate, depending on stress amplitude, if the range of the stress intensity factor is higher than the fatigue threshold. The aim of this paper is to present the procedure for determining the fatigue crack initial stage by using the Wöhler S-N curve and the fatigue crack propagation parameters obtained by experiment for the loading range R=-1. Determination of the fatigue initial stage has been determined by the analysis of tensile smooth specimens and notched bending specimens. Results show that linear elastic fracture mechanics is applicable in order to establish a model for fatigue crack propagation.
Increasing Fracture Toughness for 3D Multiscale Carbon Nanotube and Carbon Fiber Reinforced Composites
Authors: Deng Yan , Tong Li Yong
Published: October 2016

This paper presents a new concept of forming 3D hierarchical carbon nanotube (CNT) and carbon fiber (CF) reinforced composites by using a low temperature grafting method that connects CNTs to CF surface by covalent bonding. By using amorphous carbon to join the free ends of two cantilever CNTs, it is shown via in situ scanning electron microscope (SEM) pulling out experiments that the strengths at the joint between CF-CNT and CNT-CNT junction are high and breakage occurs in CNT itself. This offers evidence that the maximum load in a typical bridging load-displacement curve could be increased, which in turn can potentially increase intralaminar and interlaminar fracture toughness of 3D multiscale CNT-CF reinforced composites.
Incorporation of a Fracture Criterion in Ideal Flow Design
Authors: Lyamina Elena , Alexandrov Sergei
Published: October 2016

The theory of sheet and bulk ideal plastic flows is used for the preliminary design of metal forming processes. The present paper develops an approach to incorporate the Cockroft and Latham ductile fracture criterion in this design method for stationary bulk flows. In particular, it is demonstrated that the initiation of ductile fracture can be predicted without having the ideal flow solution for stress and strain in the plastic zone (it is only necessary to know that the solution exists). Using the approach proposed the initiation of ductile fracture in axisymmetric drawing is predicted.
Relationship between Grain Growth and Formation of Fracture Surface of Ultrafine Grained Cu in High-Cycle Fatigue
Authors: Goto Masahiro , Han S.Z. , Yamamoto Takaei , Kitamura Junichi , Kusno Kamil , Fujimura T. , Yakushiji T.
Published: October 2016

Fatigue tests were conducted on specimens of ultrafine grained copper produced by equal channel angular pressing. The growth behavior of a fatal crack was monitored successively. The morphological features of the crack growth paths and fracture surfaces were influenced by variation of grain size and damaged areas of the crack tip, depending on the stage of progress of the fatigue damage. The change in fracture surface was discussed by considering the interrelation between the reversible plastic zone size at the crack tip and the microstructure evolved during cyclic stressing.
Effect of Side Grooves on Plane Stress Fracture Behavior of Compact Tension Specimens Made of Ultra-High Strength Steel
Authors: Dabiri M. , Skriko T. , Amraei M. , Björk T.
Published: October 2016

Thin compact tension specimens made of direct quenched ultra-high strength steel were tested under constant rate uniaxial tensile load. The length of the crack was monitored using optical microscopes on both sides of the specimens during the fatigue pre-cracking (using a chevron V-notch). Deformations during the crack lengthening were recorded by a full-field measurement technique using a set of digital cameras to check the effect of side grooves on reduction of surface deformation. The Specimen without side grooves showed a high level of plasticity, thickness reduction, and crack growth along a deviating path. In addition, the fracture surface showed excessive failure along the inclined plane. The presence of side grooves, however, led to the decrease of the maximum applied force at final fracture while the force prior to crack tearing was almost the same as the specimen without side grooves. Grooves significantly reduced the inclination of the fracture plane and plastic deformation due to removal of low stress triaxiality on the surface. They led to the fracture along a straight path and approximately even surface which makes them beneficial especially when compliance method is used in plane stress fracture tests.
The Effectiveness of Polymer Damper in Damage Reduction of Temporary Steel Grandstand
Authors: Lasowicz Natalia , Jankowski Robert
Published: October 2016

A large number of accidents involving damage of temporary grandstands during different types of events were observed in the past. The aim of the paper is to analyse numerically the effectiveness of a polymer damper in damage reduction of a temporary steel scaffolding grandstand exposed to dynamic load due to jumping. The element has been installed as a diagonal one at the back part of the structure. The method has been compared with the typical solution of strengthening the grandstand with the diagonal stiffener of tubular cross section. The results of the study clearly show that the response of a temporary steel grandstand equipped with a diagonal damper as well as with the diagonal stiffener is substantially different. The application of the polymer damper leads to considerable reduction in the level of measured accelerations due to the increased structural damping preventing from damage.
Practical Method for Estimating Time-Dependent Corrosion Depth of Uncoated Carbon Steel Plates under Various Atmospheric Environmental Conditions Using Fe/Ag Galvanic Couple Corrosion Sensor
Authors: Kainuma Shigenobu , Yamamoto Yuya , Jeong Young Soo
Published: October 2016

In this research, an evaluation method for the time-dependent corrosion depth of uncoated structural steel plates using an Fe/Ag galvanic couple atmospheric corrosion monitoring (ACM)-type sensor was proposed. This method was focused on environments with and without effects of rainfall and airborne sea salt. Atmospheric exposure tests were carried out on the uncoated carbon steel plates in four sites in which the environments varied widely as a function of rainfall and airborne sea salt. In addition to this, the corrosive environments of the skyward-and groundward-facing surfaces of the plates were monitored using the ACM sensors.
Optimal Sensor Positioning for Damage Detection in Composite Sensorised Panels
Authors: Sainfort Laure , Sharif Khodaei Zahra , Aliabadi M.H.
Published: October 2016

In this work the optimal configuration of transducers for damage detection and localization has been investigated. A particular interest is given to three optimization methods: mini-max, average Probability of Non Detection (POND) and ray tracing approach, coupled with genetic algorithm. After optimal configurations have been computed for each technique, they are experimentally tested and compared on a composite panel with one or two damages by generating and receiving Lamb waves signals. Damage detection is carried out with the Probability Based Damage Index Method (PBDIM). It was found that, in most cases, the ray tracing method and the average POND technique give better results, with a good detection of damages in comparison to the minimax POND technique, even if the latter seems numerically better.
An Unexpected Feature of a Class of Damage Evolution Models
Authors: Alexandrov Sergei
Published: October 2016

The main objective of the present paper is to demonstrate, by means of a boundary value problem permitting a closed-form solution, that no solution exists under certain conditions in the case of a rigid/plastic material model including a damage evolution equation. The source of this feature of the solution is the sticking friction condition, which is often adopted in the metal forming literature.
Passive Sensing of Sensorized Composite Panels: Support Vector Machine
Authors: Yue Nan , Sharif Khodaei Zahra , Aliabadi M.H.
Published: October 2016

Strain readings recorded by surface mounted piezoelectric sensors due to impact events on composite panel are used to detect and characterize the impact. Sensor signals on a composite stiffened panels have been simulated by a valid numerical model. Applicability of least square support vector machines (LSSVM) on creating a meta-model to detect and characterize impact event has been investigated. In particular, the main advantage of LSSVM over other meta-modeling technique was found to be the smaller number of training data that is required. Experimental results on a composite panel has been used to validate the findings.
Determining Cyclic Durability of Piezoceramic Structures Using Probabilistic-Structural Approach
Authors: Babich Dmytro , Dorodnykh Tatiana
Published: October 2016

The present paper addresses the new probabilistic-structural approach to determining the service life of piezoceramic structural members under multiple static or cyclic loading. The cyclical service life of structures is related to the intensity with which a microcrack density increases with the cycles of loading. To illustrate the approach the problem of durability of piezoelectric transformer plate for idle mode is considered. Two estimation methods of the durability of this type transformer are proposed.
Mathematical Modelling of a Seismic Isolation System to Protect Structures during Damaging Earthquakes
Authors: Falborski Tomasz , Sołtysik Barbara , Jankowski Robert
Published: October 2016

The present study aims to determine the effectiveness of a nonlinear mathematical model in simulating complex mechanical behaviour of a seismic isolation system to protect structures during strong and damaging earthquakes. In order to construct the Polymeric Bearings considered in this research, a specially prepared flexible polyurethane elastomer with increased damping properties has been used. The usefulness of the proposed mathematical model has been verified by comparing the dynamic response of a base-isolated single-storey structure model under various seismic excitations with the results obtained from the detailed numerical analyses where the previously examined experimental model has been considered as a multi-degree-of-freedom system. The results obtained from the numerical investigation using lumped-mass models have confirmed that the proposed nonlinear mathematical model can be successfully used to simulate the complex mechanical behaviour of the Polymeric Bearings in numerical analyses.
Revisiting the Problem of Debond Initiation at Fibre-Matrix Interface under Transversal Biaxial Loads - A Comparison of Several Non-Classical Fracture Mechanics Approaches
Authors: Távara L. , García I.G. , Vodička Roman , Panagiotopoulos C.G. , Mantič Vladislav
Published: October 2016

Understanding matrix failure in LFRP composites is one of the main challenges when developing failure criteria for these materials. This work aims to study the influence of the secondary transverse load on the crack initiation at micro-scale. Four non-classical approaches of fracture mechanics are used to model the onset of fibre-matrix interface debonds: Linear Elastic Brittle Interface Model (LEBIM), an Energetic Approach for the Linear Elastic Brittle Interface Model (EA-LEBIM), an Energetic Approach for the bilinear Cohesive Zone Model (EA-CZM) and the Coupled Criterion of the Finite Fracture Mechanics (CC-FFM). Results obtained by these approaches predict that, for brittle fibre-matrix configurations, a secondary transverse compression reduces the critical value of the main transverse tension leading to the debond onset. This fact is not taken into account by the currently used failure criteria
Effect of Plastic Deformation on Compliance Curve Based Crack Closure Measurement
Authors: Mohin M.A. , Xu Y.G. , Lewis A. , Chrysanthou A.
Published: October 2016

Fatigue crack growth depends heavily on near tip stress-strain behavior controlled by many micromechanical and microstructural factors. Crack closure is widely used to rationalize crack growth behaviour under complex loading conditions. Reliable crack closure measurement is essential for enhanced damage tolerance design and remains a challenge to the industry. This paper focuses on the effect of plastic deformation ahead of a notch/crack on the non-linearity of compliance curves of 6082-T651 aluminium alloy specimens to highlight a potential issue in the conventional compliance curve based crack closure measurement technique. Experimental and numerical simulation results demonstrate that plastic deformation ahead of the notch will introduce non-linear stress-strain behavior in the absence of crack closure. It is proposed that the effect of crack tip plasticity on the non-linearity of the compliance curve be separated to obtain reliable crack closure measurement.
Server-Side Screening and Network Visualization of Huge Simulation Results
Authors: Yamada Tomonori , Yodo Kaworu , Wada Yoshitaka , Yoshimura Shinobu
Published: October 2016

With the growth of computing technologies including both hardware and simulation algorithms, simulation models have become extremely large in scale. Nowadays the visualization of the huge result data obtained by the large scale simulation is one of the main bottlenecks through all the simulation procedures because such large scale simulation is generally conducted on computing servers such as supercomputers, while the visualization is done on local client environments. To avoid time consuming transfer of the result data from the computing server to the local client, we propose techniques for the server-side screening and network visualization of them in advance to their transfer. We demonstrate that our approach contributes to find out the region of interests in whole the result data by a numerical example.
Investigation on Damage-Involved Structural Response of Colliding Steel Structures during Ground Motions
Authors: Sołtysik Barbara , Falborski Tomasz , Jankowski Robert
Published: October 2016

Earthquakes are the most unpredictable damaging loads which can affect civil engineering structures. Due to insufficient separation distance between adjacent structures with different dynamic properties, structural collisions may occur during ground motions. Although the research on structural pounding has recently been much advanced, the studies have mainly been conducted for concrete structures. The aim of this paper is to show the results of experimental investigation, focused on dynamic behaviour of closely-separated three models of steel structures which have been subjected to damaging earthquake excitations. The study was performed using three models of steel towers with different dynamic parameters and various distances between the structures. The acceleration time histories of the Kobe and the Northridge earthquakes were applied as the seismic excitation. The unidirectional shaking table, located at the Gdansk University of Technology (Poland), was used in the experimental study. The results have confirmed that collisions may lead to the increase in the structural response, although they may also play a positive role, depending on the size of the separation gap between the structures.
High-Temperature Structural Analysis of a Lab-Scale Alloy 800HT PCHE
Authors: Song Kee Nam , Kim Eung Seon , Jang S.Y.
Published: October 2016

The IHX (Intermediate Heat Exchanger) of a VHTR (Very High Temperature Reactor) transfers 950°C heat generated from the VHTR to a hydrogen production plant. The Korea Atomic Energy Research Institute has manufactured a lab-scale Alloy 800HT PCHE (Printed Circuit Heat Exchanger) prototype under consideration as a candidate of the IHX (Intermediate Heat Exchanger). In this study, as a part of a structural integrity evaluation of the PCHE prototype, an elasto-plastic structural analysis including a thermal analysis was carried out under the designed test conditions of the PCHE prototype in a helium experimental loop (HELP). The analysis results were reflected to re-design the pipeline layout of HELP and to determine the actual test conditions of the PCHE prototype in the re-designed HELP in view of experimental safety.
Thermal Stress in Volcanic-Ash-Deposited Thermal Barrier Coatings Monitored by Long-Range Laser System
Authors: Arai Masayuki , Yamaura Daichi
Published: October 2016

All thermal power plants including gas turbine (GT) of Tokyo electric company are located along Tokyo bay. If Mt. Fuji is exploded, volcanic ash is fallen down in Kanto area. If volcanic ash is inhaled into GTs, the ash would be firstly impacted and deposited onto thermal barrier coating (TBC) of the blades. Such deposition of the volcanic ash causes the delamination of the ceramic coating. In this study, TBC delamination mechanisms due to the volcanic ash deposition is discussed based upon thermal stress evaluated by a laser monitoring measurement system.
Studies on Mode II Rock Crack Propagation on Different Loading Environments
Authors: Cheng C. , Li M.X. , Liu Y. , Zhang X. , Cheng Y.Y. , Ling X.T.
Published: October 2016

In this paper, a new type of specimen, which can be easily made by rock core through geological exploration, of mode II rock crack has been designed and processed. The crack propagation forces F of the specimen are measured under different temperatures and different confining pressures. The crack extension patterns are observed. The 3D finite element model of the specimen is established. The stresses near crack tip are calculated to get the value of KIIC when the crack initiation. The variation of KIIC of the model II rock crack is obtained under different temperatures and confining pressures. The experiments and numerical results show that temperature and confining pressure have obviously influence on KIIC, the value of KIIC decreases with the temperature increasing, and increases with the confining pressure increasing. The results of the paper can provide an important reference for analyzing the stability of the rock cracks in underground engineering.
Fretting Wear Simulation in Fiber-Reinforced Composite Materials
Authors: Rodríguez-Tembleque Luis , Aliabadi M.H.
Published: October 2016

This work presents a numerical formulation to compute wear in ber-reinforced composite materials that are subjected to fretting wear contact conditions. The formulation is based on authors' previous works [1, 2] and presents contact and wear constitutive laws which consider micromechanical aspects such as the ber orientation relative to the sliding direction, the ber volume fraction or the ber length. The formulation uses the Boundary Element Method (BEM) for computing the elastic in uence coef cients and contact operators over the augmented Lagrangian to enforce contact constraints. The proposed formulation is applied to compute and study wear in different carbon berreinforced bulk and fi lm con gurations.
Design of a Hybrid Lightweight Energy Absorber
Authors: de Luca A. , Lamanna Giuseppe , Sepe Raffaele , Soprano Alessandro
Published: October 2016

Among several problems which might affect the passenger safety during an accidental crash event, the deceleration pulse is one of the most critical. For this reason vehicles are designed to convert the Kinetic Energy occurring in an impact in plastic deformation and to spread the loads due to such events through designed structural load paths. An important role in the kinetic energy absorbing at high velocities is played by the energy absorbers. The energy absorption capability of a crashworthy element or system is largely affected by material properties and structural design. This work deals with a numerical investigation on the energy absorbing capability of a new concept of energy absorber made out of the combination of metal parts and carbon composite materials. A numerical investigation on the parameters which increase the crash performance as well as decrease the weight of such device has been presented in this paper.
Flow Estimation in a Steel Pipe Using Guided Waves
Authors: Quiroga John , Quiroga Jabid , Mujica Luis , Villamizar Rodolfo , Ruiz Magda
Published: October 2016

In this investigation, a flow rate estimation guided wave based scheme in pipes is proposed. The effect of the fluid over the propagation of longitudinal waves has been experimentally studied by using several laminar flows of water transported by a steel pipe. Results have shown a decrease of the guided wave pattern repeatability and the signal energy as the flow rate increase as a result of the energy leakage from the pipe to the fluid. A Matlab® script is used to excite the PZT actuator via picoscope 2208 of Picotech®, the captured signal is acquired also by the picoscope and the data is processed in Matlab. The test bench utilized is composed by a 1” sch 40 A-106 pipe, a needle valve and a centrifugal pump provides the flow energy. A couple of PZTs are used in a picth-catch configuration to produce and capture the longitudinal waves along the cross section of the pipe
Numerical Investigation of the Stringer Termination Debonding in Composite Stiffened Panels
Authors: Sellitto Andrea , Della Corte S. , Riccio Aniello
Published: October 2016

The purpose of this work is the numerical investigation of the stringer termination debonding in composite stiffened panels, subjected to a traction load. A parametric analysis has been carried out, considering the influence of the plies’ number and of the stringer width on the delamination initiation load as well as on the skin-stringer complete separation load.
Basic Research on Simulation for 3D Crack Growth by Mesh Free BFM
Authors: Sonobe Yohei , Koyama Atsuhiro , Saimoto Akihide
Published: October 2016

A new methodology that enables us to compute the arbitrary shaped 3D crack problems is studied. In the present method, it is possible to analyze the 3D crack problems without preparing mesh data as in ordinary boundary elements but with defining a sequence of nodal points representing the crack front and the internal nodal points that define a crack surface as well as a shape function used for determining unknown variables. The present method has special potential for analyzing a complicated 3D crack geometry which is generally difficult to treat in usual element based methods. In the present research, we apply mesh-free body force method to analyze the growth of 3D planar cracks. In concrete, a crack growth analysis for initially rectangular or elliptical crack existing in an infinite solid under uniform tensile stress perpendicular to the crack surface at infinity is demonstrated
Experimental-Numerical Assessment of Critical SIF from VHCF Tests
Authors: Hasani Najafabadi S.H. , Paolino D.S. , Tridello A. , Chiandussi G. , Rossetto Massimo
Published: October 2016

The continuous enhancement of reliability and durability requirements for many machinery components is significantly pushing the experimental research on the Very-High-Cycle Fatigue (VHCF) response of metallic materials. In order to significantly reduce testing time, ultrasonic testing machines are widely adopted when carrying out VHCF tests.
Several fundamental material properties can be estimated from the fracture surfaces of specimens failed during ultrasonic VHCF tests. In the VHCF literature the critical Stress Intensity Factor (SIF) is generally estimated by applying analytical SIF formulations to the typical semi-circular surface crack geometry revealed by fracture surfaces at final failure. However, when subjected to ultrasonic VHCF tests, analytical SIF formulations valid for static loading conditions could eventually lead to significant estimation errors.
The present paper aims at comparing the critical SIF at failure estimated from conventional analytical formulations and from Finite Element Models (FEMs). The fracture surfaces of two specimens with different shapes (Hourglass and Gaussian) are taken into account for modeling crack geometry at final failure. Through an implicit solving procedure, the critical SIF in resonance condition at 20 kHz is computed from the 3D geometry of the cracked specimens and compared with the corresponding analytical prediction.
Determination of Fracture Mechanical Properties of Carbon Bonded Alumina Using Miniaturized Specimens
Authors: Zielke H. , Abendroth Martin , Kuna Meinhard
Published: October 2016

Open cell ceramic foam filters are utilized to reduce non-metallic inclusions during casting of metals and therefore to enhance the quality of cast parts. A new generation of multifunctional filters made of carbon bonded alumina (Al2O3-C) has been developed within the scope of the collaborative research center CRC 920 [1]. The assessment of the resistance against high thermal and mechanical loads requires a mechanical characterization of the ceramic filter material. The mechanical properties show a distinctive size dependency, that’s why the specimen dimensions should be similar to the strut size of the real filter structures.
The tensile fracture behavior is investigated by means of the Small Punch Test (SPT) using miniaturized disk-shaped specimens. During the mechanical tests a load-displacement curve is measured until failure occurs and a fracture stress is calculated from the experimental results. An estimation about the failure probability by means of Weibull statistics is performed because of the large scatter of the strength of the material. Furthermore, a modified version of the SPT, the so called Ball On Three Balls Test (B3B), is applied and compared to the SPT. In a final step numerical simulations of the B3B tests are performed by means of the finite element method to identify fracture mechanical material parameters like the fracture toughness.
Old Suspended Timber Floors Flexurally-Strengthened with Different Structural Materials
Authors: Biscaia Hugo , Franco Noel , Nunes Ricardo , Chastre Carlos
Published: October 2016

The design of timber beams has strict limits when it comes to the Serviceability Limit States (SLS) either in short-term or in long-term deflections. In order to face this aspect efficiently, the increase of the cross section of the beams might be considered as a solution. However, the prohibitive increase of the costs associated to this solution or the change of the initial architecture design of the building, opens the opportunity to find new and more efficient solutions. In that way, the use of additional reinforcements to the timber beams may be seen as a promising solution because either new or old structures would keep always their original aesthetical aspect with no significant self-weight increase and improving their behaviour to short and long-term actions. Therefore, the current study is dedicated to the analysis of composite timber beams where Fiber Reinforcement Polymers (FRP), steel or stainless steel are used to improve the stiffness, strength and deflection behaviour of old suspended timber floors. An experimental program was conducted where old suspended timber floors reinforced with CFRP strips were subjected to 4-point bending tests. A simplify nonlinear numerical model was developed to simulate the bending behaviour of the specimens and several other cases with other reinforcement configurations and different structural materials were assumed. The numerical analysis herein presented also takes into account both Ultimate and Serviceability Limit States of the reinforced specimens.
Evaluation of Fatigue Strength of Different Thickness Laser Welded S355 Steel Sheets Considering Microstructure, Surface Conditions and Residual Stresses
Authors: Černý Ivo , Sís Jiří
Published: October 2016

The paper contains results of experimental programme aimed at evaluation of fatigue resistance of laser welded 6 mm and 10 mm thick sheets of a low alloy structural S355 steel. High cycle fatigue tests were performed to verify fatigue strength of the sheets containing laser welds performed with optimised laser welding parameters. Surface of the sheets was in as-received conditions simulating real welding applications. The results are compared to each other and to fatigue S-N curve of the S355 material evaluated on quite small standard specimens. Endurance limit of the 10 mm thick laser welded sheet was by more than by 30% higher than that of the 6 mm thick sheet. In connection with this effect, all fatigue cracks in the 6 mm thick sheets initiated in the weld area unlike the 10 mm sheet, where cracks initiated both in the weld area and outside it indicating no or just minor unfavourable effect of the welding. However, fatigue strength and endurance limit of small material specimens were considerably higher even in comparison with the 10 mm welded sheets. The results are discussed considering, results of microstructure analyses, different values and distribution of residual stresses and also differences between surface conditions of the sheets and the standard specimens.
Analytical-Numerical Determination of Stress Distribution around a Tip of Polygon-Like Inclusion
Authors: Krepl Ondřej , Klusák Jan , Profant Tomáš
Published: October 2016

A stress distribution in vicinity of a tip of polygon-like inclusion exhibits a singular stress behaviour. Singular stresses at the tip can be a reason for a crack initiation in composite materials. Knowledge of stress field is necessary condition for reliable assessment of such composites.
A stress field near the general singular stress concentrator can be analytically described by means of Muskhelishvili plane elasticity based on complex variable functions. Parameters necessary for the description are the exponents of singularity and Generalized Stress Intensity Factors (GSIFs). The stress field in the closest vicinity of the SMI tip is thus characterized by 1 or 2 singular exponents (1 - λ) where, 0<Re (λ)<1, and corresponding GSIFs that follow from numerical solution. In order to describe stress filed further away from the SMI tip, the non-singular exponents for which 1<Re (λ), and factors corresponding to these non-singular exponents have to be taken into account.
Analytical-numerical procedure of determination of stress distribution around a tip of sharp material inclusion is presented. Parameters entering to the procedure are varied and tuned. Thus recommendations are stated in order to gain reliable values of stresses and displacements.
Microdamage, Viscoelasticity and Viscoplasticity as Main Phenomena in Thermal Stress Relaxation in Laminated Composites
Authors: Varna Janis , Persson Magnus , Hajlane Abdelghani
Published: October 2016

Microdamage, viscoplastic and viscoelastic strain development in 90-layers of cross-ply laminates subjected to tensile loading is studied on unsymmetrical GF/EP laminates measuring the thermal curvature change. All three phenomena partially compensate for the effect of the thermal mismatch reducing the residual stress (specimen curvature). The viscoplastic strain contribution to curvature change is the largest whereas the effect of transient viscoelasticity is the smallest. Damage is included in the analysis through its effect on the effective transverse modulus of the 90-layer.
A Novel TEM Sample Preparation by Using Micro Magnetorheological Finishing
Authors: Luo Hu , Yin Shao Hui , Chen Feng Jun
Published: October 2016

A novel TEM sample preparation method is proposed in this paper, which utilizes magnetorheological finishing to thin TEM sample. It can effectively reduce subsurface damage caused by mechanical lapping. A magnetorheological polishing tool is designed to meet TEM sample thinning requirements. Thinning testis conducted on Φ3mm single crystal silicon. Polished surface is observed by using transmission electron microscope, and high-resolution microscopy image of single crystal silicon can be achieved.
Experimental Research on Dressing Parameters of the Plate in Planetary Double-Sided Grinding Process
Authors: Song De Bo , Zhu Xiang Long , Kang Ren Ke , Jin Zhu Ji , Shi Shuang Ji , Zhang Bi
Published: October 2016

Dressing parameters, which directly affect the flatness of the plate, are very important in planetary double-sided grinding dressing process. In this paper, trajectory and velocity equations of grit are studied. By comparing to the trajectory density of different annular regions, this paper puts forward an evaluation method of the shape of the plate and explores the impact of rotation speed on the shape of the plate. Finally, the experiments are performed by adjusting the rotation speed of the sun wheel and the plate. The results show that the flatness of the plate can be dressed below 0.01 mm, which validates the correctness of the theory.
Effect of Li2O, K2O and ZnO on Vitrified Bond Composites for CBN Grinding Wheels
Authors: Wang Zi Xuan , Yu Tian Biao , Zhao Ji , Wang Xue Zhi , Sun Xue , Liu Shi Xuan
Published: October 2016

To investigate the effect of Li2O, K2O and ZnO on SiO2-Al2O3-B2O3-Na2O vitrified bond for CBN grinding wheels, the refractoriness and fluidity of specimens with different additions were studied. The bending strength was measured by three-point bending tester and the microstructures were observed by super Depth-of-Field microscope. The results show that Li2O, K2O and ZnO can reduce the refractoriness and increase the high-temperature fluidity. Li2O and K2O make a contribution to improving the bending strength; however ZnO is harmful to specimens’ mechanical property. Additionally, the fluidity is important to control the number of gas bubbles in specimen according to the microstructure analysis.
Preparation and Test of Conventional Composite Abrasives Using Recycled Alumina Grains
Authors: Dutra Golanda Alexandre , Galisteu Luiz Sandro , Candioto Katia C. Gandolpho , Shigue Carlos Yujiro
Published: October 2016

In this work we report the preparation and evaluation of the mechanical characteristics of resin-bond composite abrasives using virgin and recycled alumina grains. The composite abrasives were made with phenolic resin as binder and as-received virgin and recycled alumina grains. Three different recycled alumina grains were studied: i) alumina from wood firing resin-bond abrasive tools; ii) alumina from wood firing vitrified-matrix abrasive tools; and iii) ground alumina from vitrified-matrix abrasive tools. The virgin alumina grains were employed in order to compare the mechanical performance of the prepared composite abrasive. The composition of alumina grains, analyzed by X-ray fluorescence spectroscopy revealed the recycled alumina grains have lower alumina content and higher concentration of silica in vitrified-matrix abrasives samples. The sand blast penetration tests have shown lower penetration depth in the virgin and the ground vitrified-matrix grains composites. The impact strength test results revealed its dependence on the alumina and silica content: samples with higher alumina content present the higher impact resistance whereas samples with higher silica content present lower impact strength.
A New Look into the Loose Particle Impact Process for Ductile Materials
Authors: Wang Jun , Li Wei Yi
Published: October 2016

Abrasive waterjet machining involves the impact of micro-particles at high or ultrahigh velocities. The material removal mechanism for ductile materials has been popularly accepted for over a half century as cutting wear and deformation wear caused by the component of impact force parallel and perpendicular to the target surface respectively. However, this definition of erosion mechanisms does not give an insight into the erosion process, but describes a surface phenomenon of the event. A computational study has been undertaken to reveal the underlying mechanisms of the material removal process. Based on the findings, the impact erosion mechanisms are re-defined as material destruction through (a) failures induced by inertia, (b) failure induced by elongation, and (c) failure induced by adiabatic shear bending. This new definition appears to better represent the physical process of material deformation and removal by loose micro-particle impacts at high and ultrahigh velocities.
Drilling of Rod End Faces Using Micro-Cutting Tools
Authors: Egashira Kai , Kuriyama Kenichi , Yamaguchi Keishi , Ota Minoru
Published: October 2016

There have been few reports on the drilling of microholes on rod end faces by cutting, which can be employed for fabricating micronozzles or microneedles. Such drilling was therefore attempted in the present study using a micro turn-milling machine with the tool and workpiece axes being parallel. The drilling was performed on the end faces of brass rods with cemented tungsten carbide micro-cutting tools processed by electrical discharge machining (EDM). As a result, a microhole 12‍ μm in diameter was successfully drilled using a 10-μm-diameter tool at a feed speed of 0.5‍ μm/s. The feed speed could be increased to 25 μm/s for a tool with a diameter of 20 μm and body length of 50 μm.
Critical Feed/Tooth Value Providing Finest Machined Roughness by Peripheral Cutting with Micro Endmills
Authors: Kobayashi Yasunori , Sakamoto Haruhisa , Ishii Akihito , Itoh Masayori
Published: October 2016

This study concerns the rational determination of machining conditions for micro endmills that are less than 1.0mm in diameter. The characteristics of machined surface roughness are measured according to machining conditions, especially the feed per tooth Sz. The machined surfaces conditions are also observed with SEM. From the experiments, the following are made clear: (1) The feed per tooth Sz at the critical value Szc makes machined surface roughness the finest. (2) The conditions of Sz larger than Szc make cutting marks regular, that is, stable cutting can be done under those conditions, and then, the roughness improves according to decreasing Sz. (3) The conditions of Sz smaller than Szc cause irregular machined surfaces including pileups and diggings, that is, cutting becomes unstable conditions. The excessively thin chip-thickness prevents from stably engaging edge on workpiece surface. (4) Although the values of Szc are independent from the type of machine tools and cutting speeds, the values decrease according to decrease in tool diameter. (5) The value of Szc increases when tool has worn over its limit. Therefore, in order to determine machining conditions rationally, the changing behavior of Szc should be understood according to tool wear.
Basic Study on Ductile-Mode Grinding of Optical Glass Lenses with Rubber Bonded Diamond Wheels
Authors: Kawana Yuya , Sekiguchi Rei , Mizumoto Yuta , Kakinuma Yasuhiro , Tanaka Katsutoshi , Fukuta Masahiko
Published: October 2016

Large aperture lenses with high surface quality are demanded for professional imaging products such as single-lens reflex cameras and astronomical telescopes. Large aperture optical lenses are shaped by ultra-precision grinding and finished by prolonged polishing. However, the prolonged polishing process leads to deterioration of the form accuracy. In order to reduce the amount of polishing, ductile-mode ultra-precision grinding is demanded. In this study, a rubber bonded wheel, which has a low elastic modulus, is used for grinding of spherical glass BK7, and influence of the hardness of the rubber bonded wheel and abrasive chip thickness on brittle fracture and surface roughness are experimentally investigated.
Analysis of Element Diffusion between Alloy Cast Iron and WC/Co Cemented Carbides
Authors: Liu T. , Zhang Song , Li Jiang Feng
Published: October 2016

An alloy cast iron has special properties by adding some alloying elements to the ordinary cast iron ASTMNo35A. Diffusion wear is one of the main cutting tool wear mechanisms in machining of the alloy cast irons. The diffusion of tungsten (W) and iron (Fe) between the alloy cast iron and the WC/Co cemented carbides was investigated in this paper by means of heating diffusion couple. It has be proved from the experiment that Fe in the alloy cast iron diffused a deeper distance in the WC/Co cemented carbides with the higher Co content; while the diffusion of W element in the WC/Co cemented carbides the alloy cast iron was not serious. The Vickers-hardness analysis of the alloy cast iron and K20 cemented carbide couple was determined. The elements diffusion impaired the hardness of the alloy cast iron and WC/Co cemented carbide cutting tool.
Multi-Scale Topography Analysis of Multi-Axis Machined Surfaces Based on Dual-Tree Complex Wavelet Transform
Authors: Qin Wen Zhen , Zhao Jun , Huang Wei Min , Wang Da Wei
Published: October 2016

Multi-axis ball end milling experiments of H13 die steel have been conducted with four different cutter postures, and the 3D topographies of machined surfaces are acquired by optical profiler. The multi-scale analysis is carried out on the machined surfaces based on 2D dual-tree complex wavelet transform (2D DT-CWT). The topographies are decomposed into different frequency bands, and the roughness in every frequency band is calculated. The results reveal that the roughnesses of the machined surfaces under different cutter postures are quite different, the roughness is the lowest when the lead angle is 12° and the tilt angle is-22°. The roughnesses under different cutter postures exhibit similar changing trend with the variation of frequency bands: the roughnesses in the high and low frequency bands are relatively lower, the roughnesses in the medium frequency bands are higher. The 2D DT-CWT provides an ideal comprehensive topography analysis method for performance evaluation of machined surfaces.
Proposed Stable Machining Condition Search Method Based on Machined Surface Information after End Milling
Authors: Aotani Kaito , Shiota Ryosuke , Hirogaki Toshiki , Aoyama Eiichi
Published: October 2016

Chatter vibration in end milling remains a serious problem for manufacturing engineers. Chatter vibration often leaves a characteristic pattern or chatter mark on the machined surface. Chatter marks are generated by the relative displacement of the tool and the workpiece. Closer observation of chatter marks may prove useful in understanding chatter vibration. In this study, we investigated chatter mark patterns on end-milled surfaces. Based on these observations, we proposed and demonstrated the effectiveness of an iterative analysis method to identify stable machining conditions and minimize chatter vibration in various operations without use of sensors under specific conditions.
Characteristic of Tool Wear in Small End Milling of Nickel-Titanium Alloy
Authors: Hamaguchi Kazuya , Kodama Hiroyuki , Okuda Koichi
Published: October 2016

This paper deals with the characteristics of tool wear in small end milling of nickel-titanium alloy which is used as a medical material. Cutting experiments were carried out by varying the axial relief angle of an end mill of a diameter of 0.5 mm from 0 to 15 degrees with a step of 5 degrees, and tool wear and surface roughness was evaluated. The result revealed that tool wear of a small end mill with an axial relief angle of 0 degree was smaller by 60% than that of 15 degrees, suggesting that tool wear is reduced more with a smaller axial relief angle.