bluuebunny/crossref_metadata_2025 huggingface dataset:
Precision Shaping Experiment of Ceramic Ball Blank with Oscillating-Plate Lapping Method
Authors: Lyu Bing Hai , Dong Chen Chen , Zhou Fen Fen , Deng Qian Fa , Yuan Ju Long , Zhao Ping
Published: September 2014

An oscillating-plane lapping method, by which pre-sintered ceramic ball blanks are shaped before full sintering, was proposed to improve the precision of the ceramic ball blanks. For good sphercity and diameter consistency of ceramic ball blanks obtained after this shaping process, much less workmaterial is needed to be removed in the following lapping process of the full sintered ceramic ball blanks. Shaping experiments were carried out on a newly developed oscillating-plane lapping device. Results show that material removal rate of the pre-sintered Si3N4 ball blanks with nominal diameter Ø13mm reaches 0.92mm/h in average. The sphericity error is reduced from 0.07-0.196mm to 0.002-0.006mm, and the consistency error of diameter is reduced from 0.309 to 0.019mm after 45min's shaping. Compared with the processing time of the unshaped full-sintered blanks in the following lapping process, it takes just a half time for the shaped full-sintered blanks to be semi-finished in this study. It indicates that the oscillating-plane lapping is a promising high efficient method to improve the precision and consistency of the ceramic ball blanks, and the efficiency of the followed lapping process can be improved notably.
Micro-Cracks Removal on Edge Surface of Thin Glass Sheet Using Magnetorheological Finishing
Authors: Sato Takashi , Kum Chun Wai , Ng Seow Tong
Published: September 2014

Micro-cracks on the edge surface of thin glass edge sheet have been identified as a key factor of catastrophic glass breakage. Hence, their removal will strengthen the thin glass substantially. This paper studies the glass edge finishing using magnetorheological finishing (MRF). The thin glass sheet edge is finished by shear force exerted by magnetorheological fluid, which is magnetically held by a specially designed magnetic wheel tool. All micro-cracks can be removed from the edge surface and the surface roughness improves fromRa0.5 μm toRa0.03 μm.
The Topographic Characterisation of Grinding Wheels – A Proposed Measurement Strategy
Authors: Butler David Lee
Published: September 2014

The surface of the grinding wheel and the conditions under which it is prepared has a profound influence upon the grinding performance as characterised by the grinding forces, power consumption, cutting zone temperature and component surface finish. Only by having a clear understanding of the wheel topography can the interaction of the grinding wheel surface with the workpiece be fully understood. Two dimensional measurements or profilometry, while being a relatively quick measurement to perform, suffers from information quality issues due to the subjectiveness of the profile location as well as questions regarding how representative a profile is of a three-dimensional real surface. While profilometric measurement has long been standardised in the form of various international standards, topographic standards have only recently been agreed upon and formalised as ISO 25178. In this paper a comprehensive approach to wheel topographic characterisation will be undertaken. Factors such as measurement strategy, filtering, active grain identification as well as the fidelity of surface replication will be considered. The paper will propose a recommended measurement strategy and surface parameter set deemed sufficient to provide a comprehensive understanding of the grinding wheel topography.
Estimation of Machining Error in Ball-End Milling of Hemispherical Surface Based on Measured Cutting Force
Authors: Shimana Kenji , Kondo Eiji , Yamashita Shunichi , Kawano Yoshihiro , Kawagoishi Norio
Published: September 2014

For a cutting process using a low-rigidity end mill, it is very important to be able to estimate the degree of machining error caused by the deflection of the tool. The purpose of this study is to establish a method of estimating, in real time, the machining error caused by the deflection at the cutting point of an end mill. To this end, in this research, a method for estimating the machining error caused by the deflection of the tool used for the ball-end milling of a hemispherical surface was verified by comparing the estimated and measured deflections of the tool. As a result, it was found that the machining errors in ball-end milling could be estimated from the normal force at the moment when the radial direction of the peripheral cutting edge is normal to the feed direction of the tool.
Monitoring of Wear Land Width of Diamond Tool Cutting Edge with Large Nose Radius in Ultra-Precision Cutting Using Static Cutting Forces
Authors: Kondo Eiji , Iwamoto Ryuichi , Kobaru Yuya
Published: September 2014

Large wear of diamond tools for ultra-precision cutting of soft metals deteriorates quality of machined surface, and the worn tools have to be replaced with new tools when the tool wear reaches limited wear land width of cutting edge generating finished surface. However, it is difficult to predict the tool life since all cutting tools have individual tool life. Therefore, the purpose of this study is to estimate wear land width of cutting edge of a single crystal diamond tool having large nose radius by using static cutting forces during machining. As a result of the cutting tests and measurements, it was found that the ratio of thrust force to principal force had good relation with the ratio of flank wear land area to cutting cross section area. Furthermore, according to some detailed observation of flank wear, width of flank wear land was greatly related to uncut chip thickness obtained under different cutting conditions and it was found that width of flank wear land could be estimated by measured static cutting forces and cutting conditions.
Effectiveness Evaluation of Novel Pad Dressing Method by Flexible Fiber Dresser - Tool Life Evaluation of Flexible Fiber Dresser
Authors: Uneda Michio , Takahashi Naoki , Arai Yutaro , Fujita Takashi
Published: September 2014

Chemical mechanical polishing/ planarization (CMP) is a key technology for fabricating high-efficient semiconductor devices, and the CMP characteristics (removal rate and accuracy, etc.) is depended on the various consumables represented by slurry, polishing pad and dresser used in the CMP process. Currently, in the pad, there are many studies that have pointed the evaluation methodology and the correlation between the pad surface asperity and the CMP characteristics. On the other hand, the dresser is one of the most important consumables because the dresser can control the pad surface asperity, and the diamond grains electrodeposited dresser (diamond dresser) is frequently used. One drawback point of the diamond dresser is that the dressing performance declines owing to the deterioration of the diamond grains. Previously, we have developed a novel flexible fiber dresser that would ensure high performance and longer life of tools, and we have reported the fundamental characteristics by the flexible fiber dresser compared with that of the diamond dresser. In this paper, we will show the results of tool life evaluation of the flexible fiber dresser using a contact image analysis method. As a result, the flexible fiber dresser can be continuously used over 35 hours. Furthermore, the result of having examined the stability of the removal rate of a silicon wafer is reported. Therefore, we found that the flexible fiber dresser is one of the most effective dressing methods for the polishing pad.
Experimental Investigation of Copper-Tungsten Electrode Wear in EDM
Authors: Yu Jian Wu , He Li Hua , Sheng Xiao Min , Duan Wen , Yin Shao Hui , Shang Zhen Tao
Published: September 2014

Copper-tungsten alloy which is widely used in the field of EDM has high melting temperature and excellent electrical and thermal conductivity. Copper tungsten electrodes for electrical discharge dressing of metal-bond wheel were studied, and experiments were conducted to observe their wear performance in this paper. Orthogonal experiment was designed to explore the wear at the edge of and the bottom of electrode with the machining of holes. Thickness of the carbon layer, micro topography and experimental results were analyzed. Low current and big pulse duration can reduce the electrode wear rate. Although carbon on the electrode surface can be wiped out easily, wear rate of copper-tungsten electrode decreases with the increasing in thickness of the carbon at the initial phase. There are fewer cracks and residue presented on the machined surface by microscope.
Study on Grinding Force Distribution on Cup Type Electroplated Diamond Wheel in Face Grinding of Cemented Carbide
Authors: Fujiwara T. , Tsukamoto Shinya , Ohashi Kazuhito , Onishi Takashi
Published: September 2014

In order to establish a high performance grinding method of cemented carbide, the grinding force distribution on the working surface of the cup type electroplated diamond grinding wheel is experimentally analyzed with the grinding force variation of face grinding, which is carried out on the narrow workpiece. The grinding force distribution is obtained by the successive difference of the grinding force variation. The grinding state becomes steady as soon as beginning of the interference of grinding wheel in workpiece, because the edge profile of workpiece is formed as same as the envelope of the grinding wheel. Main conclusions obtained in this study are as follows. In the region of the front edge of the grinding wheel, relatively large grinding force occurs, then in the region of the rear edge of the grinding wheel, the grinding force becomes smaller. In the left right-side end of the wheel, the grinding forces are larger than the center of the wheel. It is made clear that the grinding force distribution shows the peak value near the outer part of the wheel, and the peak value is larger in the center part of the wheel, on the contrary, the peak width become broad in both the left and right-side end of the wheel.
Research on Grinding of Silicon Particles Reinforced Aluminum Matrix Composites with High Volume Fraction
Authors: Zhang Fei Hu , Wang Kai , Fu Peng Qiang , Wu Meng Nan
Published: September 2014

With silicon particles reinforced aluminum matrix composites with high volume fraction becoming a new hotspot on research and application in the aerospace materials and electronic packaging materials, the machinability of this material needs to be explored. This paper reports research results obtained from the surface grinding experiment of silicon particles reinforced aluminum matrix composites using black silicon carbide wheel, green silicon carbide wheel, white fused alumina wheel and chromium alumina wheel. The issues discussed are grinding force, surface roughness, the comparison of different grinding wheels, the micro-morphology of the work piece. The results showed that the grinding force was related with the grinding depth and the grinding wheel material, the grinding force was increasing as the grinding depth growing. The surface roughness was between 0.29μm and 0.48μm using the silicon carbide wheel. The surface of the work piece had concaves caused by silicon particles shedding and grooves caused by the grains observed by the SEM and CLSM.
Concept Validation for Selective Heating and Press Hardening of Automotive Safety Components with Tailored Properties
Authors: Li Nan , Lin Jian Guo , Dean Trevor A. , Dry Damian , Balint Daniel S.
Published: September 2014

A new strategy termed selective heating and press hardening, for hot stamping of boron steel parts with tailored properties is proposed in this paper. Feasibility studies were carried out through a specially designed experimental programme. The main aim was to validate the strategy and demonstrate its potential for structural optimisation. In the work, a lab-scale demonstrator part was designed, and relevant manufacturing and property-assessment processes were defined. A heating technique and selective-heating rigs were designed to enable certain microstructural distributions in blanks to be obtained. A hot stamping tool set was designed for forming and quenching the parts. Demonstrator parts of full martensite phase, full initial phase, and differentially graded microstructures have been formed with high dimensional quality. Hardness testing and three point bending tests were conducted to assess the microstructure distribution and load bearing performance of the as-formed parts, respectively. The feasibility of the concept has been validated by the testing results.
Load Prediction for the Extrusion from Circular Billet to Symmetric and Asymmetric Polygons Using Linearly Converging Die Profiles
Authors: Ajiboye J.S. , Oyinbo S.T.
Published: September 2014

The deformation load is the most important parameter in the press design as it affects the structure and the general integrity of the final product. Therefore, every other parameter such as die shape, friction, type of process (hot or cold), and speed considered in modeling is optimized to cut back on the metal forming load. The flow of metal is largely influenced by the geometry of the die and hence the geometric shape of the tools is the main factor by which an optimum load can be evaluated. In extrusion process the strain distribution, resulting from deformation load, and other important variables that influence material structure, such as a hydrostatic stress, are strongly dependent on the geometry of the die. In the present investigation using linearly converging die profiles, the extrusion of symmetric and asymmetric polygons such as circular, square, triangular, hexagonal, heptagonal, octagonal, and L-, T-and H-, respectively sections from round billet have been numerically simulated. Mathematical equations describing the die profiles were derived, and then using MATLAB R2009b the co-ordinate of the die profiles was evaluated. A solid CAD model for the linearly converging die profile was made using Autodesk Inventor 2013 software and numerical analysis using DEFORM software for extrusion of the above sections from round billet was then performed to predict, for dry and lubricated condition, the extrusion load during deformation. It is found that the predictive loads for asymmetric shapes are found to be higher than that of the symmetric shapes. While there is no marked difference between the predictive loads for symmetric shapes that of the asymmetric shapes is significant where L-section has the highest extrusion load, followed by T-section and the H-section given the least pressure.
Experimental Investigation of Ti-6Al-4V with a Biaxial Tensile Test Setup at Elevated Temperature
Authors: Merklein Marion , Suttner Sebastian , Schaub Adam
Published: September 2014

The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.
Effects of Nonconstant Strain Rate on Forming Limit and Efficiency in High Pressure Pneumatic Forming of Ti-Alloy Components
Authors: Liu Gang , Wang Jian Long , Tang Ze Jun , Wu Yong
Published: September 2014

A process with gas pressure up to 70MPa is introduced, which is called High Pressure Pneumatic Forming (HPPF), comparing to superplastic forming (SPF) with pressure lower than 5MPa. HPPF process can be used to form tube blank at lower temperature with high energy efficiency and also at higher strain rate than SPF. With Ti-3Al-2.5V Ti-alloy tube, the potential of HPPF was studied through experiment in the temperature range of 700~850°C. To know the formability of the Ti-alloy tube, HPPF experiments of a large expansion tube and a square cross-section tube were carried out at different temperature and pressure. The limit expansion ratio and limit radius were measured to evaluate the forming limit of Ti-3Al-2.5V tube within HPPF. The results show that the lower the pressure, the better formability and the lower efficiency. At a constant pressure, the strain rate increases exponentially with bulging time during the free bulging procedure, but decreases exponentially during the small corner calibration. Through EBSD pictures, the deformation mechanism of the corner forming process in HPPF was analyzed. Because of a nonconstant strain rate deformation state and complicated stress and strain state during HPPF, the microstructure at the transition zone of the components are also nonhomogenous, but the grains are refined to a certain extent.
Key words: HPPF, Ti-3Al-2.5V, limit expansion ratio, corner forming
Experimental Investigation of Interfacial Compounds Evolution in Ultra-Thin Roll Bonded Cu/Al/Cu Strip
Authors: Song Hong Wu , Yu Yang , Xu Yong , Chen Yan , Zhang Shi Hong
Published: September 2014

Ultra-thin Cu/Al clad strip with 0.12 mm thickness was successfully fabricated by accumulative roll bonding and the interfacial structure of Cu/Al clad strip has been characterized by means of optical microscope (OM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and also X-ray diffraction (XRD). The intermetallic phases and their formation sequence at the interface was experimentally verified. And the growth kinetics of each phase was also modeled considering the diffusion controlled reaction mechanism. The effect of interfacial compounds on tensile fracture of ultra-thin Cu/Al clad strip was also studied. The obtained results indicate that, intermetallic compounds formed in the interface region of ultra-thin Cu/Al clad strip within the experimental condition are confirmed to be Al2Cu, Al4Cu9 and AlCu in sequence. The calculated activation energies for the growth of Al4Cu9, AlCu and Al2Cu are 101.45、114.30 and 95.15 kJ/mol, respectively. The major cracks propagate through the AlCu intermetallic layer and the Al2Cu / AlCu interface.
Dynamic Recrystallization Behaviour of Twin Roll Cast AZ31 Strips during Hot Deformation
Authors: Ullmann Madlen , Schmidtchen Matthias , Kawalla Rudolf
Published: September 2014

The recrystallization behaviour of a Twin Roll Cast AZ31 alloy, under deformation conditions corresponding to the initial stands of a magnesium hot rolling process, has been investigated. A set of strain levels, beginning at the critical strain for the onset of dynamic recrystallization has been studied. The dynamic recrystallization, taking place during hot deformation of magnesium alloy AZ31 is analyzed with help of plane strain compression tests conducted together with microscopic examination. Dynamically recrystallized volume fraction and size of dynamically recrystallized grains increase with increasing strain. When the strain is constant, the dynamically recrystallized volume fraction is higher at higher deformation temperatures or lower strain rates. Furthermore, it has been found out that deformation temperature plays a major role, rather than strain rates, in activating the dynamic recrystallization process during deformation. The results were used to identify the coefficients for the JMAK-model approach on the dynamic recrystallization of an AZ31 TRC-sheet.
Application of the Warm Hydroforming Process to the Manufacturing of Pre-Aged 6xxx Series Components Using a Numerical/Experimental Approach
Authors: Palumbo G. , Piccininni Antonio , Guglielmi Pasquale , Sorgente Donato , Scintilla Leonardo Daniele , Tricarico Luigi
Published: September 2014

In this work the Warm Hydroforming (WHF) process for the production of a 6xxx series Al alloy component has been investigated using a numerical/experimental approach: both experimental and numerical hydroforming tests were carried out using the alloy AC170PX, a pre aged (T4 condition) Al alloy often adopted for automotive applications. In order to evaluate both the mechanical and strain behaviour of the material, tensile tests were carried out at different temperature and strain rate levels using the Gleeble system 3180, keeping also into account the ageing effect; in addition, formability (Nakazima) tests in warm conditions were performed by means of a specific equipment and the Forming Limit Curves at different temperature levels were evaluated according to the ISO standard 12004-2. Hydroforming experiments were carried out using a prototypal press machine specifically designed for WHF and SuperPlastic Forming tests. Such tests, scheduled by a DoE approach, were aimed at investigating the suitability of using the investigated Al alloy in the WHF process: attention was thus focused on those parameters mainly affecting the aging phenomenon (temperature, heating time and cycle time). In order to overcome the actual physical limitation of the hydroforming facilities, a Finite Element (FE) model of the WHF process was also created implementing experimental data (flow stress curves and FLCs) and tuned using data from preliminary WHF tests. In particular, after setting the Coefficient Of Friction (COF) according to temperature and verifying the robustness of numerical simulations, the FE model was used for investigating: (i) the influence of the Blank Holder Force (neglected in the experimental campaign); (ii) the adoption of quite smaller values of the parameter cycle time (being the aim to determine higher strain rates in the material). Through the definition of proper response variables (Flatness, Bursting Pressure and Thickness Ratio) both experimental and numerical results were analyzed by means of polynomial Response Surfaces in order to evaluate the optimal process conditions.
Geometrical Phenomena in Tube Bending with Local Induction Heating
Authors: Tomczak Janusz , Pater Zbigniew , Gontarz Andrzej , Hadasik Eugeniusz , Cieśla Marek , Mutwil Kazimierz , Rzepka Wojciech , Kawała Tomasz
Published: September 2014

A theoretical and experimental analysis of heat induction bending for tubes used in the power industry is performed. First, the design of the heat induction bending process for tubes is described and industrial application areas for this technology are presented. Next, the main methods for tube bending with local induction heating are discussed and the effect of the technology on geometrical parameters of bends formed is presented. Then, the heat induction bending process for tubes is modeled using numerical techniques (FEM). The simulations are performed in a three-dimensional strain state, where thermal phenomena are taken into account, using the commercial software package Simufact Forming v. 11.0. In the simulations, the changes in workpiece geometry in the region of the bend being made (cross section ovalization, darkening and thickening of walls, neutral axis position) are examined. Also, potential phenomena that could limit the stability of the bending process and cause shape defects are predicted. The results of the numerical modeling are then compared to those obtained under industrial conditions.
Analysis of Insulating Object Plastic Injection Forming of Bicycle Dynamo Hub Power Connector
Authors: Chen Dyi Cheng , Jao Chih Hsuan , Huang Chen Kun
Published: September 2014

Bicycle industry has been an international reputation as bicycle kingdom in Taiwan, but the problem of global warming green energy rise, the development of insulating object of hub dynamo and power output connector to bring new hope to bike industry. In this study connector power output to gather public opinion related to patent, basis of collected documents as basis for design, structural components in least drawn to power output with simple connector. The study objectives connector hoped at structure strongest, highest efficiency in output performance characteristics such as use computer-aided drawing software Solid works to establish power output connector parts of 3D model. A series of simulation analyses, in which the variables relied on Moldflow and ANSYS software forming, which were execution to investigate the effective stress, effective strain, weld line, injection time, injection pressure and filling state of insulating object plastic injection forming of insulating object of bicycle dynamo hub.
Temperature Measurement in the Rotary Forming Process of a Nickel Superalloys (INCONEL) Sheet during Induction Heating
Authors: Kwiatkowski Michał , Zaba Krzysztof , Nowosielski Maciej , Pociecha Danel , Tokarski Tomasz , Kita Paweł
Published: September 2014

The processes of spinning and flow forming of hard metal sheets made from nickel superalloy INCONEL can be realized cold or with heating - e.g. by a induction or laser. When metal sheet is heated it is necessary to measure the temperature field on heated area, because its determines the deformation susceptibility. To control the temperature field pyrometers and infrared cameras are used. Due to strong changes in the surface of a formed material, under temperature influence (oxidation) and the action of the forming rolls, it is necessary to determine the emissivity coefficient values as a function of temperature and surface conditions. The paper presents the concept of determining these values, as well as an alternative technique for measuring temperature field, based on the methods of image analysis.
Development of Ferrite–Bainite Dual Phase (FBDP) High Strength Steel for Automotive Industries
Authors: El-Bitar Taher , El-Shenawy Eman , El-Meligy Maha
Published: September 2014

The proposed Ferrite-Bainite Dual Phase (FBDP) steel is suitable for automotive industries. The steel satisfies high specific strength (strength/weight ratio), which is positively reflected on both fuel consumption and crashing resistance.
Filling of Surface Pores on Aluminum Foam with Aluminum Powder by Selective Laser Melting
Authors: Kanatani Shigehiro , Matsumoto Ryo , Utsunomiya Hiroshi
Published: September 2014

To improve mechanical properties of a closed-cell type aluminum foam, the surface pores are filled with aluminum powder by selective laser melting (SLM). The relationship between the laser irradiation conditions and solidification characteristics of aluminum powder is investigated with one-line laser irradiation on the aluminum powder with a thickness of 5 mm. The aluminum powder is continuously melted and solidified with laser spot diameter of 0.6 mm and scanning speed of 10–20 mm/s. According to the successful melting and solidification conditions, the SLM is applied to the surface pores of a closed-cell type aluminum foam supplied with aluminum powder. The supplied aluminum powder is confirmed to be successfully melted and welded to the aluminum foam. As the result, the aluminum foam with nonporous surface layer (sandwich structure) is fabricated by the SLM with aluminum powder. The compressive behavior of the fabricated aluminum foam with nonporous surface layer is investigated.
Influence of Roller Shape on Deformation Behavior in Roll Bending of Structural Channels
Authors: Murasato Yuki , Makiyama Takahiro , Teramae Toshiya
Published: September 2014

Roll bending is a useful technology for manufacturing a wide variety of products in small quantities. However, the roll bending of structural channels, which have a complicated sectional shape, causes irregular deformation. On the other hand, there are fewer reports on the bending of structural channels compared to those on the roll bending of sheet-metals. The purpose of this study is to clarify the deformation behavior in the roll bending of structural channels. The present paper reports on the results from a finite element analysis of the effects of the roller shape on the deformation behavior in the roll bending of structural channels.
Lamb-Wave Based Damage Detection in Anisotropic Composite Plates
Authors: Sharif-Khodaei Z. , M.H.Aliabadi Ferri
Published: September 2014

Damage detection in anisotropic composite plates based on Lamb wave technique has been investigated. A network of transducers is used to detect barely visible damage caused by impact. A CFRP composite plate has been impacted and tested to verify the proposed damage detection algorithms. The difference in the propagational properties of Lamb waves in the pristine state and the damage state is used through data fusion and imaging algorithms to detect, locate and characterise the damage. The influence of directionality of the velocity on the validity of the detection algorithm is examined and some results are presented.
Numerical Study of a Plate with a Pre-Cracked Circular Notch
Authors: Caputo Francesco , de Luca A. , Lamanna Giuseppe , Soprano Alessandro
Published: September 2014

In the recent years, the study of the behaviour of damaged structures has been focused on cracked components in presence of an extensive material yielding at the crack tip; under this condition, linear elastic fracture mechanics theory (LEFM) is not able to describe the real plastic zone shape and size. Within this work, an extensive numerical analysis, based on elastic plastic fracture mechanics theory (EPFM), of the plastic zone size at the tip of a Mode I pre-crack at the notch edge in a plate is presented.
Flexural Property and Mode I Interlaminar Fracture Toughness of Plain Woven Carbon Fiber Reinforced Plastics after Water Absorption and Freezing
Authors: Katogi Hideaki , Takemura Kenichi
Published: September 2014

In this study, the effects of water absorption and freezing on flexural property and mode I interlaminar fracture toughness of Carbon Fiber Reinforced Plastics (CFRP) were investigated. Plain woven carbon fiber was used as reinforcement. Epoxy resin was used as matrix. Water absorption test was conducted at 90°C for 24, 100, 250 and 500 hrs. After water absorption, the specimens were kept under-15°C for 24 hrs. Static three point flexural and Double Cantilever Beam (DCB) tests were conducted after water absorption and freezing. As a result, flexural strength and mode I interlaminar fracture toughness of CFRP after water absorption and freezing decreased with an increase of immersion time. Flexural modulus of CFRP did not change after water absorption and freezing. And flexural strength and mode I interlaminar fracture toughness of frozen CFRP after water absorption were lower than those of water absorbed CFRP. From the observation using scanning electron microscope, it is understood that the water absorption and freezing affects the interfacial adhesion between fiber and matrix.
Fatigue Crack Propagation in Thin Wires of Ultra-High Strength Steel
Authors: Petit Jean , Sarrazin-Baudoux C.
Published: September 2014

Fatigue crack propagation is studied in thin wires of about 1 mm in diameter of an ultrahigh strength steel (σmax> 2400MPa) in ambient air and in air with controlled residual humidity. A specific equipment is developed based on an electro-dynamic testing machine equipped with an environmental chamber for air humidity control. Threshold tests are run using a load shedding procedure specifically adapted to the specimen size. The relation between load ratio and crack closure is evaluated from constant Kmax tests. The results are discussed on the basis of fracture surface observations and of existing modelling for environmentally assisted fatigue crack propagation.
Inelastic Dynamic and Non-Linear Static Seismic Performance of a Building with RC Walls that Collapsed in the Chile’s Earthquake of February 2010 and a Building with RC Concrete Frame Designed in the Mexico City
Authors: Avila Jorge A. , Lopez David A. , Avila-Haro Jorge Arturo
Published: September 2014

The objectives in this paper are the followings: evaluate the seismic performance of the three buildings and compare the elastic and inelastic seismic responses of the buildings, calculated with the records CCH-NS (Chilean earthquake 2010) and SCT-EW (Mexican earthquake 1985) of the cases of strengths elastic and inelastic with nominal strength and over-strength of each model. The building 1 is a real case of a concrete wall building that collapsed during the Chilean earthquake of February 27, 2010. The building 2 was analyzed and designed with the Chilean Norm “Seismic Design of Buildings” (NCH-433) and “Reinforced Concrete–Design and Calculus Requirements” (NCH-430). The analyses and design of the building 3 was realized with the Mexican Norms “Complementary Technical Norms for seismic design” (NTC-Seismic), “Complementary Technical Norms for Design and Construction of Concrete Structures” (NTC-Concrete) of the “Code of Constructions for the Federal District” (RCDF-04). The elastic and inelastic seismic responses of each building were calculated with the step by step dynamic method. Should be avoided that the fundamental period of vibration of the structures match with the dominant period of the ground (Ts). In the design of concrete structural walls is very important classified the walls according to its slenderness in order to recognize the behavior that will govern the wall, and with it determine the detailed of the steel reinforcement that could provide the best behavior when the wall be submitted to an important earthquake.
Influence of Annealing Process on Crystallinity of Glass Fiber Reinforced Easily Degradable PLA Composites
Authors: Tanaka Kazuto , Miyamura Misato , Okamoto Yoko , Katayama Tsutao , Katayama Tsutaki , Yoshikawa Seishi
Published: September 2014

To solve the problem of large environmental burden caused by disposal of FRP (Fiber Reinforced Plastics), Poly Lactic Acid (PLA), which is plant-derived and biodegradable, has received a lot of attention as an environmentally friendly material for the matrix of FRP. However, since the decomposition rate is very slow as compared with other biodegradable resins, it is difficult to make a processing of a large amount of PLA in the natural environment. Therefore, a method to accelerate decomposition rate of PLA by blending hydrolysis accelerator to PLA has been developed. In this study, composite material, in which PLA is blended with hydrolysis accelerator and reinforced with glass fibers, was molded using high speed compression molding process, and its tensile strength and the effect of heat treatment and tensile strength on the crystallinity was clarified. In consequence, regardless of the existence of hydrolysis accelerator, crystallinity of glass fiber reinforced PLA composites was improved by the annealing process. Tensile strength of glass fiber reinforced PLA decreased by the annealing process. For glass fiber reinforced PLA which was blended with hydrolysis accelerator, however, annealing process did not affect their tensile strength.
Low-Cost System to Evaluate Impact Localization in Composite Plates
Authors: Ribeiro A.L.A. , Mastelari N. , Cimini C.A.
Published: September 2014

The development of composite materials has been following a growing trend, with its use ranging from sporting goods to construction materials and defense. The aerospace industry in particular has observed a minute increase in demand for these materials, since the associated weight reductions promise significant savings in fuel related costs. Composite materials, however, are prone to important and very specific failure modes which are invisible to the naked eye (e.g., delaminations, fiber ruptures, debondings) and occur in response to everyday events such as impacts. Thus, usage of these materials in critical areas of airplanes (e.g. wings and fuselage) is subject to the development of technologies able to continuously and precisely monitor existence, type and extent of failures. Impact localization plays a key role within this paradigm allowing identification of hot spots, that is, areas subjected to potentially damaging phenomena, for further analysis. Several such techniques have already been developed, but anisotropy, precision, robustness and cost are common drawbacks amongst their implementation. The present study was directed to the use of conditioned piezoelectric sensors along with low cost commercial off-the shelf data acquisition system to implement a reliable impact localization method.
Corrosion Resistance Testing of the Galvanized Sheet Metal Braze Welding Joints
Authors: Magda Aurelian , Codrean Cosmin
Published: September 2014

The joining of the galvanized sheet is normally difficult to be done with classical methods, requiring special attention to the specific problems involved during the welding process. This paper presents the development of the joint technology by Cold Metal Transfer (CMT) of galvanized steel sheet using as filler material a CuSi wire electrode. The salt fog corrosion test was made to certify anticorrosive protection of the galvanized sheet metal joints. This test revealed a minimal deterioration of the galvanized zinc coating during welding and also confirms that using adequate technology galvanized steel can be weld without affected anticorrosive protection of the zinc layer.Experimental researches include optimization of the welding technology using CMT concept; technical skill development solutions of the joints; elaboration and implementation of laboratory advanced technology; experimentation and demonstration of technology functionality by obtaining of braze welded joints corrosion resistant.
Fatigue Behaviour of Al 6082-T6 Friction Stir Welded Tubular Joints under Torsional Loading
Authors: Hattingh D.G. , James M.N. , Susmel Luca , Tovo Roberto
Published: September 2014

The aim of the present research is to investigate the fatigue behaviour of friction stir (FS) welded tubular joints in aluminium alloy subjected to torsional fatigue loading. To manufacture the samples which were tested, an MTS I-STIR process development system was equipped with a retracting tool specifically designed for these tubular welds. Al 6082-T6 FS welded samples were tested under cyclic torsion with a nominal shear stress ratio equal to-1 and 0. The test data show that, strictly speaking, the presence of non-zero mean shear stresses has a detrimental effect on the overall torsional fatigue strength of the FS welded joints. However, the reanalysis discussed in the present paper suggests that, from a statistical point of view, any detrimental effect is small. This means that fatigue assessment under torsional fatigue loading of these FS welded tubular connections can be performed with little loss of accuracy by neglecting the presence of non-zero mean shear stresses.
Long Term High-Temperature Environmental Effect on Impact Toughness in Austenitic Alloys
Authors: Calmunger Mattias , Chai Guo Cai , Johansson Sten , Moverare Johan
Published: September 2014

Structural integrity is crucial for the safety of power plants with higher efficiency to meet the increasing global energy consumption. High-temperature environment will demand not only improved high-temperature corrosion resistance but also a maintained sufficient toughness. This study investigates how long term high-temperature environment influence the impact toughness of two austenitic stainless steels (AISI 304 and Sandvik SanicroTM 28) and one nickel-bas alloy (Alloy 617). Alloy 617 has shown increasing impact toughness with both increasing temperature and time, up to 700°C and 3 000 hours, while the two austenitic stainless steels have shown the opposite for the same conditions. At 10 000 hours the impact toughness of Alloy 617 has decreased but the alloy still possess great toughness. Both austenitic stainless steels show embrittlement due to brittle σ-phase and Alloy 617 seems to gain good impact toughness performance from small evenly distributed precipitates.
Localization of Barely Visible Impact Damage (BVID) in Composite Plates
Authors: Meng Shi Yang , Sharif Khodaei Zahra , M.H.Aliabadi Ferri
Published: September 2014

This paper exploits the implementation of a delay-and-sum imaging method using Lamb wave signals to localise barely visible impact damage (BVID) in quasi-isotropic composite panels. The structural discontinuities, such as opening and stiffener, has also been tested to reflect the common structural features of an aircraft and to examine the feasibility of the proposed detection technique. The prediction results are compared with ultrasonic C-scan images, which indicate location error for three different panels –flat panel, flat panel with an opening and stiffened panel. The accuracy is believed to be improved by increasing the number of transducers. Overall the proposed damage detection technique, with the use of only four transducers, demonstrated sufficient accuracy and efficiency in impact damage detection and can be applied alongside the traditional NDT inspections for providing a priori information of the impact damage location.
Validity of the Finite Fracture Mechanics Based Asymptotic Analysis for Predictions of Crack Deflection in Thin Layers of Ceramic Laminates
Authors: Ševeček Oldřich , Leguillon Dominique , Profant Tomáš , Kotoul Michal
Published: September 2014

The work studies and compares different approaches suitable for predictions of the crack deflection (bifurcation) in ceramic laminates containing thin layers under high residual stresses and discuss a suitability and limits of using of the asymptotic analysis for such problems. The thickness of the thin compressive layers where the crack deflection occurs is only one order higher than the crack extension lengths considered within the solution. A purely FEM based calculation of the energy and stress conditions, necessary for the crack propagation, serves as the reference solution to the problem. The asymptotic analysis is used after for calculations of the same quantities (especially of energy release rate – ERR). This concept enables semi-analytical calculations of ERR or changes in potential energy induced by the crack extensions of different lengths and directions. Such approach can save a large amount of simulations and time compared with the pure FEM based calculations. It was found that the asymptotic analysis provides a good agreement for investigations of the crack increments enough far from the adjacent interfaces but for longer extensions (of length above 1/5-1/10 of the distance from the interface) starts more significantly to deviate from the correct solution. Involvement of the higher order terms in the asymptotic solution or other improvement of the model is thus advisable.
Comparison of Full Field and Single Inclusion Approaches to Homogenization of Composites with Non-Ellipsoidal Pores
Authors: Tsukrov Igor , Drach Borys , Trofimov Anton
Published: September 2014

This paper compares two approaches to predict the overall mechanical properties of solids with irregularly shaped pores. The first approach involves direct finite element simulations of representative volume elements containing arrangements of irregularly shaped pores subjected to periodic boundary conditions. The second approach utilizes numerical results for individual defect shapes in a micromechanical scheme. Several realizations of parallel and randomly oriented distributions of defects are considered. It is determined that the Mori-Tanaka micromechanical scheme provides good correlation with the full field finite element simulations.
Application of Acoustic Emission for Identification of Differences in Fatigue Damage of Selected Materials for Power Plants
Authors: Mentl Vaclav , Vlasic Frantisek , Bartkova Denisa , Mazal Pavel
Published: September 2014

An acoustic emission is remarkable source of information about the fatigue process and its intensity under cyclic loading. Specimens made of reactor steel and INCONEL 713LC were subjected to bending fatigue loading in the high-cycle range. This study presents results of acoustic emission signal analysis. The main aim of this study is to propose a methodology for evaluation of the early manifestations of fatigue damage and to identify material changes in both materials by AE parameters. Signal comparison material indicates differences of damage mechanism in observed. An examination of crack initiation sites and microstructure has been also performed.Experiments were realized in cooperation between laboratories of Brno University of Technology and University of West Bohemia in Pilsen and its related to solving of project of the Czech Ministry of Industry and Commerce: “A diagnostic complex for the detection of pressure media and material defects in pressure components of nuclear and classic power plants“ and project New Technologies for Mechanical Engineering (NETME +).
Optimized Ultra High Performance Fiber Reinforced Concrete Mixture with Intensified Volumetric Stability
Authors: Park Jung Jun , Yoo Doo Yeol , Park Jun Hyoung , Kim Sung Wook
Published: September 2014

This study performed compressive, tensile and restrained shrinkage tests to find out the optimized mixture including shrinkage reducing admixture (SRA) and expansive admixture (EA) enabling to reduce the shrinkage of Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The test results showed that the mixture using 1% of SRA and 7.5% of EA satisfied the design strength criterion despite of slight loss in the compressive and tensile strengths. In addition, this mixture exhibited the lowest restrained shrinkage strain by offsetting the quick setting and delaying the development of the restrained shrinkage stress.
Very High Plastic Strain Zones in 304 Stainless Steel Small Punch Specimen Loaded at RT by Martensite Formation and Recrystallization Technique
Authors: Iino Y. , Yu Hyu Sun , Kong J.H. , Okumiya Masahiro
Published: September 2014

Very high plastic strain zones with equivalent plastic strain above 0.2, PZ0.2 and above 0.5, PZ0.5 in 304 stainless steel small punch specimens loaded at RT to various level were observed and measured by martensite formation and recrystallization technique, respectively. It is found that both the very high plastic zones are formed ,at middle stage of the small punch test, at first near the outer surface region of the specimen where the loading ball is contacted to the specimen. The zones extend with increasing load toward the inner surface. Thus the contact area part of the specimen with the ball causes a significant strain gradient through thickness. This will be due to the constraint of the plastic deformation near the contact region by the friction force.
Influence of Cold Weather on Compressive Strength in High Performance with Silica Fume
Authors: Jang Young Il , Park Wan Shin , Kim Sun Woong , Yun Song Hui , Yun Hyun Do , Khil Bae Su , Kim Do Gyum
Published: September 2014

This paper addresses the influence of cold weather on the compressive strength of high performance concrete with silica fume under different curing days. Test variables of this study are weather condition (5°C, -5°C and-15°C) and different curing days (7days and 28 days). In this work, the specimen was designed a water-binder ratio of 0.34. One batches of concrete were prepared for each mixing hour, and the compressive strength of cylindrical concrete specimens was measured after 7 and 28 days. Test results for concrete compressive strength show that the concrete’s best mechanical performance occurred when there was the least difference between ambient temperature and concrete temperature, that is, during the later hours of the day in hot weather conditions.