bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Process Parameters on Laser Beam Formed Titanium Alloy Sheet
Authors: Akinlabi Stephen , Akinlabi Esther Titilayo
Published: September 2014

Titanium alloy (Ti6Al4V) is the most widely used alloy grade of titanium in the aerospace industry because of its excellent properties. Laser beam forming is a highly flexible rapid prototyping and low-volume manufacturing process that employs laser-induced thermal distortion to shape sheet metal parts without hard tooling or external forces. The resulting formed shape and the curvature are determined by the beam power and size, scanning velocity, number of scan irradiations and the effect of cooling, all these form part of the process parameters that have to be optimised in order to achieve the desired shape and properties in formed components. Hence, a good control of the process parameters is inevitable to achieve these desired properties. Controlling a single process parameter in a process may be considered easy to manage than a system of multiple parameter process such as a laser beam forming process. This study investigates the effect of the scan velocity, laser power and cooling effect on the developed curvature with the aim of achieving good structural integrity.
Experimental Investigation and Phenomenological Modeling of the Quasi-Static Mechanical Behavior of TA6V Titanium Alloy
Authors: Gilles Gaëtan , Habraken Anne Marie , Duchêne Laurent
Published: September 2014

This paper proposes an experimental and numerical investigation of the quasi-static mechanical behavior of TA6V at room temperature. Different loading conditions (tension, compression, plane strain and simple shear) were applied on a 0.6 mm thick sheet in several in-plane directions. Based on the experimental results, several identifications are performed to determine the parameters involved in the CPB06 yield criterion and its extensions. The error/time computation ratio for the different identifications is next analyzed to fix the choice of the yield criterion. The latter is finally associated with an isotropic hardening law on the one side and a formulation taking into account the evolution of the yield locus on the other side in order to describe the material. The ability of the proposed formulations to predict the TA6V response is studied in the case of a deep-drawing process.
Experimental Research on Circular Milling of Bi-Layer Composite Materials Consisting of CFRP Laminates and Titanium Alloys
Authors: Yagishita H.
Published: September 2014

Recently, to construct an airframe 2-layer composite materials consisting of carbon fiber reinforced plastic (CFRP) laminates and TiAl6V4 still need to be machined, whereby drill holes are frequently machined. Special attention has to be paid to the machining quality, which implies hole dimensional accuracy, defect free peripheral zone, edge quality at inlet and outlet of hole and so on. Machining defects often occur as a consequence of excessive mechanical and thermal loads, which are often caused by wrong process conditions or by the wrong choice of machining process itself. With respect to widely used state-of-the-art machine tools providing high performance and equipped with potent control unit, for the comparatively large drill hole, circular milling gains interest as an alternative to the drilling operation [1, 2].
In this research, in order to select suitable machining conditions for 2-layer composite materials consisting of CFRP laminates and TiAl6V4 a large number of circular milling tests of 6 mm diameter are executed by using a high performance vertical milling machine. Hole diameter deviation from 6 mm and inner surface roughness in relation to number of hole machined are measured and evaluated for CFRP laminates and TiAl6V4. Moreover, from observations of cutting edges in relation to number of hole machined it is confirmed that under wrong machining conditions the difference of heat conductivity between CFRP laminates and TiAl6V4 induces for chips of TiAl6V4 to be deposited on the end cutting edges of endmill used. In this case tool life shortens extremely.
Orbital Forging of a Ti6Al4V Alloy Jaw Coupling Sleeve
Authors: Samołyk Grzegorz
Published: September 2014

The paper presents selected results of a numerical investigation of the orbital forging process for producing a hollow part. This part is a jaw coupling sleeve made of titanium alloy, widely used in the agricultural industry. The FEM simulation was performed based on the following assumptions: (i) the orbital forging process is conducted under hot conditions using an industrial press of MCOF type and (ii) the final part is formed from a special hollow preform. The preform shape was selected such to ensure optimal conditions of the orbital forging process. The aim of the investigation was to identify phenomena which occur during the orbital forging process. The results obtained are thoroughly examined and described.
Method for Producing Twist Drills by Extrusion Using a Three-Slide Forging Press
Authors: Bulzak Tomasz , Tomczak Janusz , Pater Zbigniew
Published: September 2014

The study presents a new method, developed by the authors, for producing twist drills by extrusion using a three-slide forging press. The method consists in using two sectional dies with specially shaped impressions that allow the removal of a ready drill from the die without unscrewing. The study describes the main assumptions of the new method for twist drill extrusion, discussing benefits offered by this method when compared to the conventional process for producing twist drills by extrusion using a monolithic die. In order to verify the proposed solution, dies conforming to the assumptions of the new method were designed and executed. Experimental tests were conducted under laboratory conditions using a three-slide forging press. The model of the material used in the experiments was assigned the properties of Pb1 lead. As a result of the experiments, the theoretical assumptions of the new method could be examined and its practical application verified. Also, ideas for further research aimed at better understanding of the new technology for producing twist drills by extrusion are presented.
Effect of Hot Forging and Different Cooling Rates on the Microstructure, Mechanical Properties of Carbon Steel Containing 0.8 and 1.2Al
Authors: Farahat Ahmed Ismail Zaky , Elfawkhry Mohamed Kamal
Published: September 2014

Two alloys of steel containing nominally 0.45C-1.0Si-2.0Mn-0.8Al and 1.2Al were cast in open air induction furnace. Dilatation testing was carried out to recognize the effect on Aluminum on the different critically transformation temperatures. The alloys were hot forged at 1200°C and then subjected to different cooling rates. Mechanical testing was carried out at room temperature. Optical and SEM microstructure were observed. X-ray diffraction was conducted to observe the microstructure constituents.
Modelization and Validation of Ti-6Al-4V Alloy Material Constitutive Law for Isothermal Forging Process
Authors: Zhang Chao , Yang Xiao Guang , Zhou Jian Hua , Huang Ai Jun
Published: September 2014

Isothermal forging is a near-net shape forming technology for manufacturing complex titanium alloy components. In order to characterize the workability of Ti-6Al-4V alloy during isothermal forging process, the material properties of Ti-6Al-4V alloy were investigated by isothermal compression tests under different strain rate-temperature, where the temperature range is 850~1000 °C and strain rate range is 0.001~0.05s−1. The obtained flow stress-strain data was used to develop the Arrhenius constitutive model of which material constants considered the compensation of strain. The developed constitutive model was used to simulate the isothermal forging process of Ti-6Al-4V alloy component by finite element (FE) based numerical method. The metal flow and potential defect locations were predicted by numerical simulation. Furthermore, the relevant simulation results were compared with the product in industrial workshop to demonstrate the validity of material constitutive model.
Keywords: Isothermal forging; Ti-6Al-4V alloy; Hot compression test; Arrhenius constitutive model; FE analysis; Model validation;
A Novel Experimental Design to Obtain Forming Limit Diagram of Aluminium Alloys for Solution Heat Treatment, Forming and In-Die Quenching Process
Authors: Shao Zhu Tao , Bai Qian , Lin Jian Guo
Published: September 2014

Solution heat treatment, forming and in-die quenching (HFQ) is a patented process to form complex shape metal components at a high efficiency and a low cost. Conventional experiment approaches to determine forming limit curves (FLCs) at different strain paths are not applicable for the HFQ forming process. A novel biaxial tensile test rig is designed to overcome the difficulties and determine the FLCs at high temperatures based on the commercial Gleeble machine. This test device employs the circle plate and connecting rod mechanism in order to achieve different strain states, such as uniaxial tension, plane strain and biaxial tension. Resistance heating and air cooling are adopted to obtain an isothermal environment and to control cooling rates in Gleeble respectively. The designs of the cruciform specimen for this test are also introduced in this paper.
Characterization of UFG Microalloyed Steel Produced by Combined SPD Treatment
Authors: Majta Janusz , Muszka Krzysztof , Kwiecień Marcin , Stefanska-Kadziela Monika , Lisiecka-Graca Paulina
Published: September 2014

Studies of the effects of inhomogeneity of UFG (ultrafine-grained) microstructure evolution have been performed on severely deformed specimens produced by AAD (angular accumulative drawing), followed by wire drawing and wire flattening processes i.e. “top-down” systems of the grain refinement process. In this paper, deformation behavior and size effects are illustrated by means of UFG microalloyed steel with different combinations of microstructure length scale and deformation inhomogeneity. The refined and severely elongated structures were investigated by light microscopy, TEM and EBSD. Of particular importance was the understanding of the effects of strain path, microalloying elements and deformation inhomogeneity on grain refinement and dislocation substructure formation processes.
Fundamental Investigation for Tensile Test Using Conical Cupping Die
Authors: Ota Tomoyuki , Iizuka Takashi
Published: September 2014

A number of researches have conducted in order to evaluate the ductile fracture occurrence by using forming limit diagram. However, specimen shape and testing machine for obtaining forming limit diagram of sheet metal have some problems. The problem about specimen shape is occurring at the specimen edge. In uniaxial tensile test, the specimen edge may cause a defused neck in width direction and may have influence on fracture occurrence. In biaxial tensile test by using a cruciform specimen, a uniform biaxial deformation is not obtained because uniaxial tensile stress occurs at the specimen edge. Tensile test by using a specimen which does not have such edges should carry out, for example, in bulge test and multi-axial tube expansion test, specimens without edge are used. However, these methods need special machines. Therefore, new biaxial tensile testing method is required. By this method, materials deform depending on biaxial strain state by using popular pressing machines.
Study on Hot-Working Behavior of High Carbon Steel / Low Carbon Steel Composite Material Using Processing Map
Authors: Gao Xing Jian , Jiang Zheng Yi , Wei Dong Bin , Jiao Si Hai , Chen Deng Fu
Published: September 2014

The high carbon steel (HCS)/low carbon steel (LCS) laminated composite made by centrifugal casting technology was subjected to hot compression tests on Gleeble 3500 thermomechanical simulator in a range of temperatures (800-1100 oC) and strain rates (0.02-10 s-1). The hot-working behavior of the laminate was characterised by analysing the flow stress-strain curves and constructing the processing map based on dynamic materials model via superimposing efficiency of power dissipation and flow instability maps. The safe and unsafe processing conditions were identified in the processing map which was validated by microstructural examinations. Banded microstructure and micro-shear cracks occurred in the unsafe domains were responsible for the flow instability, while dynamic recrystallisation in stable domains with high efficiency of power dissipation imparted a good workability to the laminate. The optimum hot-working parameters were determined to be: (i) 800-1050 oC and 0.02-0.04 s-1, (ii) 800-1045 oC and 2.5-10 s-1 and (iii) 1050-1100 oC and 0.02-2.5 s-1.
Analysis into Differences between the Buckling in Single-Point and Two-Point Incremental Sheet Forming of Components for Self-Supporting Sheet Metal Structures
Authors: Bailly David , Bambach Markus , Hirt Gerhard , Pofahl Thorsten , Herkrath Ralf , Trautz Martin
Published: September 2014

In the architecture and construction sector the trend for individualization is often expressed in complex-shaped freeform buildings. Due to missing universal and mature construction methods for freeform buildings, they are usually realized with customized solutions that often include massive, material-consuming substructures, while the visible skin has neither structural nor functional properties. In this context a new concept for self-supporting lightweight structures for the realization of free-form surfaces and the production of the corresponding components has recently been proposed. Taking into account the large part dimensions and the varying part geometries in this application a flexible production chain based on incremental sheet forming has been developed and optimized. It has been validated by producing six-sided large-scale pyramids in 140 similar variants which were assembled to a self-supporting free-form demonstrator. Two-point incremental sheet forming (TPIF) was used with a universal partial supporting tool with the goal to produce all variants without dedicated tooling. Although the majority of pyramids was produced successfully with the applied TPIF strategy, there was a small number of parts with a very asymmetric shape that showed severe buckling in the side walls. For a detailed analysis of this observation the asymmetry was quantified using a wall angle ratio. Subsequently, a single-point incremental sheet forming (SPIF) strategy was successfully applied as an approach to avoid buckling. The results confirm the assumption that the circumferential expansion in SPIF suppresses buckling due to tensile stresses in the side walls, whereas the circumferential compression in TPIF triggers buckling due to the compressive stresses in the side walls.
Comparative Study for Springback Prediction on Single Point Incremental Forming Process
Authors: Oleksik Valentin , Pascu Adrian , Bondrea Ioan , Avrigean Eugen , Rosca Liviu
Published: September 2014

The present paper proposes a comparative study in order to determine the springback in single point incremental forming process. Using the Ls-Dyna software the process was simulated for one piece in frustum of pyramid shape. In the end of the explicit dynamic analysis, it was run, using the same software, an implicit analysis to determine the springback. For this comparison study we selected four different shell formulations. The results obtained in this simulation were compared with those obtained experimentally for the same part. The experimental research was conducted on a robot and, on the opposite side of the machined surface, an Aramis measuring optical system was placed to allow the online determination of deformations, displacements and thinning of material. Also, using this system, the springback was determined at the end of forming process. The closest values were obtained when using fully integrated formulation with thickness-stretch with 11 integration points on material thickness.
Experimental Study on the Incremental Forming of Coated Aluminum Alloy Sheets
Authors: Astarita Antonello , Carrino Luigi , Durante Massimo , Formisano Antonio , Langella Antonio , Minutolo Fabrizio Memola Capece , Paradiso Valentino , Squillace Antonino
Published: September 2014

Superficial coatings are widely used in industrial applications in order to improve the superficial properties of metallic components. In particular, in the aeronautic field, all the components are coated in order to prevent both corrosion and wear. In this field, heat treatable aluminum alloys, in age hardened condition, are used; consequently, superficial coatings must be carried out through “cold” processes, i.e. coating processes in which the component to be coated remains at low temperatures, below 100°C. Cold gas dynamic spray technique (CGDS) is a process of deposition that consists in the realization of surface coatings with high-velocity metal particles sprayed on the substrate at temperature significantly lower than the melting one of the substrate itself and at relatively low temperatures if compared to other spray techniques. When processing conditions are optimized, the process can produce near fully dense coatings. This technique could be particularly useful in the coating of rolled sheets, needing of successive cold plastic deformations.
One of the cold plastic processes is incremental forming, a high flexible process for rapid manufacturing of complex sheet metal part shapes; it presents the potential to be easy to automate and particularly attractive for small batches and customized parts. In this process, a simple tool describes a path that allows to locally deform the sheet clamped along its periphery.
The aim of this paper is to study the evolution and behaviour of aluminum coating deposed by CGDS on AA 2024-T3 sheets carried out by an incremental forming process. This evaluation is carried out by characterizing the cold sprayed coating after the forming process for different wall angles of simples geometries.
Innovative Machine Design for Incremental Profile Forming
Authors: Grzancic Goran , Becker Chrstioph , Hermes Matthias , Tekkaya A. Erman
Published: September 2014

The Incremental Profile Forming process (IPF) is a new method to manufacture tubes and profiles with variable cross-section design along the centre-line of the profile. The innovative process design enables the combination of high workpiece complexity and high process flexibility. For this reason, a machine concept was developed and finally a prototype realized. The new machine consists of eight numerically controlled axes, which allow the processing of thinwalled tubes and profiles with a maximum diameter of 80 mm. The design of the machine combined with the control system leads to a forming technology with a high degree of flexibility, which is an advantage of the process. Depending on the final workpiece shape the forming process proceeds in several steps and can therefore be considered as an incremental forming process. Furthermore, the tool concept supports both a kinematical and a form-closed forming process.
Simulative Model for the Evaluation of Thermo-Mechanical Effects in Friction Stir Spot Welding (FSSW) of Aluminum Sheets
Authors: D’Urso G. , Giardini Claudio
Published: September 2014

A study was performed to evaluate how the Friction Stir Spot Welding process parameters affect both the thermal distribution in the welding region and the welding forces. An experimental campaign was performed by means of a CNC machine tool and FSSW lap joints on AA6060-T6 aluminum alloy plates having a thickness of 2+2 mm were executed. Five thermocouples were inserted into the samples at a specific distance from the specimen center. A set of tests was carried out by varying the process parameters, namely rotational speed, axial feed rate, plunging depth and dwell time. Axial welding forces were also measured during the execution of the experiments by means of a piezoelectric load cell. The experimental data collected were used to set up and to validate a simulative model of the process. In particular, a 2D FEM model was set up using the commercial code Deform 2D. A 2-dimensional FEM code was preferred in order to guarantee a very simple and practical model able to achieve results in a very short time. Since it is not possible to simulate the rotation of the tool in a 2D configuration, a specific external routine for the calculation of the developed thermal energy due to the friction between tool and workpiece was set up and implemented into the code starting from the local pressure distribution along the contact area.
Extrusion Limit Diagram of Mg Alloy by Using Finite Element Method
Authors: Lee Sang Kon , Lee Seong Yun , Lee In Kyu , Jeong Myeong Sik , Jo Yong Jae , Kim Da Hye , Lee Jae Wook , Lee Kyung Hun
Published: September 2014

In order to prevent the surface defect in the magnesium alloy extrusion process, it is important to set an appropriate process condition. The extrusion limit diagram is very useful to achieve the maximum extrusion speed without surface defect. In this study, the extrusion limit diagram for the magnesium alloy extrusion is constructed by using extrusion experiment and finite element analysis. For finite element analysis hot compression test is carried out to obtain the effective stress and stain curves according to the various strain rates and temperatures. The effectiveness of the constructed extrusion limit diagram is verified through the porthole extrusion experiment for producing the magnesium alloy bumper beam.
Optimization of Pressure Path in Sheet Hydroforming Process Using Artificial Intelligence and Simulated Annealing
Authors: Yaghoobi Amirreza , Bakhshi-Jooybari Mohammad , Gorji Abdolhamid , Baseri Hamid
Published: September 2014

The success of sheet hydroforming process largely depends on the loading pressure path. Pressure path is one of the most important parameters in sheet hydroforming process. In this study, a combination of finite element simulation, artificial intelligence and simulated annealing optimization have been utilized to optimize the pressure path in producing cylindrical-spherical parts. In the beginning, the finite element model was verified based on laboratory experimental results. The experiments were designed and a radial basis neural network model was developed using data generated from verified finite element model to predict the thickness in the critical region of the product. Results indicated that the neural network model could be applied successfully to predict the sheet thickness in the critical region. In addition, the neural network model was used as a fitness function in simulated annealing algorithm to minimize the thickening in the above mentioned critical region. The final results showed that utilization of the optimized pressure path yields good thickness distribution of the part.
Superplastic Blow Forming of Aerospace Components
Authors: Lee Ho Sung , Yoon Jong Hoon , Yoo Joon Tae
Published: September 2014

Many metals, such as titanium and superalloys, are used for a wide range of aerospace applications, which include aircraft gas turbine engine and space launcher propulsion engine. In order to manufacture a stiffened extension with superplastic blow forming at elevated temperature, the structural integrity of the joint part was investigated since the welded or bonded joint of internal channels should maintain its strength during superplastic blow forming process. Various types of joint methods were performed in order to investigate microstructural and mechanical properties of the bonded specimen at elevated temperature. In this paper, the possibility of manufacturing combustion chamber and other aerospace components with superplastic blow forming of titanium and superalloy was demonstrated. An innovative manufacturing method to produce complex configuration from titanium multi-sheets by superplastic forming with low hydrostatic pressure was presented. The result also shows that the manufacturing method with superplastic blow forming of multi-sheets of IN718 alloy has been successfully demonstrated for near net shape forming of subscale nozzle extension cone with internal channels.
Microstructural Unit Controlling Cleavage Crack Propagation in High Strength Bainitic Steels
Authors: Medina Sebastián F. , Rancel Lucía , Gómez Manuel , Cabrera Jose María , Gutiérrez Isabel
Published: September 2014

The strengthening mechanisms which are operative in bainite are very well known: small bainite packet, small width of the laths, dislocation density and size and number of carbide particles (Fe3C), among others. Bainite packet size has been traditionally considered as the value measured by optical microscopy (OM), as electron back scattered diffraction (EBSD) technique is relatively recent. In a V-microalloyed steel with bainitic microstructure of C=0.38%, V=0.12% and N= 0.0214% the average length and width of ferrite laths and of cementite carbides were measured. On the other hand, the bainite packet size was measured by OM and EBSD with a misorientation of 15o. These values of the microstructural units have been taken in account to calculate the effective surface energy γp given by Griffith’s model for cleavage fracture. It was concluded that bainite packet size determined by EBSD with a misorientation angle criterion of 15o was the microstructural parameter that controls cleavage crack propagation. Given the relationship between the average unit crack path (UCP) and the bainite packet size, it was concluded that the effective surface energy of cleavage fracture (γp) would be between 71.6 and 82.6 J m-2.
Metal Powder Injection Molding Process for Manufacturing Adapter Component
Authors: Jeon Jin Woo , Yun Jeong Hwan , Jeong Myeong Sik , Kim Yang Gon , Park Hoon Jae , Bae Gi Man , Sung Ji Hyun
Published: September 2014

Adapters are a component of the output system in the internally geared hub for a bicycle. Originally, adapter parts were produced by a machining process with low productivity and material usage rate. In this study, the metal powder injection molding (MIM) process has been applied as an alternative manufacturing method to the machining process. Microstructure analysis and mechanical property testing has been conducted in order to select the material for the adapter with changes in the nickel content. The geometrical precision of the adapter is measured by using three-dimensional scanner with various mixing ratios of the powder and the binder. The developed alternative process for the adapter results in increased productivity and material usage rate. Previously, this process was only used for small parts less than 10 mm in diameter. With this development, the MIM process may be used more widely than before.
Hot Rolled Coil Property Heterogeneities due to Coil Cooling: Impact and Prediction
Authors: Jacolot Ronan , Huin Didier , Marmulev Artem , Mathey Eliette
Published: September 2014

The importance of coil cooling conditions on mechanical properties uniformity of HSLA and AHSS steel grades is discussed. It is namely shown that hot rolled coil under conventional industrial production can be cooled non-uniformly. That is why to predict correctly the final steel microstructure and mechanical properties of hot-rolled products an accurate description of not only run-out table condition but also of coil cooling should be done. Two solutions to provide accurate description of coil cooling were tested. First one is to use 2D finite element (FE) thermal model. When coupled with the ArcelorMittal metallurgical model to predict hot-rolled microstructure and properties (TACSI) it matches well the industrial data within +/-15-20MPa both for the tensile and yield strength. However, this approach is recognized to be heavy and time consuming. A second solution, a new 2D coil cooling simplified model incorporated in TACSI model, proved to be quite efficient, as it leads to performances similar to the more detailed first solution. Moreover, it is able to compute the coupling between the thermal evolution of the hot band and the kinetics of phase transformation during coil coiling and cooling, and will enable a better evaluation of the final mechanical properties especially for the grades for which the phase transformation is not completed before hot band coiling.
Process of Ontology Construction of Rolling Metal Sheets Industrial Process
Authors: Regulski Krzysztof , Rojek Gabriel , Kusiak Jan
Published: September 2014

The article presents assumptions and the process of construction of an ontology for the knowledge base that concerns industrial processes of metal sheets rolling including heat treatment operations. Creating of an ontology enables to build a knowledge base, which can be understood by both computers and engineers. Such a knowledge base can be used afterwards by intelligent computer techniques helping in solving of encountered problems during production process. The built ontology should be relevant to the nature of the rolling process – it has to take into account sequence of roll passes of the whole rolling process including all control parameters for each pass (e.g. the thickness before and after the pass, time of pass, temperature). Presented process of the construction of the ontology follows an ontology development cycle that should ensure relevance for industrial use of the ontology. The built ontology in the domain of industrial rolling should enable building knowledge base that concerns considered industrial process. One of possibilities is using of the elaborated ontology at construction of an advisory system that supports design of rolling process for a new product, which can be similar to some products made in the past. Other possibilities of utilization of the ontology can be seen in production scheduling or estimation of production costs.
Process Planning of Gear Rolling with the Finite Element Method
Authors: Khodaee Alireza , Melander Arne
Published: September 2014

Gear rolling is a new gear manufacturing process which can partly replace traditional gear milling processes. High gear wheels with modules of 4mm up to 6mm are of interest to truck manufacturing. The process is of interest since it involves no material removal and since it has the potential to give good performance of the gear wheels. The process must be adopted for the large plastic deformations which occur for gear rolling with large modules. In this paper special emphasis will be put to loads and torques during the gear rolling process of gear wheels with large modulus.
The FE method will be used to model the plastic deformation process to fully form a gear wheel with the gear rolling method. The radial and axial loads and the torques in this process are predicted. The loads of the process are high compared to the situation for small gear wheels so simulation of load level is essential for the design of rolling machines for high gears.
Topology Optimization of Geometrically Non-Linear Structures Using Iso-XFEM Method
Authors: Abdi M. , Ashcroft I. , Wildman Ricky D.
Published: September 2014

Iso-XFEM is an evolutionary-based topology optimization method which couples the extended finite element method (X-FEM) with an isoline/isosurface optimization approach, enabling a smooth and accurate representation of the design boundary in a fixed-grid finite element mesh. This paper investigates the application of the Iso-XFEM method to the topology optimization of structures which experience large deformation. The total Lagrangian formulation of the finite element method is employed to model the geometrically non-linear behaviour and equilibrium is found by implementing the Newton-Raphson method in each evolution. A cantilever beam is considered as a test case and the Iso-XFEM solutions obtained from linear and non-linear designs are compared with bi-directional evolutionary structural optimization (BESO) solutions.
Experimental Evaluation of Fatigue Resistance of ETG®88 and C45+C Steels Considering Stress Concentrators and Scale Factor
Authors: Černý Ivo , Mikulová Dagmar
Published: September 2014

The paper contains results of an experimental evaluation of fatigue properties of two steel types used for shaft manufacture, namely rather conventional, medium carbon high quality C45+C steel and quite modern low alloy ETG®88 steel, recently developed with the aim to reduce overall manufacture cycle costs together with maintenance of high mechanical and fatigue properties. Actual critical fatigue damage modes of shafts, namely at stress concentrators of shaft shoulders, was experimentally modeled by small and quite large notched specimens loaded by rotating bending. ETG®88 steel was characteristic by somewhat higher fatigue resistance, but higher scatter of results. Differences are discussed considering chemical composition, microstructure and results of simple analyses of fatigue fracture surfaces.
Fatigue Crack Propagation in Hydrogen Gas in Low Alloyed Steel
Authors: Sarrazin-Baudoux Christine , Gardin Catherine , Tran V.X. , Pham T.H. , Petit Jean
Published: September 2014

This paper deals with fatigue crack propagation under 4 bar hydrogen atmosphere in low alloyed steel (3.5Ni-1.5Cr-0.5Mo-V) used for turbine generator of nuclear plant. The tests are conducted in the same way in ambient air and high vacuum on CT specimens and the fatigue crack growth rate specially investigated in the near threshold range is plotted with respect to the applied stress intensity factor. It is shown that the propagation under hydrogen atmosphere is similar to that obtained in air up to a Kmax value of 16,5 MPam1/2 with increased growth rate compared to that in high vacuum leading to a threshold value lower that in vacuum, this effect being related to residual water vapor. For Kmax higher than 16,5 MPam1/2, much faster growth rates under hydrogen atmosphere becomes are associated to an intergranular propagation mechanism induced by an hydrogen effect. The results are discussed on the basis of available models.
Influence of the V-Notch Opening Angle on Critical Applied Force Values for the Crack Initiation from the Sharp V-Notch
Authors: Štegnerová Kateřina , Náhlík Luboš , Hutař Pavel
Published: September 2014

The aim of this paper is to estimate a value of the critical applied force for a crack initiation from the sharp V-notch tip. The classical approach of the linear elastic fracture mechanics (LELM) was generalized, because the stress singularity exponent differs from 0.5 in studied case. The value of the stress singularity exponent depends on the V-notch opening angle. The finite element method was used for a determination of stress distribution in the vicinity of the sharp V-notch tip and for the estimation of the generalized stress intensity factor depending on the V-notch opening angle. Critical value of generalized stress intensity factor was obtained by using stability criterion based on the tangential stress component averaged over a critical distance d from the V-notch tip. Calculated values of the critical applied force were compared with experimental data taken from the literature.
The Importance of Micro-Crack Evolution under Oxidation/Creep Conditions in Component Failure Life Predictions
Authors: Mehmanparast Ali , Nikbin Kamran
Published: September 2014

The oxidation, environmental corrosion and creep damage are limiting factors in the life assessment of engineering components operating at elevated temperatures. Experimental observations have shown that environmental effects (i.e. oxidation) during components operation time can harden the material [1] and lead to evolution of damage in the form of surface cracks (see Figure 1). The regions subjected to environmental damage which show higher hardness are structurally weaker and more brittle. When components operate in the creep regime, the initiated micro cracks may lead to accelerated creep crack growth in the material. The aim of this paper is to highlight the importance of oxidation effects and microcracks on creep in component life assessments.
Fracture in the Single Cantilever Beam Test with Large Scale Bridging
Authors: Budzik Michal K. , Jensen Henrik M. , Jumel Julien
Published: September 2014

A single cantilever beam test was performed on joints constituted from unidirectional carbon fiber composite flexible beam bonded to a rigid polyamide/aluminium block. The loading was following a constant separation rate rule, for which steady-state fracture energy can be obtained. In addition to the standard resistance curve we have investigated, using backface strain monitoring technique, fiber bridging effect on load distribution in the vicinity of the crack front. A big impact of the fiber bridging on the overall R-curve behaviour was confirmed with local non self-consistency of the crack propagation. The results are backed up analytically.
High Speed Fracture Phenomena by Underwater Shockwave of Explosive Energy and Large Current Pulse in Glass Container
Authors: Honda Seidai , Sakamoto Hidetoshi , Ohbuchi Yoshifumi , Kawabe Shinjiro , Itoh Shigeru , Nakamura Yasunori
Published: September 2014

Recently, many countries are promoting the collection, the reproduction and the use of consumer goods；aluminum cans, PET bottles, and so on. On the other hand, the reproduction of the glass bottles is not so active excluding use as a returnable bottle, because the recycle cost is high. The glass bottles are fractured by the small fragment for reproduction. The small crushing fragments are called ‘Cullet’. The cullet is melted and molded again as glassware. The surface area is enlarged by making the bottle cullet, and it is possible to melt these efficiently. As a result, it becomes possible to shorten the time to melt the glass bottle and reduce a consumption of the fuel oil.
The reasons with not active recycling of the glass bottle are that large-scale crushing equipment is required and it takes a lot of time and cost. This study proposed a new recycling technique for fracturing the glass bottle by using an underwater shockwave by explosive and electric pulse. The shock wave pressures produced by the explosive and the electric pulse energy were measured and the optimum crushing conditions were discussed.
Wedge Splitting Test of Foam Concrete Specimens: Calibration Curves
Authors: Seitl Stanislav , Merta Ildikó , Veselý Václav
Published: September 2014

In the present paper, the well-known wedge splitting test is applied on specimens made from foam concrete. In the case of this material the whole test specimens cannot be made from foam concrete but the rectangular groove, needed for the load transmission pieces, has to be made of stiffer material (typically marble). K-calibration (B1) and T-stress (B2) calibration curves for such specimens are introduced. The objective was to compare and discuss the calibration curves for the homogeneous case, the case with marble parts and the case with marble parts considering the glued marble/foam concrete interface
Round Timber Bolted Joints with Steel Plates under Static and Cyclic Loading
Authors: Lokaj Antonín
Published: September 2014

Aim of this paper is in presentation of results of static and dynamic tests of round timber bolted connections with slotted – in steel plates. Round timber joints static tests in tension were made on pressure machine. Round timber joints multicyclic (fatigue) tests in tension were made on pulsator. Results of laboratory tests have been statistically evaluated and completed by graphical records of deformation response on loading. Samples of round timber bolt connections with slotted - in steel plates were tested for carrying capacity and deformation of a single tension – up to the failure of connection.
Thermal Cycling Life of Porous Ceramic Coatings Subjected to Thermal Gradient and Coolant Pressure
Authors: Arai Masayuki , Hayashi T. , Suidzu T.
Published: September 2014

A transpiration cooling system for gas turbine applications has significant benefit to reduce the amount of cooling air and to increase cooling efficiency. We had developed a porous ceramic coating deposited by plasma spraying process, which can infiltrate cooling gas, and examined about those mechanical properties. In this study, thermal cycling life of this porous ceramic coating is revealed in order to apply this technology to advanced gas turbine blade in practical use. The thermal cycling test is conducted by using the hand-made device which can heat cyclically up and down around the surface of the porous coating while infiltrating cooling gas. The number of thermal cycles up to reach the coating delamination is related with maximum exposed temperature and pressure of the cooling gas as the test condition, consequently.
Review of FE-Based Fatigue Evaluation Methods for the Rib to Floorbeam Welds in Orthotropic Bridge Decks
Authors: de Corte Wouter , Jansseune Arne
Published: September 2014

Complex welded structures such as bridges are very often designed with the help of FE analysis. However, one should remain cautious when using such an analysis, since the results are mesh sensitive, with especially the mesh density and the element type influencing the results. In addition, these results are in most cases retrieved in hot spot areas with high stress gradients, where the maximum stress even cannot be correctly determined with linear elastic finite element analysis. For that reason, a stress evaluation method is required to obtain relevant stress levels that can be directly related to fatigue detailing. The most complete set of stress evaluation recommendations is given in the Recommendations for Fatigue Design of Welded Joints and Components from the International Institute of Welding. Nevertheless, several authors have recently commented on the difficulties regarding the application of these methods for the rib to floorbeam welds in orthotropic bridge decks. This paper provides findings for this type of connections based on both shell and solid model analysis and relates these findings to work from other authors.
Meshless Approaches for Fracture with Nonlocal Elasticity
Authors: Wen Pi Hua , Huang X.J. , Aliabadi M.H.
Published: September 2014

The fracture analysis for two-dimensional nonlocal elasticity is presented by the numerical approaches i.e. the Local Integral Equation Method (LIEM). Based on the Eringen’s model, the nonlocal stresses at the crack tip are regular. Numerical simulation by LIEM is proposed for the nonlocal elasticity fracture problems. A rectangular cracked plate subjected to tensile load is observed numerically to demonstrate the convergence and accuracy of LIEM.
Investigation of the Cracking Behaviors by Indentation Based on an In Situ Observation
Authors: Yamazaki Yasuhiro
Published: September 2014

In this paper, an in-situ measurement of crack size as a function of applied indentation load during indentation test was conducted. To perform the in-situ measurement, an instrumented indentation test machine with the in-situ observation system was developed and used. The joints of transparent ceramics by diffusion bonding were prepared as the specimen used in this study. The indentations were performed at the interface of the joints, and in the monolithic transparent ceramics by means of the instrumented indenter with the in-situ observation system. The relationship between crack shape and indentation load, as well as, the effect of the indenter shape on it were discussed.
Point Load Effect Determination for Different Pressure Pipe SDR Series
Authors: Majer Zdeněk , Ševčík Martin , Náhlík Luboš , Hutař Pavel
Published: September 2014

In the paper the polymer pipes loaded by internal pressure with additional point load on the external surface are studied using numerical methods. It is shown that the additional external loading can significantly influence residual lifetime of the pressured pipe. In this study the effect of the pipe geometry is considered. The shape of the propagating crack is estimated based on a special algorithm and the stress intensity factor is evaluated by direct method. The relation between crack size and a geometric function YasYas for specific material and geometrical properties is found. The results of this paper should contribute to better understanding of the real pipe behavior and to prevent unexpected failure of the pressured pipe system due to non-homogenous distribution of the soil load.
The Relationship of Compressive Strength and Tensile Strength of High Performance Concrete
Authors: Kim Jeong Eun , Park Wan Shin , Yun Song Hui , Jang Yong Il , Yun Hyun Do , Kim Sun Woong , Kim Do Gyum
Published: September 2014

Fly ash and blast furnace slag dumped not only pollutes environment, but also consumes landfills. With the aim of sustainable development, the isolated contribution of fly ash and blast furnace slag in concrete to the mechanical properties of frame concrete is investigated. An experimental study is conducted to investigate mechanical properties of high performance concrete. Test variables are the replacement levels for FA series (10%, 20% and 30%) and for BS series (10%, 30%, 50% and 70%) in place of part of cement. Compressive, splitting tensile strength, modulus of elasticity and flexural strength tests were carried out to evaluate the mechanical properties for up to 7days and 28 days. The mechanical properties of high performance concrete compared with predicted values by ACI 318-02 Code, EC 2-02, JSCE Code, KCI Code and proposed Eq.
Investigation on Compressive Strength after Impact Damage of Carbon/Epoxy Laminate
Authors: Park Hyun Bum
Published: September 2014

Development of the Korean small scale aircraft (KC-100) has been carried out by KAI (Korea Aerospace Industry Ltd.) for the BASA(Bilateral Aviation Safety Agreement) program with FAA. The KC-100 aircraft adopted the environmental friendly whole composite structure concept due to low fuel consumption owing to its light weight. However the composite structure has a disadvantage. They are very weak against impact damage due to FOD (Foreign Object Damage). This study is to investigate the residual compressive strength of the carbon/epoxy fabric and UD (Unidirectional prepreg tape) laminate due to impact damages. This residual compressive strength test follows fully the ASTM standard test procedure. Experimental investigation results reveal the residual strengths and the damage mode and size of impact damage specimens. Through these tests, it is found that the residual strength of the impact damage specimens is greatly reduced in comparison to the undamaged specimens depending on increase of both the indentation depth and the impact energy. The size and shape of damage zone greatly affects the reduction of the compressive strength.
A Development of Innovative Slip-Form System for Concrete Pylons
Authors: Yoon Hye Jin , Chin Won Jong , Kim Hee Seok , Kim Young Jin
Published: September 2014

This study developed the innovative slip-form system for the construction of concrete pylons. The slip-up time of the slip-form is determined by estimating the compressive strength from surface wave velocity by the device attached to the slip form. GPS and tiltmeter are applied to secure the precise construction quality. The design of the slip form is verified in advance by BIM to validate its applicability through virtual assembly and construction. A slip form system is fabricated and mockup test is conducted to verify the performances of the developed techniques through the construction of a 10 m-high pylon with hollow section.
Contact State Investigation of a Three-Point Bend Specimen Using Numerical Methods
Authors: Javed Raja Ahsan , Zhu Shi Fan , Guo Chun Huan , Jiang Feng Chun
Published: September 2014

At higher loading rates, modified Hopkinson pressure bar apparatus is widely used to determine the dynamic fracture toughness of the engineering materials. For accurate measurement of the dynamic fracture properties, we need to thoroughly understand the contact situation of the three-point bend specimen, with the loading apparatus. Strong inertial effects complicate the specimen’s contact situation with impactor and supports. In this work, ANSYS software is used for modeling and analysis of a modified Hopkinson pressure bar loaded fracture experimental setup. Analysis of stress contours and nodal displacements are used for the examination of specimen contact state. The results indicate that during loading in the elastic range, the specimen remains in contact with the loading apparatus as this is previously proved experimentally.