bluuebunny/crossref_metadata_2025 huggingface dataset:
A Finite Element Based Approach for the Accurate Determination of the Shear Behaviour of Textiles with the Picture-Frame Shear Test
Authors: Döbrich Oliver , Gereke Thomas , Cherif Chokri
Published: June 2013

Picture frame shear tests are state of the art for determining the shear force vs. shear angle behaviour for in-plane deformation of most technical textiles, such as woven fabrics. Many publications describe this test and the used picture frames. Benchmark tests showed that the measured shearing behaviour for one sample depends on the picture frame used. The shearing rigidity of most textiles is very small compared to the in-plane tensile stiffness, so slight imperfections on the experimental setup have a significant effect on the measured results. During the picture frame test, wrinkles may form on the sample surface during the motion of the picture frame above a critical shear angle. These wrinkles can be described as local fabric buckling. If forming of wrinkles leads to a lower level of internal energy compared to a further shearing of the fabric, local wrinkles occur due to the principle of least action. Because of this effect, the measured shear force above the first formation of wrinkles is inaccurate for describing the exact shearing behaviour of textiles. Another possibility for measuring the shear force vs. shear angle behaviour is the bias-extension test. Here, higher shear angles can be achieved without the formation of wrinkles. Both methods are compared in this paper for different textile samples. The relationship of the shear angle and the applied shear force is an important mechanical value and one of the most important input parameter in numerical drape simulations. The analysis of wrinkles, which occur during textile draping, demands exact input parameters for the simulation. Most important for the drape simulation of technical high-performance textiles are accurate values for the bending and shear behaviours. This paper presents simulation results of the wrinkling during a picture frame shear test. Results show that the input parameter for the shear rigidity delivered by the picture frame shear test do not exactly reproduce the formed wrinkles and are, therefore, not suitable for an exact drape simulation. The underestimation of the shear force vs. shear angle behaviour will be shown with a finite element simulation model. The adaptation of the picture-frame and bias-extension parameters for a proper use in numerical drape simulations are examined.
Growth and Closure of Voids in Metals at Negative Stress Triaxialities
Authors: Zapara Maksim , Tutyshkin Nikolai , Müller Wolfgang H.
Published: June 2013

Damage of metals subjected to large plastic deformations typical for forming processes is mainly governed by void nucleation, growth and coalescence. An opposite process may occur in deformation processes with negative stress triaxialities: the closure of strain-induced defects under large hydrostatic pressure. Understanding the mechanisms of damage growth and healing under plastic deformation of metals is still an urgent problem. In order to solve it a theoretical framework for anisotropic ductile damage based on a physically motivated concept for changes in the void volume and shape was recently developed [6]. Strain-induced damage was experimentally determined during uniaxial compression of cylindrical metallic specimens with artificial voids represented by fully-trough drilled holes. It was revealed that the governing physical mechanism of failure is a change in void shapes due to compressive stresses at low negative stress triaxialities in contrast to the growth of voids volume due to high positive stress triaxialities in the processes with dominating tensile stresses. The tensorial model presented in [6] proved to be able to describe kinetics of ductile damage, failure as the ultimate damage, and the closure of voids at negative stress triaxialities.
Correlation of Tensile Test Parameters and Bendability of High-Strength Steels
Authors: Lämsä Janne , Väisänen Anu , Heikkala Jouko , Järvenpää Antti
Published: June 2013

The aim of the study was to investigate correlation between bendability and tensile properties of high-strength steels. Strength and elongation in tensile test have traditionally been basic values in evaluating bending properties. Advanced high-strength (AHS) steels often have tendency for strain localization, causing risk of fractures and impairing the shape of the bend. Practice has shown that tensile test results, indicating bendability well, are not sufficiently accurate when using AHS steels. Since tensile test is a fast, simple and cheap testing method, it would be beneficial to rework it to suit better for predicting of bendability. In this study, the usability of tensile test results to predict failures in bending AHS steels has been investigated. The most common failures and failure mechanisms in bending are also presented. Test materials used were 6 mm thick AHS wear-resistant, protection and structural steels with good and poor bending properties. Minimum bending radii were determined and then compared with ten-sile test results to estimate the correlation. Conventional tensile test results, fracture surfaces and necking through width and thickness were analyzed. Correlation coefficient for measured tension properties and minimum bending radius was calculated. Results showed that in tensile test, have the best correlation with minimum bending radius with necking through the thickness and actual strain in necking area.
Comparison of Different Constitutive Models in Sheet Metal Forming
Authors: Uçan Meriç , Darendeliler Haluk
Published: June 2013

The effects of different constitutive models in sheet metal forming are investigated by considering the cylindrical and square cup drawing and V-bending processes. Numerical analyses are performed by employing eight different constitutive models. These are elastic plastic constitutive model with isotropic hardening, elastic plastic constitutive model with kinematic hardening, elastic plastic constitutive model with combined hardening, power law isotropic plasticity, piecewise linear isotropic plasticity, three-parameter Barlat, anisotropic plasticity and transversely anisotropic elastic plastic models. The simulations are performed for three different materials, St12 steel, Al-5182 aluminum and stainless steel 409 Ni, by using a commercial finite element code. A number of experiments are carried out and the experimental and analytical results are utilized to evaluate the results of simulations.
Control System Algorithm for the Prediction of Sprinback in Air Bending
Authors: Longo Michela , Maccarini Giancarlo
Published: June 2013

The phenomenon of springback, which is ruled by strain recovery after removal of forming loads, is of remarkable interest in air bending of metal sheets. In this process, the final angle is affected by a number of parameters related to both process geometry (sheet thickness, die and punch radii) and material properties (elastoplastic stress-strain law); because of this, punch stroke has to be calculated in a nontrivial way and a number of input parameters should be taken into account. In this work the study of total load as a function of displacement is used to collect information about material stress-strain law; using this approach, load data may be exploited to fine tune the mathematical description of the material and, finally, to improve springback prediction. A customized press brake able to measure both displacement and force during bending was fabricated for this purpose. The press brake is equipped with a control system algorithm able to collect material information directly during the initial stage of the bending process. These collected data are used to feed a model based on a FEM simulation and the model output is the final punch displacement suitable to obtained a specific bending angle after unloading. The program utilized for the simulation is Deform 2D. Preliminary tests were executed on metal sheets having different thickness.
Experimental and Numerical Studies of Edge Rounding Process in HSLA Steels Sheet Metal
Authors: Achouri Mohamed , Gildemyn Eric , Germain Guenael , dal Santo Philippe , Potiron Alain
Published: June 2013

Blanking of sheet-metal is an important forming process in the automotive industry for the manufacture of mechanical components. The final component shape, obtained at the end of bending or deep-drawing processes, often has sharp edges due to the blanking operation. Edge Rounding by Punching (E.R.P.) of safety components is necessary to avoid cutting the belt material. In addition to removing the sharp edges, the punching results in work hardening of the material in the rounded zones which results in an increase in the local resistance of the material. In this study, a High Strength Low Alloy steel (HSLA S500MC) is tested with the aim of analysing the residuals fields in the chaining of blanking and edge rounding processes. The mechanical behaviour of the sheet material is investigated by means of tensile tests and Vickers micro-hardness measurements. Numerical simulations are performed using a ductile damage criterion. The experimental residual stress fields are characterised and compared to numerical results, in view of predicting the in-service behaviour of the component. Specimens with rounded edges are compared to specimens that were not submitted to the rounding operation. It is shown that (E.R.P.) improves the component resistance, therefore justifying the use of this process in the manufacture of automotive safety components.
Simulation of IR Heating for Composite Stamping
Authors: El Bakali Abdelmagid , De Almeida Olivier , Bikard Jérôme , Villière Maxime , Schmidt Fabrice , Le Maoult Yannick , Dauphin Myriam
Published: June 2013

Composite stamping is a two steps process that includes an infrared heating oven in order to melt the composite sheets before forming. This study deals with the numerical simulation of the heating step of the process. The numerical model has been validated using three woven glass and carbon / PA6.6 composites provided by Solvay Rhodia. This type of simulation consists in solving the heat equation with a radiative flux that characterizes the interaction of the material with the IR heating. The model thus considers the IR properties of the material (emission and reflexion). Considering a homogeneous composite, the optical and thermal properties of sheets have been first measured. The material’s emissivity has been measured using a FTIR spectrometer from the reflective and transmitive spectra, by using the Kirchoff law and considering a Lambertian material. Three complementary measurement techniques were used to determine the thermal properties of the composites. Differential Scanning Calorimetry (DSC) measurements have been performed to identify the heat capacity of the composites. On another hand, a hot disc system (measurements performed at the LTN, France) has been used in transient conditions to determine the heat capacity and the thermal conductivity of the composites is all three directions. Finally, the in-plane thermal matrix of conductivity has also been measured by thermography by using an inverse method. The simulation of composites heating has been performed with Comsol MultiphysicsTM and the simulation procedure was validated by comparison with experimental results. The simulated IR oven is composed of 9 IR emittors provided by Toshiba Lighting Company that emit mainly in short IR wavelength (0.75-2µm). The emission properties of the tungsten filament were implemented in order to simulate the IR heating. Free convective heat transfer was also taken into account in the oven. In order to validate the model, an experimental set-up was instrumented with a calibrated IR pyrometer that measured the back side of the heated composite sheets. The experimental results confirm a low thermal gradient through composite thickness, in particular for carbon-reinforced composite. This result is consistent with the low Biot number of the composites. Moreover, experimental and simulated temperatures are in good agreement with an error lower than 15% in the entire heating stage from room to melt temperature.
Uniform Cooling and Part Warpage Reduction in Injection Molding Thanks to the Design of an Effective Cooling System
Authors: Agazzi Alban , Sobotka Vincent , Le Goff Ronan , Jarny Yvon
Published: June 2013

In this paper, a new methodology for the design of effective cooling system of thermoplastic injection tools is proposed. It is named MCOOL® for Morpho Cooling. It allows the design of the cooling channels in the mold with no a priori on the number, the size, the shape of the channels and the temperature of the coolant before performing the optimization. Numerical and experimental results obtained on a mold manufactured thanks to this methodology are compared with those coming from a conventional design. The criteria used to discriminate the results are based on the uniformity of the temperature field in the molded part and on the final warpage of the part.
Multi Criteria Adaptive Meshing for Polymers Processing in Rem3D®
Authors: Francois Guillaume , Ville Laurence , Silva Luisa , Vincent Michel
Published: June 2013

In this paper, we present an innovative adaptive meshing method developed in the injection simulation software Rem3D®. This method generates a full optimized mesh with a high accuracy for strong flow/heat/rheology coupling as well for complex interface evolutions, and with a reduced number of nodes. Results show good agreement with analytical solutions, as well as for full industrial process experiments.
Multi-Response Parameters Optimisation for Energy-Efficient Injection Moulding Process via Dynamic Shainin DOE Method
Authors: Yin Kam Hoe , Choo Hui Leng , Halim Dunant , Rudd Chris
Published: June 2013

Process parameters optimisation has been identified as a potential approach to realise a greener injection moulding process. However, reduction in the process energy consumption does not necessarily imply a good part quality. An effective multi-response optimisation process can be demanding and often relies on extensive operational experience from human operators. Therefore, this research focuses on an attempt to develop a more user-friendly approach which could simultaneously deal with the requirements of energy efficiency and part quality. This research proposes a novel approach using a dynamic Shainin Design of Experiment (DOE) methodology to determine an optimal combination of process parameters used in the injection moulding process. The Shainin DOE method is adopted to pinpoint the most important factors on energy consumption and the targeted part quality whereas the ‘dynamic’ term refers to the signal-response system. The effectiveness of the proposed approach was illustrated by investigating the influence of various dominant parameters on the specific energy consumption (SEC) and the Charpy impact strength (CIS) of polypropylene (PP) material after being injection-moulded into impact test specimens. From the experimental results, barrel temperature was identified as the signal factor while mould temperature and cooling time were used as control factors in the full factorial experiments. Then, response function modelling (RFM) was built to characterise the signal-response relationship as a function of the control factors. Finally, RFM led to a trade-off solution where reducing part-to-part variation for CIS resulted in an increase of SEC. Therefore, the research outcomes have demonstrated that the proposed methodology can be practically applied at the factory shop floor to achieve different performance output targets specified by the customer or the manufacturer’s intent.
Analysis and Simulation of the Free-Stretch-Blow Process of PET
Authors: Nixon J. , Yan S. , MENARY Gary
Published: June 2013

This paper is concerned with understanding the behaviour of Polyethylene Terephthalate (PET) in the injection stretch blow moulding (ISBM) process where it is typically bi-axially stretched to form bottles for the packaging industry. Preforms which have been pre sprayed with a pattern and heated in an oil bath have been stretched and blown in free air using a lab scale ISBM machine whilst being monitored via high speed video. The images have subsequently been analysed using a digital image correlation system (VIC 3D). The results have been used to validate appropriate simulations of the free-blow process using ABAQUS®/Explicit FEA with a suitable viscoelastic material model, along with experimental process data obtained using an instrumented stretch rod.
Design of an Experimental Device for Biaxial Tension Tests Used in a Uniaxial Test Machine
Authors: Tsai Heng Kuang , Lin Yi Wei , Chen Fuh Kuo , Wang Shi Wei
Published: June 2013

In the present study, a set of novel clamping apparatus that could deliver biaxial stretching motions with the use of a uniaxial tensile testing machine was designed and manufactured. The conversion of uniaxial motion into biaxial stretching motions is achieved by a sliding mechanism that consists of two blocks sliding in two mutually perpendicular grooves, respectively. During the biaxial tension test, a cross-shaped specimen sitting in the grooves are stretched by the two blocks driven by a pulling rod. The different stress ratios could be obtained by adjusting the groove surface shape and the lengths of specimen wings. In the clamping apparatus design stage, the finite element simulations were performed to examine the validity of the sliding mechanism and the frictional force generated between the sliding blocks and the grooves. The coefficient of friction was determined afterwards from the comparison of the pulling forces obtained in the experiments with those calculated by the finite element simulations. In addition, the optimum geometry and dimension of the cross-shaped specimen used in the biaxial tension tests were investigated by the finite element analysis as well. The slotted specimen proposed by Kuwabara et al. was taken as the basic design. A sufficiently large area in the central region of specimen where the principal stress directions aligned with the groove direction was obtained for gluing the strain gauges to the specimen for the biaxial stretching tests. The number of slots and associated slot widths were also examined to optimize the shape of the specimens. The proposed clamping apparatus was manufactured and the biaxial tension tests were conducted with cross-shaped specimens made of advanced high strength steel sheets. The validity of the designed clamping apparatus used for biaxial tension tests was confirmed and the congruence of various yield criteria applied to the advanced high strength steel sheets subjected to biaxial stress states was discussed.
Primary Research on Jet ECM Processing of Difficult to Cut Materials
Authors: Lipiec Piotr , Wyszyński Dominik , Skoczypiec Sebastian
Published: June 2013

Unconventional production techniques became interesting and promising part of manufacturing methods. They provide complementary, to traditional loss methods, solutions enabling use of high - performance engineering materials for construction of machinery and industrial equipment. By using properly selected methods or their hybrids difficult to cut materials as steel, alloys, sintered materials and composites can be processed. Among the wide variety of unconventional methods of materials forming, particular attention should be given to electrochemical machining, which has been successfully used in various industries. This fact proves attractiveness and versatility of ECM. The method could be used on large scale and many variations was developed as each application requires an individual approach and has own requirements. One of the least known and described type of electrochemical machining is jet ECM where the electrolyte jet stream acts as a tool. In this kind of machining, the part is shaped only in the area where the electrolyte jet strikes the surface. This is due to the fact that the current density distribution is located just below the stream. In the area around the jet hitting the work piece thin electrolyte layer is formed. Thickness of that layer is growing rapidly. Since the electrolyte jet machining is an electrochemical process, the machined surface has all the benefits of ECM. There is no burrs and low temperature of the process prevents appearance of cracks and there is no heat-affected zone. Electrolyte jet machining can be used as well as in macro and micro drilling, turning, texturing, and electroplating. The process can be controlled by proper selection of such parameters as time, the current density and the diameter of the jet. Jet ECM can be used not only for material removal, but also for coloration (passivation) by means of anodic dissolution. 3D shaping of elements is also possible by controlling the current and the velocity of the electrolyte stream. In addition, by changing the polarity of the applied voltage it is possible to use this method in broadly considered electroplating. The paper presents results of the initial research on jet electrochemical machining (jet ECM) of acid proof steel and tungsten carbide. The material processing was carried in two ways – drilling holes and shaping grooves. Shaping was realized in milling and face turning regime. The influence of the two basic process parameters voltage and pressure was examined. In order to get rough information about the jet ECM process experiment planning method was applied. Obtained results enable planning of the further extended research.
Machining of External Cylindrical Surfaces on a RAM Electrical Discharge Machine
Authors: Slătineanu Laurenţiu , Coteaţă Margareta , Besliu Irina , Gherman Lorelei , Dodun Oana
Published: June 2013

As other nonconventional machining methods, the electrical discharge machining is applied when the workpieces materials are difficult to be machined by classical machining methods or the surfaces could not be obtained in efficient conditions by classical machining methods. Such a situation could appear, for example, when test pieces must be separated from materials whose machining by classical methods is difficult. Taking into consideration the necessity to detach a cylindrical test piece from a workpiece made of a high resistance metallic alloy, the problem of using the electrical discharge machining was formulated. An initial experimental test by using the common work motion of the tool electrode from up to down highlighted high shape errors, due to the accumulation in the work zone of the particles detached from the workpiece and from the tool electrode, as a consequence of electrical discharge machining process. A second set of experiments were developed, placing the test piece over the electrode tool and ensuring a work motion of workpiece from up to down; in this situation, a diminishing of the shape error was noticed. The second set of experiments highlighted a relatively reduced conicalness of the machined surface and a low decrease of the machining speed. as the penetration depth of the tool electrode in the workpiece increases, too.
Rapid Manufacturing of Shaped Die and Draw Punch Tools for Presses
Authors: Kananen Markku , Hietala Mikko , Mäntyjärvi Kari
Published: June 2013

Traditionally forming tools for a press are machined with a CNC-machine. This is quite time consuming - calculating tool tracks, selecting cutting tools, cutting blanks, design fixation and finally machining - especially for a small batch of parts. One alternative method is to cut a die and a draw punch tools from a blank sheet and bunching the plates. Clamping plates together is fast and easy to implement by using for example studs and bars with a certain tolerance to ensure alignment. A laser, a water jet or a plasma cutter can be used for cutting plates. Especially the laser and the water jet cutting are precise methods giving a fine surface quality without a need for fine-tuning. The method saves material compared with machining because a die and a punch could be cut at the same time from a blank sheet as compatible pair as well as the needed amount of plates could be estimated depending of the length of a pressed product. University of Oulu, Oulu Southern institute, Future Manufacturing Technology -group has manufactured several forming tools within this technique and found it extremely suitable for experimenting different solutions and options fast. Furthermore, the method is likely to help especially SMEs in their R&D-phase by lowering production costs in a cost-efficiency way.
Determination of Flow Curve Using Bulge Test and Calibration of Damage for Ito-Goya Models
Authors: Martins Bruno , Santos Abel D. , Teixeira Pedro , Ito K. , Mori N.
Published: June 2013

The standard uniaxial tensile test is the widely accepted method to obtain relevant properties of mechanical characterization of sheet metal materials. However the range of strain obtained from tensile test is limited. The bulge test is an alternative to obtain ranges of deformation, higher than tensile test, thus permitting a better characterization for material behaviour. This paper presents a sensitivity analysis for some influencing variables used in bulge measurements, thus giving some guidelines for the evaluation of the stress-strain curve from experimental results using a developed experimental mechanical system. Additionally, using bulge test up to fracture shall give material information regarding damage, which in turn may be used to evaluate and calibrate damage models. A methodology is presented to be used for evaluation and calibration of Ito-Goya damage model of damage prediction.
Investigation of Residual Stresses Induced during the Selective Laser Melting Process
Authors: van Belle Laurent , Vansteenkiste Guillaume , Boyer Jean Claude
Published: June 2013

The selective laser melting process (SLM), belonging to the family of additive manufacturing processes, can create complex geometry parts from a CAD file. Previously, only prototypes were created by SLM, but now this process is used to manufacture quickly and directly functional parts. For example, in the PEP (Pôle Européen de la Plasturgie), this process is used to fabricate tooling parts or injection molds with cooling channels that can’t be obtained by conventional routes. During the process, the laser beam generates violent heating and cooling cycles in the material inducing important thermal gradients in the consolidated part. The cyclic thermal expansions and contractions exceeding the maximum elastic strain of the material induce heterogeneous plastic strains and generate internal stresses the level of which can reaches the yield stress of the material and cracks may appear during the process. This paper deals with the measurement and analysis of residual stresses during the selective laser melting of a simple part in maraging steel. The objective of this study is the analysis of experimental results to validate the numerical model previously presented in [1]. Some authors have investigated the residual stresses produced in SLM parts using different experimental measurement methods such as the incremental hole drilling method in [2], the layer removal method see in [3] and [4] or the non-destructive method, by neutron diffraction in [5]. A new method is proposed to evaluate the residual stresses induced during the SLM process, a rosette is fixed on the bottom face of the support. The residual stresses in the created part are calculated from strain and temperature variations when the fused layer is consolidating during the cooling between two layers. Process parameters like the powder thickness or the time cooling between successive layers are studied in this paper. [1] L. Van Belle, G. Vansteenkiste, J.C. Boyer, Comparisons of numerical modeling of the selective laser melting, Key Engineering Materials Vols. 504-506 (2012) pp 1067-1072 [2] C. Casavola, S.L. Campanelli, C. Pappalettere, Experimental analysis of residual stresses in the selective laser melting process, Proceedings of the XIth International Congress and Exposition, June 2-5, 2008 Orlando, Florida USA [3] M. Shiomi, K. Osakada, K. Nakamura, T. Yamashita, F. Abe, Residual stress within metallic model made by selective laser melting process, CIRP Annals - Manufacturing Technology, Vol. 53, No. 1. (2004), pp. 195-198 [4] T. Furumoto, T. Ueda, M.S. Abdul Aziz, A. Hosokawa and R. Tanaka, Study on reduction of residual stress induced during rapid tooling process, influence of heating conditions on residual stress, Key Engineering Materials Vols. 447-448 (2010) pp 785-789 [5] M. Zaeh, G. Branner, Investigation on residual stresses and deformation in selective laser melting, Production Engineering, Volume 4, Number 1 (2010)
Ti-6Al-4V Cutting by 100W Fibre Laser in Both CW and Modulated Regime
Authors: Astarita Antonello , Genna Silvio , Leone C. , Minutolo Fabrizio Memola Capece , Paradiso Valentino , Squillace Antonino
Published: June 2013

Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic [1]. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). Cutting of titanium sheets is one of the primary requirements in the fabrication of most of the components. Laser cutting offers several advantages over conventional cutting methods. It includes narrow kerf width (minimum material lost), straight cut edges, low roughness of cut surfaces, minimum metallurgical and surface distortions, easy integration with computer numerically controlled (CNC) machines for cutting complex profiles and importantly non-contact nature of the process (suitable for cutting in hostile environments and in areas with limited access) [2]. However, due to very limited literature available on laser cutting of titanium, it is very difficult to predict the cut surface quality and optimum process parameters for laser cutting, especially when dross-free cuts are required. Laser cutting of titanium and titanium alloys needs to be carried out with an inert gas, this due to the high reactivity of the titanium with the oxygen at high temperatures [3]. However when the available power is limited, as in the present case, the use of a reactive gas (air) can help to achieve cutting speed value reasonable for industrial applications. The aim of this work is to study the cutting of Ti-6Al-4V rolled sheets 1 mm in thickness, by means of a 100 W fibre laser, (SPI-Red Power) working at wavelength  = 1090 nm. The maximum cutting speed were measured in both CW and pulsed regime at different mean power and different duration. Furthermore, the kerf geometry and the heat affected zone (HAZ) were studied decreasing the cutting speed from the maximum to the 80 % of this values. The results obtained showed that both the power and the cutting speed influence the cutting kerf geometry and HAZ. In particular the synergy of power and speed, resulting roughly into the heat input, seems to rule the whole cutting process.
Novel Aerospace Architectures Made Possible by Forming Simulation
Authors: Zettler Joachim , van der Veen Sjoerd
Published: June 2013

In the aerospace industry lightweight design in combination with fast and reliable manufacturing processes are key components to defend the leading position in the worldwide competition. In this frame it is an overall goal to reduce the number of process steps in order to produce parts for an aircraft to its minimum. Integral design is one way to cope with this goal but on the other hand raises a lot of problems that may occur in manufacturing or final assembly. To be able to predict potential bottlenecks or drawbacks in certain designs, finite element simulation can be helpful. Especially if it’s an early design phase and new material concepts are taking into account, the virtual manufacturing, done by finite element simulations is the only way to predict real life behavior. In this paper we will focus on the use and benefit of finite element simulations in the early design phase of very huge integral parts of a next generation aircraft. The parts do belong to the nose fuselage structure and will be manufactured from a 100-150mm thick AlMgSc plate. Two different manufacturing routes will be covered by simulation. 1. Hot forming the plates at around 300°C and machining 2. Explosive forming of the plates and machining For both routes, a complete simulation chain from forming over springback to final machining is developed and presented in detail. Special care is taken on a fully automated workflow from one step to the other to allow an easy adaptation to other part geometries in the future. To ensure a high quality of the simulation results all process steps of the hot forming route are simulated with ABAQUS implicit and approved constitutive laws. The explosive forming manufacturing route is simulated using an Eulerian-Lagrange approach taken into account the various possibilities of detonation loading. To validate the simulation results to real measurements, a scaled down version of one of the parts is manufactured in reality and each process step is compared with the simulation result.
Experimental Evaluation of Innovative Tools for Ti-6Al-4V Turning
Authors: Strano Matteo , Albertelli Paolo , Chiappini Elio , Tirelli Stefano
Published: June 2013

Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds, with obvious negative consequences on the profitability of machining. An important amount of research activities has been done in order to increase productivity in titanium machining operations: high performance coatings and innovative technologies to improve inserts resistance to wear represent promising solutions. In this work, the cutting performance in Ti6Al4V rough turning of an innovative TiAlN coating obtained by Physical Vapor Deposition (PVD) magnetron sputtering and the effects of a Deep Cryogenic Treatment (DCT) have been experimentally investigated and a statistical analysis of the results has been performed. Typical commercially available inserts (TiAlN-AlCrO coated) have been used as a benchmark. Preliminary hardness and thermal conductivity measurements tests have been performed on the three types of tool to determine the differences caused by the different coatings and thermal treatment. The experiments have been conducted using a full factorial design in order to statistically evaluate, using ANOVA, the significance of the input factors on the process most interesting outputs. tool life and other variables of interest with different process parameters. The considered input factors are type of insert, cutting speed and feed rate. The analysed responses are average flank wear, surface roughness, cutting forces, coefficient of friction and chip morphology. The results show that even if friction coefficients are lower for standard tools, innovative inserts exhibit a higher resistance to wear. Taylor’s law parameters of PVD coated tools, with and without DCT have been determined, clearly showing that cryogenically treated tools present higher resistance at higher cutting speeds, mainly due to their superior hardness. In conclusion, it appears that relevant improvements of productivity or profitability of titanium turning can be obtained if an advanced PVD coating, deposited by magnetron sputtering is used on tungsten carbide inserts and if deep cryogenic of the inserts is performed afterwards.
Experimental Investigation on the Cutting Heat Distribution with Different Coating Structures Inserts
Authors: He Yun , Li Lin Ning , Li Cheng Yao , Chen Long , Yue Xin
Published: June 2013

It is known that carbide inserts have better cutting performance. Coating structures will affect the inserts’ life and the cutting heat distribution on chip, workpiece and insert. In this manuscript, three kinds of turning inserts with different coating structures were used to test under the same cutting conditions and inserts geometry for cutting AISI1045 quenched and tempered steel. These coating structures are CVD-TiCN/Al2O3/TiN, PVD- TiAlN, CVD-TiCN/Al2O3. The chip temperature and the cutting force are measured by the infrared thermal image and cutting force instrument. Total heat includes the chip heat and the dissipated heat which is calculated using the formula deduced. The coefficient η of cutting heat flow of chip and the influence of coating structures on cutting heat distribution are investigated. The results show that the three kinds of turning insert with different coating structures have different effect on cutting heat distribution and the PVD- TiAlN coating performs better for taking away more heat on chip when turning AISI1045 quenched and tempered steel.
Numerical Simulation of Machining Operations on Flexible Parts
Authors: Rivière-Lorphèvre Edouard , Filippi Enrico , Dehombreux Pierre
Published: June 2013

Airspace industry components frequently need high added value part including some featuredifficult to manufacture. One of the best example is the thin walls of parts (airplanes frames orthe turbine blades) that have a very low stiffness. The finishing operations for high height to thicknessratio parts lead to chatter vibrations, unacceptable dimensional errors or poor surface finish. The optimalmachining strategy determination is often based on trial and error and may not be cost effective(acceptable conditions can be far from the optimum). Simulation of the milling process is a powerfulmean to accelerate the search for better cutting parameters. Cutting forces, vibrations, geometricerrors or roughness can be predicted before the production of the first parts. The classical mechanisticapproach is even though limited while machining flexible parts because the dynamic response ofthe workpiece changes with the position of the cutter. The objective of this paper is to demonstratethe adaptation of numerical simulation of milling operation for the machining of thin-walled plates.Three complementary approaches are developed: location-dependent stability lobes, quasi static approachand full dynamic simulation. Location dependent stability lobes extend the classical theoryto take into account the variation of dynamic response along the workpiece. Quasi static approach isintended to deal with form error during chatter-free machining operations. Full dynamic simulation isa more complex approach intended to simulate the behavior of the complete tool/machine/workpiecesystem. The numerical approach is compared to experimental tests performed on thin plate of titaniumalloys.
Analysis of Machining Operations of a Femoral Prosthesis Using CAM Applications
Authors: Ferreira Pedro , Relvas Carlos , Simões Fernando
Published: June 2013

The studies of biomaterials machinability applied in the medical field are extensive, however many of these studies use models of regular geometry and use elementary machining operations. In this work, a femoral prosthesis with a complex geometric shape was experimental milled using two different commercial Computer Aided Manufacturing (CAM) applications. The toolpaths defined in both CAM applications were similar and carefully selected according with the femoral prosthesis geometry. Roughing, semi-finishing and finishing passes were applied in this work. The influence of toolpath strategy was studied and predicted results from software’s simulation were compared with milled part.
Effect of the Mechanical Parameters Used as Input Data in the Yield Criteria on the Accuracy of the Finite Element Simulation of Sheet Metal Forming Processes
Authors: Lazarescu Lucian , Ciobanu Ioan , Nicodim Ioan Pavel , Comsa Dan Sorin , Banabic Dorel
Published: June 2013

The accuracy of the finite element simulation of sheet metal forming processes is mainly influenced by the shape of the yield surface used in the mechanical model and, in particular, by the number of input values used in the identification of the yield surface. This paper investigates the effect of the input values used for identifying the BBC 2005 yield criterion on the accuracy of the finite element predictions. The accuracy assessment of the simulation is based on the comparison of the numerical predictions obtained using the commercially available FE programme AUTOFORM and experimental measurements obtained from the hydraulic bulging of sheet metals. Thickness and strain distributions, as well as the geometry of the bulged specimen were taken as comparison parameters. The accuracy of the finite element predictions obtained using the Hill-48 and Barlat-89 yield criteria is also studied and discussed in comparison with the results provided by the BBC 2005 yield and the experimental data.
A FEM-DBEM Investigation of the Influence of Process Parameters on Crack Growth in Aluminum Friction Stir Welded Butt Joints
Authors: Citarella Roberto G. , Carlone Pierpaolo , Lepore Marcello , Palazzo Gaetano S.
Published: June 2013

Medium to high strength aluminum alloys, such as 2xxx, 6xxx, and 7xxx series, are actually considered of great interest in the transport industries. For aeronautical applications, the precipitation hardenable AA2024 (Al-Cu) alloy is gaining considerable attention, in particular for the realization of nose barrier beam or fuselage panels. In this context, remarkable research effort is currently focused on the application of the Friction Stir Welding (FSW) process, as a suitable alternative to fusion welding processes. The interest in aeronautical application of FSW process is also justified by the reduction of production costs and weight and by the increase of strength and damage tolerance with respect to riveted lap joints. The implementation of the technique in safety-critical components, however, requires a deeper understanding of static strength as well as of fatigue behavior of FSWed assemblies. In this sense some experimental results have already been presented in the inherent literature, relatively, for instance, to AA6082-T6 and AA6061-T6, AA6063-T6, AA2024-T351, AA2024-T8 alloys processed by FSW. Despite the unavoidable relevance of experimental testing, a numerical approach able to predict the mechanical behavior of FSWed assemblies is very desirable, in order to achieve time and cost compression and to implement computational optimization procedures. This paper deals with a numerical investigation on the influence of FSW process parameters, namely the rotating speed and the welding speed, on fatigue crack growth in AA2024-T3 butt joints. The computational approach is based on a combined Finite Element Method (FEM) and Dual Boundary Element Method (DBEM) procedure, in order to take advantage of the main capabilities of the two methods. In particular, linear elastic FE simulations have been performed to evaluate the process induced residual stresses, by means of a recently developed technique named contour method. The computed residual stress field has then been superimposed to the stress field produced by an applied fatigue traction load in a Dual Boundary Element Method (DBEM) environment, where the simulation of a crack, initiated and propagating along the previously mentioned cutting line, can be performed in an automatic way. A two-parameters crack growth law is used for the crack propagation rate assessment. The DBEM code BEASY and the FEM code ANSYS have been sequentially coupled in the aforementioned numerical approach by using a BEASY interface module and in house developed routines. Computational results have been compared with experimental data, showing a satisfactory agreement. The influence of process parameters on the residual stresses distribution has also been highlighted.
Shape Optimization of the Conventional Simple Shear Specimen
Authors: Souto Nelson , Andrade-Campos António , Thuillier Sandrine
Published: June 2013

Shear tests of rectangular sample are widely used by the scientific community for characterizing the material behavior due to large strains obtained. However, for some hard metals, such as the dual-phase steel DP 980, premature rupture occurs in the vicinity of the grips. Due to this fact, the shape of the shear specimen is optimized in this work with the aim of maximizing the deformation achieved in the central part of the specimen without the occurrence of rupture near the grips. As the rupture occurs at the corners of the shear specimen only the boundaries are subjected to shape optimization. A representation with cubic splines is adopted for the definition of the boundaries geometry. The material is defined by Hill’s 1948 yield criterion combined with an isotropic hardening law. Two macroscopic rupture criteria are considered and an objective function approach based on the maximization of the shear strain average value is defined. For this study, a direct search optimization method is used for minimizing the objective function. The optimized geometries obtained for the different rupture criteria and different set of design variables are compared. The use of a larger number of design variables allows to obtain optimized geometries with higher average shear strain. The best specimen geometry shape allows increasing the maximum deformation of DP 980 steel to 1.05 without occurrence of rupture. In addition, the final specimen geometries show a concave shape for the boundaries which means that this kind of shape is the best one to delay the rupture in shear specimens.
Integrity Evaluation of Steel Flanges Joined with Metallic Gaskets
Authors: Gjengedal Ragnar , Fyllingen Ørjan , Sture Henrik
Published: June 2013

System integrity of a flanged connection requires that no leakages occur. Metallic flanges and their joining is of great importance when it comes to avoiding leakages from hydrocarbon lines. The American standard ASTM A182 demands that flanges must be forged to shape, thereby excluding other manufacturing methods. Mechanical properties of duplex stainless steel bars have been examined by doing tensile and charpy tests. A finite element model of a typical ASME-flange assembly was made and was used to calculate stress levels in the flange. The measured mechanical properties of the bar, showed that it is suitable for flange use.
CAD/CAM Strategies for a Parallel Kinematics SPIF Machine
Authors: Farias João B.S. , Martins Miguel A.B.E. , Afonso Daniel Gil , Marabuto Sonia R.H. , Ferreira Jorge A. , de Sousa Ricardo J. Alves
Published: June 2013

Single point incremental forming has attracted the interest of researchers in the last decade for the production of prototypes and small batch production of sheet-based parts [1, 2]. This technique allows the manufacture of parts without using expensive die sets. The SPIF (Single point incremental forming) process can be performed on different equipments such as adapted CNC milling machines, serial robots and built proposed machines [3]. Every solution has advantages and disadvantages. This work presents the CAD/CAM strategies for a parallel kinematics SPIF machine, designed and built at the University of Aveiro [3]. This machine brings a new approach to the SPIF industry. The machinery used to perform SPIF operations has limitations in their work volume with limited movements and in the magnitude of applicable forces. With that in mind, this machine was projected to overcome that obstacle, and was provided with a system with 6 degrees of freedom, while maintaining the ability to apply high loads. The disadvantage is the increase in volume occupied by the kinematic system. The manufacture of new parts could be reached out with more flexibility on the chosen tool path. The first step is the product design in the commercial CAD system. Next step is generating the tool path of the forming tool. This step is very important to achieve the desired part shape. It is used a commercial CAM system (EdgeCAM 2012®), which has resources from three up to five axis strategies. The last step is to send the information to the machine’s control system, based on real-time software. This paper will describe each step with more details.