bluuebunny/crossref_metadata_2025 huggingface dataset:
Colorimetric Sensor Based on Silver Nanoparticle – Embedded Polymethacrylate Matrix
Authors: Gavrilenko Nataliya A. , Saranchina Nadezhda V. , Gavrilenko Mikhail A.
Published: September 2014

Silver nanoparticles synthesized by a reagent less method involving only thermal treatment have been used in colorimetric assay for the detection of hydrogen peroxide. The silver nanoparticles were directly synthesized in polymethacrylate matrix (PMM) by method based on the reduction of the inorganic precursor AgNO3, which was pre-adsorbed by PMM from solution, through thermal treatment. These silver nanoparticles were characterized using absorption spectroscopy. It was shown that the silver nanoparticles in PMM (Ag – PMM) had ability for reduction of hydrogen peroxide with silver oxidation. As a result, the yellow color of Ag – PMM samples was gradually changed to transparent color depending on the hydrogen peroxide concentrations. Hence, the silver nanoparticles in PMM could be used as colorimetric sensor for hydrogen peroxide in aqueous medium.
Development of Fiber Optic Current Sensor
Authors: Grigoriev Mikhail G. , Turushev Nikita V.
Published: September 2014

Current measuring high-precision methods and devices are one of the most important modern engineering development lines in optimal energy consumption sphere. However, there are a few small-sized instruments which allow conducting precision measurements without breaking the circuit. This paper presents information about conducted Faraday Effect research and general construction of the simple fiber optic current sensor (FOCS). Researched sensor conception is used in prototype which is developing by team of laboratory number 63 of National Research Tomsk Polytechnic University Nondestructive Testing Institute. Required tests and accuracy analysis were conducted. Research results confirm that fiber optic current sensors provide high-precision measurement and proposed methodic is effective.
Self-Diffusion, Solute-Diffusion and Interdiffusion in Binary Intermetallics
Authors: Mehrer Helmut
Published: September 2014

800x600 Intermetallics are compounds of two metals or of metal(s) and semimetal(s). Their structures are usually different from those of the constituents. Some intermetallics are interesting functional materials, others have attracted attention as high-temperature structural materials. We remind the reader of some fundamentals of solid-state diffusion and to the major techniques for tracer diffusion measurements, interdiffusion studies and the growth kinetics of layers in solid diffusion couples. Starting from self-diffusion, which is the most basic diffusion phenomenon in any solid, the paper covers the main features of diffusion in binary intermetallics from the systems Cu-Zn, Ni-Al, Fe-Al, Mg-Al, Ni-Ge, Ni-Ga, Fe-Si, Ti-Al, Ni-Mn, Mo-Si, Co-Nb and Ni-Nb.. We illustrate the influence of phase transitions on diffusion and point out some common features of diffusion in intermetallics. We discuss in detail diffusion in silicides of iron, molybdenum and of silicides of refractory metals. We also consider aluminides of iron, nickel, and titanium and in the aluminium-magnesium system. We consider diffusion in intermetallics of the cobalt-niobium and nickel-niobium system and in in the Nb-Sn and V-Ga systems. We finish with some remarks about grain boundary diffusion in intermetallics. Normal 0 21 false false false UK X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}
Environmental Comparison between a Hot Extrusion Process and Conventional Machining Processes through a Life Cycle Assessment Approach
Authors: Ingarao Giuseppe , Priarone Paolo Claudio , Gagliardi Francesco , Di Lorenzo Rosa , Settineri Luca
Published: September 2014

Nowadays manufacturing technologies have to be evaluated not only for the technical features they can provide to products, but also considering the environmental perspective as well. As long as the technological feasibility of a given process is guaranteed, processes minimizing resources and energy consumption have to be selected for manufacturing. With respect to this topic, the research studies in the domain of metal processing technologies predominantly focus on conventional material removal processes as milling and turning. Despite some exceptions, many other non-machining technologies, such as metal forming processes, are still not well documented in terms of their energy and resource efficiency, and related environmental impact. In this paper, an environmental challenge between two traditional technologies is developed: the environmental performances of a partial hot extrusion process and of a turning processes are quantified and compared. A Life Cycle Assessment (LCA) approach is implemented to properly analyze the considered processes. The material production step and the manufacturing phase to obtain a simple axy-symmetric aluminum component is considered for the Life Cycle Inventory (LCI) data collection step. Besides, the material and consumables usage and the consumed electrical power are measured in order to quantify the energy consumption of the manufacturing phase. Further, the environmental impacts related to the manufacturing of the extrusion dies and of the turning process are included in the analysis. The paper presents an early step of a wider research project aiming at identifying the greenest technologies as functions of given product features.
The Influence of Rolling Schedule on the Dynamic Properties of Accumulatively Roll Bonded Nano-Layered Cu-Nb
Authors: Cerreta Ellen K. , Han Wei Zhong , Mara Nathan A. , Beyerlein Irene J. , Carpenter John S. , Zheng Shi Jian , Trujillo Carl P. , Dickerson Patricia O. , Misra Amit
Published: September 2014

Cu-Nb nanolayered material was produced through an accumulative roll bonding (ARB) technique. Using this technique, two different rolling schedules were employed to produce a normal and transverse rolled material. This resulted in specimens with differing microstructures within the 135nm thick nanolayers and interface structures between the layers. The dynamic response of these bulk Cu-Nb nanocomposites was then investigated under planar shock loading. It was observed in dynamically fractured specimens that the characteristics of ductile failure features formed on the fracture surface after dynamic loading were dependent upon the processing route of the nanocomposite. Specifically, grain shape differences due to dissimilar rolling passes are linked with differences in the failure response, particularly kinetics of fracture. In addition, incipient failure immediately below the primary fracture surface was also observed. Numerous nanovoids were nucleated and aligned linearly in the middle of Cu layers within the shocked Cu-Nb nanocomposites. These observations indicate relative stability of Cu-Nb interfaces produced by the ARB methods utilized in this study under dynamic loading conditions.
Triaxiality Effect on Material Damage Evolution in Hot Rolling
Authors: Kardoulaki Erofili , Lin Jian Guo , Balint Daniel S. , Farrugia Didier
Published: September 2014

High temperature tensile tests have been conducted on double-notched bars (DNBs) of varying notch acuity ratios (a/R), achieving a range of triaxiality, to evaluate the effect of stress state on edge cracking in hot rolling of free cutting steel. The conditions of the tensile tests are selected to physically simulate hot rolling condition of as-cast material to wrought structure. All experiments were conducted using a Gleeble 3800 thermo-mechanical testing system. The aim here is to develop a qualitative relationship between the activated damage mechanisms with respect to different stress states (arising from the sample geometry). Double-notch bars have been selected for this investigation as they enable the optical examination of the pre-failure mechanisms, captured in the unbroken notched area. The damage features have been observed at the notch areas and different damage mechanisms have been identified for different stress state deforming at different temperatures.
Improvement in Punching Properties of High Tensile Strength Steel Sheet by Heat-Treatments for Reduction of Center Segregation
Authors: Sakumoto Kota , Yamazaki Kazuhiko , Kobayashi Takashi , Suzuki Shinsuke
Published: September 2014

We investigated punching properties (crack in punched surface and hole expansion ratio) of high tensile strength steel sheets with and without center segregation. High strength steel sheets were heat-treated to reduce center segregation. Tensile strength, shear surface ratio, depth of rollover and burr height were measured on heat-treated steel sheets to confirm the effect of heat-treatment on strength. The EPMA analysis showed that the center segregation of Mn was reduced by the diffusion during heat-treatment. Crack-formation frequency and hole expansion ratio were also measured. As a result, the center segregation of Mn in high tensile strength steel sheets decreased by the heat-treatment (600 oC for 100 h) with maintaining the tensile strength, the depth of rollover and the burr height. The crack-formation frequency of the steel sheets decreased through heat-treatments.
Investigation on Flatness of Shim Rings in Blanking
Authors: Hirota Kenji , Hisaoka Hiroaki
Published: September 2014

Flatness of blanked parts is important as well as the cut edge quality and often becomes worse when blanking the low stiffness parts such as narrow shim rings. In this study, the affecting factors on the flatness of shim rings in conventional blanking were investigated through the experiments varying the ring widths and materials. Flatness was evaluated with the deflection angle. It was found that the shim ring with a smaller width and the material having a larger n value exhibited larger deflection angles. Deformation during blanking was analyzed by FE simulation and the experimental results were explained based on the strain distributions.
Evaluation of Anisotropy by Two Different Tests for TRIP800 Steel
Authors: Ozturk Fahrettin , Toros Serkan , Kilic Suleyman , Kacar Ilyas
Published: September 2014

For the process modeling, material properties such as anisotropy values at different orientation are very important. The most commonly used method for the determining of the anisotropy values is the tensile test that is performed for samples are prepared at different orientation. Besides the tensile test, the anisotropy parameters of TRIP 800 steel are measured with the hole-expansion test. The effects of the test methods on the yield surfaces are determined for using two different anisotropic yield criteria are Hill-48 and Barlat-89. Results illustrated that a significant difference is observed in the yield surfaces for the two test methods. The material under biaxial deformation is deformed plastically faster than the uniaxial deformation mode.
Instability Prediction during Stretch Bending of AHSS Sheet Metal
Authors: Hou Bo , Perdahcioglu Emin Semih , van den Boogaard A.H.
Published: September 2014

Under stretch-bending conditions where the curvature is relatively large, the plane stress assumption leads to a significant inaccuracy in forming limit prediction. In processes where a contact pressure acts on the material combined with a small punch radius it is observed by FE simulations that a significant thickness stress gradient develops. This gradient influences the materials plastic flow behavior through thickness and hence affects the cross-sectional stability of the sheet. Based on this observation a theoretical study has been performed in order to quantify the effects of different process and material parameters on the formability of the sheet. Furthermore, it is observed numerically and experimentally that during stretch-bending the cross-sectional stability is not lost instantaneously but gradually over time. Therefore, the concept of FLC proves to be insufficient as to judge acceptability of the deformed product. Another approach is proposed where an instability criterion is developed that also accounts for the partial loss of stability of the cross-section. The criterion is implemented in FE environment to be used in Shell type elements. The results are compared with stretch-bending experiments on selected HSS and AHSS.
Numerical Analysis of Rolling Extrusion Process of a Toothed Shaft from Titanium Alloy Ti6Al4V
Authors: Bartnicki Jarosław , Tomczak Janusz , Pater Zbigniew
Published: September 2014

This paper presents results of numerical calculations of rolling extrusion process of a toothed shaft made from titanium alloy Ti6Al4V. FEM analysis was conducted applying the software DEFORM 3D for the process chosen technological parameters. The kinematics of metal flow in the area of the formed teeth was analyzed. Distributions of stresses, strains and temperatures during teeth forming were determined. Calculated values of axial and radial forces and moments acting on rotating roll tools allow for designing of tools for experimental verification of the designed forming process.
Effect of ECAE on Structure and Strength of Porous A6061 Alloy with Aligned Unidirectional Pores
Authors: Suganuma Kotaro , Hayashida Tatsuro , Yuasa Takafumi , Suzuki Shinsuke
Published: September 2014

Deformation behavior of porous aluminum alloys with aligned unidirectional pores through equal-channel angular extrusion (ECAE) was investigated. The porous aluminum alloys were fabricated by dipping pure aluminum pipes into semi-solid slurry base metal. The pipes did not detach from the base metal even through the ECAE process. Comparing the sample dimension of pores before and after ECAE process, the amount of decrease in a dimension of pores was 19.4% in this study. The Vickers hardness increased by work hardening. Especially, the hardness value of area where plastic flow arose increased significantly. These results show that we can improve the mechanical properties with maintenance of the porous structure and measure the amount of the sample deformation quantitatively.
Friction in Hot Forging of Chrome Steel Covered with Oxide Scale Film Generated at Steam Atmosphere
Authors: Matsumoto Ryo , Harada Shohei , Utsunomiya Hiroshi
Published: September 2014

The hot ring compression test of chrome steel covered with an oxide scale film is carried out to examine the effects of the oxide scale film on the hot forging characteristics. For changing the chemical compositions of the oxide scale, the oxide scale film is generated at air or steam atmosphere. The nominal coefficient of shear friction of the chrome steel covered with the oxide scale film is estimated from the plastic deformation behavior during the ring compression test. The estimated coefficient of shear friction of the chrome steel covered with the oxide scale film is found to be lower than that of the chrome steel without the oxide scale film. Furthermore, the oxide scale generated at steam atmosphere provides lower friction characteristics in comparison with the oxide scale generated at air atmosphere. The mechanism of the reduction of friction with the oxide scale is discussed.
Sensitivity Analysis of Process Parameters for Developing an Improved Open Die Forging Process
Authors: Cheng Yu Feng , Yang Xiao Guang , Lu Qi , Lim Chao Voon Samuel , Huang Ai Jun
Published: September 2014

Open die hot forging has a wide industrial application on deforming ingot into billet with desired dimension and qualified internal microstructure. An example open die forging process of Ti-6Al-4V ingot is selected herein. A 3D FE-based numerical method was used to investigate the open die forging process with respect to the real working conditions. The simulation results were validated by the collected experimental process parameters from the forging system. Moreover, design of experiment method is adopted regarding the variation of process parameters to reveal the effects of critical factors on product deformation and quality characteristics. Results show that the process parameters including press speed, feed and reduction has significant effect on the workpiece deformation and effective strain which represents the forged billet formability and quality. Improved process parameters method is suggested with respect to the experienced benchmark based on the sensitivity analysis.
Keywords: Open die forging; Ti-6Al-4V alloy; Sensitivity analysis; Process parameter; Numerical simulation;
Effects of Anisotropic Yield Functions on Prediction of Forming Limit Diagram for AHS Steel
Authors: Panich Sansot , Uthaisangsuk Viton
Published: September 2014

In this study, experimental and numerical analyses of Forming Limit Diagram (FLD) for Advanced High Strength (AHS) steel grade 980 were performed. Forming limit curve was first determined by means of the Nakazima stretch-forming test. Then, analytical calculations of the FLD based on the Marciniak-Kuczynski (M-K) model were carried out. Different yield criteria, namely, Hill’48 (r-value and stress-based), Yld89 (r-value and stress-based) and Barlat2000 (Yld2000-2d) were investigated. The strain hardening law according to Swift was applied. To identify parameters of each model, uniaxial tension, balanced bi-axial bulge test and in-plane biaxial tension test were performed. As a result, predicted plastic flow stresses and plastic anisotropies of the AHS steel by various directions were evaluated. In addition, effects of the anisotropic yield functions, strain rate sensitivities, imperfection values and work hardening coefficient on the predicted FLD were studied and discussed. It was found that the FLD based on the Yld2000-2d yield criterion was in better agreement with the experimental curve. Accuracy of the FLD predictions based on the M-K theory, especially in the biaxial state of stress, significantly depended on the applied yield criteria, for which yield stresses and r-values of different loading directions were required.
Evaluation and Validation of Methods to Determine Limit Strain States with Focus on Modeling Ductile Fracture
Authors: Sabathil Andreas , Heinle Ingo , Lipp A. , Meinhardt J. , Merklein Marion
Published: September 2014

In the manufacturing process of body in white components made from sheet metal it is state of the art to accompany the process by means of finite element analysis. A main criterion for determining a feasible tool design and production process parameters is the prediction of material failure, which can be categorized in instability and ductile fracture. The ductile fracture failure mode is more likely to occur, as more advanced high strength steels and aluminum alloys are used for body in white components. Therefore different approaches have been presented to model ductile fracture over the past years. This task is more challenging when the material is exposed to arbitrary loading paths that can occur in deep drawing processes. However there is no guideline for sheet metal forming applications to determine which models for predicting ductile fracture are suitable, which experiments are necessary and how calibration of model parameters and validation of model prediction can be performed. Additionally there is no standard established that prescribes the evaluation of limit strain states from experiments. Suitable limit strain states are a basic requirement for prediction of ductile fracture as they are used for calibration of fracture models. In this paper, two methods for evaluation of limit strains are discussed and applied to tensile specimens with circular hole and circular cut outs made from aluminum alloy AlSi0.6Mg0.5. One validation experiment is used to investigate failure prediction that is based on limit strain states from different evaluation methods.
Formability of Magnesium Alloys AZ80 and ZE10
Authors: Pasang Timotius , Satanin V. , Ramezani M. , Waseem M. , Neitzert Thomas , Kamiya O.
Published: September 2014

Formability of two magnesium alloys, namely, AZ80 and ZE10, has been investigated. Both alloys were supplied with a thickness of 0.8 mm. The grain structure of the as-received AZ80 alloy showed dislocations, twins and second-phase particles and-/or precipitates distributed uniformly within grains. These were not obvious on the ZE10 alloy. The investigations were carried out at room temperature for both alloys in the as-received and heat treated conditions (410oC for 1 hour followed by water quench). The heat treatment significantly changed the grain structure of the AZ80 alloy, but did not affect the ZE10 alloy apart from grain enlargement. The formability was studied on the basis of plastic strain ratio (r) and strain hardening coefficient (n) by means of tensile testing. In the as-received condition, the ZE10 alloy had a slightly better formability () than AZ80 alloy. Following heat treatment, however, the formability of the AZ80 alloy was improved significantly (by about 26%), while the ZE10 alloy did not show any significant change.
Advancement in Understanding of Descalability during High Pressure Descaling
Authors: Farrugia D. , Richardson Andrew , Lan Yong Jun
Published: September 2014

This paper building upon studies [1‐8] describes a subset of the High Pressure Water (HPW) descaling strategy developed at Tata Steel UK to optimise descaling set-ups for range of steel grades prone to adherent primary scale such as in high alloy steels (Si, Ni, Cr). Effective primary descaling, i.e. descaling post furnace discharge via washbox or alternative technologies is imperative to obtain good surface quality and conditioning of the surface state as well as the morphology, growth and behaviour of the secondary/tertiary scale. This paper primarily focuses on analytical descaling concepts for both mechanical and thermal outputs for flat jet nozzle and process factors. This approach has been linked to recent developments for oxide scale evolution during rolling and descaling [8].
Mechanical Response of Microalloyed Steel Subjected to Nonlinear Deformation
Authors: Lisiecka-Graca Paulina , Muszka Krzysztof , Majta Janusz , Stefanska-Kadziela Monika , Dziedzic Dominik , Kwiecień Marcin
Published: September 2014

Microalloyed steels have been the subject of theoretical and experimental studies revealing their exceptional mechanical response under nonlinear deformation conditions. In microalloyed steels, especially in multiphase steels, the mechanical properties are adjusted by combination of microstructure components with different levels of theirs mechanical responses, including hardness and ductility. A comprehensive studies have revealed that a transition from the development of usual bulk dislocation microstructures to more architecture ones occurs when the applied strain path allows to cumulate the deformation energy what is also strictly connected with the chemical and structural compositions of analyzed materials. The study presented here aims at understanding the complex strengthening mechanisms as well as microstructure evolution and to provide a link with the mechanical behaviour of investigated steels under nonlinear deformation conditions. The proper choice of the work hardening model for the cyclic plastic deformation is essential for predicting the inhomogeneities occurring during metal forming. Aim of the current work is to discuss the differences between various hardening models with respect to their capabilities in capturing complex deformation models and possibilities of their direct application to finite element modelling of such deformation processes. The results of experimental studies are integrated with computer modelling and dislocation theory to provide insight into the unprecedented combination of properties achieved in certain multiphase steels such as ultra-high flow strengths, good ductility and workability. Finally, based upon results obtained in performed computer simulations, conclusions regarding the possibilities of potential application of the work hardening models in the identification process parameters, trough the inverse analysis, are drawn.
Characteristics of Fluoride Based Conversion Coating Film on Al-Alloy for Metal Forming Applications
Authors: Premanond Varunee , Niyomrit Pongpan
Published: September 2014

During the process of cold forming of aluminum, the high pressure which is introduced on the die can result in high adhesion between the aluminum and the die surface. Therefore, it is necessary for the aluminum billet to be coated with a lubricant prior to forming, to reduce adhesion and to ease the flow of material in the die. There are several popular types of lubricant systems used in cold forging of aluminum. For severe deformation, conversion coating in conjunction with soap lubricant are commonly used. The conversion coatings include soap phosphates (PO4-soap), as well as soap aluminum fluoride (AlF-soap). Therefore, this work studied the performance of the AlF-soap system and compared it to the conventional PO4-soap system as tested on AA6063 aluminum. Ring compression tests and ball on disc tests were conducted to explore friction conditions and the thinning of the lubricant under several forming conditions. It was found that the quantity of metal soap layer of AlF-soap used affected the friction coefficient and the lubricant thinning under forming operation. The suitable coating weight of metal soap layer of AlF-soap for this experiment was found to be 2 g/m2. The friction coefficient of the PO4-soap system was 16.26% lower than the AlF-soap system. However, the amount of thinning of the AlF-soap film after ring compression tests was lower than that of PO4-soap film.
Impact of High Speed Incremental Forming on Material Properties of AA6082 Sheets
Authors: Ambrogio Giuseppina , Bruschi Stefania , Gagliardi Francesco , Ghiotti Andrea , Filice Luigino
Published: September 2014

It is well known that Incremental Sheet Forming has two main drawbacks, i.e. accuracy and slowness. The former has been studied and partially solved by several researchers while the latter did not receive convincing answers. Thus, the idea of several research groups is that the process applicability is suggested only for rapid manufacturing or small batch production. The lack of knowledge is certainly caused by the available machines, like milling or Amino, which are typically used for incremental forming operations. In the present research the attention was focalized on the above limit: an experimental campaign was performed in order to evaluate the process feasibility at very high speed. To do that a lathe machine has been used instead of the conventional milling one, increasing the process speed up to two order of magnitude. An aluminum alloy, widely used in the mechanical fields, has been chosen as sample material and an experimental investigation has been aimed at determining the influence of tool speed on the material behavior.
High Temperature Thermal Stability of Innovative Nanostructured Thin Coatings for Advanced Tooling
Authors: Cabibbo Marcello , El Mehtedi Mohamad , Clemente Nicola , Spigarelli Stefano , Hamouda A.M.S. , Musharavati Farayi , Daurù Mauro
Published: September 2014

Tools for machining are made of hard steels and cemented carbide (WC-Co). For specialized applications, such as aluminium machining, diamond or polycrystalline cubic boron nitride are also used. The main problem with steel, isthat itexhibits a relatively low hardness (below 10 GPa) which strongly decreases upon annealing above about 600 K.Thus, the majority of modern tools are nowadays coated with hard coatings that increase the hardness, decrease the coefficient of friction and protect the tools against oxidation. A similar approach has been recently used to obtain a longer duration of the dies for aluminium die-casting.
Bending and Stamping Processes of FSWed Thin Sheets in AA1050 Alloy
Authors: Simoncini Michela , Panaccio Lorenzo , Forcellese Archimede
Published: September 2014

The present investigation aims at studying post-welding forming operations of friction stir welded AA1050 aluminium thin sheets. A preliminary investigation has allowed to define the rotational and welding speed values leading to friction stir welded joints with high mechanical properties. Then, formability and elastic springback were evaluated using the hemispherical punch and bending tests, respectively. A microstructural investigation has allowed to relate the mechanical properties of joints to microstructure. Finally, the friction stir welded assemblies were subjected to air bending and stamping experiments in order to evaluate their attitude to undergo to sheet metal forming operations.
Influence of Eccentric Arrangement of the Die for the Temperature Distribution in the Sample during the Pressure-Assisted Induction Sintering (PAIS)
Authors: Siemiaszko Dariusz , Szykut Marek
Published: September 2014

In this work, the pressure-assisted induction sintering (PAIS) method, is being presented. The specimens (a cylindrical shape, diameter of 50 mm, height of 10 mm) was heated by a induction coil with heating speed of about 220 K/s to temperature 800°C, 850oC, 900oC, 950oC and 1000oC. During this process, the temperature of specimen was measured by five thermocouples (Φ 0.5 mm) which were located into graphite punch with sampling frequency of 2 Hz. Firstly, the die with specimen was located in the center of the coil. Next, the die was located out of the coil center (1 and 2 cm in four directions) and heated again. The analyzed samples show a difference of heat flow in the specimens. The studies also showed the difference between the temperature at the surface of the matrix (measured by a pyrometer) and the temperature of the sample (measured by a thermocouples). Two types of thermocouples placement were tested, parallel and perpendicular to the door of the vacuum chamber. In addition, an analysis of the temperature distribution along the diameter of the sample was performed.
Numerical Analysis of Welding Phenomena in High-Frequency Electric Resistance Welding
Authors: Okabe Takatoshi , Toyoda Shunsuke , Goto Sota , Kato Yasushi , Yasuda Koichi , Nakata Kazuhiro
Published: September 2014

High-frequency electric resistance welded pipes are used for high-grade line pipes. To address the significant need for weld seam reliability, it is important to clarify the associated welding phenomena. In this study, a numerical analysis model is developed to clarify the behaviours of the molten steel and oxide in HFW pipes. The temperature distribution of the HFW is calculated using electromagnetic and heat conductive finite element analysis methods. The molten metal and oxide flows are analysed by modelling heat conductive and plastic flows. The movement behaviour of the oxides in the molten steel is successfully analysed with this technique. The material properties as a function of the temperature of the steel pipe are calculated using general-purpose simulation software. With pressurisation by the welding rolls, the molten steel moves to the upper part, and the oxide, which exists in the internal parts, rapidly decreases such that almost all of the oxide transitions to the excess metal part. The internal oxide content rate after pressurisation at 0.08 m/s is less than 0.01. To decrease the oxide content, the pressurisation rate must increase such that the molten steel and an oxide pressurised at high temperatures transition to the excess metal part.
Robotic Friction Stir Welding of AA5754 Aluminum Alloy Sheets at Different Initial Temper States
Authors: Callegari Massimo , Forcellese Archimede , Palpacelli Matteo , Simoncini Michela
Published: September 2014

Robotic friction stir welding experiments were performed on AA5754 aluminium alloy sheets, 2.5 mm in thickness, in two different temper states (H111 and O-annealed). A six axes robot with a hybrid structure, characterised by an arm with parallel kinematics and a roll-pitch-roll wrist with serial kinematics, was used. The effect of the process parameters on the macro-and micro-mechanical properties and microstructure of joints was widely analysed. It was shown that, under the same process condition, the mechanical properties of the joints are strongly influenced by the initial temper state of the alloy. In particular, as AA5754-H111 is welded, the ultimate tensile strength is not significantly affected by the process parameters whilst the ultimate elongation significantly depends on the welding speed. In AA5754-O, both ultimate values of tensile strength and elongation are affected by the welding speed whilst a negligible effect of the rotational speed can be observed. Irrespective of the welding parameters, the H111 temper state leads to mechanical properties higher than those given by the O-annealed state. An investigation has been also carried out in order to evaluate the micro-hardness profiles and microstructure of the FSWed joints in order to understand the mechanisms operating during robotic friction stir welding.
Work-Hardening Behavior upon Reverse Loading in a Rolled AZ31 Magnesium Alloy Sheet
Authors: Hama Takayuki , Takuda Hirohiko
Published: September 2014

The objective of this study was to understand the work-hardening behavior of a rolled AZ31 magnesium alloy sheet upon reverse loading. Firstly we carried out an in-plane compression-tension test of a rolled AZ31 magnesium alloy sheet with various compressive strains. The sigmoidal curve was exhibited during tension regardless of the amount of compressive strain, but a shape of the curve was clearly different depending on the compressive strain. To understand the mechanism of this difference, a crystal plasticity finite-element simulation was carried out. The simulation result showed that the above difference in the shape was owing to the difference in the activities of slip and twinning systems during tension depending on the compressive strain.
Efficient Numerical Simulation of Steady-State Metal Forming Processes by an Iterative Surface Calculation
Authors: Ripert Ugo , Fourment Lionel
Published: September 2014

The 3D finite element simulations of processes like multi-pass rolling or drawing often result into exorbitant computational times that make the numerical approach almost infeasible while only the “stationary” step of the process is actually of interest for the industry. Therefore, it can be advantageously simulated by resorting to steady-state formulations which allows reducing the calculation time by, at least, an order of magnitude with respect to more conventional methods where the steady regime is incrementally calculated. A general and robust formulation is developed; it is suitable for parallel computing, compatible with unstructured meshes and general enough to apply to a wide range of forming processes. It consists in alternatively resolving the “simple” steady-state material forming problem for a given domain geometry and then computing the domain corrections that allow satisfying the free surface condition. Within the “simple forming problem”, a Streamline Upwind Petrov Galerkin (SUPG) method is used to integrate the state variables along the streamlines. For the domain geometry correction, a Least Squares formulation with an Upwind shift is introduced. The two resolutions are coupled by the contact equations. This method is applied to several metal forming problems such as 3D rolling and drawing. Results show the high efficiency of the method with respect to an incremental resolution. Computational time is reduced by a factor ranging between 20 and 30. Results are as accurate as with an incremental method. Convergence is always reached whatever the initial geometry of the domain at the beginning of the iterative algorithm.
Finite Element Simulation of Formed Steel Components
Authors: Akinlabi Stephen , Pietra Francesco , Akinlabi Esther Titilayo
Published: September 2014

Forming is a manufacturing process by which the geometrical shape and size of sheet and plate metals are changed by means of either an external force using mechanical presses and dies or induced thermal stresses by external heat. This study reports on the finite element analysis of mechanically formed steel components using the ANSYS commercial package version 14.5. The samples of the steel sheets were mechanically formed to about 120 mm curvatures using a 20 ton capacity eccentric mechanical press at room temperature. The results showed that the steel samples were successfully formed to the curvature of about 120 mm and the finite element modelled results confirmed the experimental measured curvature.
Key words: Forming, Mechanical presses, Finite Element Simulation and Sheets.
Prediction of Life of Compound Die Using Artificial Neural Network (ANN)
Authors: Kashid Sachin , Kumar Shailendra
Published: September 2014

Prediction of life of compound die is an important activity usually carried out by highly experienced die designers in sheet metal industries. In this paper, research work involved in the prediction of life of compound die using artificial neural network (ANN) is presented. The parameters affecting life of compound die are investigated through FEM analysis and the critical simulation values are determined. Thereafter, an ANN model is developed using MATLAB. This ANN model is trained from FEM simulation results. The proposed ANN model is tested successfully on different compound dies designed for manufacturing sheet metal parts. A sample run of the proposed ANN model is also demonstrated in this paper.
FFT-Based Modelling of Transformation Plasticity in Polycrystalline Materials during Diffusive Phase Transformation
Authors: Otsuka T. , Brenner Renald , Bacroix Brigitte
Published: September 2014

During phase transformation of steels, when stress is applied, significant large strain can be observed even though the applied stress is smaller than their yield stresses. This phenomenon is called Transformation Plasticity or TRansformation Induced Plasticity (TRIP). Transformation plasticity is known to play an important role during steel producing processes. Although its importance, the phenomenon is not fully understood because of complicated coupled effect of metallurgical, thermal and mechanical behaviour during phase transformation. There are several explanations which account for the phenomenon. Among those, Greenwood-Johnson effect appears to be appropriate explanation especially for diffusive phase transformation. According to Greenwood-Johnson effect, volume change during phase transformation causes locally heterogeneous stress variation and it results in the macroscopic strain together with small applied stress. Along with the notion, Leblond et. al. developed an analytical model which describes well the phenomenon of transformation plasticity. On the other hand, the authors have developed a micromechanical model of polycrystalline materials using discrete FFT (Fast Fourier Transform) method with diffusive phase transformation. In this study, volume expansion along with phase transformation (Greenwood-Johnson effect) is taken into account in the model in order to evaluate the transformation plasticity and micromechanical behaviour during phase transformation. The results by FFT confirm linear relation between applied stress and transformation plastic strain, only if the applied stress does not exceed a half the value of yield stress of the parent phase. In contrast, if applied stress is relatively large (more than half of yield stress of weaker phase), the linear relation is never satisfied. The numerical results are compared with those of experimental and of Leblond model. Furthermore, pre-deformation (deformation just before phase transformation) effect on transformation plasticity is investigated. As a first step, uniaxial tensile followed by phase transformation simulation is carried out. Back stress develops in the course of tensile process and thus the material will be macroscopically anisotropic. It is found that the pre-deformation causes anisotropic dilatation during phase transformation. The mechanism of this anisotropic dilatation will be discussed in the micromechanical point of view.
Prediction of Ridging by 3-Dimensional Texture in Ferritic Stainless Steels
Authors: Chung Yang Jin , Ahn Deok Chan , Barlat Frédéric , Lee Myoung Gyu
Published: September 2014

Experimental and numerical investigations of the ridging in ferritic stainless steels were presented in this paper. Two kinds of ferritic stainless steels exhibiting different levels of ridging were selected as model materials. The measured roughness of the uniaxially elongated specimens up to 15% in rolling direction (RD) was compared to the prediction using a rate-dependent crystal plasticity FEM (CPFEM). Initial textures of the two materials on 5 equi-spaced sequential RD planes were obtained by EBSD measurement. The initial textures were utilized as input data for the constitutive parameters of the crystal plasticity. Measured respective single planar textures were collected all together so that the 5-layer textures complete 3-dimensional structure and they were mapped onto the FE mesh. Ridging profiles predicted by the CPFEM using both every single layer texture and multilayer texture were compared to the experimental results. Predicted ridging profile of a material exhibiting weak ridging by using 5-layer EBSD mapping was in good agreement with the experimental result. On the other hand, prediction by using only single layer texture was efficient to estimate the ridging in a material exhibiting severe ridging due to the elongated cluster of analogous orientations along RD.
Determination of the Heat Flux in the Process of Solidiﬁcation by Applying the Ant Colony Optimization Algorithm
Authors: Hetmaniok Edyta , Slota Damian
Published: September 2014

The paper presents an application of Ant Colony Optimization algorithm as a partof procedure for solving the inverse solidiﬁcation problem. Investigated task consists in recon-struction of the boundary condition (heat ﬂux) on the basis of temperature measurements inselected points of the cast. First step of the method is based on the ﬁnite diﬀerence method withapplication of the generalized alternating phase truncation method and serves for solving theappropriate direct solidiﬁcation problem. In the second step some functional representing thecrucial part of the procedure is minimized with the aid of Ant Colony Optimization algorithm.
Process-Controlled Forming Using an Intelligent Tool on a Servo Press
Authors: Engel Bernd , Kersten Sebastian , Kopfer Peter
Published: September 2014

With regard to the climate change as well as the shortage and increase in price of natural resources, efficient resource management becomes more and more important, also for production processes. More than half of the sheet metal used in the automotive industry is wasted. Considering the amount of energy and the added value associated to the discards, enormous savings are possible. The approach of this research work is to avoid waste during a forming process by means of a continuous process monitoring and a self-learning intelligent tool interacting with the servo press. The flexibility of the servo press, which is so far used to optimize the single press stroke, only, shall be exerted to respond on altering material properties of blank sheets and the thereby changing forming behaviour. The sample process includes a two-tiered bending process, in which a conventional punch performs the pre-bending in the first step and an independent servo axis the compensation-bending in the second step. If an inadmissible bending angle is measured after the second step, the servo press stops automatically and the additional servo axis performs a teaching-stroke to adjust the compensation angle. After that, the continuous process starts again. This paper presents the springback compensation strategy which uses flexible correction algorithms based on data of the on-line process monitoring as well as data of the previous bending steps. Finite Element Analyses are carried out to validate the strategy.
Sintering Kinetics of the Powder during Fields-Activated Micro-Forming and Sintering (Micro-FAST) of Copper Micro-Gears
Authors: Huang Kun Lan , Yang Yi , Qin Yi
Published: September 2014

Forming of micro-components from powder with fields-activated sintering technology (FAST) renders different forming and sintering mechanisms, comparing to that occurring during the forming of macro-sized components with a similar technology. Establishing a good understanding of these mechanisms would help process design and control aiming at achieving desired quality of the components to be formed. This paper presents a study and the results on the sintering kinetics of the powder during Micro-FAST for the fabrication of micro-gears (the module is 0.2 and the pitch diameter 1.6 mm) from copper powder. The results showed that the densification of copper powder is related largely to the bulk plastic-deformations of the particles and the melting of the particles at contact interfaces. Particularly, it is revealed that plastic deformations of the copper particles mainly occurred at approximately 340 °C and melting of the particle-interfaces at approximately 640 °C. Differently, in a densification process with a traditional powder sintering method, grain growth and neck growth would, normally, be two dominant mechanisms that achieve the densification of powder.
Investigation on Dimensional Accuracy in Micro Cross Wedge Rolling of Metals
Authors: Lu Haina N. , Wei D.B. , Jiang Z.Y.
Published: September 2014

A novel microforming process - Micro Cross Wedge Rolling (MCWR) has been developed. It is a very promising technology in the field of microforming due to its advantages such as high product rate and minimised material consumption. How to control geometrical accuracy of the produced micro parts is one of the major challenges in the development of microforming technology. Geometrical accuracy was still concentrated in term of springback. When the wedge tools loads are removed after forming step, a portion of the deformation recovers, which causes a change in the shape of micro parts. In other word, springback happens, which should be determined and controlled especially in microforming technology. A series of MCWR experiments of pure copper and aluminium have been carried out using the machine designed by authors in this study. Cylindrical workpieces were deformed into stepped shafts with cross-sectional area reductions of 35, 52.73 and 75%. Corresponding finite element simulation has also been conducted in consideration of the size effect on the material flow. The springback was proposed to account for the geometrical error of micro products. The effect of grained heterogeneity on the height of surface asperity after rolling was assessed quantitatively.
Keywords: Micro cross wedge rolling, Size effect, Dimensional accuracy, Springback