Showing papers in "International Journal of Material Forming in 2008"
TL;DR: In this article, the incorporation of zinc oxide nanoparticles into the polymer matrix has been investigated. But the results showed that the ZnO nanoparticles were uniformly dispersed in the polymers matrix and the particles remained their original size (20-150nm).
Abstract: The introduction of inorganic nanomaterials into polymer matrix has resulted in polymer nanostructured materials exhibiting multi-functional, high performance polymer characteristics beyond what traditional polymer composites possess. Multi-functional features attributable to polymer nanocomposites consist of improved moisture resistance, antibacterial and fungal properties. Zinc oxide powders was prepared via coprecipitation and used as inorganic materials; polyvinylalcohole was used as polymer matrix. The technical approach involves the introduction of nanoparticles into polymer matrix whereby nanoparticles has antibacterial characteristics and enhanced inclusion into the polymer matrix. The objectives of this paper are to summarize our research activities in: (a) developing processes to disperse nanomaterials (undoped and doped zinc oxide powders) in the polymers matrix, (b) using optical microscopy and scanning electron microscopy (SEM) techniques to characterize polymer matrix structures, (c) studying structure-property relationship of these types of new materials, and (d) evaluating the antibacterial performance of these materials for different applications. The results also show that the ZnO nanoparticles were uniformly dispersed in the polymer matrix and the particles remained their original size (20–150 nm) before incorporation into the polymer matrix.
133 citations
TL;DR: In this article, a five stage forming strategy for Single Point Incremental Forming of a circular cylindrical cup with a height/radius ratio of one is presented, where geometrical relations are discussed and theoretical strains are calculated.
Abstract: A five stage forming strategy for Single Point Incremental Forming of a circular cylindrical cup with a height/radius ratio of one is presented. Geometrical relations are discussed and theoretical strains are calculated. The influence of forming direction (upwards or downwards) is investigated for the second stage comparing explicit FE analysis with experiments. Good agreement is found between calculated and measured thickness distribution, overall geometry and strains. Using the proposed multi stage strategy it is shown possible to produce a cup with a height close to the radius and sides parallel to the symmetry axis in about half of the depth.
102 citations
TL;DR: In this article, the applicability of Single Point Incremental Forming techniques (SPIF) to thermoplastic materials was investigated and a 24-1 fractional factorial design of experiments with three replications was performed to investigate the effects of forming parameters on material formability.
Abstract: This paper presents some preliminary investigations on applicability of Single Point Incremental Forming techniques (SPIF) to thermoplastic materials. A 24-1 fractional factorial design of experiments with three replications was performed to investigate the effects of forming parameters on material formability. To study the formability of the thermoplastic sheets, a cone-shaped part with circular generatrix with varying wall angles with respect to depth was considered. The formability of SPIF to the thermoplastic sheets can be defined in terms of the maximum wall angle reached without tearing and/or failure. This angle was measured at position where the mechanical failure of the deformed sheet occurred such as wrinkling, crushing and tearing. It is concluded that the existing knowledge and know-how of sheet metal on SPIF process can be applied to thermoplastic sheets that has potential and preeminent benefits.
79 citations
TL;DR: In this paper, a semi-discrete finite element made of woven unit cells under biaxial tension and in-plane shear is presented, where the yarn directions must be strictly followed during the large strains of the fabric.
Abstract: Different approaches used for the simulation of woven reinforcement forming are investigated. Especially several methods based on finite element approximation are presented. Some are based on continuous modelling, while others, called discrete or mesoscopic approaches, model the components of the fabric. A semi discrete finite element made of woven unit cells under biaxial tension and in-plane shear is detailed. In continuous approaches, the difficulty lies in the necessity to take the strong specificity of the fibrous material into account. The yarn directions must be strictly followed during the large strains of the fabric. This is the main goal of the non-orthogonal model and of the hypoelastic constitutive model based on the yarn rotation presented in this paper. In the case of discrete and semi-discrete approaches the directions of the yarns are “naturally” followed because the yarns are modeled. Explicitly, however, modeling each component at the mesoscopic scale can lead to high numerical cost.
76 citations
TL;DR: In this article, two generic mechanisms of dispersion of carbon nanotubes in a low-viscosity solvent or a high-Viscosity polymer are discussed, focusing on the neat tubes not surface functionalized in any way.
Abstract: We review two generic mechanisms of dispersion of carbon nanotubes in a low-viscosity solvent or high-viscosity polymer, focusing on the neat nanotubes not surface-functionalized in any way. We give estimates of the van der Waals energies involved in nanotube aggregates and examine two main techniques: ultrasonication and shear mixing. For ultrasonic dispersion methods, the local mechanical energy applied to individual tubes is high and bundle separation is assured in the cavitation regime. We analyze and estimate the tube scission during ultrasonic cavitation and predict the characteristic nanotube length L
lim below which scission does not occur. For shear-mixing, our analysis suggests that dispersion is possible in non-parallel bundled nanotube aggregates, in high-viscosity polymers, once a critical mixing time t* is reached. We then examine characteristic features of nanotube-polymer composite rheology and its aging/stability against re-aggregation. We show that at nanotube loading above overlap concentration the tubes form an elastic network in the matrix. Physical junctions of this network are strong and stable enough to provide a rubber-like elastic response with very slow relaxation.
65 citations
TL;DR: In this paper, the formability of laser assisted friction stir welded steel aluminium joints was evaluated by applying tensile tests to achieve mechanical properties of joints, which were welded by systematic variation of process parameters.
Abstract: Steel aluminium Tailor Welded Hybrids are still mentioned to be difficult to be joint as intermetallic phases appear during melting welding techniques. These phases are the reason for failure of the joint during loading or forming. As conventional friction stir welding, a solid phase welding technology, is not feasible to join steel and aluminium, laser assistance for preheating the steel sheet is adapted in order to enhance the weldability as well as the welding feed and to reduce the wear at the tool. Tensile tests are performed to achieve mechanical properties of joints, which were welded by systematic variation of process parameters. Finally deep drawing tests are conducted to demonstrate the formability of laser assisted friction stir welded steel aluminium joints.
60 citations
TL;DR: In this paper, the challenges in woven composites forming, from material variations, experimental material characterization methods to numerical modeling is reviewed and results on material shear behavior from bias extension tests are presented.
Abstract: Woven-fabric reinforced composites have gained a significant attention from both industrial and academic fields, due to their high specific strength and stiffness as well as their supreme formability characteristics. In this work, the challenges in woven composites forming, from material variations, experimental material characterization methods to numerical modeling is reviewed and results on material shear behavior from bias-extension tests are presented. Three different types of fabrics (plain, balanced twill, and unbalanced twill weaves) were tested using various aspect ratios. From force-displacement curves, shear angles and normalized shear forces were theoretically determined and test data from different aspect ratios were compared with each other. Additionally, real-time shear angles were measured using the IcaSoft image correlation software developed at INSA-Lyon and compared with manually measured shear angles.
57 citations
TL;DR: In this paper, a study of the laser assisted machining of Inconel 718 (NiCr19FeNb at 46 HRc) with carbide and ceramic insert is presented.
Abstract: Laser assisted machining (LAM) can improve the machinability of materials by locally heating the material prior to its removal. The work presented here is a study of the laser assisted machining of Inconel 718 (NiCr19FeNb at 46 HRc) with carbide and ceramic insert. The tests have shown a reduction in the cutting force, and have highlighted the impact of laser assistance on the integrity surface (roughness, appearance, residual stress) and the tool life.
52 citations
TL;DR: In this paper, a multi-step approach for single point incremental forming was proposed and experiments were performed and compared with simulations to better understand the phenomena underlying the improved process performance, and the multi-stage approach was compared with simulation to understand the underlying process performance.
Abstract: Although Incremental Forming offers distinct advantages over traditional forming processes, such as short lead times and low setup costs, the process still has some drawbacks Besides the obtainable accuracy, one of the main challenges of the process are the process limits Many workpiece geometries cannot be manufactured due to the fact that the maximum wall angle that can be formed is limited for a certain sheet material and thickness to a given angle Different solutions to this approach have been proposed and this paper further investigates one of those solutions, the multi step approach for single point incremental forming Experiments were performed and compared with simulations to better understand the phenomena underlying the improved process performance
51 citations
TL;DR: In this paper, the authors investigated the possibility of extension of classical orbital forging technology to obtain more cost effective forging process, which is the process used for forging of shaped parts by applying the incremental forging method.
Abstract: The main subject of the present work is investigation of possibility of extension of classical orbital forging technology to obtain more cost effective forging process. Orbital forging is the process used for forging of shaped parts by applying the incremental forging method. Results of simulation of orbital forging are compared in the present work with the result obtained from a conventional forging process. 3D finite element (FE) simulations are used in the present project to evaluate the capabilities of the orbital forging process and proper die design, and to predict the forging loads the. Selected results of simulations are presented in the paper. These results are the basis for the further comparison and discussion about possible modifications of conventional orbital forging approach.
47 citations
TL;DR: In this article, the authors give a brief overview of microstructure and rheology that have been observed for a range of carbon nanotube (CNT) suspensions, and present a series of parallel plate optical observations showing a broad spectrum of behaviour for different shear conditions.
Abstract: This paper gives a brief overview of microstructure and rheology that have been observed for a range of carbon nanotube (CNT) suspensions. In general, untreated CNT suspensions show a much higher level of observable optical microstructure reflecting their preference to aggregate; they also show higher levels of viscoelasticity over treated CNT suspensions. An unexpected Helical Band texture for untreated CNTs is reported together with a series of parallel plate optical observations showing a broad spectrum of behaviour for different shear conditions. Both steady shear and linear viscoelastic data are presented for treated and untreated systems.
TL;DR: In this paper, the gas and aroma barrier properties of poly(lactic acid) (PLA) films were analyzed and the influence of PLA crystallinity on these properties was studied because of processing conditions.
Abstract: Poly(lactic acid) (PLA) films have a great interest for the food packaging. But the interaction between the food and the packaging must be investigated. The gas and aroma barrier properties of PLA were analysed and the influence of PLA crystallinity on these properties was studied because of processing conditions. The crystallinity seems to have no effect on helium and oxygen barrier properties but ethyl acetate as aroma compound has a plasticizing effect on the PLA film.
TL;DR: In this paper, a specific friction test, called the Warm Hot Upsetting Sliding Test (WHUST), is used to reproduce hot forging contact conditions, such as friction force/normal load ratio or sliding distance before the first scratch, to characterize the contactor wear at microscopic and macroscopic scales.
Abstract: The aim of the present work is to improved comprehension of wear phenomenon during hot steel forging with sprayed lubricants. The study reported in this paper uses a specific friction test, called the Warm Hot Upsetting Sliding Test (WHUST), which reproduces hot forging contact conditions. Wear markers –such as friction force/normal load ratio or sliding distance before the first scratch– are proposed to characterize the contactor wear at microscopic and macroscopic scales. Friction tests are performed on 1100°C heated specimens to characterize the influence of graphite based lubricant film thickness and particle sizes on friction and wear in the flash zone of a nitrided steel die.
TL;DR: The Cambridge process was developed to utilize these unique properties by directly spinning carbon nanotube fibres drawn from an aerogel sock as mentioned in this paper, which can be made at a rate of 20m/min.
Abstract: Carbon nanotubes are regarded by many as being the next generation in high performance materials due to their unique properties. The Cambridge Process was developed to utilize these unique properties by directly spinning carbon nanotube fibres drawn from an aerogel sock. The sock is formed from carbon nanotubes grown via a catalytic chemical vapour deposition (CVD) process. Due to the nature of CVD, the process is readily scalable. Kilometres of fibre can be made at a rate of 20 m/min. Altering process parameters (catalyst concentration, feedstock injection rate, furnace temperature, and gas flow rate) allows the production of nanotubes of a desired morphology. The fibres have been characterized with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman Spectroscopy in order to confirm nanotube composition and orientation. The fibre possesses mechanical and electrical properties that rival or exceed those of present-day materials. Mechanical properties can be enhanced by increasing the degree of orientation of the nanotubes with the long axis of the fibre and by overall densification. These effects can be accomplished through drawing the fibre and solvent treatment.
TL;DR: In this paper, the effect of lubrication cooling condition on surface roughness in finish face milling operations has been widely investigated, and the evolution of the surface finish and tool wear with cutting time have been monitored.
Abstract: The effect of lubrication-cooling condition on surface roughness in finish face milling operations has been widely investigated. Different cutting speeds and lubrication cooling conditions (dry, wet and MQL), in finish face milling of AISI 420 B stainless steel, have been considered. The evolution of the surface finish and tool wear with cutting time have been monitored. Analytical and artificial neural networkmodels, able to predict the surface roughness under different machining conditions, have been proposed.
TL;DR: In this paper, a prototype micro-sheet-forming machine system has been developed, which addresses the specific issues concerning machine dynamics, material feeding, production rate, tool design and fabrication, and part transport.
Abstract: Challenges concerning industrial applications of microforming have been recognised, and efforts are being made to meet these challenges. For micro-sheet forming, fundamentals related to the development of an industrial system are being examined further by the EU MASMICRO consortium, based on which prototype micro-sheet-forming machine system has been developed. The system development addresses the specific issues concerning machine dynamics, material feeding, production rate, tool design and fabrication, and part transport. The prototype system has been tested with the forming of demonstration components and an industrial version of the machine has been designed.
TL;DR: In this paper, the authors developed an inverse method for adjusting the material parameters for single point incremental forming (SPIF), which consists in FEM simulations of simple tests involving the SPIF specificities (the "line test") performed on the machine used for the process itself.
Abstract: The purpose of this article is to develop an inverse method for adjusting the material parameters for single point incremental forming (SPIF). The main idea consists in FEM simulations of simple tests involving the SPIF specificities (the “line test”) performed on the machine used for the process itself. This approach decreases the equipment cost. It has the advantage that the material parameters are fitted for heterogeneous stress and strain fields close to the ones occurring during the actual process. A first set of material parameters, adjusted for the aluminum alloy AA3103 with classical tests (tensile and cyclic shear tests), is compared with parameters adjusted by the line test. It is shown that the chosen tests and the strain state level have an important impact on the adjusted material data and on the accuracy of the tool force prediction reached during the SPIF process.
TL;DR: In this article, a mesoscopic model based on the Reynolds equation for thin film lubrication has been validated against experiments for 2'×'2 twill/PP (Twintex) and 8 harness satin/PPS laminates.
Abstract: Friction is an important phenomenon that can dominate the resulting product geometry of thermoplastic composites upon forming. A model was developed that predicts the friction between a thermoplastic laminate and a rigid tool. The mesoscopic model, based on the Reynolds’ equation for thin film lubrication, has been validated against experiments. The tool-ply friction was characterised for 2 × 2 twill/PP (Twintex) and 8 harness satin/PPS laminates. Tool-ply friction of the latter appears to be a combination of a Coulomb type of friction and a viscous type of friction.
TL;DR: In this article, a review of the application of carbon nanotubes for microfluidic lab-on-a-chip is presented, where the authors investigate the tunable mechanical, chemical, electrical and electrical properties of carbon nano-structures in order to manipulate and analyse extremely small volumes of fluid effectively.
Abstract: Microfluidic lab-on-a-chip allows chemical and biochemical analysis to be conducted in a miniaturized system. Miniaturized analysis reduces the reagent consumption while decreasing the overall size of the device, but the small dose of the sample make detection more demanding and is more sensitive to adsorption of species on the surface. Integration of carbon nanotubes into microfludic devices is a promising approach. This review addresses recent advances in the application of carbon nanotubes for microfluidic lab-on-a-chip. The literature review shows that carbon nanotubes have been used to achieve superlubrifying microchannels, act as high density nanoporous membranes, electrical transducers mainly in flow sensors and biosensors, and mimics of living systems. In addition, extensive work has been carried out to investigate the tunable mechanical, chemical and electrical properties of carbon nanotubes in order to manipulate and analyse extremely small volumes of fluid effectively.
TL;DR: In this article, thermally induced phase separation (TIPS) was used for tissue engineering applications and Foams were prepared via TIP using poly-L-Lactic acid (PLLA) and blends of PLLA with PLA.
Abstract: Foams for tissue engineering applications were prepared via thermally induced phase separation (TIPS). Poly-L-Lactic Acid (PLLA) and blends of PLLA with PLA in different proportions were used (100/0, 90/10, 75/25, 50/50, 0/100 PLLA/PLA wt/wt) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection) and the void fraction was measured by means of Hg porosimetry. Foams apparent density was also evaluated (porosity ranges from 87% to 92%). Biodegradability was estimated in a body mimicking fluid. Results show that structure and morphology (in terms of average pore size and distribution, interconnectivity and mechanical properties) depend upon the combination of the operating conditions adopted for the process (polymer concentration, solvent/non-solvent ration, demixing temperature and time). Furthermore, by blending PLLA with PLA it is possible to tune the biodegrability of the foam, thus addressing the possible applications in different fields of soft tissue engineering.
TL;DR: In this paper, the authors address the problem of numerically simulating the Friction Stir Welding (FSW) process using the Natural Element Method (NEM) and present some interesting characteristics such as the ease of imposition of essential boundary conditions and coupling with FEM codes.
Abstract: In this work we address the problem of numerically simulating the Friction Stir Welding process. Due to the special characteristics of this welding method (i.e., high speed of the rotating pin, very large deformations, etc.) finite element methods (FEM) encounter several difficulties. While Lagrangian simulations suffer from mesh distortion, Eulerian or Arbitrary Lagrangian Eulerian (ALE) ones still have difficulties due to the treatment of convective terms, the treatment of the advancing pin, and many others. Meshless methods somewhat alleviate these problems, allowing for an updated Lagrangian framework in the simulation. Accuracy is not affected by mesh distortion (and hence the name meshless), but the price to pay is the computational cost, higher than in the FEM. The method used here, the Natural Element Method (NEM), presents some interesting characteristics, such as the ease of imposition of essential boundary conditions and coupling with FEM codes. Even more, since the method is formulated in a Lagrangian setting, it is possible to track the evolution of any material point during the process and also to simulate the Friction Stir Welding (FSW) of two slabs of different materials. The examples shown in this paper cover some of the difficulties related with the simulation of the FSW process: very large deformations, complex nonlinear and strongly coupled thermomechanical behaviour of the material and mixing of different materials.
TL;DR: In this article, an experimental and numerical study of the TOX- clinching process and its mechanical strength due to different surface conditions (blank, electro galvanized, corrosion protection primer (CPP) coated).
Abstract: This work describes an experimental and numerical study of the TOX®- clinching process and its mechanical strength due to different surface conditions (blank, electro galvanized, corrosion protection primer (CPP) coated). The main purpose of using different types of surface conditions is to analyze their influences on the geometry and mechanical strength of the clinched joint. Finite element analysis (ABAQUSExplicit) is used to model the clinching process as well as the subsequent loading of the joint in the shear and cross tension test. The influence of the plastic anisotropy of the material is analyzed by evaluation of the punch force-displacement curve and the strength of clinched joint under these loading conditions.
TL;DR: In this article, a simulation model is used to study the influence of different grades of strain hardening in a Taylor rolleded Blank on the bulge formation that occurs during the rolling of a rill in this Tailor Rolled Blank.
Abstract: 3D-Strip Profile Rolling should enable the production of blanks with a defined thickness profile in latitudinal and longitudinal direction. The production chain of 3D-Strip Profile Rolling will combine Flexible Rolling in a first production step with Strip Profile Rolling in a second step. The control system to adjust the roll gap during 3D-Strip Profile Rolling is currently under development. Nevertheless, some first experiments have shown the general feasibility to produce 3D-profiled blanks. In 3D-Strip Profile Rolling the material will strain harden differently on different locations. This results in a variation of the material properties of the strip. Lateral spread, elastic roll stand deformation and local deformation will be influenced by this variation. To investigate these influences on the complete production process, the complete production chain needs to be modelled in the future with aid of finite element simulations. In this publication a first simulation model is used to study the influence of different grades of strain hardening in a Taylor Rolled Blank on the bulge formation that occurs during the rolling of a rill in this Tailor Rolled Blank.
TL;DR: In this paper, the results obtained by trying to achieve small diameters holes by electrochemical discharge machining using an aqueous solution of sodium silicate as working liquid were presented.
Abstract: Electrochemical discharge machining (ECDM) is considered to be a hybrid machining method where material removal is based on two phenomena: electrochemical dissolution of the material and thermal erosion by electrical discharges that occur between the electrodes. Obtaining holes of small diameter in hard materials is one challenge also for this machining method. The paper contains some results obtained by trying to achieve small diameters holes by electrochemical discharge machining using an aqueous solution of sodium silicate as working liquid. Identifying an optimized system for mechanical and electrical equipment was one of the targets of this research. By assuring a relative motion between the electrodes, holes (diameter <1 mm) in cutting steel workpieces were obtained.
TL;DR: In this paper, a new cantilever test using optical measurement has been developed to provide the searched flexibility for stiffer and thicker reinforced textiles, and tests have been performed on a carbon woven reinforcement and compared with KES measurements.
Abstract: In shaping of composite reinforcements, tensile stresses are the major stresses, while in plane shear strains are the major strains. However the knowledge of the bending behaviour would give more precisely simulation of forming especially for stiffer and thicker textiles. Two standard tests are used to determine it. The cantilever test is limited because of its elastic linear model. The KES fabric bending test allows a more complicated model but its use is difficult for stiff and thick reinforcements. A new cantilever test using optical measurement has been developed to provide the searched flexibility. Tests have been performed on a carbon woven reinforcement and compared with KES measurements. The results allow to validate the experimentation.
TL;DR: In this article, an Arbitrary Lagrangian Eulerian (ALE) formulation was developed to simulate the different stages of the FSW process with the FORGE3® F.E. software.
Abstract: An Arbitrary Lagrangian Eulerian (ALE) formulation was developed to simulate the different stages of the Friction Stir Welding (FSW) process with the FORGE3® F.E. software. A splitting method was utilized: a) the material velocity/pressure and temperature fields are calculated, b) the mesh velocity is derived from the domain boundary evolution and an adaptive refinement criterion provided by error estimation, c) P1 and P0 variables are remapped. The proposed ALE formulation is applied to FSW simulation. Steady state welding, but also transient phases are simulated, showing good robustness and accuracy of the developed formulation. Friction parameters are identified for an Eulerian steady state simulation by comparison with experimental results. Simulations of the transient plunge and welding phases help to better understand the deposition process that occurs at the trailing edge of the probe, and in particular possible void formation. Flexibility and robustness of the model allows investigating the influence of threads and tooling designs.
TL;DR: In this article, a single-walled carbon nanotubes (SWNTs) polyvinyl alcohol (PVA) composite film was used as a mode-locker in an Er3+ fiber ring laser.
Abstract: We present the fabrication of a high optical quality single-walled carbon nanotubes (SWNTs) polyvinyl alcohol (PVA) composite film. The composites demonstrate strong saturable absorption at ∼1.5 μm, the spectral range for optical communications. By measuring the nonlinear transmission of a sub-picosecond pump pulse through the film, we were able to deduce a saturation fluence of ∼13.9 μJ/cm2 and a modulation depth ∼16.9% (in absorption) at a high pulse fluence ∼200 μJ/cm2. Transient saturable absorption is investigated by measuring the transmitted autocorrelation traces at various incident power levels. Observed side-peak suppression indicates a fast recovery time on the scale of ∼1 ps for our saturable absorber devices. Furthermore, we use these SWNT-PVA composite saturable absorbers as mode-lockers in an Er3+ fiber ring laser and achieve ∼560 fs pulse generation with good jitter performance and long term stability. The laser performance is also associated with the parameters of our SWNT based saturable absorber.
TL;DR: In this article, the variable pressure-time load profile during a superplastic forming process was predicted to get best performances, in terms of ductility, on the material, and the so obtained curve has been used in experimental free bulging tests on an AZ31 magnesium alloy sheet.
Abstract: In this work, an original algorithm, proposed in [1–2], has been used to predict the variable pressure-time load profile during a superplastic forming process, in order to get best performances, in terms of ductility, on the material. The so obtained curve has been used in experimental free bulging tests on an AZ31 magnesium alloy sheet. Tests results, in particular the maximum bulge height achieved by the material, have been compared with numerical results and with constant-pressure experimental tests.
TL;DR: In this paper, the authors investigated the possibility of using an ultrafine grained (UFG) metal for micro-extrusion and compared the extrusion force, grain flow, shape representation and surface quality of the extruded micro-components.
Abstract: Because of the well known virtues of low cost and high productivity, metal forming technology is well suited for mass production of metal micro-components. However, scaling down metal forming processes proves to be problematic because, among other factors, the relatively coarse grain (CG) structure of micro-billets leads to non-uniform material flow and lack of repeatability during microforming. A substantial grain size reduction below one micron should help to prevent these problems. The aim of the presented study is to investigate a possibility of using an ultrafine grained (UFG) metal for micro-extrusion. The material used for this purpose is CP Cu often used for electrical applications. The UFG version of Cu is produced by severe plastic deformation at room temperature using up to 8 passes of equal channel angular pressing. The microstructure and compression properties of the UFG version of the material are tested. The microforming process of backward extrusion is carried out at room temperature using half cylindrical billets. The extrusion force, grain flow, shape representation and surface quality of the extruded micro-components are compared.
TL;DR: In this article, a new developed method described the gear-rolling process and an alternative pitch design of forming tools was created to analyze rolling processes which determined that in contrast to flat rolling tools, round tools for helical gears need additional kinematic compensation during diameter-related variable pitch forming processes.
Abstract: A new developed method describes the gear-rolling-process and an alternative pitch design of forming tools. A model was created to analyze rolling processes which determined that in contrast to flat rolling tools, round tools for helical gears need additional kinematic compensation during diameter-related variable pitch forming processes. The new method shows up to a 50% improvement in pitch accuracy and the ability to roll high teeth gears (up to 10 mm in height and a tooth-height-coefficient larger than 2,7). The Fraunhofer Institute IWU has carried out research for many years to provide insight in generating high gearing typical of transmissions with rolling techniques and surpassing the limits of forming feasibility.