bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Roller Hemming System for High Volume Part Production
Authors: Zubeil Martin , Roll Karl , Merklein Marion
Published: March 2011

Roller hemming is usually applied for hang-on-parts such as hoods, doors or trunk-lids which all have complex non-linear geometries. The flange is often hemmed along both surfaces and edges which have 3D curvilinear shapes. Minimization of hemming defects and the requirement to improve cycle time of the roller hemming process are essential for roller hemmed hang-on-parts in the automotive industry. Different systems such as the driven roller hemming provide the possibility to increase the strain rate without loosing surface quality and dimensional stability. Investigating the influence of friction during roller hemming, results will give an understanding of the advantage for mentioned roller hemming systems.
The Effect of Process Parameters on Thickness Distribution in Hydroforming of Conical-Cylindrical Cups
Authors: Gorji Abdolhamid , Bakhshi-Jooybari Mohammad , Norouzi Salman , Hosseinipour S.J. , Mohammad-Alinejad G.
Published: March 2011

Forming conical parts is one of the complex and difficult fields in sheet metal forming processes. These parts are normally formed in industry by spinning, explosive forming or multistage deep drawing processes. In this paper, forming pure copper conical–cylindrical cups in the hydrodynamic deep drawing process was studied using finite element (FE) simulation and experiment. In this study, the effect of cone angle and punch tip radius on bursting and thickness distribution of the parts and also the effect of pressure path on thickness distribution were examined. Using the measurements of strains and thickness variations on the cup wall, the quality of the drawn cups was evaluated. The results demonstrated that increasing cone angle will lead to higher drawing ratio and uniform thickness distribution. Also, it was concluded that in the conical-cylindrical part the punch tip radius region is the most critical zone. At this zone, the more the cone angle the less the possibility of tearing is. In addition, with increasing punch tip radius it could be seen that the thickness reduction decreases.
Combination of Finite-Element and Semi-Analytical Models for Sheet Metal Leveling Simulation
Authors: Amor Amine , Rachik Mohamed , Sfar Hédi
Published: March 2011

Coiled sheet metal often exhibits shape defects that result from the rolling process or the coiling operation. To meet the quality requirement, these defects need to be removed using leveling and straightening. The process efficiency strongly depends on several parameters like the machine design, the rollers penetration and the sheet metal. Consequently, the leveling process is very sensitive and it is difficult to find the appropriate setting using trial and error procedure. In this context, numerical simulation can be very helpful. The aim of our work is to predict the residual curvature of the sheet knowing its initial shape and the leveling process settings. The simulation is carried out in two steps to integrate the global and the local behavior of the strip along the leveling process. In the first step, a 2D finite element model is used to predict the sheet metal deformations under the rollers action. In this first step the strip curvatures along the leveling machine are predicted. The so obtained results are then used to simulate the alternating bending and the spring back of the strip with the help of a semi-analytical model using the MATLAB programming environment. To validate the proposed approach, leveling tests were carried out on a 2.5 mm thickness sheet of DX51 steel and the measured residual curvatures are compared with the predictions. These comparisons show that satisfactory predictions can be obtained with good computational efficiency.
Characterization of Horizontal Loads in the Production of Asymmetrical Parts
Authors: Behrens Bernd-Arno , Bouguecha Anas , Krimm Richard , Matthias Thorsten , Salfeld Valerian
Published: March 2011

The vision of Transregional Collaborative Research Centre 73 of the German Research Foundation (DFG) is the development of a new manufacturing technology, sheet-bulk metal forming. The research activity is focused on the manufacturing of geometrically complex parts with functional elements from thin sheet metal. This paper gives an overview about the challenges in forming of asymmetrical parts with regard to the forming forces and resulting displacements of the press components. Furthermore, it introduces an appropriate approach for consideration of machine characteristics in order to improve the computational accuracy of the process modelling.
High Performance Active Elements for Agricultural Machines Made of Ultra High-Strength Steels
Authors: Homberg W. , Rostek Tim
Published: March 2011

This article will highlight various aspects of the production process of high performance active elements made of ultra high-strength steels. Focus is put on the processing of thick sheet metal regarding hot forming by means of punching, embossing, and forging processes as well as on thermo-mechanical treatment. Due to the material thickness of the semi-finished parts/blanks used and owing to the high strength of the materials (Rm > 2600 MPa) current production techniques and parameters from the field of thin sheet metal can only be limitedly be transferred and have therefore been specially investigated for this application.
Modelling of Fine Blanking Process of the Aluminium Sheets
Authors: Wieckowski Wojciech , Lacki Piotr , Adamus Janina
Published: March 2011

The required technological quality of the blanked products can be achieved through operations of fine blanking. This allows for obtaining products with improved dimensional accuracy and good quality cut-surface. In order to cut products from soft materials, including aluminium and its alloys, the methods of fine blanking with upsetting and fine blanking with reduced clearance are typically employed. The study presents the results of numerical modelling of the fine blanking process for a disk made of 1-millimetre sheet aluminium EN AW-1070A. The goal of the numerical simulations was to evaluate the effect of clearance between blanking die and the punch, and the impact of V-ring indenter on stress and strain distribution in the shearing zone.
The Effect of Residual Stresses on the Strain Evolution during Welding of Thin-Walled Tubes
Authors: De Strycker Maarten , van Paepegem Wim , Schueremans Luc , Debruyne Dimitri
Published: March 2011

In many applications, negative effects of residual stresses in the material stemming from the production process, are regularly encountered. These residual stresses in cold-rolled steel tubes are mainly due to two mechanisms: (i) the rolling of the flat plate into a circular cross-section and (ii) afterwards closing this section with a weld bead. This research focuses on the residual stresses due to the welding process. In an experimental setup abstraction is made of the real production process of the tube. A finite element model is built of this experimental setup. Validation of the welding simulations is done by comparing the strain evolution in both the experiment and the simulation. In this validation process, sometimes a discrepancy between the measured strain evolution and the one obtained from the numerical analysis is seen. In this contribution it is numerically investigated how initial residual stresses affect the thermal strain evolution in the tube during the welding process. This is done in two ways: firstly an initial stress field in hoop direction, based on the spring back of the tube when cut is taken as the reference state and secondly the stress/strain state after the first weld is used in stead of the virgin material state. The conclusion for both assumptions is that the strain evolution during the welding is affected by the initial stress/strain state of the material.
Analytical and Experimental Evaluation of the Stress-Strain Curves of Sheet Metals by Hydraulic Bulge Tests
Authors: Lazarescu Lucian , Comsa Dan Sorin , Banabic Dorel
Published: March 2011

This paper presents a new methodology for the determination of the biaxial stress – strain curves by hydraulic bulging tests with circular die. In order to validate the methodology, the authors have performed both stepwise and continuous bulging experiments. The pressure, polar height and curvature radius have been measured in different stages of the deformation process or continuously recorded during the test.
Investigation of Influence Parameters on Forming Limit Diagrams of Aluminum Alloy-AA2024
Authors: Celik Gokhan , Kaftanoğlu Bilgin , Karadogan Celalettin
Published: March 2011

Sheet metal forming technology is the keyword for many industries such as aerospace, aeronautics and automobile industries. Customer expectations, quality and safety requirements and market competitions require sheet metal forming operations to be well analyzed before the process to fulfill all these requirements. In this study, combination of FEA (finite element analysis) and mechanical material characterization were used in order to improve sheet metal forming operations while considering cost and quality. On the material characterization side of the studies, simple uniaxial tensile tests were conducted to obtain anisotropy parameters and yield points along different directions and hydraulic bulge test (HBT) was performed to obtain plastic behavior of the material up to 0.7 strains. Deformation measurements were conducted using optical measurement system GOM-ARAMIS while a 60-ton hydraulic press; Zwick/Roell BUP600 was used to deform the sheet part AA2024-0 aluminum alloy. Effects of process parameters, which are initial material thickness, lubrication and punch speed, on sheet metal formability and forming limit diagrams (FLDs) were investigated. On the study of thickness effects, sheet metals those having 0.81mm, 1.27mm and 1.60mm thickness were tested. Punch velocities of 250mm/min, 500mm/min and 750mm/min were used to investigate effect of punch speed on formability of sheet metals. Finally, PTFE (Polytetrafluoroethylene), paraffin lubricated and dry conditions were presented to obtain friction effects. FE analyses were performed to simulate experiments and to obtain friction coefficients of different lubricants. Good correlations were observed between numerical simulations and experimental results.
Adjusting Optimized Material Properties for Tailored Heat Treated Blanks
Authors: Merklein Marion , Nguyen Hung
Published: March 2011

Aluminum alloys have great potential for lightweight construction. In order to achieve an optimized properties distribution for the forming operation and to enhance the formability of aluminum alloys, so called Tailored Heat Treated Blanks (THTB) are developed. In this context, this paper is about the local precipitation hardening of sheet metals for the application of THTB. By using a specific, short-term heat treatment via conductive heating plates the thermal induced hardening of the fast hardenable alloy AA6181PX is quantified and qualified. Considering the processibility of the local precipitation hardening for THTB, a process window for the heat treatment parameters is presented allowing a precise setting of the mechanical material properties.
Experimental Methods for Characterizing of Sheet Metals at High Strain Rates
Authors: Meyer Lothar W. , Abdel-Malek Shawky , Herzig Norman
Published: March 2011

Beside tension tests and measuring of Lankford coefficients (r-values), compression tests on small cubes in the sheet plane over a wide range of strain rates are also performed using special devices. The material behavior under shear loading is measured according to Miyauchi using appropriate equipment with the application of optical measurement of speckle strain field. A biaxial tension/tension stress state can be realized in the layer compression test. Through the compression, shear and layer compression tests, large deformations are reached, which can not be measured in the tension test due to necking. These four test types are performed not only quasi-statically but also quasi-dynamically on a servo hydraulic machine and under impact loading in a drop weight machine and rotary tensile impact tester (flywheel) with a precise measurement of force and displacement to determine the strain rate dependency of the investigated materials. Extra points of the yield loci can be measured in the plane strain tension test using a specimen ratio of B/L ≥ 20.
Assessment of Damage Models in Sheet Metal Forming for Industrial Applications
Authors: Doig Maria , Roll Karl
Published: March 2011

Due to increasing demands to reduce C02-emission and to augment occupant’s safety new modern materials are developed ongoing. Because of relatively low production costs, high strength and simultaneously good formability the advanced high strength steels (AHSS) are applied among others for the lightweight design of body-in-white components in the automotive industry. Their already mentioned properties follow from the presence of mixed mild and hard ferrous phases. Due to this multiphase microstructure of the most AHSS steels, a complex material and damage behavior is observed during forming. The damage grows in a ductile manner during plastic flow and the cracks appear without necking. They are often characterized as the so called shear cracks. The damage predictions with standard methods like the forming limit curve (FLC) lack accuracy and reliability. These methods are based on the measurement of linear strain paths. On the other hand ductile damage models are generally used in the bulk forming and crash analysis. The goal is to prove if these models can be applied for the damage prediction in sheet metal forming and which troubles have to be overcome. This paper demonstrates the capability of the Gurson-Tvergaard-Needleman (GTN) model within commercial codes to treat industrial applications. The GTN damage model describes the existence of voids and they evolution (nucleation, growth and coalescence). After a short introduction of the model the finite element aspects of the simulative damage prediction have been investigated. Finally, the determination of the damage model parameters is discussed for a test part.
Geometrical Modeling of the Sheet Metal Parts in the Incremental Shrinking Process
Authors: Yang Zong Ru , Scherer Daniel , Golle Matthias , Hoffmann Hartmut
Published: March 2011

Shrinking is an incremental forming process and can be carried out using a driving machine, so called “Kraftformer”. It needs an upper and a lower shrinking tool, each of which has two moveable jaws as contact and force transform units. During every forming operation the tools clamp the metal sheet, so that the vertical forces from the upper tool are switched by the leverages inside the tools into the horizontal directions. The moveable jaws are practiced by the horizontal forces to compress the metal sheet. The shrinking of the metal sheet brings out the different three-dimensional forms. As a traditional manual forming method, economical productions can’t be reached for individualized sheet metal parts to achieve the customer’s demands. Hence, it is proposed to automate this forming process to reduce the manual work. The production strategies are to be deduced from the manual shrinking process. A direct way to get them is to simulate the forming process in a FEM-software environment. But within such a FEM-simulation it can take about even one hour only just to finish one forming step. Furthermore, an analytical modeling of the shrinking can’t be realized because of its complex procedures such as variation of contact conditions, material hardening. However, a pure geometric model can be established to demonstrate the change of the 3D-forms of the sheet metal parts. The respective forming parameters can be identified through the experiments. The simulation can take place only in a few seconds. This paper provides general information about the application of the manufacturing method and with it the qualification of shrinking as a manufacturing concept for the production of individualized sheet metal products.
Effect of Friction and Back Pressure on the Formability of Superplastically Formed Aluminium Alloy Sheet
Authors: Wood Paul , Qarni Muhammad Jawad , Rosochowski Andrzej
Published: March 2011

This paper examines the effect of friction and back pressure on the formability of superplastically formed aluminium alloy AA7475 sheet at the temperature of 517 °C. Several experiments with lubrication and back pressure are performed using a simple box shape tool cavity. The coefficient of Coulomb friction between the formed sheet and tool has been determined indirectly using a finite element model to simulate superplastic forming of the box shape. Typical values determined for all lubricant conditions tested are in the range 0.1 < μ < 0.2. The void growth with strain was determined directly from measurements as a function of back pressure. The results show the application of back pressure at 1 MPa reduces the growth of voids from 7% to 0.3% void volume fraction at a logarithmic thickness strain of 0.65. This paper reports back pressure has a significantly greater role than friction in enhancing the formability of the alloy.
Continuous Roll Forming Simulation Using Arbitrary Lagrangian Eulerian Formalism
Authors: Boman Romain , Ponthot Jean Philippe
Published: March 2011

Due to the length of the mill, accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very large mesh leading to huge CPU times. In order to model industrial forming lines including many tools in a reasonable time, the sheet has to be shortened or the element size has to be increased leading to inaccurate results. On top of this, applying loads and boundary conditions on this smaller sheet is usually more difficult than in the continuous case. Moreover, transient dynamic vibrations, which are unnecessarily computed, may appear when the sheet hits each tool, decreasing the convergence rate of the numerical simulation. Beside this classical Lagrangian approach, an alternative method is given by the Arbitrary Lagrangian Eulerian (ALE) formalism which consists in decoupling the motion of the material and the mesh. Starting from an initial guess of the sheet geometry between the rolls, the numerical simulation is performed until the stationary state is reached with a mesh, the nodes of which are fixed in the rolling direction but are free to move on perpendicular plane, following the geometrical boundary of the sheet. The whole forming line can then be modelled using a limited number of brick and contact elements because the mesh is only refined near the tools where bending and contact occur. In this paper, ALE results are compared to previous Lagrangian simulations and experimental measurement on a U-channel, including springback. Advantages of the ALE method are finally demonstrated by the simulation of a tubular rocker panel on a 16-stands forming mill.
Modeling and Optimization of Pressure Profile in Hydroforming of St12 Conic Part with RSM and Genetic Algorithm
Authors: Shahrajabian Hamzeh , Khalili Khalil , Khalili M. Soheil
Published: March 2011

One of the most effective methods of manufacturing conical parts is the hydroforming process. The pressure profile during forming is the most important factor on wrinkling, thinning, and punch wall contact. This paper presents a methodology to determine the optimal profile of hydraulic pressure during hydroforming of conical parts. The objective is to minimize the variation of the thickness throughout the part. Initially, the finite element model is developed and verified. The part being modeled is then subjected to different pressure profiles to examine the effect of each profile on thinning. The Response Surface Modeling (RSM) along with Genetic Algorithm (GA) is employed to obtain the optimum pressure profile. The paper describes the methodology developed and reports the results obtained.
Parametric Investigation of Circular and Elliptical Bulge Tests in Warm Hydroforming Process for AA5754-O Sheet
Authors: Gedikli Hasan , Cora Ömer Necati , Koç Muammer
Published: March 2011

This study numerically investigated the effects of process parameter variations such as blank holder forces (800kN-1200kN), strain rates (0.0013/sec, 0.013/sec, 0.13/sec), coefficient of friction (0.05-0.15), temperature (150 °C, 260 °C) and apex angles (0º, 60º, 90º,120º) on warm hydroforming of AA 5754-O sheet blanks. Warm hydroforming process was simulated through hydraulic bulge test with circular and elliptical die openings. Dome height and sheet thinning were selected as control parameters for formability of AA 5754-O sheet blanks. Results showed that the dome height and formed blank thicknesses did not change significantly with the variation of coefficient of friction and blank holder force. Moreover, increasing forming temperature and non-isothermal conditions yielded slightly better formability. On the other hand, increase in strain rate, and elliptical type of bulge test cavity led to significant decreases in dome height and formed part thinning. Another significant finding was that the elliptical bulge test model and isothermal analyses did not reveal the effect of anisotropy for the sheet material concerned.
Material Hybrid Joining of Sheet Metals by Electromagnetic Pulse Technology
Authors: Schäfer Ralph , Pasquale Pablo , Elsen Alexander
Published: March 2011

Adhesively joining metals of dissimilar melting point represents one of the most sophisticated tasks in joining technique. However, due to light weight considerations this type of joint, for example the connection between an aluminum flange and a high strength steel crash element, is of prior interest. The electromagnetic pulse technology is a proven process to accomplish adhesive joints between tubes made of dissimilar metals. Recent developments of the technique now allow welding even dissimilar and similar sheet metals under industrial conditions. This paper details the underlying mechanisms and shows a variety of samples, depicting for the potential of this new process.
Modeling Uniaxial, Temperature, and Strain Rate Dependent Behavior of AZ31 Alloy by Softening Model
Authors: Toros Serkan , Ozturk Fahrettin , Kaya M.
Published: March 2011

In the present study, a softening model proposed for warm forming behavior of Al-Mg alloys is applied to AZ31 alloy in order to determine the applicability of the model to magnesium alloys AZ31 alloy is tested at several temperatures (room temperature to 300 oC) and strain rates (0.0083-0.17 s-1). The results indicate that the model shows good agreement with experimental flow curves for different temperatures and strain rates for AZ31 alloy.
FEM Analysis of Sandwich Shells with Metallic Foam Cores
Authors: Mata H. , Natal Jorge Renato , Fernandes A.A. , Valente Robertt , Parente M.P.L.
Published: March 2011

Traffic-related accidents are a major threat to life in the European Union, plus all the associated social and economic costs, remain unacceptable. It is generally considered that the number of traffic-related accidents is an unacceptable high burden for Europe´s society and economy. World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new energy absorbing materials. In this field, passive safety systems still have great potential to reduce fatalities and injuries, as in the case of using new lightweight energy-absorbing materials. The main goal of this project is the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications, especially in automotive and aeronautical industries. In this work, we first made an approach to analyze sandwich shells with metal cores forms. To this end we used a numerical model based on the finite element method using commercial software ABAQUS.
Blank Optimization in Elliptical-Shape Sheet Metal Forming Using Response Surface Model Coupled with Reduced Basis Technique and Finite Element Analysis
Authors: Khalili Khalil , Kahhal Parviz , Shari Ehsan Eftekhari , Khalili M. Soheil
Published: March 2011

The present study aims to determine the optimum blank shape design for the deep drawing of Elliptical-shape cups with a uniform trimming allowance at the flange i.e. cups without ears. This earing defect is caused by planar anisotropy in the sheet and the friction between the blank and punch/die. In this research, a new method for optimum blank shape design using finite element analysis has been proposed. Present study describes the approach of applying Response Surface Methodology (RSM) with Reduced Basis Technique (RBT) to assist engineers in the blank optimization in sheet metal forming. The primary objective of the method is to reduce the enormous number of design variables required to define the blank shape. RBT is a weighted combination of several basis shapes. The aim of the method is to find the best combination using the weights for each blank shape as the design variables. A multi-level design process is developed to find suitable basis shapes or trial shapes at each level that can be used in the reduced basis technique. Each level is treated as a separated optimization problem until the required objective – minimum earing function – is achieved. The experimental design of RSM method is used to build the approximation model and to perform optimization. MATLAB software has been used for building RSM model. Explicit non-linear finite element (FE) Code Abaqus/CAE is used to simulate the deep drawing process. FE models are constructed incorporating the exact physical conditions of the process such as tooling design like die profile radius, punch corner radius, etc., material used, coefficient of friction, punch speed and blank holder force. The material used for the analysis is Stainless steel St12. A quantitative earing function is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. So through the investigation the proposed method of optimal blank design is found to be very effective in the deep drawing process and can be further applied to other stamping applications.
DOE Analysis of the Effects of Geometrical Parameters on the Self-Piercing Riveting of Aluminium Alloy AA6060T4
Authors: Casalino Giuseppe
Published: March 2011

The design of experiments (DOE) is a very useful tool to design and analyze complicated industrial design problems. They help to understand the variability a manufacturing process by investigating which parameters and their interaction mainly affect the output repeatability. As a consequence, it enables to individuate the combination of parameters that optimize the output avoiding misinterpretation that can be due to the singularity of the experimental data. In this study the factorial analysis was used to investigate the effects of the major geometrical parameters on the shape of the force-displacement curve of the self piercing riveting (SPR) process. A full two level three-factorial design (23) was completed, three-way interaction was not considered. The statistical analysis was carried out at four different points of the force-rivet displacement curve. These points can be considered critical since they limit the four steps in which the process is commonly divided for studying purpose. The experimental data did not fulfil the required design points, the missing points were obtained by a finite element model of the riveting process, which furnished the force versus the rivet run.
A Holistic Modeling Approach for the Design of Tension Leveling and Scale Breaking Processes and Equipment
Authors: Steinwender Lorenz , Salzmann Christoph , Kainz Alexander , Krimpelstätter Konrad , Zeman Klaus
Published: March 2011

Tension leveling is employed as one of the final processes in continuous galvanizing and finishing lines in order to improve strip flatness and minimize residual stresses. Scale breaking is normally located at the entry of continuous pickling lines to break the scale layer on the hot strip surface and to improve strip flatness. In both applications, the strip is bent under high tension around multiple rolls with small diameters whereby small elasto-plastic strains are induced, leading to plastic dissipation and significant tension losses at the typically undriven process rolls. To improve the process design as well as the equipment layout of tension levelers, precise simulation models are essential. Extensive analyses of the tension leveling process (employing commercial FEM-packages) have led to a comprehensive understanding of the underlying physical effects and correlations. In order to reduce the extensive computational costs of FEM models (while assuring high significance of results), an alternative and new modelling approach based on the principle of virtual work and parametric shape functions (PSF) for curvature and strain distributions was employed. Compared to optimized (Lagrangian) FEM models, the new tailor-made PSF model (based on a specific Arbitrary Lagrangian-Eulerian formalism) allows a drastic reduction of degrees of freedom and computational costs, while the key process results (e.g. tension level and tension loss, strip bending line, plastification, global strain level, etc.) show high agreement with those obtained from FEM-models. Following a holistic, mechatronic modeling strategy, these process results can be easily transferred to a generic model for the analysis of various drive concepts.
Employment of Finite Element Modelling and Design of Experiments to Investigate the Geometrical Factors in T-Type Bi-Layered Tube Hydroforming
Authors: Alaswad Abed , Olabi Abdul Ghani , Benyounis Khaled Y.
Published: March 2011

In the last years many researchers were concentrating to develop and design new unconventional metal forming processes. Among such new technologies, tube hydroforming was proved as one of the most promising. Geometry of the tube and die were found to have significant effects on the hydroformed part. In this work, Response surface method was used based on data provided by Finite element modeling to construct a model for the bulge height as a function of geometrical factors for T-type bi-layered tube hydroforming. Interaction effects were analyzed and discussed.
Continuous Improvement of Manufacturing Systems with the Concept of Functional Periodicity
Authors: Matt Dominik T. , Rauch Erwin
Published: March 2011

To compete effectively in the dynamic global marketplace, manufacturing companies have to maintain a high level of responsiveness to remain competitive. This paper presents a theoretic framework for the installation of mechanisms in order to control the effects of the time-dependent combinatorial complexity caused by the uncertainty of maintaining the fulfillment of once defined functional requirements for a manufacturing system. Inspired by the idea of a system that automatically detects, diagnoses, and repairs identified areas of inefficiency, the objective of this research is to find mechanisms that anticipate market or environmentally driven events and help to set up the manufacturing system in advance in order to maximize total system efficiency. The paper builds on previous research about system complexity and on recent findings of a research project conducted in an Italian manufacturing company. Starting from the overall objective of “enhanced survivability” for the company and its manufacturing system, functional system requirements are deducted mapping between functional and system design domain, first on a time-independent basis. With the help of the scenario-technique, time-dependent influence is shown and improvement strategies are developed, using functional periodicity as a trigger point for their release. The first results from practical application show very promising results which will be discussed in the paper.
Experimental Investigation of Parameters Effect on Laser Forming Productiveness
Authors: Lambiase Francesco , Paoletti Alfonso , di Ilio Antoniomaria
Published: March 2011

In the present study the deformation behaviour of thin steel sheets processed by using laser forming has been investigated as well as the temperature distribution along the sheet thickness. A campaign of experimental tests has been carried out on stainless steel AISI 304 in order to evaluate the influence of the main process parameters, such as laser power, scanning speed and sheet thickness on the bending angle and temperature of upper and lower surfaces. In addition, in order to prevent oxidation, the optimal interval duration between two consecutive scans has been assessed. A productivity index has been also introduced in order to evaluate the effectiveness of different process parameters configuration.
Design for Manufacture Based on an Integrated Product Process Design Model
Authors: Voswinckel H. , Schleifenbaum Heinrich , Bambach Markus , Hirt Gerhard
Published: March 2011

This paper details an integrated product process design model that represents process capabilities by a set of key indicators and allows for the design of products taking into account constraints set out by the process. The model is applied to Incremental sheet forming (ISF) processes and their variants. ISF processes have been developed over the past 20 years and have reached a state of development now allowing for a transition from scientific research to broader industrial application. ISF with its low part specific tooling represents a technology suitable for individualized production down to one-piece-flow. Hence, it might satisfy the growing demand for individualized products in the field of sheet metal production. However, an industrial use of ISF requires that general design rules are provided to designers to enable designs that are compatible with the capabilities of ISF. Today’s product design typically is more suitable for stamping operations than for ISF which makes the fabrication of parts by ISF difficult and increases lead time and costs. Also, different variations of ISF processes exist that are based on different machines (industrial robots, CNC machines,…) and are characterized by different capabilities, e.g. in terms of accuracy. The objective of this work is the development of an integrated product process design model and its application to ISF. The capabilities of currently available ISF processes are determined and compared to the requirements of selected products from the automotive and aero-space industry.
Impact of Laser-Based Technologies in the Energy-Consumption of Metal Cutters: Comparison between Commercially Available Systems
Authors: Oliveira Marta , Santos João P. , Almeida Fernando G. , Reis Ana , Pereira João P.G.T. , Barata da Rocha Augusto
Published: March 2011

This paper introduces a framework for the Ecodesign of sheet metal cutters, which targets the definition of a set of design guidelines for this type of machine-tools, based on the contribution of the main equipment sub-systems to the processing and environmental impacts associated to their electrical energy consumption. A comparative study of commercially available Laser cutting equipments, using CO2 or doped fiber as the energy source, is described. Two parallel analysis of electricity consumption have been carried out: (1) the observation of CO2-Laser cutters usage, production modes and work conditions in real industrial environments, and (2) a comparison between these and a Fiber-Laser equipment, for a similar work order (material and thickness). The specific process energy with the different equipments was calculated, and confirms the importance of alternative technologies and practices for the energy efficiency of machining processes.
Heuristic-Based Evaluation of Energy Flows in Press Hardening Process Chains
Authors: Neugebauer Reimund , Schieck Frank , Göschel Angela , Schönherr Julia
Published: March 2011

Energy and resource efficiency is a pressing issue for technological markets in the 21st century. In the field of production technology the development of energy and resource efficient processes and process chains is of particular importance. In order to meet these needs sustainable methods and standards have to be developed. This paper presents a new procedure to calculate and evaluate the energy and resource efficiency of process chains. The method consists of 4 stages that proceed from the real world to the quantitative calculation and qualitative evaluation of material and energy flows. The method is explained and validated using press hardening process chains as an example. The procedure enables the user to systematically capture and structure the press hardening process chain and subsequently develop a comprehensive model of the whole process chain. As a result, it allows to calculate the energy requirements for each stage of the process chain, and later on the process chain as a whole. The intention of the developed procedure is to provide a tool to detect the most energy efficient variant from a range of possible process chains.
Sheet-Bulk Metal Forming of Preformed Sheet Metal Parts
Authors: Schneider Thomas , Merklein Marion
Published: March 2011

Due to ecological and economic challenges there is a rising demand on closely-tolerated complex functional components. Regarding short process chains and improved mechanical properties conventional forming processes are often limited. A promising approach to meet these requirements can be seen in the combination of traditional sheet and bulk metal forming processes, to form sheet metals out of the sheet plane with typical bulk forming operations. The challenge of applying conventional bulk forming operations on sheet metal is the interaction between regions of high and low deformation, which is largely unknown in literature. To analyze this topic fundamentally, a process combination of deep drawing and upsetting is developed for manufacturing tooth-like elements at pre-drawn cups. To fully understand material flow out of the sheet plane into the tooth cavity and to identify and qualify process factors depending on the functional elements´ geometry and friction, a single upsetting stage forming a simplified model of the blank is virtually analyzed with finite-element simulation. By inhibiting the forming history of the pre-drawn blank, the upsetting process can be investigated without interactions with a previous deep drawing operation.
Force Modeling in Single Point Incremental Forming of Variable Wall Angle Components
Authors: Pérez-Santiago Rogelio , Bagudanch Isabel , Garcia-Romeu Maria Luisa
Published: March 2011

Prediction of forming forces in Incremental Sheet Forming (ISF) is specially important in the case of using adapted machinery not designed for the process. Moreover, forming force is an important indicator that can be monitored on-line and utilized for real time process control. Besides experimentation, simulations based on the Finite Element Method (FEM) have been utilized as a reliable source of process force data. Nevertheless, the long solution times required to simulate ISF renders difficult its inclusion into a process optimization chain. In consequence, models that predict the forces required to manufacture simple parts have appeared. This work begins with a review of forming force models available for Single Point Incremental Forming (SPIF). Then, an equation recently proposed in the literature is compared with published experimental results of SPIF under different working conditions. The same data is employed to verify our own FEM simulations. Finally, the above-mentioned formula and FEM simulation were applied to predict the forming force of Variable Wall Angle (VWA) geometries where available force information is limited. Besides the applicability assessment of the equation, results will supplement a future experimental campaign focused in modeling geometries of intermediate complexity level by means of Computational Intelligence methods.
Tool Directionality in Contour-Based Incremental Sheet Forming: an Experimental Study on Product Properties and Formability
Authors: Eyckens Philip , Vanhove Hans , Van Bael Albert , Duflou Joost R. , van Houtte Paul
Published: March 2011

The Incremental Sheet Forming (ISF) process offers a large variety in tool path strategies to obtain a particular final product shape. As fundamental understanding of the relevant deformation modes in ISF is growing, the selection of the tool path strategy may be shifted from trial-and-error towards more fundamentally based knowledge of the process characteristics. Truncated cones and pyramids have been fabricated by both unidirectional (UD) and bidirectional (BD) contour-based tool path strategies, considering different wall angles and materials (Mn-Fe alloyed aluminum sheet and low carbon steel sheet). It is shown that the induced through-thickness shear along the tool movement direction is clearly non-zero for UD, in which case the sense of tool movement is the same for all contours, while it is close to 0 for BD, due to the alternating tool sense during consecutive contours. Furthermore, the heterogeneity in product thickness, as observed for the UD strategy in [1,2], is avoided by using the BD strategy. It is verified that this difference in deformation may affect the mechanical properties in the walls of pyramids by means of tensile testing, but the results are material-dependent. For the aluminum alloy, the re-yield stress along the tool movement direction is smaller for BD in comparison to UD, and the fracture strain in large wall angle products is higher. For the steel, no statistically significant differences in mechanical properties between UD- and BD-processed parts are observed. Finally, for both materials a (slightly) higher limiting wall angle has been repeatedly measured using the BD tool strategy. In light of these results, the bidirectional tool path strategy is to be preferred over the unidirectional one, as thickness distribution and formability are more favorable, while both strategies require similar resources and processing time.
Comparison between SPIF with Robot and CNC Machine
Authors: Attanasio Aldo , Ceretti Elisabetta , Giardini Claudio , Antonioni Silvio
Published: March 2011

This paper deals with Incremental Sheet Forming (ISF) a sheet metal forming process that knew a wide development in the last years. A lot of experimental and simulative researches have been conducted in this field with different aims: to study the sheet formability and part feasibility; to define models able to forecast the final sheet thickness; to understand how the sheet deforms and how formability limits can be defined. Another very important issue is related with the tool path optimization. In fact, the process is characterized by high springback which causes dimensional defects. When IF is performed by a robot, the capabilities of the technology is improved in terms of obtainable shapes (it is possible to use the 6 degrees of freedom of the robot), but the shape errors seem to be higher due to the lower robot stiffness in comparison with CNC machine. In this work the comparison between two different ISF configurations, tool mounted on a CNC machine or tool mounted on a robot, is reported. A suitable geometry was investigated working different sheet material types and sheet thicknesses. The results in terms of geometrical accuracy and sheet deformation have been analyzed in order to define advantages and disadvantages of these two techniques. An analysis on the process forces has been carried out too.
Deviations between FE Simulation and Experiments in the SPIF Process
Authors: Vasilakos Ioannis , Gu Jun , Vanhove Hans , Sol Hugo , Duflou Joost R.
Published: March 2011

Single Point Incremental Forming (SPIF) is a modern and flexible alternative to traditional forming techniques. It thanks its flexibility to the fact that it does not require a dedicated tool set to operate. Numerical simulation of the SPIF process requires an accurate FE model. In the past several attempts have been undertaken to use inverse methods for sheet metal SPIF material model identification based on shearing, tensile and indenting tests. The basic idea of this paper is that the results of inverse methods can be improved by using the SPIF process itself as experimental data source. A SPIF experiment dedicated for material identification on a simple geometry using large step sizes is presented and compared with the FE simulation of the forming process based on an initial guess for the material behavior.
Counter Laser Treatment for Recovering Deformation of Slender Workpiece
Authors: Giorleo Luca , Ceretti Elisabetta , Giardini Claudio , Previtali Barbara
Published: March 2011

Laser hardening, compared to other surface hardening processes, presents several advantages: it can be extremely selective and almost without distortion, it achieves higher levels of hardness and thanks to the rapidity of the heating phase it does not require a quenching medium as the material surrounding the heated layer acts as a heat sink. Nevertheless, in case of workpiece with slim geometry, the thermal stress after the treatment induces a sensible deformation on the treatment direction; this deformation can deeply affect the part ability to fulfil its function and/or its reliability. In this paper a solution to recover the workpiece function ability is presented: a second laser treatment (called counter treatment) was executed on the opposite surface of the treated one to reduce the deformation induced by the first treatment. A numerical model was firstly tested and then used to simulate the counter treatment process and to evaluate the optimum process parameters. Based on the numerical analysis, experimental results show that thanks to this technique it is possible to recover up to 80% of the induced deformation.
Investigation of the Hole Shape in Pulsed Fiber Laser Microdrilling of Nanostructured Titanium
Authors: Biffi Carlo Alberto , Previtali Barbara
Published: March 2011

The request of small features resulting from high productive and good quality processes has been growing in several industrial fields, such as micromechanical, microelectronic and biomedical sectors. In conjunction with this demand from industries, innovative laser sources such as pulsed fiber lasers, are becoming the answer to the machining of innovative and hard to process materials, such as the nanostructured metallic alloys. The pulsed fiber lasers indeed offer a very precise and small dimension tool able to work with high productivity and small thermal alteration, which is of fundamental importance when nanostractured alloys are machined. In this work an experimental study on percussion microdrilling of 0.7 mm thick nanostructured titanium sheets by means of a nanosecond pulsed fiber laser was performed. In particular, the entrance and exit hole quality as well as the shape of the inner hole were investigated as a function of pulse frequency and process time. The drilling time was firstly measured by means of a couple of fast infrared photodiodes. Then, the effect of the process time, immediately before and after the measured drilling time, and pulse frequency on the hole geometry was investigated. Moreover, the evolution of the machined holes as a function of the process time was discussed.
Geometrical Control of 3C and 6H-SiC Nucleation on Low Off-Axis Substrates
Authors: Jokubavicius Valdas , Liljedahl Rickard , Ou Yi Yu , Ou Hai Yan , Kamiyama Satoshi , Yakimova Rositza , Syväjärvi Mikael
Published: March 2011

Growth of 3C or 6H-SiC epilayers on low off-axis 6H-SiC substrates can be mastered by changing the size of the on axis plane formed by long terraces in the epilayer using geometrical control. The desired polytype can be selected in thick (~200 µm) layers of both 6H-SiC and 3C-SiC polytypes on substrates with off-orientation as low as 1.4 and 2 degrees. The resultant crystal quality of the 3C and the 6H-SiC epilayers, grown under the same process parameters, deteriorates when lowering the off-orientation of the substrate.