Institute for Production Engineering and Forming Machines

Darmstadt, Germany

Institute for Production Engineering and Forming Machines

Darmstadt, Germany
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Mahajan P.,Institute for Production Engineering and Forming Machines | Taplick C.,Institute for Production Engineering and Forming Machines | Ozel M.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
IOP Conference Series: Materials Science and Engineering | Year: 2016

The bending of linear flow split profiles made up of high strength materials involves high bending loads leading to high springback and geometrical defects. In addition, the linear flow split profiles are made stronger due to the high plastic deformation applied by the process itself. The bending method proposed in this paper combines the linear flow splitting process with a movable bending tool. The aim of the research was to investigate the effect of superimposed stresses exerted by the linear flow splitting process on bending load and springback of the profile by using a finite element model. The latter was validated by means of experimental results. The results show that the bending loads and the springback were reduced by increasing the superposition of stress applied by the linear flow splitting process. The reduction in the bending loads leads to a reduction in the cross-sectional distortion. Furthermore, the springback was compensated by controlling the amount of superimposed stress. © Published under licence by IOP Publishing Ltd.


Traub T.,Institute for Production Engineering and Forming Machines | Chen X.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
International Journal of Mechanical Sciences | Year: 2017

Roll forming is a widespread method for manufacturing cold rolled profiles. Increasing requirements regarding tolerances challenge existing procedures for designing roll forming processes. For instance, despite a large number of calculation methods, a reliable prediction of the initial sheet width has not been possible yet. The initial sheet width is crucial for the product quality since this dimension influences the lengths of the legs of the profile directly and thus the tolerances being achievable. Furthermore, with respect to the thickness reduction of profiles due to lightweight design and the use of high strength steels, the reliable prediction of the additional thinning of the profile during the roll forming process in the bending zones is gaining more and more importance. Presently, there is no feasible approach providing detailed information on the strain distribution and thus the thickness reduction in the bending zone during roll forming processes without significantly delaying the planning process. Therefore, this study presents a numerical modelling approach combining global and submodels enabling a high resolution of the strain distribution in the bending zone at acceptable computational costs. The application of the validated numerical model proves in good accordance with experimental results that the profile geometry (U-channel versus C-profile) and the bending ratio (bending radius divided by sheet thickness) are the main factors of influence on the strain distribution in the bending zone. © 2017 Elsevier Ltd


Groche P.,Institute for Production Engineering and Forming Machines | Huttel D.,Institute for Production Engineering and Forming Machines | Post P.-P.,TU Darmstadt | Schabel S.,TU Darmstadt
Production Engineering | Year: 2012

The material behavior of two different types of paperboard was characterized in tensile tests and in a new test device called paperboard bulge test. A particularly adapted hydroforming process was used to produce three-dimensional paperboard structures. Furthermore, an online measurement device to describe the mold-filling behavior is introduced. The experimental results were compared to the results obtained with an FEA investigation. The investigations showed the possibilities of the new forming process, as well as the advantages of FEA methods used to pre-define the process parameters. © 2012 German Academic Society for Production Engineering (WGP).


Scheil J.,Physical Metallurgy PhM | Muller C.,Physical Metallurgy PhM | Steitz M.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Key Engineering Materials | Year: 2013

Deep Rolling and Machine Hammer Peening are mechanical surface treatments which generate hard surfaces due to cold working accompanied by the induction of compressive residual stresses. Both processes can be controlled by a variety of parameters. Up to this point, it is unclear which parameters should be used to generate hard surfaces. This paper gives a statistical approach to close this gap. Four different materials, containing 1.2379, GP4M, EN-GJL-250 and EN-JS2070, are tested using brinell hardness measurement and for each material every machining parameter is investigated. In addition an approach is given why a large ball diameter in deep rolling results in a higher hardness than a small diameter using a kinematic isotropic material FEM model of 1.2379. Copyright © 2013 Trans Tech Publications Ltd.


Ludwig M.,Institute for Production Engineering and Forming Machines | Muller C.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Key Engineering Materials | Year: 2010

Tribology plays an important role in sheet metal forming processes relating to near net shape production processes and achievable surface qualities. Nearly every process is realized by using characteristic lubricants affecting the tribological system to achieve the desired results. Deterministic structures on sheet surfaces can result in less friction and higher drawing ratios. This is caused by hydrostatic pressures build up in closed lubricant areas and hydrodynamic pressures due to the lubricant motion especially in thin fluid films [1, 2, 3]. Friction mechanisms in the mixed lubrication regime are not fully understood till today. The numerical simulation of flows in lubricant pockets and their influence on surface evolution are promising ways to gain more knowledge of the lubricant behavior in tribological systems. Therefore, this paper shows results of combined numerical and experimental approaches. The described simulations of closed lubricant pockets on surfaces identify influencing parameters. Strip drawing experiments are done to verify the simulations. The influence and the importance of local pressures due to viscous effects in the lubricant are considered as well as the necessity to use fluid-structure-interactions to simulate the behavior of lubricants in the tribological system. © (2010) Trans Tech Publications.


Ubelacker D.,Institute for Production Engineering and Forming Machines | Hohmann J.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Advanced Materials Research | Year: 2014

New approaches in lightweight design require the use of multi materials like metal-polymer-metal composites. Composite materials, especially so-called sandwich panels, offer the possibility to combine properties of different materials synergistically. Shear cutting is one of the commonly used manufacturing processes. However, conventional shear cutting of sandwich panels leads to characteristic types of failure, such as high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material. To develop an understanding of the cutting mechanism the cutting force requirement and the failure progress for shear cutting of metal-polymer-metal composites is studied. A lubricant free shear cutting process is used to prevent an absorption of the lubricant by the composite. Two industrial used thermoplastic polymers, an aluminium sheet an unalloyed steel sheet are combined in order to create different composite materials. Furthermore, the composite materials are cut stepwise to examine the different stages of a cutting process in detail. © (2014) Trans Tech Publications, Switzerland.


Muller C.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Tribologie und Schmierungstechnik | Year: 2014

Cold forging is a highly efficient process for the production of high quality components, even though high tribological loads may occur. Hence, complex tribological systems are essential, which have to be analyzed and refined constantly. Therefore tribometers are used. This paper introduces the necessity, the aims and the tasks of tribometers. Furthermore, certain demands, such as the representable tribological loads, the homogeneity in the contact area, the usability and the flexibility are discussed. This is necessary in order to evaluate tribometers and their applicability in cold forging. The paper at hand focuses on the examination of common tribometers used in cold forging. The topic will be completed with a survey of parameters influencing the friction coefficient, which were analyzed by the Sliding Compression Test.


Groche P.,Institute for Production Engineering and Forming Machines | Vogler F.,Institute for Production Engineering and Forming Machines | Wiessner L.,Institute for Production Engineering and Forming Machines
Production Engineering | Year: 2015

Components with large cross section differences and complex geometries are not or only hardly produceable using conventional hydroforming processes at room temperature. In order to overcome this difficulty, the combination with other forming processes is promising. In the present paper a process chain consisting of rotary swaging followed by a subsequent hydroforming is examined. Local material data such as flow stress and forming limits of the preform are characterized. Kinematic hardening is found out to be the predominant material behavior. Hence, appropriate control curves for hydroforming were designed via locally assigned material data in numerical simulations. A complex geometry is thus formed with the presented process chain. It is shown that high forming ratios of preformed areas are achievable when compressive stress is superimposed by axial feeding. © 2015 German Academic Society for Production Engineering (WGP)


Stein P.,Institute for Production Engineering and Forming Machines | Ubelacker D.,Institute for Production Engineering and Forming Machines | Holke D.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Materials Science Forum | Year: 2015

Continually increasing exhaust emission standards for automobiles and an increasing environmental awareness push design engineers to develop new constructive and material concepts. So-called sandwich panels, consisting of stiff facings and light-weight cores, offer the possibility to combine properties of different materials synergistically. When processing large quantities, as is the case in the automotive industry commonly used manufacturing processes for cutting sandwich panels, like sawing or milling, are not applicable. A common manufacturing process to cut metal sheets in high quantities is shear cutting. However, pre-trials of shear cutting of sandwich panels have shown that it is not possible to achieve flawless cutting surfaces with current process layouts. Characteristic types of failure like high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material were ascertained. Thus, in this study, the influence of cutting parameters, such as the clearance and the punch diameter, on these types of failure is examined. Five different clearances between 0.025 mm and 0.4 mm with two punch diameters, 8 mm and 32 mm, were investigated. In order to compare the influence of different materials, three commercially available sandwich panels were studied. The chosen sandwich panels differ both in the face sheet thickness and the core material. Finally, the shear cutting force is measured to identify a possible correlation between the cutting force and the face bending. As a result, optimal clearances to minimize the face bending are derived. Additionally, the influence of the core stiffness on the cutting force is determined. © (2015) Trans Tech Publications, Switzerland.


Brenneis M.,Institute for Production Engineering and Forming Machines | Groche P.,Institute for Production Engineering and Forming Machines
Advanced Materials Research | Year: 2014

Smart structures consisting of a load carrying structure and smart materials with actuatory and sensory capabilities feature high potential in numerous applications. However, to master the assembly conditions of smart structures, there is a need to integrate additional design parameters such as prestress of the smart material, critical loads and electric contacting as well as insulation into the process development. This paper focusses on the design of an incremental bulk forming process to integrate piezoceramic components into an aluminum tube simultaneously to the manufacturing process. Axial forces imposed on the piezoceramic are investigated numerically and experimentally to verify the design of critical components and the process control. Within this investigation, in situ measurement of the direct piezoelectric effect provides a method to validate the numerical design with regard to failure of the piezo tube and the functional properties of the overall structure. © (2014) Trans Tech Publications, Switzerland.

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