Due to the potential of forming induced residual stresses to influence component properties, a deeper understanding of the mechanisms of residual stress generation and stability is required. Therefore, the approach to the research project is structured into the phases of component manufacturing (generation of residual stresses), component operation (residual stress stability) and process design (exploitation of residual stresses). As reference process the forward rod extrusion is used, which is established as standard process in industrial use. Due to the trend towards component materials with higher strength and corrosion resistance, two stainless steels are used in the project. The investigations include parallel experimental and numerical analyses of the process and its synthesis.
During the first phase, the necessary experimental equipment for component manufacture and testing was set up, material and friction parameters were identified, components were formed under consideration of different parameter variants and their residual stresses were determined by X-ray diffraction. In a complementary approach, macroscopic finite element models with subroutines for an extended post-processing of residual stresses were developed on the simulation side and applied in the context of numerical parameter variations. Furthermore, differential geometric and continuum mechanical relationships of residual stresses were investigated and the material modelling was extended to crystal plasticity. The predictivity of the numerical results was quantified on the basis of experimental results.
The second phase concentrates on the residual stress stability in component use and the process robustness during component manufacture. The knowledge gained will be used at the end of the second and in the third phase to specifically influence the operating behaviour and to control the cyclic strength.
The objective in the second phase is the experimental and numerical determination of the mechanical and thermal residual stress stability. As a requirement for the targeted influencing, relevant parameters will be identified. These cause-and-effect relationships are to be plausibilised by means of fundamental physical effects, whereby a recourse is made to effects described in the literature and numerical methods for the derivation of basic model ideas. Based on the experience gained so far, fluctuations of input variables and previously known disturbance variables are to be taken into account in all investigations. A further prerequisite for a systematic investigation of the fundamental mechanisms relevant to residual stresses is an increase in the numerical modeling and prediction accuracy of the deformation-induced residual stresses. In analogy to the generation phase, a constant comparison of simulation and experiment is therefore also carried out in the operating phase in the sense of an assessment of the prognosis quality of the numerical approaches and the plausibility of the experimental laboratory results.
The Project is part of the DFG priority programm SPP2013 "Targeted Use of Forming Induced Internal Stresses in Metal Components". Within the priority program, the subproject takes part in the expert groups Production technology (thick-walled) and Mechanics and simulation.
Research projects
„Grundlegende Untersuchungen zur Herstellung von Funktionsbauteilen vom Band“
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
The applicationof bulk forming processes to sheet metal, also known as sheet-bulk metalforming, extends the existing forming limits of established sheet and bulkforming processes. This enables the resource-efficient production offunctionally integrated lightweight components. In previous research, sheet-bulkmetal forming of pre-cut blanks was investigated. By using coil assemi-finished products, the advantages of manufacturing from coil in terms ofsimplified component handling and as a result higher output quantity arecombined with the advantages of sheet-bulk metal forming in terms of extendedforming limits.
The usage ofcoils, however, results in an anisotropic material flow and consequently an unequalshape of the formed components. This worsens the component application behaviorand is especially a challenge for cyclically symmetrical parts. In additionasymmetrical tool loads, critical for fatigue, occur. Considering this, theobjective is to elaborate a process understanding for extrusion of gears fromcoil. It should be investigated how the anisotropic material flow affects the formingof the individual functional elements of cyclically symmetrical components andthe tool loads.
In order to increasethe application potential of extrusion of gears from coil, another objective isto provide measures to reduce the anisotropic material flow and to improve thegeometrical accuracy of formed parts. For this purpose, different approaches formaterial flow control, such as adjusting the coil width, feed width, toolgeometry and local adaptation of friction should be analyzed for cyclicallysymmetrical parts. In addition to the effectiveness, the wear-behavior of the measureshas to be investigated in tool life tests.
In-situ characterization of a locally carburized complex phase steel for manufacturing of tailored semi-finished products
(Third Party Funds Single)
Funding source: Deutsche Forschungsgemeinschaft (DFG)
Reduction of local tool stresses in cold forging tools
(Third Party Funds Single)
Funding source: Bayerische Forschungsstiftung
Part geometry is a major influence on the formation of local stress in cold forging tools. Non-constant asymmetrical cross-sections result in axial and tangential stress concentrations. This challenge can be seen in the processes of the industrial partners, where fatigue failure occurs in local elements. In order to counteract fatigue and improve process economics, the formation of local tool stresses is to be analysed using a model process. Using the process the influence of functional elements and changes in cross-section on the stress state of the die is researched. With an understanding of the mechanisms of the stress formation, adapted tool concepts will be developed, which enable a suitable improvement of the stress state depending on the part and tool geometry. To evaluate the effectiveness of the new tool designs, they will be implemented in the processes of the industrial partners. That way, the effect on tool life can be analysed for different die materials. These are usually cold working steels or cemented carbides, which react very sensibly to tensile stresses. Finally, the new tool concepts will be evaluated using the developed process understanding and the experimental results regarding the tool life.
Enhancement of joinability and joint characteristics in mechanical joining processes by tailor heat-treated aluminium semi-finished products
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Friction reduction in lubricated tribological contacts by micro textured surfaces
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Development of a forming process to manufacture near-net-shape functional components with a gradient in sheet thickness
(Third Party Funds Group – Sub project)
Term: 1. January 2021 - 31. December 2022
Funding source: Deutsche Forschungsgemeinschaft (DFG)
Laser implantation of press hardening tools to influence the tribological and thermal properties for the process application
(Third Party Funds Single)
Funding source: Deutsche Forschungsgemeinschaft (DFG)
Resource-minimized production through hybrid and highly networked processes
(Third Party Funds Single)
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)
Hydroforming of high-strength aluminium alloys
(Third Party Funds Single)
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi), AIF Arbeitsgemeinschaft industrieller Forschungsvereinigungen
Kerbwalzen und Wechselbiegen - Grundlegende Untersuchungen zur Herstellung von Fließgut mit geringem Aspektverhältnis ausgehend von Bandmaterial
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Inorder to increase the productivity of the production process of steel wires,the process chain of notch rolling and cyclic bending is fundamentallyanalyzed. During notch rolling, notches are formed on both sides of a sheetmetal strip, in whose areas the material fatigues and forms cracks during thesubsequent fulling process. The numerical and experimental implementation ofboth process steps enables the identification of relevant influencingparameters and their interactions. Parameters taken into account are, amongothers, the notch radius, notch angle and web thickness in notch rolling, andthe bending angle and number of cycles to breakage or to the desired residualweb thickness in cyclic bending. Numerical and experimental studies of ductiledamage are required to evaluate material separation.
Hilfsfügeteilfreies Fügen
(Third Party Funds Group – Sub project)
Term: 1. July 2019 - 30. June 2023
Funding source: DFG / Sonderforschungsbereich / Transregio (SFB / TRR)
URL: https://trr285.uni-paderborn.de/
Fundamental investigation of ultrasonic-assisted metal forming by compressive and shear stress
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Investigation of residual stress related elementary processes in cold forged components in the manufacturing and operating phase
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Due to the potential of forming induced residual stresses to influence component properties, a deeper understanding of the mechanisms of residual stress generation and stability is required. Therefore, the approach to the research project is structured into the phases of component manufacturing (generation of residual stresses), component operation (residual stress stability) and process design (exploitation of residual stresses). As reference process the forward rod extrusion is used, which is established as standard process in industrial use. Due to the trend towards component materials with higher strength and corrosion resistance, two stainless steels are used in the project. The investigations include parallel experimental and numerical analyses of the process and its synthesis.
During the first phase, the necessary experimental equipment for component manufacture and testing was set up, material and friction parameters were identified, components were formed under consideration of different parameter variants and their residual stresses were determined by X-ray diffraction. In a complementary approach, macroscopic finite element models with subroutines for an extended post-processing of residual stresses were developed on the simulation side and applied in the context of numerical parameter variations. Furthermore, differential geometric and continuum mechanical relationships of residual stresses were investigated and the material modelling was extended to crystal plasticity. The predictivity of the numerical results was quantified on the basis of experimental results.
The second phase concentrates on the residual stress stability in component use and the process robustness during component manufacture. The knowledge gained will be used at the end of the second and in the third phase to specifically influence the operating behaviour and to control the cyclic strength.
The objective in the second phase is the experimental and numerical determination of the mechanical and thermal residual stress stability. As a requirement for the targeted influencing, relevant parameters will be identified. These cause-and-effect relationships are to be plausibilised by means of fundamental physical effects, whereby a recourse is made to effects described in the literature and numerical methods for the derivation of basic model ideas. Based on the experience gained so far, fluctuations of input variables and previously known disturbance variables are to be taken into account in all investigations. A further prerequisite for a systematic investigation of the fundamental mechanisms relevant to residual stresses is an increase in the numerical modeling and prediction accuracy of the deformation-induced residual stresses. In analogy to the generation phase, a constant comparison of simulation and experiment is therefore also carried out in the operating phase in the sense of an assessment of the prognosis quality of the numerical approaches and the plausibility of the experimental laboratory results.
The Project is part of the DFG priority programm SPP2013 "Targeted Use of Forming Induced Internal Stresses in Metal Components". Within the priority program, the subproject takes part in the expert groups Production technology (thick-walled) and Mechanics and simulation.
Investigation of residual stress related elementary processes in cold forged components in the manufacturing and operating phase
(Third Party Funds Single)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
FOR 2271: Prozessorientiertes Toleranzmanagement mit virtuellen Absicherungsmethoden
(Third Party Funds Group – Overall project)
Funding source: DFG / Forschergruppe (FOR)
URL: https://www.for2271.tf.fau.de/
The comprehension of geometric part deviationsand their manufacturing and assembly related sources as well as the investigationof their effects on the function and quality of technical products builds theframework for the planned research group “process-oriented tolerance managementbased on virtual computer-aided engineering tools”. The aim of this researchgroup is the provision of holistic methods and efficient tools for thecomprehensive management of geometric deviations along the product originationprocess, which are to be validated in a model factory. In doing so, aparticular focus is set on the development of a procedure for the fruitfulcooperation of all departments involved in geometric variations management,from product development, to manufacturing, to assembly and to metrology, whichwill enable companies to quickly specify functional tolerances, which aremanufacturable and measurable, and consequently to save costs and to reduce thetime to market.
In this regard, the vision of the researchgroup is to enable the close collaboration of product development,manufacturing, assembly and metrology in computer-aided tolerancing, i. e.the joint formulation of functional tolerances, which are manufacturable andmeasurable. By enabling this close collaboration, all manufacturing andassembly related sources of later problems regarding the product function andquality can be considered already during early phases of virtual product andprocess development. As a consequence, tolerances can be specified efficientlyand optimized inspection plans as well as robust manufacturing and operatingwindows can be identified, which allows the development of robust products tobe manufactured and measured at low costs.
Since geometric part deviations are inevitableand affect the function and quality of technical products, their managementalong the product origination process is essential for the development offunctioning products, which conform to the quality and usage requirements ofcustomers and are successful on international markets. As a consequence,tolerance management is a fundamental task in product development and reachesvarious fields of industry, from consumer to industrial goods. Due to steadilyincreasing requirements on quality and efficiency, it strongly gains importancenot only with large, but also small and medium-sized enterprises. In thiscontext, the industrial application of the scientific findings of the researchgroup will contribute to the success of the German economy.
Consideration of functionally relevant geometric deviations in the design of metal forming processes for the production of gears by extrusion
(Third Party Funds Group – Sub project)
Term: 1. April 2016 - 31. March 2023
Funding source: DFG / Forschergruppe (FOR)
Additive and formative manufacturing of hybrid parts with locally adapted, tailored properties (B5)
(Third Party Funds Group – Sub project)
Term: 1. July 2011 - 30. June 2023
Funding source: DFG / Sonderforschungsbereich (SFB)
URL: https://www.crc814.research.fau.eu
Aim of this sub-projectis to investigate the combination of additive manufacturing and formingtechnology for the production of tailored, functionalized and individualizedtitanium hybrid parts, fundamentally. Besides the sheet metal body also theadditively manufactured elements of the hybrid parts will be formed. This leadsto a defined work-hardening of the material and locally adjusted properties. Bythe spatially resolved application of additives in combination with in situalloying during Laser Beam Melting (LBM) a local material modification isintended. This modification is supposed to be adjustable to the demands of theforming operation as well as to the demands of the later use case.
Center for Nanoanalysis and Electron Microscopy
(FAU Funds)
CENEM was established in 2010 to provide a forefront research center for the versatile characterization of materials and devices with state-of-the-art instrumentation and expertise and to intensify the interdisciplinary research. The big CENEM network represents the strong collaborations within the University of Erlangen-Nürnberg as well as the collaboration with other universities, dedicated research institutes and industry.
The support of the core facility CENEM by the German Science Foundation (DFG) and the Cluster of Excellence EXC 315 “Engineering of Advanced Materials” is gratefully acknowledged.
TRR 73: Manufacturing of complex functional components with variants by using a new sheet metal forming process - Sheet-Bulk Metal Forming
(Third Party Funds Group – Overall project)
Funding source: DFG / Sonderforschungsbereich / Transregio (SFB / TRR)
URL: http://www.tr-73.de
2022
2021
2020
Related Research Fields
Contact: