A. Erman Tekkaya

A. Erman Tekkaya
Technische Universität Dortmund | TUD · Institute of Forming Technology and Lightweight Components

Prof. Dr.-Ing. Dr.-Ing. E. h.

About

857
Publications
211,531
Reads
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13,560
Citations
Additional affiliations
August 2018 - present
Editorial Committee (CIRP Annals)
Position
  • CEO
July 2018 - present
European Society for Experimental Mechanics (EURASEM)
Position
  • Council member
Description
  • The Society is a European non-governmental non-profit scientific and engineering organization whose general purpose is the furtherance of international collaboration in the field of Experimental Mechanics.
March 2018 - present
The German Metal Forming Association (AGU)
Position
  • CEO
Description
  • The German Metal Forming Association (AGU) is founded 1974. The metal forming chairs or institutes at German Universities are unified in the AGU. The number of members is 26.
Education
March 1986 - January 1988
TC Üniversiteler Arası Kurul
Field of study
  • Mechanical Metallurgy
November 1980 - December 1985
Universität Stuttgart
Field of study
  • Umformtechnik
February 1979 - November 1980
Middle East Technical University
Field of study
  • Mechanical Engineering

Publications

Publications (857)
Article
Hot stamping tools require cooling channels, preferably with a high positioning flexibility. Conventionally, these are machined. This represents a disadvantage because of the limited accessibility for milling tools and the low flexibility. By means of the Directed Energy Deposition (DED) process, a flexible design of the cooling channels is possibl...
Article
Increasing demands for reducing greenhouse gases drive the metal processing industries to a CO 2 -neutral production. A thorough understanding of CO 2 emission sources from the stage of material acquisition up to the final component is thus necessary to improve the CO 2 footprint of sheet metal hot forming process chains. To emphasize on this, an e...
Article
Incremental sheet metal sheet forming (ISF) is a flexible forming process to manufacture sheet metal parts. ISF processes allow a control of residual stresses depending on the process parameters and the acting forming mechanisms. These forming-induced residual stresses highly influence the product properties. This paper presents numerical and exper...
Preprint
Metal laminated tooling provides a fast and cheap manufacturing concept. In this study, laser metal deposition (LMD) is used for reducing and eliminating the stair step effect in a metal laminated bending die. A systematical analysis of the effect of preheating of the laminae on the surface quality and mechanical properties of the bending die is pe...
Chapter
TrimmingTrimming by forming is the method of choice for the production of complex components with functional surfaces. With increasing strength, this method is no longer applicable due to the high tool load and risk of production stop. Hot cutting and quenching of boron-manganese grades is a solution to meet the part requirements out of geometry, m...
Article
The large strain flow curve is an essential input for the calibration of a myriad of plasticity models required for accurately simulating sheet metal forming processes and the mechanical performance of formed components. Studies on large strain flow curve identification can be divided in three main categories. The first class of experiments generat...
Article
Flow forming is an incremental sheet forming (ISF) process during which a sheet metal is compressed and stretched multiple times by means of one or multiple rotating roller tools. The local tool-workpiece contact zone evolves during the entire process. The necking phenomenon, which corresponds to an uncontrolled thinning of the part wall, is introd...
Article
Full-text available
Composite components combine the benefits of different materials, leading to improved product properties, enhanced resource- and energy efficiency and widening the product spectrum. Draw-forging is the unique combination of deep-drawing and cold forging, where a core material is encapsulated within a thin sheet metal blank. Previously, the basic dr...
Article
Full-text available
In research and industry, the in-plane torsion test is applied to investigate the material behaviour at large plastic strains: a sheet is clamped in two concentric circles, the boundaries are twisted against each other applying a torque, and simple shear of the material arises. This deformation is analysed within the scope of finite elasto-plastici...
Article
Full-text available
Electrically vaporizing foil actuators are employed as an innovative high speed sheet metal forming technology, which has the potential to lower tool costs. To reduce experimental try-outs, a predictive physics-based process design procedure is developed for the first time. It consists of a mathematical optimization utilizing numerical forming simu...
Article
To investigate the impact of the sudden shift to online education triggered by the COVID-19 pandemic, a survey was conducted among international mechanical engineering students, specializing in manufacturing technology, at the TU Dortmund University. The surveyed students, were exposed to differently structured online courses from different institu...
Article
Full-text available
The influence of anisotropic work-hardening on the component properties and process forces in cold forging is investigated. The focus is on the material behaviour exhibited after strain path reversals. The work-hardening of three steels is characterized for large monotonic strains (equivalent strains up to 1.7) and subsequent strain path reversals...
Article
The free and open source software tool ADAPT (A Diversely Applicable Parameter Identification Tool) for the inverse parameter identification of constitutive material models is presented and applied in combination with Finite Element (FE) simulations. Different types of input data, namely integral data such as forces and field data such as displacem...
Article
Full-text available
Bent components and deep drawn cups are produced by direct usage of aluminium chips without melting following a new process chain: hot extrusion of aluminium chips to a cylindrical open profile, flattening, subsequent rolling and bending or deep drawing. The properties of the hot extruded chip-based AA6060 sheets are examined by tensile tests and m...
Article
Full-text available
Zusammenfassung Die Prozessführung der inkrementellen Blechumformung beeinflusst maßgeblich den Eigenspannungszustand einer gefertigten Komponente und damit die Produkteigenschaften. Eine kontinuierliche Variation des Zustellinkrements im Umformprozess ermöglicht die lokale Ausbildung vordefinierter Eigenspannungen im Bauteil. Um die lokale Beeinfl...
Article
Full-text available
A new process combination route consisting of additive manufacturing (AM) with a subsequent forming operation is proposed. The process route has the opportunity to increase the efficiency of the AM process route up to 360%. Stainless steel 316L sheets with different core structures (similar to sandwich sheets) are produced by AM, characterized, and...
Article
Full-text available
Process-induced residual stresses significantly influence the mechanical properties of a formed component. A polymer pad is used as a flexible die in two-point incremental forming to induce compressive residual stresses in the component during the forming process. Experimental and numerical results illustrate the influence of compressive stress sup...
Article
Full-text available
The mechanical properties and the operating life of a formed component are highly dependent on the residual stress state. There is always a high magnitude of residual stresses in the components formed by incremental sheet forming (ISF) due to the localized deformation mechanism. Hence, a thorough understanding of the generation of the residual stre...
Article
The in-plane torsion test is a shear test that has already been successfully used to determine flow curves up to high strains for thin sheets with thicknesses between 0.5 mm and 3.0 mm. In the same way as with other shear tests, the formation of wrinkles is a major challenge in determining flow curves with the in-plane torsion test, especially when...
Article
Full-text available
Incremental sheet-bulk metal forming (iSBMF) enables the manufacture of functional lightweight components featuring a load-adapted shape with a high material efficiency. The flexibility of the incremental forming process allows for the modification of the strain path through the adjustment of the tool motion while maintaining the final product geom...
Article
A concise approach is proposed to determine a reduced order control design oriented dynamical model of a multi-stage hot sheet metal forming process starting from a high-dimensional coupled thermo-mechanical model. The obtained reduced order nonlinear parametric model serves as basis for the design of an Extended Kalman filter to estimate the spati...
Article
Strain hardening behaviours at large strain under various loading conditions are the basic but the most important input for reliable numerical simulation of plastic deformation processes, such as sheet metal forming and crash. However, neither the flow curve at large strain beyond necking nor the strain hardening under stress states different from...
Conference Paper
The in-plane torsion test is a shear test that has already been successfully used to determine flow curves up to high strains for thin sheets with thicknesses between 0.5 mm and 3.0 mm. In the same way as with other shear tests, the formation of wrinkles is a major challenge in determining flow curves with the in-plane torsion test, especially when...
Article
Metal sheets are forward extruded at large plastic strains up to 1.6. The sheet specimens are placed between two half-cylindrical billets and cold-extruded collectively. While extruding the sheets, their central zone is plastically deformed nearly homogeneously under a deviatoric stress state equivalent to simple tension. Tensile test specimens are...
Article
Full-text available
Multiturn coils are required for manufacturing sheet metal parts with varying depths and special geometrical features using electromagnetic forming (EMF). Due to close coil turns, the physical phenomena of the proximity effect and Lorentz forces between the parallel coil windings are observed. This work attempts to investigate the mechanical conseq...
Preprint
A concise approach is proposed to determine a reduced order control design oriented dynamical model of a multi-stage hot sheet metal forming process starting from a high-dimensional coupled thermo-mechanical model. The obtained reduced order nonlinear parametric model serves as basis for the design of an Extended Kalman filter to estimate the spati...
Article
Producing load-adapted and functionally integrated components by flexible and resource efficient processes has gained importance within industries like the automotive sector in recent years. A promising new class of processes that enables a local adaption of the sheet thickness is Sheet-Bulk Metal Forming (SBMF). While the incremental procedure (iS...
Article
Current joining technologies have to fulfil multiple requirements. Firstly, the demand of mass reduction is causing a progressive hybridization, requiring the joining of dissimilar materials. Additionally, load-adapted structures lead to a variety of different workpiece geometries. Finally, the integration of functions, like the requirement of join...
Article
Full-text available
Robust and versatile production is enabled by a closed-loop control of product properties. This essentially relies on the characterization of the interaction between properties and available degrees of freedom to control the process. In particular, this work examines the setting of collar height, thinning, curvature, and hardness during hot hole-fl...
Chapter
Sheet-bulk forming processes are applied to manufacture complex components with intricate shape elements or with large variations in wall thickness from sheet metals. Accumulated plastic strains achieved in sheet-bulk metal forming are substantially larger than in conventional sheet metal forming. Differing from sheet forming, the stress state is t...
Book
This book presents the findings of research projects from the Transregional Collaborative Research Centre 73. These proceedings are the result of years of research into sheet–bulk metal forming. The book discusses the challenges posed by simulating sheet–bulk metal forming. It takes into account the different phenomena characteristic to both sheet...
Article
Bei Biegeverfahren stellt die geometriepräzise Fertigung von gebogenen Profilen eine Herausforderung dar. Insbesondere beim Biegen von Profilen mit asymmetrischem Querschnitt zur Krafteinleitungsachse tritt eine Verdrillung des Querschnitts auf. Bisherige Methoden zum verdrillungsfreien Biegen benötigen besondere Belastungsstrategien, spezielle Wer...
Article
Full-text available
Many metal forming processes involve several steps, which influence the shape and properties of the final component. The previous manufacturing process of the semi-finished component influences the properties of extruded components. The authors analyze the evolution of damage and voids in the sequence of caliber rolling to cold forward rod extrusio...
Article
Full-text available
In this paper a process sequence, that uses forward rod extrusion with cold forged C15 steel cup billets to produce lightweight shafts, is presented. The steel cup billets feature either a lightweight magnesium alloy core or a granular medium core that is removed after forming to obtain hollow shafts without the need of complex tools and highly loa...
Book
Full-text available
Die Bildungs- und Arbeitswelten angehender Ingenieur*innen werden geprägt durch die Auswirkungen weltweiter Trends und Entwicklungen wie Digitalisierung, Entrepreneurship-Bewegungen und Globalisierung. In Folge führen arbeitsorganisatorische Herausforderungen und gesellschaftliche Entwicklungen zu mehr Komplexität auf inhaltlicher und methodischer...
Article
Full-text available
The objective of this paper is to present a new hybrid additive manufacturing route for fabricating collector coins with complex, intricate contoured holes. The new manufacturing route combines metal deposition by additive manufacturing with metal cutting and forming, and its application is illustrated with an example consisting of a prototype coin...
Article
Full-text available
In this study, an aluminium alloy of AA5182 is taken as the research object to study strain hardening under large plastic deformation. Tensile tests are done for four specimens, including dog-bone specimens, notched specimens, specimens with a central hole and in-plane shear specimens. Bulging tests are also conducted to measure strain hardening un...
Article
Additive manufacturing is proposed as a novel alternative to coin blank’s production routes based on rolling, blanking and edge rimming. The presentation draws from laser powder bed fusion of cylinders, slicing into individual coin blanks by electro discharge machining and surface preparation by polishing, to coin minting in a laboratory press-tool...
Conference Paper
The technology of incremental sheet-bulk metal forming (iSBMF) provides a resource-efficient approach for the near-net-shape manufacture of functional components featuring a load-adapted shape. For this reason, consecutive edge thickening and gear forming processes are experimentally developed, numerically investigated and analytically described. D...
Conference Paper
The industrial manufacturing of functional components featuring a load-adapted shape primarily occurs by cutting or joining processes. These processes lead to inferior material efficiency and mechanical properties. The technology of incremental sheet-bulk metal forming (iSBMF) avoids these disadvantages but presents challenges towards a controllabl...
Article
Full-text available
In addition to strain hardening and residual stress, damage influences the product performance of forward rod extruded parts. Damage is usually neglected and difficult to quantify. The evolution of ductile damage in metal forming is closely correlated to the load path. An experimental approach using automated energy dispersive X-ray spectroscopy (E...
Article
Full-text available
The possibility of applying CMR-B-scalar sensors made from thin manganite films exhibiting the colossal magnetoresistance effect as a fast-nondestructive method for the evaluation of the quality of the magnetic pulse welding (MPW) process is investigated in this paper. This method based on magnetic field magnitude measurements in the vicinity of th...
Article
Magnetic pulse welding (MPW) is a solid state welding process that bonds similar and dissimilar metals using a high velocity collision. In this paper, effects of impact velocity, target tube thickness, and mandrel inclusion on the interfacial morphology were investigated through the welding of tubular parts, Al6060T4 (flyer) to Cu-ETP (target), by...
Article
Full-text available
A new method to determine electromagnetic forming limits curves (EM-FLCs) for sheet metals is proposed. The different strain paths (between uniaxial and biaxial tension) are achieved by specific tool coil and specimen designs. It is ensured that the apex of the specimen deforms on a constant strain path, and excess bending at the apex is avoided. T...
Article
Full-text available
Collision welding is a high-speed joining technology based on the plastic deformation of at least one of the joining partners. During the process, several phenomena like the formation of a so-called jet and a cloud of particles occur and enable bond formation. However, the interaction of these phenomena and how they are influenced by the amount of...
Conference Paper
Full-text available
The requirements towards lightweight components and cost-efficient processes call for innovative developments. In the case of load-adapted components with functional elements, incremental Sheet-Bulk Metal Forming (iSBMF) presents a suitable approach. Nevertheless, secondary issues such as an inhomogeneous thickness increase at the sheet-edge are un...
Article
Collision welding processes are accompanied by the ejection of a metal jet, a cloud of particles (CoP), or both phenomena, respectively. The purpose of this study is to investigate the formation, the characteristics as well as the influence of the CoP on weld formation. Impact welding experiments on three different setups in normal ambient atmosphe...
Article
High speed metal forming processes apply dynamic pressures on a sheet metal blank. To predict the forming capabilities inherent to these processes, suitable modeling approaches are of interest. Often, complex and large finite element (FE) simulations are necessary. A simplified novel mechanical approach, named chain model, is introduced and compare...
Chapter
In mechanical engineering studies hands-on laboratories are an integral part of the students’ education. In manufacturing related fields, material characterization labs are often used to enable students to foster their understanding of different materials. To enhance the laboratory experience and to educate about specific aspects of the uniaxial te...
Chapter
Additive manufacturing, which enables the production of highly complex components that were previously next to impossible to manufacture, has evolved from a tool for rapid prototyping to an integral part of many production lines in the metal manufacturing industry. Therefore, it is critical that today’s students, the manufacturing engineers of tomo...
Article
Full-text available
Lightweight design is one of the current key drivers to reduce the energy consumption of vehicles. Design methodologies for lightweight components, strategies utilizing materials with favorable specific properties and hybrid materials are used to increase the performance of parts for automotive applications. In this paper, various forming processes...
Article
Physical mechanisms of ductile damage in metal forming, experimental characterization methods for damage, and models predicting the damage level in formed components are reviewed. Applications of damage analysis in metal forming processes reveal that damage in metal formed parts is not failure, but a product property that accumulates between proces...
Article
Full-text available
Vaporizing Foil Actuators (VFA) can be employed as an innovative, extremely fast sheet metal forming method. An ultimate goal in forming technologies is generally to be flexible and rely on as few part-specific tools as possible. Therefore, various realizable VFA pressure distributions were investigated with a focus on the free forming result. Fund...