Gerhard Hirt

Bio: Gerhard Hirt is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Forging & Incremental sheet forming. The author has an hindex of 30, co-authored 335 publications receiving 4463 citations. Previous affiliations of Gerhard Hirt include Saarland University & University of Bath.

Review on the development of a hybrid incremental sheet forming system for small batch sizes and individualized production

Abstract: Asymmetric Incremental Sheet Forming (AISF) has been developed as a flexible process for low-volume production of sheet metal parts. In AISF, a part is obtained as the sum of localized plastic deformations produced by a simple forming tool that moves under CNC control. In spite of about 20 years of research and development, AISF has not had much industrial take-up yet. The main reason for this is that attempts to improve, among other limitations, the accuracy, speed and range of feasible geometries of the process by adapted process strategies has not brought about general solutions. This paper presents an overview of the current state of development of hybrid asymmetric incremental sheet forming processes at RWTH Aachen University. The goal of the development of hybrid ISF processes is to allow for a quantum leap of the capabilities of AISF in order to enable a broader industrial use of AISF. Two hybrid process variations of AISF are presented: stretch forming combined with ISF and laser-assisted AISF. It is shown that the combination of stretch forming and AISF can improve the time per part, sheet thickness distribution and accuracy of the final part. Laser-assisted AISF is shown to enable the flexible forming of non cold-workable materials such as magnesium and titanium alloys when the forming conditions are adapted to the temperature and strain rate dependent formability of the sheet metal. In addition, first results of the forming of hybrid aluminum-steel sheet metal are shown.

Production of blanks with thickness transitions in longitudinal and lateral direction through 3D-Strip Profile Rolling

Abstract: 3D-Strip Profile Rolling should enable the production of blanks with a defined thickness profile in latitudinal and longitudinal direction. The production chain of 3D-Strip Profile Rolling will combine Flexible Rolling in a first production step with Strip Profile Rolling in a second step. The control system to adjust the roll gap during 3D-Strip Profile Rolling is currently under development. Nevertheless, some first experiments have shown the general feasibility to produce 3D-profiled blanks. In 3D-Strip Profile Rolling the material will strain harden differently on different locations. This results in a variation of the material properties of the strip. Lateral spread, elastic roll stand deformation and local deformation will be influenced by this variation. To investigate these influences on the complete production process, the complete production chain needs to be modelled in the future with aid of finite element simulations. In this publication a first simulation model is used to study the influence of different grades of strain hardening in a Taylor Rolled Blank on the bulge formation that occurs during the rolling of a rill in this Tailor Rolled Blank.

A new forming strategy to realise parts designed for deep-drawing by incremental CNC sheet forming

Abstract: The work detailed in this paper focuses on a new forming strategy for the CNC incremental sheet forming (ISF) process that is appropriate to form steep flanges, e.g. for parts designed for deep-drawing. When parts are designed for deep-drawing, they usually contain steep or rectangular side walls that cannot be manufactured using the standard ISF strategies. Unlike prior approaches to obtain steep flanges through ISF, the present method achieves a rough approximation to the final part already in the preforming stage. This can be accomplished without excessive sheet thinning due to sheet bending and stretching at this stage. As a consequence, additional material can be used for the finishing stages, thus yielding a final part with largely reduced thinning. After basic studies on a simple benchmark problem, the new bending/stretching strategy is tested with an industrially applied part that is usually produced by deep-drawing. Finally, the ISF workpiece is evaluated against the deep-drawn component with respect to sheet thickness and geometric accuracy.

Semi Solid Casting and Forging of Steel

Abstract: The semi solid forming of steel has the potential of an innovative technology, which could open a new possibility of metal components production. Earlier research works in the 1990s have already shown the principal feasibility of the process but also revealed the various kinds of technical problems. Since then, research works on steel processing have been continuously made in several locations in Japan, USA and Europe. Currently, the focus of these research activities is the development of suitable tool material and the achievement of high part quality, which is the key point for the success of the process. This paper gives an overview of the previous research works and the current state of the research with an outlook on future tasks for this challenge.

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Adaptive Control

Abstract: This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Effect of Temperature

Abstract: A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.