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.

A novel approach for temperature control in ISF supported by laser and resistance heating

Abstract: Aeronautical applications often require small batches of large-scale sheet metal parts made from titanium and its alloys. Due to the low formability of titanium at room temperature, warm forming processes are necessary. Incremental sheet metal forming (ISF) is suitable for production of prototypes and small batches as well as large-scale parts. A short review of the experimental work done by international scientists in the field of warm ISF including stationary and moved temperature sensors will be presented mostly applied from the backside of the sheet metal. The present paper shows a new approach for a tool setup including a thermocouple inside of the tool. Hence, the sensor for temperature measurement was moved with the forming zone. Furthermore, a suitable closed loop control including a PID controller will be presented. The characteristics of the controller will be discussed. By means of two different warm ISF processes (ISF with resistance heating and laser-assisted ISF), the applicability of the developed setup will be analysed and evaluated. It will be shown that the experimental setup is capable to ensure minimal temperatures needed to ensure adequate formability of Ti grade 5.

Twin-roll strip casting: A competitive alternative for the production of high-manganese steels with advanced mechanical properties

Abstract: In this work, a high-manganese Fe–29Mn–0.3C TWIP steel was produced by twin-roll strip casting and subjected to additional thermo-mechanical treatment. The evolution of microstructure and texture in each processing condition was investigated and correlated with the corresponding mechanical properties. Due to pronounced microsegregations, chemical gradients and an inhomogeneous microstructure in the as-cast and hot-rolled material, regions of strongly varying stacking fault energy caused undesired austenite–martensite transformation and inhomogeneous mechanical properties. The specimens after additional cold rolling and annealing at temperatures as low as 900 °C revealed a microstructure with a homogeneous grain size distribution and significantly reduced microsegregations. The resulting mechanical properties were comparable to those of industrial advanced high strength steels and TWIP steel produced by conventional processing, where energy-consuming homogenization is necessary. Therefore, twin-roll strip casting offers the possibility for cost-effective processing of TWIP steel with competitive mechanical properties.

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.