Author
Gerhard Hirt
Other affiliations: Saarland University, University of Bath
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.
Papers published on a yearly basis
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TL;DR: In this article, the Taylor factors were used to estimate the conditions under which a microforming process is likely to be influenced by single grain orientations and to explain the difference between flow stress determination in microcompression or microtensile tests versus punch force in microdeep drawing.
67 citations
TL;DR: The state of the art of steel thixoforming can be found in this paper, where the authors present a survey of the state-of-the-art of thixoeformable steels.
Abstract: The thixoforming of metals is a new forming technology, which combines the advantages of casting and forging and focuses on the production of structural components with complex shapes. Various components made of aluminium and magnesium are already industrially produced. Apart from this, using steels in the thixoforming processes is still a matter of research. This paper summarises the state of the art of steel thixoforming. Besides relevant material and process parameters, different process routes, numerical modelling techniques, and tool requirements are discussed. In addition, thixoformed prototypes of different steel grades are presented and evaluated with defect index cards, which characterise occurring defects and give suggestions how to avoid them. The design of suitable tool materials and tool concepts, the development of heating strategies which provide a homogeneous temperature distribution, and the development of thixoformable steels are main topics of current research. This paper focuses on the technology of steel thixoforming with regard to the material requirements, the production processes, and the accompanying current technical problems.
64 citations
TL;DR: In this paper, the effect of selected single-scale and multi-scale surface patterns fabricated by roller-coining and/or direct laser interference patterning on the frictional performance of journal bearings was examined.
57 citations
TL;DR: In this article, the forming restrictions of the high pressure sheet metal forming of tailor-rolled blanks are presented and two optimisations, considering not only the process chain but also the behaviour under loading conditions, are shown.
53 citations
TL;DR: In this paper, a ball-on-disc tribometer was used to study the tribological properties of hemispherical structures fabricated by hot micro-coining on stainless steel samples and the largest improvement was achieved using a pattern with a pocket depth of 25μm and an area density of 5%.
52 citations
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Journal Article•
TL;DR: 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.
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
13,333 citations
Journal Article•
9,185 citations
Journal Article•
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TL;DR: In this paper, two major figures in adaptive control provide a wealth of material for researchers, practitioners, and students 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.
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.
1,814 citations
01 Jan 1976
TL;DR: 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.
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.
1,573 citations