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

The Design and Analysis of Experiments

Data Mining Practical Machine Learning Tools and Techniques

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.

Adaptive Control

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.

Effect of Temperature

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Direct thin strip casting is an economically end energetically smart process for the production of steel strip. In a single process step, liquid steel can be cast and directly rolled to hot strip in thicknesses ranging from one to four millimeters. With the use of specifically profiled casting rolls it is possible to produce strip with optimized cross-sections, allowing this process to compete with tailor welded and tailor rolled blanks for the production of a class of products already widely applied in industry. Numerical and experimental studies proved the feasibility of this concept and additional simulations were used to optimize the profile to be used for the experiments. A thickness variation of one millimeter from the edge to the center could be successfully achieved. However, the dimensional precision and the roughness distribution along the cross section of the produced strip were not satisfactory. Additional profiles were applied for the experimental analysis leading to better roughness distribution and geometrical accuracy. In order to further improve the uniformity of properties along the profiled section it is necessary to increase the homogeneity of the microstructure. The coating and surface preparation of the casting rolls play a very important role in the strip casting process as they strongly affect the solidification behavior. This observation lead to the idea of selectively coating the casting rolls, applying a less conductive layer on the areas where the casted profile is thinner. Thus, a more homogeneous solidification front can be obtained. The effect of a locally modified casting roll coating on the solidification is numerically investigated and the results applied for the selection of the coating parameters to be used for the experiments.

Advances in the Twin-Roll Strip Casting of Strip with Profiled Cross Section

In the architecture and construction sector the trend for individualization is often expressed in complex-shaped freeform buildings. Due to missing universal and mature construction methods for freeform buildings, they are usually realized with customized solutions that often include massive, material-consuming substructures, while the visible skin has neither structural nor functional properties. In this context a new concept for self-supporting lightweight structures for the realization of free-form surfaces and the production of the corresponding components has recently been proposed. Taking into account the large part dimensions and the varying part geometries in this application a flexible production chain based on incremental sheet forming has been developed and optimized. It has been validated by producing six-sided large-scale pyramids in 140 similar variants which were assembled to a self-supporting free-form demonstrator. Two-point incremental sheet forming (TPIF) was used with a universal partial supporting tool with the goal to produce all variants without dedicated tooling. Although the majority of pyramids was produced successfully with the applied TPIF strategy, there was a small number of parts with a very asymmetric shape that showed severe buckling in the side walls. For a detailed analysis of this observation the asymmetry was quantified using a wall angle ratio. Subsequently, a single-point incremental sheet forming (SPIF) strategy was successfully applied as an approach to avoid buckling. The results confirm the assumption that the circumferential expansion in SPIF suppresses buckling due to tensile stresses in the side walls, whereas the circumferential compression in TPIF triggers buckling due to the compressive stresses in the side walls.

Analysis into Differences between the Buckling in Single-Point and Two-Point Incremental Sheet Forming of Components for Self-Supporting Sheet Metal Structures

Ring Rolling is a versatile metal-forming process to manufacture seamless rings of various cross-sectional geometries. Rings with a “dish shape” are used in different areas such as offshore, aeronautics or the energy sector. Current ways to produce dish shaped rings have the disadvantages of limited or inflexible geometries and either high material waste, additional costs for special tools or long process time. Instead, when manufacturing dish shaped rings on conventional radial-axial ring rolling mills, ring producers will be able to expand the range of their products easily. In a prior investigation, the general feasibility of an alternative to the current manufacturing processes was shown in experiments and in finite element method (FEM) simulations, avoiding major additional machining and material costs. Resulting from an analysis of the geometrical requirements and material flow mechanisms for dishing and ring climbing, a rolling strategy was derived, applying a large height reduction of the ring. A major problem of this rolling strategy is that whenever the contact between the ring and the main roll is lost in the process, the ring starts to oscillate around the mandrel and neither dishing nor ring climbing can be observed. In order to ensure a permanent contact between ring and main roll and in order to stabilize the ring in its inclined position in the rolling mill, additional stabilizing measures of the process will be developed and investigated. With the developed FE-model, a stabilizing measure by the use of pressure rolls and automatic guide roll movement for ring climbing was tested and appears promising for the application in a real experimental environment.

Intended Dishing in Ring Rolling

Kurzfassung Das thermomechanische Behandlungsverfahren (TMB), welches durch den Verzicht auf eine separate Warmebehandlung hohe Potenziale zur Einsparung von Energie- und Prozesskosten bietet, hat sich im Bereich der Ringherstellung bislang kaum etablieren konnen. Die Ursache fur den geringen Entwicklungsstand lasst sich auf das fur das Ringwalzen typische, stark instationare und damit auserst komplexe Prozessverhalten zuruckfuhren. Diese Besonderheit bringt selbst moderne, auf Basis der Finite-Elemente-Methode (FEM) arbeitende Simulatoren an ihre Leistungsgrenzen. Durch die inakzeptabel langen Rechenzeiten scheidet die FEM daher zur Simulation der Gefugeevolution als Grundlage zur Entwicklung thermomechanischer Behandlungsstrategien fur den Ringherstellprozess aus. Im Rahmen des vorgestellten Forschungsvorhabens wurde deshalb ein weitestgehend analytisch und somit schnell rechnendes Simulationsmodell entwickelt. Zur globalen Simulationssteuerung wurde ein verbreiteter, kommerzieller Prozesssimulator in d...

Schnelle Modelle zur Simulation der Gefügeevolution beim Ringwalzen

In recent years, hot stamping of sheet metal parts has emerged to satisfy the contrary demands of the automotive industry for components with increased strength at reduced weight. To analyse the material behaviour during these processes, a hot gas bulge test at high temperatures and high strain rates is promising, since the bulge test at room temperature has already proven itself as a useful test for the material characterization of sheet metals up to high strains. Therefore, a hot gas bulge test at elevated temperatures and high strain rates is being developed at the Institute of Metal Forming (IBF) in cooperation with the Institute for Fluid Power Drives and Controls (IFAS) at the RWTH Aachen. To verify if the concepts of the membrane theory, which are used for the evaluation of bulge tests at room temperature, are adaptable to such a hot gas bulge test, a simulation study using finite element calculations was conducted. The purpose of this simulation study is is to estimate the errors which occur if the equivalent stress at the bulge pole is calculated by using the membrane theory. In addition to this study several approaches were examined to obtain the sheet thickness at the bulge pole by measuring the bulge height. The study showed that a hot gas bulge test can be described very well by the membrane theory if the sheet thickness, the curvature at the bulge pole and the pressure inside the bulge are exactly known. However, substantial errors can occur if the sheet thickness at the bulge pole is determined by measuring the height of the bulge pole.

Gerhard Hirt

Papers

Advances in the Twin-Roll Strip Casting of Strip with Profiled Cross Section

Analysis into Differences between the Buckling in Single-Point and Two-Point Incremental Sheet Forming of Components for Self-Supporting Sheet Metal Structures

Intended Dishing in Ring Rolling

Schnelle Modelle zur Simulation der Gefügeevolution beim Ringwalzen

Investigation of a Bulge Test at High Temperatures and High Strain Rates Using a Finite-Element Simulation Study