Vadim V. Silberschmidt

Bio: Vadim V. Silberschmidt is an academic researcher from Loughborough University. The author has contributed to research in topics: Machining & Materials science. The author has an hindex of 44, co-authored 543 publications receiving 8619 citations. Previous affiliations of Vadim V. Silberschmidt include University of Rhode Island & Universities UK.

Effect of Cutting Conditions on Temperature Generated in Drilling Process: a FEA Approach

Abstract: Heat generated during a drilling process has a major influence on the tool life and the workpiece material behaviour that are significantly affected by cutting conditions (cutting speed, feed rate). In this paper, the effect of cutting conditions on temperature generated in drilling process is investigated by means of finite element (FE) simulations using commercially available code MSC MARC MENTAT. A Johnson Cook material model is used to describe elasto-plastic deformation behaviour. The updated Lagrangian procedure is used to implement the transient analysis for the elasto-plastic material in the model. A modified shear friction model is employed to model friction at the tool tip-workpiece interface. The effect of friction on chip shape is investigated with FE simulations. Experiments were carried out to verify the FE results.

Finite-Element Analysis of Forces in Drilling of Ti-Alloys at Elevated Temperature

Abstract: Demand for high-strength alloys in aerospace, marine and off-shore industries has grown significantly over last decades, primarily thanks to their high strength, light weight as well as good fatigue and corrosion-resistance properties. However, these materials are extremely difficult to machine with conventional machining methods. Hot machining is an alternative technique used by many researchers for cutting of hard-to-cut materials in turning and milling operations. In this assisted machining technique, an external heat source is used to reduce shear strength of the machined workpiece, enhancing material removal of such alloys. Drilling is one of the most important and basic operations for producing cylindrical holes in machined components. In this work, a three-dimensional finite-element (FE) model of drilling process is developed in a commercial FE software DEFORM 3D. A nonlinear temperature-dependent material behaviour is incorporated in numerical simulations. The effect of an external heat source on thrust forces and torque on a drill-bit was investigated with the developed FE model. Advantages of hot drilling in reducing thrust force and torque reduction are demonstrated.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

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

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

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.