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.

Identification of elastic parameters of composite using experimental data on modal characteristics of samples

Abstract: In order to determine the elastic parameters of polymer composites, a mixed numerical-experimental method of identification was developed in the 1990s - 2000s, based on the use of experimental data on natural frequencies and eigenmodes of oscillation of samples Its practical application involves the choice of a shape and a size of samples, a set used to identify the natural frequencies and eigenmodes of vibration, a methods of their experimental determination, a finite-element model for modal analysis, and an algorithm for solving the identification problemThe object of the research is laminated polymer composite materials reinforced with carbon or glass fibers The aim of the work is to develop practical aspects of implementation and assessment of the accuracy of the mixed experimental-calculation method for identifying of the elastic parameters of such materials based on experimental data on natural frequencies and eigenmodes of vibration of standard samples Parameter identification for the material is considered as an optimization problem with an optimization function, which is a weighted sum of squares of differences between the experimental and calculated values of natural frequencies A procedure was developed to implementing the main steps of the suggested technique: experiments, calculations and control of results An error analysis of main steps was carried out, and the accuracy of the determined parameters of the ply was estimated To determine the natural frequencies and eigenmodes of oscillation of the samples, the method of three-component scanning laser vibrometry was used The experimental technique was established and parameters of the technique were chosen to ensure the necessary accuracy in determining of the natural frequencies The parameters of the identification procedure and the finite-element model of the sample were selected To control the obtained values of the elastic parameters, the natural frequencies of the samples were calculated, including those not used in the identification procedure The error assessment of the in determined elastic parameters was performed on three different series of samples of carbon-fiber-reinforced laminates with the same material of the plies and different ply numbers and stacking orders The developed technique can be recommended to determine the parameters of material models required for strength and vibrations assessment of products manufactured with layered composites

TEM interfacial characteristics of thermosonic gold wire bonding on aluminium metallization

Abstract: A native alumina thin film existing on aluminium and its evolution in thermosonic gold wire bonding were characterized using high resolution transmission electron microscopy (HR TEM). It has been found that the partly fracture of this alumina film by the ultrasonic vibration allows the interdiffusion at the Au/Al interface, such that the intermetallic compounds (IMCs) are formed. The IMCs are identified as Au 4 Al and AuAl 2 with a thickness of approximately 300 nm. With a higher ultrasonic energy, IMCs are formed in more contact areas, resulting in a stronger bond. Based on these experimental results, a mechanism of ultrasonic gold wire bonding is proposed, which helps to understand the correlation among ultrasonic energy, interfacial structure and bonding strength.

Heterogeneous Intragranular Inelastic Behavior of a Sn-Ag-Cu Alloy

Abstract: To study the intragranular mechanical behavior of a Sn-Ag-Cu solder, a focused ion beam system was used to manufacture a notched microspecimen at a eutectic area within a grain. A low-speed tensile test was performed on the microspecimen using an Instron 5848 microtester at room temperature. The results show that, besides an obvious shearing deformation, a large number of subgrains are formed in the β-Sn matrix. Subgrain boundaries are composed of a large number of dislocations. Besides the heterogeneous deformation due to the notch, Ag 3 Sn intermetallic compounds influence the evolution path of subgrain boundaries.

Assessment of dynamic mode-I delamination driving force in double cantilever beam tests for fiber-reinforced polymer composite and adhesive materials

Abstract: The double cantilever beam (DCB) tests are widely used to assess the interfacial delamination properties of laminated composites. For quasi-static loads, the DCB tests are standardized based on the beam mechanics; for dynamic loads, however, such as high-loading-rate impact and cyclic loads, there is no established analytical theory. This presents a significant obstacle preventing the research community from assessing the delamination behavior of composites or adhesives for their application under complex in-service loads. In this paper, the theory of evaluating dynamic mode-I delamination driving force for DCBs under general displacement loads is developed for the first time, accounting for structural vibration effects. The developed theory is demonstrated by two examples: high-loading-rate split Hopkinson bar impact and cyclic fatigue loads. The analytical solutions are validated by published experiment results and in-house tests. This work provides a fundamental analytical tool to study and assess the fracture behavior of fiber reinforced-polymer composite and adhesive materials under various loading conditions.

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.