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.

Dynamic large-deflection bending of laminates

Abstract: Composite laminates employed in various sports products are usually subjected to large-deflection dynamic bending during their service. The chapter first describes the experimental characterisation of composites as well as investigation of various damage modes ensued under these loading conditions replicated by means of Izod-type dynamic tests. It then describes the development of three-dimensional finite-element models employing a cohesive-zone method to study the onset, progression and interaction of some damage modes observed experimentally. The developed numerical models are capable of simulating damage mechanisms in laminates and their interaction observed in the tests.

Dynamic fractures of adhesively bonded carbon fibre-reinforced polymeric joints

Abstract: The main aim of this chapter is to investigate the behaviour of adhesive joints exposed to repeated low-velocity impact, that is, impact fatigue (IF), and to compare this loading regime with standard fatigue (SF), that is, nonimpacting, constant amplitude, sinusoidal loading conditions. Fatigue crack growth using bonded carbon fibre-reinforced polymeric lap strap joints is conducted. It is seen that IF had the potential to initiate a crack and to cause its rapid propagation at levels of loading that were significantly lower than quasistatic and dynamic strengths and even the fatigue durability of joints. Differences between IF and SF are seen in mixed-mechanism failure and also with regard to the crack speed. It is found that in the initial stages of the crack propagation, the crack rate is 10 times higher in IF than in SF. It is found that the introduction of a relatively small number of in-plane impacts between blocks of SF drastically changed the dynamics of fracture in the specimen, with the IF blocks having a damage accelerating effect. The fatigue crack growth rate curve is seen to be a valid representation of fatigue propagation under SF and IF, in which a combination of experimental data and finite element analysis enables the curve to be constructed. It is seen that the curve shows a normal fatigue relation shape with clearly distinction of a linear and critical regions. It is concluded that this curve can be used to analyse crack propagation in IF and also in SF. Changes of the fracture mechanism in specimens are modelled by the mixed-mechanism fracture model, which represented the experimentally observed acceleration of fatigue crack growth rate when the crack path changes.

Thermo-mechanical behaviour analysis of micro-solder joints by finite element modelling

Abstract: Modern trends in design of electrical products require miniaturization and multi-function. In line with these trends, dimensions of lead-free solder joints reduce from over 100μm to 10μm, resulting in some new reliability issues. A high fraction of intermetallic compounds (IMC) with various shapes is a key feature in micro-solder joints. So far, few investigations focused on the influence of high fraction of IMCs on thermal fatigue, which is of great importance for reliability of electronic devices. In this work a parameterized finite element model is presented and analyzed to find out the change in stress and strain distributions in micro-solder joints. Different thicknesses and shapes of IMC are simulated. Results show that both thickness and shape of IMC have significant effects on thermal stress and creep strain.

Effect of surgical defect localization on ultimate load-bearing capacity of human femur: finite-element energy-based assessment

Abstract: Elastic properties and toughness of cortical bone tissue are non-uniformly distributed over its anatomical quadrants. This can have an effect on the bone’s load-bearing capacity after a surgical resection associated with a removal of tumor-like lesions followed by formation of a sectorial bone defect. The purpose of this work is to evaluate the ultimate load-bearing capacity of the femur with the post-resection defect, taking into account various types of distributions of elastic properties and toughness in different quadrants of a cross section of the bone. The elasticity modulus of the bone tissue in the longitudinal direction of the femur is determined based on a nanoindentation test of a human femoral bone specimen. Based on numerical simulations, it is established that the most dangerous – with regard to the occurrence of a pathological fracture – is the localization of the post-resection defect, when a remaining fragment of the bone tissue is located in the anterior quadrant. In this case, the value of the ultimate load is significantly lower compared to that for other variants of localization of the post-resection defect. A non-uniform distribution of fracture toughness in the cross-section of the femur has a greater effect on the magnitude of the ultimate load than non-uniformity of elastic properties. This should be taken into account when evaluating the ultimate load, since averaging the toughness over the bone’s cross-section can result in overestimations. Neglecting non-uniformity of toughness can lead to an incorrect assessment of the ultimate load and to wrong recommendations for postoperative rehabilitation of a patient.

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.