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.

Micro-macro transition for stochastic fracture process: Fractural approach.

Abstract: A fractal approach is proposed for the stochastic fracture analysis. The morphology of fractures are studied numerically for various types of materials stochasticity. The fractal dimension of crack front shape and scaling properties of the brittle fracture development are obtained with account for damage evolution.

Nonlinear Vibro-acoustic Interactions for Crack Detection in Beams

Abstract: Recent years have shown a growing interest in damage detection methods based on damage-related nonlinearities in structures. In the paper, the numerical simulations of two techniques – classical Higher Harmonic generation and Vibro-Acoustic Modulation - are presented and validated experimentally. Two-dimensional models of beam with non-propagating cracks are investigated. The focus is on bi-linear breathing crack behavior, which was modeled as a contact between crack faces. This phenomenon is known as crack breathing. Numerical simulation results show that nonlinear phenomena investigated are particularly strong in the vicinity of the crack. A number of aluminum beam specimens with different crack lengths and locations are investigated experimentally to validate numerical simulations. Signal responses were measured at several positions using piezoceramic sensors. The results show that nonlinear phenomena investigated depend not only on excitation amplitude – as expected – but also on crack position, sensor location and boundary conditions. doi: 10.12783/SHM2015/181

Damage and fracture in fabric-reinforced composites under quasi-static and dynamic bending

Abstract: Fabric-reinforced polymer composites used in sports products can be exposed to different in-service conditions such as large deformations caused by quasi-static and dynamic loading. Composite materials subjected to such bending loads can demonstrate various damage modes – matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution in composites affects both their in-service properties and performance that can deteriorate with time. Such behaviour needs adequate means of analysis and investigation, the main approaches being experimental characterisation and non-destructive examination of internal damage in composite laminates. This research deals with a deformation behaviour and damage in carbon fabric-reinforced polymer (CFRP) laminates caused by quasi-static and dynamic bending. Experimental tests were carried out to characterise the behaviour of a CFRP material under large-deflection bending, first in quasi-static and then in dynamic conditions. Izod-type impact bending tests were performed on un-notched specimens of CFRP using a Resil impactor to assess the transient response and energy absorbing capability of the material. X-ray micro computed tomography (micro-CT) was used to analyse various damage modes in the tested specimens. X-ray tomographs revealed that through-thickness matrix cracking, inter-ply and intra-ply delamination such as tow debonding, and fabric fracture were the prominent damage modes both in quasi-static and dynamic test specimens. However, the inter-ply damage was localised at impact location in dynamically tested specimens, whereas in the quasi-static specimens, it spread almost over the entire interface.

Finite Element Modelling of 2D Brittle Fracture: The Phase-Field Approach

Abstract: The prevention of fracture-induced failure is a major constraint in engineering design, and numerical simulations of fracture processes often play a key role in design decisions Although huge efforts have been made to develop novel and more accurate models of fracture and an enormous progress has been achieved in the recent years, the development of an adequate scheme for the numerical simulation of crack initiation and propagation is still a significant challenge for the scientific community The goal of this paper is twofold: (i) to give an overview of current numerical methods available in the literature for the analysis of brittle fracture problems; (ii) to present a finite element phase-field scheme for the analysis of brittle fracture problems This scheme relies on recently developed strategies for incorporating an additional phase-field to account for fracture The spatial finite element discretization is formulated by means of the classical Galerkin method, whereas an implicit Euler method with adaptive time-stepping is adopted for the temporal discretization To demonstrate the capabilities of the model, some numerical experiments are modelled

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.