Mechanics of Taylor impact testing of polycarbonate

AbstractThe deformation of polymers under high-rate loading conditions is a governing factor in their use in impact-resistant applications, such as protective shields, safety glass windows and transparent armor. In this paper, Taylor impact experiments were conducted to examine the mechanical behavior of polycarbonate (PC), under conditions of high strain rate (∼105s−1) and inhomogeneous deformation. High-speed photography was used to monitor the progression of deformation within the sample. A recently developed three-dimensional large strain rate-dependent elastic–viscoplastic constitutive model which describes the high-rate behavior of glassy polymers was used together with the ABAQUS/Explicit finite-element code to simulate several Taylor impact conditions. The simulation results are compared directly with experimental images for a range in initial rod dimensions and velocities. Final deformed shapes are found to correspond with those obtained experimentally, demonstrating the ability to predict complex inhomogeneous deformation events during very high-rate impact loading scenarios. The dependence of the observed behaviors on the various features of the polymer stress–strain behavior are presented in detail revealing the roles of strain softening and strain hardening in governing the manner in which deformation progresses in a polymer during dynamic inhomogeneous loading events

Telecom Data Analysis

The telecommunications industry regularly uses data analytics in fields such as customer analysis and network optimization. For financial analysis such as identifying risks, which could negatively impact an entity’s financial performance, communications service providers have traditionally used statistical sampling techniques that cover only short time periods and a limited subset of data. Given the massive number of transactions processed by telecommunications companies; and the costs and complexity involved in their operations, data analytics offers a valuable opportunity for enhancing the frameworks and procedures they adopt to drive profitability and minimize unnecessary downside risk

Impact of woven fabric: Experiments and mesostructure-based continuum-level simulations

Woven fabric is an increasingly important component of many defense and commercial systems, including deployable structures, restraint systems, numerous forms of protective armor, and a variety of structural applications where it serves as the reinforcement phase of composite materials. With the prevalence of these systems and the desire to explore new applications, acomprehensive, computationally efficient model for the deformation of woven fabrics is needed. However, modeling woven fabrics is difficult due, inparticular, to the need to simulate the response both at the scale of the entire fabric and at the meso-level, the scale of the yarns that compose the weave. Here, we present finite elements for the simulation of the three- dimensional, high-rated eformation of woven fabric. We employ a continuum- level modeling technique that, through the use of an appropriate unit cell, captures the evolution of the mesostructure of the fabric without explicitly modeling every yarn. Displacement degrees of freedom and degrees of freedom representing the change in crimp amplitude of each yarn family fully determine the deformed geometry of the mesostructure of the fabric, which in turn provides, through the constitutive relations, the internal nodal forces. In order to verify the accuracy of the elements, instrumented ballistic impact experiments with projectile velocities of 22–550 m/s were conducted on single layers of Kevlar ® fabric. Simulations of the experiments demonstrate that the finite elements are capable of efficiently simulating large, complex structures

Large deformation rate‐dependent stress‐strain behavior of polyurea and polyurethane

International audienceno abstrac

Stress−strain behavior of a polyurea and a polyurethane from low to high strain rates

International audienceno abstrac

The sensitivity of electrodiagnostic criteria in subtype identification at the presentation in patients of Guillain-Barre syndrome

Introduction: Electrophysiology plays a pivotal role in identifying various GBS subtypes. Despite having many electrodiagnostic criteria,studies addressing their applicability in patients of GBS at diagnosis are quite a few. Purpose: This study evaluates the sensitivity of 5 known electrophysiological criteria in patients with GBS at the time of presentation. Material & Methods: Clinical and electrophysiological data of GBS patients admitted with us between January 2011 and December 2016 were collected retrospectively from our hospital database, compiled and analyzed. For each patient, 5 different criteria for the electrophysiological diagnosis of GBS were applied, and the sensitivity of these 5 criteria in the diagnosis was evaluated. Results: A total of 288 patients were included. Closer concordance was noted between the criteria in diagnosing axonal subtype (Range- 36.81% to 41.32%).Italian criteria had the highest sensitivity (41.32%). There was a wider variation in the diagnosis of AIDP (Range- 19.79 to 34.72%). Hadden criteria showed the highest sensitivity (34.72%) closely followed by Ho et al (34.02%). Conclusion: As the timing of Nerve Conduction Studies (NCS) and the severity of disease influence the grouping of each patient into a specific electrophysiologic subtype, one should be cautious in interpreting electrodiagnosticdata. Serial nerve conduction studies may be required to subtype each patient as electrophysiology evolves over the first few weeks of illness