Experimental characterization and finite element modelling of strain-rate dependent hyperelastic properties of PVB interlayers

Laminated glass provides safety in an impact or explosion event by way of a polymer interlayer to which glass fragments adhere upon fracture. The mechanical deformation of the interlayer defines how the impact energy can be absorbed to prevent calamities by flying glass debris, penetration of a blast wave, lacerations, etc. The PVB interlayer used in safety glass shows highly nonlinear viscoelastic material behaviour, with a great sensitivity to temperature and deformation rate. Although various material models for PVB can be found in literature, few publications discuss the full range of its mechanical behaviour and none are found to describe a material model that is valid in a wide range of deformation rates and up to high elongations. Such material model is necessary for the numerical study of the post-fracture response in a dynamic event. The article describes the mechanical behaviour of PVB interlayer and the constitutive models by which the polymer can be represented under different load cases. Tensile experiments of Saflex® PVB are presented for a wide range of deformation rates and up to tearing of the specimens. Subsequently, a method to calibrate a hyper-viscoelastic material model for the interlayer by numerically simulating the tensile tests is developed. The resulting material models are valid up to the tearing strain of the interlayer and are accurate within a specified range of deformation rates and temperatures

Experimental Characterization and Finite Element Modelling of Strain-rate Dependent Hyperelastic Properties of PVB Interlayers

Laminated glass provides safety in an impact or explosion event by way of a polymer interlayer to which glass fragments adhere upon fracture. The mechanical deformation of the interlayer defines how the impact energy can be absorbed to prevent calamities by flying glass debris, penetration of a blast wave, lacerations, etc. The PVB interlayer used in safety glass shows highly nonlinear viscoelastic material behaviour, with a great sensitivity to temperature and deformation rate. Although various material models for PVB can be found in literature, few publications discuss the full range of its mechanical behaviour and none are found to describe a material model that is valid in a wide range of deformation rates and up to high elongations. Such material model is necessary for the numerical study of the post-fracture response in a dynamic event. The article describes the mechanical behaviour of PVB interlayer and the constitutive models by which the polymer can be represented under different load cases. Tensile experiments of Saflex® PVB are presented for a wide range of deformation rates and up to tearing of the specimens. Subsequently, a method to calibrate a hyper-viscoelastic material model for the interlayer by numerically simulating the tensile tests is developed. The resulting material models are valid up to the tearing strain of the interlayer and are accurate within a specified range of deformation rates and temperatures

Numerical simulation of the EN 12600 Pendulum Test for Structural Glass

In modern-day architecture, transparent glass units are omnipresent as large façades, windows, floors and balustrades. To ensure safety in an accident, glass panels must successfully pass the 'human impact' test, described by the international standard EN 12600. This test setup consists of a steel frame in which the test plate is clamped with prescribed force; and the pendulum impactor, hanging from a steel cable. The impactor weighs a total 50 kg and is built up from a rigid steel core to which two small tyres are mounted. The window panels are assigned a qualification number as they remain intact, fracture without losing integrity or fragment completely in impacts from different drop heights. As experimental testing is expensive and time-consuming, there is an interest in numerical modelling to predict a qualifying glass panel, which is already allowed by the German standard DIN 18008-4. Several modelling approaches allow the impact simulation for intact glass panels. This paper presents a detailed numerical model for the pendulum impact which enables realistic simulation of impactor, frame and test plate, to be valid also for the post-breakage safety assessment of laminated glass. The model shows good correspondence for static compression of the tyres and for impact against a pressure plate. Further comparison is made for the impact on a laminated glass panel that remains intact. Although less suited for structural design qualification, the detailed model can be used for future simulation of the post-breakage response of laminated glass panels

5G Technologies: Insights, Opportunities & the Future

The advances in fifth-generation (5G) cellular technologies have shown much potential in this transformational technology which has been critical in driving economic development via numerous opportunities and applications. 5G technology is integral to realizing the full potential of the Internet of Things, edge computing, and artificial intelligence technologies in the real world. The purpose of this panel is to disseminate multi-faceted perspectives on 5G in order to more holistically understand it, such as diverse spectrum, network slicing, edge computing, cloud radio access network (C-RAN), various industries and use cases, business model, deployment, vulnerabilities; and to stimulate an engaging discussion on 5G. Three executives with expertise in the telecom industry, along with three academicians knowledgeable in the 5G and wireless telecom field, will share their perspectives and insights on 5G. They will also discuss the research agenda in the Information Systems field

Accurately measuring 2D position using a composed grid pattern and DTFT

In this research study, a novel optical measurement technique has been developed which can, in great detail, capture the displacement, velocity and acceleration of a rigid body. One example is an impactor in free fall striking a test specimen. Another application where the technique has succesfully been applied is during bird strike experiments. The technique sets itself apart by its ease of use and sub-pixel accuracy and precision. To achieve this, a 2D grayscale line pattern with known and constant pitch is applied to the rigid body. The grid pattern is filmed with a high speed camera perpendicular to its surface. The images, or rather the recorded intensities, undergo a Fourier transform and the phase shift of each subsequent frame is converted to a displacement measurement. Several operations are applied to optimally prepare the signal for a DTFT algorithm. Differentiating the signal to velocity and again to acceleration, which has also been measured with an accelerometer, proves the adequacy of the method. No calibration of the system is necessary, unlike with DIG, apart from an accurate measurement of the pitch

Non-invasive estimation of QLV from the standard 12-lead ECG in patients with left bundle branch block

Background: Cardiac resynchronization therapy (CRT) is a treatment for patients with heart failure and electrical dyssynchrony, i.e., left bundle branch block (LBBB) ECG pattern. CRT resynchronizes ventricular contraction with a right ventricle (RV) and a left ventricle (LV) pacemaker lead. Positioning the LV lead in the latest electrically activated region (measured from Q wave onset in the ECG to LV sensing by the left pacemaker electrode [QLV]) is associated with favorable outcome. However, optimal LV lead placement is limited by coronary venous anatomy and the inability to measure QLV non-invasively before implantation. We propose a novel non-invasive method for estimating QLV in sinus-rhythm from the standard 12-lead ECG. Methods: We obtained 12-lead ECG, LV electrograms and LV lead position in a standard LV 17-segment model from procedural recordings from 135 standard CRT recipients. QLV duration was measured post-operatively. Using a generic heart geometry and corresponding forward model for ECG computation, the electrical activation pattern of the heart was fitted to best match the 12-lead ECG in an iterative optimization procedure. This procedure initialized six activation sites associated with the His-Purkinje system. The initial timing of each site was based on the directions of the vectorcardiogram (VCG). Timing and position of the sites were then changed iteratively to improve the match between simulated and measured ECG. Noninvasive estimation of QLV was done by calculating the time difference between Q-onset on the computed ECG and the activation time corresponding to centroidal epicardial activation time of the segment where the LV electrode is positioned. The estimated QLV was compared to the measured QLV. Further, the distance between the actual LV position and the estimated LV position was computed from the generic ventricular model. Results: On average there was no difference between QLV measured from procedural recordings and non-invasive estimation of QLV ( [Formula: see text] ). Median distance between actual LV pacing site and the estimated pacing site was 18.6 mm (IQR 17.3 mm). Conclusion: Using the standard 12-lead ECG and a generic heart model it is possible to accurately estimate QLV. This method may potentially be used to support patient selection, optimize implant procedures, and to simulate optimal stimulation parameters prior to pacemaker implantation

A near-infrared tip-tilt sensor for the Keck I laser guide star adaptive optics system

The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope’s LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph

High‐Volume Processed, ITO‐Free Superstrates and Substrates for Roll‐to‐Roll Development of Organic Electronics

The fabrication of substrates and superstrates prepared by scalable roll‐to‐roll methods is reviewed. The substrates and superstrates that act as the flexible carrier for the processing of functional organic electronic devices are an essential component, and proposals are made about how the general availability of various forms of these materials is needed to accelerate the development of the field of organic electronics. The initial development of the replacement of indium‐tin‐oxide (ITO) for the flexible carrier materials is described and a description of how roll‐to‐roll processing development led to simplification from an initially complex make‐up to higher performing materials through a more simple process is also presented. This process intensification through process simplification is viewed as a central strategy for upscaling, increasing throughput, performance, and cost reduction