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The Energy Absorption Capability of Composite Materials and Structures: Influence of Impact Loading
Get PDFIn this paper, the energy absorption capability of composite materials and performance-critical structures made from using these materials under conditions of impact loading is presented and discussed. An overview is provided of the key events associated with detonation and decomposition of an explosive that eventually culminates in the generation of a shock wave that exerts an impact type of loading on structures both in contact and in the immediate vicinity. The blast loads that culminate from an explosive often tend to generate very high strain rates in the range of 102/sec to 104/sec. The resultant high rate of loading does tend to exert an influence on dynamic mechanical properties of the targeted structure besides exerting an influence on damage mechanisms experienced by the structural element. The progressive use of composite materials for structures, such as sandwich panels, that essentially comprise of a mixture of composite face sheets and foam cores was shown by researchers, based on actual field test data, to offer few to many advantages over usual metal counterparts when it came to the purpose of offering acceptable blast resistance. Thus, it became both essential and desirable to assess the blast response of composite structures made using appropriate selection of composite materials. Through the years several independent research studies have been conducted to understand the influence of blast loading on the response kinetics of sandwich panels. Key highlights of the research done and resultant findings obtained from these studies is presented and briefly discussed The importance of both material selection and resultant structure for providing adequate protection against an impact type of loading caused by an explosive device, such as Improvised Explosive Device (IED), is highlighted through appropriate summary of research conducted and published in the open literature. The need and necessity for developing new and improved materials, composite in nature, that can be used for performance-critical structures that can also offer an enhanced level of safety to all personal involved in emphasized
A Consistent and Long-term Mapping Approach for Navigation
Get PDFThe construction and maintenance of a robocentric map is key to high-level mobile robotic tasks like path planning and smart navigation. But the challenge of dynamic environment and huge amount of dense sensor data makes it hard to be implemented in a real-world application for long-term use. In this paper we present a novel mapping approach by incorporating semantic cuboid object detection and multi-view geometry information. The proposed system can precisely describe the incremental 3D environment in real-time and maintain a long-term map by extracting out moving objects. The representation of the map is a collection of sub-volumes which can be utilized to perform pose graph optimization to address the challenge of building a consistent and scalable map. These sub-volumes are first aligned by localization module and refined by fusing the active volumes using co-visible graph. With the proposed framework we can obtain the object-level constraints and propose a consistent obstacle mapping system combining multi-view geometry with obstacle detection to obtain robust static map in a complex environment. Public dataset and self-collected data demonstrate the efficiency and consistency of our proposed approach
Behavior of Two Foundry Cobalt-Based Alloys Exposed to a Hot Complex Gaseous Mixture Simulating the Atmosphere in a Waste-to-Energy Boiler. Part 1: Case of the Alloy Exposed to the Complex Gas Stream
Get PDFThe refractory materials required for waste-to-energy boilers endure severe working conditions, such as exposure to heat and hot oxidation / corrosion. Thanks to their high temperature properties cobalt-based alloys may respond to these properties requirements. In this work two model alloys based on cobalt and rich in chromium were elaborated by casting and samples were prepared by cutting and polishing. These samples were exposed, one to a hot complex gaseous mixture particularly aggressive reproducing the atmosphere in WtE boilers in service (presence of water vapor, di-oxygen, carbon di-oxide, hydrogen chloride), and the other to synthetic ashes, both for more than two hundreds hours. After test the samples were characterized by X-ray diffraction and SEM observations. On sample exposed to the complex gas stream a {10 to 15μm}-thick oxide scale formed on the surface of the sample exposed to the gas mixture. It involved all the elements of the alloy and it obviously developed both inwards and outwards as suggested by the position of the oxidized carbides
Behavior of Two Foundry Cobalt-Based Alloys Exposed to a Hot Complex Gaseous Mixture Simulating the Atmosphere in a Waste-to-Energy Boiler. Part 2: Case of the Alloy Immersed in Synthetic Ashes
Get PDFCurrently cobalt-based alloys are seemingly not really envisaged for constituting waste-to-energy boilers, although that the WtE working conditions are similar to those encountered in some applications in which Co-based superalloys are successfully used. To test the behavior of the cast chromium-rich cobalt-based alloys’ family, two model alloys belonging to the later one were cast and samples were exposed during more than ten days to a hot complex gaseous mixture and to synthetic ashes. After test the samples were characterized by X-ray diffraction and SEM observations. The results of the characterization of the first sample, the one exposed to the hot complex gaseous atmosphere, were presented in the first part of this work. This second part concerns the post-mortem analysis of the second sample, the one immersed in ashes. It appears first that this one was not protected by any external oxide scale. Instead, a mixture of oxides and chlorides formed and reaction between these corrosion products with ashes obviously led to an intermediate liquid phase. Internal oxidation/chloridation of the chromium carbides network obviously occurred over a 500μm-depth from the surface happened. The responsibility of an active oxidation mechanism analogous to what was earlier observed on steels is envisaged
Effects of Hot Strip Microstructure on the Deformation Microstructure and Textures after Cold Rolling in Ferritic Nonoriented Electrical Steels
Get PDFThe magnetic properties of electrical steels are related to the microstructure and texture of the final processed steel. There is an interplay and interaction of the microstructure and texture between the various processing steps. The ongoing structural changes at final annealing of the cold rolled material depend sensitively on the deformation structure after the cold rolling with high deformation. In this paper, we will study in detail the role of the microstructure of the hot strip on the deformation structure after cold rolling with high deformation
Microstructural Features and Wear Characteristics of Semi-Solid Processed A356 Aluminum Alloy
Get PDFIn the present study the microstructural features and tribological characteristics of hot forged A356 Al alloy subjected to SIMA (Strain induced melt activation) and T6 heat treatment (semi-solid) processes have been investigated. The SIMA process consists of hot forging of alloy at 325˚C followed by cold forging at room temperature, isothermal holding at 580˚C for 10 min and quenching. In case of T6 heat treatment, the hot forged alloy was solution treated at 540˚C for 4 hours followed by quenching in cold water and artificial aging at 155˚C for 3 hours. The microstructure of the alloy exhibited a spherical or globular morphology of the primary α-phase with uniform distribution of solutes in the interdendritic region. A detailed analysis of the solidification behaviour of the melt from semi-solid region of the alloy is reported. The reasons for the consequential changes in tribological properties of A356 Al alloy processed by SIMA andT6 heat treatment have been clearly brought out
Composite Materials and Structural Glass: Adhesion Phenomena
Get PDFThis study aims to investigate the adhesion phenomena between glass and composite materials, which - if they work in synergy – can increase the performance of glass structures, as regard both structural elements and the manufacture of joints. The experimental programme consisted of shear traction tests on all samples: glass-glass singlelap shear adhesion, glass-GFRP double-lap shear adhesion and glass-SRP shear adhesion. Different types of adhesive and various interface geometries were also tested to evaluate the ultimate force and identify fracture patterns with different bonding lengths. It was possible to identify the effective bonding length for each type of resin used to prepare test samples, by taking fracture load and average peel stress into account. Bonding length variations were also recorded. This enabled the values of bonding length to be verified analytically. Based on experimental results, a formula for the evaluation of delamination resistance and the optimal bonding length is proposed
Effect of Sublimation Temperature on the Photovoltaic Properties of Amorphous Carbon Thin Films from Fullerene
Get PDFThis paper presents the effects of sublimation temperature of C60 fullerene on the photovoltaic properties of amorphous carbon (a-C) films synthesized by remote plasma cracking. Here, we show that the deposition rate increases rapidly,Raman peak intensity corresponding to disordered fullerene becomes strong and the optical band gap increases with increasing the sublimation temperature. The photovoltaic devices with structure of Al/C60/a-C/ITO glass are fabricated with different sublimation temperatures and therelationship between the photovoltaic properties and the material properties of a-C films are discussed. It is shown that the improvementof power conversion efficiency is explained by low component of disorderedC60in amorphous carbon at lower sublimation temperature
Commercial Scale Solar Power Generation (5MW to 50 MW) and its Connection to Distribution Power Network in the United Kingdom
Get PDFOver the years, the contribution of solar photovoltaic systems to the power generation is expected to grow through household small scale, and commercial scale solar installation. Researcher pronouncing that delivering such a determination require greater motivation and innovation and much more dynamic power grid network to manage solar generation connection. This research work identifies and recommends the possibilities of applying proven technical know how to get the maximum from the existing power network economically. The simulated case study examples of various capacity connection requests was carried out to provide key insights on the problems faced by the PV farm connections in their line of business. This research is also an effort to give many answers to solar PV developers and enthusiasts who are not very technical and confused about different money saving connection options and the electrical constraints of the power grid. This study data can be used to provide recommendations to further enhance the growth of commercial scale solar power generation in the UK
Solar-Coal Hybrid for Steam Boiler
Get PDFSolar-coal hybrid is the use of solar and coal energy for producing steam for electricity as opposed to coal alone. The boiler feed-water is pre-heated using solar energy before introduced into the coal boiler, where the steam generating process is finalized for use in the electrical generating turbine. Reviewed is liquid-based direct absorption solar thermal collectors, in which incident sunlight is absorbed directly by the working fluid. Described is the amount of reduction in coal consumption, thus reduction in pollutant