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Statistical Analysis of Adhesive Bond Parameters in a Single Lap Joint System
Get PDFThe design and sizing of adhesives used for bonding of two or more similar/dissimilar materials in aerospace and automobile structural engineering studies have always been important. A vast number of studies have reported via experimental, numerical, and analytical methods of lap joint system with adhesive bonding. Optimization studies of the adhesives used in joints are highly necessary which can be done either with numerical or experimental data in determining the suitable parameters for the specified solution through the design of experiments analysis. In this study, a single lap joint with different variables has been modelled and the resulting stress was measured in each case. A standard two-dimensional plane stress element was used for modelling of single lap joint stress elements. Furthermore, a statistical analysis method was used to optimize the selected parameters for the improvement of current solutions with suitable parameters. The results showed that the response values of stresses were influenced by input parametric variables which control the stresses and reduces the risk of damage to the adhesive bonds used in the joints. Moreover, based on the present optimization results it has been found that the thick adhesive bond will result in higher shear stress transfer with less width and suitable for the lower applied voltage
Influence of the Base Element on the Thermal Properties of Non- Ferrous Chromium-Rich TaC-Containing Alloys Elaborated by Conventional Casting: Part 1: Thermodynamic Approach, Melting Ranges, as-Cast Microstructures and Thermal Expansion
Get PDFAfter preliminary thermodynamic calculations for verifying their refractoriness, six (Ni,Co)-based alloys were synthesized by casting. They contain chromium, carbon and tantalum to achieve interesting chemical and mechanical high temperature properties. Their microstructures in the as-cast state were observed by electron microscopy (SEM) to discover the carbides characteristics. Differential thermal analysis (DTA) was carried out for all of them to assess their melting points notably, for having better knowledge about the level of high temperature at which they can be used potentially. Thereafter thermomechanical analyses (TMA) were run to explore their behaviour in thermal expansion. As shown by the thermodynamic calculations all the alloys are theoretically possible to be shaped by conventional foundry due to liquidus temperatures all below 1400°C. According to these same results, the solidus temperatures of all alloys would stay over 1250°C, this suggesting that all alloys would be able to be used under moderate mechanical stresses at temperatures as high as 1200°C. As suggested by calculations, the as-cast microstructures are all dendritic and the interdendritic spaces are occupied by carbides. According to calculations again, the Ni-richest alloys contain chromium carbides, but tantalum carbides are also present, a presence which was not expected. In contrast the Co-richest versions contain only TaC carbides. The DTA experiments show that the solidus and liquidus temperatures both increase by going from the Ni-richest alloys to the Co-richest ones. The TMA experiments demonstrate that the thermal expansions and thermal contractions are rather continuous, without any irregularities, and the average thermal expansion coefficients, all close to 20 × 10-6K-1, do not systematically depend on the respective proportions of nickel and cobalt. This first part of the whole work will be followed by two other parts dealing with the effect of these Ni and Co proportions on the high temperature oxidation phenomena, for temperature variations and for isothermal conditions respectively
Analysis of EXAFS Spectra of Crystalline Copper using Classical Anharmonic Correlated Einstein Model
Get PDFIn this work, the temperature dependence of extended X-ray absorption fine structure (EXAFS) of the crystalline copper structure was calculated and analyzed using the anharmonic correlated Einstein model and the classical statistical theory. The thermodynamic parameters of a system are derived from an anharmonic effective potential that has taken into account the influence of all nearest neighbors of absorbing and backscattering atoms in the crystal lattice with thermal vibrations, where the Morse potential is assumed to characterize the interactions between each pair of atoms and the function of anharmonic EXAFS spectra presented in terms of the cumulant expansion up to the fourth-order. Analytical expressions for the first four cumulants and their contribution to amplitude reduction and phase shift obtained in the simple form of the mean-square relative displacement or the correlated Einstein frequency. The numerical results for crystalline copper were in good agreement with those obtained by the other theoretical procedures and experiments at several temperatures. The analytical results show that this calculation model is useful to reduce measurement and data analysis of experimental EXAFS spectra
Automatic Reconstruction of Building-Scale Indoor 3D Environment with a Deep-Reinforcement-Learning-Based Mobile Robot
Get PDFThe aim of this paper is to digitize the environments in which humans live, at low cost, and reconstruct highly accurate three-dimensional environments that are based on those in the real world. This three-dimensional content can be used such as for virtual reality environments and three-dimensional maps for automatic driving systems.
In general, however, a three-dimensional environment must be carefully reconstructed by manually moving the sensors used to first scan the real environment on which the three-dimensional one is based. This is done so that every corner of an entire area can be measured, but time and costs increase as the area expands. Therefore, a system that creates three-dimensional content that is based on real-world large-scale buildings at low cost is proposed. This involves automatically scanning the indoors with a mobile robot that uses low-cost sensors and generating 3D point clouds.
When the robot reaches an appropriate measurement position, it collects the three-dimensional data of shapes observable from that position by using a 3D sensor and 360-degree panoramic camera. The problem of determining an appropriate measurement position is called the “next best view problem,” and it is difficult to solve in a complicated indoor environment. To deal with this problem, a deep reinforcement learning method is employed. It combines reinforcement learning, with which an autonomous agent learns strategies for selecting behavior, and deep learning done using a neural network. As a result, 3D point cloud data can be generated with better quality than the conventional rule-based approach
Optoelectrical Properties of NiInZnO (NIZO) Thin Films
Get PDFThis report presents the fabrication and characterization of x % Ni - InZnO (NIZO) Schottky diodes. The structural, optical and electrical properties of the fabricate Al/p-Si / x % Ni - InZnO /Au photodiodes were investigated. An average visible transmittance of about 75% - 85% has been obtained in the visible-light to near-infrared wavelength region. The optical bandgap was 3.17 ± 0.02 eV. Current-Voltage measurements were conducted to analyze the photodiode behavior under dark and light illumination. The reverse bias current increases together with increasing light illumination. The observed I-V results confirm the photoconductive and photovoltaic properties of the fabricated diode. There is an exponential relationship between the current and the voltage in the forward bias, confirming the rectification performance of the photodiode. The electrical properties of the fabricated photodiodes were evaluated using Cheung- Cheung and Norde’s methods. The transient photocurrent, capacitance-voltage-frequency and conductance-voltagefrequency plots indicate that the diode is very sensitive to light illumination. We also observe a strong correlation between capacitance and conductance on frequency, this was explained based on the presence of interface states. The obtained results suggest that the Ni-doped InZnO photodiodes can be useful in photovoltaic and optoelectronic applications
Efficient Selection Method for Mass Scaling Factor in 3D Microscopic Cutting Simulation of CFRP
Get PDF3D microscopic cutting simulation of CFRP is very important for revealing material removal mechanism and damage suppression, wherein mass scaling is usually adopted for solving the problem of extremely low calculating efficiency. For the simulation with very low cutting speed, a quasi-static criterion is usually adopted for an appropriate mass scaling factor. However, to get closer to real machining processes, there is tendency of simulation with higher cutting speed considering more complicated factors, and the selection of mass scaling factor in this situation is difficult and computationally intensive. To solve this problem, this study aims to propose an efficient method of appropriately selecting mass scaling factor, which is upon the kinetic-to-internal energy ratio in the beginning stage of simulation. Through direct relationship between kinetic energy and cutting speed, the selection method applies under different cutting speeds; with the focus on the beginning stage of calculation, the proposed method requires little calculating work. By verification, such advantages are clearly presented with obviously improved calculating efficiency and limited error. What’s more, a set of empirical values of mass scaling factor suitable for different cutting speeds are provided for reference. The findings of this study could make great contributions in facilitating the development of 3D microscopic cutting simulation method of CFRP
In-Situ Synthesis of Polymer–Clay Nanocomposites: Exfoliation of Organophilic Montmorillonite Nanolayers in Poly 2-ThiozylMethacrylamide
Get PDFThe aim of this work is the preparation and properties of poly 2-thiozyl methacrylamidevinylbenzyldimethyloctadecylammonium/montmorillonite (TMAAm-VBOA/MMT) nanocomposites. Firstly 2-thiozyl methacrylamide (TMAAm) monomer was synthesized by reacting 2-amino thiazole with methacryloyl chloride in the presence of triethylamine. Synthesis of nanocomposites were performed in three steps which are; purification and cation exchange capacity (CEC) determination of clay, preparation of organoclay and synthesis of nanocomposites. Nanocomposites with various amounts of TMAAm and VBOA/MMT were synthesized through in-situ and free radical polymerization using benzoyl peroxide as an initiator. Changes in the structure of the nanocomposites were examined through Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Additionally, thermogravimetric analysis and BET analysis were conducted to investigate the thermal properties and particle size distribution of the nanocomposites. The results of X-ray and SEM analysis suggest that the exfoliated structure of the new nanocomposite materials. In addition, the thermal decomposition temperatures of nanocomposites were found to be higher than that of pure organoclay and poly(TMAAm) and thermally degradation rate decreased
Conceptualization and Prototyping of Unmanned Amphibious Aerial Vehicle for Water Quality Assessment
Get PDFUnmanned Amphibious Aerial Vehicles (UAAV) are gaining significant interest in accessing remote water bodies and an ideal tool for limnologist in water quality assessment. In this article, conceptualization of UAAV by inculcating the principle of hovercraft and multirotor system is carried out in a systematic approach. The unconventional configuration of UAAV makes the conceptual stage as a challenging task in the design process. In order to overcome the challenges and strapped configuration of vehicle design, the authors exploited the design process, Thirteen conceptual models are evolved and the best UAAV design model is selected based on stability, provision for accommodating payload, endurance, air cushioning effect for effective gliding along the water bodies, payload carrying capacity and modularity in construction. In addition, design of payload bay, selection of material, estimation of endurance and center of gravity calculations are carried out for those designs. The finalized conceptual models are constructed and performance of amphibious vehicles is investigated for varying the payload. The conglomerate designs of UAAV are evaluated for the design requirements and the computational fluid dynamic (CFD) analysis is performed to measure its performance characteristics. The experimental prototype of UAAV is custom built to demonstrate the competency of UAAV through flying in air and hovering in water. The test results suggested that, the developed UAAV has tremendous impact on minimizing the efforts of human being in inspecting remote water bodies in proficient way
Design and Evaluation of a Concentrated Solar-Powered Thermal-Pasteurization System
Get PDFA device has been designed, constructed, and tested for heating fluids using solar energy. The device heats water to levels to kill pathogens by a parabolic reflecting surface that concentrates solar energy along an axis. Among the components that increase the thermal performance of the system is a thermally actuated valve, which controls the temperature and the thermal exposure duration of the fluid to cause deactivation of targeted pathogens. Also, a novel fluid-to-fluid heat exchanger arranged in counter flow is used.
Experiments were performed with a water solution containing non-pathogenic Escherichia coli K-12 MG1655 (E. coli) bacteria. The results showed that the system is capable of pasteurization to levels where no living pathogens were detected in the heated fluid. The experiments were carried out over a wide range of temperatures and exposure durations to test the device and the underlying mathematical model. E. coli log reductions greater than 1 were achieved in all cases and it is shown that arbitrary values of reduction can be achieved with appropriate temperature/time settings
Influence of the Base Element on the Thermal Properties of Non- Ferrous Chromium-Rich TaC-Containing Alloys Elaborated by Conventional Casting: Part 2: Thermogravimetric and Metallographic Study of the Oxidation Start and of the Oxide Scale Spallation
Get PDFAfter a first part devoted to the study of several thermal chemical and mechanical characteristics of the six (xCo-yNi, bal.)-25Cr-0.4C-6Ta alloys, this second part of their study deals with the oxidation behaviour of these alloys in presence of heating or of cooling. The heating and cooling parts of thermogravimetry files of oxidation tests of which the isothermal parts were earlier studied, were analysed by plotting mass variation versus temperature. During heating the oxidation starts and a first mass gain is achieved prior to the isothermal stage. They are slightly influenced by the Co/Ni ratio. During the cooling oxide scale spallation happens for all alloys. For the nickel-richest alloys this phenomenon takes place for a temperature less decreased in comparison to the cobalt-based alloys. The fall in mass due to the loss of oxides by spallation seems a little higher for the nickel-richest alloys than that for the cobalt-richest ones. More than to differences in thermal expansion coefficient, this difference may be linked to the oxidation-induced mass gain achieved prior to spallation start, which is higher for the cobalt-richest alloys than for the nickel-richest ones