Maintenance, Reliability and Condition Monitoring
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Numerical modeling of the stress-strain state of the ice beam by specified constitutive model
Get PDFIce cantilever beam is a generic construction component in cold region, referring recent decade research, many reports demonstrated ice mechanic characteristics separately, however, in most previous numerical simulations of ice material are based on the ‘Coulomb-Mohr’ constitutive models. In this article, author also used another ‘user defined constitutive model’ (‘Exponent’ temporary name), which is governed by “nonlinear isotropic harden power law” to simulate the ice cantilever beam mechanic behaviors. As per these numerical results, author made a few comparisons between ‘Coulomb-Mohr’ and ‘user defined’ model, all these compared results contain stress, strain, deformation items in elastic and plastic states respectively, in the meantime, author established series charts, such as ‘stress distributions on failure surface’, ‘dependance of loads with deformations’, ‘dependency of loads and flexural stress with equivalent and plastic strain’, etc., to prove the availability of ‘user defined’ constitutive model. Besides, author proposed some parameter assumptions for further research
An efficient solar water desalination system using natural vacuum pressure
Get PDFAn innovative design of a solar natural vacuum desalination (SNVD) system is proposed and investigated. To obtain a vacuum pressure in a desalination chamber its height is considered as 9.5 m. The waste heat in the system is efficiently utilized for both brine and distilled water. Seawater is preheated by the produced warm water, then, it is heated again by the outlet rejected hot brine before it is charged into the evaporation chamber. In addition, inlet pure water to a flat-plate collector is preheated by the condensation latent heat of the evaporated vapor from the evaporation chamber. Later, the outlet hot water from the collector is used as a heat source to the evaporation process. An optimum design of the system components was provided under the actual weather conditions for the shortest day of the year. It was found that the collector area is required to be 23 m2 to produce 66.6 liter of distilled water during. A mathematical modeling of the system was provided to establish a transient simulation and investigate the hourly performance of the system. Based on the annual performance of the system, the system can produce 76.5 liter of distilled water daily that is corresponding to 3.5 liter per one quadratic meter of collector. The annual average specific productivity of the system is obtained as 1.44 liter per kWh of solar radiation. Moreover, the maximum annual production is estimated as 92.88 liter of distilled water per day. Accordingly, the evaporation ratio (ER) is dependent on the solar irradiation and the annual average is found 0.0175 (or 1.75 %) where the gain output ratio (GOR) was estimated as 0.97 on yearly average basis
Traveling wave effect of multi-span through concrete-filled steel tubular arch bridge
Get PDFTo explore the different influence of traveling wave effect on the isolated and non-isolated arch bridge, the isolated and non-isolated multi-span arch bridges models are established respectively, three measured seismic waves were selected, and under the eight kinds of apparent wave velocities and multi-point consistent excitations, the structural responses of the two models, including the internal force response, the arch rib velocity, the pier’s internal force response, the bridge deck acceleration, and the shear force and displacement of isolation support of different arch ribs position in two models, were compared and analyzed. The results show that the isolation effect of the isolation structure is obvious; the wave effect of the isolated structure is significant, the two structures show different internal force response curves in different positions of the arch ribs under the influence of different seismic waves; the influence of the apparent wave velocity on the force and shock reduction rate of the arch ribs is complex; the vertical acceleration of the arch ribs and bridge deck of the isolated structure is reduced significantly; and the shear force and displacement of the isolation bearing increase with the increase of the apparent wave velocity. The study shows the traveling wave effect of multi-span through a concrete-filled steel tubular arch bridge with and without isolation, and the results will be used for the seismic design and analysis of structural diseases caused by the wave effect
Nonlinear dynamic analysis of constant-speed and variable-speed of autonomous vehicle passing uneven road
Get PDFThis paper focuses on the research about the comfort and safety of autonomous vehicles passing consecutive speed control humps (SCHs) at a highway, compares and analyzes the nonlinear dynamic characteristics of vehicles driving on uneven roads at a constant speed or with accelerations or decelerations. Firstly, a speed coupling excitation model of the consecutive SCHs and a four-degree-of-freedom (4-DOF) nonlinear vehicle suspension model are established, and then the numerical simulation is carried out by using the four-order fixed-step Runge-Kutta algorithm. The nonlinear dynamic characteristics are analyzed by means of a bifurcation diagram, phase portrait, Poincaré map, time history and power spectrum. Through the analysis, the relevant nonlinear motion characteristics and the speed critical conditions of chaotic vibration of autonomous vehicle suspension under these three conditions are obtained. The results show that chaotic motion may occur when the vehicle passes the uneven road in all three cases, and motion is not periodic during acceleration. Therefore, the vehicle should not accelerate passing continuous SCHs. The experimental results provide support for the follow-up researches of autonomous vehicle, because they give information on how to avoid chaotic motion, speed adaptive control, driving comfort and driving safety
“The tonic’s not always in a bottle”: a qualitative study investigating a heart rate variability biofeedback coherence intervention for individuals with gastrointestinal disorders
Get PDFGastrointestinal disorders (GID) affect psychological and physical health and can be impacted by stress and ability to self-regulate emotions. The aim of this study was to gain an in-depth understanding of individuals with GID experiences of a Heart Rate Variability biofeedback (HRV-BF) coherence intervention. Six patients, who had already been diagnosed with GID, were interviewed using a semi-structured interview schedule to investigate how engaging in an HRV-BF coherence intervention affected their levels of stress and their GID condition. All transcripts were explored using Interpretative Phenomenological Analysis (IPA). Analysis of the accounts indicated four superordinate themes: (1) Autonomy, (2) Self-regulation, (3) Acceptance, (4) Mind-Body-Spirit. The field of HRV-BF interventions in the area of gastroenterology is promising. However, it is recommended that further studies involving psycho-physiological interventions, with mixed-method designs and larger samples, are undertaken
Impact of outgassing and its corrective methods to improve the vacuum stability in the Coriolis Vibratory Gyroscope
Get PDFCoriolis Vibratory Gyroscope (CVG) is an inertial angular rate measurement sensor. CVG sensor comprises of metal coated hemispherical quartz vibrating structure as the rotation sensing element. It is forced to vibrate at one of its resonant modes by electrostatic excitation. Because of the limited flexibility of the quartz sensing element, the amplitude is limited to the submicron level. An ultra-high vacuum environment is required for the sensing element to sustain vibration for a long time. The criticality in the sensor development is to maintaining an ultra-high vacuum environment for the sensing element. Sensor suffers a problem of vacuum instability during the operation due to the outgassing from its components. This paper presents a novel approach in the identification of various outgassing sources that exist in the sensor, mitigation plan to minimize outgassing rate by selection of suitable raw material, suitable fabrication process of the components, and the surface characterization etc. The research work also presents the cost-effective experimental methodology to measure the outgassing rate from the sensor components to assess the CVG vacuum life, the requirement of the getter to maintain the ultra-high vacuum level throughout the CVG operation
Manufacturing of complex geometric structure metal matrix structures used for special purposes
Get PDFThree-dimensional (3D) production systems are making rapid progress and their needs are met in every field from the construction sector to the food sector. This technology is based on a hardware called the 3D printer which performs layered production. These printers are used in producing both prototypes and machine parts and mold tools. 3D prints can be produced using 3D printers with that are based on different technologies. These production systems have some disadvantages as well as the advantages they provide. Filament supported productions have a common problem if the fluid gets stuck in the flow line. In this study, screw extruder design and product development will be provided as a new generation production technology to be used in additive production as an innovative approach in additive manufacturing technology
The role of mechanical testing in additive manufacturing: review
Get PDFAdditive Manufacturing has become a new era of manufacturing technology that goes beyond traditional subtractive manufacturing. It is based on layer-by-layer material deposition technology. Additive manufacturing technology is widely used due to its various advantages such as accurate production in a short time, required product design and complexity, easy operation, rapid prototyping, etc. It is widely used in automobile industry, oil and electric power industry, aerospace industry, biomedical applications and many more. Mechanical testing plays an important role in understanding the complex relationships between basic process parameters, defects, and the final product of the AM process. Mechanical testing such as tensile testing, fatigue testing, torsion testing, hardness and impact tests etc. are crucial to determine various performance parameters of the component of product. Owing to increasing applications of additive manufacturing in various fields it is important to analyse the components produced for their mechanical performance and hence mechanical testing plays a very important role in additive manufacturing. This paper aims to review the various mechanical testing performed in the area of additive manufacture and available published data on the mechanical properties of additively manufactured components. This paper on AM processes discusses the mechanical properties of materials and current research