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[en] FRC (Fibre Reinforced Concrete) is fibrous material which increases its structural integrity, resists explosive spalling in case of environmental affects, improves mix cohesion, improves ductility, reduces steel reinforcement requirements and reduces the voids due to good stiffness. It contains short discrete fibres that are uniformly distributed. Mostly, natural fibers are the waste material which may have negative impact on environment. Synthetic fibres include steel fibres and glass fibres but natural fibres are coconut fibres and human hair fibres which tend to vary the properties to concrete. In addition, the character of FRC changes with varying concrete, fibre material, geometries, distribution, orientation and densities. Hair fibre concrete gives a practical, cost-effective and convenient method to avoid cracks and deficiencies regarding strength and proper mixing ratio which occurs at a longer period. Fibres have been used to reduce plastic shrinkage and drying shrinkage in concrete. In some structural elements, fibrous concrete can be used to reduce the cost of structure. Different fibres are used to improve the tensile strength of concrete. Human hair are strong in tension. Hair fibres can be utilized as a strengthening material. Hair fibre is a non decayable matter and available at a cheap rate. Experiments have been performed on fibrous concrete cylinders containing various percentages of human hair which is 0, 0.5, 1 and 1.5 percent by the weight of cement. A total of seventy-two cylinders have been prepared with FRC having different percentages of hair content. Workability, compressive strength and split tensile strength have been checked at three curing ages i.e. 7, 14 and 28 days. This research will open a new wicket in the horizon of reuse of waste material efficiently in construction industry. This innovation in construction industry will save our natural resources and use fibre in productive and an effective approach. (author)
[en] Power plant machinery can be dynamically decoupled from the substructure by the effective use of vibration isolation systems. These isolation systems can be used in turbine foundations, coal mills, boiler feed pumps or other equipment foundations to mitigate the transmission of operational vibration. The application of helical steel springs and viscous dampers as elastic support systems may also be used to protect against earthquakes and other catastrophic events, such as airplane crash. This article illustrates basic principles of 3dimensional elastic support systems and applications on power plant equipment and buildings in medium and high seismic areas.
[en] Modern, lean and premixed gas turbine combustion concepts for low NOx emissions are prone to combustion instabilities. In a previous work it was shown that laser interferometric vibrometry (LIV) can be used to record global as well as local heat release fluctuations in swirl-stabilized premixed methane flames quantitatively, if other effects influencing density are small. In this work a newly developed camera-based full-field LIV system (CLIV) was applied to a lean, confined, premixed and swirl-stabilized methane flame under atmospheric conditions. Instead of time-consuming pointwise scanning of the flame, CLIV records full-field line-of-sight density fluctuations with high spatio-temporal resolution. With a recording rate of 200 kHz, CLIV enables the visualization of highly unsteady processes in fluid dynamics and combustion research. As an example for an unsteady process, the propagation of the flame front through a lean, premixed gas volume is visualized during an ignition process. A discussion of algorithms and assumptions necessary to calculate heat release oscillations from density oscillations is presented and applied to phase-averaged data recorded with CLIV for this type of flame. As reference, OH* chemiluminescence data were recorded simultaneously. While density gradients travelling with the flow are recorded by LIV and CLIV, chemiluminescence imaging will show nothing in the absence of chemical reaction.
Graphic abstracta Time-averaged density gradient within the combustor in lateral direction. b Density fluctuations along line-of-sight 7 ms after ignition. c Phase-averaged and local heat release fluctuations at 225 Hz perturbation frequency .
[en] This review summarizes state-of-the-art knowledge on fast-responding pressure-sensitive paint (fast PSP), which has evolved into a powerful experimental tool for studying complex flow problems. As the formulation of porous paint with kilohertz response is now well established, full-field pressure measurements with high spatial and temporal resolution have been achieved on both stationary and moving targets. Recent studies have significantly advanced every aspect of this technology, including paint development, theoretical modeling, system integration and data processing. Novel paint formulations with superior sensing properties and additional functions for multi-physical measurements are being continually developed. The dynamic response mechanism is better understood through analysis and modeling considering the processes of photoluminescence, gas diffusion and light transmission. More importantly, applications of fast PSP are being expanded from regular wind-tunnel tests to more challenging conditions featuring hypervelocity, fast rotation and high temperature. Interdisciplinary research has played a key role in these development processes, and will remain vital for future breakthroughs in PSP technology. Graphic abstract: .
[en] The residual stresses in welded joints are a common cause for breaking down after repeated loading of the joint. The neutron diffraction method for residual stresses measurement is non-destructive and allows measurement at great depth under the surface with a good precision. The aim of this work is to present the results of residual stress measurement via neutron diffraction method of specimens of low carbon steel, which were electron beam welded with different welding speed. The three components of the residual stress tensor were measured. The maximum values are at the component along the weld and closest to the welding seam. The residual stresses depend on the technological parameters of the welding – they decrease with increasing the welding speed. Key words: residual stresses, neutron diffraction, electron beam welding, steel
[en] In this paper, we propose a method for numerically evaluating the probability of failure from the diagnostic results of condition monitoring using the Bayesian theorem. When performing maintenance using real-time monitoring results, a diagnostic result without any inspection error is ideal. However, failure is not caused even if the monitoring method sufficiently overestimates any small damage that can cause failure. Moreover, failure is not caused even if the method slightly underestimates large damage. In other words, for reducing the probability of failure, improving the accuracy of estimating specific damage levels is necessary. In this study, a method for reducing the risk by improving the diagnostic accuracy of specific damage levels by means of controlling the sampling ratio of the training data employed for learning the use of a weight function is proposed. The consequences of overestimation and underestimation of damage differ. The risk caused by underestimation is called failure risk and that caused by overestimation is called economic risk. In this paper, the effect of weighted regression on risk reduction is discussed. The proposed method is validated by employing it to identify delamination in a CFRP beam via the electric potential change method. (author)
[en] A conceptual design of Passive Containment Cooling System with Closed-Loop Heat Pipe Technology (PCSHP) is studied using both experimental and computational methods. By studying on the thermal-hydraulic parameters in system running, such as temperature, pressure and flow rate, the paper mainly focuses on the start-up characteristics, the steady-state operating characteristics, the heat transfer capacity and the natural circulation capacity of the system. Hence, the principle experiment and GOTHIC simulation are carried out under start-up conditions, steady-state conditions and decay heat simulation conditions. The applicability and conservatism of the GOTHIC model is evaluated by comparing the simulating results with the experimental results. The rationality of the system design is validated by both the principle experiment and GOTHIC simulation. It is preliminarily judged that the heat pipe technology is feasible to apply to the Passive Containment Cooling System (PCCS) of nuclear power plant.
[en] The ultrasonic testing (UT) is a major nondestructive technique for inservice inspection (ISI) of light water nuclear power plants in Japan and conventional UT techniques (A-scan display type UT instrument) have mainly been used. In recent years, although ultrasonic testing using phased array technology has been applied to other non-nuclear fields, it is not actively applied to detect cracks in ISI. Despite scope to use phased array technology according to codes and regulations, the technology is only applicable to special cases such as crack depth sizing or vessel internal inspections and the lack of demonstration data for field applications hinders application of the technology. In this basic study, crack detectability is compared between the phased array UT technique and the conventional UT method and a method for fabricating a crack induced specimen usable to detect defects was developed. When replacing the conventional method with phased array technology under the same conditions, the detectability is approximately equivalent to or improved compared to the focused area. When the sensitivity is confirmed by calibration, although detection of the crack sought is possible, it is preferable to consider calibration not only via a side drilled hole but also a notch to compare with the conventional UT method. (author)
[en] Traffic regulations on the roads mostly aim to ensure the safety of road users. Vehicles may come across many traffic lights (TL) on their way, and some of them will reach TLs in the green phase when others are in yellow/red phases. Reaching a traffic light on the yellow or the red phase means a loss of inertia or kinetic energy that could also be interpreted as a loss of fuel because after the light turns green, the vehicle will resume its normal speed using extra fuel (compared to moving without stopping at traffic light). The economic reasoning may seem negligible to some, but in case of heavy cars or trucks, stopping can be very expensive, especially when fully loaded. Another effect of such movement interruptions is safety leakages. In some cases, drivers could simply be late after a slow down. Moreover, the slowing down that is required to stop the vehicle at traffic lights forces the driver to undergo unhealthy deceleration. One of the simple solutions of the given problem is to change the route from a disallowed to an allowed one at traffic lights; in contrast to moving directly on the route that will require the driver to stop and wait for a red light, a heavy truck can turn right or left in order to take a slightly longer route if possible, thereby increasing its travel distance but saving inertia. This study proposed an alternative solution to the described problem as an intelligent speed control that mostly relies on knowing the traffic light's state and aims to control the vehicle's speed in such a way that it always tries to reach the traffic light in its green phase. (author)
[en] The aim of the project 4717R01361 "System validation of safety functions of software-based crane control systems" was to develop a method for validating the correct implementation of the safety functions of the control system of a crane. As a first step, the rules and regulations to be applied for the design of the control system for lifting equipment in nuclear power plants were compiled. The central regulations are KTA Safety Standards 3902 and 3903, with KTA 3902 giving the specific requirements on the design of safety functions. For each safety function a performance levels as defined in DIN ISO 13849-1 is assigned. DIN ISO 13849-1 contains instructions for calculating the performance levels depending on reliability parameters and the concept of the control system. Alternatively, Safety Integrity Levels as defined in DIN EN 61508 can be used. Specifications for the design of the electrical safety functions and devices with a focus on the deterministic, electrotechnical parameters can be found in DIN EN 60204-32. The typical lifting equipment in German nuclea power plants, for which increased or additional requirements in the sense of KTA 3902 are made, were determined. For increased requirements, these are the reactor building cranes, the semi-gantry cranes in the outside area of pressurized water reactors and, in some cases, the cranes in the interim storage. The number of cranes with additional requirements as specified in KTA 3902 is larger and depends on the individual plant. Separate requirements are specified in KTA 3902 for the fuel assembly loading machines. The reactor building cranes, the fuel assembly loading machines, the interim storage cranes and the lifting equipment used in the treatment of radioactive waste shall be classified as relevant for decommissioning. For the other lifting equipment this depends on the plant-specific decommissioning concept. German and international events from nuclear power plants were assessed in order to evaluate the specific operating experience of cranes. For the evaluation period, a total of 135 events with faults or failures in lifting equipment were found. These events were categorized and grouped according to their consequence, the equipment causing the failure the type of failure and whether the control system played a role in the failure. Observed failure consequences were load crashes, collisions with surrounding elements, unplanned connections between hoist and load (both collisions and unplanned lifting operations), self-inflicted damages and ineffective nuclear-specific interlocks (related to radiation protection or criticality safety). The events where the control system of the lifting equipment played a role were then evaluated in a more detailed manner. It turned out that failures in the control system rarely lead to load crashes, but often to self-inflicted damages and collisions with surrounding elements. Regarding the type of failure, design errors were relatively common. The events could be further divided into four sub-groups: 1. component failures, in which individual (in a few cases: several) physical components failed. 2. programming errors, in which the software of the control system contained logical or calculation errors. 3. parameterization errors, in which impermissible values were assigned to variables in the soft-ware of the control system and 4. specification errors, in which the safety function was not implemented at all or not implemented with the specified reliability. Various model-based methods for the analysis of digital crane control systems were developed and tested. The pre-selection of the analysis methods was based on the experience already gained at GRS in the field of analyzing digital I&C systems in nuclear power plants. Subsequently, a simplified model of a crane system and the corresponding crane control system was developed. The testing of analysis methods based on the mod-elled crane control system was then carried out in three steps: Model-based Failure Mode and Effects Analysis (FMEA), Fault tree modelling and analysis, Analysis of a simulated crane control system (simulation analysis). As expected, the methods given above have fundamentally demonstrated their suitability for model-based analysis of potential failures of I&C components of the control system. Based on the assumptions made, the FMEA can help to determine the effects of potential individual faults on the function of the modelled crane control system and/or candidates for systematic failures (Common Cause Failure, CCF). The fault tree analyses essentially provided the failure combinations of SILT components that can lead to load crashes. For the fault tree modeling, results of the model based FMEA were used as basic elements. The quantification was based on estimates. The sensitivity and minimal cut set analyses of the fault tree analysis carried out in the project are particularly important for the model-based analyses, because they also allow for the identification and reduction of the model uncertainties. The simulation analyses offer essential extensions for analyses of dynamic processes during crane system movements and for the validation of FMEA and fault tree analyses. During the modelling of the crane control system it was already determined that a lot of detailed information on the design and function of individual components as well as of the entire crane system is required for the application of the analysis methods. This includes information on the operation and testing of the crane system and its control system, on the monitoring of the crane system and reliability data from the manufacturer or from operating experience. In order to evaluate the effectiveness of individual functions of the crane control system, a consistent, comprehensive modelling of the crane system, the movement space and the loads to be moved is required. A further improvement of the significance of the model-based fault tree and simulation analysis can be achieved by taking into account the operational functions of the crane control system and the mechanical safety devices when modelling the crane and its control system. This allows the potential hazards and, if necessary, the extent of damage to be estimated in a meaningful way. This assessment is not yet possible given the current state of model of the crane system developed in this project.