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[en] With the continuous progression of the advancement of new age airplane, great, high-productivity, and high adaptability have become predictable necessities for the gathering of fuselage segments. The customary gathering mode can't meet assembly necessities. As per the fuselage get together undertaking of a particular sort of airplane, this paper investigates the underlying attributes of the fuselage items, takes the situating of the cycle crossing point openings of the skeleton segments as the exploration object, receives the secluded plan thought, and plans a bunch of adaptable frameworks as per the prerequisites of framework capacities and specialized markers. The tooling framework understands the adaptability of the situating of meeting openings of the fuselage outline, establishing the framework for the programmed gathering of the center fuselage parts. The underlying attributes, specialized boundaries and utilitarian pointers of the fuselage segments in the airplane, the item prerequisites for tooling are investigated, four diverse adaptable tooling plans are proposed, and the different plans are gauged and looked at through hypothetical examination and trials. An adaptable tooling test stage was constructed, equipment troubleshooting, boundary setup and program configuration were finished, the movement control of every servo hub was understood, the control plan of the servo framework was checked, and the situating mistake model of the test stage was set up. The instrument adjusts the portable unit of the tooling, positioning accuracy of 0.05mm. (author)
[en] Knowing the engineering properties of geomaterials is imperative to make the right decision while designing and executing any geotechnical project. For the economical and safe geotechnical design, quick characterization of the compressibility properties of the cohesive soil is often desirable; these properties are indeed tedious to determine through actual tests. Therefore, correlating the consolidation parameters of the soils with its index properties has a great significance in the geotechnical engineering field. Several attempts have been made in the past to develop correlations between the consolidation parameters and index properties of the cohesive soils, within certain limitations. However, there is still a need to develop such correlations based on the extensive database, composing of unified plasticity range of soils, i.e., low to high plasticity. In the current study, 148 undisturbed soil specimens were obtained from different areas of Pakistan. Out of which 120 samples were utilized to develop correlations, and 28 samples were used to check the validity of the developed correlations. In order to enhance the index properties database, 30 more bentonite mixed soil samples were prepared and tested accordingly. Correlations to envisage different consolidation parameters such as compression index, compression ratio and coefficient of volume compressibility were developed using 150 cohesive soil samples of low to high plasticity. In addition, the performance of these developed correlations was verified on a set of 40 soil samples and compared with the performance of different correlations available in the literature. The percentage deviation in the prediction of compressibility characteristics through developed correlations in the present study was found to be very less, which endorsed the excellent reliability of the developed correlations. (author)
[en] The aim of this research is to study the machinability aspects of hardened AISI 4340 High Strength Low Alloy (HSLA) steel (50 ± 2 HRC (Hardness Rockwell C)). The experimental investigation using coated carbide inserts is carried out during the dry hard milling process in a sustainable environment. The input parameters in the study are speed, feed rate and depth of cut and the responses are Average surface Roughness (Ra) and Material Removal Rate (MRR) that are selected through screening. Central Composite Design (CCD) in response surface methodology has been utilized as the experimental design technique with twenty experiments. Analysis of variance has been employed to examine the momentous machining parameters and responses. A mathematical model has been developed to optimize the surface roughness and material removal rate. It has been observed that the most significant factor for Ra is feed rate while for MRR depth of cut is the most significant factor. The results show that the minimum value of Ra ~ 0.098 µm is achieved at speed ~ 1000 RPM, feed rate ~ 300 mm/min and depth of cut ~ 0.2 mm while the maximum value of MRR ~ 6.35 cm3/min is attained at feed rate ~ 500mm/min and depth of cut ~ 0.4 mm regarding less or no effect of speed ~ 500-1000 RPM. The average forecast error for the validation information has been observed to be 3.35%. for Ra and 3.2% for MRR. Further, it is investigated that good surface finish like grinding and dimensional accuracy can be achieved with coated carbide tools. (author)
[en] This paper investigates the trajectory tracking problem for a Multi-Input Multi-Output (MIMO) Twin Rotor Aerodynamic System (TRAS) using a hybrid architecture based on an H∞controller and Iterative Learning Control (ILC). TRAS is a fast, nonlinear coupled system and therefore it is a challenging task to design a control system that ensures the tracking for fast changing trajectories. The controllers proposed in the literature for the TRAS through linear approaches tend to have a large control effort, while the ones designed using the nonlinear approaches track only for smooth input trajectories. Both issues are important from control point of view. In this paper, these issues are addressed by designing a feedback H∞control that stabilizes the system and a feedforward ILC which reduces the control effort. The H∞controller achieves the tracking for input trajectories with sharp edges, but the control effort required for tracking is large. With the proposed hybrid approach, tracking is achieved by the H∞controller whereas the required control effort is reduced in each subsequent iteration by ILC. After a few iterations, accurate tracking at a minimized control effort is achieved. The simulations have been performed using MATLAB software and the controller designed through the proposed approach has been validated on nonlinear model of the system. The results of the proposed technique, compared with the flatness-based and back-stepping control strategies, show that the proposed controller ensures accurate tracking at the reduced control effort. (author)
[en] The energy dissipation capacity of concrete is an important aspect for a Reinforced Concrete (RC) structure to be seismically resistant. Various types of concrete incorporating sustainable materials are being developed these days such as recycled aggregate concrete. Determination of energy dissipation capacity of such new types of concrete is of great importance for their application in RC structures which are to be constructed in seismically active areas. In this regard, the experimental study presented in this contribution investigated the energy dissipation capacity of RC beams constructed using recycled aggregate concrete and subjected to three different deflection amplitude levels of reverse cyclic flexural loading. For this purpose, a total of 20 RC beams of cross section 75 x 150 mm and length of 1350 mm were cast using five different concrete compositions and tested. Among five different concrete compositions, one was control concrete containing 100% natural aggregates while the remaining four compositions were of recycled aggregate concrete containing natural and recycled aggregates. Four replacement levels (25%, 50%, 75%, and 100%) of natural aggregates with recycled aggregates were examined. Results indicated that the amplitude level of imposed deflection is an important factor which influenced the value of energy dissipated by RC beams. Further, results showed that RC beam constructed using recycled aggregate concrete containing 25% recycled aggregates exhibited energy dissipation capacity similar to or even better than that of control RC beam containing 100% natural aggregates. (author)
[en] An adapted heat source model is developed for transient thermal numerical analysis of electron beam welded nickel-based alloy with increased susceptibility to hot cracking. The model enables the consideration of heat redistribution due to beam deflection phenomena. The modeling concept is validated by the appropriate theoretical models and in addition, experimental studies especially performed for this purpose. Special attention is given to the calibration of heat source model parameters. The calibration procedure is based on a statistical approach involving a combination of novel analytical solutions and quasi-steady state finite element models. The model parameter field is statistically analyzed, and a prediction algorithm is developed using optimization algorithms from the six sigma theory. The reliability and practicability of the model is demonstrated by validation weldments. The work is dedicated to precisely calculating the temperature field in the high temperature region around the weld pool and thus to provide a more detailed explanation of the formation of hot cracks when welding turbine materials commonly used in industry and aircraft constructions.
[en] Obtaining accurate experimental data from Lagrangian tracking and tomographic velocimetry requires an accurate camera calibration consistent over multiple views. Established calibration procedures are often challenging to implement when the length scale of the measurement volume exceeds that of a typical laboratory experiment. Here, we combine tools developed in computer vision and non-linear camera mappings used in experimental fluid mechanics, to successfully calibrate a four-camera setup that is imaging inside a large tank of dimensions . The calibration procedure uses a planar checkerboard that is arbitrarily positioned at unknown locations and orientations. The method can be applied to any number of cameras. The parameters of the calibration yields direct estimates of the positions and orientations of the four cameras as well as the focal lengths of the lenses. These parameters are used to assess the quality of the calibration. The calibration allows us to perform accurate and consistent linear ray-tracing, which we use to triangulate and track fish inside the large tank. An open-source implementation of the calibration in MATLAB is available. Graphic abstract: .
[en] In this study, we propose a method to reconstruct pressure fields from planar particle image velocimetry measurements for laminar flows by employing semi-implicit method for pressure-linked equations algorithm to solve governing equations where measured velocities are inherently used as boundary conditions. The method starts with interpolating the measured velocity field on a staggered computational grid. The continuity equation, in the form of pressure equation for incompressible flows, is solved with this velocity data to reach an initial pressure field. Momentum equations are solved with calculated pressure field and then pressure correction equation is solved for calculating the mass imbalance in continuity equation. Using this mass imbalance, the current velocity field is corrected. Repeating this procedure until convergence provides not only the pressure field that satisfies governing equations, but also error reduction on the measured velocity. The method is validated with theoretical flows and its sensitivity to the velocity field error is assessed. This method reconstructs the pressure fields exactly for error-free velocity fields and can correct the flow-fields to accurate values even with extremely high experimental errors. Application on a flapping airfoil experiment showed that the method can successfully reconstruct pressure field by slightly altering the measured velocity field. The proposed method offers a non-intrusive, global pressure measurement for laminar flows with minimum end user input. Graphic abstract: .
[en] In this paper we present a study on the mechanical properties of nanodiamond enhanced tungsten strengthened aluminium alloy 7075, stored for 28 months under different conditions. One of the samples was stored in terrestrial conditions and the other sample was mounted on the outside of the International Space Station for the same period. The purpose of the experiment is to determine tensile strength, Young’s modulus and Poisson's ratio using different testing procedures and to compare the results with those obtained using the ultrasonic volumetric method Key words: aluminium and alloys, nanodiamond, ultrasonic volumetric method, tensile strength, outer space structures
[en] Internal gas-liquid two-phase flow is commonly observed in various engineering disciplines. One of its unique characteristics is the presence of flow regime, and its identification is crucial for improving the accuracy of thermal-hydraulic analysis codes as well as securing the integrity of piping systems. Furthermore, transition of two-phase flow regime takes place gradually, and is highly unsteady phenomenon, objective flow regime identification near the transition region still remains challenging to this day. In the present study, we developed the novel flow regime identification method based on the state-of-the-art AI technique which is fully automated and capable of detecting bubble characteristics from high-speed images at high accuracy. The present tool was developed based on a machine learning algorithm, which can quickly detect flow characteristics and capture individual bubble positions from given images. Furthermore, it is possible to calculate major two-phase flow parameters such as void fraction and bubble rise velocity using the detection results. By utilizing the current tool, instant objective two-phase flow feature extraction is now possible, and our results showed promising performance by coupling the state-of-the-art AI technique with conventional thermal-hydraulics. (author)