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Number of results: 258
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Abstract

An attempt is made in the current research to obtain the fundamental buckling torque and the associated buckled shape of an annular plate. The plate is subjected to a torque on its outer edge. An isotropic homogeneous plate is considered. The governing equations of the plate in polar coordinates are established with the aid of the Mindlin plate theory. Deformations and stresses of the plate prior to buckling are determined using the axisymmetric flatness conditions. Small perturbations are then applied to construct the linearised stability equations which govern the onset of buckling. To solve the highly coupled equations in terms of displacements and rotations, periodic auxiliary functions and the generalised differential quadrature method are applied. The coupled linear algebraic equations are a set of homogeneous equations dealing with the buckling state of the plate subjected to a unique torque. Benchmark results are given in tabular presentations for combinations of free, simply-supported, and clamped types of boundary conditions. It is shown that the critical buckling torque and its associated shape highly depend upon the combination of boundary conditions, radius ratio, and the thickness ratio.
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Abstract

The article presents the methodology to estimate the operator influence on measurements performed with a coordinate measuring arm. The research was based on the R&R analysis, adapted to the specifics of redundant devices such as ACMM (selection of a test object difficult to measure). The method provides for measurements by three operators, who measure ten parts in two or three samples (measurement data developed in the article relate to the three measurements of holes). The methodology is designed to identify which operator has the best predisposition to perform measurements (generates the smallest measurement errors). Statistica software was used to analyse and visualize measurement data.
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Abstract

At the current stage of diagnostics and therapy, it is necessary to perform a geometric evaluation of facial skull bone structures basing upon virtually reconstructed objects or replicated objects with reverse engineering. The objective hereof is an analysis of imaging precision for cranial bone structures basing upon spiral tomography and in relation to the reference model with the use of laser scanning. Evaluated was the precision of skull reconstruction in 3D printing, and it was compared with the real object, topography model and reference model. The performed investigations allowed identifying the CT imaging accuracy for cranial bone structures the development of and 3D models as well as replicating its shape in printed models. The execution of the project permits one to determine the uncertainty of components in the following procedures: CT imaging, development of numerical models and 3D printing of objects, which allows one to determine the complex uncertainty in medical applications.
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Abstract

Automation of earth moving machineries is a widely studied problem. This paper focusses on one of the main challenges in automation of the earth moving industry, estimation of loading torque acting on the machinery. Loading torque acting on the excavation machinery is a very significant aspect in terms of both machine and operator safety. In this study, a disturbance observer-assisted control system for the estimation of loading torque acting on a robotic backhoe during excavation process is presented. The proposed observer does not use any acceleration measurements, rather, is proposed as a function of joint velocity. Numerical simulations are performed to demonstrate the effectiveness of the proposed control scheme in tracking the reaction torques for a given dig cycle. Co-simulation experiments demonstrate robust performance and accurate tracking of the proposed control in both disturbance torque and position tracking. Further, the performance and sensitivity of the proposed control are also analyzed through the help of performance error quantifiers, the root-mean-square (RMS) values of the position and disturbance tracking errors.
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Abstract

The article presents the issue of calibration and verification of an original module, which is a part of the robotic turbojet engines elements processing station. The task of the module is to measure turbojet engine compressor blades geometric parameters. These type of devices are used in the automotive and the machine industry, but here we present their application in the aviation industry. The article presents the idea of the module, operation algorithm and communication structure with elements of a robot station. The module uses Keyence GT2-A32 contact sensors. The presented information has an application nature. Functioning of the module and the developed algorithm has been tested, the obtained results are satisfactory and ensure sufficient process accuracy. Other station elements include a robot with force control, elements connected to grinding such as electrospindles, and security systems.
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Abstract

An optimal sensor placement methodology is implemented and herein proposed for SHM model-assisted design and analysis purposes. The kernel of this approach analysis is a genetic-based algorithm providing the sensor network layout by optimizing the probability of detection (PoD) function while, in this preliminary phase, a classic strain energy approach is adopted as well established damage detection criteria. The layout of the sensor network is assessed with respect to its own capability of detection, parameterized through the PoD. A distributed fiber optic strain sensor is adopted in order to get dense information of the structural strain field. The overall methodology includes an original user-friendly graphical interface (GUI) that reduces the time-to-design costs needs. The proposed methodology is preliminarily validated for isotropic and anisotropic elements.
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Abstract

Centrifugal pumps are used for different applications that include pressure boosting, wastewater, water supply, heating and cooling distribution and other industrial processes. This paper presents theoretical and experimental investigations of mechanical vibrations of a centrifugal pump. The flow in this pump, which induces pressure pulsations and mechanical vibrations, have been monitored. Vibration measurements and data collection (overall vibrations levels and frequency spectrum) were extracted from the system. In addition, one of the methods used to study vibration amplitudes for this pump is forced response analysis. To study and analyze the pump system, the finite element analysis software (ANSYS) was applied. Depending on the analysis performed and investigations outcomes, the system natural frequency coincides with the vane-pass frequency (VPF) hazardously. To attenuate the system’s vibration, a vibration control element was used. The vibration levels were reduced by a factor of 2 for a tuned element as obtained from a forced harmonic response analysis of the pump system with absorber. It is shown that the inserted element allows the centrifugal pump to work in a safe operating range without any interference with its operation.
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