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In this paper, simulation and analysis of thin steel cylindrical shells of various lengths and diameters and thickness with triangular cutouts have been studied. In this research buckling and post-buckling analyses were carried out using the finite element method by ABAQUS software. Moreover, the effect of cutout position and the length-to-diameter (L/D) and diameter-to-thickness (D/t) ratios on the buckling and post-buckling behavior of cylindrical shells have been investigated. In this work the cylindrical shells used for this study were made of mild steel and their mechanical properties were determined using servo hydraulic machine. Then buckling tests were performed using a servo hydraulic machine. In order to numerical analyze the buckling subject to axial load similar to what was done in the experiments; a displacement was applied to the center of the upper of the specimens. The results of experimental tests were compared to the results of the finite element method. A very good correlation was observed between numerical simulation and experimental result.

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In this paper, the effect of gas and liquid inlet superficial velocities and distance from upstream on slug frequency is studied experimentally. Empirical correlations are also presented based on the obtained results. The tests are conducted for liquid holdup αl= 0.75 and three distances from inlet in a long horizontal channel made of Plexiglas with dimensions of 510 cm2 and 36m length in Multiphase Flow Lab. of Tarbiat Modares University. The superficial liquid and air velocities rated as to 0.11-0.56 m/s and 1.88-13 m/s, respectively. The obtained results show that slug frequency is dependent to superficial liquid velocity directly. Slug frequency decreases with slip ratio increase. Slug frequency has strong dependency on superficial liquid velocity and increases monotonically with it. However, superficial gas velocity has damping effect on slug frequency. As slug moves towards downstream, slug frequency will be decreased but slug velocity will be increased.

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It is essential to inspect manufactured and in-service machines and components in industry. Many different are currently in use for this purpose. Ultrasonic testing is one of the most important nondestructive testing methods. Ultrasonic testing has different applications such as defect detection, assessment of mechanical and metallurgical properties of materials and temperature measurement. In the first part of this paper, theoretical equations and finite element analysis of variation of longitudinal ultrasonic wave velocity in the presence of a thermal gradient were studied. In the second part, the effect of a thermal gradient on the longitudinal ultrasonic waves is investigated by experiments. A specific test rig is designed and fabricated for this purpose. It can provide the desired temperatures and transmit and receive ultrasonic bulk waves simultaneously. Twelve different tests were carried out to study the effects of the work piece length and maximum and minimum temperatures. The experimental results are compared with the theory under similar conditions and very good agreement is observed. Uncertainty analysis is incorporated for determining the uncertainty in measuring the ultrasonic wave velocity in the presence of a thermal gradient and identifying the sources of error. The measurements were found to be quite accurate with an uncertainty of 4.5 m/s.

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In this paper, the nonlinear electromechanical formulations of a piezoelectric energy harvester are proposed to investigate the effect of exponential tapering on generating more power with less mass from energy harvester. For this purpose, geometric, inertial, material and damping nonlinearities are included. The governing equations are derived using the Euler-Bernoulli and linear variation of electric voltage along the thickness assumptions. The coupled nonlinear equations are discretized by the mass normalized mode shapes of an exponentially tapered piezoelectric beam with tip mass, and resulting differential equations are solved employing the method of multiple scales. An experiment is set up, and the damping coefficient of the beam is calculated from the tip acceleration to base acceleration frequency response function in the case of low exciting acceleration and short circuit. Material nonlinear coefficients are identified using the experiment, when the exciting acceleration of the shaker is increased, and the proposed solution accuracy is verified. The effect of tapering exponentially on the behavior of the piezoelectric energy harvester is investigated by studying length, tapering parameter and exciting acceleration amplitude in some examples.

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The purpose of this study is to generate two-phase flow patterns and to obtain a flow pattern map for two phases as water and air in a vertical pipe which is made of transparent Plexiglas. The pipe specification is 50 mm diameter and 390 cm length. In this attempt the average velocity of the Taylor bubble will be calculate. In order to facilitate this research work, a two phase flow was designed, built and adjusted at Tarbiat Modares University Two-phase flow laboratory. Three flow patterns as bubbly, slug and churn flow are generated and examined for 320 runs of different superficial velocities of air and water. A seven-layer distributor with the ability to change the number of bubbles produced is used to create a bubbly flow pattern at the air inlet. The effect of the superficial velocities of each phase on the flow pattern was evaluated and a flow pattern map was presented for 320 different data. By processing the images obtained from the high-speed camera, the average Taylor bubble velocity was calculated for different flow conditions with uncertainty in calculating the velocity. Also, for 5 different velocities of the liquid phase, a diagram of the average velocity of Taylor velocity with increasing gas velocity was drawn and compared with the Nicklin correlation which can be found in the literature

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This study introduces a novel lattice structure, whose unit cell design draws inspiration from the fusion of honeycomb patterns and the DNA found at the core of cells, constructed from PLA material. This structure underwent tensile testing along the X and Y axes. Additionally, the paper presents a new analytical-numerical approach that combines Timoshenko beam theory, mechanics of materials principles, and finite element analysis to determine the mechanical properties and forecast failure in cellular structures. This method was corroborated using the ABAQUS commercial software. Research indicated that a closer ratio of thickness to unit cell length, specifically 1/10, leads to more precise predictions for the mechanical behavior of the cellular structure under tension along the X axis. The findings showed that, in comparison to the Y axis, the X direction exhibited a 7% increase in load-bearing capacity and an 8% increase in maximum yield stress, yet the equivalent stiffness was 75% lower