Scientia Iranica
Volume:29 Issue: 5, Sep-Oct 2022

The dynamic performance of straddle monorail train is closely related to the track irregularity. However, there is little research on the track irregularity of straddle monorail , and its semi-random particularity makes it impossible to use the existing track spectrum. In this paper, the irregularity of the running surface of PC beam of monorail is measured, the elevation map is drawn, and the expression of the random irregularity of the track is obtained; the irregularity of finger-band and the deflection of PC beam under dead load are studied; a method is proposed to descript the track irregularity for straddle type monorail, the running surface of straddle monorail is reconstructed, and the correctness is verified by comparing with the test.

Current study proposes a novel mechanism for micro scale droplet generation. To this end, a new micro pump consisting of an expansion chamber with two nozzles at its left and right sides, is introduced which is capable of creating a unidirectional flow. In the current study, for the first time, thermo-Viscose expansion method is used to actuate the flow by assuming that the fluid is heated by using a laser beam source leading to expansion and movement of the fluid. Two-phase flow analysis using the VOF method showed that the proposed micro pump can consistently generate droplets with uniform and micro-scale dimensions.

Loop layout is a common layout in the Flexible Manufacturing Systems (FMS), machines arranged around the loop and materials are transported in unidirectional only. The intention of the loop layout problem (LLP) is the determination of regulating of machines around a loop, to minimize the maximum congestion among the family of parts. Artificial immune system (AIS) algorithm, Tabu Search (TS) and Improved Tabu Search (ITS) algorithms are employed to solve these loop layout problems. The algorithm is tested and validated through large and small-sized randomly generated hypothetical problems with minimum required machine sequence. Further, the efficiency of algorithms is compared with existing algorithm for benchmark problems. Computational results reveal that ITS algorithm outperforms the AIS, TS and existing algorithm for large-sized hypothetical problems.

This paper presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. To describe the entire process, three steps are considered in this study: 1) a coupled hydro-stability analysis which detects the failure plane using the Finite Element Method (FEM) (pre-failure stage), 2) computing the local rheology of the failed mass (wet sandy soil) based on the water saturation at the onset of failure, using the saturation-based rheological model (transition stage), and 3) a continuum-based propagation analysis which solves the flow of the wet material by employing the Smoothed Particle Hydrodynamics (SPH) method (post-failure stage). Finally, to investigate the influence of rheological model on the post-failure behavior, the computed final deposition profile and flow kinetic energy are compared with those of a viscoplastic model.

This work confers the comparative study of Casson-Williamson fluid flow over a heated porous stretchy sheet. The energy and mass transfer equations are modeled by Cattaneo-Christov theory. The governing flow models were altered into an ODE model with the use of suitable transformations. The HAM scheme is applied to find the series solutions. The response of diverse flow variables on fluid speed, fluid warmness, liquid concentration, skin friction coefficient, local Nusselt number, local Sherwood number, local entropy generation number and Bejan number are analyzed through graphs and charts. It is found that the fluid speed subsides when surging values of the magnetic field, porosity, Casson fluid, Williamson fluid and injection/suction parameters. The fluid warmness escalates for a high amount of radiation, convective heating and heat generation/absorption parameters and its suppresses when enriching the convective cooling parameter. The chemical reaction parameter leads to rise in the thickness of the solutal boundary layer. The higher quantity of skin friction coefficient occurs in Casson fluid compared to Williamson fluid. The local entropy generation decimates when growing the Casson and Williamson parameters and it aggravates when raising the Biot number. The Bejan number exalts when upgrading the Reynolds, Brinkman and Biot numbers.

The equalizing wake flow into the propeller behind the ship is important from the hydrodynamic performance viewpoint. In this study, numerical simulations of the DTMB4119 propeller with two symmetric and asymmetric duct types behind the KRISO container ship (KCS) are performed using computational fluid dynamics (CFD). In order to improve the wake equaling flow, a combined duct and stators configurations were installed before the propeller in the stern of the ship and its hydrodynamic performance was studied using CFD. A duct with the NACA4415 section and two types of stator configurations are selected. The STAR-CCM+ software that uses the finite volume discretization method was used to solve the governing equations of the fluid flow. In simulating the turbulence model, the standard k-ω model was used and the solution method was validated by comparing the available experimental data. Output parameters such as thrust coefficient and torque coefficient in the open-water condition and behind the ship have been presented and discussed. Improvements in the propeller performance after mounting the asymmetric and symmetric ducts are found at 4.8% and 6.57%, respectively. So, it is concluded that the symmetric duct is more affected by the propeller performance and, hence, reduced fuel consumption considerably.

The Equal Channel Angular Pressing-Conform process has improved the mechanical and functional properties of materials as well as resolves the disadvantages of conventional ECAP. The main goal of this study was investigation of the variable in ECAP-Conform process of pure titanium Grade 2. The design of experiments with full factorial technique was implemented in conjunction with finite element numerical simulation. The equivalent plastic strain, required torque, applied force on the ECAP die, and the warping radius of the product were measured and results were interpreted using analysis of variance. It was found that the ECAP die angles and the rod bending angle have the highest effect on both imposed strain and required torque. Also, the rod bending angle and the rod-die friction had no significant effect on the warping radius. The optimal values were specified for minimizing the required torque, reaction force, and warping radius, and maximizing the imposed strain. Based on the optimal estimated parameters, the minimum values of torque, force, warping radius, and maximum value of equivalent strain were predicted to 8.4 kN.m, 42 kN, 0.36 m, and 1.7, respectively. Also, the response optimizer obtained the results with less than 8% error in comparison with numerical simulation.

Nowadays, the use of lattice structure designs in metallic parts to produce lightweight systems has gained importance owing to advances in additive manufacturing technology. On the other hand, vehicle manufacturers are constantly looking for new ways to reduce weight due to the depletion of fossil fuels, the demand for vehicles having higher performance, global warming and increasingly stringent emission standards. In this study, in order to reduce the weight of the internal combustion engine, different lattice designs were made in the connecting rods. Four different 2.5D lattice designs, hexagonal, octagonal, square and triangular, were created in reference connecting rod body. The dimension of the lattice designs was 10x10x12 mm with the wall thickness of 1.5 mm. The fatigue behaviors of the connecting rods as well as mechanical properties under static conditions were analyzed using finite element approach. Three different materials were used in the analyzes: AISI 4140, Inconel 718 and Ti6Al4V. As a result, it was seen that weight reduction of up to 15.75% was possible in the connecting rod thanks to the lattice designs and the maximum stresses were below the yield stresses of the materials. Moreover, connecting rods with lattice design had satisfactory safety factor values.