Papers by Keyword: Numerical Analysis

Abstract: The mechanical analysis of sliding frictional contact under small scales is important to improve the understanding about the influence of the contact conditions on the real contact area and, consequently, on the apparent coefficient of friction. This study uses the finite element method to model the contact between an elastoplastic body and a rigid surface with a unidirectional sinusoidal topography, including large sliding. A sensitivity analysis is presented, studying the influence of the initial average pressure, local coefficient of friction and asperity wavelength on the contact conditions. The ratio between total tangential and normal force (apparent friction coefficient) reaches a steady state after a sliding distance of five roughness wavelengths, except for lower values of average initial contact pressure. Increasing the initial average contact pressure leads to an increase of the steady state apparent friction coefficient, particularly for a surface with sharper asperities. This increasing tends to stagnate also with the increase of the local friction coefficient. Withing the cases studied, increasing the initial average contact pressure from 25% to 100% of the material yield stress, leads to an increase of up to 0.07 in the apparent coefficient of friction and of the real-to-apparent contact area ratio up to 30%.

Abstract: A numerical study of an axial fan was conducted, with models compared to catalogue data, key results discussed, and performance improvement suggestions proposed. Research aims to numerically analyze a five-blade axial fan, using topology optimization to maximize flow rate and minimize blade count by comparing fans with varying blades to identify the optimal design. The five-blade axial fan was designed using Creo PTC Software based on standard requirements, and its numerical analysis was conducted using Computational Fluid Dynamics in ANSYS Workbench (2022 R1). The simulation results for the five-blade fan were validated against catalogue data and compared with fans having 1-7 blades. Results, presented through various contour plots and velocity streamlines, showed that the maximum airflow rate (ṁ = 1.432 kg/s) occurred with four blades, the highest-pressure contour (T_total = 474 kPa) with six blades, and the highest total pressure contour (T_total = 170 kPa) at the hub with three blades. The maximum velocity contour (V= 30 m/s) and velocity streamline at the stationary frame (V= 35 m/s) were recorded with five blades. Overall, comparing the four-blade results with the other cases shows that the four-blade configuration delivers superior performance under the same model setup and can be used to enhance future designs.

Abstract: The sustainability and performance of highway infrastructure are vital issues in the current era of rapid urbanization and civilization. The stability of highway embankments needs spatial precaution to maintain good traffic flow and serviceability performance. The lateral sliding and crack formation on the pavement appear due to a lack of confinement against embankments. Conventional retaining structures like gravity walls and reinforced cement concrete retaining walls absorb plastic strains and dissipate in the form of cracks, leading to failure of the structure. Flexibility needs to be introduced in the structure to maintain its strength and shape during the serviceable period. Less explored geocell-retained structures are a good option to maintain flexibility and stress rearrangement in different layers along the structure's height. This research aims to evaluate the structural efficiency and sustainability of the geocell-retained highway embankments as an alternative approach to conventional rigid retaining walls. In the current study, numerical analysis was performed using the Abaqus 2017 version on the geocell retained wall by considering three different shapes (square, hexagonal, and honeycomb) of geocell fiber with aggregates as infill material. Highway cyclic loading (0.5 Hz) and seismic loading (7.5M Kobe earthquake-0.05 Hz) are analyzed respectively. The horizontal stress, displacement, and crest settlement are considered basic parameters to judge geocell efficiency over conventional retaining structures. Shapes like square geocells perform well compared to hexagonal and honeycomb shapes due to more contact area and uniform all-around lateral confinement against instability. This study found that square-shaped geocells provide superior confinement and stability, minimizing crest settlement (1.5 mm under static loading and 0.5 mm under seismic loading) and enabling efficient stress distribution. The findings suggest that geocell-reinforced systems, especially with square cells, offer a much more cost-effective and flexible solution for enhancing the durability and performance of the highway embankments.

Abstract: Computational methods provide effective tools for the prediction of the failure behavior of structures, especially for composites with complex failure modes. The effect of manufacturing process defects on the delamination behavior of composites receives insufficient attention in current studies. In this work, an interlaminar model for composite curved beams considering inter-ply voids was established. A classification and calculation method for calculating inter-ply porosity and intra-ply porosity is proposed based on geometry and location characteristics of voids. Then, an interlaminar model is established based on cohesive zone model with the inter-ply porosity as an input parameter. L-shaped composites with balanced and symmetry layups were cured and subjected to four-point bending tests to validate the proposed method. The numerically predicted location of initial crack generation and final delamination pattern are in great agreement with the experimental results. Besides, the prediction accuracy of the model considering inter-ply voids improves compared with the model without defects, the prediction error of the failure load is reduced from 12.8% to 2.1%. The overall framework provides an accurate and promising tool for the prediction of the delamination behavior and assessing the effects of pore defects of composite curve beams.

Abstract: This paper investigates the thermal performance of a longitudinal trapezoidal fin using the Finite Volume Method, considering temperature-dependent thermal conductivity and heat transfer coefficient. The governing energy equation is developed by incorporating nonlinear thermal parameters and transforming these to dimensionless forms. The domain is discretized into control volumes and the energy balance is applied to each node to develop a system of algebraic equations. The effect of parameters like effectiveness factor, fin steepness, thermal conductivity and scale factor on temperature distribution is then studied. The results provide insights into optimizing fin geometry and thermal properties for efficient heat dissipation in engineering applications, while the temperature gradients along the fin length offers useful information for design. The Finite Volume Method ((FVM) proves advantageous in handling irregular geometries and conserving local balances. Overall, this comprehensive numerical approach enables accurate prediction of the intricate thermal response of longitudinal trapezoidal fins.

Abstract: This paper presents a comprehensive modal analysis of a 15-meter span footbridge constructed using fiber-reinforced polymer structures (FRPs) integrated with natural resource fibers and a partial bio-based resin. The bridge was erected at the Floriade Expo 2022 located in Almere, the Netherlands. The lightweight nature of FRPs, coupled with their sensitivity to vibrations, necessitates the satisfaction of specific design requirements to ensure the safety and comfort of pedestrians. The initial phase of this study entails determining the natural frequencies of the bridge via Finite Element Analysis (FEA). Comparative assessment between the footbridge's natural frequency and excitation frequencies evaluates the risk of resonance induced by pedestrian loading. The FEA employs a composite layup technique to replicate the same ply configuration as the actual bridge model. Following the initial assessment, a comprehensive analysis is undertaken to meticulously examine the dynamic response of the footbridge. This analysis prioritizes the evaluation of critical acceleration parameters under diverse conditions, encompassing scenarios such as walking, jogging, and crowded pedestrian traffic. Bridge peak acceleration is assessed and juxtaposed against design values based on site usage, route redundancy, and structural height, and for the target bridge is 0.77 m/s². The results indicate that the footbridge successfully fulfills the specified design criteria for ensuring pedestrian comfort under various dynamic loading conditions. This finding underscores the significance of including the footbridge in the building application process. This study underscores the successful application of FRPs, augmented with natural fibers and bio-based resin, in ensuring the structural integrity and comfort of footbridges subjected to real-world dynamic conditions.

Abstract: This study proposes a numerical investigation of turbulent flow and heat transfer properties within an air channel featuring a 7-shaped baffle affixed to the lower wall. The main objective of this computational investigation is to assess how the Reynolds number influences the enhancement of heat transfer across a range of Reynolds values from 18000 to 33000. To solve the governing equations, the QUICK numerical scheme and the SIMPLE discretization algorithm are employed. The numerical results are presented through variations in mean velocity and temperature, as well as profiles of local Nusselt number, friction coefficient, Nusselt number and friction factor. These representations facilitate a comprehensive exploration of the aerodynamic and thermal flow properties.

Abstract: In this paper, to confirm the effectiveness and validity of the open-source software Salome–Meca, we constructed and operated Salome–Meca in a design/development environment and performed basic problem solving and eigenvalue analysis, as well as structural analysis. A parametric study was then carried out in collaboration with the open-source software Dakota. Analysis results of Salome–Meca matched both theoretical values and analysis results of ANSYS. Furthermore, the parameter research in Dakota confirmed the eigenvalues and deformation behavior of a pump column pipe as each variable in Salome–Meca was changed; moreover, Salome–Meca and Dakota executed a series of analysis operations normally and automatically. Therefore, Salome–Meca and Dakota are expected to optimize the shape of a structure while avoiding resonance points at natural frequencies.

Abstract: In general, high-precision machines, such as machine tools and measuring equipment, have employed moving tables with hydrostatic bearings. Hydrostatic bearings for these high-precision applications require high bearing stiffness and response speed. Various flow-control restrictors inserted in oil passages were proposed to improve bearing characteristics. However, the active control of conventional flow-control restrictors has some shortcomings because most flow-control restrictors employ voice coil motors (VCMs), which generally consume a large amount of electricity and raise the oil temperature. The increased oil temperature decreases the oil viscosity, which reduces bearing stiffness and damping. Although piezo actuators can solve the above problems and are suitable candidate alternatives to VCMs, their small range of travel has prevented their use in flow-control restrictors. In this paper, a novel flow-control restrictor using a bending beam in stroke expansion is proposed for the purpose of employing piezo actuators. In addition, the bearing characteristics of the hydrostatic bearing with the proposed flow-control restrictor were investigated numerically. In this investigation, the Rayleigh-Ritz method for solving the deformation equations of the bending beam and the divergence formulation method to obtain the pressure distribution in the hydrostatic bearing were adopted in the numerical calculations. The results showed that the hydrostatic thrust bearing with the proposed restrictor has higher stiffness compared with conventional hydrostatic bearings using a capillary restrictor.

Abstract: Transport industry plays a vital role in development of economy of countries. To increase the load carrying capacity of the truck, the weight of truck bed may be reduced using fibre reinforced composite material. In this work, a numerical investigation is performed to reduce the weight of the truck bed using different types of laminated composites. An extensive study is conducted using unidirectional and woven fibres of glass, carbon and Kevlar fibres with polyester, epoxy and vinyl ester resins. Carbon fibre laminated plates have higher stiffness than Glass and Kevlar composite plates. Asymmetrically hybrid composite plates have lower stiffness than symmetrically hybrid composite plates. It is observed that the stiffness of plate is increased when kevlar unidirectional fibres are arranged at top and bottom of the laminate. [K/G_w]_S hybrid composite plates has the lowest deflection than other five hybrid composite plates. An optimization study is performed to identify the influencing parameter for deflection of the composite materials among material type, fibre volumetric fraction and the thickness of plate using Taguchi method. The results revealed that thickness of the plate has more influential than other two parameters.