Journal of Computational Applied Mechanics
Volume:52 Issue: 2, Jun 2021

Composite slabs with steel deck have been used on building construction due to its fast-and-easy crafting that brings economic outstanding alternatives to architects and engineers on large-scale steel framed constructions. At room temperatures and in Europe, the designing procedures of composite slabs are defined by Eurocode 1994-1-1. When it comes to the fire safety analysis of these elements, the designing procedure requires more attention due to the direct exposition of the steel deck to fire, affecting the overall bending resistance. This importance is presented in Eurocode 1994-1-2, taking in consideration the integrity, insulation and load-bearing criteria. In this work the thermal and mechanical behaviour of composite slabs with steel deck exposed to standard fire ISO 834 are studied through numerical simulations using Finite-Element Method (FEM). The model was previously validated with one experimental test from literature. The ANSYS Mechanical APDL software was used to develop a parametric study, simulating four different geometries with different load levels, comprehending a total of 126 thermal and mechanical simulations used to determine the correlation between load-level and fire resistance. As result, a new simplified method is proposed for the load bearing fire resistance of composite slabs, considering the effect of the effective thickness and the load level. The fire resistance decreases with the load level and increases with the thickness of the concrete. A new proposal is presented to determine the fire resistance, based on these two parameters.

Composite steel-concrete slabs are structural elements composed of a profiled steel deck which acts as a permanent formwork to the concrete topping. This layer is commonly reinforced with individual rebars and an anti-crack mesh. The Annex D of the EN 1994-1-2 provides guidelines for the calculation of the temperature of the steel components of composite slabs subjected to the standard fire. However, no revisions were made to these calculation rules during the last years. This paper proposes a new method for the estimation of the temperature of the parts of the steel deck and the rebars as well. The proposed methodology is derived from numerical analyses using a 3-D finite element model, considering perfect thermal contact between the materials.

The spillways of hydraulic structures transfer excessive water from dam reservoir to the downstream in a safe and controlled manner. A labyrinth or triangular weir is a flat spillway folded in plain view. The labyrinth weirs provide an increase in crest length for a given channel width and increase the flow capacity for a given weir load. As a result of the increased flow capacity, the labyrinth and triangular weirs require less space in the dam body than the flat weirs. In this study, experiments were carried out on the labyrinth weirs containing triangles of different heights and numbers by using 3 different weir heights (P=20cm, 30cm, and 40 cm) and 4 different weir shapes. Each experiment was repeated for 30 different discharge values. The effects of weir height and weir shape on the total head over the weir (HT) and discharge (Q) were investigated. In addition, the numerical models of all experimental setups were created by ANSYS-Fluent program using Computational Fluid Dynamics (CFD). By comparing the results obtained from the numerical models with the physical models, the accuracy of the numerical models was tested. According to the results, as the number of the triangles (N) of the weir increases, the discharge coefficient (Cd) decreases. The weir height (P) does not have a major effect on the discharge.

In this article, a reliable model for the vibration of cross-ply and angle-ply laminated plates that own inhomogeneous elastic properties is considered. The methodology includes a theoretical study of free vibration behavior of composite plates with the inhomogeneous fibrous distribution of the volume fraction using a sinusoidal model by the use of the advanced refined theory of shear deformation of nth-higher-order. The micromechanical typical is proposed to represent the elastic and physical properties of the inhomogeneous laminated composite plate. The effects of inhomogeneity, lamination schemes, aspect ratio, and the number and order of layers on dimensionless vibration frequencies are investigated.

Well conditions during drilling operation can be predicted using numerical simulation. During under-balanced drilling (UBD) operation, controlling the bottom-hole pressure (BHP) in a suitable range and also appropriate hole-cleaning is essential. In this paper, numerical simulation of gas-liquid-solid three-phase flow in the annulus is used to study the effects of annulus geometry and also liquid properties on the BHP and hole-cleaning during UBD operation. To validate the numerical simulation, the results are compared with the experimental data from a laboratory study. Also, the gain results from developed code are compared with the actual field data from a real well, several mechanistic models from WellFlo software, and gas- liquid two- fluid numerical simulation. Due to the significance of controlling the BHP and hole-cleaning during UBD operation, the effects of annulus geometry and liquid phase properties on BHP and the solid volume fraction distribution are investigated. According to the results, changing the hydraulic diameter and cross-sectional area of the annulus can affect BHP and hole- cleaning in UBD operation. In other words, increasing the hydraulic diameter at a constant cross- sectional area improves hole-cleaning and decrease BHP. Also, decreasing the cross-sectional area at a constant hydraulic diameter improves hole-cleaning and increase BHP. The results show that the liquid viscosity affects hole-cleaning through two contrary mechanisms. In fact, by increasing the liquid viscosity, carrying capacity of the liquid phase is increased and cutting transfer velocity is decreased.

This paper aims to discuss the vibration analysis of the post-buckled cracked axially functionally graded (AFG) beam. The nonlinear equations of motion of the Euler-Bernoulli beam are derived using the equilibrium principles. Then, these differential equations are converted into a set of algebraic ones using the differential quadrature (DQ) method and solved by an arc-length strategy. The resulted displacement field from the post-buckling analysis is assumed to be the equilibrium state of vibration analysis, and an eigenvalue problem is derived. By solving this linear eigenvalue problem, both the natural frequencies and mode shapes of the beam are calculated. The validation of results in comparison with a similar work shows a good agreement. The effect of several parameters such as the extensible and inextensible clamped-clamped boundary conditions, initial geometric imperfection, crack’s depth, and crack’s location on the natural frequencies and mode shapes are investigated in detail.

One of the most important characteristics of a modern product is the extent to which it meets the needs of customers to gain market share. The conceptual design methods of products based on customer requirements are often feature-based, in which several features are identified between different types of a product. According to customer demands, these features are tuned and the closest is selected as the optimum. The great variety of features of a present-day product can often make this difficult because finding these common features is very complicated or even impossible. To solve this problem, choosing the optimal design is divided into two phases: In the first phase, the main product is divided into some basic categories and according to the customers' opinion, one is selected as the "winning category". In the second phase, the selection of common geometrical features between the members of the winning category is made. Then, the optimization process is done based on customer rating and the closest design to the mentioned rating is selected. The house light switch is used as a case study and the proposed algorithm is implemented on it. High customer satisfaction with the optimized final design, high response rate to survey forms, and the low number of incompatible data, all, indicate the suitability of the proposed algorithm with human interface characteristics, simplicity and efficiency in adapting the product to the customers' view. This method can be used for other industrial products and even for non-industrial products or services.

The cutting tool and work-piece of cutting process are commonly analyzed using Finite Element (FE) and Smooth-Particle Hydrodynamics (SPH) methods respectively. This is identified a compound method in this research. The interaction between cutting tool elements and work-piece particles are modeled as pressure and friction force. The coefficient of friction (CF) between cutting tool and work-piece is the fundamental parameter of friction model. The CF effects on chip morphology and cutting force. In present study, both cutting tool and work-piece of cutting process are analyzed using SPH method without Friction and pressure model (SPH.NO.F). Therefore the pressure and friction force between elements and particles in compound method are replaced with the interaction between particles. The friction in the cutting zones is a physical process that accompanies the cutting but this is not modeled in analyzing of this process, because the cutting tool and work-piece particles interact with each other using the mass and momentum conservation equation. The results of orthogonal cutting process show the chip morphology of SPH.NO.F method is the same as compound method with friction model by CF=0 and 0.17. The cutting force of SPH.NO.F method is coincided to experimental results. The cutting force of milling process is investigated using SPH.NO.F and compound method by CF=0 and 0.17.

This study investigates the effect of size scale material parameters on stress distribution and radial displacement of nanosphere based on strain gradient theory. This model is more capable of studying mechanical behavior than classical elasticity theory as the size scale effect of the nanosphere is also considered. Minimum total potential energy is used to derive governing differential equation of nanosphere under internal hydrostatic pressure. Using the efficient numerical generalized differential quadrature (GDQ) method, the governing equation and corresponding boundary conditions are solved. The classical elasticity equation is obtained by setting the value of size scale material parameters to zero. With the comparison of these theories, the importance of the size scale material parameters is achieved. It is found that the radial displacement of nanosphere predicted by strain gradient theory is less than those predicted by classical elasticity theory but comparing the distribution of stress components along radius is more complex. The effect of the size of the nanosphere on the radial stress components is also studied. With an increasing outer radius of the nanosphere, the mechanical behavior predicted by strain gradient theory tends toward those in classical elasticity theory.

The purpose of this paper is to analyze the effects of structural and mechanical characteristics of metal foam on the melting behavior of phase change materials under the influence of different heat fluxes. To this aim, a two dimensional numerical model considering the non-equilibrium thermal factor, non-Darcy effect and local natural convection was used. The governing equations of PCM and metal foam are discretized using a finite volume method with a collocated grid arrangement. To simulate the melting of PCM, the enthalpy-porosity method is applied which computes the liquid fraction at each iteration, based on the enthalpy balance. The effect of metal foam characteristics (porosity, pores size and base material) and wall heat flux on the PCM melting time were investigated. The result showed that for both wall heat fluxes (4000 W m-2 and 8000 W m-2), foam structure and its mechanical properties have significant influence on the PCM melting time which these effects should be considered.

In this study, two-phase flow over a three-dimensional stepped spillway was numerically investigated using a finite volume code in ansys-Fluent commercial software. The numerical results were validated against experimental data. Then, the effects of several parameters were evaluated on the structure of the flow over the concerned spillway. Based on the natural roughness, several roughness heights of 0.0001, 0.0005, and 0.001 m were considered on the spillway surface to investigate the flow structure. In the next step, several surfaces with different contact angles, including 80, 120, and 160°, were used. Finally, a passive control method, including simultaneous blowing and suction with different configurations, was applied to the steps of the spillway. The results revealed that a change in the surface roughness or contact angle and applying the control method could change the flow regime from skipping to nappe. Also, variations in the speed of falling water and energy loss were attributed to changes in the surface roughness and contact angle and implementation of the proposed control method.

As a result of reduction trend in exploration of super-giant carbonate fields and depletion of the proven mature fields categorized as easy oil, development of tight, deep carbonates with more complexities in reservoir rock and fluid behavior have become of interest for exploration and development companies in recent years. New challenges have arisen in development of complex carbonates due to fracture network distribution uncertainty, lateral and vertical fluid behavior heterogeneities, unstable asphaltene content, high H2S and CO2 contents and high salinity formation brine. The complexity elements and problems for downhole sampling have made the full understanding of the reservoir behavior and consequently availability of data for further routine analysis and utilization of simulation model as the main way of data integration limited. Therefore, there is an emerging need to better understand the challenges surrounding production and enhanced oil recovery strategies in these reservoirs for an improved oil recovery decision making system. In this paper, the challenges in production, stimulation and enhanced oil recovery strategies in newly-developed complex carbonates are addressed and analyzed based on the changes to the chemical and mechanical environment. An integrated decision-making workflow based on coupled hydro-mechanical mechanisms in water-based EOR methods is discussed.