J.J. del Coz Díaz

The use of design of experiments to improve a neural network model in order to predict the thickness of the chromium layer in a hard chromium plating process

The hard chromium plating process aims at creating a coating of hard and wear-resistant chromium with a thickness of some micrometres directly on the metal part without the insertion of copper or nickel layers. Chromium plating features high levels of hardness and resistance to wear and it is due to these properties that they can be applied in a huge range of sectors. Resistance to corrosion of a hard chromium plate depends on the thickness of its coating, and its adherence and micro-fissures. This micro-fissured structure is what provides the optimal hardness of the layers. The hard chromium plating process is one of the most effective ways of protecting the base material against a hostile environment or improving the surface properties of the base material. However, in the electroplating industry, electroplaters are faced with many problems and undesirable results with chromium plated materials. Common problems faced in the electroplating industry include matt deposition, milky white chromium deposition, rough or sandy chromium deposition and insufficient thickness and hardness. This article presents an artificial neural network (ANN) model to predict the thickness of the layer in a hard chromium plating process. The optimization of the ANN was performed by means of the design of experiments theory (DOE). In the present work the purpose of using DOE is twofold: to define the optimal experiments which maximize the ratio of the model accuracy, and to minimize the number of necessary experiments (ANN models trained and validated).

Design and finite element analysis of a wet cycle cement rotary kiln

The finite element method (FEM) is applied to the nonlinear analysis of a cement rotary kiln for the Rais Hamidou factory (Algeria). The nonlinearity is due to contact conditions between the kiln body, tyres and foundations. The FEM is first used in a reduced model of the kiln in order to obtain the meshing criterion for the global model. Then, an overall FEM analysis is performed for the different operating and live loads at different positions of the rotary kiln. Stress and displacement components are evaluated based on the ASME rules (Asme Boiler and Pressure Vessel Code. VIII. Division 2--Alternative Rules. The American Society of Mechanical Engineers, 1995). Finally, in this work, the main design criterion is the out-of-roundness values at the kiln shell so that the thickness of the kiln shell is smaller in the central bend span than the values at the tyres.

Non-linear buckling analysis of a self-weighted metallic roof by FEM

This paper aims to describe the development of a numerical model to accurately simulate the non linear buckling of self-weighted metallic roofs by the finite element method (FEM), which has different span lengths, ranging from 22 to 30 m, and the same cross section. In this way, the collapse buckling load was calculated in two steps: firstly a linear buckling was carried out and secondly, an initial imperfection was added to the geometrical model and the non-linear analysis was performed. Finally the results and conclusions reached in this work are shown.

Evaluation of the damage in the vault and portico of the pre-Romanesque chapel of San Salvador de Valdediós using frictional contacts and the finite-element method

Monuments are by definition unique buildings which cannot be reduced to any standard structural scheme. In this study, we have used quasi-static loads, which is common practice in many finite-element (FEM) analyses of masonry structures. Thus it is difficult to evaluate their reliability, because in addition to the many uncertainties that exist in all ‘old’ buildings, no statistics on the behaviour of similar buildings are available. In this paper we describe a study of the structure of the chapel of San Salvador de Valdediós and proposals for its restoration. The non-linear analysis is based on the application of FEM to each of the stone blocks in this ancient structure. The blocks are assembled side by side using ‘contact elements’ in order to reproduce the mechanical behaviour of the mortar and the surface conditions of the blocks, some of which are seriously damaged. A clear understanding of the structural behaviour, based on sophisticated analysis tools, can reduce the extent of the remedial measures necessary for the restoration of the chapel vault and portico. In this case, severe damage to the chapel vault has affected the portico, resulting in the possibility of a structural collapse. Finally, based on the numerical results obtained for different load cases and hypotheses, we propose a solution for the repair of this part of the chapel using either traditional materials or compatible substitutes.

Non-linear thermal analysis of the efficiency of light concrete multi-holed bricks with large recesses by FEM

Abstract This paper shows how advanced numerical methods can help to improve the thermal efficiency of walls made up of multi-holed bricks with large recesses. In order to get this objective, a new methodology based on different numerical simulations is presented here. With the help of the finite element analysis (FEA), we present an optimization procedure in order to determine the best candidate brick with large recesses from the thermal point of view. With respect to the ecological design and the energy saving for housing and industrial structures, there is also a great interest in light building materials with good physical and thermal behaviours, which fulfils all thermal requirements of the new CTE Spanish rule for further energy savings. On one hand, we want to validate the numerical analysis procedure, based on the simulation of three-dimensional walls by the finite element method (FEM). On the other hand, we have analyzed the material conductivity for different compositions of the light concrete. The FEM technique is used for finding accurate solutions of the heat transfer equation in walls made up of light concrete multi-holed bricks with large recesses. Mathematically, the non-linearity is due to the radiation boundary condition inside the inner recesses of the bricks. Next, the thermal optimization of the walls is carried out from the FEM technique of several hollow brick geometries using the average mass overall thermal efficiency and the equivalent thermal conductivity. In order to select the appropriate wall satisfying the CTE requirements, detailed instructions are obtained and indicated to the readers. Finally, conclusions of this paper are exposed.

Comparative Analysis of Mechanical Tensile Tests and the Explicit Simulation of a Brake Energy Dissipater by FEM

The use of brakes or energy dissipaters in the anchorages of rockfall barriers is based on their great slip resistance capacity. The brake energy dissipaters can dissipate the kinetic energy produced by the impact of rocks, which is transmitted to them through the system made up of a network of wires, poles, guided cables and anchorages. The dissipaters transform kinetic energy into heat through their deformation (strain), thus increasing the dynamic performance of the screens against falling rocks. These dissipating elements consist of two tubular steel loops (bearing ropes, ties) joined by two aluminium compression sleeves at its extremities, which are under pressure depending on the slip resistance that is desired. In this work a comparative analysis of results obtained from two tensile tests is carried out simulating the slip of the brake energy dissipaters when they are working. The first tests were carried out with a static tensile load. These tests were conducted on a bench with a hydraulic jack varying the tightening pressure on the dissipaters compression sleeves. The second test was the nonlinear dynamic simulation of symmetrical tensile tests and fixed point of the brake energy dissipater. This simulation was performed using the explicit finite element method (FEM), varying the coefficients of friction and speed of slippage between the bearing ropes. The numerical results of these studies show the correlation between the dissipation energy in the tensile tests and the fixed point between the two experiments. In addition, some complementary improvements with respect to the location and geometry of the design of these brake energy dissipaters are made by correcting the efficiency of brake energy dissipater and anchorage set of the rockfall barriers.

Non-linear analysis of cable networks by FEM and experimental validation

This work studies the analysis of the resistant capacity of cable nets for the stabilization of slopes. Two tests have been carried out, one with a distributed longitudinal load and the other with distributed transversal load, in order to simulate in situ the working conditions of these systems. Tensile tests were also carried out on the cable elements of the network in order to obtain the non-linear mechanical properties. On the one hand, the proposed numerical procedure uses the finite element method (FEM) and it takes into account the material and geometrical non-linearities due to the geometrical change in the cable net substructure. On the other hand, the contour (boundary) beam is modelled by linear beam elements with contact between them. The numerical results of the longitudinal and cross tests were simulated for different geometrical configurations, generating convergent results with respect to strain and resistance, which permit the extrapolation from tested cable nets to untested simulated cable nets, maintaining a basic configuration of constant parameters. The laboratory tests only provide information about the strain and maximum resistance, but they do not establish a relationship between the values of stresses of each net element. These data have been obtained through the computational simulation by FEM. A reliable model of the interaction of the flexible contour beam with the cable network enables the achievement of more efficient solutions in the design analysis. Finally, we compare the structural behaviour of the numerical and experimental results by means of the equivalent elastic modulus and the equivalent Poisson ratio. Excellent agreement between the predicted results by FEM and test observations was found. Besides, conclusions and suggested procedures of calculation applied on the cable networks are given and numerical models to evaluate the stability of the slope protection systems are presented.

Improvement of a System for Catchment, Pretreatment, and Treatment of Runoff Water Using PIV Tests and Numerical Simulation

AbstractThis paper studies how to improve the efficiency of a new system for catchment, pretreatment, and treatment of runoff water (SCPT). This system is integrated into an urban sustainable gravity settler that can decrease diffusive pollution. This study provides important advantages for the ecosystem by improving new sustainable drainage to clean runoff water. In this paper, an investigation methodology known as hybrid engineering (HE) was used. HE combines experimental tests and numerical simulations, both of them conducted on a 1:4-scale prototype. In this study, numerical simulations by the finite-volume method (FVM) and experimental tests by particle image velocimetry (PIV) were compared. A strong correlation between the numerical and experimental analysis was found. Next, the efficiency of the SCPT was optimized by design of experiments (DOE). Analysis of experimental and numerical results and their comparison are presented in this paper.

Effects of elevated temperatures on mechanical properties of concrete containing haematite evaluated using fuzzy logic model

Abstract Concretes containing different proportions of haematite (15, 30, 45 and 60%) were fabricated and subjected to elevated temperatures (25, 200, 400, 600 and 800°C). The cement content and water/cement ratio were 450 kg m−3 and 0·38 respectively. The compressive strength and elasticity modulus of concretes were determined according to ASTM C39 and ASTM C469. A rule based Mamdani type fuzzy logic model for predicting the compressive strengths and elasticity modules of concretes containing haematite has been developed. The inputs were haematite content (%), exposure time (h) and temperature T (°C); the outputs were compressive strength and compressive elasticity modulus. It is shown that all the results of the model for elasticity modulus and compressive strength were in good correlation with the experimental results for all data sets.

Steady state numerical simulation of the particle collection efficiency of a new urban sustainable gravity settler using design of experiments by FVM

Abstract The aim of this work is to analyze the efficiency of a new sustainable urban gravity settler to avoid the solid particle transport, to improve the water waste quality and to prevent pollution problems due to rain water harvesting in areas with no drainage pavement. In order to get this objective, it is necessary to solve particle transport equations along with the turbulent fluid flow equations since there are two phases: solid phase (sand particles) and fluid phase (water). In the first place, the turbulent flow is modelled by solving the Reynolds-averaged Navier–Stokes (RANS) equations for incompressible viscous flows through the finite volume method (FVM) and then, once the flow velocity field has been determined, representative particles are tracked using the Lagrangian approach. Within the particle transport models, a particle transport model termed as Lagrangian particle tracking model is used, where particulates are tracked through the flow in a Lagrangian way. The full particulate phase is modelled by just a sample of about 2,000 individual particles. The tracking is carried out by forming a set of ordinary differential equations in time for each particle, consisting of equations for position and velocity. These equations are then integrated using a simple integration method to calculate the behaviour of the particles as they traverse the flow domain. The entire FVM model is built and the design of experiments (DOE) method was used to limit the number of simulations required, saving on the computational time significantly needed to arrive at the optimum configuration of the settler. Finally, conclusions of this work are exposed.