DIMM-Artículos

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The sustainable manufacturing concept, evolution and opportunities within Industry 4.0: A literature review
(SAGE, 2014-05) Sartal, Antonio; Bellas, Roberto; García-Collado, Alberto; Mejías, Ana
Today’s society is becoming aware that a new economic model of production and consumption must take into account its environmental and social impact. Industries are under increasing pressure from stakeholders to be transparent in reporting the environmental and social impacts of their operations. In this context, sustainable manufacturing must minimize negative environmental impacts and consumption of energy and natural resources, while also being socially responsible and economically viable. That is why the sustainable manufacturing concept is gaining increasing attention both in the research community and in organizations, especially in the industrial sector. However, even today, there is a great diversity of interpretations and ideas associated with this term. Accordingly, this article first presents an overview of the main concepts related to sustainable manufacturing, and metrics to evaluate organizations’ sustainability performance, and then an outlook of current trends. Our work highlights the consistencies and inconsistencies in the research community related to the interpretations of sustainable manufacturing and Industry 4.0, as well as the lack of consensus about the true social impact of Industry 4.0. However, the positive ecological and economic impacts of sustainable manufacturing seem fairly widespread. In this way, sustainable manufacturing practices seem to be reinforced by initiatives within the fourth stage of industrialization – the so-called Industry 4.0 – which offers great opportunities for sustainable manufacturing, thanks to digital transformation.
Development of Vertical Wind Turbines via FDM Prototypes
(ELSEVIER, 2015-12-25) Guerrero-Villar, Francisca; Torres-Jiménez, Eloísa; Dorado-Vicente, Rubén; Jiménez-González, Jose Ignacio
In the present work, we propose to design and manufacture a specific Vertical Axis Wind Turbine (VAWT) prototype in order to evaluate its performance when some geometrical parameters are modified. The key idea is to take advantage of additive manufacturing flexibility to print the main components in an easy way and at low cost. Prototype size (scale 1:250, with respect to a 2 MW wind turbine) is small enough to be tested in a 40 cm x 40 cm wind tunnel. We use a Fused Deposition Modeling (FDM) machine to print the prototype, which is previously designed via CAD software. Different tests have been performed to determine an adequate printing configuration, mainly regarding how layer height influences roughness and printing time. Main dimensions, roughness and weight of the printed pieces were measured and finally, parts of highest quality were used to assemble a working prototype. The methodology presented in this paper shows it is possible to manufacture a wind turbine prototype with the following characteristics: flexibility to modify the design throughout the course of the investigation, low cost and low time needed to obtain the components with enough quality.
Fracture of eutectoid steel bars under tensile loading: Experimental results and numerical simulation Author links open overlay panel
(Elsevier, 2016-06) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime Carlos; Cendón, David Ángel; Atienza, José Miguel
Construction steel bars tested under tension usually show a cup-cone fracture pattern. Nevertheless, some steels, such as the eutectoid one used for manufacturing prestressing steel wires, show a different pattern: a flat fracture surface with a dark region inside. This paper presents experimental work performed to identify the fracture mechanisms that trigger this particular flat fracture pattern and numerical simulations where it is reproduced numerically. The experimental tests are carried out on cylindrical specimens of three diameters, 3, 6 and 9 mm, subjected to tension. In order to analyse the fracture mechanism, numerical simulations are performed by using the finite element method and the cohesive zone approach. To that end, a cohesive interface element with mechanical properties that depend on the stress triaxiality is presented and assessed. This approach provides reasonably good agreement with the experimental results. In addition, when compared with other popular models such as the GTN model, it presents certain advantages since it requires a smaller number of parameters to be defined.
Study of the last part of the stress-deformation curve of construction steels with distinct fracture patterns
(Elsevier, 2016-10) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime Carlos; Cendón, David Ángel; Atienza, José Miguel
The principal mechanical characteristics of construction steels are obtained by tensile testing. Nevertheless, the standards neglect the behaviour of steel beyond the maximum load point and do not define parameters related to the part of the stress-deformation curve that lies between the maximum load point and failure. The necking process that begins when the maximum load is reached makes it somewhat difficult to study the material behaviour beyond that point. However, the ductility of steel is highly affected by this last part of the load-deformation curve. For such a reason, and especially since structural safety is directly related to ductility, a deeper knowledge of this may help in designing safer structures. In this paper, this part of the load-deformation curve is analysed in two construction steels that exhibit distinct fracture patterns: one shows the typical cup-cone fracture surface, while the other shows a flat fracture surface with a dark region inside. An experimental campaign has been carried out with cylindrical specimens of contrasting diameters: 3 mm, 6 mm and 9 mm for each material. The use of a digital image correlation system is shown to be extremely useful in studying the behaviour of steel beyond the maximum load point, with an innovative procedure for identifying the growth of the internal damage that leads to failure in a specimen being developed.
Controlled formation of bubbles in a planar co-flow configuration
(Elsevier, 2017-03-01) Ruiz-Rus, Javier; Bolaños-Jiménez, Rocío; Gutiérrez-Montes, Cándido; Sevilla-Santiago, Alejandro; Martínez-Bazán, Carlos
We present a new method that allows to control the bubble size and formation frequency in a planar air-water co-flow configuration by modulating the Water velocity at the nozzle exit. The forcing process has been experimentally characterized determining the amplitude of the water velocity fluctuations from measurements of the pressure variations in the water stream. The effect of the forcing on the bubbling process has been described by analyzing the pressute signals in the air stream in combinatiOn with visualizations performed with a high-speed camera. We show that, when the forcing amplitude is sufficiently large, the bubbles can be generated at a rate different from the natural bubbling frequency, f(n), which depends on the water-to-air velocity ratio, Lambda u(n)/u(q), and the Weber number, We rho(w)u(n)(2)H(0)/sigma, where H(0) is the half-thickness of the air stream at the exit slit, rho(w), the water density and a the surface tension coefficient. Consequently, when the forcing is effective, monodisperse bubbles, of sizes smaller than those generated without stimulation, are produced at the prescribed frequency, f(f) > f(n). The effect of the forcing process on the bubble size is also characterized by measuring the resulting intact length, l, i.e. the length of the air stem that remains attached to the injector when a bubble is released. In addition, the physics behind the forcing procedure is explained as a purely kinematic mechanism that is added to the effect of the pressure evolution inside the air stream that would take place in the unforced case. Finally, the downstream position of the maximum perturbation amplitude has been determined by a one-dimensional model, exhibiting a good agreement with both experiments and numerical simulations performed with OpenFOAM.
Distinct Fracture Patterns in Construction Steels for Reinforced Concrete under Quasistatic Loading— A Review
(MDPI, 2018-03) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime Carlos; Cendón, David Ángel; Atienza, José Miguel
Steel is one of the most widely used materials in construction. Nucleation growth and coalescence theory is usually employed to explain the fracture process in ductile materials, such as many metals. The typical cup–cone fracture pattern has been extensively studied in the past, giving rise to numerical models able to reproduce this pattern. Nevertheless, some steels, such as the eutectoid steel used for manufacturing prestressing wires, does not show this specific shape but a flat surface with a dark region in the centre of the fracture area. Recent studies have deepened the knowledge on these distinct fracture patterns, shedding light on some aspects that help to understand how damage begins and propagates in each case. The numerical modelling of both fracture patterns have also been discussed and reproduced with different approaches. This work reviews the main recent advances in the knowledge on this subject, particularly focusing on the experimental work carried out by the authors.
On the localisation of damage under pure bending using a nonlocal approach
(Elsevier, 2018-06) Suárez Guerra, Fernando
To reproduce the behaviour of quasibrittle materials mathematically, constitutive laws with softening are needed, which often leads to development of damage localisation bands. If a standard local formulation is used, this approach leads to a pathological mesh dependence, which can be eliminated by making use of alternative nonlocal formulations. The aim of this paper is to assess the localisation properties of damage models under pure bending using different nonlocal formulations; to permit a partially analytical treatment, the idealised case of pure bending is studied. Under these conditions, the localisation process starts at the tensile face of the beam, which belongs to the boundary of the domain on which the problem is solved. Consequently, localisation patterns are affected by the boundary treatment as well as other parameters, such as the characteristic length that defines the area contributing to the nonlocal averaging. This paper presents an analytical study of the onset of localisation of different nonlocal formulations for a beam under pure bending. In addition to it, the subsequent evolution of the localised solution is explored by numerical simulations, analysing the localisation bands spacing, the dissipated energy profile along the fracture plane and the Moment-curvature diagrams, with curvature being a parameter that represents the rotation that drives the loading process (ϕ stands for the relative rotation angle of the cross section and L for the beam length). An analysis of damage localisation on longer beams where damage localises in several areas is also carried out and, finally, the damage localisation due to shrinkage is studied as a more realistic example of the problem addressed here.
Macro Photography as an Alternative to the Stereoscopic Microscope in the Standard Test Method for Microscopical Characterisation of the Air-Void System in Hardened Concrete: Equipment and Methodology
(MDPI, 2018-08) Suárez Guerra, Fernando; Conchillo, José J.; Gálvez, Jaime C.; Casati, María J.
The determination of the parameters that characterize the air-void system in hardened concrete elements becomes crucial for structures under freezing and thawing cycles. The ASTM C457 standard describes some procedures to accomplish this task, but they are not easy to apply, require specialised equipment, such as a stereoscopic microscope, and result in highly tedious tasks to be performed. This paper describes an alternative procedure to the modified point-count method that is described in the Standard that makes use of macro photography. This alternative procedure uses macro-photographic images that can be obtained with a quite standard photo camera and it is successfully applied to a large set of samples and presents some advantages over the traditional method, since the required equipment is less expensive and provides a more comfortable and less tedious procedure for the operator.
Surface Quality Enhancement of Fused Deposition Modeling (FDM) Printed Samples Based on the Selection of Critical Printing Parameters
(MDPI, 2018-08) Pérez, Mercedes; Medina-Sanchez, Gustavo; García-Collado, Alberto J.; Kumar Gupta, Munish; Carou, Diego
he present paper shows an experimental study on additive manufacturing for obtaining samples of polylactic acid (PLA). The process used for manufacturing these samples was fused deposition modeling (FDM). Little attention to the surface quality obtained in additive manufacturing processes has been paid by the research community. So, this paper aims at filling this gap. The goal of the study is the recognition of critical factors in FDM processes for reducing surface roughness. Two different types of experiments were carried out to analyze five printing parameters. The results were analyzed by means of Analysis of Variance, graphical methods, and non-parametric tests using Spearman’s ρ and Kendall’s τ correlation coefficients. The results showed how layer height and wall thickness are the most important factors for controlling surface roughness, while printing path, printing speed, and temperature showed no clear influence on surface roughness.
A material model to reproduce mixed-mode fracture in concrete
(Wiley, 2018-08) Suárez Guerra, Fernando; Gálvez, Jaime C.; Cendón , David A.
This paper presents a material model to reproduce crack propagation in cement-based material specimens under mixed-mode loading. Its numerical formulation is based on the cohesive crack model, proposed by Hillerborg, and extended for the mixed-mode case. This model is inspired by former works by Gálvez et al but implemented for its use in a finite element code at a material level, that is to say, at an integration point level. Among its main features, the model is able to predict the crack orientation and can reproduce the fracture behaviour under mixed-mode fracture loading. In addition, several experimental results found in the literature are properly reproduced by the model.
Force Prediction for Incremental Forming of Polymer Sheets
(MDPI, 2018-09-03) Medina Sánchez, Gustavo; García Collado, Alberto; Carou Porto, Diego; Dorado Vicente, Rubén
Incremental sheet forming (ISF) is gaining attention as a low cost prototyping and small batch production solution to obtain 3D components. In ISF, the forming force is key to define an adequate setup, avoiding damage and reducing wear, as well as to determine the energy consumption and the final shape of the part. Although there are several analytical, experimental and numerical approaches to estimate the axial forming force for metal sheets, further efforts must be done to extend the study to polymers. This work presents two procedures for predicting axial force in Single Point Incremental Forming (SPIF) of polymer sheets. Particularly, a numerical model based on the Finite Element Model (FEM), which considers a hyperelastic-plastic constitutive equation, and a simple semi-analytical model that extends the known specific energy concept used in machining. A set of experimental tests was used to validate the numerical model, and to determine the specific energy for two polymer sheets of polycarbonate (PC) and polyvinyl chloride (PVC). The approaches provide results in good agreement with additional real examples. Moreover, the numerical model is useful for accurately predicting temperature and thickness.
Improving composite tensile properties during resin infusion based on a computer vision flow-control approach
(Multidisciplinary Digital Publishing Institute, 2018-12-05) Almazán-Lázaro, Juan Antonio; López-Alba, Elías; Díaz-Garrido, Francisco Alberto
Liquid composite manufacturing techniques, mainly applied in the transport industry, have been studied and optimized for decades while defect analysis and its minimization have been a goal to increase reliability and mechanical performance. Researchers have found that many process parameters have a strong influence on the mechanical behavior of composite structures where the flow front velocity, closely related to voids, plays a considerable role. In this work, the optimal flow front velocity was evaluated and controlled using a computer vision system for different laminates improving the mechanical tensile properties and void content. Enhanced mechanical tensile properties were found using a feedback flow-controller vision system which was able to keep the optimal flow front velocity constant to reduce the air traps among tows and fibers. Tensile strength was enhanced up to 18% for fiber orientation at 0◦ and 3.3% at 90◦, whereas tensile modulus was increased up to 18.4% for fibers at 0◦ and 8.7% at 90◦. A novel methodology is presented through this work, aiming to improve the robustness of resin film infusion (RFI) processes while ensuring the quality of the composite material.
An alternative procedure to measure railroad track irregularities. Application to a scaled track
(ELSEVIER, 2019) Fernández-Aceituno, Javier; Chamorro, Rosario; Muñoz-Moreno, Sergio; Escalona, José Luis
In this paper an alternative procedure to accurately measure static railroad track irregularities is proposed and applied to a scaled railroad track. The purpose of this work is the determination of highlyprecise measured data in short track segments that needs to be used as input in the validation of railroad computational models that are used for on-board railroad track measurement systems. The procedure consists of the use of a topographic total station combined with a postprocessing of the measured data that reduces misalignment errors and provide the analytical ideal geometry of the track together with its irregular geometry characterized in terms of the magnitudes of track gauge, vertical profile, alignment and cross level. Experimental results are compared to standard magnitudes of full scale tracks showing that real track geometry can differ from PSD-based predicted one. This supports the application of the proposed procedure for an accurate geometric determination of short track segments.
Multibody simulation of railway vehicles with contact lookup tables
(ELSEVIER, 2019) Escalona, José Luis; Fernández-Aceituno, Javier
The use of contact lookup tables is widely used in multibody railway simulations to increase the computational efficiency. However, due to simplifying assumptions the use of contact lookup tables decreases the accuracy of the simulation results. This paper analyses the increase of computational efficiency and loss of accuracy for a particular multibody simulation. To this end the results based on contact lookup tables are compared with the results of the online solution of the wheel-rail contact constraints. The formulation used to compute the equations of motion of railway vehicles has the following features: (1) the equations of motion are obtained using a systematic procedure based on multibody dynamics, (2) generalized forces included in the equations of motion are obtained using symbolic computations when possible, (3) generalized coordinates are referred to a non-inertial track frame, (4) the equations of motion are obtained using a velocity transformation of the Newton–Euler equations of the vehicle bodies, which are assumed to be rigid and (5) wheel-rail tread contact and flange contact are treated with pre-calculated lookup tables which can take into account the track irregularities. The comparative study presented in this paper shows that this formulation can be used to simulate the dynamics of a railway vehicle in real-time.
Modelling fracture on polyolefin fibre reinforced concrete specimens subjected to mixed-mode loading
(Elsevier, 2019-02) Suárez-Guerra, Fernando; Gálvez-Ruíz, Jaime Carlos; Enfedaque, Alejandro; García-Alberti, Marcos
In recent years, polyolefin fibres have proved a remarkable performance as reinforcement of concrete, which has inspired a number of studies involving, among others, the simulation of fracture on polyolefin fibre reinforced concrete (PFRC) specimens. Fracture has been successfully reproduced on PFRC specimens in the past by means of an embedded crack model with a trilinear softening function, but always using for comparison the classical three-point bending test, which employs a symmetrical setup and induces fracture under pure mode I conditions. In the present study, six sets of specimens tested under an alternative setup of the three-point bending test, which induces fracture under mixed-mode conditions (I and II), are simulated using the same numerical approach. The results not only prove that the use of a trilinear softening function together with an embedded cohesive crack approach can reproduce fracture under mixed-mode conditions, but also provide interesting insights on how the trilinear softening function may be designed for suiting the usage of different fibre lengths or varying the proportions of polyolefin fibres.
The Evolution of Internal Damage Identified by Means of X-ray Computed Tomography in Two Steels and the Ensuing Relation with Gurson’s Numerical Modelling
(MDPI, 2019-03) Suárez-Guerra, Fernando; Sket, Federico; Gálvez-Ruíz, Jaime Carlos; Cendón, David Ángel; Atienza, José Miguel; Molina-Aldareguia, Jon
This paper analyzes the evolution of the internal damage in two types of steel that show different fracture behaviors, with one of them being the initial material used for manufacturing prestressing steel wires, and the other one being a standard steel used in reinforced concrete structures. The first of them shows a flat fracture surface perpendicular to the loading direction while the second one shows the typical cup-cone surface. 3 mm-diameter cylindrical specimens are tested with a tensile test carried out in several loading steps and, after each of them, unloaded and analyzed with X-ray tomography, which allows detection of internal damage throughout the tensile test. In the steel used for reinforcement, damage is developed progressively in the whole specimen, as predicted by Gurson-type models, while in the steel used for manufacturing prestressing steel-wire, damage is developed only in the very last part of the test. In addition to the experimental study, a numerical analysis is carried out by means of the finite element method by using a Gurson model to reproduce the material behavior.
Characterisation of fatigue crack growth using digital image correlation measurements of plastic CTOD.
(Elsevier, 2019-03-27) Vasco, José Manuel; Diaz-Garrido, Francisco Alberto; Antunes, Fernando Ventura; James, Neil
Crack tip opening displacement (CTOD) was measured using digital image correlation (DIC) and resolved into elastic and plastic CTOD components via an offset compliance technique. The plastic CTOD range gave a single linear correlation for fatigue crack growth rate at stress ratios of 0.1 and 0.6 in compact- tension (CT) specimens of Grade 2 titanium. A sensitivity analysis was performed to find the optimum position in the crack wake to make the CTOD measurements. The results are the first time (to the authors knowledge) that plastic CTOD has been found directly from experimentation and demonstrate that plastic CTOD is a useful alternate characterising parameter for fatigue crack growth to the stress intensity factor defined by Irwin.
FP+DIC for low-cost 3D full-field experimental modal analysis in industrial components
(ELSEVIER, 2019-04-07) Felipe-Sesé, Luis; Molina-Viedma, Ángel J.; López-Alba, Elías; Díaz, Francisco A.
High Speed 3D Digital Image Correlation has reached notorious popularity in dynamic characterisations because of the full-field non-invasive performance. It is being especially relevant for experimental modal analysis due to the importance of the modal parameters to define the dynamic behaviour. However, the economic cost of a stereoscopic system of two high speed cameras is a main concern regarding traditional instrumentations. In the search for low-cost alternatives, different methodologies have arisen that employ a single camera for 3D measurements. One approach consists in obtaining a stereo-vision in a single image using, for instance, a mirror system. These approaches involve important field of-view restrictions. An interesting approach employs the full resolution by combining Fringe Projection and 2D-DIC for out-of-plane and in-plane displacements, respectively. In this study, this technique is explored to perform experimental modal analysis in a large non-flat aeronautical panel. The validation of the results has been performed using accelerometer measurements during an impact hammer test. The results of the study stand this technique as an attractive low-cost technique for 3D full-field modal characterisations of complex components
The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes
(Elsevier, 2019-04-12) Bohórquez, Patricio; Cañada-Pereira, Pablo; Jiménez-Ruiz, Pedro Jeús; del-Moral-Erencia, José David
Exceptional megaflood-scale bedforms on Earth are commonly associated with the catastrophic draining of glacial lakes in the late Pleistocene. The widest studied events have been the Missoula and Altai floods with 300–700 m flow depth, 1–20 m bedform height and 10–300 m wavelength. Nowadays, the Saint-Venant equations have succeeded at simulating the catastrophic glacial-lake drainage process numerically, but we still lack a depth-averaged morphodynamic theory able to predict the growth of dunes and antidunes. The disparity of spatial scales in megafloods prevents the use of non-depth-averaged rotational flow equations, motivating the present shallow-water theory for the formation of megaflood-scale bedforms. We adopt a non-equilibrium sediment transport equation rooted in Einstein's pioneering work. Here we prove that the bed instability triggers to form dunes and antidunes simply by lagging the entrainment term for sediment mass conservation, or the bottom shear stress, with respect to the depth-averaged flow velocity. We formalise this result using a linear stability theory that captures the existence regions of dune and antidune in addition to the roll wave instability. Furthermore, in the spirit of Kennedy (Annu. Rev. Fluid Mech., vol. 1, 1969, pp. 147–168), we derive a closed-form solution of growth rate and wave speed of the bedform. The nondimensional groups controlling the linear instabilities are the Froude number, ℱr, the Shields parameter, Sh, and the grain roughness relative to flow depth, Subsequently, we simulate the drainage of the largest Missoula flood numerically to explain the formation of giant antidunes in the Camas Prairie (Montana, US) during the late stage of the megaflood. Also considered are large fields of gravel dunes in the Kuray-Chuja Lake Basin (Altai Mountains, Siberia). The simulated hydraulic conditions over bedforms in both basins yield values of the nondimensional parameters that lie in the theoretical region of dunes and antidunes according to the proposed theory and in situ measurements in sandy rivers and flume experiments.
Alternative Calibration of Cup Anemometers: A Way to Reduce the Uncertainty of Wind Power Density Estimation
(MDPI, 2019-04-30) Guerrero-Villar, Francisca; Dorado-Vicente, Rubén; Medina-Sánchez, Gustavo; Torres-Jiménez, Eloísa
This study presents a procedure to reduce the uncertainty of wind power density estimations, which is useful to improve the energy production predictions of wind farms. Power density is usually determined from the wind speed measured by a cup anemometer and the air density value (conventional procedure). An alternative procedure based on wind speed and dynamic pressure estimations provided by a cup anemometer is proposed. The dynamic pressure is obtained by means of a calibration curve that relates the anemometer rotation frequency and the dynamic pressure measured by a Pitot tube. The quadratic regression, used to define the calibration curve, and its uncertainty are both detailed. A comparison between the alternative procedure and the conventional one points out the advantage of the proposed alternative since results show a high reduction of the indirect measurement uncertainty of wind power density.

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