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Prediction of Surface Roughness of SLM Built Parts after Finishing Processes Using an Artificial Neural Network
Full text linkA known problem of additive manufactured parts is their poor surface quality, which influences product performance. There are different surface treatments to improve surface quality: blasting is commonly employed to improve mechanical properties and reduce surface roughness, and electropolishing to clean shot peened surfaces and improve the surface roughness. However, the final surface roughness is conditioned by multiple parameters related to these techniques. This paper presents a prediction model of surface roughness (Ra) using an Artificial Neural Network considering two parameters of the SLM manufacturing process and seven blasting and electropolishing processes. This model is proven to be in agreement with 429 experimental results. Moreover, this model is then used to find the optimal conditions to be applied during the blasting and the electropolishing in order to improve the surface roughness by roughly 60%
A post-processing technique for removing ‘irregular frequencies’ and other issues in the results from BEM solvers
Full text linkWithin the wave energy community, hydrodynamic coefficients obtained from boundary element methods (BEMs) are commonly used to predict the behaviour of wave energy converters (WECs) in response to incident waves. A number of commercially-available BEM solvers exist, with a number of open-source alternatives also available. While open-source solvers have an obvious cost advantage compared to their commercial counterparts, the results from such solvers are often susceptible to so-called ‘irregular frequencies’, which arise from ill-conditioning in boundary integral problems, and result in large under- or over-estimation of hydrodynamic parameters at certain excitation frequencies. Furthermore, while commercial solvers may employ techniques to suppress the effects of irregular frequencies, such solvers may, under certain circumstances, exhibit other problems in the hydrodynamic results produced. For example, the results obtained for the added mass at high frequencies, and the infinite frequency added mass for a water column, may be incorrect. The current work first focusses on an approach to remove the effects of irregular frequencies from the results obtained for the radiation damping of a particular WEC geometry. The use of radiation damping results to obtain values for the added mass, through the use of the Ogilvie relations, is then considered.
The technique described herein has been implemented in BEMRosetta, an open-source tool which allows a user to view the results from various BEM solvers, as well as converting input files between solvers. The results presented in this paper have been obtained using the BEMRosetta implementation
Influence of Coulomb’s Friction Coefficient in Finite Element Modeling of Orthogonal Cutting of Ti6Al4V
Full text linkThe reliability of the pertinent parameters set of Johnson-Cook constitutive model is highly linked with the friction condition at the tool-chip-workpiece interface. In the present work, a study on the influence of Coulomb’s friction coefficient on the observables such as forces, chip thickness and chip curvature by FE simulation of orthogonal cutting of Ti6Al4V alloy has been carried out. A FE model with an Arbitrary Lagrangian-Eulerian (ALE) approach is employed to simulate the cutting process for different cutting conditions. The simulated results, for a wide range of friction conditions, are analyzed and compared with experimental results. The analysis show that the Coulomb’s friction coefficient has a direct link with the observables. The paper reveals that for accurate prediction of observables an optimized value of the coefficient of friction in correlation with the parameters values of the constitutive model is imperative
Evolutionary generation of metamorphic relations for cyber-physical systems
Full text linkA problem when testing Cyber-Physical Systems (CPS) is the difficulty of determining whether a particular system output or behaviour is correct or not. Metamorphic testing alleviates such a problem by reasoning on the relations expected to hold among multiple executions of the system under test, which are known as Metamorphic Relations (MRs). However, the development of effective MRs is often challenging and requires the involvement of domain experts. This paper summarizes our recent publication: "Generating Metamorphic Relations for Cyber-Physical Systems with Genetic Programming: An Industrial Case Study", presented at ESEC/FSE 2021. In that publication we presented GAssertMRs, the first technique to automatically generate MRs for CPS, leveraging GP to explore the space of candidate solutions. We evaluated GAssertMRs in an industrial case study, outperforming other baselines
Thrust Ripple Reduction in Linear Switched-Flux Machines via Additional Pole Optimisation
Full text linkLinear switched-flux machines are a kind of permanent magnet machine with a passive ferromagnetic secondary. Therefore, they can achieve both a good performance and a low cost in long stroke applications. However, due to the end effect, these machines generate high detent force and on load thrust force ripples. There are several solutions in the literature that aim to minimise the thrust ripple. One of those solutions is the placement of additional poles in the ends of the machine. These can be passive, i. e. simple ferromagnetic teeth, or active, with additional magnets. The former is the most common solution in the literature. In this article, the optimal configuration of the additional poles is discussed via 4 additional pole sizing strategies, and the influence of the design variables and optimisation objectives is analysed. Then, a generic additional pole configuration is proposed, which combines a high effectiveness and a simple design. Finally, an experimental validation is carried out, and the measurements confirm the results from the optimisation
Evaluación heurística de la interacción persona-robot en entornos industriales
No full textEn la nueva industria cada vez son más los robots utilizados. Para aprovechar al máximo los beneficios que los robots pueden ofrecer, es necesario generar una interacción fluida y satisfactoria persona-robot, de modo que se refuerce una relación simbiótica entre ambos. Un aspecto clave para el éxito de la Interacción Persona-Robot (HRI) es centrarse en la experiencia de usuario (UX). En este sentido, la evaluación heurística se presenta como una herramienta eficaz, ya que permite identificar problemas de diseño mediante una aplicación sencilla y de bajo coste. El objetivo de este trabajo es desarrollar un nuevo listado de heurísticos para evaluar la HRI en entornos industriales. Se han considerado una serie de dimensiones para constituir el nuevo listado: (i) seguridad, confianza y seguridad percibida, (ii) ergonomía física, (iii) ergonomía cognitiva y emociones, (iv) inclusividad, (v) tipos de interfaces y (vi) tipos de robots y funcionalidades. Para ello, se ha realizado una búsqueda de la literatura y una agrupación de los heurísticos identificados. Finalmente se propone un listado de heurísticos compuesto de los siguientes apartados y que considera en cada una de ellas las dimensiones mencionadas (i) aspectos generales, (ii) funcionalidades y (iii) tipos de interfaces
Partial Power Processing Based Converter for Electric Vehicle Fast Charging Stations
Full text linkThis paper focuses on the design of a charging unit for an electric vehicle fast charging station. With this purpose, in first place, different solutions that exist for fast charging stations are described through a brief introduction. Then, partial power processing architectures are introduced and proposed as attractive strategies to improve the performance of this type of applications. Furthermore, through a series of simulations, it is observed that partial power processing based converters obtain reduced processed power ratio and efficiency results compared to conventional full power converters. So, with the aim of verifying the conclusions obtained through the simulations, two downscaled prototypes are assembled and tested. Finally, it is concluded that, in case galvanic isolation is not required for the charging unit converter, partial power converters are smaller and more efficient alternatives than conventional full power converters
Potentzia prozesamendu partzialean oinarritutako bihurgailuak
Full text linkIn recent years, many research lines have made efforts to improve the performance of power converters. In this context, literature proposes strategies based on partial power processing, in which the power to be processed by the converter is reduced. Thus, the losses produced are reduced, as does its size. Taking this into account, the main objective of this research work is to describe the current state of partial power processing, to understand its functioning, and to study its advantages and disadvantages.Azken urteotan, ikerketa-ildo askok potentzia-bihurgailuen errendimendua hobetzeko ahaleginak egin dituzte. Testuinguru horretan, literatura zientifikoan ageri den proposamenetako bat potentziaren prozesamendu partziala da. Estrategia hauen helburua potentziako bihurgailuak prozesatu beharreko potentzia murriztea da. Horrela, bihurgailuak sortutako galerak gutxitzen dira, bere tamaina bezalaxe. Hori kontuan hartuta, ikerketa-lan honen helburu nagusiak potentzia prozesamendu partzialaren egungo egoera deskribatzea, haren funtzionamendua ulertzea eta haren abantailak eta desabantailak zehatz-mehatz aztertzea dira
A Model for Measuring and Managing the Impact of Design on the Organization: Insights from Four Companies
Full text linkIncreasing numbers of companies are looking to embed design as a strategic capability to meet today’s business and social challenges. However, integrating design in an organization is a challenge, due to the scarcity of knowledge on managing this process and measuring its impact. This study presents a model for measuring and managing the impact of design on the organization (DIMM). The model builds on four levels of design impact identified in the literature: results, perception, processes, and design culture. The model was tested with four service companies that have recently developed design capabilities. To this end, those responsible for the integration of design were interviewed, using the model itself as an interview guide to confirm its usefulness and identify possible improvements. The results showed that the model was useful to assess the impact of design on companies with emerging design capabilities, but also as a reflection and management tool to align design with strategic objectives and promote its integration into the organization. Finally, future research should test the model longitudinally, as well as in a broader scope of organizations, to validate its usefulness for organizations with greater design maturity
Petri net implementation in programmable logic controllers: methodology for development and validation
Full text linkLead times are key to good market positioning of providers of automated solutions based on a programmable logic controller (PLC). Testing control software against a digital twin (DT) of the process, any programming errors that may have incurred are detected before commissioning, which reduces project duration. This work raises the possibility of reducing that probability of error when programming discrete event dynamic systems (DEDS), by implementing a Petri net (PN) managing algorithm. A framework is presented which combines the use of this algorithm, by means of pre-incidence and post-incidence matrices and initial marking vector of a net, with code validation through emulation. A use case is brought forward in which the control program of a sequential process with parallel operations is implemented, with both virtual (VC) and real commissioning