Analysis and comparison of a hydraulic and pneumatic system using the Dymola software

This work addresses the modelling of a system using Modelica language and the Dymola software tool. Dymola is a modelling and simulation environment that uses the open Modelica language to map hardware components of physical systems directly into software components. Therefore, this modelling language allows the user to model a system in a physical form, rather than a mathematical fashion, through the use of general equations, objects, and links. This paper as an informative character about a tool for the development of mechatronic systems. The topics covered here are part of a more extensive modelling and simulation work on the dynamics of mechanical systems, within the scope of an Integrated Master in Mechanical Engineering. This study was carried out based on the comparison between pneumatic and hydraulic models of the same system. Therefore, it was modeled a system used in backhoe loaders that can be operated either using a hydraulic or a pneumatic cylinder. The activity focuses, essentially, on the analysis of parameters that describe the behaviour of the system, emphasizing the position, velocity, acceleration and loads observed in both cylinders. The goal is to introduce the reader to the Dymola environment and Modelica language by addressing the modelling of a system. This study also pretends to identify significant differences regarding the behaviour performance of the pneumatic and hydraulic approaches to model the selected system, and the causes that lead to such differences.(undefined)info:eu-repo/semantics/publishedVersio

Production and optimization of 316L stainless steel dimples by laser surface texturing using Nd: YAG laser

Surface patterning is of increasing interest in modern manufacturing processes to achieve better results in terms of wear resistance and friction of mechanical parts and tools and, consequently, to improve their lifetime in service conditions [1]. Several approaches have been used to modify the surface properties of steel components, namely deposition of coatings, sandblasting, and texturing by electron beam, electric arc, or laser ablation [1,2]. In this work, laser technology was explored to produce dimples on the surface of 316L stainless steel samples. The production of textures can have several purposes, namely in tribological applications where they can reduce wear by acting as a reservoir for the lubricant or be reinforced with other materials (e.g. ceramics or intermetallic compounds), capable of improving the surface properties [1–3]. This work presents a detailed study on the texturing of a 316L stainless steel (dimples - circle design) by an Nd: YAG laser and its surface characterization by Scanning Electron Microscopy and analysis software (Image J) for obtaining their width (diameter) and depth. The texturing parameters are discussed herein. Results show that the width of the dimples is little influenced by the scan speed and wobble, but strongly affected by the combination of laser power and number of passes. On the other hand, wobble strongly influenced the depth of the dimples.This work was supported by FCT (Fundação para a Ciência e a Tecnologia) national funds, under the national support to R&D units grant, through the grant SFRH/BD/147460/2019, the project UIDB/04436/2020 and UIDP/04436/2020 and, also by project UIDB/00285/2020

3D Multi-Material Laser Powder Bed Fusion of 420 stainless steel-Cu parts for Plastic Injection Mold Inserts

Plastic injection molding is one of the fastest-growing industries in the world. However, although it presents numerous advantages, the costs associated with the mold and machine are high and, therefore, this process is only profitable for mass production. Moreover, the reduction in the cycle time, more specifically the cooling time, has been a never-ending challenge since it has a direct influence on production costs. This study is focused on the production of 420 stainless steel-copper solutions by 3D multi-material laser powder bed fusion. This novel material’s design concept allows combining the high mechanical resistance of the steel alloy and the high thermal conductivity of the copper. The processing parameters and strategies as well as the transition zone between these materials are of the most challenging and important aspects both from a mechanical and metallurgical point of view. The obtained results show that this approach is effective to produce inserts of copper in a 420 stainless steel capable of improving the in-service conditions of a plastic injection mold, enhancing its performance and life

Optimization of zirconia surface textured designs using Nd:Yag laser for biomedical applications

The development of surface textured designs has influence in primary stability of surgically placed implants since a textured surface allows to firmer mechanical link to the surrounding tissue. Laser technology has been investigated to develop new surface designs on green zirconia compacts by cold pressing. Nd:Yag laser were used to produce several strategies and different laser parameters (laser power, speed and laser passages) were tested to evaluate their impact on cavities geometry and depth. The surface texture designs were analysed by Scanning Electron Microscopy (SEM) and regular geometries such as cavities or pillars were observed. The distance between lines have a strong impact on texturing quality and should be combined with optimum power and speed conditions. Regarding the optimized conditions, several surface textured patterns were created in both green and sintered zirconia compacts. This study allowed to conclude that only some texturing strategies are suitable to obtain high quality surface textured patterns. Otherwise, the remaining strategies are potential solutions for obtaining high quality machined structures (laser does not machine cavities but crosses the entire bulk). High strength zirconia scaffolds were machined by laser and CNC machining technologies and the two promising technologies were compared.This work is supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/148031/2019, the project UIDB/04436/2020 and UIDP/04436/2020

Design e manufatura de peças híbridas multi-material de elevada condutividade térmica para a indústria de moldes de injeção de plásticos

Programa doutoral em Engenharia MecânicaUm dos principais desafios da indústria da moldação por injeção de plásticos está relacionado com o elevado tempo de arrefecimento após o ciclo de injeção. Este problema leva à diminuição da capacidade de produção e a um consequente aumento do custo associado ao processo e aos componentes finais. Nos últimos anos, a competitividade e o aumento da procura de um processo mais eficiente impulsionaram a investigação de novas abordagens relativas ao design e à utilização de diferentes materiais. No entanto, atualmente ainda não é possível combinar o efeito dos canais de arrefecimento e materiais de elevada condutividade térmica sem afetar a vida útil e as propriedades do molde. Idealmente, um molde de injeção de plásticos deve exibir propriedades mecânicas adequadas para suportar as tensões cíclicas (mecânicas e térmicas) inerentes ao processo, ser resistente à corrosão e ao desgaste provocados pelo contacto constante com o material a ser injetado e ter elevada condutividade térmica para tornar o arrefecimento mais eficiente, diminuindo o tempo de ciclo. Neste sentido, esta tese de doutoramento foca-se no desenvolvimento e na produção de componentes multi-funcionais multi-material com o intuito de superar os problemas acima referidos e assim aumentar a performance dos moldes de injeção de plásticos. Para tal, desenvolveram-se soluções que envolvem a combinação de diferentes técnicas de fabricação de ponta e materiais capazes de preservar as características de um molde convencional e melhorar significativamente a sua capacidade térmica. Deste modo, foram produzidas soluções multi-material à base de aço inoxidável 420-cobre. Esta abordagem visa adicionar novas funções a estes moldes ao introduzir conceitos como propriedades mecânicas aliadas a uma adequada performance térmica. Estas soluções foram caraterizadas quanto ao seu desempenho termo-mecânico, demonstrando uma combinação de propriedades adequadas para criar uma solução efetiva a longo prazo, de acordo com as especificações locais.One of the main challenges in the plastic injection moulding industry is related to the long cooling time after the injection cycle. This problem leads to a decrease in production capacity and a consequent increase in the cost associated with the process and final components. In the last few years, competitiveness and the increased demand for a more efficient process boosted the research on new approaches to the design and use of different materials. However, currently, it is not yet possible to combine the effect of the cooling channels with materials of high thermal conductivity without affecting the lifetime and properties of the mould. Ideally, a plastic injection mould should display suitable mechanical properties to withstand the cyclic mechanical and thermal stresses inherent to the process, be resistance to corrosion and wear due to constant contact with the material to be injected, and have high thermal conductivity to make cooling more efficient, reducing the cycle time. In this sense, this PhD thesis is focused on the development and production of multi-functional multi-material components to overcome all the above-mentioned issues and to increase the performance of the plastic injection moulds. For that purpose, solutions have been developed that involve the combination of different cutting-edge fabrication techniques and materials capable of preserving the characteristics of a conventional mould and significantly improving its thermal capacity. Hence, multi-material solutions based on 420 stainless steel-copper were produced. This approach aims to add new functions to these moulds by introducing concepts like mechanical properties allied to suitable thermal performance. These solutions were characterised by their thermo-mechanical performance, showing a suitable combination of properties to create a long-term and effective solution according to local requirements.I would like to acknowledge Fundação para a Ciência e a Tecnologia for my PhD grant SFRH/BD/147460/2019

Analysis and comparison of a hydraulic and pneumatic system

This work addresses the modeling of a system using Modelica language and the Dymola software tool. Dymola is a modeling and simulation environment that uses the open Modelica language to map hardware components of physical systems directly into software components. Therefore, this modeling language allows the user to model a system in a physical form, rather than a mathematical fashion, through the use of general equations, objects, and links. This paper as an informative character about a tool for the development of mechatronic systems. The topics covered here are part of a more extensive modeling and simulation work on the dynamics of mechanical systems, within the scope of an Integrated Master in Mechanical Engineering. This study was carried out based on the comparison between pneumatic and hydraulic models of the same system. Therefore, it was modeled a system used in backhoe loaders that can be operated either using a hydraulic or a pneumatic cylinder. The activity focuses, essentially, on the analysis of parameters that describe the behavior of the system, emphasizing the position, velocity, acceleration and loads observed in both cylinders. The goal is to introduce the reader to the Dymola environment and Modelica language by addressing the modeling of a system. This study also pretends to identify significant differences regarding the behavior performance of the pneumatic and hydraulic approaches to model the selected system, and the causes that lead to such differences.info:eu-repo/semantics/publishedVersio

Influence of laser parameters on the texturing of 420 stainless steel

AISI 420 martensitic stainless steel is widely used in the mould industry due to its high tensile strength, hardness, and corrosion properties. Another requirement concerning any material used for this type of application is high thermal conductivity to minimise the time between consecutive injection cycles. The surfaces of some parts of the mould may be textured and reinforced with a material with higher thermal conductivity to achieve this aim. The results of a detailed study on the texturing of annealed 420 stainless steel using a Nd:YVO4 fibre laser are presented in this work. The influence of the laser’s processing parameters (laser power, scanning speed, number of passes, and line spacing) on the dimensions of the track, microstructure, and hardness of the modified surfaces was studied. Based on the continuity and dimensions of the machined grooves, several promising textures could be produced with laser power values from 5 to 30 W, scanning speeds of 500 to 2000 mm/s, 8 passes or more, and line spacings of 40 and 50 µm. High laser powers were responsible for the dissolution of chromium carbides in the laser tracks, the incorporation of chromium in austenite, and the consequent hardening of the microstructure.This research was funded by FCT (Fundação para a Ciência e a Tecnologia) through grant SFRH/BD/147460/2019 and reference projects UIDB/04436/2020, UIDP/04436/2020, and UIDB/00285/2020. Additionally, this work is co-financed by FEDER through the Competitiveness and Internationalization Operational Program (POCI) in the project Add. Additive, with reference POCI-01-0247-FEDER-024533

Inconel 718 produced by hot pressing: optimization of temperature and pressure conditions

This paper aims to act as a useful engineering tool for researchers who are studying the production of well-densified IN718 parts by uniaxial vacuum hot pressing. To the best of the authors’ knowledge, there is no relevant information on literature about densification of IN718 parts by this technique. This work is focused on understanding the influence of uniaxial vacuum hot pressing sintering conditions (temperature and pressure) on Inconel 718 (IN718) powder densification, microstructural, fracture mode, and hardness properties. The optimization of temperature and pressure sintering conditions are presented as well as its influence on the densification, microstructural features, and hardness properties. The sintering conditions included temperatures of 1000, 1068, 1150, and 1200 °C; pressures of 50 and 60 MPa; and a dwell time of 60 min. The results showed an increase in the grain size (GS) of the compacts with the processing temperature and a change on the fracture mode from intergranular dominant fracture to fully dimple ductile fracture. Regarding the microstructural properties, the results showed that γ′(Ni3(Al, Ti)) intermetallic precipitate originated from IN718 powders was retained in the sintered specimens. The hardness results revealed that the sintering temperature of 1000 °C is not enough to promote accurate densification. The optimum hardness results were achieved at 1200 °C (327 HV) with high levels of densification and pure intragranular fracture mode. In future studies, shear and tensile strength test should be performed in order to properly evaluate the mechanical behavior of hot-pressed IN718 specimens.Open access funding provided by FCT|FCCN (b-on). This work was supported by FCT (Fundação para a Ciência e Tecnologia) through the grant national funds, under the national support to R&D unit grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020 and SFRH/BD/148031/2019. This work was also cofnanced by FEDER, through the Competitiveness and Internationalization Operational Program (POCI), in the project Add. Additive, with the reference POCI-01-0247-FEDER-024533

Predictive models on the influence of laser texturing parameters on the Inconel 718 surface by using Nd: YVO4 laser

This work presents a detailed study on Inconel 718 alloy surface texturing by a Nd: YVO4 fibre laser aiming to create localized textured areas for further introduction of reinforcement materials for improvin relevant properties such as thermal conductivity (copper alloys), lightweight (aluminium alloys) or avoid chemical oxidizing reactions (stainless steel alloys).Various laser parameters - there are laser power (P), scan speed (S) and number of passes (N) - and different line spacing (D) were combined. The characterization of the textured surfaces was carried out by scanning electron microscopy (SEM) and analyzed using image analysis software (Image J) to measure the depth and width of the grooves. The textured Inconel 718 specimens were etched to analyze the effect of the laser interaction with the grain morphology. The influence of laser parameters on the grain morphology was assessed by using statistical analysis. In order to find the significant main factors and their interactions an analysis of variance (ANOVA) was used.Results show high-quality textured surfaces are obtained by using low power values and medium scan speed values and remelting areas are produced when considering a low number of passes. Moreover, the grain size is larger when considering high power values when compared with non-textured areas. The mathematical models demonstrated that laser power, scan speed and number of passes affect the depth and width of the grooves. According to its significance, the power (P) is the variable that most affects width of the grooves and the number of passes (N) is the significant variable that most influences the depth variable.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects SFRH/BD/148031/2019, UIDB/04436/2020 and UIDP/04436/2020). Also, the project Add: additive -add additive manufacturing to Portuguese industry [grant number POCI-01-0247-FEDER-024533]

Multi-functional Inconel 718 - Pure Copper parts fabricated by 3D multi-material laser powder bed fusion: a novel technological and designing approach for rocket engine

Currently, most aerospace components are under extreme operating conditions such as high fluid pressure, mechanical loads, and thermal stresses [1,2]. The structural integrity of the component is assured by the use of high strength and temperature resistant materials as well distinct cooling mechanisms [1,2]. Inconel 718 (Inc718) is usually used in aerospace components (e.g rocket engines) due to their resistance to oxidation (due to the presence of Ni and Cr) and because withstand high mechanical stress at high temperatures. However, one of the main drawbacks of Inconel alloys is their low thermal conductivity (~11 W/m.K) [3] which makes difficult heat extraction of the combustion chamber at high-temperature and pressure conditions as well as reduces its energy efficiency. Moreover, these alloys display low expansion at these temperatures and offer creep resistance [4]. In regeneratively cooled rocket engines, the choice of material, with high thermal conductivity leads to an increase in heat transfer rate and so thermal efficiency [5]. Pure Copper (Pure Cu) is an exceptional thermal conductor (about 397 W/m.K) [6], with resistance oxidization in fuel-rich non-corrosive gas mixtures. However, its reflectivity and thermal conductivity have been an obstacle when processing this powder by laser powder bed fusion [7]. Carlos [7] reported the production of Pure Copper specimens by LPBF with more than 50% porosity, with poor consolidation and low mechanical strength. The joining of different materials such as Inconel 718-16SS, Ti6Al4V-Inconel 718, TiBw/Ti6Al4V composites - Inconel 718 [8] multi-material solutions have been reported in the literature. Residual stresses and defects (such as cracks) on the interface have been the main obstacles when producing multi-material specimens by additive manufacturing processes [9,10]. This technology can be disruptive once by using optimized processing parameters and low solidification times, the diffusion phenomenon can be avoided, and consequently, the formation of fragile and undesirable intermetallic phases [11]. In this regard, this study explored the use of a new Multi-Material Laser Powder Bed Fusion system to combine two completely distinct materials (Inc718 and Pure-Cu) with unique and specific properties (high strength and high thermal conductivity, respectively) in one single multi-functional component for improving heat extraction of a rocket engine. 3D multi-material metal-based parts were produced by using a new home-made 3D Multi-Material-Selective-Laser-Melting (3DMMSLM) equipment developed at CMEMS (Center for Microelectromechanical Systems) at the University of Minho.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference project SFRH/BD/148031/2019, UIDB/04436/2020 and UIDP/04436/2020