Kerf Taper Defect Minimization Based on Abrasive Waterjet Machining of Low Thickness Thermoplastic Carbon Fiber Composites C/TPU

Carbon fiber-reinforced thermoplastics (CFRTPs) are materials of great interest in industry. Like thermosets composite materials, they have an excellent weight/mechanical properties ratio and a high degree of automation in their manufacture and recyclability. However, these materials present di culties in their machining due to their nature. Their anisotropy, together with their low glass transition temperature, can produce important defects in their machining. A process able to machine these materials correctly by producing very small thermal defects is abrasive waterjet machining. However, the dispersion of the waterjet produces a reduction in kinetic energy, which decreases its cutting capacity. This results in an inherent defect called a kerf taper. Also, machining these materials with reduced thicknesses can increase this defect due to the formation of a damage zone at the beginning of cut due to the abrasive particles. This paper studies the influence of cutting parameters on the kerf taper generated during waterjet machining of a thin-walled thermoplastic composite material (carbon/polyurethane, C/TPU). This influence was studied by means of an ANOVA statistical analysis, and a mathematical model was obtained by means of a response surface methodology (RSM). Kerf taper defect was evaluated using a new image processing methodology, where the initial and final damage zone was separated from the kerf taper defect. Finally, a combination of a hydraulic pressure of 3400 bar with a feed rate of 100 mm/min and an abrasive mass flow of 170 g/min produces the minimum kerf taper angle

Analysis of Secondary Adhesion Wear Mechanism on Hard Machining of Titanium Aerospace Alloy

Titanium alloys are widely used in important manufacturing sectors such as the aerospace industry, internal components of motor or biomechanical components, for the development of functional prostheses. The relationship between mechanical properties and weight and its excellent biocompatibility have positioned this material among the most demanded for specific applications. However, it is necessary to consider the low machinability as a disadvantage in the titanium alloys features. This fact is especially due to the low thermal conductivity, producing significant increases in the temperature of the contact area during the machining process. In this aspect, one of the main objectives of strategic industries is focused on the improvement of the efficiency and the increase of the service life of the elements involved in the machining of this alloy. With the aim to understand the most relevant effects in the machinability of the Ti6Al4V alloy, an analysis is required of different variables of the machining process like tool wear evolution, based on secondary adhesion mechanisms, and the relation between surface roughness of the work-pieces with the cutting parameters. In this research work, a study on the machinability of Ti6Al4V titanium alloy has been performed. For that purpose, in a horizontal turning process, the influence of cutting tool wear effects has been evaluated on the surface finish of the machined element. As a result, parametric behavior models for average roughness (Ra) have been determined as a function of the machining parameters used

Cutting Forces Parametric Model for the Dry High Speed Contour Milling of Aerospace Aluminium Alloys

Cutting forces is one of the most important outputs in material removal machining processes. Their values depend on a large number of parameters, such as the cutting tool material and geometry, the workpiece material or the cutting parameters, among others. In this paper, cutting forces behavior have been analyzed as a function of feedrate and cutting speed, for the high-speed peripheral milling of UNS A92024-T3 (Al-Cu) stacks. This alloy is widely used in the manufacturing process of aircraft structural elements. From this analysis, different parametric models have been adjusted to experimental data, establishing Fn=f(fz,V) relationships that allow an approximation to the values of force components for machining conditions dependent on those variables

Impact of Chemical Post-Processing in Fused Deposition Modelling (FDM) on Polylactic Acid (PLA) Surface Quality and Structure

The application of techniques to improve the surface finish of pieces obtained by fused deposition modelling, as well as other functional aspects, is of great interest nowadays. Polylactic acid, a biodegradable material, has been considered a possible substitute for petroleum-based polymers. In this work, different chemical post-processing methods are applied to polylactic acid pieces obtained by fused deposition modelling and some characteristics are studied. Structural, thermal, and crystallinity property changes are analyzed according to the treatments applied. This can prevent degradation, eliminate the glass transition phase of the material, and thereby increase the thermal resistance by about 50 C. An improvement in the roughness of the pieces of up to 97% was also found

Shipbuilding 4.0 Index Approaching Supply Chain

The shipbuilding industry shows a special interest in adapting to the changes proposed by the industry 4.0. This article bets on the development of an index that indicates the current situation considering that supply chain is a key factor in any type of change, and at the same time it serves as a control tool in the implementation of improvements. The proposed indices provide a first definition of the paradigm or paradigms that best fit the supply chain in order to improve its sustainability and a second definition, regarding the key enabling technologies for Industry 4.0. The values obtained put shipbuilding on the road to industry 4.0 while suggesting categorized planning of technologies

Machining of Al-Cu and Al-Zn Alloys for Aeronautical Components

Machining operations are chosen by aircraft manufacturers worldwide to process light aluminum alloys. This type of materials presents good characteristics in terms of weight and physicochemical properties, which combined with a low cost ratio making them irreplaceable in aircraft elements with a high structural commitment. Conventional machining processes such as drilling, milling and turning are widely used for aeronautical parts manufacturing. High quality requirements are usually demanded for these kinds of components but aluminum alloys may present some machinability issues, basically associated to the heat generated during the process. Among others, surface quality and geometrical deviations are highly influenced by the condition of the cutting-tool, its wear and the cutting parameters. Consequently, the understanding of the relationship among the process parameters, the quality features and the main wear mechanism is a key factor for the improvement in the productivity. In this chapter, the fundamental issues of drilling, milling and turning are addressed, dealing with the relationship between cutting parameters, wear phenomena and micro and macro geometrical deviations

Recurrence-based analysis of barrier breakup in the standard nontwist map

We wish to acknowledge the support: CNPq, CAPES, and FAPESP.Peer reviewedPublisher PD

A governança do turismo em um município do nordeste brasileiro: uma análise em base ao conceito de destinos turísticos inteligentes

O estudo tem como objetivo analisar a governança no planejamento da atividade turística com base no conceito de destinos turísticos inteligentes, em um municipio do nordeste brasileiro. Mediante a análise dos Planos de Desenvolvimento Turístico (n=4) e da realização de entrevistas a informantes-chave (n=8) envolvidos com o planejamento do turismo, realizou-se um estudo qualitativo, exploratório e descritivo no município de Aracaju-Sergipe. A ausência de uma visão estratégica em nível local, de coordenação entre instrumentos e organismos da administração local e regional, e de organismos colegiados foram as principais debilidades identificadas. Por outro lado, desde uma perspectiva positiva, foi identificada a existência de um planejamento estratégico em âmbito estadual com dotação orçamentária suficiente e com medidas de monitoramento. O Estado apresenta um importante papel para o desenvolvimento turístico no município estudado, onde a governança ainda apresenta fragilidades. As variáveis/indicadores utilizados neste estudo podem auxiliar na implementação de medidas para melhorar a eficiência da governança no planejamento turístico na região