Effect of cooling methods on dimensional accuracy and surface finish of a turned titanium part

In metal cutting, the choice of cooling method influences the deformation mechanism, which is related to the dimensional accuracy and surface finish of the parts. The deformation mechanism of titanium alloys under machining conditions is known to be very different from that of commonly used industrial materials. Therefore, the effect of cooling methods on dimensional accuracy and surface finish in machining titanium is of particular interest. This paper investigates experimentally and analytically the influence of cooling method and cutting parameters on two major dimensional accuracy characteristics of a turned titanium part—diameter error and circularity, and surface finish. Data were analyzed via three methods: traditional analysis, Pareto ANOVA, and Taguchi method. The findings indicate that the cooling method has significant effect on circularity error (contribution ratio 76.75 %), moderate effect on diameter error (contribution ratio 25.00 %), and negligible effect on surface finish (contribution ratio 0.16 %)

Estudo experimental do uso de rebolos convencionais na usinagem do aço VP-50 utilizado na retificação cilíndrica, por meio de diferentes métodos de lubrirrefrigeração

A retificação é um processo de usinagem preciso, sendo uma das etapas mais caras na fabricação dos moldes para injeção de termoplásticos. Na retificação o rebolo é a ferramenta abrasiva responsável pela retirada do material. O número de tipos de abrasivos e granulometrias disponíveis são bastante grandes e junto com a quantidade de ligas possíveis, estruturas e durezas, além dos formatos, fazem com que se chegue a um número enorme de produtos. O conhecimento das suas características técnicas, vantagens, defeitos e condições de trabalho são fundamentais para os engenheiros de produto, de processos e, naturalmente, para os gerentes de área industrial, identificarem qual o rebolo mais indicado para realização do processo de retificação. Dentre os aços utilizados na fabricação de moldes para injeção de termoplásticos destaca-se o aço VP-50, o qual foi o aço usado neste experimento, sendo usinado pelo processo de retificação cilíndrica. No processo de retificação, também foi adotado para fins de experimento dois métodos de lubrirrefrigeração, sendo eles o método convencional com lubrirrefrigeração abundante e o MQL que é a técnica com mínima quantidade de lubrirrefrigeração. O objetivo deste trabalho foi analisar de forma comparativa o desempenho de corte executado com três tipos de rebolos convencionais: rebolo de óxido de alumínio branco, rebolo de carbureto de silício verde e rebolo de carbureto de silício preto com óxido de alumínio branco. Os resultados foram analisados e comparados pelas variáveis de saída dos três tipos de rebolos, tipo de refrigeração e espessura equivalente de corte

Numerical Simulation of Collision Process of High Speed Debris against Thin Plate

A collision process of a high speed debris with a spherical or cylindrical shape against a thin plate, which were parts of a satellite and made of an aluminum or its alloy, was numerically simulated based on a thermo-elasto-plastic FEM. In the simulation the effects of strain, strain rate and temperature including the heating effect resulting to melt away of materials were simultaneously considered. The collision of the high speed debrises, with larger than 2000 m/sec, causes melting away of both a debris and a plate. The spalling fracture in bottom side of a plate can be only seen in a collision of relatively slow speed debris.Cet article se concerne avec les calculs numériques utilisant themo-élasto-plastique FEM de la collision dynamic entre des gravats sphériques ou cylindriques à grande vitesse et une planche construite d'aluminium ou d'une de ces alliages et qui représente une partie d'un satellite. Dans les calculs, les effects du strain, strain-rate, et température, aussi bien que le chauffage qui fait fondre les matériaux, ont été considérés. On découvre que les collisions avec des gravats d'une vitesse plus que 2000 m/sec occasionnent le fondrage aussi bien des gravats que de la planche. Par contre, le fracture spalling à la cote derrière de la planche n'est évident qu'avec des collisions des gravats à vitesse relativement base

Numerical simulation of titanium alloy dry machining with a strain softening constitutive law

In this study, the commercial finite element software FORGE2005, able to solve complex thermo-mechanical problems is used to model titanium alloy dry machining. One of the main machining characteristics of titanium alloys is to produce a special chip morphology named “saw-tooth chip” or serrated chip for a wide range of cutting speeds and feeds. The mechanism of saw-tooth chip formation is still not completely understood. Among the two theories about its formation, this study assumes that chip segmentation is only induced by adiabatic shear band formation and thus no material failure occurs in the primary shear zone. Based on the assumption of material strain softening, a new material law was developed. The aim of this study is to analyze the newly developed model’s capacity to correctly simulate the machining process. The model validation is based on the comparison of experimental and simulated results, such as chip formation, global chip morphology, cutting forces and geometrical chip characteristics. A good correlation was found between the experimental and numerical results, especially for cutting speeds generating low tool wear

Metal machining: Theory and applications

Metal machining is the most widespread metal-shaping process in the mechanical manufacturing industry. World-wide investment in metal machining tools increases year on year - and the wealth of nations can be judged by it. This text - the most up-to-date in the field - provides in-depth discussion of the theory and application of metal machining at an advanced level. It begins with an overview of the development of metal machining and its role in the current industrial environment and continues with a discussion of the theory and practice of machining. The underlying mechanics are analysed in detail and there are extensive chapters examining applications through a discussion of simulation and process control. "Metal Machining: Theory and Applications" is essential reading for senior undergraduates and postgraduates specialising in cutting technology. It is also an invaluable reference tool for professional engineers. Professors Childs, Maekawa, Obikawa and Yamane are four of the leading authorities on metal machining and have worked together for many years. Of interest to all mechanical, manufacturing and materials engineers Theoretical and practical problems addresse