Reliability assessment of cutting tool life based on surrogate approximation methods

A novel reliability estimation approach to the cutting tools based on advanced approximation methods is proposed. Methods such as the stochastic response surface and surrogate modeling are tested, starting from a few sample points obtained through fundamental experiments and extending them to models able to estimate the tool wear as a function of the key process parameters. Subsequently, different reliability analysis methods are employed such as Monte Carlo simulations and first- and second-order reliability methods. In the present study, these reliability analysis methods are assessed for estimating the reliability of cutting tools. The results show that the proposed method is an efficient method for assessing the reliability of the cutting tool based on the minimum number of experimental results. Experimental verification for the case of high-speed turning confirms the findings of the present study for cutting tools under flank wear

Estimation of residual life of a cutting tool used in a machining process

A significant part of cost of machining is associated with non-optimum use of cutting tool. Moreover cutting tool failure is responsible for almost 20% of the machining downtime. Thus, having knowledge of residual life of cutting tool is highly recommended so as to maximise the availability time and reduce the machining cost. The aim of this work is to find out residual life of a worn cutting tool which has been used for turning of Ti-6Al-4V alloy under constant cutting condition. The lognormal distribution is used to model the cutting tool life data. Remaining useful life of cutting tool is estimated using Mean Remaining Life (MRL) function. The results obtained from model are compared with the experimental results and it shows good agreement

Machinability of Titanium Metal Matrix Composites (Ti-MMCs)

RÉSUMÉ Les composites à matrices métalliques de titane (Ti-MMCs), en tant que nouvelle génération de matériaux, ont plusieurs applications potentielles dans les domaines industriels de l’aérospatiale, et l’automobile. La présence de particules de céramique améliore les propriétés mécaniques et physiques de la matrice. Cependant, ces particules sont dures et abrasives par leur nature, ce qui cause de multiples difficultés pour leur usinabilité. L’usure sévère des outils ainsi que la vie utile très brève de ceux-ci représentent les inconvénients les plus importants de leur usinabilité. La littérature indique très peu d’études concernant leur usinabilité, en particulier pour l’estimation de la durée de vie utile et de l’usure des outils de coupe. Les outils de diamant polycristallin (PCD) semblent être le meilleur choix pour usiner les MMCs du point de vue des chercheurs. Malgré ceci, en raison de leur coût élevé, des alternatives abordables sont fort souhaitables. Les plaquettes de nitrure de bore cubique (CBN) demeurent les outils les plus durs après celles de PCD, démontrent d’excellentes qualités dont une grande résistance à l’usure, une bonne dureté à température élevée, un bas coefficient de friction et une température de fusion élevée. Toutefois, les outils de CBN n’ont pas encore été étudiés dans le contexte de l’usinage des Ti-MMCs. La présente étude élabore en profondeur les mécanismes d’usure des plaquettes de CBN durant le tournage des Ti-MMCs. La morphologie unique des faces usées des outils a été étudiée pour la première fois, menant à une nouvelle compréhension dans l’identification des mécanismes d’usure chimiques durant l’usinage des Ti-MMCs. De plus, la pleine exploitation de la vie utile des outils de coupe est critique en raison des dépenses importantes liées au remplacement non-optimal des outils de coupe. Ceci encourage fortement le développement d’une modèle fiable pour l’estimation de la vie utile pour toutes conditions de coupe. Cette étude élabore une nouvelle méthode découlant de la méthodologie d’analyse de survie (survival analysis) pour estimer les états d’usures successives des outils pour toutes conditions d’usinage des Ti-MMCs. Ce modèle statistique prend en compte la durée de l’usinage en plus des effets des paramètres de coupe. De cette manière, les résultats obtenus ont démontré un excellent accord avec les résultats expérimentaux. De surcroît, un modèle plus avancé a été développé en rajoutant l’usure des outils comme variable au modèle précédent. Il en sort un nouveau modèle proposé pour estimer la durée de vie utile restante des plaquettes usées pour des conditions d’usinage variables, en incluant l’usure actuelle des outils dans les données d’entrée. Les résultats de ce modèle ont été validés par expérimentation et le modèle concorde très bien avec les essais expérimentaux.----------ABSTRACT Titanium metal matrix composites (Ti-MMCs), as a new generation of materials, have various potential applications in aerospace and automotive industries. The presence of ceramic particles enhances the physical and mechanical properties of the alloy matrix. However, the hard and abrasive nature of these particles causes various issues in the field of their machinability. Severe tool wear and short tool life are the most important drawbacks of machining this class of materials. There is very limited work in the literature regarding the machinability of this class of materials especially in the area of tool life estimation and tool wear. By far, polycrystalline diamond (PCD) tools appear to be the best choice for machining MMCs from researchers’ point of view. However, due to their high cost, economical alternatives are sought. Cubic boron nitride (CBN) inserts, as the second hardest available tools, show superior characteristics such as great wear resistance, high hardness at elevated temperatures, a low coefficient of friction and a high melting point. Yet, so far CBN tools have not been studied during machining of Ti-MMCs. In this study, a comprehensive study has been performed to explore the tool wear mechanisms of CBN inserts during turning of Ti-MMCs. The unique morphology of the worn faces of the tools was investigated for the first time, which led to new insights in the identification of chemical wear mechanisms during machining of Ti-MMCs. Utilizing the full tool life capacity of cutting tools is also very crucial, due to the considerable costs associated with suboptimal replacement of tools. This strongly motivates development of a reliable model for tool life estimation under any cutting conditions. In this study, a novel model based on the survival analysis methodology is developed to estimate the progressive states of tool wear under any cutting conditions during machining of Ti-MMCs. This statistical model takes into account the machining time in addition to the effect of cutting parameters. Thus, promising results were obtained which showed a very good agreement with the experimental results. Moreover, a more advanced model was constructed, by adding the tool wear as another variable to the previous model. Therefore, a new model was proposed for estimating the remaining life of worn inserts under different cutting conditions, using the current tool wear data as an input. The results of this model were validated with the experimental results. The estimated results were well consistent with the results obtained from the experiments

An Effective Method for Milling Tool Condition Monitoring Using On-machine Measurement

Smart machining technology is now under intensive research worldwide. As a kernel technique of smart machining, on-machine measurement (OMM) technology can automatically measure tool diameter and length with laser tool setters on machine so that the machine controller compensates for the tool wear while machining, which can improve part accuracy without manual tool measurement on tool pre-setters. However, there is a dilemma that the OMM technique cannot predict tool failure so that the operator can replace tools before it fails. To address this problem, this research proposes a new approach to predict failure of round-insert face mill in rough and finish machining to automatically change tools right before their failure. First, the geometric equation of flank wear land width of round-insert face mill is formulated; second, after a tool diameter is measured, the flank wear width is calculated. Third, an experimental method is proposed to determine the tool radius reduction threshold and the tool location of measurement, and then the tool failure can be predicted in rough machining. Then, a new method is established to determine the criteria of tool radius reduction in finish machining according to the machined surface roughness. Finally, several experiments are conducted to verify this approach, and it is applied to a practical example. This approach can be directly applied in industry, and it can advance the smart machining technology

Gestión escolar y la práctica docente en la Institución Educativa N° 400 Virgen del Rosario, Huaral, 2020

La investigación tuvo como objetivo determinar la relación entre la gestión escolar y la práctica docente en la institución educativa N 400 Virgen del Rosario, Huaral, 2020. Estuvo regida bajo el enfoque cuantitativo, diseño no experimental correlacional, transversal. La muestra empleada fue de 72 docentes, con instrumentos validados por expertos y una alta fiabilidad. Los resultados nos indicaron la existente de una correlación alta entre las variables gestión escolar y práctica docente con un Rho de Spearman de ,618** y una significación bilateral de ,000