Optimal replacement of tool during turning titanium metal matrix composites (original) (raw)
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Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2015
Little practical results are known about the cutting tool optimal replacement time, specifically for machining of composite materials. Due to the fact that tool failure represents about 20% of machine down-time, and due to the high cost of machining, in particular when the work piece's material is very expensive, optimization of tool replacement time is thus fundamental. Finding the optimal replacement time has also positive impact on product quality in terms of dimensions and surface finish. In this article, two new contributions to research on tool replacement are introduced. First, tool replacement mathematical models are proposed. These models are used in order to find the optimal time to tool replacement when the tool is used under variable machining conditions, namely, the cutting speed and the feed rate. Proportional hazards models are used to find an optimal replacement function. Second, this model is obtained during turning titanium metal matrix composites. These composites are a new generation of materials which have proven to be viable in various industrial fields such as biomedical and aerospace, and they are very expensive. Experimental data are obtained and used in order to develop and to validate the proportional hazards models, which are then used to find the optimal replacement conditions.
Metal matrix composites (MMCs), as a new generation of materials; have proven to be viable materials in various industrial fields such as biomedical and aerospace. In order to achieve a valuable modification in various properties of materials, metallic matrices are reinforced with additional phases based on the chemical and/or physical properties required in the in-service operating conditions. The presence of the reinforcements in MMCs improves the physical, mechanical and thermal properties of the composite; however it induces significant issues in the domain of machining, such as high tool wear and inferior surface finish. The interaction between the tool and abrasive hard reinforcing particles induces complex deformation behaviour in the MMC structure. Sever tool wear is technically the most important drawback of machining MMCs.
Procedia CIRP, 2014
Metal matrix composites (MMCs), as a new generation of materials; have proven to be viable materials in various industrial fields such as biomedical and aerospace. In order to achieve a valuable modification in various properties of materials, metallic matrices are reinforced with additional phases based on the chemical and/or physical properties required in the in-service operating conditions. The presence of the reinforcements in MMCs improves the physical, mechanical and thermal properties of the composite; however it induces significant issues in the domain of machining, such as high tool wear and inferior surface finish. The interaction between the tool and abrasive hard reinforcing particles induces complex deformation behaviour in the MMC structure. Sever tool wear is technically the most important drawback of machining MMCs.
Procedia CIRP, 2013
The Outstanding characteristics of titanium metal matrix composites (Ti-MMCs) have brought them up as promising materials in different industries, such as aerospace and biomedical. They exhibit high mechanical and physical properties, in addition to their low weight, high stiffness and high wear resistance. The presence of the ceramic reinforcements in a metallic matrix further contributes to these preferable properties. However, the high abrasive nature of the ceramic particles limits greatly the machinability of this class of material, as they induce significant tool wear and poor surface finish. In this study an attempt is made to find the optimum cutting conditions in terms of minimizing the tool wear and surface roughness during machining Ti-MMCs. Meta-modeling optimization in performed to achieve the goal. In this study the three independent parameters under consideration are the cutting speed, feed rate and the depth of cut. The response parameters are the surface roughness and the tool wear rate. The independent parameters are divided into a set of levels at which the experiments are conducted. At each experimental condition the two response parameters are measured. Kriging meta-modeling technique is used to fit a model to the response parameters in the multi-dimensional space. These models are used, in turn, within a multi-objective optimization algorithm to find the optimum cutting condition space. The above-mentioned algorithm is based on an evolutionary multi-objective search technique known as SPEA (Strength Pareto Evolutionary Algorithm).
Identifying Optimal Intervene Hazard for Cutting Tools Considering Cost-availability Optimization
—In this paper, the optimal intervene hazard and their associated optimal tool replacement times were found considering three models of optimization, namely cost optimization, availability optimization, and cost-availability optimization. The cost-availability optimization was done by taking into consideration replacement costs, replacement times and costs of downtimes. Experimental data was collected during turning titanium metal matrix composites (TiMMCs). In the surface finishing process, cutting tool is used under low constant cutting speed, small constant depth of cut, and changeable feed rate. The Proportional Hazards Model (PHM) is used to model the tool's reliability and hazard functions using EXAKT software. The experimental results are used to construct, and then validate, the PHM model.
Metals
Metal-matrix composites (MMCs) are made of non-metallic reinforcements in metal matrixes, which have excellent hardness, corrosion, and wear resistance. They are also lightweight and may pose a higher strength-to-weight ratio as compared to commercial titanium alloys. One of the MMCs with remarkable mechanical properties are titanium metal matrix composites (Ti-MMCs), which are considered a replacement for super-alloys in many industrial products and industries. Limited machining and machinability studies of Ti-MMCs were reported under different cutting and lubrication conditions. Tool wear morphology and life are among the main machinability attributes with limited attention. Therefore, this study presents the effects of cutting and lubrication conditions on wear morphology in carbide inserts when turning Ti-MMCs. To that end, maximum flank wear (VB) and cutting forces were recorded, and the wear morphologies within the initial period of the cut, as well as the worn condition, were...
Tool wear characterization in high-speed milling of titanium metal matrix composites
The International Journal of Advanced Manufacturing Technology, 2018
Titanium metal matrix composites (Ti-MMCs) have been successfully incorporated into a vast number of products within various industrial sectors. Despite excellent mechanical and physical features, due to the presence of hard and abrasive ceramic particles in metal matrices of Ti-MMCs, various issues have been emerged regarding machining and machinability of Ti-MMCs. Among critical machinability attributes, tool/insert wear and surface quality, in principle average surface roughness, R a , are the principal critical attributes. This study plans to present an experimental analysis of wear characterization of polycrystalline diamond (PCD) and carbide inserts during high-speed milling of Ti-MMCs. The main wear modes observed were adhesion, abrasion, and diffusion. Oxidation was also observed at under those cutting conditions with elevated temperature. Regardless of the insert used, edge chipping was also observed in milling tests under various levels of cutting. It was observed that cutting speed and depth of cut are the major cutting parameters affecting wear rate in carbide X500 and PCD inserts. Meanwhile, surface roughness R a was not affected by the cutting parameters used when using PCD insert. Promising tool wear rates also were recorded under low levels of cutting speed and high levels of feed rate when using carbide insert X500.
Determining optimal replacement time for metal cutting tools
European Journal of Operational Research, 2010
Traditional tool life models do not take into account the variation inherent in metal cutting processes. As a consequence, the real tool life rarely matches the predicted values. To compensate for this uncertainty, tools are usually replaced prematurely, which leads to unnecessarily high tool costs. In some cases, however, wear-out occurs earlier than predicted, which imposes a risk of workpiece damage or rework and can lead to other extra charges. To balance these costs, this paper proposes an age replacement model. It is assumed that penalty costs are incurred each time a tool fails before the planned replacement. The probability of such an event is determined from the tool reliability function, which models the wear-out by a mixture of Weibull distributions, while failures due to external stresses are accounted for by a homogeneous Poisson process. The optimal replacement time is then determined from a total time on test (TTT) plot. The adequacy of the proposed approach for practical application is tested and confirmed in a case study on turning of Inconel 718 with cubic boron nitride (CBN) N) tools.