Tool–chip thermal conductance coefficient and heat flux in machining : Theory, model and experiment

This study proposes a technique for determining a tool–chip thermal conductance coefficient and heat flux in machining. The technique is based on solving an inverse heat transfer problem (IHTP). Because the IHTP is ill-posed, a priori information is required for its effective solution. To derive this information, substantial qualitative and quantitative analysis of a mixed boundary value problem for the heat equation and an illustrative test case for IHTP are provided. It has been established that the averaged interfacial chip temperature is needed for an effective IHTP solution. Thermal imaging combined with a special experimental setup was used to determine chip temperature. It was also found that a function describing the heat flux time dependency belongs to a set of decreasing functions. Tool–chip thermal conductance coefficients were obtained for high-speed steel and cemented carbide tooling. On the microscale, this data was interpreted in terms of a conforming rough surface contact conductance model, where tool wear was found to govern variations in the thermal conductance coefficient

SEM Investigation of ZnO and CdO–ZnO Layers Grown by Sol-Gel Technology and a Multifractal Analysis of their Surface Depending on Synthesis Conditions

Introduction. Super-thin films of zinc oxide regarded as transparent electrodes can be integrated in effective semiconductor heterostructures for use in modern infrared photo electronics and solar power installations. The most important parameter of zinc oxide thin layers is their surface nanorelief, which can be effectively studied using SEM spectroscopy. SEM images allow for a quantitative description of the surface depending on the synthesis conditions using the method of multifractal analysis. Such an approach reveals quantitative relationships between the fractal parameters of the surface topography of the layers in these systems and the temperature regimes used for their final annealing in conventional sol-gel technology.Aim. To reveal quantitative relationships between the fractal parameters of the surface topography of layers in the Zn–O & Zn–Cd–O systems and the temperature conditions of their final annealing. The MFA method was used for a quantitative description of the surface state depending on the synthesis conditions.Materials and methods. Super-thin films in the ZnO and ZnO–CdO systems were synthesized using a modified sol-gel technology. The temperature-concentration ranges of the parameters of the modified technological process, which allows high-quality layers of the material to be reproducibly obtained on a glass substrate, were determined. The surface morphology was investigated by SEM spectroscopy depending on the temperature of the final annealing of the layers. SEM images of the surface served as a basis for multifractal analysis (MFA) of the surface area and volume of nanoforms, which are formed on the surface of the obtained layers thus determining their surface relief.Results. Renyi’s numbers and the parameters of fractal ordering in MFA were chosen as fractal parameters for describing the nano-geometry of the layer surface. MFA was applied to the description of both the surface areas and volumes of nanoforms. Quantitative correlations between Renyi’s numbers, as well as the parameters of fractal ordering for the areas and volumes of surface nanoforms, and the temperature of the final annealing were found.Conclusion. The numerical values of Renyi’s numbers for the surface and volume characteristics of the surface of layers were used to assess the effect of the fractality of the surface on the molar surface energy of the film. Consideration of the fractal geometry of nanoforms with their characteristic sizes smaller than 5·103μm shows the possibility of both an increase in the surface energy of the resulting film and its decrease when changing the characteristic sizes of nanoforms. The latter effect is due to the formation of a highly porous surface at the nano levelIntroduction. Super-thin films of zinc oxide regarded as transparent electrodes can be integrated in effective semiconductor heterostructures for use in modern infrared photo electronics and solar power installations. The most important parameter of zinc oxide thin layers is their surface nanorelief, which can be effectively studied using SEM spectroscopy. SEM images allow for a quantitative description of the surface depending on the synthesis conditions using the method of multifractal analysis. Such an approach reveals quantitative relationships between the fractal parameters of the surface topography of the layers in these systems and the temperature regimes used for their final annealing in conventional sol-gel technology.Aim. To reveal quantitative relationships between the fractal parameters of the surface topography of layers in the Zn–O & Zn–Cd–O systems and the temperature conditions of their final annealing. The MFA method was used for a quantitative description of the surface state depending on the synthesis conditions.Materials and methods. Super-thin films in the ZnO and ZnO–CdO systems were synthesized using a modified sol-gel technology. The temperature-concentration ranges of the parameters of the modified technological process, which allows high-quality layers of the material to be reproducibly obtained on a glass substrate, were determined. The surface morphology was investigated by SEM spectroscopy depending on the temperature of the final annealing of the layers. SEM images of the surface served as a basis for multifractal analysis (MFA) of the surface area and volume of nanoforms, which are formed on the surface of the obtained layers thus determining their surface relief.Results. Renyi’s numbers and the parameters of fractal ordering in MFA were chosen as fractal parameters for describing the nano-geometry of the layer surface. MFA was applied to the description of both the surface areas and volumes of nanoforms. Quantitative correlations between Renyi’s numbers, as well as the parameters of fractal ordering for the areas and volumes of surface nanoforms, and the temperature of the final annealing were found.Conclusion. The numerical values of Renyi’s numbers for the surface and volume characteristics of the surface of layers were used to assess the effect of the fractality of the surface on the molar surface energy of the film. Consideration of the fractal geometry of nanoforms with their characteristic sizes smaller than 5·103μm shows the possibility of both an increase in the surface energy of the resulting film and its decrease when changing the characteristic sizes of nanoforms. The latter effect is due to the formation of a highly porous surface at the nano leve

Influence of tool material and tool wear on tool temperature in hard turning reconstructed via inverse problem solution

In this work the cutting tool temperature distribution that develops during turning of hardened cold-work tool steel is modeled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes were computed. The temperature distribution was modeled for the case of new tools, as well as for the case of its development in the course of a tool wear. The reconstructed temperature distributions were in good agreement with the measured data. The heat flux through rake face was found to be reducing with the decrease of thermal conductivity of the tool material.Отримано розподіл температури різального інструменту при точінні загартованої холодно-штампованої сталі інструменту моделюванням на основі експериментальних даних. Дані, що отримано для ряду термопар, розміщених безпосередньо на пластині з ПКНБ, всередині підкладки і в державці, було використано в якості вхідних даних для моделі. Теплові потоки при різанні було отримано розв’язанням оберненої задачі. Розподіл температури в різці було отримано як для випадку нового інструменту, так і для випадку розвитку зносу інструменту в процесі зносу. Отримані розподіли температури добре узгоджуються з виміряними даними. Було виявлено, що тепловий потік через передню поверхню інструменту зменшується при зниженні теплопровідності матеріалу інструменту.Получено распределение температуры режущего инструмента при точении закаленной холодно-штамповой стали моделированием на основе экспериментальных данных. Данные, полученные для ряда термопар, расположенных непосредственно на пластине из ПКНБ, внутри подложки и в державке, были использованы в качестве входных данных для модели. Тепловые потоки при резании были получены решением обратной задачи. Распределение температуры в резце было получено как для случая нового инструмента, так и для случая развития износа инструмента в процессе резания. Полученные распределения температур хорошо согласуются с измеренными данными. Было обнаружено, что тепловой поток через переднюю поверхность инструмента уменьшается при снижении теплопроводности материала инструмента

Experimental study and modeling of the heat flux acting on the tool flank when machining

Adequate setting of the boundary conditions for the heat equation when modeling the temperature distribution in the cutting tool is one of the key points. The boundary conditions on the tool surfaces can be divided into two groups: conditions that describe heat losses (heat exchange with the environment) and conditions that characterize the heat source that heats up the tool (heat flux from the cutting zone). Additional complexity in modeling is provided by the fact that during cutting the surface on which the heat source acts changes, for example, due to wear on the flank surface. In this paper, a method is proposed for measuring the power of a heat source acting on the flank surface. The hardware of the method includes a sensor equipped tool and specially manufactured inserts that imitate the geometry of worn flank surface. In turn, the software is based on the method of solving the inverse heat conduction problem in metal cutting, which allows restoring the heat flux flowing into the tool by measuring temperature with sensors installed in the toolholder. The experimental plan included inserts with negative and positive rake, different cutting speeds (190, 235, 280 m/min), and feeds (0.15, 0.3, 0.45 mm/rev)

Computational and Experimental Inverse Problem Approach for Determination of Time Dependency of Heat Flux in Metal Cutting

This study develops the method for solution of inverse heat conduction problem applied to metal cutting. The proposed method operates with a selection procedure involving iterative solutions of heat forward problem. In such formulation, it allows avoiding difficulties associated with ill-posed inverse problems inherent to conventional formulations. Inverse heat problem was transformed into constrained optimization problem via objective function which metrizes the difference between FE and experimental data. Specially designed solid HSS cutting tool with embedded thermocouples was manufactured. The method was validated for the case of orthogonal machining of 6061 aluminum alloy. The numerical simulations were performed with the help of COMSOL Multiphysics and MATLAB scripts. Heat flux exhibits descending trend over the time of the cutting test and closely follows hyperbola function behavior with the average value of q = 4.6 MW/m2

Machine Learning based Approach for the Prediction of Surface Integrity in Machining

This paper presents a two-stage procedure to create a surface integrity predictor. The first stage includes data clustering, which allows to evaluate the achievable surface quality. The second stage consists in training the model to predict which cluster the machined surface will belong to. To demonstrate the applicability, an experimental plan for machining of Inconel 718 in milling was developed. The validation through confusion matrix showed that the accuracy of prediction ranged from 64.7% to 84.9% for different test and train sets. Prospect of the research is to expand the set of monitored machining parameters and controlled surface integrity parameters

Heat flux in metal cutting : Experiment, model, and comparative analysis

In this paper, a proof of time-dependent behavior of heat flux into a cutting tool is built. Its implementation calls for a new method for estimating heat flux, which was developed using an inverse problem technique. A special experimental setup was designed and manufactured to implement the method. A series of dry machining experiments were conducted with high speed steel and cemented carbide tooling. A two-stage procedure was developed to overcome the ill-posedness of the inverse heat conduction problem by transforming it into a well-posed parameter estimation problem. The first stage retrieves the value of the heat flux and specific tool heating energy Et. The second stage parametrizes and compares predefined heat flux behaviors. It was found that the time dependency of heat flux is best described by a decreasing power function

Оптимізація режимів розвантаження стиснутого природного газу транспортованого суднами-контейнеровозами

The aim of the study is to calculate the parameters of the movable pipeline ship unloading as a part of the cargo plan of a CNG ship, to develop a technological scheme of the pipeline strapping of the containers system, to develop an unloading scheme of a CNG ship under the conditions of the different schemes of mooring, to calculate the parameters of the gas flow during the unloading process. The scientific novelty of the work is to substantiate the technological strapping of the container blocks in order to make loading/unloading of the CNG vehicle uniform, to determine the required performance of unloading points and to ensure the unloading duration up to 12 hours. According to the research there is offered the unloading scheme of the CNG vehicle under the conditions of the bow mooring to the port facilities and the presence of the bow and stern containers blocks connections to the pipeline communications. There are offered two concurrent unloading points with the maximum unloading capacity of 150 kg/s. The further layout of the turbo expander and compressor equipment should result from the offered parameters scheme. It is proved that the offered pipeline communication scheme provides with the uniform ship unloading (pressure difference in individual containers blocks (0,5-0,7 bar), however, there is a significant uniform (up to -30°C) temperature lowering of the gas due to physical processes of the gas throttling in CNG cylinders. During further research studies it should be considered the impact of the temperature lowering on the mechanical properties of the CNG cylinders composite material. Generally, the offered unloading scheme will allow ship unloading in the economically reasonable period of 12 hours. The results should be used for further development of the technological scheme of ground equipment for connecting of a CNG vehicle, for choosing the technological equipment, assessing the gas flow parameters influence on the mechanical properties of the pipes metal and the composite material

Influence of tool material and tool wear on tool temperature in hard turning reconstructed via inverse problem solution

In this work the cutting tool temperature distribution that develops during turning of hardened cold-work tool steel is modeled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes were computed. The temperature distribution was modeled for the case of new tools, as well as for the case of its development in the course of a tool wear. The reconstructed temperature distributions were in good agreement with the measured data. The heat flux through rake face was found to be reducing with the decrease of thermal conductivity of the tool material

Modelling and Experimental Investigation of Cutting Temperature when Rough Turning Hardened Tool Steel with PCBN Tools

In this study the cutting tool temperature that develops during rough turning of hardened cold-work tool steel is modelled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes and heat transfer coefficients were computed and where the developed temperature field was reconstructed from the experimental readings. The temperature was modelled for the case of new tools, as well as for the case of its development in the course of tool wear. The machining case involved utilization of a high-cBN content and a binderless PCBN grade, both possessing high thermal conductivity of 110 and 190 W/m K respectively. (C) 2015 The Authors. Published by Elsevier B.V