FUNDAMENTALLY NEW APPROACHES TO SOLVING THERMOPHYSICAL PROBLEMS IN THE FIELD OF NANOELECTRONICS

The paper discusses current problems related to the heat transfer in solid-state nanostructures: the influence of real rough boundaries on the effective thermal conductivity and contact thermal resistance

An Improved Thermal Performance Modeling for High-speed Spindle of Machine Tool Based on Thermal Contact Resistance Analysis

The distribution of the temperature field has a great influence on structural performance, thermal deformation, thermal error compensation. To improve the prediction accuracy of the temperature distribution of the spindle system, a comprehensive model considering the contact thermal resistance (TCR) of the interfaces was established to analyze the thermal performance of high-speed spindle system in the present work. An elastoplastic contact model was used to calculate the contacting areas and loads of interfaces, which were employed to establish the contact thermal resistance model of the main interfaces of spindle, such as bearing rings and tool holders. Basing on the TCR parameters, a Finite Element Analysis (FEA) model was proposed to analyze the temperature distribution of the spindle system. And a temperature test experiment was set up to verify the accuracy of the FEA model. The results show that the relative error of representative test points was all less than 5%, which means the established model can appropriately reflect the temperature field distribution of the spindle.

HEAT EXCHANGE IN THE AREA OF SURFACE CONTACT WITH SHAPE DEVIATIONS

The article discusses a thermal model of the heat transfer process in a composite system with contacting metal surfaces with macrodeviations in the form of bulges. It is shown that the previously developed methods for calculating contact thermal resistances are suitable only for contact pairs with flat-rough surfaces. For the considered contact pairs, when deriving analytical dependences, it is necessary to take into account the effect of equivalent non-flatness, the presence of which significantly increases the contact thermal resistance, which requires taking into account the influence of deviations in the shape of the contact surfaces in the process of designing heat-stressed systems.

Simulation of a Contact Pseudo-Environment in Calculating Thermal Resistance

The use of the temperature criterion in the design of metal-cutting machines, determined on the basis of models that take into account the contact thermal resistances, is an objective necessity. These models should take into account to the maximum extent the actual conditions of contact of parts in the design under consideration, determined by the deviations of the mating surfaces from the ideal shape. The article presents the results of numerical modeling based on the finite element method of the formation of the contact thermal resistance and the evaluation of the influence of the parameters of the intermediate layer (pseudo-environment) that occurs in the contact zone of surfaces with macro-deviations on the passage of the heat flow. The obtained results allowed us to identify the most significant of the considered parameters. It is established that when modeling a pseudo-environment, it is necessary to take into account the coefficient of its thermal conductivity, the size, location and integrity of the actual contact zone.

CONSTRUCTION OF A REGRESSION MODEL OF THERMAL RESISTANCE OF A CONTACT PSEUDO MEDIUM

The operating experience of metal-cutting machines made it possible to develop reasonable recommendations for the permissible limit values of temperature for the main subsystems of the machine, which determine the accuracy of processing. However, the decrease in the seriality of the manufactured metal-cutting equipment and the constant improvement of its designs require the development of models that are the basis of engineering techniques that allow at the design stage to predict the thermal picture of the main machine units that affect the processing accuracy. In connection with a significant number of factors influencing the formation of contact thermal resistance, and the difference in the weight of their action, it is proposed to use a pseudolayer (pseudo-medium), consisting of areas of actual contact and cavities filled with air or oil, for their comprehensive consideration in the thermal model of joining parts. To determine the significant factors that dominate the contact thermal resistance, a number of one-factor experiments were carried out. To develop a regression model of temperature change in the contact zone, a PFE of type 24 was performed. The results obtained were verified by the Cochran, Student and Fisher criteria.