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

2021 ◽  
Vol 23 (3) ◽  
pp. 47-54
Author(s):  
A.F. Denisenko ◽  
◽  
L.Yu. Girth ◽  
Keyword(s):  
Thermal Resistance ◽  
Regression Model ◽  
Metal Cutting ◽  
Operating Experience ◽  
Design Stage ◽  
Contact Thermal Resistance ◽  
Limit Values ◽  
Cutting Equipment ◽  
Processing Accuracy ◽  
The Difference

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.

scholarly journals Simulation of a Contact Pseudo-Environment in Calculating Thermal Resistance

2021 ◽  
Vol 346 ◽  
pp. 03049
Author(s):  
Alexander Denisenko ◽  
Roman Grishin ◽  
Liubov Podkruglyak
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Numerical Modeling ◽  
Thermal Resistance ◽  
Contact Zone ◽  
Metal Cutting ◽  
The Finite Element Method ◽  
Contact Thermal Resistance ◽  
Temperature Criterion ◽  
The Ideal

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.

IMPROVING THE EFFICIENCY OF FINISHING MILLING OF CONCAVE SURFACES ON SMALL-SIZED CNC MACHINES

2021 ◽  
pp. 92-97
Author(s):  
А.М. Козлов ◽  
Г.Е. Малютин ◽  
Е.А. Малявин ◽  
А.А. Козлов
Keyword(s):  
Metal Cutting ◽  
Low Cost ◽  
Cutting Depth ◽  
Ferrous Metals ◽  
Cutting Equipment ◽  
Processing Accuracy ◽  
Increase Productivity ◽  
Spatial Shape ◽  
Cad Tool ◽  
Cutting Modes

Pазвитие систем ЧПУ современного полногабаритного металлорежущего оборудования дало возможность корректировать режимы резания, например, величину рабочей подачи непосредственно в процессе обработки. Однако на производстве имеется значительная часть деталей, которые по своим габаритам экономически невыгодно обрабатывать на дорогостоящих крупных станках, имеющих мощную систему ЧПУ. Поэтому на предприятиях все большее применение получают относительно недорогие малогабаритные металлорежущие станки. Технологические возможности такого оборудования позволяют обрабатывать не только цветные металлы и сплавы, но и стали. Особенностью управления таким оборудованием является использование упрощенных систем ЧПУ, установленных на персональных компьютерах, которые не имеют возможности выполнять арифметические операции, и это становится препятствием для повышения производительности обработки сложных поверхностей. В то же время из-за своей простоты и низкой стоимости эти системы становятся все более востребованными. Предлагается повысить производительность обработки поверхностей сложной пространственной формы на основе расчета движения инструмента САПР системой путем преобразования реальной траектории в набор симметричных отрезков с известными координатами. Этот метод позволяет при заданной точности обработки установить значения параметров режима резания, близкие к оптимальным, исключить аварийные ситуации, связанные с выходом из строя инструмента при работе с переменной глубиной резания, сформированной после черновой обработки, и повысить производительность на 15-20% The development of CNC systems of modern full-sized metal-cutting equipment made it possible to adjust cutting modes, for example, the value of the working feed, directly during processing. However, there is a significant number of the parts in production that, according to their dimensions, are economically unprofitable to process on expensive large machines with a powerful CNC system. Therefore, relatively inexpensive small-sized metal-cutting machines are becoming increasingly used in enterprises. The technological capabilities of such equipment allow processing not only non-ferrous metals and alloys but also steels. A feature of the control of such equipment is the use of simplified CNC systems installed on personal computers that are not able to perform arithmetic operations and this becomes an obstacle to improving the productivity of processing complex surfaces. At the same time, due to their simplicity and low cost, these systems are becoming more and more popular. In the article, we proposed to increase the productivity of processing surfaces of complex spatial shape on such machines based on the calculation of the CAD tool movement by the system by converting the real trajectory into a set of symmetrical segments with known coordinates. This method allows you, with a given processing accuracy, to set the values of the cutting mode parameters close to the optimal ones, to eliminate emergencies associated with tool failure when working with a variable cutting depth formed after roughing and to increase productivity by 15-20%

Derivation of Design Guidelines for Miniature Machine Tools

2004 ◽  
Author(s):  
Nozomu Mishima
Keyword(s):  
Machine Tools ◽  
Metal Cutting ◽  
Evaluation Method ◽  
Design Guidelines ◽  
Design Tool ◽  
Design Stage ◽  
Local Error ◽  
Early Design Stage ◽  
The Difference ◽  
Micro Machine

As has been demonstrated the “microfactory”, which is a miniature manufacturing system proposed by the author and his research group, small machine tools that are comparable in size to their target products lead to large reductions in energy consumption and occupied space. They also increase the flexibility of system reconfiguration because of their low weight and small size. Although it had been thought that micro machine tools might not have sufficient metal cutting capability, experiments showed that were capable of micro mechanical fabrication. However, the design of miniature machine tools has not been fully optimized. For example, the design target of the first prototype, a performable miniature machine (“Micro lathe”), was to make the overall size as small as possible. The author proposed a design evaluation method to roughly estimate machine tool performances during its early design stage. In this paper, the above-mentioned design tool is applied to find suitable miniaturizing strategies. By applying the design tool to the miniaturization of machine tools, it is possible to determine which of the design candidates have the best theoretical performance and which of the local error factors would significantly affect machine performance. From the results of calculation, the tool can clarify the difference of effect of error sources on performances between normal machine tools and miniature machine tools. This leads to some suggestions regarding structures, sizes and suitable machine components. Design guidelines for miniature machine tools can be obtained from the information.

Experimental Investigation into Driver Behavior along Curved and Parallel Diverging Terminals of Exit Interchange Ramps

2021 ◽  
pp. 036119812199742
Author(s):  
Alberto Portera ◽  
Marco Bassani
Keyword(s):  
Design Stage ◽  
Lane Change ◽  
Age And Gender ◽  
Traffic Conditions ◽  
Current Design ◽  
The Difference ◽  
Safety Countermeasures ◽  
And Gender ◽  
Set Up ◽  
Curve Radius

Current design manuals provide guidance on how to design exit ramps to facilitate driving operations and minimize the incidence of crashes. They also suggest that interchanges should be built along straight roadway sections. These criteria may prove ineffective in situations where there is no alternative to terminals being located along curved motorway segments. The paper investigates driving behavior along parallel deceleration curved terminals, with attention paid to the difference in impact between terminals having a curvature which is the same sign as the motorway segment (i.e., continue design), and those having an opposite curvature (i.e., reverse design). A driving simulation study was set up to collect longitudinal and transversal driver behavioral data in response to experimental factor variations. Forty-eight drivers were stratified on the basis of age and gender, and asked to drive along three randomly assigned circuits with off-ramps obtained by combining experimental factors such as motorway mainline curve radius (2 values), terminal length (3), curve direction (2), and traffic conditions (2). The motorway radius was found to be significant for drivers’ preferred speed when approaching the terminal. Terminal length and traffic volume do not have a significant impact on either longitudinal or transversal driver outputs. However, the effect of curve direction was found to be significant, notably for reverse terminals which do not compel drivers to select appropriate speeds and lane change positions. This terminal type can give rise to critical driving situations that should be considered at the design stage to facilitate the adoption of appropriate safety countermeasures.

scholarly journals The inverse coefficient problem of heat transfer in layered nanostructures

2017 ◽  
Vol 20 (3) ◽  
pp. 213-219
Author(s):  
K. K. Abgarian ◽  
R. G. Noskov ◽  
D. L. Reviznikov
Keyword(s):  
Heat Transfer ◽  
Inverse Problem ◽  
Thermal Resistance ◽  
Transfer Problem ◽  
Dominant Role ◽  
Rapid Development ◽  
Problem Solution ◽  
Microwave Range ◽  
Contact Thermal Resistance ◽  
Resistance Coefficients

The rapid development of electronics leads to the creation and use of electronic components of small dimensions, including nanoelements of complex, layered structure. The search for effective methods for cooling electronic systems dictates the need for the development of methods for the numerical analysis of heat transfer in nanostructures. A characteristic feature of energy transfer in such systems is the dominant role of contact thermal resistance at interlayer interfaces. Since the contact resistance depends on a number of factors associated with the technology of heterostructures manufacturing, it is of great importance to determine the corresponding coefficients from the results of temperature measurements.The purpose of this paper is to evaluate the possibility of reconstructing the thermal resistance coefficients at the interfaces between layers by solving the inverse problem of heat transfer.The complex of algorithms includes two major blocks — a block for solving the direct heat transfer problem in a layered nanostructure and an optimization block for solving the inverse problem. The direct problem was formulated in an algebraic (finite difference) form under the assumption of a constant temperature within each layer, which is due to the small thickness of the layers. The inverse problem was solved in the extreme formulation, the optimization was carried out using zero-order methods that do not require the calculation of the derivatives of the optimized function. As a basic optimization algorithm, the Nelder—Mead method was used in combination with random restarts to search for a global minimum.The results of the identification of the contact thermal resistance coefficients obtained in the framework of a quasi-real experiment are presented. The accuracy of the identification problem solution is estimated as a function of the number of layers in the heterostructure and the «measurements» error.The obtained results are planned to be used in the new technique of multiscale modeling of thermal regimes of the electronic component base of the microwave range, when identifying the coefficients of thermal conductivity of heterostructure.

scholarly journals Contact thermal resistance of capillary structures of heat pipes in heat-exchange systems of spacecrafts and helioenergetics

2009 ◽  
Vol 15 (1) ◽  
pp. 75-79
Author(s):  
A.G. Kostornov ◽  
◽  
A.A. Shapoval ◽  
G.A. Frolov ◽  
I.V. Shapoval ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Thermal Resistance ◽  
Heat Pipes ◽  
Contact Thermal Resistance

The Effect of Prior Cutting Conditions on the Shear Mechanics of Orthogonal Machining

1998 ◽  
Vol 120 (1) ◽  
pp. 13-20 ◽  
Author(s):  
R. Stevenson ◽  
D. A. Stephenson
Keyword(s):  
Material Properties ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Rake Angle ◽  
Cnc Machining ◽  
Machining Process ◽  
Depth Of Cut ◽  
Prior History ◽  
Machining Conditions ◽  
The Difference

It has been proposed several times in the metal-cutting literature that the machining process is non-unique and that the instantaneous machining conditions depend on the prior machining conditions (e.g. depth of cut, rake angle etc.). To evaluate the validity of this concept, a series of experiments was conducted using a highly accurate CNC machining center. For these experiments, the machining conditions were changed during the course of an orthogonal cutting experiment in a repeatable manner and the measured forces compared as a function of prior history. Tests were conducted on several tempers of 1100 aluminum and commercial purity zinc to evaluate the effect of material properties on the machining response. It was found that the change in measured cutting forces which could be ascribed to prior machining history was less than 3 percent and that material properties, particularly work hardening response, had no discernible effect on the magnitude of the difference.

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