scholarly journals Analytical method of calculation of thermal fields of cast parts during crystallization

2021 ◽  
Vol 1,2021 (1,2021(126)) ◽  
pp. 5-13
Author(s):  
Liutyi Rostislav
Keyword(s):  
Mathematical Method ◽  
Thermal Field ◽  
Complex Method ◽  
Cylindrical Shape ◽  
Mathematical Basis ◽  
Method Of Calculation ◽  
Thermal Fields ◽  
Analytical Formulas ◽  
Molding Materials ◽  
Cast Parts

The aim of the work is to create a mathematical method that allows to calculate the distribution of thermal fields in cast parts during crystallization using a system of analytical formulas. During the calculations, a combination of known analytical formulas GF was used. Balandin, AY Weinik, S. Schwartz with their own original mathematical solutions created on the basis of the analysis of thermophysical processes in castings in the process of their crystallization. Computer simulation of thermal fields using the LVMFlow program was used to compare the results. According to the created mathematical method, examples of calculation of thermal fields for two castings made of steel 25L of hollow cylindrical shape, the wall thickness of which is 100 mm and 4 mm, respectively, are given. Calculations were performed for the conditions of crystallization of castings in a single sand form. The comparison of results of calculations by the developed method and with use of the existing software is presented. For the first time, based on our own mathematical and thermophysical developments, a comprehensive calculation method for determining the thermal field of the casting during crystallization and cooling was developed. casting. The technique is expressed in a number of analytical formulas, each of which describes a specific thermal process that occurs in the casting. This takes into account the features of the casting configuration. The created complex method of calculation of thermal fields of cast parts is a mathematical basis for determining the thermal fields of molds and rods, which allows to predict their properties and select the optimal molding materials. The created technique can also be offered as a mathematical basis for refining applied computer programs for foundry production. CASTING, TEMPERATURE, THERMAL FIELD, COOLING DYNAMICS, COOLING DURATION, MATHEMATICAL LAW, COLORING FRONT, CALCULATION

Prediction of Comprehensive Thermal Error of a Preloaded Ball Screw on a Gantry Milling Machine

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Kuo Liu ◽  
Haibo Liu ◽  
Te Li ◽  
Yongqing Wang ◽  
Mingjia Sun ◽  
...  
Keyword(s):  
Thermal Field ◽  
Thermal Characteristics ◽  
Thermal Error ◽  
Least Square Method ◽  
High Accuracy ◽  
Least Square ◽  
Ball Screw ◽  
Milling Machine ◽  
Thermal Fields ◽  
Proposed Model

The conception of the comprehensive thermal error of servo axes is given. Thermal characteristics of a preloaded ball screw on a gantry milling machine is investigated, and the error and temperature data are obtained. The comprehensive thermal error is divided into two parts: thermal expansion error ((TEE) in the stroke range) and thermal drift error ((TDE) of origin). The thermal mechanism and thermal error variation of preloaded ball screw are expounded. Based on the generation, conduction, and convection theory of heat, the thermal field models of screw caused by friction of screw-nut pairs and bearing blocks are derived. The prediction for TEE is presented based on thermal fields of multiheat sources. Besides, the factors influencing TDE are analyzed, and the model of TDE is established based on the least square method. The predicted thermal field of the screw is analyzed. The simulation and experimental results indicate that high accuracy stability can be obtained using the proposed model. Moreover, high accuracy stability can still be achieved even if the moving state of servo axis changes randomly, the screw is preloaded, and the thermal deformation process is complex. Strong robustness of the model is verified.

scholarly journals Analytical Design of the Human Bronchial Tree for Healthy Patients and Patients with Obstructive Pulmonary Diseases

2019 ◽  
Vol 14 (2) ◽  
pp. 635-648 ◽  
Author(s):  
A.E. Medvedev ◽  
P.S. Gafurova
Keyword(s):  
Airway Obstruction ◽  
Bronchial Tree ◽  
Pulmonary Diseases ◽  
Cylindrical Shape ◽  
Analytical Design ◽  
Geometric Characteristics ◽  
Analytical Formulas ◽  
Two Parameters ◽  
Pathological Case ◽  
Order Smoothness

The study is aimed at the analytical design of the full human bronchial tree for healthy patients and patients with obstructive pulmonary diseases. Analytical formulas for design of the full bronchial tree are derived. All surfaces of the bronchial tree are matched with the second-order smoothness (there are no acute angles or ribs). The geometric characteristics of the human bronchial tree in the pathological case are modeled by a “starry” shape of the inner structure of the bronchus; the pathology degree is defined by two parameters: bronchus constriction level and degree of distortion of the cylindrical shape of the bronchus. Closed analytical formulas allow the human bronchial tree of an arbitrary complexity (up to alveoli) to be designed; moreover, the parametric dependences make it possible to specify any desirable degree of airway obstruction.

Thermal Analysis of Solids at High Peclet Numbers Subjected to Moving Heat Sources

1999 ◽  
Vol 121 (1) ◽  
pp. 182-186 ◽  
Author(s):  
O. Manca ◽  
B. Morrone ◽  
S. Nardini
Keyword(s):  
Thermal Field ◽  
Three Dimensional ◽  
Heat Losses ◽  
Transfer Model ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Motion Direction ◽  
Thermal Fields ◽  
Diffusion Component ◽  
Conductive Thermal Field

A three-dimensional heat transfer model has been developed to obtain the conductive thermal field inside a brick-type solid under a moving heat source with different beam profiles. The problem in quasi-steady state has been approximated by neglecting the axial diffusion component; thus, for Peclet numbers greater than 5, the elliptic differential equation becomes a parabolic one along the motion direction. The dependence of the solution on the radiative and convective heat losses has been highlighted. Thermal fields are strongly dependent on different spot shapes and on the impinging jet; this situation allows control of the parameters involved in the technological process.

Nanoscale Continuous Directional Motion Driven by a Cyclic Thermal Field

2021 ◽  
pp. 1-19
Author(s):  
Yichang Chen ◽  
Jiantao Leng ◽  
Zhengrong Guo ◽  
Yingyan Zhang ◽  
Tienchong Chang
Keyword(s):  
Carbon Nanotube ◽  
Thermal Gradient ◽  
Thermal Field ◽  
Joint Actions ◽  
Thermal Fields ◽  
Heating Region ◽  
Directional Motion ◽  
Gradient Forces ◽  
Controllable Motion ◽  
Novel Devices

Abstract Directional motion plays a crucial role in various mechanical systems. Although mechanisms for nanoscale directional motion have been widely used in many aspects of nanotechnology, it remains a great challenge to generate continuous and controllable motion at the nanoscale. Herein we propose a nanoscale continuous directional motion in cyclic thermal fields by using a double-walled system which consists of an outer BN/C heterojunction nanotube and a concentric inner carbon nanotube (CNT). By manipulating the heating region of the outer BN/C heterojunction tube, the continuous motion of the inner CNT can be realized with ease. The inner CNT demonstrates three distinct movements due to the joint actions of the asymmetric thermal gradient forces and interlayer attraction forces caused by the presence of the outer BN/C heterojunction nanotube. The mechanism revealed in the present study may be useful in designing novel devices for energy conversion and directional transportation.

scholarly journals The Effects of Water Friction Loss Calculation on the Thermal Field of the Canned Motor

Processes ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 256 ◽  
Author(s):  
Yiping Lu ◽  
Azeem Mustafa ◽  
Mirza Abdullah Rehan ◽  
Samia Razzaq ◽  
Shoukat Ali ◽  
...  
Keyword(s):  
Thermal Field ◽  
Test Method ◽  
Friction Loss ◽  
Heat Sources ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Volume Method ◽  
Canned Motor ◽  
Separation Test

The thermal behavior of a canned motor also depends on the losses and the cooling capability, and these losses cause an increase in the temperature of the stator winding. This paper focuses on the modeling and simulation of the thermal fields of the large canned induction motor by different calculation methods of water friction loss. The values of water friction losses are set as heat sources in the corresponding clearance of water at different positions along the duct and are calculated by the analytical method, loss separation test method, and by assuming the values that may be larger than the experimental results and at zero. Based on Finite volume method (FVM), 3D turbulent flow and heat transfer equations of the canned motor are solve numerically to obtain the temperature distributions of different parts of the motor. The analysis results of water friction loss are compared with the measurements, obtained from the total losses using the loss separation method. The results show that the magnitude of water friction loss within various parts of the motor does not affect the position of peak temperature and the tendency of the temperature distribution of windings. This paper is highly significant for the design of cooling structures of electrical machines.

The Effect of Thermal Field on the Deposition of Fe-TiC on Carbon Steel Using Laser Cladding

2010 ◽  
Author(s):  
Masoud Alimardani ◽  
Ali Emamian ◽  
Amir Khajepour ◽  
Stephen F. Corbin
Keyword(s):  
Carbon Steel ◽  
Numerical Model ◽  
Laser Cladding ◽  
Thermal Field ◽  
Deposition Process ◽  
Time Dependent ◽  
Experimental Investigations ◽  
Thermal Fields ◽  
Temperature Distributions ◽  
Laser Cladding Process

In this paper, a numerical and experimental method is used to investigate the effect of thermal fields on the deposition of Fe-TiC using the laser cladding process. Since in laser cladding temperature distributions and consequent rapid cooling rates determine the microstructure and final physical properties of the deposited layers, a 3D time-dependent numerical model is used to simulate the cladding process parallel to experimental analysis. The numerical results are used to study the temperature distributions and their evolutions throughout the deposition process. The experimental and verified numerical outcomes are then employed to study the variations of the microstructures of the deposited material as well as correlation between the formed microstructures and temperature distributions across the deposition domain. The numerical and experimental investigations are conducted through the deposition of Fe-TiC on the substrate of AISI 1030 carbon steel using a 1.1 kW fiber laser. The experimental results confirm that by increasing the substrate temperature throughout the process the distribution of the TiC particles changes along with the deposited tracks and the TiC particles start forming clusters at the top of the clad.

The interference of thermal fields from line sources in grid turbulence

1984 ◽  
Vol 144 ◽  
pp. 363-387 ◽  
Author(s):  
Z. Warhaft
Keyword(s):  
Line Source ◽  
Cross Correlation ◽  
Thermal Field ◽  
Grid Turbulence ◽  
Inference Method ◽  
Thermal Fields ◽  
Downstream Distance ◽  
Scalar Variance ◽  
Rate Of Decay ◽  
Total Temperature

The interference of passive thermal fields produced by two (and more) line sources in decaying grid turbulence is studied by using the inference method described by Warhaft (1981) to determine the cross-correlation coefficient ρ between the temperature fluctuations produced by the sources. The evolution of ρ as a function of downstream distance, for 0.075 < d/l < 10, where d is the wire spacing and l is the integral lengthscale of the turbulence, is determined for a pair of sources located at various distances from the grid. It is found that ρ may be positive or negative (thereby enhancing or diminishing the total temperature variance) depending on the line-source spacing, their location from the grid and the position of measurement. It is also shown that the effects of a mandoline (Warhaft & Lumley 1978) may be idealized as the interference of thermal fields produced by a number of line sources. Thus new light is shed on the rate of decay of scalar-variance dissipation. The thermal field of a single line source is also examined in detail, and these results are compared with other recent measurements.

scholarly journals Thermal Field Analysis and Simulation of an Infrared Belt Furnace Used for Solar Cells

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Bai Lu ◽  
Liang Zongcun ◽  
Shen Hui
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Gas Flow ◽  
Thermal Field ◽  
Field Analysis ◽  
Metal Particles ◽  
Thermal Fields ◽  
Internal Structures ◽  
Cell Firing ◽  
Transient Thermal

During solar cell firing, volatile organic compounds (VOC) and a small number of metal particles were removed using the gas flow. When the gas flow was disturbed by the thermal field of infrared belt furnace and structure, the metal particles in the discharging gas flow randomly adhered to the surface of solar cell, possibly causing contamination. Meanwhile, the gas flow also affected the thermal uniformity of the solar cell. In this paper, the heating mechanism of the solar cell caused by radiation, convection, and conduction during firing was analyzed. Afterward, four 2-dimensional (2D) models of the furnace were proposed. The transient thermal fields with different gas inlets, outlets, and internal structures were simulated. The thermal fields and the temperature of the solar cell could remain stable and uniform when the gas outlets were installed at the ends and in the middle of the furnace, with the gas inlets being distributed evenly. To verify the results, we produced four types of furnaces according to the four simulated results. The experimental results indicated that the thermal distribution of the furnace and the characteristics of the solar cells were consistent with the simulation. These experiments improved the efficiency of the solar cells while optimizing the solar cell manufacturing equipment.

scholarly journals Mathematical modeling of groundwaters pressure distribution in the underground structures by cylindrical form zone

2018 ◽  
Vol 196 ◽  
pp. 02025 ◽  
Author(s):  
Valeriy Telichenko ◽  
Vladimir Rimshin ◽  
Vladimir Eremeev ◽  
Vladimir Kurbatov
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Pressure Distribution ◽  
Underground Structure ◽  
Viscosity Coefficient ◽  
Soil Porosity ◽  
Cylindrical Shape ◽  
Underground Structures ◽  
Cylindrical Form ◽  
Analytical Formulas

A mathematical model is developed for studying the distribution of groundwater pressure and its variation in the zone of underground structures of a cylindrical shape. Based on the created model, the influence of the thickness of the aquifer, the soil porosity, the filtration coefficient, the viscosity coefficient and the piezoelectric conductivity coefficient on the pressure that groundwater exerts on the lower part of the underground structure is investigated. The analysis of the possibility of pushing the structure and breaking the foundation under the influence of pressure caused by groundwater is analyzed. Analytical formulas are obtained for estimating the stresses in the foundation and predicting the possibility of its destruction.

Leak Detection Assessment of a Through Wall Crack in a Circumferential Weld

2017 ◽  
Author(s):  
Peter Gill ◽  
Colin Madew ◽  
Steve Booth
Keyword(s):  
Finite Element ◽  
Thermal Field ◽  
Crack Opening ◽  
Leak Detection ◽  
Defect Size ◽  
Element Analysis ◽  
Thermal Fields ◽  
Start Up ◽  
Tensile Data ◽  
Fit For Purpose

A leak detection assessment at a circumferential weld has been carried out to support a Leak-before-Break argument. This was performed using detailed finite element analysis (FEA) of the component to determine limiting defect sizes and crack opening areas. Leak rates of CO2 were then calculated and were found to be at an acceptable level. The loading on the component were complex, including thermal, pressure and weld residual stresses. The thermal field originated from both a steady state operating condition and hold point during start up plant state. Computational Fluid Dynamics (CFD) was used to generate the thermal fields for this component and the crack was postulated to occur at the region of highest opening stress along the weld. In addition to the thermal field, the weld was also subjected to a residual stress, which was applied in the model via a novel application method that is described in the paper. The FEA incorporated temperature dependent Ramberg-Osgood stress strain data that was generated from tensile data. For the limiting defect size calculation, lower bound material properties were used, and for the crack opening area, mean properties were used. Various crack sizes were considered and J-integrals were calculated and compared against the material toughness of the weld. This enabled the calculation of a limiting defect size, and crack opening area, so that a leakage rate could then be calculated. Contour independence was observed for the J-integral evaluation giving confidence that the finite element meshes were fit for purpose.

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