WO2020048110A1

WO2020048110A1 - Thermodynamic modeling and thermal design method for overall structure of high-speed processing machine

Info

Publication number: WO2020048110A1
Application number: PCT/CN2019/078377
Authority: WO
Inventors: 蒋书运; 朱国振
Original assignee: 东南大学
Priority date: 2018-09-07
Filing date: 2019-03-15
Publication date: 2020-03-12
Also published as: CN109376377A; CN109376377B; WO2020047880A1

Abstract

Provided is a thermodynamic modeling and thermal design method for the overall structure of a high-speed processing machine, comprising the following steps: step 1: performing three-dimensional digital modeling of a high-speed processing machine; step 2: calculating a heating power of a main heat source of the high-speed processing machine and a related heat transfer coefficient of the high-speed processing machine; step 3: calculating a thermal resistance parameter of a surface joint portion of the high-speed processing machine; step 4: performing thermodynamic modeling of the overall structure of the high-speed processing machine and calculating a thermal property thereof; and step 5: generating a thermal design method for the overall structure of the high-speed processing machine. The method can be adopted to greatly improve the accuracy of thermodynamic modeling of the overall structure of a high-speed processing machine and shortens a design cycle. The present invention not only facilitates forward design of a high-speed processing machine, but also increases the success rate of a first-time design.

Description

Thermodynamic Modeling and Thermal Design Method for High Speed Machining Machine Structure

Technical field

The invention relates to a method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure, and belongs to the field of numerical control machine tool design.

Background technique

CNC machine tools are developing in the direction of high speed and high precision, and the industry has higher and higher requirements for the thermal performance of high-speed processing machine tools. Establishing the thermodynamic model of the high-speed processing machine tool, conducting the thermodynamic analysis of the whole machine, and then completing the thermodynamic design of the machine tool are the first technical links in the research and development of high-speed machine tools.

The establishment of a high-precision high-speed machining machine thermodynamic model is the theoretical basis for developing the high-speed machining machine thermodynamic design. In recent years, scholars at home and abroad have carried out a lot of research around machine tool thermodynamic modeling and calculation of thermal characteristics. In summary, the main research work includes:

①Electro-spindle thermodynamics: Considering the rolling bearings in the spindle as well as the built-in motor rotor and stator as the main heat source, the heat transfer coefficients of the surfaces of the spindle are calculated, and the thermodynamic model of the electro-spindle is established. The temperature field and thermal displacement of the electro-spindle are calculated by the finite element method field.

② Thermal resistance at the joint of the machine tool: Establish the main joint surface thermal resistance of the machine tool, take the machine tool bed as the research object, establish a local thermodynamic model of the machine tool, and calculate the temperature field and thermal displacement field of the machine tool bed considering the thermal resistance through the finite element method.

It should be noted that the above two types of thermodynamic single-factor modeling and design methods of machine tools cannot meet the design requirements of high-speed processing machine tools. From the perspective of the forward thermal design of the machine tool, the integration of high-speed processing machine tools that consider the thermal resistance of the main heat sources (high-speed electric spindle, workpiece spindle, secondary heat source of cutting fluid) and the joints (plane joints, rolling joints) should be established. Based on this model, the thermodynamic characteristics analysis of high-speed processing machine tools can be carried out, and then the thermal design of the whole machine of high-speed processing machine tools is proposed to improve the thermal performance of the machine tools.

Summary of the Invention

Technical problem: In view of the problems existing in the thermodynamic modeling and thermal design of the high-speed processing machine tool, the invention patent proposes the main heat source of the high-speed processing machine tool (high-speed electric spindle, workpiece spindle, secondary heat source of cutting fluid) and the typical joint (plane (Joint, rolling joint) contact thermal resistance modeling method, and then established the whole machine thermodynamic model of high-speed processing machine tools; Based on the analysis results of the whole machine thermodynamic sensitivity of high-speed processing machine tools, a thermodynamic design method of high-speed processing machine tools was proposed. The invention patent not only facilitates the forward design of high-speed processing machine tools, but also improves the thermal design accuracy of the machine tools and the design success rate at one time.

Technical solution: A high-speed processing machine tool structure thermodynamic modeling and thermal design method of the present invention includes the following steps:

Step 1: Three-dimensional digital modeling of high-speed processing machine tools: The three-dimensional digital software is used to convert the preliminary structure of the proposed high-speed processing machine tools into three-dimensional CAD models;

Step 2: Calculation of the heating power and related heat transfer coefficient of the main heat source of high-speed processing machine tools: Calculate the heating power of rolling bearings using Palmgren's empirical formula, and calculate the convective heat transfer coefficient of relevant parts by using heat transfer theory; Basic data;

Step 3: Calculation of thermal resistance parameters of the plane joint of the machine tool: using fractal geometry theory, contact thermal resistance of the plane joint of the computer bed;

Step 4: Thermodynamic modeling and thermal characteristics calculation of the high-speed processing machine tool structure: Establish a complete machine thermodynamic model of the high-speed processing machine tool including the contact thermal resistance between the main heat source and the typical joint; develop the key parameters of the machine tool, and the physical parameters of the water-cooling system against Analysis and calculation of the thermodynamic sensitivity of the entire machine tool to find the weak links that affect the thermodynamic performance of the machine tool;

Step 5: The thermal design method of the high-speed processing machine tool structure: Aiming at the weak links affecting the thermodynamic performance of the machine tool found in step 4, aiming at improving the thermal performance of the machine tool, a dynamic design method of the high-speed processing machine tool machine structure is proposed.

Step 1: Three-dimensional digital modeling of the high-speed processing machine tool. The three-dimensional digital software Solidworks or Pro-E is used to convert the preliminary structure of the proposed high-speed processing machine tool into a three-dimensional CAD model.

The step 2: the calculation of the heating power of the main heat source and the related heat transfer coefficient of the high-speed processing machine tool is divided into the following three steps:

Step 2a: Calculation of heating power of electric spindle and workpiece spindle of high-speed processing machine

1) Calculation of heating power Q ₁ for rolling bearings,

Q ₁ = 1.047 × 10 ^-4 (M ₀ + M ₁ ) · n (1)

M ₁ = f ₁ p ₁ d _m (3)

In the formula: M ₀ is the hydrodynamic loss of the lubricant, M ₁ is the elastic hysteresis and the friction loss of the local differential sliding, n is the speed of the bearing, r / min; d _m is the bearing diameter, mm; f ₀ is the bearing Type and empirical constants related to the lubrication method, v is the kinematic viscosity of the lubricant at the working temperature, cst, f ₁ are parameters related to the bearing type and the load; p ₁ is the calculated load N to determine the bearing friction torque;

2) Calculation of heating power of rotor and stator of electric spindle motor

P ₀ is the rated power, the motor power coefficient α, and the efficiency η, then the heat loss Q = P ₀ α (1-η), where 2/3 of the heat loss is distributed in the motor rotor, and 1/3 of the heat loss is distributed in the motor stator;

3) Calculation of the heating power q _{belt of the} workpiece spindle _belt

q _belt = P _beltin (1-η) (3)

In the formula: P _beltin belt transmission input power W, η is the belt transmission efficiency, half of the heat loss of the belt transmission is transmitted to the belt, and half is transmitted to the belt wheel, and the frictional heat generated on the driving wheel and the driven wheel is based on the two belt wheels. Angle distribution of belts

Step 2b: Calculation of convective heat transfer coefficient between high-speed machining machine electric spindle and workpiece spindle

Relationship between heat transfer coefficient α and Nusser number Nu:

Where: λ is the thermal conductivity of the fluid, Nu _f is the Nusser number, and D is the fixed dimension of the geometric feature;

1) Calculation of forced convection heat transfer coefficient h _{1 of the} stator cooling water jacket of the built-in motor of the electric spindle

In the formula: λ is the thermal conductivity of the fluid, Nu _f is the Nusser number; Pr _f is the Prandtl number, Re _f is the Reynolds number, and L is the length of the cooling water channel;

2) Calculation of the heat transfer coefficient h _{2 of the} inner surface of the stator and the outer surface of the rotor of the electric spindle motor

In the formula: r ₁ is the outer diameter of the rotor (m); σ is fixed, the air gap between the rotors (m);

3) Calculation of the convective heat transfer coefficient h ₃ between the rotating surface of the workpiece spindle and the air

4) Convection heat transfer coefficient h _{4 of} workpiece spindle

h ₄ = 9.7 + 5.33 × U ^0.8 (8)

In the formula: h ₄ —Convection heat transfer coefficient W / (m ² · K); U—Linear surface speed m / s;

5) The convective heat transfer coefficient between the outer surface of the main shaft and the air, taking the composite heat transfer coefficient as h ₅ = 9.7W / (m ² · K)

Step 2c) Modeling method of "secondary heat source" of cutting fluid

Calculation of convection heat transfer coefficient Nu of cutting fluid flow channel part:

Convection heat transfer coefficient of the surface to which the cutting fluid splashes: Multiply the convection coefficient of the cutting fluid channel by 0.6 to obtain the convection coefficient of the surface. The qualitative temperature of formula (9) is the average temperature T _{m of the} fluid and the wall. Length L of wall surface through which fluid flows.

Step 3: The calculation of the thermal resistance parameters of the main joint of the high-speed processing machine tool is divided into the following two steps:

Step 3a) Calculation of contact thermal resistance R _c of the fixed bonding surface

The total contact thermal resistance TCR is

In the formula: R _ci is the i-th micro-convex contact thermal resistance.

The dimensionless total contact thermal resistance is

Where R _ci is the i-th micro-convex contact thermal resistance,

Is the relative area contact ratio,

Is the cross-sectional area of the i-th microconvex, and N (a ′ _s ) is the number of contact points;

Step 3b) Calculation of the contact thermal resistance between the bearing outer ring and the bearing seat

The bearing contact thermal conductivity is,

Where: Π is the contact thermal conductivity (W / K); h _ring and h _gap are the average thickness of the bearing outer ring, the outer ring and the bearing seat, respectively; λ _ring and λ _gap are the air in the bearing outer ring and the gap, respectively. Thermal conductivity W / (m ² · K), A is the cylindrical outer surface area of the bearing ring;

The average gap h _gap can be calculated by the following formula

h _gap = h _gap0- (T _ring -T _housing ) _a′r _housing (13)

In the formula: h _gap is the original gap between the bearing outer ring and the bearing seat, m; a ′ is the linear expansion coefficient, which can be 11.7 × 10 ^-6 / K for steel.

Step 4: Thermodynamic modeling and thermal characteristic calculation of the high-speed processing machine tool structure, establishing a complete machine thermodynamic model of the high-speed processing machine tool including the thermal resistance of the main heat source and the typical joint contact thermal resistance; developing the heating power of the main heat source of the high-speed processing machine tool, Sensitivity analysis and calculation of key machine parts and water cooling system physical parameters to the thermodynamic performance of high-speed processing machine tools, looking for weak links and main factors that affect the thermal performance of machine tools.

The main heat source is a high-speed electric main shaft, a workpiece main shaft, and a secondary heat source for cutting fluid; typical joints are a planar joint and a rolling joint.

The thermodynamic performance of the high-speed processing machine tool includes a temperature field and a thermal displacement field.

Step 5: The thermal state design method of the high-speed processing machine tool structure, surrounding the weak links and main factors affecting the thermal performance of the machine tool found in step 4, with the goal of reducing thermal deformation and improving processing accuracy during the process of modifying the machine tool Structural parameters of main components, redesign related physical parameters, and complete thermal design of high-speed processing machine tools.

Beneficial effect: The thermodynamic modeling and thermal design method of the high-speed processing machine tool structure provided by the present invention is based on the thermodynamic analysis and calculation results of a complete high-speed processing machine tool thermodynamic model and system. Therefore, by adopting the "thermodynamic modeling and thermal design method for the whole structure of a high-speed processing machine tool" of the present invention, the thermal design accuracy of the machine tool and the design success rate at one time can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 Design steps and content of the invention patent,

Figure 2 Three-dimensional digital model of high-speed processing machine,

a is a 3D-CAD model of the internal compound grinding machine,

b is the finite element analysis model of the whole machine,

Fig. 3 Dimensionless contact thermal resistance R ^* Calculation results under the influence of different parameters,

a is the relationship between the dimensionless contact thermal resistance and the contact load under different G ^* (E / σ = 106, D = 1.3),

b is the relationship between the dimensionless contact thermal resistance and the contact load under different D (E / σ = 106, G = 10 ^-7 ),

c is the relationship between the dimensionless contact thermal resistance and the contact load at different E / σ (D = 1.3, G = 10 ^-7 ),

d is the relationship between the dimensionless contact area and the contact thermal resistance under different contact deformation situations,

Figure 4 Cloud diagram of temperature field distribution under rated conditions of the whole machine,

a is the cloud diagram of the temperature range of the entire machine under rated working conditions at an isometric perspective,

b is the distribution cloud diagram of the rated operating temperature field of the whole machine from the rear view perspective,

Fig. 5 Distribution diagram of thermal displacement field under rated conditions of the whole machine,

a is the cloud map of the thermal displacement field of the entire machine under the rated operating conditions at an isometric perspective,

b is the cloud diagram of the thermal displacement field distribution of the complete machine under rated operating conditions,

Figure 6 Cloud diagram of the whole machine temperature field after thermal design.

a is the cloud map of the whole machine temperature field after thermal design from the perspective of the top view,

b is the cloud map of the whole machine's temperature field after thermal design from the perspective of the back view.

detailed description

In the following, an embodiment (precision numerical control inner circle composite grinder) is used to further describe the thermodynamic design method of the entire structure of the high-speed processing machine tool of the present invention.

FIG. 1 shows the specific content of the thermodynamic design method of the high-speed processing machine tool structure of the present invention, including the following steps:

Step 1: 3D digital modeling of high-speed processing machine

3D modeling software (such as Solidworks) is used to establish a 3D digital (CAD, CAE) model of a precision CNC internal cylindrical composite grinder, as shown in Figure 2.

Step 2: Calculation of heating power of main heat source of high-speed processing machine

Step 2a: Use formulas (1)-(3) to calculate the heating power Q of the high-speed machining machine grinding electric spindle rolling bearing. The calculation results are shown in Table 1 at different temperatures.

Table 1 Correspondence between the heat generation rate q and temperature of the electric spindle bearing for internal grinding (q = Q / V)

Using formulas (1)-(3), calculate the heating power Q of the rolling bearing of the spindle of the high-speed machining machine tool. Under different temperature conditions, the bearing heat generation rate at different temperatures is obtained, as shown in Table 2.

Table 2 Correspondence between bearing heat generation rate and temperature (q = Q / V)

The electric motor's built-in motor has a rated power of 16kW, a power factor of 0.9 under normal working conditions, and a power loss of 1.5kW. Assuming that all the losses are converted into heat, of which 2/3 (1kW) is emitted by the stator and 1/3 (0.5kW) is emitted by the rotor, the motor heating and rotor heat generation rates are 254250W / m ³ and 255056W / m ^{3 respectively} .

The efficiency of the belt drive is 96%. The belt drive input power P _beltin is the friction loss power of the tilting pad dynamic pressure bearing and thrust sliding bearing, which is 5.5kW. The frictional heat loss of the driven pulley on the workpiece spindle (q _belt ) It is 43.86W.

Use formula (5) to calculate the convective heat transfer coefficient of forced cooling water h ₁ = 13719W / (m ² · K)

Adopt formula (6) Convection heat transfer coefficient of motor with built-in rotor and stator h ₂ = 116.2W / (m ² · K)

Use formula (7) to calculate the convective heat transfer coefficient between the rotating surface of the workpiece spindle and the air h ₃ = 100W / (m ² · K)

According to formula (8), the convection heat transfer coefficients corresponding to the radial surfaces of the pulley diameters of 245mm, 200mm, and 144mm are 81W / (m ² · K), 70W / (m ² · K), and 56W / (m ² · K); the convective heat transfer coefficients of the radial surfaces of the grinding wheel with a diameter of 95mm and 56mm are 43W / (m ² · K) and 31W / (m ² · K)

Convective heat transfer coefficient between the outer surface of the main shaft and the air, taking the composite heat transfer coefficient as h ₅ = 9.7W / (m ² · K)

Step 2c: Use formula (9) to calculate the relevant convective heat transfer coefficient of the cutting fluid of the high-speed processing machine tool as a "secondary heat source". The flow rate of the cutting fluid is 100 L / min under rated conditions. The convection heat transfer coefficients of the main surfaces are shown in Table 3:

Table 3 Convection heat transfer coefficients of the main surfaces of the bed

Step 3: Calculation of thermal resistance parameters of the plane joint of the machine tool

Step 3a: Use formulas (10) and (11) to calculate the total contact thermal resistance R and the dimensionless contact thermal resistance R ^* . The calculation results are shown in FIG.

Step 3b: Use formula (12) to calculate the contact thermal resistance between the outer ring of the bearing and the bearing block. For ordinary spindle bearings (take 4 levels of machining accuracy), take h _ring = 5 × 10 ^-6 m, λ _ring = 24W / ( m · K), λ _gap = 2.84 × 10 ^-2 W / (m · K), then the contact coefficient between the spindle bearing and the mating surface is shown in Table 4.

Table 4 Contact coefficient h between the main shaft bearing and the mating surface (unit: W / m ² · K)

Step 4: Thermodynamic Modeling and Thermal Characteristic Calculation of High Speed Machining Machine Structure

In this embodiment, the internal grinding hole diameter is 150 mm, and the grinding wheel diameter is 80 mm. All internal heat sources such as electric spindle, bedside box and cutting fluid are applied to the thermodynamic analysis model of the machine tool, and the temperature field distribution cloud diagram of the whole machine under rated working conditions is calculated, as shown in Figure 4.

The cloud diagram of the thermal displacement field of the whole machine under rated conditions is shown in Figure 5. The black grid in the figure indicates the outline when no thermal deformation has occurred.

The thermal displacements of the main parts of the machine under rated conditions are listed in Table 5.

Table 5 The average thermal displacement of each component of the machine under rated conditions

After conversion, the internal hole and tapered surface grinding error caused by the thermal deformation of the whole machine is 43.30 μm.

Step 5: Thermal design method of high-speed processing machine tool structure

According to the analysis result of step 4, this embodiment improves the design of the machine tool structure. The flat plate with the same size as the flow path is covered on the flow path, so that the cutting fluid does not directly contact the bed, and the heat transmitted to the bed is reduced, thereby reducing the bed. Thermal deformation, the thermal displacement of the main parts are listed in Table 6.

Table 6 Average thermal displacement of each component after thermal design

After thermal design, the grinding error of the inner hole and the tapered surface caused by the thermal deformation of the whole machine is 1.15 μm.

From the design results, under the condition that the grinding hole diameter is 150mm and the internal grinding wheel diameter is 80mm, the comparison of the processing thermal errors before and after the thermal design of the grinding machine is shown in Table 7. It can be seen that the use of the invention patent "the method of thermodynamic modeling and thermal design of the whole structure of a high-speed processing machine tool" can greatly improve the grinding accuracy of the machine tool.

Table 7 Comparison of processing accuracy before and after thermal design

Claims

A high-speed processing machine tool structure thermodynamic modeling and thermal design method is characterized in that the method includes the following steps:

Step 1: Three-dimensional digital modeling of high-speed processing machine tools: The three-dimensional digital software is used to convert the preliminary structure of the proposed high-speed processing machine tools into three-dimensional CAD models;

Step 2: Calculation of the heating power and related heat transfer coefficient of the main heat source of high-speed processing machine tools: Calculate the heating power of rolling bearings using Palmgren's empirical formula, and calculate the convective heat transfer coefficient of relevant parts by using heat transfer theory; Basic data;

Step 3: Calculation of thermal resistance parameters of the plane joint of the machine tool: using fractal geometry theory, contact thermal resistance of the plane joint of the computer bed;

Step 4: Thermodynamic modeling and thermal characteristics calculation of the high-speed processing machine tool structure: Establish a complete machine thermodynamic model of the high-speed processing machine tool including the contact thermal resistance between the main heat source and the typical joint; develop the key parameters of the machine tool, and the physical parameters of the water-cooling system against high-speed Analysis and calculation of the thermodynamic sensitivity of the entire machine tool to find the weak links that affect the thermodynamic performance of the machine tool;

Step 5: The thermal design method of the high-speed processing machine tool structure: Aiming at the weak links affecting the thermodynamic performance of the machine tool found in step 4, aiming at improving the thermal performance of the machine tool, a dynamic design method of the high-speed processing machine tool machine structure is proposed.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 1, wherein the step 1: three-dimensional digital modeling of the high-speed processing machine tool, using three-dimensional digital software Solidworks or Pro-E, The preliminary structure of the designed high-speed machining machine was transformed into a three-dimensional CAD model.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 1, wherein said step 2: the calculation of the heating power and the related heat transfer coefficient of the main heat source of the high-speed processing machine tool are divided into the following three step:

Step 2a: Calculation of heating power of electric spindle and workpiece spindle of high-speed processing machine

1) Calculation of heating power Q 1 for rolling bearings,

Q 1 = 1.047 × 10 -4 (M 0 + M 1 ) · n (1)

M 1 = f 1 p 1 d m (3)

In the formula: M 0 is the hydrodynamic loss of the lubricant, M 1 is the elastic hysteresis and the friction loss of the local differential sliding, n is the speed of the bearing, r / min; d m is the bearing diameter, mm; f 0 is the bearing Type and empirical constants related to the lubrication method, v is the kinematic viscosity of the lubricant at the working temperature, cst, f 1 are parameters related to the bearing type and the load; p 1 is the calculated load N to determine the bearing friction torque;

2) Calculation of heating power of rotor and stator of electric spindle motor

P 0 is the rated power, the motor power coefficient α, and the efficiency η, then the heat loss Q = P 0 α (1-η), where 2/3 of the heat loss is distributed in the motor rotor, and 1/3 of the heat loss is distributed in the motor stator;

3) Calculation of the heating power q belt of the workpiece spindle belt

q belt = P beltin (1-η) (3)

In the formula: P beltin belt transmission input power W, η is the belt transmission efficiency, half of the heat loss of the belt transmission is transmitted to the belt, and half is transmitted to the pulley, and the frictional heat generation on the driving and driven wheels is based on the two pulleys. Angle distribution of belts

Step 2b: Calculation of convective heat transfer coefficient between high-speed machining machine electric spindle and workpiece spindle

Relationship between heat transfer coefficient α and Nusser number Nu:

Where: λ is the thermal conductivity of the fluid, Nu f is the Nusser number, and D is the fixed dimension of the geometric feature;

1) Calculation of forced convection heat transfer coefficient h 1 of the stator cooling water jacket of the built-in motor of the electric spindle

In the formula: λ is the thermal conductivity of the fluid, Nu f is the Nusser number; Pr f is the Prandtl number, Re f is the Reynolds number, and L is the length of the cooling water channel;

2) Calculation of the heat transfer coefficient h 2 of the inner surface of the stator and the outer surface of the rotor of the electric spindle motor

In the formula: r 1 is the outer diameter of the rotor (m); σ is fixed, the air gap between the rotors (m);

3) Calculation of the convective heat transfer coefficient h 3 between the rotating surface of the workpiece spindle and the air

4) Convection heat transfer coefficient h 4 of workpiece spindle

h 4 = 9.7 + 5.33 × U 0.8 (8)

In the formula: h 4 —Convection heat transfer coefficient W / (m 2 · K); U—Linear surface speed m / s;

5) The convective heat transfer coefficient between the outer surface of the main shaft and the air, taking the composite heat transfer coefficient as h 5 = 9.7W / (m 2 · K)

Step 2c) Modeling method of "secondary heat source" of cutting fluid

Calculation of convection heat transfer coefficient Nu of cutting fluid flow channel part:

Convection heat transfer coefficient of the surface to which the cutting fluid splashes: Multiply the convection coefficient of the cutting fluid channel by 0.6 to obtain the convection coefficient of the surface. The qualitative temperature of formula (9) is the average temperature T m of the fluid and the wall. Length L of wall surface through which fluid flows.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 1, wherein the step 3: calculating the thermal resistance parameters of the main joint of the high-speed processing machine tool is divided into the following two steps:

Step 3a) Calculation of contact thermal resistance R c of the fixed bonding surface

The total contact thermal resistance TCR is

In the formula: R ci is the i-th micro-convex contact thermal resistance.

The dimensionless total contact thermal resistance is

Where R ci is the i-th micro-convex contact thermal resistance,
Is the relative area contact ratio,
Is the cross-sectional area of the i-th microconvex, and N (a ′ s ) is the number of contact points;

Step 3b) Calculation of the contact thermal resistance between the bearing outer ring and the bearing seat

The bearing contact thermal conductivity is,

Where: Π is the contact thermal conductivity (W / K); h ring and h gap are the average thickness of the bearing outer ring, the outer ring and the bearing seat, respectively; λ ring and λ gap are the air in the bearing outer ring and the gap, respectively. Thermal conductivity W / (m 2 · K), A is the cylindrical outer surface area of the bearing ring;

The average gap h gap can be calculated by the following formula

h gap = h gap0- (T ring -T housing ) a′r housing (13)

In the formula: h gap is the original gap between the bearing outer ring and the bearing seat, m; a ′ is the linear expansion coefficient, which can be 11.7 × 10 -6 / K for steel.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 1, characterized in that, said step 4: thermodynamic modeling and thermal characteristic calculation of the high-speed processing machine tool structure, establishing the main heat source and typical The whole machine thermodynamic model of the high-speed processing machine tool with contact thermal resistance at the joint; the sensitivity analysis and calculation of the thermal power of the main heat source of the high-speed machine tool, the key components of the machine tool, and the physical parameters of the water-cooling system on the thermodynamic performance of the high-speed machine tool are sought to find the effect on the machine tool Weak links and main factors of thermal performance.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 5, wherein the main heat source is a high-speed electric spindle, a workpiece spindle, and a secondary heat source for cutting fluid; a typical joint is a planar joint Scrolling joint.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 5, wherein the thermodynamic performance of the high-speed processing machine tool includes a temperature field and a thermal displacement field.
The method for thermodynamic modeling and thermal design of a high-speed processing machine tool structure according to claim 1, characterized in that said step 5: a method for thermal state design of the high-speed processing machine tool structure, affecting the thermal performance of the machine tool found around step 4 Weak links and main factors are designed to reduce thermal deformation during processing and improve processing accuracy, modify the structural parameters of the main parts of the machine tool, redesign the relevant physical parameters, and complete the thermal design of the high-speed processing machine tool.