En nghiên cứu tối ưu hóa một số thông số công nghệ và bôi trơn tối thiểu khi phay mặt phẳng hợp kim ti 6al 4v

Investigating the flat surface milling of Ti-6Al-4V alloy using the MQL method will provide conditions for the development of MQL in machining various materials in Vietnam… Thus, the doc

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NGUYEN VAN CANH

OPTIMIZATION OF CUTTING AND MINIMUM QUANTITY LUBRICATION PARAMETERS IN FACE MILLING OF TI-6AL-4V

Major: Mechanical Engineering Code: 9.52.01.03

SUMMARY OF DESERTATION IN ENGINEERING

Hanoi, 2024

This desertation has been completed at:

HANOI UNIVERSITY OF INDUSRY

Scientific supervisors:

1 Assoc Prof Dr Hoang Tien Dung

2 Prof Dr Pham Van Hung

Reviewer 1:

Reviewer 2:

Reviewer 3:

The desertation was defended at the Doctoral Evaluating Council at

University level, held at Hanoi University of Industry at …., date… 20…

The desertation can be found at:

- The library of Hanoi University of Industry

- Vietnam National Library

INTRODUCTION

1 Reason for research topic selection

Titanium alloy is an essential material widely utilized in various industries, particularly in aerospace, space technology, and engine manufacturing, constituting approximately 84% of the total Among these alloys, Ti-6Al-4V alloy accounts for over 50% of the global consumption of titanium alloys [1] During the machining process of Ti-6Al-4V alloy, significant heat is generated due to friction between the cutting tool and the workpiece at the cutting interface, directly affecting machining accuracy, surface quality, and tool durability To increase machining speed and reduce heat and cutting force, a cooling lubricant is commonly employed

The most prevalent method of lubrication and cooling using a cooling lubricant is through "flood cooling," where the nozzle directs the coolant into the cutting zone However, flood cooling has certain limitations concerning economic efficiency, environmental impact, and user health Specifically, the cost of purchasing and disposing of coolant after use is substantial [2], and the coolant is non-biodegradable and toxic [3] Currently, to address the limitations

of flood cooling, Minimum Quantity Lubrication (MQL) has been researched and implemented This method allows for minimizing the amount of coolant lubricant and using environmentally friendly lubricants while not compromising the operator's health [4] Therefore, MQL is considered a suitable lubrication and cooling method for machining processes in line with the principles of "sustainable machining" and "green manufacturing."

Following the principle of "Economic Development in Harmony with Environmental Protection" [9], several studies on MQL in machining SKD 11 tool steel [10] or 9XC steel (9CrSi) [11] have been researched and published Investigating the flat surface milling of Ti-6Al-4V alloy using the MQL method will provide conditions for the development of MQL in machining various materials in Vietnam… Thus, the doctoral student has chosen the

research topic "Optimization of some technological parameters and minimum lubrication in milling flat surfaces of Ti-6Al-4V alloy" aiming for green and

sustainable manufacturing

2 Research Objectives

General Objective:

To optimize certain technological parameters and minimum lubrication in milling flat surfaces of Ti-6Al-4V alloy

- Optimize cutting and MQL parameters using the SVR-NSGA II-TOPSIS

combination for milling flat surfaces of Ti-6Al-4V alloy

3 Research Subject, Scope

4 Research Content

(1) Overview of milling titanium alloy Ti-6Al-4V under minimum lubrication conditions; (2) Study of characteristic parameters during milling flat surfaces under minimum lubrication conditions;(3) Research on methods, experimental equipment, and comparative experiments;(4) Experimental results and optimization of the milling process of Ti-6Al-4V titanium alloy

5 Research Methodology

Theoretical research: Analyze and predict the effects of milling process

parameters on milling characteristics, thus developing an experimental model with Ti-6Al-4V alloy

Experimental research: Establish an experimental model and conduct

experiments Utilize advanced data processing methods to derive regression

equations and optimize the milling process of Ti-6Al-4V alloy

6 Scientific and Practical Significance of the Research

6.1 Scientific Significance

- Development of multi-objective optimization algorithms for the milling process of Ti-6Al-4V alloy based on the application of the SVR-NSGA II - TOPSIS combination

- The research outcomes can serve as valuable reference materials for related studies in the fields of minimum lubrication, machining of Ti-6Al-4V alloy, and multi-objective optimization of machining processes

6.2 Practical Significance

The research results aid engineers in selecting appropriate technological parameters and minimum lubrication for achieving quality objectives in the milling process of Ti-6Al-4V alloy based on multi-objective optimization algorithms

7 Novel Contributions of the Research

- Establishment and integration of an MQL minimum lubrication system for the milling of Ti-6Al-4V alloy flat surfaces

- Investigation and development of regression models regarding the relationship between machining process parameters (Vc, fz, ap) and minimum lubrication system technological parameters (P, Q) with criteria (Ra, Fc, MRR)

- Development of mathematical models and optimization problems for technological parameters in the milling process of Ti-6Al-4V alloy under minimum lubrication conditions

8 Structure of the Thesis

Apart from the Introduction, Conclusion, and Future Research Directions, the research content is presented in 4 chapters:

Chapter 1 Overview of milling Ti-6Al-4V alloy under minimum lubrication

conditions

Chapter 2 Characteristic parameters during milling flat surfaces under

minimum lubrication conditions

Chapter 3 Establishment of experimental models and survey experiments Chapter 4 Optimization of technological parameters in milling flat surfaces of

Ti-6Al-4V alloy under minimum lubrication conditions

CHAPTER 1: OVERVIEW OF MACHINING TITANIUM ALLOY TI-6AL-4V UNDER MINIMUM LUBRICATION CONDITIONS

The content of Chapter 1 focuses on related research regarding

(1) Introduction to titanium and common titanium alloys; (2) Applications

of Ti-6Al-4V alloy in various fields; (3) Machinability of Ti-6Al-4V alloy; (4) Characteristics of the machining process of Ti-6Al-4V alloy; (5) Minimum

lubrication and its application in machining titanium alloys; (6) Research status

at home and abroad

From there, the following conclusions are drawn:

Milling flat surfaces of Ti-6Al-4V alloy under minimum lubrication conditions using cylindrical end mills equipped with carbide inserts is highly topical, scientifically rigorous, and practical

CHAPTER 2: CHARACTERISTIC PARAMETERS DURING MILLING FLAT SURFACES UNDER MINIMUM LUBRICATION CONDITIONS

Some of the contents studied and presented in Chapter 2 include:

2.1 Khái quát về quá trình phay

2.1 Overview of the milling process;

2.2 Kinematics of the milling process;

2.2.1 Cutting forces in milling Ti-6Al-4V alloy;

2.2.1.1 Cutting force models in milling;

2.2.1.2 Factors influencing cutting forces in milling;

2.2.2 Vibration in milling Ti-6Al-4V alloy;

2.2.2.1 Vibration in milling processes;

2.2.2.2 Causes of vibration;

2.2.2.3 Characteristics of vibration in Ti-6Al-4V milling;

2.3 Cutting heat in milling under minimum lubrication conditions;

2.3.1 Heat generation in milling;

High temperatures generated during cutting processes can affect the surface quality of products, the durability of cutting tools, and their lifespan, as well as cause product deformation

2.3.2 Factors affecting cutting heat;

In metal cutting, metal is removed by the cutting edge of the tool, which cuts the workpiece material The energy used in deforming the metal is released, mainly in the form of heat, in the primary and secondary cutting zones

2.4 Tool Wear in Machining

During cutting, the workpiece slides against the front face of the tool, causing significant wear on both the front and back faces of the cutting tool

2.5 Characteristics and Surface Quality After Milling

Surface quality not only affects the dimensional accuracy of machined parts but also influences their properties and performance during use

2.5.1 Surface Roughness After Milling

Surface roughness reflects the stability of the machined surface Material deformation, cutting forces, vibration, and tool wear all impact the surface roughness of machined parts Cutting conditions directly affect the surface roughness of machined parts

2.5.2 Factors Affecting Surface Roughness

{Vc, fz, ap, P, Q}

2.6 Milling of Ti-6Al-4V Alloy Under MQL Conditions

2.6.1 Characteristics of Milling Ti-6Al-4V Alloy

In common metal machining, about 90% of heat is generated from plastic deformation However, the main difference of titanium alloy compared to other metal alloys is its low thermal conductivity

2.6.2 Application of Minimum Lubrication in Machining Ti-6Al-4V Alloy 2.6.3 Characteristics of Cutting Tools in Machining Ti-6Al-4V Alloy

Researching the characteristics of cutting forces, vibration, chip formation, surface quality, and tool wear when milling Ti-6Al-4V alloy

CHAPTER 3: CONSTRUCTION OF EXPERIMENTAL MODELS AND EXPERIMENTAL INVESTIGATION

In this chapter, the following main contents are carried out:

3.1 Purpose and Requirements of Experimental Research

Purpose: To establish a method, experimental equipment system, and

experiments to evaluate the effectiveness of MQL compared to dry machining and flood cooling conditions based on criteria for Ra, Fc, and Vb

Requirements: Convenient MQL lubrication system for fabrication, installation,

and operation during the experimental process

The system should have lubrication equipment capable of adjusting the

pressure and flow rate of the lubricant

Stability of pressure in the minimum lubrication system during the

experimental process

3.2 Construction and Integration of Experimental Equipment System

3.2.1 Object of Experimental Research

Experimental milling of Ti-6Al-4V alloy under minimum lubrication

conditions using cutting oil

- Milling method: Flat surface milling

- Technological parameters of the milling process used in the study include cutting speed (Vc), feed per tooth (fz), and depth of cut (ap)

- Technological parameters of the minimum lubrication system include air supply pressure (P) and lubricating oil flow rate (Q)

- Quality criteria surveyed include surface roughness (Ra), cutting force (Fc), and tool flank wear (Vb)

3.2.2 Experimental Equipment

3.2.2.1 Flow rate adjustment range

The technical specifications of the MQL equipment are presented in Table 3-1

Table 3-1 Technical Specifications of the Minimum Lubrication System

2 Maximum air supply pressure 8 bar

3 Flow rate adjustment range 0-1000 ml/h

3.2.2.2 Machine and Cutting Tools

- Machine: DMG Mori Seiki DMU50 5-axis machining center

- Cutting tools: Sandvik cutting tools with TiCN+Al2O3+TiN coating

3.2.2.3 Measurement Equipment and Tools

Surface roughness measurement: Mitutoyo Surftest JS-210; Cutting force measurement: Kistler 9139AA; Tool wear measurement: Keyence VHX-7000 optical microscope

Fig 3- 5 Surftest JS-210; Fig 3- 6 Kistler 9139AA; Fig 3- 7 VHX-7000

3.3 Evaluation of the Influence of Different Lubrication Environments on Surface Roughness, Cutting Force, and Tool Wear

To assess the influence of different technological parameters (Vc, fz, ap) on surface roughness Ra, cutting force Fc, and tool flank wear Vb, the Taguchi L27 matrix has been chosen for the experimental study

3.3.1 Experimental Matrix

Table 3-5 Investigated Variables for Tool Wear with Corresponding Levels of Values

Var Unit Description Level 1 Level 2 Level 3

Kết quả thực nghiệm được tổng hợp trong bảng 3-6

3.3.2 Tiến hành thực nghiệm

The experiments were conducted following the sequence described in Fig 3-8

Figure 3- 8 Sequence of Experiments Table 3-7 Experimental Matrix Evaluating the Influence of Technological Modes on Cutting Force, Surface Roughness, and Tool Wear under Different Machining Conditions

3.3.3 Results and Discussion

3.3.3.1 Influence on Surface Roughness (R a )

The ANOVA analysis results show that the surface roughness of the machined parts under minimum lubrication conditions is the smallest; the surface roughness under dry machining conditions is higher in most experiments (Figure 3-10)

The surface of the machined parts reveals variations in surface roughness among different machining conditions, as depicted in Figure 3-11 The coloration in the image of the workpiece after machining under minimum lubrication conditions (Figure 3-11b) illustrates uniformity in color, indicating

more consistent surface heights compared to machining under flood coolant conditions

Figure 3-10 Comparison of Surface Roughness R a under Different Lubrication Conditions

This can be attributed to the mist form of the coolant, which can penetrate better into the cutting zone Conversely, the image of the surface of the machined part under dry machining conditions (Figure 3-11a) shows significant differences in surface peaks and valleys This is a common phenomenon in dry machining, where high cutting temperatures result from inadequate cooling during cutting operations

Fig 3-11 Surface images of the wp after machining under different milling conditions

Figure 3-12 illustrates the Ra value decreasing when transitioning from dry machining to minimum quantity lubrication (MQL) conditions, and increasing again when switching to flood coolant mode

The surface roughness (Ra) values decrease significantly under dry machining conditions (CL=1, Figure 3-11) as cutting speed (Vc) increases from

60 m/min to 150 m/min, with a slight further increase as Vc reaches 240 m/min Conversely, the Ra values remain stable under minimum quantity lubrication and flood coolant conditions, corresponding to a cutting speed of

150 m/min

Figure 3- 12 Correlation between input parameters and surface roughness values R a

Table 3-8 Response table for the standard deviation of surface roughness R a

3.3.3.2 Impact on cutting force F c

The analysis results in Figure 3-12 show that Fc is the lowest when machining under minimum lubrication conditions and the highest under dry machining conditions in most experiments

Figure 3-13 Comparison of cutting force Fc values under different lubrication conditions

The influence of Vc on Fc is the highest, followed by CL and fz The influence of ap on Fc is negligible

Figure 3-14 Interaction plot for cutting force Fc values

The trend of Fc variation (Figure 3-14) under dry cutting, minimum quantity lubrication, and flood conditions is quite similar, where the cutting force decreases as Vc increases from level 1 to level 2, and Fc increases again

3.3.3.3 Impact on flank wear V b

The analysis results show that flank wear Vb is minimal when machining under minimum quantity lubrication conditions in most experiments Conversely, the flank wear Vb is higher when machining under dry cutting conditions in most experiments (Figure 3-15)

Figure 3-15 Comparison of flank wear (Vb) under different machining conditions