A physics-based dynamic dual heat source model for UVAD of UD-CFRP with intermittent contact and anisotropic heat conduction

다국어 초록 (Multilingual Abstract)

Ultrasonic vibration-assisted drilling （UVAD） has emerged as an effective technique for improving the machining quality of carbon fiber reinforced polymer （CFRP） composites by reducing cutting forces, mitigating delamination, and suppressing thermal damage. However, the complex thermo-mechanical coupling behavior in UVAD, particularly the interaction between intermittent tool–workpiece contact and anisotropic heat conduction, remains insufficiently understood. To address this issue, this study develops a physics-based dynamic dual heat source mechanistic model to characterize the transient thermal behavior during UVAD of unidirectional CFRP （UD-CFRP）. In the proposed model, the heat generation mechanisms associated with different cutting regions are explicitly considered. The chisel edge is modeled as a circular moving heat source dominated by extrusion deformation and friction, whereas the main cutting edges are represented as truncated conical surface heat sources incorporating both cutting and frictional heat generation. To capture the ultrasonic-induced intermittent contact, an effective cutting ratio is introduced, which couples the instantaneous thrust force and heat generation with the fiber orientation angle （FOA）, enabling accurate representation of localized heat input and dynamic heat-source modulation. Based on the anisotropic thermophysical properties of UD-CFRP, a non- homogeneous transient heat conduction model is formulated. Through coordinate transformation and homogenization, the governing equation is analytically solved using Green’s function to obtain the three-dimensional transient temperature field induced by moving heat sources. The model integrates cutting mechanics, heat generation, and anisotropic heat transfer into a unified analytical framework. To validate the proposed model, a series of drilling experiments were conducted using a longitudinal ultrasonic vibration-assisted machining system. The cutting forces were measured by a dynamometer, and the temperature field was captured using infrared thermography. The predicted thrust force and temperature evolution show strong agreement with experimental results, with average relative errors of 5.34% and 4.98%, respectively, and peak temperature errors within 4.47–5.69%, confirming the accuracy and reliability of the model. The results demonstrate that ultrasonic vibration significantly alters the thermal behavior of the drilling process. Compared with conventional drilling, UVAD reduces the peak temperature at the hole exit by 9.10% under representative cutting conditions. With increasing ultrasonic amplitude from 0 μm to 6 μm, the peak hole wall temperature decreases by 8.93–21.81%, while the average temperature in the exit region decreases by 18.69%. Furthermore, due to the anisotropic thermal conductivity of UD- CFRP, the temperature field exhibits a characteristic four-lobed distribution, with maximum temperatures occurring at fiber orientations of 0° and 180°. The proposed model reveals the underlying coupling mechanisms among ultrasonic vibration, cutting forces, fiber orientation, and anisotropic heat transfer. By capturing the dynamic modulation of heat sources and the spatially non-uniform temperature evolution, it provides a physically grounded and computationally efficient tool for predicting temperature fields in composite drilling. The findings offer valuable guidance for process parameter optimization, thermal damage suppression, and high- quality machining of advanced composite materials.

목차 (Table of Contents)

• Chapter 1 Introduction 1
• 1.1 Research Background and Engineering Significance 1
• 1.2 Current Research Status at Home and Abroad 2
• 1.2.1 Research Status on Drilling Thermal Damage and Temperature Issues of CFRP 2
• 1.2.2 Current Research Status of Thermal-Force Effects in Ultrasonic Vibration-Assisted Processing 3
• 1.2.3 Research Status of CFRP Drilling Temperature Testing and Modeling Methods 4
• 1.2.4 Summary of Existing Research Shortcomings and Key Scientific Issues 5
• 1.3 Main Research Contents and Technical Route of the Paper ·· 7
• 1.4 Innovation Points of the Paper 8
• Chapter 2 Cutting Mechanics Modeling of LUVAD 9
• 2.1 Kinematic modeling of ultrasonic drilling 9
• 2.1.1 Motion Model of Longitudinal Ultrasonic Vibration ·· 9
• 2.1.2 Dynamic Tool–Workpiece Interaction 10
• 2.1.3 Tool geometry modeling 13
• 2.1.4 Dynamic Uncut Chip Thickness Model 16
• 2.2 Cutting force modeling 17
• 2.3 Chapter Summary 34
• Chapter 3 Thermal Modeling of LUVAD 36
• 3.1 Heat source modeling 36
• 3.1.1 Heat generation mechanism 36
• 3.1.2 Heat source configuration and moving heat source model 37
• 3.2 Heat Source Modeling of Chisel Edge 38
• 3.2.1 Physical Description of Circular Heat Source 38
• 3.2.2 Heat Flux Distribution Model 39
• 3.2.3 Heat Partition Ratio 40
• 3.3 Heat Generation Model of the Main Cutting Edges under Ultrasonic Vibration 40
• 3.3.1 Heat Generation Mechanism of the Main Cutting Edges 41
• 3.3.2 Modeling of Cutting Heat and Friction Heat of the Main Cutting Edges 41
• 3.3.3 Influence of Fiber Cutting Angle on Heat Generation 45
• 3.3.4 Heat Partition Model of the Main Cutting Edges 47
• 3.4 Chapter Summary 47
• Chapter 4 Temperature Field Prediction Model 49
• 4.1 Modeling assumptions and governing equation 49
• 4.2 Boundary and initial conditions 50
• 4.3 Coordinate transformation and homogenization 51
• 4.4 Heat conduction model of a micro heat source element 52
• 4.5 Green function solution of the homogenized equation 54
• 4.6 Temperature field induced by moving heat sources 57
• 4.7 Chapter summary 58
• Chapter 5 Experimental Methodology 60
• 5.1 Experimental system configuration 60
• 5.1.1 Ultrasonic machining platform 60
• 5.1.2 Force measurement system 61
• 5.1.3 Temperature measurement system 62
• 5.2 Experimental design and drilling conditions 62
• 5.3 Cutting tools and workpiece materials 64
• 5.4 Thermophysical properties of UD-CFRP 64
• 5.5 Mechanical properties of UD-CFRP 65
• 5.6 Data acquisition and measurement procedure 66
• Chapter 6 Results and discussion 69
• 6.1 Validation of thrust force model 69
• 6.2 Validation of temperature prediction model 72
• 6.3 Error analysis and model uncertainty 73
• 6.4 Temperature distribution characteristics 75
• 6.5 Effect of ultrasonic amplitude 79
• 6.6 Effect of fiber orientation angle 81
• 6.7 Effect of feed rate 83
• 6.8 Three-dimensional temperature field analysis 85
• 6.9 Thermal damage mechanism 87
• 6.10 Engineering implications 89
• 6.11 Thermo-mechanical coupling discussion 90
• 6.12 Chapter summary 91
• Chapter 7 Conclusions and outlook 93
• 7.1 Conclusions 93
• 7.2 Future research directions 95
• References 97
• Abstracts 115