In the aviation industry, flexural distortion of thin-walled aeronautic parts after machining processes is inevitable, especially for high-strength aluminum alloy. To satisfy the accuracy requirement for subsequent assembly processes, the distorted parts have to be corrected. Bilateral rolling operation has been proved to be an effective method for correcting the flexural distortion. However, this method is generally based on trial and error, and the quality of distortion correcting cannot be guaranteed. To solve this problem, finite element method (FEM) was first adopted to investigate the distortion feature after bilateral rolling process for T-shaped structures. The relationship between processing parameters and maximum deflection was then studied. An equivalent bending moment method was proposed to represent the effects of bilateral rolling on micro-plastic deformation and residual stresses. Besides, a theoretical model was established for distortion prediction. Furthermore, based on simulation results, the calculation formula of the equivalent load was deduced. Finally, the theoretical model and the equivalent bending moment method were verified by rolling correction experiments, which were used to calculate the rolling correcting load (rolling depth). The results show that the average reduction rate of deflection is 73.5%. This paper provides an effective theoretical model for predicting the correction load in rolling correction process for thin-walled aeronautic parts.

Titanium alloys are attractive materials for aerospace, biomedical and chemical engineering due to their excellent combined performance of high specific strength and fracture resistant characteristics. Drilling titanium alloys is essential to the bolted/rivet connection in the assembly of aerospace parts. This paper outlines a comprehensive analysis of drilling characteristics and hole quality/integrity assessment following drilling titanium alloy Ti6Al4V without coolant under different machining parameters. The experimental results show that hole quality can be improved by proper selection of cutting parameters. This is substantiated by monitoring thrust force, hole diameter, circularity, chip formation, and surface finish. It was observed that the thrust force increased rapidly with respect to feed rate, which was increased by 2.5 times when the feed was increased from 0.05 to 0.13 mm/r as a constant cutting speed of 40 m/min. In addition, the circularity was found to be around 4 μm at low feed rate, when the feed was increased the circularity increased to 10 μm. The experimental results also indicated that the shape and the size of chips were strongly influenced by feed rate. Observation on the subsurface of drilled workpiece indicated a severe plastic deformation under different cutting conditions. This study demonstrates that using proper process parameters plays an important role in improving machining efficiency and guaranteeing quality in dry drilling titanium alloy.

Ultrasonic surface rolling process (USRP) is an effective method to improve material surface quality, such as surface finish, microstructure, and stress state. Previously, USRP is usually used in comparably hard materials (e.g., instance steel and titanium alloys). In this paper, attention is focused on low hardness aluminum alloy which is widely used in the aviation industry. Aluminum alloy 7050-T7451 is used to investigate its surface characteristics in the ultrasonic rolling experiment. With the aid of surface optical profiler, X-ray stress analyzer, scanning electronic microscope (SEM), and energy-dispersive spectrometer (EDS), the differences of surface characteristics are explored in the USRP-treated area and that of the turning area. In addition, the influence of feed rate on surface integrity is also investigated. The results show that surface integrity is improved by USRP, and the best quality is obtained with the feed speed of 0.10 mm/r. Under the optimal experimental condition, surface roughness (Ra) is reduced to 0.059 μm, axial and tangential surface compressive residual stress is increased to −130.6 and −330.8 MPa, respectively, and surface microhardness is increased by 41.3 %. Metal flow traces, fusion of surface grain boundary, and the phenomenon of impurity phase diffusion are observed in the cross section of the treated specimen. The internal strengthening mechanism of the USRP-treated surface is probed.

Temperature is a key factor that affects the quality of carbon fiber reinforced polymer (CFRP) cutting. Degradation of resin will occur within the machined surface or surface layer with the temperature rise. In this research, the temperature rise under the condition of line heat source in high-speed movement was analyzed, and it was found that the thermal conductivity in different fiber orientation is a key factor for the rise of cutting temperature. Based on the analysis of the thermal conductivity in different fiber orientation, the relationship between cutting temperature and fiber orientation was evaluated. Verification experiments were designed to capture the signal of cutting temperature using the tool-workpiece thermocouple technique. The influence of cutting temperature on machining quality was also studied with scanning electron microscope (SEM). Degradation of resin is occurred within the machined surface or surface layer when the cutting temperature exceeds the glass-transition temperature (Tg).

The cutting temperature and cutting force are some of the main factors that influence the surface quality of carbon fiber-reinforced polymer (CFRP). However, few investigations have been done on cutting temperature because it is difficult to capture the dynamic response of the temperature measurement system. Degradation of resin will occur within the machined surface or surface layer as the temperature exceeds the glass-transition temperature of the resin matrix. In this research, the relationship between cutting parameters and cutting temperature, cutting force were developed by response surface methodology (RSM). The experiments were designed using the tool-workpiece thermocouple technique. Taking into consideration the effect of the glass-transition temperature, the influence of cutting force and cutting temperature on surface quality of CFRP was analyzed. Analysis results showed that Spindle speed is the key parameter which influenced the cutting temperature while feed rate is the key parameter which influenced the cutting force in milling of CFRP. When the cutting temperature exceeds the glass-transition temperature (Tg), the matrix cannot provide enough support to the fibers, and the machining quality of composite material is poor.

Titanium alloys are widely utilized in aerospace, automotive, biomedical and chemical engineering, etc., thanks to their excellent combination of high-specific strength, fracture, corrosion resistance characteristics, etc. However, titanium alloys are difficult-to-machine materials. Tool wear is one of the bottlenecks restricting their machining efficiency. A systematic study on the relationships among tool wear, chip morphology, and cutting vibration is inadequate. In this study, chip morphology and cutting vibration characteristics under different tool wear stages are examined using optical microscope, SEM, and vibration test system. The mechanism of tool wear in end milling titanium alloy is also investigated. Results indicate that with the progression of tool wear, the chip segment degree becomes more and more serious. The mechanism for this phenomenon is probed. Tool wear progression enlarges the cutting vibration which causes the friction force on tool/chip interfaces to increase, and this aggravates chip edge wear accordingly. On the contrary, the increase of chip segment degree induces the progression of cutting vibration and tool wear. Therefore, the aim of the present research is to investigate the sophisticated relationship. This will benefit for improving cutting efficiency and guaranteeing machining quality in end milling titanium alloy.

Laser cladding, which can increase the hardness and wear resistance of the used components, is widely used in remanufacture and sustainable manufacturing field. Generally, laser cladding layer should be machined to meet the function as well as the assembly requirements. Milling is an effective means for precision machining. However, there exist great differences of physical and mechanical performances between laser cladding layer and substrate material, such as microstructure, hardness, mechanical properties, etc. This produces some new milling problems for laser cladding layer. An insightful understanding of milling mechanism of laser cladding layer is inevitable. There still lacks the research on this subject, such as chip morphology and mechanical behavior, vibration during laser cladding layer milling process, etc. Thus, the change of chip morphology depending on the cutting parameters and microhardness variation was studied. Signal analysis methods of time and frequency domains of cutting forces and machining vibration were used to evaluate the milling characteristics of laser cladding layer. The microstructural analysis indicates that shear-induced lamella structures are the basic features for the chip free surface. The height-to-thickness ratio of saw-tooth chips increases with increasing cutting speeds and feeds. Microhardness profiles on the top surfaces of machined chip decrease from the back surface to the bulk chip, and the shear band shows increased hardness. The cutting force and machining vibration acceleration of laser cladding layer are higher than those of the KMN steel substrate at the same cutting parameters. The machining vibration is characterized by high vibration in the intermediate position of each layer and low vibration in the joint surfaces between layers.

Helical groove geometry has important influence on the performance of end mills. It is the hardest and most time-consuming grinding process in end mill manufacture. This paper reports a graphical analysis method to obtain the structure parameters and geometric shapes of helical grooves with the known wheel geometry and position. Mathematical models are presented to describe the wheel geometry and position (including orientation and location) in space. A family of wheel surfaces is calculated and a scattered point set in the cross section plane is deduced according to the grinding path. Finally, an original algorithm for the cross sectional outline profile identification is given using graphical method. To verify this method, a calculation program programmed using MATLAB programming is developed. This study provides a fundamental understanding for the groove grinding process, based on this, the influence of different grinding process parameters on groove geometry (including radial rake angle, groove width and core radius) is discussed.

An investigation was reported on the cutting temperature in milling Ti6Al4V by applying semi-artificial thermocouple. ANOVA was conducted on the experimental results, and regression models were obtained. Analysis results showed that the tool temperature and workpiece temperature performed a similar rising trend with the increase of cutting parameters, including cutting speed, feed rate, radial feed, and axial feed. And their influence degrees decreased successively. The cutting force with different cutting parameters was also measured, and the relationship between cutting temperature and cutting force was discussed. It was found that cutting temperature and cutting force obtained in the experiment had the same fluctuation feature. Therefore, the cutting force and cutting temperature could complement each other for monitoring and analysis of the cutting process.

Clearance of end mills has great impact on the performance of milling, and therefore a high demand for its machining theory and process is put forward. Based on the analysis of practical machining process, enveloping theory, principles of spatial geometry are introduced to establish the clearances processing model, as well as considering the geometries, orientations, and locations of wheels used to machine the clearances with convex, eccentric, or elliptic shapes. Accordingly, limitations of wheel geometry and location to machine a desired clearance are discussed. A commercial computer aided design system with API function programming is used to visualize the machining process. The solid model is finally obtained.