Xiaoxiao Chen

Bio: Xiaoxiao Chen is an academic researcher from Shandong University. The author has contributed to research in topics: Machining & Surface roughness. The author has an hindex of 12, co-authored 36 publications receiving 449 citations. Previous affiliations of Xiaoxiao Chen include Chinese Academy of Sciences.

A review on the recent development of incremental sheet-forming process

Abstract: This paper presents a detailed literature review on the current research of incremental sheet forming relating to deformation mechanism, modelling techniques, forming force prediction and process investigations. First, a review of the fundamental deformation mechanism and formability in incremental sheet forming (ISF) is provided. Subsequently, the modelling techniques for ISF are reviewed and categorised into two approaches: analytical modelling and finite element modelling. Special interest is given to a critical review regarding the forming forces analysis and prediction during the process. Then, previous publications related to geometric accuracy, surface finish and forming efficiency in ISF are reviewed. Finally, several potential hybrid incremental sheet-forming strategies are discussed. This leads to a statement of conclusion which may act as an inspiration and reference for the researcher.

Experimental investigation on chip morphologies in high-speed dry milling of titanium alloy Ti-6Al-4V

Abstract: An experimental investigation of chip morphologies in high-speed dry milling of Ti-6Al-4V alloy was conducted over a variety of different cutting conditions. Observation on the multi-view characterization of the chips was carried out which includes free surface, back surface, and cross-section of top surface. Structure and shape alterations of the free and back surfaces were analyzed using an optical microscope and a scanning electron microscope (SEM). The microstructural analysis indicated that the chip morphology when dry milling Ti-6Al-4V alloy in high-speed range exhibited a serrated shape for a wide range of cutting conditions. The degree of chip serration is more pronounced and evident with the increase in cutting speed, feed, and depth of cut. A significant variation in the microstructure of the chip including the thickness of the shear bands and the serrated tooth structure for different cutting speeds has been identified. The higher chip serration ratio (CSR) in high cutting speed range may facilitate appropriate machining condition for the occurrence of well-broken chips. Moreover, chip formation takes place by the mechanism of catastrophic thermoplastic shear from the observation of the shear bands using metallurgical analysis techniques. X-ray diffraction results indicated that no evidence of phase transformation was found in the shear localized chips. The variation in chip serration and metallurgical microstructure inside the shear bands and the tool/chip contact zone should be attributed to the reinforcement of coupled thermo-mechanical behavior in the cutting process with the increase in machining parameters.

Force coefficients identification considering inclination angle for ball-end finish milling

Abstract: The slotting experimental method is not applicable for force coefficients identification considering inclination angle in ball-end finish milling. A new experimental method for force coefficients identification considering the inclination angle is proposed in this research. In this method, the start and exit radial immersion angles φst and φex in any cutting conditions are modeled based on different inclination angles. Based on the research of Gradisek et al., contrary to the slotting experimental method, the position of the cutting element on a ball-end mill edge could be approximately regarded as the only factor that affects the cutting force coefficients. Experiments have been conducted to calculate the cutting force coefficients based on the new method and slotting method respectively. The results show that, for finish milling, the new experimental method for force coefficients identification is better than the slotting experimental method.

Mechanical properties of nanomaterials: A review

Abstract: Abstract As an emerging material, nanomaterials have attracted extensive attention due to their small size, surface effect and quantum tunneling effect, as well as potential applications in traditional materials, medical devices, electronic devices, coatings and other industries. Herein, the influence of nanoparticle selection, production process, grain size, and grain boundary structures on the mechanical properties of nanomaterials is introduced. The current research progress and application range of nano-materials are presented. The unique properties of nano-materials make them superior over traditional materials. Therefore, nanomaterials will have a broader application prospect in the future. Research on nanomaterials is significant for the development and application of materials science.

Improvement of machinability of Ti and its alloys using cooling-lubrication techniques: a review and future prospect

Abstract: Products made of titanium and its alloys are widely used in modern areas like the mechanical engineering, instrument making, aerospace and medical sector. High strength and low thermal conductivity are the causes of difficulties with the machinability of these alloys. It is important to find ways to increase machinability by cutting titanium alloys. One way to implement this is to apply various methods of cooling on workpieces of titanium alloys and on cutting tools during machining. In this review article, an extensive analysis of the literature on such cooling techniques as dry, conventional cooling system, minimum quantity of lubricant (MQL), minimum quantity cooling lubrication (MQCL), cryogenic lubrication, and high-pressure cooling (HPC) is performed. The following groups of Ti alloys are considered: high-strength structural and high-temperature Ti alloys, intermetallic compounds, pure titanium, as well as composites CFRPs/Ti alloys. For the processes of turning, milling, drilling, and grinding, etc. it is shown how the type of cooling affects the surface integrity include surface roughness, tool wear, tool life, temperature, cutting forces, environmental aspects, etc. The main advantages, disadvantages and prospects of different cooling methods are also shown. The problems and future trends of these methods for the machining of Ti and its alloys are indicated.

Application of signal to noise ratio and grey relational analysis to minimize forces and vibrations during precise ball end milling

Abstract: In this paper, a method for the minimization of cutting forces and vibrations during precise ball end milling of hardened 55NiCrMoV6 steel is developed. The aim of this work concentrates on the optimal selection of surface inclination angle α and tool’s overhang l, which enables the minimization of cutting forces and vibrations in order to improve the machined surface quality. The experiment includes the measurement of cutting forces and acceleration of vibrations during the milling tests with variable input parameters. The next step focuses on the optimization of the ball end milling process with the consideration of the acquired signals. This procedure is carried out by the minimization of process responses with the application of signal to noise S/N ratio and grey relational analysis (GRA). Subsequently, the obtained optimal values of process input parameters are validated during the ball end milling tests involving the measurements of machined surface topographies. Research reveals that surface inclination angle and tool’s overhang have significant influence on generated forces and vibration values. Moreover, the selection of the optimal values of α and l enables significant improvement of machined surface quality.

Investigations on machinability aspects of hardened AISI 4340 steel at different levels of hardness using coated carbide tools

Abstract: This study investigates the effect of workpiece hardness, cutting parameters and type of coating (coated tool) on different machinability aspects like, the tool life, surface roughness, and cutting force and chip morphology during turning of hardened AISI 4340 steel at different levels of hardness. Cutting forces observed to be higher for harder workpiece and for CVD applied multi-layer MT-TiCN/Al 2 O 3 /TiN coated carbide tool. Better surface finish observed for harder workpiece and for PVD applied single-layer TiAlN coated carbide tool. However, better tool life obtained by CVD coated tool can be attributed to its thick coating and the protective Al 2 O 3 oxide layer formed during cutting, which has protected the tool from severe abrasion at elevated temperatures. Modified Taylor tool life equation indicated that the workpiece hardness followed by the cutting speed and depth of cut as the most influencing factors on tool life. The better performance of CVD coated tool under study is obtained by limiting the cutting speed to 300 and 180 m/min for workpiece hardness of 35 and 45 HRC, respectively. However, the upper limit is of 200 m/min when using PVD coated tool. It has been observed that the tool wear form and the wear mechanism(s) by which the tool wear occurred are influenced by the workpiece hardness, cutting conditions and the type of tool.