Papers by Author: Chuan Zhen Huang

Abstract: 17-4PH stainless steel is a widely used martensitic precipitation hardening stainless steel, and it is a typical difficult-to-cut material. Residual stress is an important part of the surface integrity. In this paper, superficial residual stress tests of face-milling the 17-4PH stainless steel were carried out at 0.1~0.3 mm/tooth with TiAlN coated carbide inserts. The effects of feed rate on the superficial residual stresses at various cutting speeds were studied. It was found that the residual stresses on the machined surface were very sensitive to the feed rate. The superficial residual stresses at the directions of parallel to and normal to the feed direction both remained compressive and changed obviously in higher compressive direction along with the feed rate. The burnishing effect determined by the cutting force was found to be the primary reason of the residual compressive stresses on the machined surface. The suitable cutting parameters were recommended according to the superficial residual stresses.

Abstract: Micro milling is most flexible to create 3D features for application. However, how to design and fabrication of high precision micro milling tools are one of big challenges for mechanical micro milling. Commercially available micro milling tools are usually simply made from downsizing of macro milling tools, which have negative impact on milling performance. Therefore, in this paper, firstly, various structural of micro milling tools were optimized with abaqus that investigated stress and strain under certain static load on the cutting edges. Then, results showed the minimum stress and strain was a micro hexagonal end mill. Finally, a Ti (C₇N₃) cermet micro hexagonal end mill with a radius of 0.5mm was fabricated by wire electrical discharge machining, and the evaluation experiments for the hexagonal mill have been processed on a micro milling centre.

Abstract: Inconel 718 alloy is a typical difficult-to-cut material and widely used in the aerospace industry. Finite element simulation is an efficient method to investigate the cutting process, whereby a work material constitutive model plays an important role. In this paper, finite element simulation of the cutting process for Inconel 718 alloy using a new material constitutive model for high strain rates is presented. The effect of tool cutting edge radius on the cutting forces and temperature is then investigated with a view to facilitate cutting tool design. It is found that as the cutting edge radius increases, the characteristics of tool-work friction and the material removal mechanisms change, resulting in variation in cutting forces and temperature. It is shown that a smaller cutting edge radius is preferred to reduce the cutting forces and cutting temperature.

Abstract: To grind fused silica in ductile mode, it was proposed to repair surface and subsurface micro cracks of fused silica by CO₂ laser irradiation. However, excessive residual stress remains on the surface because the melt fused silica on the surface quenches in air. It causes the critical depth of cut for ductile grinding fused silica to be smaller than 0.2μm. To investigate the distribution of the residual stress and look for an optimal manner of irradiation to control residual tensile stress, a numerical model of was built for simulating the dynamic behavior of fused silica when irradiated by CO₂ laser. Laser energy absorption, heat transmission, viscoelastic behavior of fused silica and thermally induced stress were considered in the numerical simulation. The results show how the residual stress is formed and distributed. We found that an appropriate control of the temperature field as a function of time and position in the laser process is the key to reduce the residual stress. Therefore, three kinds of processes were proposed to reduce residual tensile stress on the surface of fused silica introduced by laser irradiation. The residual stress distributions of these three processes were compared by numerical analysis to decide a better method of laser irradiation.

Abstract: Abrasive waterjet machining is considered as a promising technique in hard-brittle material polishing. In this paper, The ultrasonic torsional vibration is considered to apply on the workpiece to improve the abrasive waterjet polishing quality and efficiency. The process parameters in the ultrasonic torsional vibration-assisted abrasive waterjet polishing are optimized. The ultrasonic torsional vibration in the role of the abrasive waterjet polishing is investigated. The results show that the application of ultrasonic torsional vibration can effect of abrasive particle movement and increase the critical depth of the ceramic materials.

Abstract: Potassium Dihydrogen Phosphate (KDP) crystal is widely used in laser frequency multiplications and electro-optical modulators, but its soft-brittle property and thermal sensitive characteristic make it a very difficult-to-machine material. In this paper, an in-house made diamond tool with one tooth is used to face-mill KDP crystal specimens on a high-speed micro CNC machining centre, based on a statistically designed experiment. The morphology and roughness of the milled KDP crystal surfaces are analyzed with respect to the process parameters. It has been found that cutting speed has the largest effect on surface roughness, while axial depth of cut and feed per tooth show a comparable effect on both the Ra and PV roughness measures. From this study, 3 m/s cutting speed, 3 μm axial depth of cut and 1 μm/z feed per tooth are recommended for single point diamond milling of KDP crystal.

Abstract: A phase field model of three-phase composite ceramic tool materials with two kinds of nanoparticles is set up in this research. The three-dimensional simulation algorithm is modified and a new efficient algorithm is established. The microstructure evolution of three-phase nanoceramic tool materials is more efficiently and successfully simulated in 200x200x200 unit size. Microstructure evolution of single-phase and three-phase ceramic tool materials is simulated respectively. It can be found that the peak value of grain size distribution for three-phase nanoceramic tool material is smaller than average diameter. It indicates that the nanoparticles not only restrain grain boundary migration, but also prevent the elimination of small grains and refine matrix grains.

Abstract: An automatic test system of airflow performance in refrigerator transportation vehicle is proposed and constructed. The wind velocity field of loading area of empty refrigerated compartment is test in this research. The distribution characteristics of the tri-dimensional wind velocity field are analyzed. The plenty vortex areas in the back part of the recurvature area of the refrigerated compartment is beneficial to the uniformity of the temperature field, the flow fields of the loading area are obviously influenced by vortex areas and the face that the area below the return air inlet is most probably one of the temperature blind angles are concluded.

Abstract: This paper analyzes the reasons of the defects generation of the ceramic cutting tool materials. The defects in the ceramic cutting tool materials are caused by chemical compatibility and physical mismatch during the designing process, and caused by grain abnormal growth and sintering parameters during the preparation stage. The database of low defect ceramic cutting tool is established and the data structure of the database is described. The users can use the database to design the tool material system through the mode that can reduce the defects.

Abstract: Ti(C,N)-based cermets were fabricated by the vacuum hot-processing technique. The effect of sintering process, initial powder size and binder content on mechanical properties of Ti(C,N)-based cermets were investigated. The composite was analyzed by the observation of scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). The results showed that a lower sintering temperature led to insufficient liquid-phase sintering process, which reduced the density of the composite. However, higher temperature and longer holding time resulted in abnormal grain growth, which was not good for improving the mechanical properties of the composite. With the refinement of the initial powder size of the Ti(C,N), the fracture toughness reduced slightly, the flexural strength and Vickers hardness increased. The better mechanical properties were obtained when the binder content of the cermets was designed based on the eutectic composition of Mo-Ni binary alloy phase diagram.