Key Engineering Materials Vols. 589-590

Abstract: Whirlwind hard milling is a new high-efficient and environmental technology for maching process ballscrew thread. Thermal elongation of the workpiece in processing is one of the main reasons causing the screw-pitch error. The screw-pitch error due to thermal elongation caused by milling heat were analyzed . The dynamic temperature distribution simulation and thermal elogation of the workpiece were carried out with ANSYS software.Compared the simulation results with measured temperature during processing of the workpiece,the temperature distribution pattern is consistent.The result indicate that the law of thermal elongation of the free end and unprocessed section of ballscrew simulated by ANSYS is helpful to compensate screw-pitch error caused by thermal elogation.

Abstract: This paper performed a series of experimental investigations for typical die steels with ultrasonic vibration assisted turning. The micro-morphology of rake face and flank face of diamond was detected by scanning electron microscopy, and the roughness of machined surface was measured by Form Talysurf. In order to clarify the influence laws of cutting parameters and tool geometric parameters on tool wear and surface quality. The results revealed that the wear of diamond and surface roughness rely heavily on the feed rate, and have less relativity with the relief angle and the depth of cut to an extent. In addition, the function mechanism of ultrasonic vibration turning had been analyzed, it exhibited that this technological measure has enhanced tool life and improved surface quality to a large extent.

Abstract: For most of materials, a chip transformation from continuous to serrated takes place at a relative high cutting speed which is called the critical cutting speed (CCS). Serrated chips at CCS have different characteristics from those at higher cutting speeds. In this paper, the chip transformation is analytically investigated. The deformation in the primary shear zone (PSZ) during the transformation is analyzed. The critical shear strain at CCS for chip transformation is proposed. Cutting Experiments are carried out with four metals, and metallographical and morphological investigations on the chip transformation are conducted. The results show that serrated chips can be produced if the shear localization along a shear plane occurs before the shear plane reaches to the middle of PSZ. At CCS, the flow stress of the shear plane passing through the PSZ reaches maximum at the middle of PSZ and then decreases with further straining. The high thickness of localized shear bands makes the serrated chip at CCS look as a wave. At CCS, the shear strain of chip segments is approximately equal to the critical shear strain for chip transformation. Influences of material hardess (brittleness) on chip transformation are also discussed.

Abstract: The constitutive relationship of GH4169 superalloy was investigated. The grinding thermal load acting on GH4169 workpiece in grinding process with conventional aluminum oxide wheel was determined by using the method combining finite element method (FEM) with experiment. The grinding temperature field and grinding thermal residual stress generated in GH4169 were calculated via finite element method (FEM). Finally, the relation between grinding parameters and grinding temperature field and that between grinding parameters and thermal residual stress were discussed.

Abstract: The silicon carbide reinforced aluminum matrix composites (SiCp/Al) are widely used for its high specific stiffness and high specific strength. However, the poor surface quality and machined surface defects limit its further application. The aim of this paper is to investigate the effect of cutting parameters on the machined surface defects in high-speed milling of SiCp/Al composites. The tests were performed on a high precision computerized numerical control (CNC) precision milling machine using a polycrystalline diamond (PCD) tool, and the machined surfaces were measured by the scanning electron microscope (SEM).It was found that cutting parameters have a great influence on the depth of big pits. A high feed rate and a low cutting speed correspond with a big cutting force, and result in a large depth of big pits.

Abstract: This paper investigates the surface integrity of premium thread gauge material 9Mn2V in reciprocating surface grinding using SG abrasive, which includes metallographic structure for grinding crack, specific grinding energy and surface residual stress. The specific grinding energy and the surface residual stress can be reduced after the workpiece gets tempered, so small grinding depth can lead to the generation of cracks when the workpiece is not tempered. Otherwise, the depth of heat affected zone increases with the increase of grinding depth, but not increases proportionally. After 9Mn2V is tempered, the occurrence of grinding burn and grinding cracks can be improved.

Abstract: The high temperature strength of Ni-based superalloys coupled with excellent corrosion resistance make them ideal for aerospace applications. However, the difficulty in finish machining superalloys with the carbide tools presents the short tool-life. Polycrystalline Cubic Boron Nitride (PCBN) is potential to machine superalloys. To data, there are many researches about PCBN tool wear, but only little papers showing how the surface roughness and the wear speed are influenced by cutting parameter and the coolant during the differences periods of PCBN tool wear. This investigation has been conducted to show that the PCBN tool wear is slower with cooling that without cooling during cutting superalloys with PCBN tool especially in VB up to a certain value. It is shown that tool fracture can be reduced by using the cooling. In the process of PCBN tool wear, in addition, there are some differences of the effect of the cooling for roughness Ra values.

Abstract: The influence of stretched fixation on face milling-machined 6061T6 aluminum alloy, a widely used material in industry, was investigated in the paper. A unidirectional stretched fixture was designed and used in the face milling experiments. During the experiments, the pre-stress exerted on the work-piece increased from 0 to 220MPa with other machining parameters being constant. Surface topography, surface residual stress and flatness were measured. The results reveal that stretched fixation has significantly effect on residual stress, machined surface flatness, and roughness.

Abstract: The water soluble grinding fluids (coolants) with 3M^TM Trizact^TM Diamond Tile（TDT）used in thinning process of the flat glass contains lubricants, extreme pressure antiwear agents, surfactants and anti-rust additives, which are expected to provide the functions of lubricating, cooling, cleaning, anti-rust. The results showed that the water soluble grinding fluids can improve the processing performance of 3M TDT effectively, keep excellent self-sharpening, increase processing efficiency, extend the service life of the abrasive pads and reduce surface roughness of the glass .

Abstract: According to subject needs, this article considers both processing time and production costs as the objective function. And it gets the mathematical model of the system regarding cutting force, machine power, machining accuracy and tool life as constraints. The system is developed by Visual C++ 6.0 and SQL Server 2000. The database gets reasonable cutting parameters by Hybrid Reasoning. What’s more, the system optimizes the cutting parameters by using Artificial Bee Colony algorithm further. And the optimization results have been verified its correctness.