Advanced Materials Research Vols. 774-776

Abstract: Austempered Ductile Iron (ADI) is a new generation of cast iron materials developed in recent decades; but its excellent comprehensive mechanical properties make it become hard-machining material. The main objective of this paper is to develop the prediction model of cutting force of ADI based on the BP neural network. The main factors that affect the prediction of cutting force were analyzed with experimental data. The structure of BP neural network and the reasonable training function were determined when experimental data was used to develop the prediction model of cutting force. Prediction error was between ± 4% when the prediction model was used to predict cutting force. The approach to the prediction of cutting force based on BP neural network is valuable for application.

Abstract: This article studies the effect of process parameters on the grindability of Ti-6Al-4V and particulate reinforced titanium matrix composites (PTMCs) comparatively, using the wheels of white alundum (WA) and cubic boron nitride (CBN) respectively. The processing variables, such as grinding force, grinding temperature, specific energy were investigated in detail. The results indicate that the grinding force and temperature with WA wheels were obviously larger than that of CBN wheels. The specific energy of Ti-6Al-4V and PTMCs decreased gradually with the increase in the maximum underformed chip thickness using the two different wheels.

Abstract: The NAK80 die steel was processed in spray etching with mask preprocessing.The effect of the mask gap width and etching depth on the undercut ratio was investigated . The result shows that with the increase of the mask gap width the effect of the etching depth on the undercut ratio increases. Based on the experiment, the relation of the mask gap width, the etching depth and the undercut ratio is obtained.

Abstract: In this report, our attention was paid on the tool wear due to the stop of tool-feed, caused by change from the automatic operation to the manual one in the lathe work, because it was thought that skill level of workers influences the tool wear significantly. First, the workers gaze-point movement was recorded with an eye camera and analyzed with the application software. The results showed that the stop time of the tool-feed for skilled workers was very shorter than that of beginners. Then, the relationship between the tool-feed stop time and the tool wear was investigated by using an NC lathe. It was found that the shorter the stop time is, the smaller the tool wear becomes. Based on the above findings, the influence of the skill level on the tool wear due to the tool-feed stop in lathe work was revealed and key issues in the skill transfer of lathe work were confirmed.

Abstract: This paper discusses the plastic limit load of elbows without defects and with local thinned area (LTA) in the extrados under combined pressure and in-plane closing bending moment. Finite element analysis (FEA) and experiments have been used. The results of FEA show that, for the elbows without defects, when the ratio of pressure to the limit pressure (P/PL) is smaller than 0.469, the limit moment of elbows increases with the increasing pressure; when the ratio (P/PL) is bigger than 0.469, the limit moment of elbow decreases with the increasing pressure. For the elbows with LTA, the FEA results show that with different LTA the variation of the limit load of elbows to the pressure is different. Perhaps, the limit moment of elbows always decreases with the increasing pressure. It is also likely that the limit moment of elbows increases with the increasing pressure and then decreases with the increasing pressure. The results of FEA are consistent with the experimental results. By fitting the results of FEA, the safety assessment figure for elbows under combined pressure and in-plane closing bending moment is drawn.

Abstract: Micron-sized WC-CrCNi powder (WC-metal powder, WC 68%, C 0.56%, Cr 21% Ni 6%) was coated onto magnetic shaft material Inconel718 (In718) surface using HVOF thermal spraying equipment for the improvement of the surface properties of the shaft. During the HVOF coating, metal carbides, such as WC and Cr₇C₃ decomposed to W₂C, metals and free carbon. The free carbon and the excesively sprayed oxygen formed carbon oxide gases and thus produced pores and voids in coating. The optimal coating process (OCP) that produced the lowest coating surface porosity and the highest surface hardness was determined by the Taguchi experimental program of nine processes for four spray parameters with three levels. Coatings with porosity 1.20±0.1% and hardness 1150±60 Hv were prepared using optimal coating processes. The coating was porous, but the hardness was improved approximately three times from 400±10 Hv (In718) to 1150±60 Hv (coating). Friction coefficients (FC) of the coating were lower compared with In718 at both 25°C and 450°C. FC decreased with increasing temperature from 25°C to 450°C for both In718 and the coating. Wear depths of coatings were smaller than those of In718 at both 25°C and 450°C. For the improvement of the surface properties and durability of the magnetic shaft, HVOF WC-CrCNi power coating was recommended.

Abstract: PAN-based carbon fibers (CFs) were oxidized in a static electrochemical oxidation process. The surface color and chemical composition were investigated by means of digital camera and XPS. The results showed that, with the increasing distance from anodic roller, the surface color of CFs changed and the degree of oxidation got weaker and weaker. A close correlation was found between its surface color and chemical properties. It indicates that the electrochemical oxidation performance of one kind of carbon fiber can be handily studied using static electrochemical oxidation process because we can get CFs of different degree of oxidation through one experiment.

Abstract: With the accuracy improvement of twin-screw compressor rotor machining, higher requirement of crew rotor grinded equipment and grinding process is put forward. Based the theory of screw grinding and CNC forming grinding wheel dress technology, the relationship between machine working parameters, CNC grinding wheel dressing parameters and screw rotor grinded process parameters are investigated, and the relationship between CNC grinding wheel dressing parameters and the screw rotor grinded process parameters is established, and its formulas are presented to describe the distances between grinding wheel axis and screw rotor axis. Through these formulas, the CNC wheel dressing program could be designed easily, the performance and efficiency of machine would be improved, and especially the machining quality of screw rotor would be enhanced and becomes more stability.

Abstract: For investigating the effect of ultrasonic treatment on the cooling and lubricating action of cutting fluid, an ultrasonic treatment system of emulsion fluid was developed to be used in cutting experiments. And the comparison experiments were carried out with YT15 tool turning 45 steel, under the conditions of dry cutting, fluid and ultrasonic treatment fluid. The results show that as ultrasonic treatment one used cutting forces decrease about 10%-15% and 5%-10% to dry cutting and fluid; the cutting deformation coefficients reduce too; and the machined surfaces are enhanced. Therefore, the cooling and lubricating performances of the fluid are improved by ultrasonic treatment. As a result, the using quantity of emulsion fluid would reduce indirectly, and this help to energy saving and emission reducing.

Abstract: The formation of residual stresses in the vicinity of a single defect of continuity in the process of intense impulse loading surface with considerable distance from the defect is examined. Modeling is carried out within the framework of large elastic-plastic deformation. In the vicinity of the defect there is level of stress, leading to its elimination.