Papers by Author: Wei Zhao

Abstract: With the development of advanced automation degree industries, the requirements of network management for workshop tool become more and more urgent. A very important part in network management system is identification technology of the tool. In this paper, 2D (two-dimensional) barcode identification technology is applied in the tool information in real-time query to realize network management. The 2D barcode reading device, which is combined with the local computer decoding software, could achieve communication between production line and the server. By using 2D barcode identification technology, it could achieve network management for workshop tool, improve production efficiency and reduce the artificial error.

Abstract: Cutting tools play an important role in the cutting process of titanium aircraft components, but it is difficult to comprehensively evaluate the cutting tool performance, so the selection of appropriate cutting tool becomes extremely important. In this paper, an evaluation method using grey relational analysis for cutting tool performance was proposed. Meanwhile, in this method, a test benchmark with some typical difficult-to-machined features extracted from titanium aircraft components was designed, and the processing route was developed. Grey comprehensive evaluation models of cutting tool performance were established for the rough and finish machining respectively. Finally, the grey comprehensive evaluation models were used to evaluate the cutting tool performance in the milling experiments of the benchmarks. The results show that the grey relational comprehensive evaluation method is convenient and effective to evaluate milling tools performance for titanium aircraft components.

Abstract: Titanium alloy is becoming increasingly employed in the aerospace industries due to its good mechanical and chemical properties. As a typical difficult-to-machine material, there are problems of fast tool wear and poor stability of the processing quality in the machining process. Therefore, experiments of high feed milling of TB2 titanium alloy in liquid nitrogen cooling were carried out to measure the cutting force and the cutting temperature. The experimental results showed that under some parameters, liquid nitrogen could decrease the cutting force and cutting temperature in comparison with dry cutting. What’s more, the tool life as well as the surface quality was improved.

Abstract: In order to improve the working efficiency of a manufacturing system, tool life estimation is very essential. In this paper, the dominant factors affecting tool life are analyzed by theoretical analysis. According to the nonlinear relationship between affecting factors and tool life, a tool life prediction model based on BP neural network, which is optimized by genetic algorithm (GA), is built up. 15 network patterns are trained to get the best network structure. The accuracy of GA-BP model is verified through computing and compared with the standard BP model. The results show that GA-BP model prediction value is exactly closed to the expected value of tool life and the prediction accuracy can be improved more than 5% compared than the standard BP model. The model is proved to be accuracy and it can be used as an effective method of tool selection decision.

Abstract: Flank milling was used to machine titanium alloy workpieces, and there would be high residual stresses induced by milling in the superficial layer of the workpieces. Corrode the stress layers gradually and measure the changes of workpiece’s bending deflection during the corrosion process. With reverse thinking, calculate the stress values in the upper layers based on the values in the bottom layers and the changes of the bending deflection. At last, the stress values got by this method are prior to the self-balanced state, so the result rules out the factors of the workpiece’ size and shape. The deformations of workpieces with different sizes and shapes can be predicted accurately based on the stress values got by this method. The correctness of the method has been verified by Finite Element Method(FEM).

Abstract: This paper presents the prediction method of cutting force and dimensional error of Ti6Al4V alloy thin-wall components in end-milling operations. Based on the FEM simulation software and force-model, machining deformation was predicted by two kinds of FEM models, and then compared with the measured data. Results obtained from the proposed models and the tests show that the coupling model of thermal-mechanical having better agreement with the experimental results. Besides, the test results also prove the new tool-path pattern proposed in this paper is useful to reduce the machining error.

Abstract: A strain based dynamometer used for the prediction and measurement of three-component cutting forces for milling operations has been designed on the basis of the principle of additional elastic element theory. Meanwhile, four Wheatstone bridges, considerable amplifier and data acquisition software based on LabVIEW are also used to compose a whole system acquiring the cutting force signals. In order to obtain higher natural frequency and magnification, this paper focuses on the calculation and optimization of the dimensions of the special structure, and finally its first natural frequency can be stabilized at more than 14kHz, which are high enough to precisely measure the cutting forces, and the magnification can also achieve up to 15. The dynamic characteristics of the dynamometer are studied theoretically and experimentally, the results show that the developed dynamometer is able to measure the dynamic force component in high-speed cutting.

Abstract: TC4-DT is a new damage-tolerant titanium alloy. In the paper, a series of experiments on tool wear and surface integrity in high speed milling of the alloy were carried out. The tool lives of different tool materials were studied and the wear mechanism of cutting tools was also investigated. Then surface integrity, including surface roughness, microhardness and metallurgical structure was studied and analyzed in high speed milling at different tool wear status. Results showed that K10 is the most suitable cutting tool after considering a combination of factors. And good surface integrity could be obtained in high speed milling of TC4-DT under all cutting situations. In addition, even with acutely worn stages, there has been no so-called serious hardening layer (or white layer) according to the study of microhardness and metallurgical structure beneath the machined surface.

Abstract: The axial limit cutting depth(LCD) of constant speed were studied, and the stability lobes were gotten by expriments and simulation. The vari-speed milling selected various parameters was investigated by expriments,also.The experimental results show that varying speed milling approach improves the limit cutting depth on proper time and prope parameters selection. According to the comparative analysis of the exprimental results of constant speed and vari-speed milling, it was obtained whether the varying speed milling approach was to be chosen and how to select proper parameters, should be reference to the stability lobes of constant speed.

Abstract: Titanium alloys are known for their strong chemical reactivity with surrounding gas due to their high chemical affinity, especially in dry machining. But it is very difficult to study the influence of surrounding gas on the tool-workpiece interface because of the machining processes’ complexity. In this paper, rotating pin-on-disc friction tests have been carried out at room temperature in ambient air and nitrogen gas to investigate the friction and wear behavior of WC-Co cemented carbide sliding against Ti6Al4V alloy. Scanning electron microscope (SEM) and Energy dispersive x-ray spectroscopy (EDX) have been used to examine the worn surface of the WC-Co pin and Ti6Al4V disc. The result shows that, compared to air, nitrogen gas brings a slight decrease in coefficient of friction, but a significant deduction in wear of the pin and disc. The SEM observation and EDX analysis indicate a distinct difference in wear mechanism between the pin and disc. Severe grooved wear, squeezing, adhering and tearing interactions are the main mechanisms causing the extensive wear of Ti6Al4V disc. Abrasion, adhesion and “pulling out” are the main mechanisms resulting in the wear of WC-Co pin.