Papers by Author: Shen Yung Lin

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Authors: Shen Yung Lin, Y.C. Liu, C.W. Huang
Abstract: This study performs an experiment to investigate the effect of process variables such as rotational cutting speeds of the wheel, feed rate of the work-table and grinding depth of cut on surface roughness and the fluctuations of grinding forces for Ti-6Al-4V titanium alloy. STP-1623 ADC surface grinding machine, grinding wheel with CBN material sintering and Ti-6Al-4V titanium alloy workpiece are used in the experiment. The roughness of the grinding surface was measured by the roughness measuring instruments and the fluctuations of grinding forces were measured through dynamometer after each surface layer ground from the workpiece in the experiment. The grinding performance can be ascertained from the signal fluctuations phenomena of the grinding forces both along normal and tangential directions, which may also be utilized as an index for the quality of surface finish judgment. The results show that excellent surface quality being always consistent with the stable grinding force fluctuations and can be obtained under the conditions of slow feed rate of the work-table, high revolutions of the wheel and shallow depth of cut.
237
Authors: Shen Yung Lin, Y.Y. Cheng, C.T. Chung
Abstract: First, a 2D orthogonal cutting model for titanium alloy is constructed by finite element method in this study. The cutting tool is incrementally advanced forward from an incipient stage of tool-workpiece engagement to a steady state of chip formation. Cockroft and Latham fracture criterion [1] is adopted as a chip separation criterion. By changing the settings of cutting variables such as cutting speed, depth of cut and tool rake angle to investigate the chip formation process and the variation of cutting performance during titanium cutting simulation. The changes of chip type, cutting force, effective stress/strain and cutting temperature with different cutting condition combinations are thus analyzed. The result demonstrates that the serrated chip type is obviously produced when cutting titanium alloy. Next, water-based and oil-based cutting fluids are employed in conjunction with proper cutting parameter arrangements to perform up-milling experiments. By measuring the cutting force, surface roughness and tool wear to investigate the effect of these combinations of milling variables on the variation of cutting performance for Ti-6Al-4V. The chip shape and cutting force obtained from the experiment are compared with those calculated from simulation. It is shown that there is a good agreement between simulation and experimental results.
1062
Authors: Shen Yung Lin, Y.C. Fang
Abstract: The accuracy and surface roughness of a machined component is strongly dominated by the dynamic characteristics of the machine tool while the most important factor related to precision machining is the dynamic behaviors during cutting processes. The main objective of this study is to develop a thermo-elastic-plastic coupling dynamic cutting model under large deformation for precision machining and so that the model can be used to predict several variations of cutting mechanics variables. The flow stress in the model is considered as a function of strain, strain rate and temperature and the critical value of the strain energy density of the workpiece is utilized as a chip separation criterion. A powerful FEM software is adopted to create a complete numerical solution for this model. During the analysis, the cutting tool is incrementally advanced forward in a step-by-step manner, from an incipient stage of tool-workpiece engagement to a steady state of chip formation. Three different dynamic cutting processes are introduced in this study, i.e., wave cutting, wave removing and wave on wave cutting. Various levels of frequencies, of amplitudes and of phase angle associated with different kinds of sinusoidal surface waviness are arranged during each simulation case. A whole simulation of dynamic cutting process is undertaken and the fluctuations of the dynamic cutting force during each dynamic cutting process are determined.
265
Authors: Shen Yung Lin, S.H. Yu, M.L. Wu
Abstract: Different materials coated on milling tools (tungsten carbide) such as TiCN, TiAlN, TiN and DLC are integrated in this study for the analysis of cutting performance such as tool wear, surface roughness and noise induced in high-speed machining of mold steels such as NAK80 and SKD61 under different combinations of cutting conditions. The study attempts to find out the advantages and adaptabilities in various coating materials being suitable for which cutting circumferences with specific performance request. High-speed milling experiments of NAK80 and SKD61 mold steels with four materials coating tools were carried out in the laboratory. The tool wear was measured through the toolmaker’s microscope and the roughness of the machined surface was measured by the roughness measuring instruments after each surface layer was removed from the workpiece in the experiment. Besides, the noise-mediator was used to detect cutting noise during each surface layer workpiece removing of high-speed milling process, and the curl chips removed from the workpiece were also collected for the result verifications. Good surface quality and small amount of tool wear can be achieved under the cutting conditions of high-speed revolutions, small feed rate and small depth of cut for four materials coating tools. From the observations of the annealing temperature from the removed chips and the analysis of the cutting noise levels, TiAlN material coating tool has the better tool life and it is suitable for rougher high-speed machining, while DLC material coating tool only has a good surface roughness in shallow cut and hence it is not suitable for high-speed machining of mold steel with excellent cutting performance request.
1026
Authors: Shen Yung Lin, C.T. Chung, R.W. Chang, C.K. Chang
Abstract: The main objective of this study is to investigate the effect of bearing preloads on the characteristics of spindle stiffness. Finite element model for spindle-bearing system is established enabling the variation of spindle stiffness calculations under different bearing preloads. On the other hand, the spindle stiffness may also be obtained from the experiment and its result may be utilized to validate the numerical calculations. The front-end section of spindle is acted by poise weights at different directions, and their corresponding deformations are measured through dial indicator. Three bearing preload conditions, i.e. light, medium and heavy preloads are selected, which are imposed on the bearing to investigate the spindle stiffness variation, respectively. In addition, the effects of the geometrical parallelism error at the end surfaces of spacer due to the manufacturing tolerance or some imperfection on the spindle stiffness are studied. Finally, the impact test on the spindle-bearing body is performed by hammer and the corresponding vibration signal on the spindle surfaces is acquired by accelerometer. The spindle stiffness may be reflected in the other manner through the signals processing by spectrum analysis.
9
Authors: Shen Yung Lin, C.K. Chang, C.T. Chung, F.C. Hsu, C.C. Wang, Yuan Chuan Hsu
Abstract: This paper presents the use of vibration measurement in conjunction with spectrum signal analysis to investigate the vibration phenomena and the dynamic response of the absorber system frame and rigid axle of a vehicle body under real road-driving conditions. Ford 1.6L sedan was selected as the vehicle body to carry out the experiments with different driving speeds. B&K PULSE dynamic signal analyzer was used to detect the vibration signal induced from the absorber system frame and rigid axle of the vehicle body in motion. The acquired on-line signals are then processed through the Fast Fourier Transform using the power spectrum density, the cepstrum method, and the overall analysis. The vibration energy attenuated from the absorber system is analyzed by comparing with that on the rigid axle excited from the road conditions corresponding to different driving speeds. Furthermore, the effects of various road conditions and driving speeds on oscillation of the vehicle body are studied. The corresponding results may be extensively treated as a guiding reference of the absorber system design and manufacturing for those vehicle manufacturing companies.
482
Authors: Shen Yung Lin, C.M. Chang, Ruey Fang Shyu
Abstract: The objective of this study is to construct the forming rule for hourglass-like tube with magnesium alloy during hydro-forming and offer the analysis results as a guideline for magnesium alloy forming in industry. AZ31 magnesium alloy circular tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the hourglass-like tubing products. A finite element based code is utilized to investigate the forming characteristics of hourglass-like tube forming, by changing process parameters such as punch velocity, hydraulic pressure gradient and tool-workpiece interface friction etc. to investigate the material flow of tube filling, wall thickness variations, and stress and strain distributions. And the abductive network is in turn applied to synthesize the data sets obtained from the numerical simulations. Consequently, a quantitative prediction model is developed for the relationships among the process variables, corner radius and minimum tube thickness in the process of hourglass-like tube hydro-forming with magnesium alloy. The results show that proper mechanical force can help material flow, prevent large strain deformation from falling into the area of negative strain hardening rate, enhance the magnesium alloy to become easy in forming and make tube fitting may to be formed successfully.
489
Authors: Shen Yung Lin, C.M. Chang, C.K. Chang
Abstract: Due to the light weight and electromagnetic interference shielding capabilities in magnesium alloy material, it is widely utilized in 3C electronic components and automobile parts. However, its formability is very poor due to the phenomenon of negative strain hardening rate appearing as the deformation in large strain range, so it is usually formed as die casting or casting styles leads to much scrap, and manufacturing cost is thus increased. The objective of this study is to investigate the effect of process parameters on T-shape tube hydro-forming characteristics for magnesium alloy and it may offer the data resulting from the analysis to predict an acceptable product of tube fitting for magnesium alloy forming in industry. AZ31 magnesium alloy tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the T-shape tubing products. Finite element code DEFORM-3D is adopted to investigate the forming states of T-shape tube forming, by changing process parameters; such as punch velocity, hydraulic pressure, fillet radius of the die and tool-workpiece interface friction etc. to investigate the material flow of tube fitting, wall thickness variations, and stress and strain distributions. By qualifying the forming processes whether if it is completed or not, and synthesizing the overall analysis and judgment, we establish an admissible level of process parameter range for complete tube manufacture. The results show that suitable mechanical force can help material flow, prevent large strain deformation falling into the area of negative strain hardening rate, enhance magnesium alloy to become easy in forming and make tube fitting to be formed successfully.
973
Authors: Shen Yung Lin, S.H. Cheng
Abstract: High speed machining is very popular and widely used in industry recently, and it has been accepted as a key technology for die and mold steel manufacturing because it has much advantage as compared with conventional machining such as low cutting resistance, low cutting heat generation and high production rate, etc. The finite element method is utilized in this study to simulate the processes of chip formation during high speed machining of SKD11 die steel workpiece step by step from an incipient of tool-workpiece engagement to a steady state of chip formation. The effects of different combinations of cutting conditions such as cutting velocity, feed rate, rake angle and nose radius of the tool on the curly types of chip formation are investigated thoroughly for establishing the related skill for high speed machining or for predicting the chip morphology in advance.
1009
Authors: Chen Hua She, Jian Yu Lin, Shen Yung Lin
Abstract: To develop the numerical control program of mill-turn machine, the traditional method is to apply the computer-aided design and manufacture software to construct the geometric model, then to generate tool path and convert the path to NC program. For complex numerical control program of mill-turn machine, such as the multiple turret synchronized motion machining, because of the need to control time sequence, the NC program is highly required on using of dedicated software system. The objective of this paper is to establish a mill-turn machining system with window interface of via the language of Borland C++ Builder. The developed system can plan the machining path of simple mill-turn features, including turning shape, axial slot milling, and radial packet milling, and generate the corresponding NC program. For the milling functions, after the offset coordinates are calculated along the polygonal angle vector in the center point of cutters, the NC program is generated. For the turning functions, through importing the 2D DXF (Drawing Exchange Format) file and inputting related configurations, the entity coordinates can be retrieved and the corresponding NC program is then converted. By means of the solid cutting simulation software and practical cutting experiment for the generated numerical control program, the accuracy of the tool path generation algorithm is confirmed. Hence, the cost of purchasing commercial software can be saved and the time of generating program can also be decreased so that the working efficiency can be enhanced.
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