Browsing by Author "Hung, Jung-Chung"

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Development of a new apparatus for ultrasonic vibration-assisted glass hot embossing process
(2013-01-01)
Hung, Jung-Chung
;
Tsai, Yen-Pin
;
Hung, Chinghua
;
機械工程學系
;
Department of Mechanical Engineering
A new apparatus for an ultrasonic vibration-assisted glass hot embossing process has been developed. The upper die constitutes the ultrasonic vibrating device, and a cooler is provided to protect the transducer from the high operating temperatures. An ultrasonic horn originally designed for use at room temperature was modified to ensure correct operation of ultrasonic vibrating device for high temperature use. Because the load cell is located inside a vacuum chamber, the detection of the force applied to the glass during the forming process is not significantly impacted by external forces, and thus, a precise force history of the forming glass can be obtained. Flat hot embossing experiments were performed to investigate the effect of ultrasonic vibration on the amount of force required during forming, and Fresnel structure hot embossing experiments were then conducted to investigate the improvement in molding accuracy gained through ultrasonic vibration. The experimental results are taken to validate the manufacturing potential of the developed apparatus and the improvement in formability achieved by applying ultrasonic vibration. (c) 2012 Elsevier Inc. All rights reserved.
Evaluation of Friction in Ultrasonic Vibration-assisted Press Forging Using Double Cup Extrusion Tests
(2012-12-01)
Hung, Jung-Chung
;
Huang, Chi-Chen
;
機械工程學系
;
Department of Mechanical Engineering
Ultrasonic energy is applied to a die in an ultrasonic vibration-assisted metal forming process, and the die is used to deform the workpiece. The friction between die and workpiece decreases when ultrasonic vibration is applied ill metal forming process. The friction ploys a crucial role in metal forming: therefore, the friction force must be evaluated and quantified to obtain the optimal forming process. The ring compression test is widely used to evaluate the friction factor or coefficient of friction. However the ring compression test is unsuitable to determine the friction condition in forging and extrusion processes. Therefore, this study evaluated the effect of vibration on the friction factor using double cup extrusion tests (DCET). The apparatus design for ultrasonic vibration-assisted DCET and experiments were conducted, and the commercial finite element software Marc was used to simulate the DECT to obtain the friction calibration curves. The results demonstrated that the evaluation of the interface friction factor using DCET is sensitive. Under no lubricant condition, the friction factors of traditional and ultrasonic vibration-assisted DCET were approximately 0.1 and 0.3, respectively Under Blue Moly lubricant condition, the friction factors of traditional and ultrasonic vibration-assisted DCET were approximately 0.05 and 0.1, respectively.
Experimental and numerical analysis of titanium/aluminum clad metal sheets in sheet hydroforming
(2011-04-01)
Tseng, Huang-Chi
;
Hung, Jung-Chung
;
Hung, Chinghua
;
Lee, Ming-Fu
;
交大名義發表
Clad metals are becoming increasingly emphasized in sheet metal applications. In this research, sheet hydroforming process (SHF) was adopted to improve the formability of Ti/Al clad metal sheets and SUS 304 metal sheets used in computer, communication, and consumer product housings. Both finite element simulation and experimental verification were carried out to investigate the deformation of blanks. Several significant process parameters, such as holding force, friction, counter pressure history, and blank dimensions, were discussed for improving the formability of the two metal sheets. In SHF simulation, a virtual film technique was proposed to realistically approach the hydraulic loading condition during SHF. Finally, the deformed shape and thickness distribution of parts manufactured with SHF were compared with the results of simulation. Good agreements were obtained.
Fabricating High-Aspect Ratio Microchannels on Metallic Sheets Using Hydroforming
(2012)
Lin, Chih-Chia
;
Yan, Jhen-Jie
;
Hung, Chinghua
;
Hung, Jung-Chung
;
交大名義發表
High-aspect ratio microchannels on bipolar plates have the advantage of improving fuel cell performance. This study formed high-aspect ratio microchannels by increasing the forming pressure, and predicted excellent aspect ratio of micro-flow channels by optimization analysis during the hydroforming process. This study used an experimental high-pressure hydroforming apparatus that provides various pressures to form microchannels on 304 stainless steel sheets with 0.1 mm thickness. Simultaneously, finite element analysis software was used to analyze the hydroforming process. First, the precision of the finite element model was verified by comparing simulations with experiments. Subsequently, the optimization software was connected to the finite element software to determine the optimal aspect ratio of microchannels by changing the dimension of micro-flow channels and pressures. Furthermore, the results of the simulations, hydroforming experiments, and related literature were discussed. The result indicated that the high-pressure hydroforming technique was feasibility, which formed high aspect ratio microchannels with 200 MPa, and the optimization predicted aspect ratio could reach 0.478 when changing geometries of channels and pressures. This research proposed a design process through hydroforming experiments, finite element analysis, and optimization analysis when predicting and designing the dimensions of micro-flow channels on metallic bipolar plates.
Fabrication of micro-flow channels for metallic bipolar plates by a high-pressure hydroforming apparatus
(2012-05-15)
Hung, Jung-Chung
;
Lin, Chih-Chia
;
機械工程學系
;
Department of Mechanical Engineering
High aspect-ratio micro-flow channels on bipolar plates have the advantage of improving fuel cell performance. This study forms micro-flow channels with a high aspect ratio by increasing the forming pressure during the hydroforming process. This study designs and constructs a mechanical apparatus to enable a two-stage pressure increase in the hydroforming process. A high-pressure container is designed with three-layered tapered cylinders to sustain 1230.17 MPa working pressures, and a special seal component is designed to seal the high-pressure fluid and maintain high pressure. The feasibility of this high-pressure hydroforming technique is verified in preliminary tests. The investigation indicates that the aspect ratio of micro-flow channels can reach 0.468 when a hydrostatic pressure of 250 MPa is applied. Compared with the maximum aspect ratio of 0.31 formed using the traditional hydroforming process, the aspect ratio of micro-flow channels in this study was 51% higher, which enables the fuel cells with metallic bipolar plates to meet both performance and manufacturing requirements. (C) 2012 Elsevier B.V. All rights reserved.
Finite Element Analysis of an Ultrasonic Vibration Device at High Temperatures
(2016-06)
Lan Phuong Nguyen
;
Tsai, Yen-Pin
;
Hung, Jung-Chung
;
Hsieh, Yi-Chun
;
Hung, Chinghua
Ultrasonic-vibration-assisted forming has been extensively adopted in plastic manufacturing processes. Ultrasonic vibration contributes to enhancing material formability and product quality and to reducing manufacturing costs by improving frictional conditions and increasing the temperature of materials. However, designing a suitable ultrasonic vibration system for processes conducted at high working temperatures, such as the ultrasonic vibration-assisted glass hot embossing process, is difficult because of complex thermal boundaries and material properties. In this study, an ultrasonic vibration system that can be used at high working temperatures was analyzed using the finite element method and ANSYS commercial software. The simulation results obtained from thermal, modal, and harmonic response analyses were compared with experimental measurements to confirm the validity of the numerical analysis. The resulting finite element module can be used in designing the components of ultrasonic vibration devices that can be used at high working temperatures.
Finite element analysis on neck-spinning process of tube at elevated temperature
(2011-10-01)
Huang, Chi-Chen
;
Hung, Jung-Chung
;
Hung, Chinghua
;
Lin, Chia-Rung
;
機械工程學系
Tube spinning process is a metal forming process used in the manufacture of axisymmetric products and has been widely used in various applications. Finite element analysis has been successfully applied to the tube spinning processes, but no temperature effects have been considered on neck-spinning. For this reason, the aim of this research is to investigate numerically the neck-spinning process of a tube at elevated temperature. The commercial software Abaqus/Explicit was adopted in the simulation. For the construction of the material model, special uniaxial tensile tests were conducted at elevated temperature and various strain rates, since the material is sensitive to strain rates at high temperature. Comparisons between experimental and simulation results on thickness distribution and the outer contour of the spun tube are discussed. During the final stage, the average deviations between the simulation and experiment were 10.65% in thickness and 3.03% in outer contour. Good agreement was found between experimental and simulation results. The influence of the coefficient of friction, roller translation speeds, and the tip radius of the rollers were also investigated through numerical simulation.
Glass material model for the forming stage of the glass molding process
(2008-05-26)
Tsai, Yu-Chung
;
Hung, Chinghua
;
Hung, Jung-Chung
;
機械工程學系
;
Department of Mechanical Engineering
The aim of this research is to obtain an accurate material model for glass that can be used in finite element (FE) analysis of the glass molding process. A thorough understanding of the deformation behavior of the glass specimens was acquired by performing uniaxial compression tests. The elasto-viscoplastic model was utilized for the glass material at the molding temperature to construct the FE model, and a suitable set of parameters for this material model was verified by comparing the simulation results to the experimental data. As a result, the feasibility of the elasto-viscoplastic model for glass at the molding temperature was confirmed; this material model can be used in FE analysis of the prediction and modification of properties of the final lens products. (C) 2008 Published by Elsevier B.V.
Investigation of the effects of ultrasonic vibration-assisted micro-upsetting on brass
(2013-09-15)
Hung, Jung-Chung
;
Tsai, Yu-Chung
;
機械工程學系
;
Department of Mechanical Engineering
Ultrasonic vibration is widely applied in traditional metal forming to soften material and to increase formability. However, the effects of ultrasonic vibration on miniaturized workpieces must be studied before applying its benefits to metallic micro-forming. This study investigates the effects of applying ultrasonic vibration to micro-forming, along with two other factors: specimen size and grain size. Conventional (without ultrasonic vibration) and ultrasonic vibration micro-upsetting experiments were conducted using brass (C2600). Specimens of three different dimensions (phi 3 x 4.5 mm, phi 2 x 3 mm, and phi 1 x 1.5 mm) and of three grain sizes (12 mu m, 44 mu m, and 90 mu m) were used. The conventional micro-upsetting (CMU) experiment revealed the size-effect in which flow stress decreased with the miniaturizing of the specimen. Flow stress also decreased as the grain size increased, but at a smaller magnitude than that of the size-effect. Results show that ultrasonic vibration-assisted micro-upsetting (UMU) decreased the flow stress effectively, especially in miniaturized specimens. The amount of decrease was related more to the dimension than to the grain size of the specimen. (C) 2013 Elsevier B.V. All rights reserved.
Investigations on the material property changes of ultrasonic-vibration assisted aluminum alloy upsetting
(2013-03-01)
Hung, Jung-Chung
;
Lin, Chih-Chia
;
機械工程學系
;
Department of Mechanical Engineering
Numerous studies have shown the benefit of ultrasonic-vibration assisted metal forming. This benefit include a reduction in forming forces, which might be attributed to the superposition of stress, increased temperatures, the effects of interface friction, and energy absorption of dislocation. This study conducts a series of experiments and analyses to investigate the main mechanisms of a reduction in forming forces during ultrasonic-vibration assisted A6061-T6 aluminum alloy upsetting. The findings of this research confirm that, under frictionless conditions, ultrasonic vibration still reduced forming forces, and ultrasonic vibration can increase the temperature of specimens and soften specimen surface during upsetting. From metallographic analyses and micro-hardness tests, the results reveal that energy absorption of dislocation was occurred during upsetting, which also contribute to the reduction of forming force. This research concludes that the mechanisms of increased temperatures and energy absorption of dislocation can affect the material property and make a reduction in forming forces; however, the interface friction effect has nothing to do with a reduction in forming forces. (C) 2012 Published by Elsevier Ltd.
Optimization of Ultrasonic Plastic Welding Horns on Amplitude Uniformity
(2012)
Hung, Jung-Chung
;
Tsai, Yen-Pin
;
Hung, Chinghua
;
機械工程學系
;
Department of Mechanical Engineering
This research integrated finite element analysis (FEA) and optimum design to obtain a fast, accurate and automatic optimization system for the design of an ultrasonic horn. The optimization system was developed to achieve uniform amplitude distribution on the output surface of a block shaped horn for the ultrasonic plastic welding. Agreement between the experimental and numerical data proved that this optimization system was efficient in the design of ultrasonic horns.
The effect of ultrasonic-vibration on upsetting
(2006)
Hung, Jung-Chung
;
Tsai, Yu-Chung
;
Hung, Chinghua
;
機械工程學系
;
Department of Mechanical Engineering
Ultrasonic-vibration upsetting is a process in which a cylindrical specimen is compressed by an axial force while the ultrasonic vibration is simultaneously applied to the die. Homogenous deformation is difficult to achieve during this process because of the friction at the interface between the specimen and the die. An extrapolated compression test was performed in this study on aluminum alloy specimens to explore the effect of superimposing ultrasonic-vibration during upsetting. Experimental results indicate that ultrasonic-vibration reduced the compressive force when the friction was eliminated by the extrapolated compression test. The specimen size also influences the force-reducing effects of ultrasonic-vibration. The decrease in the compressive force is smaller for a larger specimen. The barreling profile of the specimen after test indicates that the interface friction will increase during ultrasonic-vibration compression. Additionally, the raised material temperatures are caused by ultrasonic-vibration. Experimental results of the hot extrapolated compression test and the hot ring compression test indicate that the drop in the flow stress and the increase in the interface friction are caused by the increase in the temperature of the material under ultrasonic vibration.
THE INFLUENCE OF THE ROLLER FORMING PATH ON THE NECK-SPINNING PROCESS OF TUBE AT ELEVATED TEMPERATURE
(2012)
Huang, Chi-Chen
;
Hung, Jung-Chung
;
Lo, Cheng-Chan
;
Lin, Chia-Rung
;
Hung, Chinghua
The tube spinning process is a metal forming process used in the manufacture of axisymmetric products, and has been widely used in various applications. In this paper, the neck-spinning process was applied to form the neck part of the tube end at an elevated temperature. The spun tube was used as a high pressure CO2 vessel, which is a component of motorcycle airbag jackets. An uneven surface will occur on the tube surface if the thickness distribution of the tube is not uniform after the neck-spinning process. This is because different thicknesses result from different contractions during the cooling stage. For this reason, the aim of this research was to numerically investigate the roller forming path to improve the thickness distribution of the tube during the neck-spinning process. The finite element method was used to simulate the neck-spinning process of the tube at an elevated temperature. For the construction of the material model, special uni-axial tensile tests were conducted at elevated temperatures and various strain rates, because the material is sensitive to strain rates at high temperatures. This paper compares the experimental and simulation results of the thickness distribution and the outer contour of the spun tube. The validated finite element model was used to investigate the influence of the roller forming path on the thickness distribution of the tube. The thickness distribution of the tube formed by a curved path was found to be more uniform than for the tube formed by a straight path. Finally, the optimization technique was used to find the optimal forming path, and the optimal result was verified experimentally.
Three Dimension Finite Element Model for Neck-spinning Process of Tube at Elevated Temperature
(2012-01-01)
Huang, Chi-Chen
;
Hung, Chinghua
;
Hung, Jung-Chung
;
Lin, Chia-Rung
;
交大名義發表
The aim of this research is to investigate numerically the neck-spinning process of a tube at elevated temperature. The commercial software Abaqus/Explicit was adopted in the simulation. For the construction of the material model, special uni-axial tensile tests were conducted at elevated temperature and various strain rates, since the material is sensitive to strain rates at high temperature. The influence of the element type and mass scaling factor were investigated through numerical simulation. Full-integration shell element is the better choice in the simulation of the neck-spinning process at elevated temperature. The use of suitable mass scaling factor will make the analysis more efficiency. Comparisons between experimental and simulation results on thickness distribution and the outer contour of the spun tube are discussed. Good agreement was found between experimental and simulation results.
Three Dimension Finite Element Model for Neck-spinning Process of Tube at Elevated Temperature
(2012-01-01)
Huang, Chi-Chen
;
Hung, Chinghua
;
Hung, Jung-Chung
;
Lin, Chia-Rung
;
機械工程學系
The aim of this research is to investigate numerically the neck-spinning process of a tube at elevated temperature. The commercial software Abaqus/Explicit was adopted in the simulation. For the construction of the material model, special uni-axial tensile tests were conducted at elevated temperature and various strain rates, since the material is sensitive to strain rates at high temperature. The influence of the element type and mass scaling factor were investigated through numerical simulation. Full-integration shell element is the better choice in the simulation of the neck-spinning process at elevated temperature. The use of suitable mass scaling factor will make the analysis more efficiency. Comparisons between experimental and simulation results on thickness distribution and the outer contour of the spun tube are discussed. Good agreement was found between experimental and simulation results.
Three Dimensional Finite Element Analysis on Neck-spinning Process of Thick-Walled Tube at an Elevated Temperature
(2012)
Huang, Chi-Chen
;
Fan, Hsin-Yen
;
Hung, Chinghua
;
Hung, Jung-Chung
;
Lin, Chia-Rung
Tube spinning is a metal forming process used to manufacture axisymmetric products. This study chose a seamless thick-walled steel tube to manufacture a high pressure vessel. Finite element analysis was successfully applied to the neck-spinning process of a thin-walled tube; however, previous research has not investigated the neck-spinning process of thick-walled tubes. Therefore, the aim of this research was to investigate numerically the neck-spinning process of thick-walled tubes at an elevated temperature. The commercial software Abaqus/Explicit was adopted in the simulation. This paper compares experimental and simulation results on thickness distribution and outer contour of the spun tube. During the final stage, the average deviations between the simulation and experiment were 6.74% in thickness and 4.97% in outer contour. The simulation results correspond with those derived in the experiment.
Ultrasonic vibration-assisted optical glass hot embossing process
(2012-06-01)
Tsai, Yen-Pin
;
Hung, Jung-Chung
;
Yin, Li-Chao
;
Hung, Chinghua
;
機械工程學系
A homemade apparatus was used to apply ultrasonic-vibration to assist the glass hot embossing processes. To operate at high temperatures for glass hot embossing, the ultrasonic vibration system was appropriately designed with an embedded cooling system, and an ultrasonic horn was specifically modified for high-temperature use. Molds with both V-groove and Fresnel structures were manufactured for hot embossing experiments on PSK-100 glass. The heights of the molded structures were increased significantly with the assistance of ultrasonic vibration. This technology demonstrates the capability to upgrade the performance of the glass hot embossing process.