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Now showing 1 - 10 of 17

An analysis of the formability of aluminum/copper clad metals with different thicknesses by the finite element method and experiment
(2010-08-01)
Tseng, Huang-Chi
;
Hung, Chinghua
;
Huang, Chin-Chuan
;
交大名義發表
;
機械工程學系
In this research, the possibility of applying forming limit diagrams to the formability and fracture prediction of clad metal sheets is examined. The forming limits of clad metal sheets with different thickness combinations (e.g., A1050 1.0, 1.5, 2.0 mm/C1100 1.0 mm) are investigated via forming limits test (punch stretching tests). The true stress-strain curves of Al/Cu clad metal sheets are obtained through tensile tests. Using the experimental forming limit diagrams and the stress-strain curves, the fracture prediction of clad metal sheets are simulated by finite element analysis. Moreover, deep drawing tests are carried out to compare the experimental with the numerical results. These results can verify the accuracy of finite element model. Finally, significant differences in formability are found, and comparisons of the fracture prediction of clad metals with different initial thickness ratios are analyzed both numerically and experimentally.
Study on involute of circle with variable radii in a scroll compressor
(2010-11-01)
Liu, Yangguang
;
Hung, Chinghua
;
Chang, Yuchoung
;
機械工程學系
;
Department of Mechanical Engineering
A geometric model of scroll profiles, constructed from an involute of circle with variable radii, has been developed by using the theorem of planar orbiting mechanisms. Parametric studies have also been investigated in this study. When compared to the conventional scroll profile with the same suction volume, volume ratio and housing size, this new model demonstrates better reliability and efficiency because of a lower wrap height. Alternatively, a scroll type compressor with a more compact housing size can be achieved by using this new profile but keeping its wrap height the same as the conventional one. Furthermore, arc and line modifications have been built to provide wider design varieties. These are used to avoid interference at the center of the scroll pair and to boost the volume ratio of this new scroll profile. (c) 2010 Elsevier Ltd. All rights reserved.
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.
The influence of different magnitudes and methods of applying preload on fusion and disc replacement constructs in the lumbar spine: a finite element analysis
(2013-09-01)
Zhong, Zheng-Cheng
;
Hung, Chinghua
;
Lin, Hung-Ming
;
Wang, Ying-Hui
;
Huang, Chang-Hung
In a finite element (FE) analysis of the lumbar spine, different preload application methods that are used in biomechanical studies may yield diverging results. To investigate how the biomechanical behaviour of a spinal implant is affected by the method of applying the preload, hybrid-controlled FE analysis was used to evaluate the biomechanical behaviour of the lumbar spine under different preload application methods. The FE models of anterior lumbar interbody fusion (ALIF) and artificial disc replacement (ADR) were tested under three different loading conditions: a 150N pressure preload (PP) and 150 and 400N follower loads (FLs). This study analysed the resulting range of motion (ROM), facet contact force (FCF), inlay contact pressure (ICP) and stress distribution of adjacent discs. The FE results indicated that the ROM of both surgical constructs was related to the preload application method and magnitude; differences in the ROM were within 7% for the ALIF model and 32% for the ADR model. Following the application of the FL and after increasing the FL magnitude, the FCF of the ADR model gradually increased, reaching 45% at the implanted level in torsion. The maximum ICP gradually decreased by 34.1% in torsion and 28.4% in lateral bending. This study concluded that the preload magnitude and application method affect the biomechanical behaviour of the lumbar spine. For the ADR, remarkable alteration was observed while increasing the FL magnitude, particularly in the ROM, FCF and ICP. However, for the ALIF, PP and FL methods had no remarkable alteration in terms of ROM and adjacent disc stress.
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.
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.
Performance improvements in low side scroll compressor with extended operation speeds
(2011-11-01)
Tang, Yuehju
;
Hung, Chinghua
;
Chang, Yuchoung
;
機械工程學系
;
Department of Mechanical Engineering
Scroll-type compressors (STCs) are widely used in modern air conditioners for higher efficiency and durability. However, the internal leakage, caused during un-rating operated speed, reduces the volumetric efficiency and influences the performance of STCs. This paper has proposed an axial-compliant mechanism (ACM), composed of a suspension structure and a limiting ring, to solve the leakage problem of a low side STC running in extended speeds. The aim of this ACM design is to control the leakage by keeping optimum clearance. By integrating the verified STC performance simulation package with the internal leakage model, the optimum clearance between scroll tip and bottom plate has been investigated. After the numerical simulation, by employing suitable designs, an improved ACM prototype has been developed and tested. The experimental results show that low leakage, noise, and power consumption are achieved during compression processes even with extended operation speeds, and moreover, the overall coefficient of performance is increased from 0.61% to 13.53%. In this study, the proposed design is useful for enhancing the performance of low side type STCs. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
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.
Biomechanical effect after Coflex and Coflex rivet implantation for segmental instability at surgical and adjacent segments: a finite element analysis
(2011)
Lo, Cheng-Chan
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Tsai, Kai-Jow
;
Chen, Shih-Hao
;
Zhong, Zheng-Cheng
;
Hung, Chinghua
The Coflex device may provide stability to the surgical segment in extension but does not restore stability in other motion. Recently, a modified version called the Coflex rivet has been developed. The effects of Coflex and Coflex rivet implantation on the adjacent segments are still not clear; therefore, the purpose of this study was to investigate the biomechanical differences between Coflex and Coflex rivet implantation by using finite element analyses. The results show that the Coflex implantation can provide stability in extension, lateral bending, and axial rotation at the surgical segment, and it had no influence at adjacent segments except for extension. The Coflex rivet implantation can provide stability in all motions and reduce disc annulus stress at the surgical segment. Therefore, the higher range of motion and stress induced by the Coflex rivet at both adjacent discs may result in adjacent segment degeneration in flexion and extension.
Biomechanical differences of Coflex-F and pedicle screw fixation combined with TLIF or ALIF - a finite element study
(2011)
Lo, Cheng-Chan
;
Tsai, Kai-Jow
;
Zhong, Zheng-Cheng
;
Chen, Shih-Hao
;
Hung, Chinghua
Lumbar interbody fusion is a common procedure for treating lower back pain related to degenerative disc diseases. The Coflex-F is a recently developed interspinous spacer, the makers of which claim that it can provide stabilisation similar to pedicle screw fixation. Therefore, this study compares the biomechanical behaviour of the Coflex-F device and pedicle screw fixation with transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF) surgeries by using finite element analysis. The results show that the Coflex-F device combined with ALIF surgery can provide stability similar to the pedicle screw fixation combined with TLIF or ALIF surgery. Also, the posterior instrumentations (Coflex-F and pedicle screw fixation) combined with TLIF surgery had lower stability than when combined with ALIF surgery.

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