Browsing by Author "Hung, Chinghua"

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A new device for in situ static and dynamic calibration of force platforms
(2011-04-01)
Hsieh, Hong-Jung
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Lu, Tung-Wu
;
Chen, Sheng-Chang
;
Chang, Chia-Min
;
Hung, Chinghua
In human motion analysis, in situ calibration of the force plate is necessary to improve the accuracy of the measured ground reaction force (GRF) and center of pressure (COP). Few existing devices are capable of both static and dynamic calibration of the usually non-linear GRF and COP errors, while are also easy to move and/or set up without damaging the building. The current study developed a small device (160 cm x 88 cm x 43 cm) with a mass of 50 kg, equipped with auxiliary wheels and fixing suction pads for rapid deployment and easy set-up. A PC-based controller enabled quick movement and accurate positioning of the applied force to the calibration point. Static calibration at 100 validation points and dynamic calibration of a force plate were performed using the device. After correction by an artificial neural network (ANN) trained with the static data from another 121 points, the mean errors for the GRF were all reduced from a maximum of 0.64% to less than 0.01%, while those for the COP were all reduced from a maximum of about 1.37 mm to less than 0.04 mm. For dynamic calibration, the mean errors for the GRF were reduced from a maximum of 0.46% to less than 0.28%, while those for the COP were reduced from a maximum of 0.95 mm to less than 0.11 mm. The results suggest that the calibration device with the ANN method will be useful for obtaining more accurate GRF and COP measurements in human motion analysis. (C) 2011 Elsevier B.V. All rights reserved.
AIRSIDE PERFORMANCE OF WAVY FIN-AND-TUBE HEAT EXCHANGERS - DATA WITH LARGER DIAMETER TUBE
(2010)
Lo, Huau Pao
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Hung, Chinghua
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
This study examines the airside performance of the wavy fin-and-tube heat exchangers having a larger diameter tube (D-c = 16.59 mm) with the tube row ranging from 1 to 16. It is found that the effect of tube row on the heat transfer performance is quite significant, and the heat transfer performance deteriorates with the rise of tube row. The performance drop is especially pronounced at the low Reynolds number region. Actually more than 85% drop of heat transfer performance is seen for F-p similar to 1.7 mm as the row number is increased from 1 to 16. Upon the influence of tube row on the frictional performance, an unexpected row dependence of the friction factor is encountered. The effect of fin pitch on the airside performance is comparatively small for N = 1 or N = 2. However, a notable drop of heat transfer performance is seen when the number of tube row is increased, and normally higher heat transfer and frictional performance is associated with that of the larger fin pitch.
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
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Hung, Chinghua
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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.
Biomechanical comparison between lumbar disc arthroplasty and fusion
(2009-03-01)
Chen, Shih-Hao
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Zhong, Zheng-Cheng
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Chen, Chen-Sheng
;
Chen, Wen-Jer
;
Hung, Chinghua
The artificial disc is a mobile implant for degenerative disc replacement that attempts to lessen the degeneration of the adjacent elements. However, inconsistent biomechanical results for the neighboring elements have been reported in a number of studies. The present study used finite element (FE) analysis to explore the biomechanical differences at the surgical and both adjacent levels following artificial disc replacement and interbody fusion procedures. First, a three-dimensional FE model of a five-level lumbar spine was established by the commercially available medical imaging software Amira 3.1.1, and FE software ANSYS 9.0. After validating the five-level intact (INT) model with previous in vitro studies, the L3/L4 level of the INT model was modified to either insert an artificial disc (ProDisc II; ADR) or incorporate bilateral posterior lumbar interbody fusion (PLIF) cages with a pedicle screw fixation system. All models were constrained at the bottom of the L5 vertebra and subjected to 150 N preload and 10 N m moments under four physiological motions. The ADR model demonstrated higher range of motion (ROM), annulus stress, and facet contact pressure at the surgical level compared to the non-modified INT model. At both adjacent levels, ROM and annulus stress were similar to that of the INT model and varied less than 7%. In addition, the greatest displacement of posterior annulus occurred at the superior-lateral region. Conversely, the PLIF model showed less ROM, less annulus stress, and no facet contact pressure at the surgical level compared to the INT model. The adjacent levels had obviously high ROM, annulus stress, and facet contact pressure, especially at the adjacent L2/3 level. In conclusion, the artificial disc replacement revealed no adjacent-level instability. However, instability was found at the surgical level, which might accelerate degeneration at the highly stressed annulus and facet joint. In contrast to disc replacement results, the posterior interbody fusion procedure revealed possibly accelerative degeneration of the annulus and facet joint at both adjacent levels. (C) 2008 IPEM. Published by Elsevier Ltd. All rights reserved.
Biomechanical differences of Coflex-F and pedicle screw fixation combined with TLIF or ALIF - a finite element study
(2011)
Lo, Cheng-Chan
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Tsai, Kai-Jow
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Zhong, Zheng-Cheng
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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.
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
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Chen, Shih-Hao
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Zhong, Zheng-Cheng
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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 evaluation of reconstruction plates with locking, nonlocking, and hybrid screws configurations in calcaneal fracture: a finite element model study
(2017-10-01)
Chen, Ching-Hsuan
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Hung, Chinghua
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Hsu, Yu-Chun
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Chen, Chen-Sheng
;
Chiang, Chao-Ching
Calcaneal fractures are the most common fractures of the tarsal bones. The stability of fixation is an important factor for successful reconstruction of calcaneal fractures. The purpose of this study was to analyze the biomechanical influence of plate fixation with different combinations of locking and nonlocking screws during early weight-bearing phase. A three-dimensional FE foot model was established using ANSYS software, which comprised bones, cartilages, plantar fascia, and soft tissue. Calcaneal plate was fixed with whole locking (WLS), whole nonlocking (WNS), and hybrid screw configurations for FE analysis. The WNS generated a 6.1A degrees and 2.2A degrees Bohler angle decrease compared with the intact model and WLS (WNS: 18.9; WLS: 21.1; intact: 25.0A degrees). Some hybrid screw configurations (Bohler angle: 21.5A degrees and 21.2A degrees) generated stability similar to WLS. The FE results showed that the fragments at the posterior facet and the posterior tuberosity sustained more stress. This study recommends that the hybrid screw configuration with at least four locking screws, two at the posterior facet fragment and two at the posterior tuberosity fragment, is the optimal choice for the fixation of Sanders type IIB calcaneal fractures.
Design of optical components for a light emitting diode zoom illumination system
(2011-03-01)
Tsai, Yen-Pin
;
Hung, Chinghua
;
機械工程學系
;
Department of Mechanical Engineering
In this article, we report an optical design for a light emitting diode that can achieve high illumination quality using two hyperbolic reflectors. The relative movements of the reflectors and the light source produce a zoom function that can change the illumination beam from convergence to divergence. This study uses optical software ZEMAX for system simulation, and optimization was performed to select reflector parameters with the objectives of both improving floodlight uniformity and spotlight efficiency. Finally, experiments were conducted to verify the validity of the design, and the results corresponded well to the zoom illumination simulations.
Design optimization of scroll compressor applied for frictional losses evaluation
(2010-05-01)
Liu, Yangguang
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Hung, Chinghua
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Chang, Yuchoung
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機械工程學系
;
Department of Mechanical Engineering
This paper develops a design optimization procedure in scroll-type compressor (STC). By integrating the verified STC simulation model with an optimum solver, a frictional losses reduced problem of bearing components has been investigated. After the optimum search, the frictional losses can be reduced in range of 14.1-18.1% at all testing conditions with specified constraints. Herein, the design modifications of crank and upper bearings are compromised between reduction of frictional losses and maintenance of hydrodynamic lubrication. In addition, the narrower and shorter design of lower bearing and smaller one of thrust bearing can reduce frictional losses too. Furthermore, wider selection of materials in all the bearings can be adopted with the satisfied strength constraint. By using this procedure, various optimum combinations of parameters can be found for different STC design considerations. (C) 2010 Elsevier Ltd and IIR. All rights reserved.
Development of a new apparatus for ultrasonic vibration-assisted glass hot embossing process
(2013-01-01)
Hung, Jung-Chung
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Tsai, Yen-Pin
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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.
Development of an Experimental Friction Testing Platform and a Finite Element Simulation for Hot Stamping
(2015)
Hung, Chinghua
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Hung, Tzu-Hao
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Tsai, Heng-Kuang
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Chen, Fuh-Kuo
;
Lee, Ping-Kun
In hot stamping, the material formability, thermal interaction, and metallurgical microstructure are coupled. Because of this complex forming mechanism, forming defects and product strength are difficult to predict. Therefore, accomplishing the process design and performing strength analysis by using finite element simulations is more efficient. To analyze forming characteristics and facilitate finite element analysis, material properties of boron steel at increased temperatures and other crucial process parameters such as the friction coefficient and interfacial heat transfer coefficient, which affect sheet thickness reduction and the die quenching rate considerably, must be determined first. In this study, an experimental platform was developed to measure and derive the coefficients of friction at the interface between the sheet metal and the die surface. To ensure that the designed platform was sufficiently strong to sustain both normal and pulling forces in friction tests, finite element simulations were performed. An optimal structural design was then determined and the experimental platform was constructed accordingly. Friction experiments at various increased temperatures and contact forces were conducted using non-coated 15B22 boron steel sheets as test specimens. The compression mold was made of SKD61 steel, which is commonly used as the die material in hot stamping. In each friction test, the pulling force exerted on the sheet specimen was recorded and the friction coefficient was calculated. The experimental results showed that the coefficients of friction ranged from 0.50 to 0.53 for various conditions. The friction coefficient was also shown to be more dependent on the forming temperature than on the contact force. A finite element simulation was then constructed using the experimental data and material properties of boron steel, which were calculated using the JMatPro software. The finite element simulations for hot stamping an automotive door beam, including transportation, hot forming, and die quenching analyses, were then performed. The validation of the finite element results for the hot stamped production part confirmed the importance and accuracy of the developed experimental platform for friction tests.
Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis
(2011-11-01)
Liu, Chien-Lin
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Zhong, Zheng-Cheng
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Hsu, Hung-Wei
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Shih, Shih-Liang
;
Wang, Shih-Tien
The Dynesys dynamics stabilisation system was developed to maintain the mobility of motion segment of the lumbar spine in order to reduce the incidence of negative effects at the adjacent segments. However, the magnitude of cord pretension may change the stiffness of the Dynesys system and result in a diverse clinical outcome, and the effects of Dynesys cord pretension remain unclear. Displacement-controlled finite element analysis was used to evaluate the biomechanical behaviour of the lumbar spine after insertion of Dynesys with three different cord pretensions. For the implanted level, increasing the cord pretension from 100 to 300 N resulted in an increase in flexion stiffness from 19.0 to 64.5 Nm/deg, a marked increase in facet contact force (FCF) of 35% in extension and 32% in torsion, a 40% increase of the annulus stress in torsion, and an increase in the high-stress region of the pedicle screw in flexion and lateral bending. For the adjacent levels, varying the cord pretension from 100 to 300 N only had a minor influence on range of motion (ROM), FCF, and annulus stress, with changes of 6, 12, and 9%, respectively. This study found that alteration of cord pretension affects the ROM and FCF, and annulus stress within the construct but not the adjacent segment. In addition, use of a 300 N cord pretension causes a much higher stiffness at the implanted level when compared with the intact lumbar spine.
Effects of ultrasonic vibration on SUS304 stainless steel subjected to uniaxial plastic deformation
(2018-01-01)
Chen, Chun-yuan
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Cristino, Valentino Anok Melo
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Hung, Chinghua
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機械工程學系
;
Department of Mechanical Engineering
In this study, a series of experiments was conducted in order to investigate the mechanisms of tensile force reduction and martensitic transformation in SUS304 stainless steel during ultrasonic vibration assisted tensile tests (UAT). An independent analysis of the impact of the stress superposition effect in the ultrasound assisted tensile tests was done by finite element simulation, and metallographic analysis on the specimens showed that the increase of the amplitude of the ultrasonic vibration has a great influence on the martensite transformation in the material during deformation, reducing the elongation of the specimens. The results also pointed out that the tensile force reduction is caused by a combination of the effects of stress superposition and the energy absorption of dislocations over the hardening of the material due to the increase of dislocation density and induced martensitic transformation.
Experimental and numerical analysis of titanium/aluminum clad metal sheets in sheet hydroforming
(2011-04-01)
Tseng, Huang-Chi
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Hung, Jung-Chung
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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
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Yan, Jhen-Jie
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Hung, Chinghua
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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.
Finite Element Analysis of an Ultrasonic Vibration Device at High Temperatures
(2016-06)
Lan Phuong Nguyen
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Tsai, Yen-Pin
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Hung, Jung-Chung
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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 of Tongue Type Calcaneal Fracture with Open Reduction and Internal Fixation with Locking Plate
(2018-02-01)
Chen, Ching-Hsuan
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Huang, Yu-Hsuan
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Hung, Chinghua
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Chen, Chen-Sheng
;
Chiang, Chao-Ching
Open reduction and internal fixation (ORIF) with plate is the standard treatment for displaced intra-articular calcaneal fractures. We constructed a three-dimensional complete foot finite element model, which was also modified to evaluate the biomechanical effect of Sanders IIB tongue-type calcaneal fracture treated by ORIF with locking plate. We compared plates with locking screws (LSs) and those with non-locking screws (NSs). Static standing was simulated by applying ground reaction force and the pulling force of the Achilles tendon. ORIF with plate using NS or LS provided good stability for Sanders IIB tongue-type calcaneal fracture and might allow light touch weight-bearing in the early postoperative period.
Finite element analysis on neck-spinning process of tube at elevated temperature
(2011-10-01)
Huang, Chi-Chen
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Hung, Jung-Chung
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Hung, Chinghua
;
Lin, Chia-Rung
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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
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Hung, Chinghua
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Hung, Jung-Chung
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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.
Influence of Dynesys System Screw Profile on Adjacent Segment and Screw
(2010-08-01)
Liu, Chien-Lin
;
Zhong, Zheng-Cheng
;
Shih, Shih-Liang
;
Hung, Chinghua
;
Lee, Yong-Eng
Study Design: Displacement-controlled finite element analysis was used to evaluate the mechanical behavior of the lumbar spine after insertion of the Dynesys dynamic stabilization system. Objective: This study aimed to investigate whether different depths of screw placement of Dynesys would affect load sharing of screw, range of motion (ROM), annulus stress, and facet contact force. Summary of Background Data: In clinical follow-up, a high rate of screw complications and adjacent segment disease were found after using Dynesys. The pedicle screw in the Dynesys system is not so easy to implant into the standard position and causes the screw to protrude more prominently from the pedicle. Little is known about how the biomechanical effects are influenced by the Dynesys screw profile. Methods: The Dynesys was implanted in a 3-dimensional, nonlinear, finite element model of the L1 to L5 lumbar spine. Different depths of screw position were modified in this model by 5 and 10mm out of the pedicle. The model was loaded to 150 N preload and controlled the same ROMs by 20, 15, 8, and 20 degrees in flexion, extension, torsion, and lateral bending, respectively. Resultant ROM, annulus stress, and facet contact force were analyzed at the surgical and adjacent level. Results: Under flexion, extension, and lateral bending, the Dynesys provided sufficient stability at the surgical level, but increased the ROM at the adjacent level. Under flexion and lateral bending, the Dynesys alleviated annulus stress at the surgical level, but increased annulus stress at the adjacent level. Under extension, the Dynesys decreased facet loading at the surgical level but increased facet loading at the adjacent level. Conclusions: This study found that the Dynesys system was able to restore spinal stability and alleviate loading on disc and facet at the surgical level, but greater ROM, annulus stress, and facet loading were found at the adjacent level. In addition, profile of the screw placement caused only a minor influence on the ROM, annulus stress, and facet loading, but the screw stress was noticeably increased.