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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.
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
;
Hung, Chinghua
;
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.
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
;
Hsu, Yu-Chun
;
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.
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
;
Hung, Chinghua
;
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.
Study on improvement of CRI using RGB LED lights for underwater environments
(2017)
Lai, Ming Hui
;
Hung, Chinghua
;
機械工程學系
;
Department of Mechanical Engineering
This study presents a novel LED (light-emitting diode) light source. The device was simulated in both air and underwater environments by using TracePro. This device can adjust the current to change the power of different colors (M-E-L-R,M-E-L-G and M-E-L-B) to improve its color rendering index (CRI) in different scattering environments. The simulated results were analyzed and used to build a design module for use in underwater LED devices. In underwater experiments, the ordered sequence of light efficiency values was M-E-L-G > M-E-L-B > M-E-L-R. Underwater measurements of the performance of the device confirmed the simulated results. (C) 2016 Elsevier GmbH. 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.
Development of an Experimental Friction Testing Platform and a Finite Element Simulation for Hot Stamping
(2015)
Hung, Chinghua
;
Hung, Tzu-Hao
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Tsai, Heng-Kuang
;
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.
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.
Modeling the Embossing Stage of the Ultrasonic-Vibration-Assisted Hot Glass Embossing Process
(2015-06-01)
Nguyen, Lan Phuong
;
Hao, Kei-Chon
;
Su, Yi-Hsiang
;
Hung, Chinghua
;
機械工程學系
Ultrasonic vibration technology has recently been applied in high-temperature forming processes, such as hot upsetting and hot glass embossing. Experimental research has delineated the effects of ultrasonic vibration on reducing required forces and improving the formability of materials. The purpose of this study was to construct a finite element model of the embossing stage of the ultrasonic vibration-assisted hot glass embossing process. Traditional hot embossing experiments in which the embossing speed and temperature were varied were performed to calculate the viscoelastic dissipation caused by ultrasonic vibration, and this value was then inputted into the simulation. The consistency of the force responses in the experiments and simulation indicated that the proposed model is valid. The findings indicate that the influences of parameters such as the vibration frequency, vibration amplitude, and embossing speed on the ultrasonic vibration-assisted hot glass embossing process must be investigated further.
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.

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