Browsing by Author "Yeh, Ren-Yu"

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Application of porous oxide layer in plastic/metal direct adhesion by injection molding
(2015-08-03)
Yeh, Ren-Yu
;
Hsu, Ray-Quen
;
機械工程學系
;
Department of Mechanical Engineering
In this study, porous oxide layers were coated on aluminum sheets by plasma electrolytic oxidation (PEO) treatment. The PEO-treated aluminum sheets were then inserted and direct heated in the injection mold. The melting plastic penetrated and solidified in the micropores during the injection molding process, consequently achieving plastic/metal direct adhesion through micro-mechanical interlocking. The effects of the different surface morphologies of PEO coatings on plastic/metal adhesion were studied by shear test and microscopic characterizations. The microstructures were varied by changing PEO process parameters. The bonding strength was affected by the surface morphology changes, and the experimental results show that the surface porosity is a major factor in the direct adhesion. Reliable joints can be achieved on the porous coating, and the strength was proportional to the surface porosity. The shear strength in this study was in a range of approximately 3-8MPa with 7-20% surface porosity.
Development of ultrasonic direct joining of thermoplastic to laser structured metal
(2016-03-01)
Yeh, Ren-Yu
;
Hsu, Ray-Quen
;
機械工程學系
;
Department of Mechanical Engineering
This work reports on an improved ultrasonic welding process for the direct joining of thermoplastic and metal. A metal thin plate was structured with grid arrays on a micro-scale level by laser irradiation. A thermoplastic part was placed on the structured region, and ultrasonic welding or ultrasonic hot welding was applied. The thermoplastic was locally melted and re-solidified in the structured grooves with very low energy input due to the tiny initial contact area of the grid tips. Single lap shear specimens and boss specimens were used to study the feasibility and performance of hybrids made by this joining method. Both shear strength and normal tensile strength were affected by changes in the grid structures and welding parameters, and the experimental results show that the micro-structure geometry of the metal plate is a major factor in the joining strength. Successful welds required that process cycle times be less than 1 s. Furthermore, the mold holding the metal sheet was heated in the ultrasonic hot welding experiments, and the heated mold significantly enhanced the joint quality. Ultrasonic hot welding appears to be a fast, low cost, and reliable method to produce plastic/metal hybrid products for electronics and other industrial applications. (C) 2015 Elsevier Ltd. All rights reserved.
Direct joining of 3D-printed thermoplastic parts to SLM-fabricated metal cellular structures by ultrasonic welding
(2018-10-01)
Tang, Sheng-Hung
;
Cheng, Chung-Wei
;
Yeh, Ren-Yu
;
Hsu, Ray-Quan
;
機械工程學系
The joining capability of metal cellular structures fabricated using the additive manufacturing (selective laser melting (SLM)) method is investigated herein. The metal cellular structures are composed of sub-millimeter holes and internal pores. The direct joining of 3D-printed ABS-M30i thermoplastic parts to metal cellular structures by ultrasonic welding is demonstrated. The SLM-fabricated structures comprised of partially melted powders provide micro-scale roughness, which enhances the micro-mechanical interlocking between joining parts. A shear strength 17.7MPa and normal tensile strength of 15.2MPa were obtained, up to 55 and 48% of ABS-M30i ultimate tensile strength, respectively. Moreover, normal tensile plastic strength up to 86% of the shear strength was obtained.
Direct numerical simulation of methane hydrate dissociation in pore-scale flow by using CFD method
(2017-10-01)
Yu, Pei-Yi
;
Sean, Wu-Yang
;
Yeh, Ren-Yu
;
Hsieh, Lin-Han Chiang
;
Hsu, Ray-Quan
The objective of this work is to establish a new pore-scale (m-mu m) model for estimating the dissociation rate of methane hydrate (MH) synthesized in laboratory-scale sediment samples. Finite volume method (FVM) with unstructured mesh were constructed in a representative face-centered cubic unit. The surface model of MH reported by Sean et al. (2007) has been employed. In the bulk flow, concentration of methane in water flow was analyzed by computational fluid dynamics (CFD) method. However, only water flow and solid MH are simulated without considering ice or gas phase. In this study, tentative cases with porosity 0.74, 0.66, and 0.49 is individually considered as representative cubic unit of MH array. The initial temperature, 253.15 (K) of MH pellets inside the cubic unit dissociated due to the driving force of fugacity variation, ex. 0.56 and 0.54 (MPa) while warm water of 282.15 and 276.15 (K) flow in. In the calculation, periodic conditions are imposed at surfaces of inlet/right/front sides updated every time step. The flux of methane at the surface are all regarded as being dissolved into the water in this high pressure state, and compared to Kim et al. (1987)'s correlation at Reynolds no. of about 50. Results of dissociation flux in cases 5 and 6 with porosity 0.49 show good agreements with Kim's correlation. However, as the porosity increases, flux increases due to the fast transport in bulk flow such as cases 1-4 in this study. If the transport process in bulk flow is faster than dissociation rate, then the surface flux becomes saturated as Reynolds no. greater than 100 in this work. (C) 2017 Elsevier Ltd. All rights reserved.