Ray-Quen Hsu

The finite element analysis on planetary rolling process

Abstract This paper is focused on using the finite element method to simulate and analyze the planetary rolling process. First, a basic geometric model of the planetary rolling mill that considers roll profiles and offset angle of the rolls was constructed. Then, a three-dimensional elastic–plastic finite element simulation was used to analyze both the deformation characteristics of this process and the distributions of stress and strain in the workpieces. During simulations, an algorithm called Equation of Meshing was proposed by which the initial contact conditions between the rollers and the workpiece were successfully derived. Finally, an optimum design method was integrated into this analysis for seeking the best design variables in order to reduce the cavity conditions in the leading end of milled steel rods.

A study on seamless tube in the planetary rolling process

Abstract In this paper, the finite element method and the dual-stream functions upper bound method are selected to analyze the tube rolling process with a planetary rolling mill. Three-dimensional elastic–plastic finite element simulations with special emphasis on the determination of the roller profile and realistic contact conditions between the rollers, workpiece and mandrel are used to reveal the deformation characteristics of seamless tube during the rolling process. In addition, the kinematically admissible velocity field of the deforming tube is described in terms of two stream functions so that the velocity components of the deforming tube can be obtained through the upper bound analysis. In both analysis methods, the equation of meshing is used to determine the contact condition between the rollers and the workpiece. The results from both methods with different variables are observed and compared.

A universal velocity field for the extrusion of non-axisymmetric rods with non-uniform velocity distribution in the extrusion direction

Abstract This study formulates a universal velocity field that is kinematically admissible for application in the extrusion of non-axisymmetric rods. Then upper bound theorem dictates that a better upper bound solution heavily depends on the precise conformity of the velocity field postulated. However, a compromise must frequently be made, since the formulation is in general rather complicated. The kinematically admissible velocity field proposed herein has the following features: (a) it is three-dimensional, (b) it is non-uniformally distributed in the axial direction, and (c) the formulation is straight-forward once the boundary of the deformation zone is specified. In addition, the velocity field is applied to the extrusion of rectangular, hexagonal, and octagonal rods from round billets. Moreover, the extrusion loads are calculated against process variables such as the semi-die angle, the percentage reduction of area, and the friction factor. Furthermore, the velocity field is compared with results from the literature, indicating that the present results render a better upper bound solution for application in extrusion than do previous results.

Chip-based protein-protein interaction studied by atomic force microscopy.

In this article, a technique for accurate direct measurement of protein‐to‐protein interactions before and after the introduction of a drug candidate is developed using atomic force microscopy (AFM). The method is applied to known immunosuppressant drug candidate Echinacea purpurea derived cynarin. T‐cell/CD28 is on‐chip immobilized and B‐cell/CD80 is immobilized on an AFM tip. The difference in unbinding force between these two proteins before and after the introduction of cynarin is measured. The method is described in detail including determination of the loading rates, maximum probability of bindings, and average unbinding forces. At an AFM loading rate of 1.44 × 104 pN/s, binding events were largely reduced from 61 ± 5% to 47 ± 6% after cynarin introduction. Similarly, maximum probability of bindings reduced from 70% to 35% with a blocking effect of about 35% for a fixed contact time of 0.5 s or greater. Furthermore, average unbinding forces were reduced from 61.4 to 38.9 pN with a blocking effect of ∼37% as compared with ∼9% by SPR. AFM, which can provide accurate quantitative measures, is shown to be a good method for drug screening. The method could be applied to a wider variety of drug candidates with advances in bio‐chip technology and a more comprehensive AFM database of protein‐to‐protein interactions. Biotechnol. Bioeng. 2012; 109: 2460–2467.

Fast incorporation of primary amine group into polylactide surface for improving C2C12 cell proliferation using nitrogen‐based atmospheric‐pressure plasma jets

In this article, we report the development of the fast incorporation of primary amine functional groups into a polylactide (PLA) surface using the post-discharge jet region of an atmospheric-pressure nitrogen-based dielectric barrier discharge (DBD). Plasma treatments were carried out in two sequential steps: (1) nitrogen with 0.1% oxygen addition, and (2) nitrogen with 5% ammonia addition. The analyses show that the concentration of N/C ratio, surface energy, contact angle, and surface roughness of the treated PLA surface can reach 19.1%, 70.5 mJ/m(2), 38° and 73.22 nm, respectively. In addition, the proposed two-step plasma treatment procedure can produce a PLA surface exhibiting almost the same C2C12 cell attachment and proliferation performance as that of the conventional gelatin coating method. Most importantly, the processing/preparation time is reduced from 13-15 h (gelatin coating method) to 5-15 min (two-step plasma treatment), which is very useful in practical applications.

Application of porous oxide layer in plastic/metal direct adhesion by injection molding

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 3–8 MPa with 7–20% surface porosity.

Analysis of InAsN quantum dots by transmission electron microscopy and photoluminescence.

Quantum dots (QDs) have great potential in optical fiber communication applications were widely recognized. The structure of molecular beam epitaxy (MBE) grew InAsN QDs were investigated by transmission electron microscopy (TEM) and measured their optical properties by photoluminescence (PL). TEM images show that the InAsN QDs are irregular or oval shaped. Some of the InAsN QDs are observed to have defects, such as dislocations at or near the surface in contrast to InAs QDs, which appear to be defect free. PL results for InAsN QDs showed a red-shifted emission peak. In addition, the InAsN emission peak is broader than InAs QDs, which supports the TEM observation that the size distribution of the InAsN QDs is more random than InAs QDs. The results show that the addition of nitrogen to InAs QDs leads to a decrease in the average size of the QDs, bring changes in the QDs shape, compositional distribution, and optical properties.

Extrusion of three-layer composite hexagonal clad rods

Abstract Composite clad rods consisting of three different materials are applied extensively as conductors, electrodes and chemical devices. Commercial applications involving low temperature niobium–tin alloy (Nb 3 Sn) superconductor rods, which have a pure niobium (Nb) core, a copper–tin (Cu–Sn) alloy outer sleeve and a Nb 3 Sn diffusion layer in between, stipulate these conductors as, electrodes that are intended for processing as rods of various shapes. During the extrusion process, non-homogeneous deformation tends to occur because the billet consists of materials with different mechanical properties. In this study, the authors present a numerical simulation model based on the upper-bound theorem to analyze three-layer composite clad rods with a hexagonal cross-section under extrusion. A velocity field is also generated with the assistance of a product’s cross-section profile functions. The velocity component in the extrusion axis is expressed as a convex distribution. Analytical results indicate that various process variables such as the semi-die angle, reduction of area, friction condition of the die and combinations of the three constituent materials, prominently influence the extrusion process. Moreover, the extrusion pressure, product dimension-change and the probability of sound extrusion are related closely to the process variables.

Improving the adhesion of plastic/metal direct bonding by injection moulding using surface modifications

Abstract In this work, the surface of aluminium alloy A5052 thin plate was treated by chemical etching and atmospheric plasma before applying primer to enhance its adhesion with PC/ABS under insert moulding. The chemical etching was conducted with an ammonia aqueous solution; nanostructures were produced on metal surface, namely to increase the mechanical interlocking effect between polymer and metal. In another experiment, DBD atmospheric plasma treatment was used to clean and activate polar groups on the surface. In general, the chemical change affects bonding strength significantly in the case of A5052/PC + ABS hybrids, the bonding strength improved 2.5 times after the two-step process of chemical etching and plasma treatment.

Joint strength of Ag–9Pd–9Ga brazed interconnect and anode-supported electrolyte for solid-oxide fuel cell applications

A newly developed Ag–9Pd–9Ga active filler was vacuum brazed, and the mechanical properties between the metallic interconnects (SS430, Crofer22 APU, Crofer22 H) and a Ni–yttria-stabilized zirconia cermet anode were systematically investigated. The results indicate that the bonding between metal and cermet is well established and that the interface is smooth. The joint strength evaluated at both 25 ℃ and 800 ℃ under shear and tensile loading conditions confirmed that the brazed Ag–9Pd–9Ga sealant compared favorably with its commercially available glass-ceramic GC-9 counterpart.