Browsing by Author "Hsu, RQ"

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A study on seamless tube in the planetary rolling process
(2002-02-28)
Shih, CK
;
Hsu, RQ
;
Hung, CH
;
機械工程學系
;
Department of Mechanical Engineering
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. (C) 2002 Elsevier Science B.V. All rights reserved.
A universal velocity field for the extrusion of non-axisymmetric rods with non-uniform velocity distribution in the extrusion direction
(2000-01-01)
Wu, CW
;
Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
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. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
An analysis of force distribution in shear spinning of cone
(2005-06-01)
Chen, MD
;
Hsu, RQ
;
Fuh, KH
;
機械工程學系
;
Department of Mechanical Engineering
An analytic model for calculation of shear spinning force incorporate factor of over-roll (press down) of the blank is derived. The effects of blank thickness, roller nose radius, mandrel revolution and roller feed on the spinning force are discussed. Results obtained from calculation were compared with the experiment and other theoretical predictions. It is found that the present findings yield optimum results. (c) 2005 Elsevier Ltd. All rights reserved.
Barrier capability of HfN films with various nitrogen concentrations against copper diffusion in CuHf-N/n(+)-p junction diodes
(2005)
Ou, KL
;
Chiou, SY
;
Lin, MH
;
Hsu, RQ
;
機械工程學系
Hafnium-based (Hf-N) films were prepared by reactive radio frequency (rf)-magnetron sputtering on blank silicon wafers. Nitrogen incorporation and phase transformation of hafnium-based thin film were analyzed by cross-sectional transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The as-deposited Hf film has a hexagonal close-packed structure and a low resistivity of 48.29 muOmega cm. With increasing nitrogen concentration of Hf-N film, phase transformations are identified as alpha-Hf --> HfN0.4 --> epsilon-Hf3N2 --> fcc-HfN. The thermal stability of the Cu/Hf-N/Si contact system is evaluated by thermal stressing at various annealing temperatures. For the Cu/Hf/Si contact system, the inter-facial reaction between the Hf barrier layer and the Cu layer is observed after annealing at 550degreesC for 30 min, and copper-hafnium compounds form. Highly resistive copper silicide forms after annealing at 600degreesC for 30 min. The Elf barrier fails due to the reaction of Cu and the Hf barrier, in which Cu atoms penetrate into the Si substrate after annealing at high temperature. However, no copper-hafnium and copper silicide compounds are found for the Cu/HfN0.47/Si contact system even after annealing at 650degreesC for 30 min. A hafnium diffusion barrier incorporated with nitrogen can suppress the formation of copper-hafnium compounds and copper penetration, and thus enhance the thermal stability of the barrier layer. (C) 2005 The Electrochemical Society.
Comparative study of polycrystalline Ti, amorphous Ti, and multiamoIrphous Ti as a barrier film for Cu interconnect
(2005-01-01)
Ou, KL
;
Yu, MS
;
Hsu, RQ
;
Lin, MH
;
機械工程學系
Ultrathin (10 nm) Ti films with various structures were deposited by physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes. CVD-Ti films with low-temperature (<500degreesC) plasma-enhanced chemical vapor deposition Using TiCl4 and H-2 as reactants is an amorphous structure. This result is different from PVD-Ti films. deposited by magnetron sputtering, which have a columnar structure. Ammonia plasma was further employed to post-treat the CVD-Ti barrier layer to improve barrier properties. An amorphous Ti(N,H) layer was formed on the surface of the CVD-Ti layer after ammonia plasma post-treatment. The resultant films had a bilayered amorphous Ti(N,H)/Ti structure. Furthermore, the effective resistivity of the resultant Ti(N, H) /Ti film decreased to 122 muOmega cm. The thermal stability of Cu/PVD-Ti/Si and Cu/CVD-Ti/Si contact systems was evaluated by thermal stressing at various annealing temperatures. For the Cu/PVD-Ti/Si, the highly copper titanium compound was formed after 450degreesC annealing. The PVD Ti barrier failed initially due to the reaction of Cu and the Ti barrier, in which Cu atoms penetrated into the Si substrate after annealing at high temperature. However, no copper-titanium and copper-silicide compounds were found for amorphous Ti and plasma-treated Ti[Ti(N,H)/Ti] barriers, even after annealing at 500 and 600degreesC, respectively. Improved barrier capability against Cu diffusion was found for the Ti(N,H)/Ti barrier layer because the Cu/Ti(N,H)/Ti/n(+)-p junction diodes retained low leakage current densities even, after annealing at 500degreesC for 1 h., Ti(N,H)/Ti barrier layers present lengthened grain structures to effectively impede Cu diffusion, thus acting as much more effective barriers than conventional Ti and TiN films. (C) 2005 American Vacuum Society.
Effects of over-roll thickness on cone surface roughness in shear spinning
(2005-01-10)
Chen, MD
;
Hsu, RQ
;
Fuh, KH
;
機械工程學系
;
Department of Mechanical Engineering
A high quality of cone surface finish was achieved by carefully controlled over-roll thickness in the shear spinning process. In this study, blank thickness, roller nose radius, mandrel revolution, roller feed and over-roll thickness were taken as major process variables to investigate the effects of the above parameters on the surface roughness of cone shape products. From the experiment, several sets of experimental data were obtained, which in turn were used to construct regression equations for applied forces and product surface roughness. The results were verified by four extra spinning experiments. It is found that deeper over-roll combines with the thinner blank sheet, larger roller nose radius and slower roller feed, and are advantageous for obtaining smoother surface roughness. Over-roll of the blank in shear spinning is an effective way to improve the surface roughness of the product. (C) 2003 Published by Elsevier B.V.
Extrusion analysis and workability prediction of three-layer composite hexagonal clad rods
(2006-05-25)
Wu, CW
;
Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
This study uses upper bound method to predict the workability for the extrusion of three-layer composite hexagonal clad rods. A velocity field is 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. The simultaneous deformation of each constituent material with quite different mechanical properties may lead to fracture. A criterion for fracture based on the velocity deviation existing on the layer interface was proposed. Material fractures under extrusion are affected by a set of independent process parameters, including the initial area percentage of each layer, friction condition of die, mechanical characteristics of three constituent materials and reduction of area of billet. Finally, figures of extrusion limits containing safety and fracture zones for each process parameter are obtained for extrusion of three-layer composite hexagonal clad rods. (c) 2006 Elsevier B.V. All rights reserved.
Extrusion of three-layer composite hexagonal clad rods
(2002-04-10)
Wu, CW
;
Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
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 (Nb3Sn) superconductor rods, which have a pure niobium (Nb) core, a copper-tin (Cu-Sn) alloy outer sleeve and a Nb3Sn 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. (C) 2002 Elsevier Science B.V. All rights reserved.
Forecast of shear spinning force and surface roughness of spun cones by employing regression analysis
(2001-09-01)
Chen, MD
;
Hsu, RQ
;
Fuh, KH
;
機械工程學系
;
Department of Mechanical Engineering
A series of shear spinning experiments has been performed to produce axi-symmetric cones from blank sheet. The experiments investigated influences of roller nose radius, mandrel revolution and roller feed on the spinning force and the inside/outside surface roughness of spun cone. Statistical analysis was adopted to construct the regression equations governing these parameters. Independent experiments verified the findings. It was discovered that the established regression equations possess a significant degree of reliability. (C) 2001 Elsevier Science Ltd. All rights reserved.
The finite element analysis on planetary rolling process
(2001-06-15)
Shih, CK
;
Hung, CH
;
Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
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. (C) 2001 Elsevier Science B.V. All rights reserved.
Theoretical analysis of extrusion of rectangular, hexagonal and octagonal composite clad rods
(2000-03-01)
Wu, CW
;
Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
Composite clad rods with non-axisymmetric cross-sectional areas are commercially important owing to their extensive industrial applications such as in electrodes, conductors and chemical devices. For instance, in the processing of superconductor wire, increasing the packing density involves closely packing superconductor rods which have a hexagonal cross-section next to each other inside the high purity copper tube. During extrusion process, non-uniform deformation tends to occur because the core and sleeve of a composite clad rod is usually composed of materials with different mechanical properties. The first recognized paper on round-to-square drawing/extrusion with variable corner radius was presented by Beer et al. in 1979. In this study, we present a model based on upper-bound theorem to analyze the extrusion of composite clad rods with non-axisymmetric cross-section. Velocity fields for both core and sleeve are generated with the assistance of a product's cross-sectional profile functions. Products with rectangular, hexagonal and octagonal sections are chosen as the study objects. Also discussed herein are numerical results for various process variables such as semi-die angle, reduction of area, frictional condition of die, and product shape complexity. According to these results, the extrusion pressure and product dimensional change are closely related to the process variables. (C) 1999 Elsevier Science Ltd. All rights reserved.