• Journal of the Korean Society for Precision Engineering
• /
• v.34 no.1
• /
• pp.65-72
• /
• 2017

The goal of this paper is to investigate the effects of out-of-plane deposition angle on product characteristics of a UV photo-curing process. Specimens are manufactured from a commercialized UV photo-curing machine, the NOBEL V1.0. The influence of the out-of-plane deposition angle of the specimen on surface characteristics, including morphology of the sloped surface, pick-to-pick distance of convex region, and roughness of the sloped surface, is examined via the observation of the sloped surface. In addition, the influence of the radius of curvature of the specimen on the surface roughness of the sloped surface is evaluated. The effects of the out-of-plane deposition angle on impact strength of specimens are investigated via Izod impact experiments. Finally, we discuss the influence of the out-of-plane deposition angle on failure characteristics of specimens for impact loads.

• Clean Technology
• /
• v.18 no.3
• /
• pp.295-300
• /
• 2012

Synthesis of well-defined particle with tunable size, shape, and functionalities is strongly emphasized for various applications such as chemistry, biology, material science, chemical engineering, medicine, and biotechnology. This study presents micromolding method for the fabrication of anisotropic particles with elegant control of curvature of covex roof. For the demostration of rapid fabrication of the particles, we have applied polydimethylsiloxane (PDMS) micromold as structure guiding template and wetting fluid to control curvature of roof of the particles. Based on this approach, we can control the radius of curvature from $20{\mu}m$ to $70{\mu}m$ with different aspect ratio of mold. In addition, wetting fluids with different wetting properties can also modulate the height and radius of curvature of the particles. We envision that this methodology is promising tool for precise control of particle shape in 3-dimensional space and new synthetic route for anisotropic particles with cost effective, simple, easy, and fast procedure.

• Transactions of Materials Processing
• /
• v.4 no.1
• /
• pp.28-38
• /
• 1995

An integrated process planning system can determine desirable operation sequences even if they have little experience in the design of multistage cold forging process. This system is composed of seven major modules such as input module, pre-design module, formability check module, forming sequence design module, forming analysis module, FEM verification module, and output module which are used independently or in all. The forming sequence for the part can be determined by means of primitive geometries such as cylinder, cone, convex, and concave. By utilizing this geometrical characteristics(diameter, height, and radius), the part geometry is expressed by a list of the primitive geometries. Accordingly, the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the dimensional tolerances and the proper sequence of operations for parts, is generated under the environment of AutoCAD. Several forming sequences generated by the planning system can be checked by the forming analysis module. The acceptable forming sequences can be verified further, using FE simulation.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.2
• /
• pp.195-202
• /
• 2002

An automated process planning system for cold forging of non-axisymmetric parts of comparatively simple shape was developed in this study. Programs for the system have been written with Visual LISP in the AutoCAD using a personal computer and are composed of four main modules such as input module, shape cognition and shape expression module, material diameter determination module and process planning module. The design rules and knowledges for the system are extracted from the plasticity theories, handbook, relevant reference and empirical knowledge of field experts. Generally, in forging, only front view is needed for expression of axisymmetric parts, but non-axisymmetric parts need front and plane view. At the plane, this system cognizes the external shape of non-axisymmetric, parts - number of sides of regular polygon and radius of a circle circumscribing the polygon of n sides. At the front view, the system perceives diameter of axisymmetric portions and height of primitive geometries such as polygon, cylinder, cone, concave, convex, etc.

• Kyungpook Mathematical Journal
• /
• v.48 no.3
• /
• pp.359-366
• /
• 2008

Let A(p) be the class of functions $f\;:\;z^p\;+\;\sum\limits_{j=1}^{\infty}a_jz^{p+j}$ analytic in the open unit disc E. Let, for any integer n > -p, $f_{n+p-1}(z)\;=\;z^p+\sum\limits_{j=1}^{\infty}(p+j)^{n+p-1}z^{p+j}$. We define $f_{n+p-1}^{(-1)}(z)$ by using convolution * as $f_{n+p-1}\;*\;f_{n+p-1}^{-1}=\frac{z^p}{(1-z)^{n+p}$. A function p, analytic in E with p(0) = 1, is in the class $P_k(\rho)$ if ${\int}_0^{2\pi}\|\frac{Re\;p(z)-\rho}{p-\rho}\|\;d\theta\;\leq\;k{\pi}$, where $z=re^{i\theta}$, $k\;\geq\;2$ and $0\;{\leq}\;\rho\;{\leq}\;p$. We use the class $P_k(\rho)$ to introduce a new class of multivalent analytic functions and define an integral operator $L_{n+p-1}(f)\;\;=\;f_{n+p-1}^{-1}\;*\;f$ for f(z) belonging to this class. We derive some interesting properties of this generalized integral operator which include inclusion results and radius problems.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.4
• /
• pp.402-416
• /
• 1999

The thermal distributions near the growth interface of 150nm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) and edge (10nm from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat flux balance equation. Using this fact, it is confirmed in CZ crystals that the type of point defects created is determined by the value of the thermal gradient(G) near the interface during growth, as already reported for FZ crystals. Although depending on the growth systems the effective length of the thermal gradient for defect generation are varied, we defined the effective length as 10n,\m from th interface in this experiment. If the G is roughly smaller than 20C/cm, vacancy rich CZ crystals are produced. If G is larger than 25C/cm, the species of point defects changes dramatically from vacancies to interstitials. The experimental results after detaching FZ and CZ crystals from the melt show that growth interfaces are filled with vacancies. We propose that large G produces shrunk lattice spacing and in order to relax such lattice excess interstitials are necessary. Such interstitials recombine with vacancies which were generated at the growth interface, nest occupy interstitial sites and residuals aggregate themselves to make stacking faults and dislocation loops during cooling. The shape of the growth interface is also determined by te distributions of G across the interface. That is, the small G and the large G in the center induce concave and convex interfaces to the melts, respectively.

• Transactions of Materials Processing
• /
• v.25 no.3
• /
• pp.182-188
• /
• 2016

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to producing multi-curvature surfaces by controlling the strain distribution along longitudinal direction. In FRRF, a sheet metal is shaped into the desired curvature by using reconfigurable rollers and gaps between the rollers. As FRRF technology and equipment are under development, a simulation model corresponding to the physical FRRF would aid in investigating how the shape of a sheet varies with input parameters. To facilitate the investigation, the current study exploits regression analysis to construct a predictive model for the longitudinal curvature of the sheet. Variables considered as input parameters are sheet compression ratio, radius of curvature in the transverse direction, and initial blank width. Samples were generated by a three-level, three-factor full factorial design, and both convex and saddle curvatures are represented by a quadratic regression model with two-factor interactions. The fitted quadratic equations were verified numerically with R-squared values and root mean square errors.

• Structural Engineering and Mechanics
• /
• v.17 no.5
• /
• pp.611-626
• /
• 2004

On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

• Geomechanics and Engineering
• /
• v.35 no.4
• /
• pp.411-424
• /
• 2023

Reasonable estimates of tunnel lining dislocations in the operation stage, especially under longitudinal differential settlement, are important for the design of waterproof gaskets. In this paper, a modified shell-joint model is proposed to calculate shield tunnel dislocations under longitudinal differential settlement, with the ability to consider the nonlinear shear stiffness of the joint. In the case of shell elements in the model, an elastoplastic damage constitutive model was adopted to describe the nonlinear stress-strain relationship of concrete. After verifying its applicability and correctness against a full-scale tunnel test and a joint shear test, the proposed model was used to analyze the dislocation behaviors of a shield tunnel in Shanghai Metro Line 2 under longitudinal differential settlement. Based on the results, when the tunnel structure is solely subjected to water-earth load, circumferential and longitudinal joint dislocations are all less than 0.1 mm. When the tunnel suffers longitudinal differential settlement and the curvature radius of the differential settlement is less than 300 m, although maximum longitudinal joint dislocation is still less than 0.1 mm, the maximum circumferential joint dislocation is approximately 10.3 mm, which leads to leakage and damage of the tunnel structure. However, with concavo-convex tenons applied to circumferential joints, the maximum dislocation value reduces to 4.5 mm.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1999.06a
• /
• pp.187-207
• /
• 1999

The thermal distributions near the growth interface of 150mm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) and edge (10m from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat flux balance equation. Using this fact, it si confirmed in CZ crystals that the type of point defects created is determined by the value of the thermal gradient (G) near the interface during growth, as already reported for FZ crystals. Although depending on the growth systems the effective lengths of the thermal gradient for defect generation are varied, were defined the effective length as 10mm from the interface in this experiment. If the G is roughly smaller than 20C/cm, vacancy rich CZ crystals are produced. If G is larger than 25C/cm, the species of point defects changes dramatically from vacancies to interstitial. The experimental results which FZ and CZ crystals are detached from the melt show that growth interfaces are filled with vacancy. We propose that large G produces shrunk lattice spacing and in order to relax such lattice excess interstitial are necessary. Such interstitial recombine with vacancies which were generated at the growth interface, next occupy interstitial sites and residuals aggregate themselves to make stacking faults and dislocation loops during cooling. The shape of the growth interface is also determined by the distributions of G across the interface. That is, the small G and the large G in the center induce concave and convex interfaces to the melt, respectively.