Seon-Bong Lee

Development of optimal layout design system in multihole blanking process

Abstract In order to produce precision integrated circuit (IC) leadframe, it must be done through try-error. IC leadframe needs the precision shape for good efficiency. The blanking of sheet metal using progressive dies is an important process on production of precision electronic machine parts. Especially, the main defect is lead shift of inner leads in progressive blanking process. In this paper, FE simulation technique has been proposed to predict the deformation behavior and springback of IC leadframe through the simulation of the progressive blanking process. It predicts the shape of the stamped component after forming, trimming and springback for inner leads. The next blanking process is executed repeatedly until the final blanking of lead. From the results of FE analysis using suggested method in this research, it is possible to predict the lead shift of leadframe to manufacture high precision leadframe in progressive blanking process and these results might be used as a guideline to optimize layout design system in multihole blanking process.

Joining High-Strength Steel and Al6061 Sheet Using Hole Clinching Process

The joining of aluminum and HSS (high-strength steel) by the conventional clinching process is limited by the low formability of HSS. Defects in the clinching joint, such as necking of the upper sheet, cracks, and lack of interlocking, are produced by the different ductility properties of HSS and aluminum. In this study, we propose the hole clinching process for joining Al6061 and SPFC440, in which deformation of SPFC440 is avoided by drilling a hole in the SPFC440. The dimensions of the interlocking in the hole-clinched joint necessary to provide the required joint strength were determined. Based on the volume constant of the hole clinching process, the shapes of the tools were designed by finite element (FE)-analysis. A hole clinching experiment was performed to verify the proposed process. A cross-section of the joint showed good agreement with the results of the FE-analysis. The lap shear strength was found to be 2.56 kN, which is higher than required joint strength.

Development of Three-Dimensional Strip Profile Model for Thin-Foil Cold Rolling

Accurately predicting the strip profile after thin-foil cold rolling is very difficult because of the thinness of the strip. In this study, a three-dimensional (3D) strip profile model was developed to improve the accuracy of a rolled thin-foil profile. The distribution of the contact pressure between rolls (i.e., the work, intermediate, and backup rolls) and the rolling pressure between the strip and work roll were calculated by using the geometric structure of a 6-high mill and boundary conditions imposed in the width direction by a numerical method. The rolling pressure distribution in the rolling direction was determined by Flecks model of thin-foil rolling. The 3D rolled-strip profile was predicted by using the pressures in the width and rolling directions. In order to investigate the effect of the rolling speed and rise in strip temperature on the lubrication, the friction coefficient was estimated through an analytical method and experiments to test the viscosity and friction. The resulting 3D strip profile was verified by a thin-foil cold rolling test and was compared with the profile obtained using the proposed 3D model and finite element simulation.

Estimations of the Adhesion Strength of Galvannealed Coatings on Coated Sheet Using Single Lap-Shear Test

This paper was designed to estimate the adhesion strength of galvannealed coatings on steel sheets. The adhesion strength were evaluated using single lap - shear tests where the lap joint was bonded by structural adhesive. Tests were performed for overlap length of 5mm, 10mm and 15 mm and three directions (0, 45, 90) of steel sheets used as the adherend of the overlap joint. After the tests, FE simulations of the single lap - shear test were also carried out to observe the stress distribution in the interface between the adhesive and the coated sheet. The results showed that the joint failure loads obtained from the tensile tests of bonded single lap-joints were the same, regardless of overlap lengths and directions of steel sheets. Also, the failure of galvannealed coatings greatly depended on shear stress distribution in the interface and the value was about 30MPa.

Analysis of Homogenized Laser Beam Display by a Polymeric Stretchable Diffuser

Abstract A stretchable polymeric membrane shaped diffuser was used to homogenize the coherent laser beam. The developed RGB module was used to focus and defocus test by beam combiners. Average oscillation frequency was set at 180Hz~300Hz and it resulted in the best homogenization effect in visual range. The blue laser module turned out to be the worst case for the transmission and primary reason is believed to be the short length of irradiated laser beam. The developed system removed the speckling and the brightness was decreased by 10 ~ 20% for the RGB laser. Overall the brightness was decreased by 13% and homogenity with respect to the temporal axis was improved from 30fs to 110fs. Key Words : Diffuser, Head up display (HUD), Laser, Speckle patterns, Stretchable polymer * Corresponding Author : Jae-Won Lee(Keimyung Univ.)Tel: +82-10-5000-2381 email: darkjaewon@nate.comReceived September 17, 2013 Revised (1st October 16, 2013, 2nd October 21, 2013) Accepted January 9, 2014

Delamination Limit of Aluminum Foil-Laminated Sheet During Stretch Forming

An aluminum foil-laminated sheet is a laminated steel sheet on which aluminum foil is adhesively bonded. It is usually used on the outer panel of home appliances to provide an aluminum feeling and appearance on the surface of the product. The delamination of aluminum foil is one of the main problems during the stretch forming process. The purpose of this study is was to determine the delamination limit of an aluminum foil-laminated sheet in the stretch forming process. The delamination was dependent on the bonding strength between aluminum foil and steel sheet. The fracture behavior of the interface between the aluminum foil and the steel sheet was described by a cohesive zone model. A finite element was conducted with the cohesive zone model to analyze the relationship between the delamination limit and the bonding strength of the interface. The interface bonding strength was evaluated by lap shear and T-peel test. The delamination limit of the aluminum foil-laminated sheet was determined by using the bonding strength of the steel sheet. The delamination limit was also verified by the Erichsen test.

Study on control system design for washer fluid heating system

This paper presents the design of a control system for improving performance of a washer fluid heating system (WFHS) which is capable of removing frost, ice, snow and/or other debris from windshield. First, for the WFHS, a modeling process is described, and the extraction of characteristic parameters of the model are made by experimental studies. Design variables that affect on performance of the WFHS are also presented. Secondly, a control system is proposed for improving heating performance of the WFHS, and its performance is verified through experiments. The key feature of the proposed control system is to regulate the current of a booster converter input to the WFHS up to the target value that is set to guarantee heating performance. Target current is calculated by using initial temperature value and employing the mathematical model derived in the paper. Computer simulation and experimental results show that the proposed control system can perform heating operations in a way to satisfy per-determined target performance of the WFHS.

Determined Car Door Latch Injection Molding Process Conditions through the Finite Elements Analysis

Injection molding is a method for manufacturing many products, wherein a plasticized resin is injected into a mold at high pressure and hardened. According to the method, the product can be manufactured into various forms, and the mass production of up to tens of thousands of products is possible. The purpose of this study was to determine the process conditions for manufacturing a door latch for automobiles, through an analysis of the injection molding method. To calculate an appropriate injection flow for injection molding, a primary analysis for comparing the injection time, pressure, flow pattern, consolidation range, shear stress, shear rate, and weld line, as well as a secondary analysis for determining the conditions for stabilizing the molding temperature, holding pressure, and cooling process, were conducted. The characteristics of injection molding, and their influence on the product quality are discussed. No weld line and pores were observed on the products that had been manufactured based on the process conditions determined above. In addition, there were no flaws regarding the deformation compared to the prototype. Therefore, the manufacture of a product under the conditions determined in this study can reduce the defect rate compared to the existing production, and the process is also more competitive due to reduced production time.

Process Design of Trimming to Improve the Sheared-Edge of the Vehicle Door Latch based on the FE Simulation and the Taguchi Method

Automobile door latch is a fine design and assembly techniques are required in order to produce them in a small component assembly shape such as a spring, injection products, a small-sized motor. The door latch is fixed to not open the door of the car plays an important role it has a direct impact on the drivers safety. In this study, during trimming of the terminals of the connector main components of the car door latch, reduce rollover and conducted a research to find a suitable effective shear surface. Using the Taguchi method with orthogonal array of Finite Element Analysis and optimal Design of Experiments were set up parameters for the shear surface quality of the car door latch connector terminals. The design parameters used in the analysis is the clearance, the radius, and the blank holding force, the material of the connector terminal is a C2600. Trimming process optimum conditions suggested by the analysis has been verified by experiments, the shear surface shape and dimensions of a final product in good agreement with forming analysis results.Taguchi method from the above results in the optimization for the final rollover and effective shear surface improved for a vehicle door latch to the connector terminal can be seen that the applicable and useful for a variety of metal forming processes other than the trimming process is determined to be applicable.

Development of Proving Ground Test Mode for Durability Test of Active Suspension System

It is important that proving ground damage is correlated with target customer usage. This paper describes the test mode for durability test of active suspension control system for proving ground correlation and optimization. Acceleration, strain, wheel force and other types of data are collected on a vehicle as it traverses different proving ground surfaces. The primary objective of the analysis is to determine which mixture of proving ground surfaces offers the best representation of customer usage while minimizing the total test time. And durability testing offers the best way to assess the capability of a product to reach its reliability target. The test should be representative of the real environmental load and replicate the same customer usage.