Jaedeuk Yun

Development of a gap searching program for automotive body assemblies based on a decomposition model representation

We suggest a method of locating gaps between the parts of an assembly automatically.We propose an algorithm to define the boundary between the exterior and the gaps.The developed program can visualize gaps of less than 1mm in a specified region.It can help to avoid design changes and repair processes while developing products.Application of the method can also be extended to aircraft and ship designs. Automobiles, aircraft, and ships require tremendously many parts to be assembled. For developing such large assemblies, most companies accelerate the design process by having many design engineers in different functional or sectional design groups working concurrently. However, interferences and gaps can be found when the parts and sub-assemblies of different design groups are to be assembled. These error cause design changes and additional repair processes, resulting in an unexpected increase in costs and time delays. While the interference problem has been resolved by digital mockup and concurrent engineering methodology, many cases of the gap problem in the automotive industry have been covered by temporary treatments when the gaps are small enough to be filled with sealants. This kind of fast fix can cause leakage into the engine chamber and passenger cabin when the gap size is too big for filling or when the sealant gets old, which can turn fatal. With this research, we have developed a program to automatically find gaps between the parts of an assembly so that design engineers can correct their designs before the manufacturing stage begins. By using the method of decomposition model representation, the program can visualize gaps between complex car body parts as well as estimate their volumetric information. It can also automatically define the boundary between a gap and the exterior space. Although we have reviewed the benefits of the program by applying it to car development, it can also be applied to aircraft and ship designs comprising several parts.

Filament winding path generation based on the inverse process of stability analysis for non-axisymmetric mandrels

Obtaining reliable winding paths for non-axisymmetric shapes with current filament winding technologies is still a challenge. In this study, an algorithm was developed for generating geodesic and non-geodesic paths that are slippage- and bridging-free and can be applied to axisymmetric as well as non-axisymmetric mandrel models represented by triangular meshes. By performing a stability analysis on the winding path on a curved surface, the non-slipping and non-bridging conditions on a triangular mesh are deduced. Then, according to the inverse process of stability analysis, the next path point that satisfies the stability conditions is determined. In this method, the surface normal vector is calculated by a geodesic rather than via the weighted average method. Consequently, a stroke of the winding path is constructed by adding the next path point recursively. In addition, strategies for generating stable paths on a mandrel surface that includes concave regions are presented to avoid bridging.

Real-time graphic visualization of filament band winding for fiber-reinforced cylindrical vessels:

The filament winding method is widely used to manufacture lightweight, strong, composite products. To reduce winding time, the method of winding by filament band, which consists of several roving tows, is used. A computer numerical control winding machine is used with input path commands for precise winding operation. Before filament winding, users should verify by simulation that the input path is appropriate for the winding without any erroneous operation. Furthermore, prior to starting the winding operation, the usage length of each tow must to be checked because the manufacturing process stops unexpectedly if the tow on the creel runs out. In this work, we used the geodesic equation to generate a filament band surface and calculate the usage length of each tow. We also proposed a graphic display method to make the visual effect in accord with the real winding process. To verify the presented algorithm, a program for three-dimensional real-time graphic visualization of filament band winding process was developed.

Development of a Car Door Checker for Reducing Noise in Opening

A door checker holds a car door at several opening angles and limits the maximum door opening, so that the door does not bump against to passengers. Recently, the performance of door checker becomes more important as the feeling of door opening and closing effects on the quality of a car. However, some of door checkers make squealing noise when they are used for ages, which causes consumers complaints as well as decreasing commercial value of the product. In this study, after various experiments for the noise, we concluded that the major reasons of the noise are acceleration of wearing and loss of lubricant due to impurities in working parts. Therefore, we developed a new mechanism of door checker which can resolve the major reasons of the noise. The developed mechanism is effective to prevent inflow of impurities and loss of lubricant by locating working parts in the case. We also proved that the developed mechanism does not make any noise after the test of 50,000 times of operations.

Analytical Model for the Analysis of Pop-up Deviation of the Trunk Lid with Torsion Bar

A four-link mechanism consisting of torsion bars is used for opening the trunk lid in most midsize sedans. When the weight of the lid is in equilibrium with the spring force exerted by torsion bars, the lid stops opening at a pop-up height. However, the actual pop-up height has large deviations from the specified height even with the same parts in the same car model, which leads to quality issues. Automotive manufacturers have experienced this deviation problem despite much effort to resolve it. In this research, we developed a multi-body dynamics model for the analysis of pop-up deviation of a trunk lid with torsion bars, which can simulate the actual pop-up motion of the trunk lid by considering kinematic constraints of the motion and friction forces in joints. We could also determine the most important factor that governs the pop-up height by sensitivity analysis of all parts. The developed system can be used for the analysis of other trunk lid systems to control the tolerance of parts.

Filament Band Winding Simulation for Fiber Reinforced Cylindrical Pressure Vessels

Received 29 August, 2013; received in revised form 10 December, 2013; accepted 12 December, 2013ABSTRACTThe filament winding method is widely used to manufacture products of fiber reinforced plas-tics (FRP), such as high pressure vessels, launch tubes and pipes. For reducing winding time,the method of winding by filament band which consists of several filament fibers is used. NCwinding machine is used for precise winding and NC path is needed. Before filament winding,users should verify that winding path which presented by a line is appropriate by filament wind-ing simulation. Also, the used length of each filament is different. So, if the peak filamentexhausted, it causes to stop manufacturing. In this research, we developed software which visu-alizes 3D graphic of filament band winding path and simulates winding process on real time.And we proposed algorithm about calculation of each filament usage. We use geodesic equa-tion for generating filament band surface and calculating the usage length of each filament. Key Words: Composite material, Fiber path, Filament winding, Vessel, Winding simulation

Development on mechanism for opening sensitivity quality improvement of oven range door using nonlinear cam and spring

Abstract Most of oven range doors are opened from top to down. Feeling of door in case of home appliances including oven ranges affects the quality of product. The major factors to evaluate the feeling quality are opening force, closing force, and bouncing effect happened when the door is opened completely. If opening and closing forces become large, consumers may have complaints. If the bouncing effect becomes large, the impact can cause the body as well as the door to damage. Opening and closing forces, and bouncing effect must be minimized to improve the feeling quality. In this study, the mechanism which improves the existed dual compressive spring and cam structure is suggested by using nonlinear cam and spring. After the nonlinear cam is designed and manufactured for the suggested mechanism, this cam is confirmed to become more superior than the existed one by applying it to the practical oven range. Key Words : Feeling quality, Non-linear cam, Oven 본 논문은 부산대학교 자유과제 학술연구비(2년)에 의하여 연구되었음.

Development of the auto leveling mechanism for side-by-side refrigerator doors

Recently the increasingly common large refrigerator is the side by side(SBS) refrigerator whose freezing chamber and refrigerating chamber are set side by side. But one of the biggest dissatisfaction of customers about SBS refrigerator is that the two doors don`t meet the same height when they are closed. It is called door height difference(DHD). The main cause of DHD is the unevenness of floor on which a refrigerator is placed or the cabinet deformation caused by long time use. When the DHD is confirmed, the customer or maintenance personnel use wrench to adjust the support screw to make the refrigerator to reach the horizontal position. But for big refrigerator, it is not only difficult for women and old people who don`t have enough force to adjust it, but also inappropriate to require customers to do this job. In order to resolve this problem, this research proposes a new mechanism which can detect the DHD and adjust two doors to the same height automatically. The adjustment would be completed during opening and closing the doors, avoid needing hard operation with wrench by hand.

Interference-free French door design using four-bar linkage mechanism

The French doors have the advantage that they can use inner space more efficiently due to without of partition between two rooms. However, when they are used for refrigerators, the door gaskets for sealing may cause interference of themselves during opening and closing, which causes fatal effect on sealing by worn out of the gaskets as well as increases door opening force. This research proposes a new mechanism for the French doors using the parallelogram motion of 4-bar linkage mechanism, which does not make any interference between gaskets. We manufactured the French doors of proposed mechanism to verify that they do not cause any interference during opening and closing, as well as opening force is decreased. The use of our developed mechanism is not limited to refrigerators, but can be extended to other industrial products with the French doors.