Soon-Man Kwon

Expression for Surface Roughness Distribution of FDM Processed Parts

Rapid prototyping (RP) processed parts are mainly fabricated by layered manufacturing process. Hence stair steps occur at surface of the part and affect the quality of the surface. Also, the surface roughness by the stair step depends on surface angle. Therefore, prediction of the surface roughness distribution by the change of surface angle for a part to be processed is required on the process planning stage of the RP. This paper proposes a methodology to express surface roughness distribution of the part which is processed by the FDM. In order to reflect actual roughness distribution in computing, a surface roughness distribution equation is presented based on interpolation using measured roughness values. And, the computing accuracy by the number of the measured roughness data is analyzed. The implemented results show that the proposed methodology can be practical.

A Study on Optimal Wear Design for a Gerotor Pump

A disadvantage in the design of gerotor pump is a lack of parts that can be adjusted to compensate for wear in the rotor set, and as a consequence, it causes a sharp reduction of efficiency. In this paper, an attempt has been made to reduce the wear rate between the rotors of a gerotor pump. To do this, floating genetic algorithm (FGA) is used as an optimization technique for minimizing the wear rate proportional factor (WRPF). The result shows that the wear rate can be reduced considerably, e.g. approximately 8% in this paper, throughout the optimization using FGA.

Contact Surface Fatigue Life for RPG System

A roller pinion gear (RPG) system composed of either a pin or a roller and its conjugated cam gear can improve the gear endurance from that of a conventional gear system by reducing the sliding contact while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection condition obtained when the profile shift coefficient is introduced. Then, we investigated the Hertzian contact stresses and the load stress factors while the varying the shape design parameters to predict the gear surface fatigue life, which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

Pitting Life for RRP System

A roller rack pinion (RRP) system, which consists of a rack-bar and a cam pinion, transforms a rotation motion into a linear one. The rack-bar has a series of roller trains, and meshes with the cam pinion. This paper first proposes the exact tooth profile of the cam pinion and the non-undercut condition to satisfy the required performance by introducing the profile shift coefficient. The paper then investigates the load stress factors under various shape design parameters to predict the gear surface fatigue limit, which was strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly with an increase in the profile shift coefficient.

Contact Fatigue Life for CRG System

A cam ring gear (CRG) system based on a hypotrochoid curve consists of a pinion with roller teeth and its conjugated internal CRG. In this study, we investigated contact forces, contact stresses, and load stress factors to predict the surface pitting life using an exact CRG profile by introducing the profile modification coefficient. The results show that the pitting life can be extended significantly by increasing the profile modification coefficient without any other change of parameters in the CRG system.

New shape design method of an epicycloidal gear for an epicycloid drive

This paper proposed a new approach to the shape design of an epicycloidal gear, which is a key part of an epicycloidal drive with a fixed outer ring. Applying the concept of instant center of velocity of a contact mechanism to the drive, this paper derived the analytical equation fot designing the epicycloidal plate gear, including the generation of curve conjugated to the pin-tooth of an outer ring and the calculation of transmission angles and determination of the contact points. This method has been completed by three steps: the first is to find the instant center of velocity for the epicycloidal drive; the second is to determinate the transmission angles and the contact points in the special coordinate systems; and the last is to generate the full shape of the epicycloidal gear by the coordinate transformation technique. A program for design automation of shape of the cycloidal gear has been developed with C++ language. Finally, an example was given to demonstrate the feasibility of the application.

A study on wear characteristic for oscillating disc cam mechanism using GA

In the cam mechanism, the problem of surface fatigue or wear becomes more severe at contact point between cam and roller follower. The more fatigue or wear is, the less the lifetime is. As well as it leads to loss of engine performance, so to reduce the surface fatigue or wear is the primary problem to solve. In this paper, a general polynomial function developed by Thoren, Engemann, and Stoddart (TES) with real values of exponents is selected and genetic algorithm (GA) is used to decrease the surface fatigue by minimizing the wear rate proportional factor (WRPF) since they vary directly. Therefore, an attempt of this paper has been made to minimize the maximum value of WRPF using GA as the optimization program. And the results show that the minimum the maximum WRPF can be lowered approximately 10% in this paper.

Optimal wear design for a gerotor pump using genetic algorithm

A gerotor pump has various advantages such as compact size lower noise, less emissions and little pressure ripples for circulation of the fluid, but also it has a disadvantage without adjustable parts to compensate wear between the contact patch because of continuous contact during operation. Wear causes a sharp reduction of volumetric efficiency of pump. This paper presents the optimal design approach for a wear characteristic. It has been made to reduce the wear rate between the rotors of a gerotor pump. This paper uses genetic algorithm (GA) as an optimization technique for minimizing the wear rate proportional factor (WRPF). The results show that the wear rate can be reduced considerably, e.g. approximately 8%, respectively throughout the optimization using GA.

Optimization of Specific Film Thickness for a Disc Cam Using Genetic Algorithm

Abstract The rate of wear of cam followers in a valve train system is mainly a function of contact stress between the cam and the follower, sliding velocity and hydrodynamic film thickness between the two mating surfaces. The wear or surface fatigue can be reduced by maximizing the elastohydrodynamic film thickness. In this paper, an attempt has been made to estimate the optimal specific film thickness of cam-follower system quantitatively. A general TES polynomial function with real values of exponents is developed and genetic algorithm (GA) is used as optimization techniques for maximizing the minimum specific film thickness. The optimization programs enumerate values of the exponents for synthesis of cam displacement curves. The results show that the minimum film thickness can be increased considerably, e.g. approximately 7% in this paper. 1. 서 론 캠(cam)은 일반 링크 장치에 비해 구조가 간단하기 때문에 적은 부품수로 제작이 가능하고, 좁은 공간에서 다양한 운동을 얻을 수 있는 장점을 가지고 있다. 그리고 설계기술과 가공기술의 급속한 발전에 힘입어 그 활용범위가 점차 증가하고 있는 추세이다. 자동차 엔진의 밸브 트레인(valve train)용 캠의 경우 캠과 종동절(follower)간의 마찰이 엔진출력에 상당한 영향을 미치므로, 마찰을 최소화할 수 있는 윤활방식에 대한 연구가 활발히 진행되고 있다.

Theoretical Temperature Analysis for 88316 Piping Weld

In this paper, the arc beam is considered as a moving disc heat source with a pseudo-Gaussian distribution of heat intensity. The solution for temperature distribution on welds is derived by using the image heat source method and the superposition method. It is general solution in that it can determine the temperature-rise distribution in and around the arc beam heat source, as well as the width and depth of the melt pool (MP) and the heat-affected zone (HAZ) in welding short lengths, where quasi-stationary conditions may not have been established. As a comparative study, the results of this analytical approach has been compared with that of the finite-element modeling. As a result, The theoretical analysis presented here has shown good consistency and is more time/cost-effective method compared with FEM.