Seok Swoo Cho

An Effective Approach of Equivalent Elastic Method for Three-Dimensional Finite Element Analysis of Ceramic Honeycomb Substrates

A ceramic monolithic catalyst is a honeycomb structure that consists of two layers. The honeycomb structure is regarded as a continuum in structure and heat-flow analysis. The equivalent mechanical properties of the honeycomb structure were determined by performing finite element analysis (FEA) for a test specimen. Bending strength experiments and FEA of the test specimen used in ASTM C1674-08 standard test were performed individually. The bonding coefficient between the cordierite ceramic layer and the washcoat layer was almost zero. The FEA test specimen was modeled on the basis of the bonding coefficient. The elastic modulus, Poissons ratio, and the thermal properties of the ceramic monolithic substrate were determined by performing the FEA of the test specimen.

Reliability Analysis and Preventive Maintenance for Fatigue Life of End Beam for Uncovered Freight Car

Increased cumulative running times of railroad vehicle brings out such degradation as wear and fatigue. It doesn`t adapt corrective maintenance which repairs a poor part after a trouble but use preventive maintenance which fixes a bad part before a trouble. There were a few researches for preventive maintenance such as inspect affairs and facilities management. They couldn`t estimate the operation reliability on railroad vehicle. Therefore, this study proposes the preventive maintenance procedure that predict repair period of end beam fur uncovered freight car using reliability function and instantaneous failure rate on the basis of fatigue test and load history data.

Study on Structural Analysis and Manufacturing of Polyethylene Canoes

Canoes are usually made from wood or FRP. However, today environment-friendly materials are preferred, and hulls made of FRP are prohibited in some countries. Polyethylene can be recycled and so is suitable for synthetic canoe construction. We used 3D Boat-Design to determine the hydrostatic properties of the canoe. Flow-structure coupled analysis was performed using ANSYS Workbench R12.1. The hull pressure and passenger weight were considered as canoe loading factors. The key parameters for the canoe are the design variables. The constraints are as follows: (1) The maximum stress must not exceed 50% of the polyethylene yield stress; and (2) the canoe weight must not exceed 50 kg. The optimal structural conditions were obtained by the response optimization process. The components of the canoe hull were manufactured from polyethylene pipes and joined by thermal fusion methods. Tests showed that the polyethylene canoe had better performance than existing canoes.

A Experimental Estimation of Thermal Fatigue at Polyethylene Boat

Material of boat hull has been used mainly with FRP composite materials until now. FRP boat hull manufacturing began to be restricted after the 2000`s under international regulation on ocean environment safety. Shipyard on a small scale has manufactured polyethylene canoe and kayak hulls. Polyethylene has the melting point lower than the existing hull materials. Thermal stress occurs on outer hull surface when the polyethylene boat hull is exposed to sunlight. If it happens everyday, boat hull undergoes fatigue damage due to thermal fatigue. Therefore, this study presents the statistical fatigue life estimation on the HDPE boat hull subject to repeated thermal stress under three point bending condition.

Study of Structural Design of Polyethylene Pleasure Boat

Boat or yacht hulls are mainly built using FRP composite materials. FRP boat hull manufacturing has been restricted since 2000 under international regulations on ocean environment safety. FRP composite materials cannot be recycled and require more than 100 years to biodegrade. Therefore, alternatives to FRP have been proposed by many boat builders. Steel, aluminum, and FRP are commonly used as boat hull materials. Their design specifications are proposed as Korean register of shipping. However, the design specifications for inexpensive materials for a small boat have not yet been studied. Small shipbuilders manufacture and sell HDPE canoes or HDPE kayaks. In this study, a hull form was designed based on actual boats. The thickness of an HDPE boat hull was determined based on ISO 12215-5 structural design specifications.

Reliability-Based Optimization for Fatigue Maintenance Planning of Freight Car

The performance of bogie decreases according as traveling distance increases. Its causes were expected to be fatigue, wear, and deterioration. Especially, maintenance coat needs about triple than manufacture cost during required life in case of container and uncovered freight car. Freight car doesn’t adapt corrective maintenance which repairs a poor part after a trouble but use preventive maintenance which fixes a bad part before a trouble. There were a few researches on preventive maintenance such as inspect affairs and facilities management. They couldn’t estimate the operation reliability on railroad vehicle. Therefore, this study proposes the preventive maintenance procedure that predict repair period of end beam for uncovered freight car using reliability function and instantaneous failure rate on the basis of fatigue test and load history data.

A Study on Optimal Design of Rocker Arm Shaft Using Improved Genetic Algorithm

This study proposes a new optimization algorithm which is combined with genetic algorithm and ANOM. This improved genetic algorithm is not only faster than the simple genetic algorithm, but also gives a more accurate solution. The optimizing ability and convergence rate of a new optimization algorithm is identified by using a evaluation function which have several local optimum and an optimum design of rocker arm shaft. The calculation results are compared with the simple genetic algorithm.

Optimum Design of Vent Pipe of Fire Station by Using Analytical Approach of Heat Transfer

This paper presents the optimal design of vent pipe in a fire station by using design of experiments and analytical method of heat transfer theory. In order to calculate formulation without using tables, equations in terms of temperature are developed for five air properties such as specific heat, thermal conductivity, kinematic viscosity, density and Prandtl number. It is shown that the equations accurately approximate the variations of air properties in terms of temperature. Series of design analysis are performed under considering the process parameters such as inlet temperature, pipe diameter and heat transfer rate. Orthogonal arrays of L27 are used. The signal-to-noise (S/N) and analysis of variance (ANOVA) are utilized to determine the effect of parameters on objective functions, surface temperature and outlet temperature. From the results it is clear that inlet temperature is prominent on objective function.

Failure Stress Estimation of Table Liner for Vertical Roller Mill

A roller mill is composed of several rollers, rotational table liners, hydraulic cylinders and raw materials are ground between the rollers and the table with the assistance with a shearing and compressive force. It has been reported that an unexpected fatigue failure occurred in a table liner in the course of grinding portland cement. It is subjected to the cyclic bending stress by the rollers load and the centrifugal force by the table rotation and fractures at the edge of grinding path of outer roller. It demands design life 4×107 cycles but has fatigue life 4×106 ~ 8×106 cycles. The purpose of this study is to reveal the failure mechanism of the table liner occurring in the grinding operation of roller mill and to show the structural design guidelines for reducing the fatigue failure.

A Study on the Safety Estimation of Table Liner for Vertical Roller Mill Using HDM

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers load and the centrifugal force by rotation of table. It demands cycle but has cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner for vertical roller mill using HDM and fatigue analysis and makes the estimation for safety of vertical roller mill.