Jae Soo Hong

Anthropometric and Standing Action Analysis for Electric Adjustable Bed

ABSTRACT Recently, the frequency in use of electric adjustable bed is going up by an increase in the elderly population. In bad ergonomic design for an electric adjustable bed causes some problems in the aspects of usability and safety. In particular, lots of accidents came from going up or going down an electric adjustable bed. In that case, the height of bed is very important factor for preventing an accident. This problem is related to its anthropometric factors. Therefore we carried out its anthropometric analysis and old peoples standing action according the height of electric adjustable bed as an experimental study. As a result, we proposed some anthropometric design criteria and identified the effect of bed height when old people use it. Keyword: Electric adjustable bed, Anthropometric analysis, Standing action, EMG 1. 서 론 1.1 연구배경 및 목적 최근 노인인구가 증가함에 따라 대한민국은 이미 고령사회로 접어들었고, 초 고령사회로 나아가고 있다. 이에 맞춰 노인복지에 관련된 많은 제도가 시행되게 되었으며 복지용구의 수요도 증가하게 되었다. 따라서 복지용구는 점차 노인의 삶을 윤택하게 하는 선택사항이 아닌 기본적인 필수용품으로 받아들여지고 있다. 본 연구는 여러 가지 복지용구 중에서 하루 생활의 시작과 종료를 함께하는 침대에 대해서 다루었다. 그리고 특히 고령자가 스스로 활동할 수 있도록 편리한 기능을 제공하는 전동침대는 노인장기요양보험의 급여대상 품목에 추가되어 그 필요성이 더욱 높아지고 있다. 현재 전동침대는 매우 다양한 제품이 출시되고 있으며 사용자층도 노약자뿐만 아니라 일반인에 이르기까지 넓어지고 있다. 하지만, 전동침대가 가장 절실하게 필요한 노인요양시설과 같은 곳의 노인들의 특성을 잘 반영하여 설계된 제품은 그리 많다고 할 수 없다. 전동침대는 주된 사용자가 고령자 및 환자인 만큼 안전이 매우 중요한 요소이다. 그 중에서 노인에게 주로 발생하는 낙상사고에 관한 문헌조사에 따르면 낙상의 주요 환경적 요인으로는 침대 높이나 화장실 내의 어두운 조명등의 환경적

A Study on Wear and Wear Mechanism of Exhaust Valve and Seat Insert Depending on Different Speeds Using a Simulator

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350°C, and the test load was 1960 N. The test cycle number was 6.0×106. The mean (±standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 (±3.7)μm and 81.7 (±2.5)μm, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 (±3.9) μm and 91.2 (±2.7) μm, respectively. In the case of multi-Hz it was 70.7 (±2.4)/on and 77.4 (±3.8) μm, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.

Engine valve and seat insert wear depending on speed changes

Abstract The minimization of valve and seat insert wear is a critical factor for consideration in the pursuit of engine performance improvement. In order to achieve this goal, an innovative simulator was developed with the ability to generate and control high temperatures up to 900°C and various frequencies up to 80 Hz during motion, just as in the case of an actual vehicle engine. This wear simulator is considered to be a valid reproduction of the engine valve and seat insert wear process operating with various speeds during engine activity. This work focuses on the different degrees of wear at three different test frequencies (10 Hz, 25 Hz, and multi-hertz). In this study, the seat inserts exterior surface temperature was controlled at 350 °C, the number of cycles was 2.1×106and the test load was 1960 N. The wear depth was measured before and after testing using a confocal laser microscope. It was found that higher frequencies caused a greater degree of wear than lower frequencies under identical test conditions (temperature, valve displacement, number of cycles, and test load). It was intended that an actual vehicle engine be used to perform a similar test, in order that the multi-hertz test, using a combination of the 10 and 25 Hz frequencies be applied. In the wear mechanism, adhesive wear, shear strain, abrasive wear, and surface fatigue wear were observed.

Comparison of the wear exerted on engine valves and seat inserts under various speeds and mileages

Abstract Under actual engine driving conditions, there is a possibility of engine valve and seat insert wear occurring as a result of various speed changes and accumulation of mileage. It is therefore necessary to examine the wear-related problems of engine valves and seat inserts and to determine by comparison whether speed or mileage inflicts the greater wear. This work focuses on the various degrees of wear produced at three different singular test speeds (10 Hz, 25 Hz, and multi-Hz) and two different cycle numbers (2.1 — 106 and 6.0 — 106). Throughout all tests performed in this study, the temperature of the outer surface of the seat insert was controlled at 350°C and the test load was 1960 N. Wear depths were measured using a confocal laser microscope, and wear mechanisms were observed using a scanning electron microscope. The extent of wear produced at higher speeds (25 Hz) was found to be greater than that produced at lower speeds (10 Hz) under identical test conditions (temperature, valve displacement, cycle number, and test load). Although test cycle numbers were increased by a factor of 3, for example from 2.1 — 106 to 6.0 — 106, the wear depths were not proportionally increased. Wear occurred rapidly during the initial stages of the test and wear depths increased less significantly with each cycle number. Wear depth of the 2.1 — 106 cycle number test at 25 Hz was much larger than that of the 6.0 — 106 cycle number test at 10 Hz in both the valve and the seat insert. Therefore, this result indicates that speed (Hz) might have a greater effect than mileage (cycle number) on the valve and seat insert while the engine is running. As the cycle number was increased, the wear depth at multi-Hz showed a tendency to near the wear depth at 25 Hz (high speed) rather than that at 10 Hz (low speed). Adhesive wear and shear strain were observed in the wear mechanisms of the valves. Furthermore, adhesive wear and surface fatigue wear were observed in the wear mechanisms of the seat inserts.