• 제목/요약/키워드: Lifting force

검색결과 160건 처리시간 0.03초

Fatigue effects on manual lifting acceleration

  • Kim, Y.J.;Lee, K.S.
    • 대한인간공학회:학술대회논문집
    • /
    • 대한인간공학회 1992년도 추계학술대회논문집
    • /
    • pp.18-21
    • /
    • 1992
  • The objective of this study was to investigate the effects of fatigue, caused by frequent manual lifting, on lifting velocity and lifting acceleration. Ten male volunteers performed lifting at a rate of 4 times per minute, continuously, for two hours using the free-style posture. A box $(30cm{\times}30cm{\times}20cm)$ with a fixed weight (15.9kg) was used as the load for lifting. Heart rate, oxygen consumption, and EMG were also measured to estimate the level of fatigue. The posture as well as acceleration was recorded. The results show that the lifting acceleration at the end of two hour increased significantly (20%, p<0.001) compared to the accleration after fifteen minutes of lifting. It was also found that subjects changed their lifting postures as the result of fatigue. All subjects also indicated pain in their upper legs and the lower back at the conclusion of the experiment.

  • PDF

크레인 로프의 신장을 고려한 침몰선체의 인양력 해석 (Lifting Analysis for a Sunken Ship in Consideration of Elongation of Crane Ropes)

  • 최경식;신맹기
    • 한국해양공학회:학술대회논문집
    • /
    • 한국해양공학회 2003년도 춘계학술대회 논문집
    • /
    • pp.179-184
    • /
    • 2003
  • This study focuses on an analytical approach to calculate crane lifting forces for a sunken ship in consideration oj elongation of crane ropes. The method takes into account the relation of lifting forces acting in wire rope slings to the inclination of the ship's hull including the effect of lug positions. For lifting analysis, the Euler angles are defined to represent the inclination of a sunken ship in developing the static force and moment equations. An additional compatability condition is introduced in order to solve an indeterminate lifting analysis problem with 4 cranes and a set of lifting forces along the 4 crane ropes is calculated. A 3-dimensional example of the G/T 1500 oil tanker is analyzed and the results show that the information obtained by the method could be useful to engineers to conduct salvage work.

  • PDF

A Study on the Measurement of Contact Force of Pantograph on High Speed Train

  • Seo, Sung-Il;Cho, Yong-Hyun;Mok, Jin-Yong;Park, Choon-Soo;Kim, Ki-Hwan
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 제어로봇시스템학회 2005년도 ICCAS
    • /
    • pp.1374-1378
    • /
    • 2005
  • Appropriate upward force is crucial for the pantograph on high speed train to collect current from the catenery system without separation. However, at high speed, large aerodynamic lifting force is generated by the contact plate and the arms of pantograph, which may cause wear of the contact wire. In this study, to confirm the interface performance of the pantograph on Korea High Speed Train, a method to measure the contact force of the pantograph was proposed and the related measurement system was developed. The forces acting on the pantograph were clarified and a procedure to calculate the aerodynamic lifting force was proposed. A special device was invented and applied to measure the lifting force. Measured contact forces were displayed by the developed system and evaluated according to the criteria. Countermeasures were also taken to reduce the contact force based on the results.

  • PDF

Prediction of Peak Back Compressive Forces as a Function of Lifting Speed and Compressive Forces at Lift Origin and Destination - A Pilot Study

  • Greenland, Kasey O.;Merryweather, Andrew S.;Bloswick, Donald S.
    • Safety and Health at Work
    • /
    • 제2권3호
    • /
    • pp.236-242
    • /
    • 2011
  • Objectives: To determine the feasibility of predicting static and dynamic peak back-compressive forces based on (1) static back compressive force values at the lift origin and destination and (2) lifting speed. Methods: Ten male subjects performed symmetric mid-sagittal floor-to-shoulder, floor-to-waist, and waist-to-shoulder lifts at three different speeds (slow, medium, and fast), and with two different loads (light and heavy). Two-dimensional kinematics and kinetics were captured. Linear regression analyses were used to develop prediction equations, the amount of predictability, and significance for static and dynamic peak back-compressive forces based on a static origin and destination average (SODA) backcompressive force. Results: Static and dynamic peak back-compressive forces were highly predicted by the SODA, with R2 values ranging from 0.830 to 0.947. Slopes were significantly different between slow and fast lifting speeds (p < 0.05) for the dynamic peak prediction equations. The slope of the regression line for static prediction was significantly greater than one with a significant positive intercept value. Conclusion: SODA under-predict both static and dynamic peak back-compressive force values. Peak values are highly predictable and could be readily determined using back-compressive force assessments at the origin and destination of a lifting task. This could be valuable for enhancing job design and analysis in the workplace and for large-scale studies where a full analysis of each lifting task is not feasible.

역도경기의 자세, 무게중심, 가속도가 발휘근력에 미치는 영향에 관한 생체역학적 연구 (A Biomechanical Study on Kinetic Posture, Center-of-Gravity, Acceleration and their Effects on the Maximum Capability of Weight-lifting)

  • 이면우;정경호;한성호;이긍세;이춘식
    • 대한산업공학회지
    • /
    • 제11권2호
    • /
    • pp.87-99
    • /
    • 1985
  • The purpose of this study is to analyze the changes in centers-of-gravity (COG), acceleration and body posture and their associated effects both on EMG and on the maximum capability of weight lifting during Clean & Jerk and Snatch motions. Displacement, velocity, acceleration of joints were obtained from film analysis. Also levels of exertions on 11 major muscle groups were obtained from EMG analysis during a lifting cycle. The EMG data were measured from Telemetry System which is useful in field experiments. Magnitude and direction of force, change in center-of-gravity were extracted from COG data which were measured from force platform. The results of this study can be to be useful both to coaches and to athletes in weight-lifting.

  • PDF

교량상 slab궤도의 상향력 민감도분석 (Parameteric Analysis for Up-lifting force on Slab track of Bridge)

  • 최성기;박대근;한상윤;강영종
    • 한국철도학회:학술대회논문집
    • /
    • 한국철도학회 2007년도 추계학술대회 논문집
    • /
    • pp.1188-1195
    • /
    • 2007
  • The vertical forces in rail fasteners at areas of bridge transitions near the embankment and on the pier will occur due to different deformations of adjoining bridges caused by the trainloads, the settlement of supports, and the temperature gradients. The up-lifting forces is not large problem in the blast track because the elasticity of blast and rail pad buffs up-lifting effect. But, it is likely to be difficult to ensure the serviceability of the railway and the safety of the fastener in the end in that concrete slab track consist of rail, fastener, and track in a single body, delivering directly the up-lifting force to the fastener if the deck is bended because of various load cases, such as the end rotation of the overhang due to the vertical load, the bending of pier due to acceleration/braking force and temperature deviation, the settlement of embankment and pier, the temperature deviation of up-down deck and front-back pier, and the rail deformation due to wheel loads. The analysis of the rail fastener is made to verify the superposed tension forces in the rail fastener due to various load cases, temperature gradients and settlement of supports. The potential critical fasteners with the highest uplift forces are the fastener adjacent to the civil joint. The main influence factors are the geometry of the bridge such as, the beneath length of overhang, relative position of bridge bearing and fastener, deflection of bridge and the vertical spring stiffness of the fastener.

  • PDF

4기 크레인을 이용한 선체블록의 인양력 해석 (Lifting Analysis for Ship Hull Blocks using 4 Cranes)

  • 최경식;김동준
    • 대한조선학회논문집
    • /
    • 제41권2호
    • /
    • pp.98-105
    • /
    • 2004
  • This study focuses on an analytical approach to calculate four crane lifting forces for heavy ship hull blocks considering elongations of lilting slings. Four-crane-lifting is a redundant problem. During lifting procedures, in addition to the force and moment equilibrium equations, a compatibility condition is introduced to determine 4 unknown lifting forces. For verification of the method, a ship hull block with field measurements data is analyzed and the result shows that the information obtained by current method could be useful to engineers to conduct lifting work at shipyards.

부산종합운동장 주경기장 지붕구조물의 시공 (Construction of Roof Structure for Pusan Main Stadium)

  • 이주영;유상현
    • 한국건설관리학회:학술대회논문집
    • /
    • 한국건설관리학회 2001년도 학술대회지
    • /
    • pp.228-231
    • /
    • 2001
  • 부산종합운동장 주경기장 지붕구조는 케이블현수구조로 그 시공은 VSL 리프팅시스템을 사용한 인양공법을 채택하여 이루어 졌다. 본 지붕구조물의 시공은 크게 5단계 공정으로 이루어 졌고, 상기 공정 중 인양작업은 상부케이블과 하부케이블로 나누어 1차 인양작업과 2차 인양작업으로 이루어 졌다. 본 지붕구조물의 경우 각 케이블의 정착단은 조정이 불가능한 개방소켓으로 되어 있어 설계시 각 케이블의 길이 계산이 잘못될 경우에는 케이블이 구조부재로써 소정의 성능을 유지하기 위해 필요한 인장응력의 도입이 불가능하게 된다. 그러나, 구조물의 인양이 완료된 상태에서 계측된 각 케이블의 장력에 의하면 평균 $4\%$정도의 정확도를 보이고 있어 설계뿐만 아니라 지붕구조와 관련된 모든 공정의 시공이 치밀하게 이루어 졌음을 보여 주고 있다.

  • PDF

틸트 로터 항공기의 지면 효과 분석 (Ground Effect Analysis of Tilt-Rotor Aircraft)

  • 김철완;장병희;이장연
    • 유체기계공업학회:학술대회논문집
    • /
    • 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
    • /
    • pp.427-430
    • /
    • 2006
  • The ground effect on tilt-rotor UAV is analyzed by simulating the hovering UAV for various altitudes. Ground effect increases pressure beneath the UAV body and generates additional lifting force. The ground effect diminishes at altitude 3m and hovering UAV generates constant lifting force above 3m.

  • PDF

힙업기능이 적용된 기립보조의자의 생체역학적 평가 (Biomechanical Assessment of Lifting Chair with Hip-up Function)

  • 배주환;문인혁
    • 대한의용생체공학회:의공학회지
    • /
    • 제32권3호
    • /
    • pp.191-197
    • /
    • 2011
  • Lifting chair is a typical assistive product to aid for standing up and sitting down for persons with disability. It is particularly useful for the elderly persons whose muscular system is weakened by degenerative joint disease. This paper describes biomechanical assessments of lifting chair with hip-up function. In experiments we measured 3D motion and electromyographic(EMG) signal on the femoral muscle when subject performs the standing motion on the predetermined seat height. Based on assessment of the standing motion, we select the hip-up angle as 15 degrees to cover the relative femoral angle when EMG peak value is appeared. Using an implemented prototype lifting chair with hip-up function we perform standing experiments with five subjects. The experimental results show that the lifting and hip-up functions are effective to assist for standing up motion with less muscle force.