Hydraulic servo actuator is used as the core actuator in tensile compression fatigue life test equipment as it operates the micro displacement very precisely at a high frequency and can be used continuously for a long period of time. Recently, the life expectancy of automobiles has been extended, the load conditions of accelerated life testing on auto parts have been increased, and the life test time and number of tests have increased significantly in order to secure the reliability of the guaranteed life of produced vehicles. Therefore, hydraulic servo actuators mounted on accelerated life testing equipment for automotive parts are essential for much higher performance and a longer life than those tested. However, small- and medium-sized companies that supply test equipment for the fatigue life of auto often fail to develop technology due to a lack of research personnel and the development budget compared to the capabilities of large automobile manufacturers, resulting in frequent breakdowns due to the technical overload of test equipment. In this study, servo actuators were used to test automotive parts, with a maximum output of 2 ton, a maximum frequency of 3.3 Hz and a maximum displacement of 50 mm. The hydraulic servo actuator, which was installed in the tensile compression fatigue life test equipment, failed to operate normally at the site, and by analyzing it, we realized this resulted from the heat generation of insulation compression due to the accumulation of air and gas into the hydraulic oil and the increase in friction due to the deterioration of flow. A static pressure bearing was adopted as a design change to improve the root cause for this failure mode, and a very high level of geometric concentricity was secured by inserting concentric tubes outside the labyrinth seal type piston. The newly designed and manufactured actuator is the result of research that has achieved a semi-permanent long life and improved performance up to 100 Hz by non-contact operation.

Hydraulic excavator is one of the most commonly used construction equipments. In addition, the demand of large excavator has been increased. PTO gearbox, installed between engine and pumps, is used to improve fuel efficiency of large excavator. Because the PTO gearbox is loaded by the pump mounted on the output shaft, the torque distribution technique should be applied when controlling the load with the dynamometer. This paper introduces a torque distribution technique and conducts a comparative analysis of the torque test results and dynamic analysis.

The power take‐off (PTO) gearbox is widely used for special vehicles, large construction machinery, industrial machinery and ships, to distribute the power of a single input shaft from an engine or a motor to several shafts or to collect several shafts by single shaft power (Torque × rotation speed). The super large hydraulic excavator is equipped with a power take‐off (PTO) gearbox between the main engine and a number of pumps for the purpose of improving the fuel efficiency and improving the system efficiency. The power take‐off (PTO) gearbox of a large hydraulic excavator with a body weight of 100 ton ( = 10⁵ kg) is connected with two large hydraulic pumps and one small hydraulic pump on three output shafts and different axial loads are generated depending on the working characteristics of the excavator. In this paper, we evaluated the performance and durability of a power take‐off (PTO) gearbox of a large hydraulic excavator with a 100‐ton body weight. The test evaluation criteria for non‐fault life time calculation, performance and accelerated life test were established, and the types and characteristics of acceleration test equipment were analyzed. The torque distribution with the use of the gear phase difference to maintain the gearbox output condition was investigated, and energy was saved by circulating experimental power while controlling speed and load with two electric dynamometers. We analyzed the life of the gearbox by analyzing the metal particles generated in the lubricating oil of the gearbox.

A PTO gearbox ("gearbox") is designed to be mounted on a construction vehicle to convey power from the engine to multiple pumps. The gearbox uses oil bath lubrication, which often experiences a disruption in the supply oflubricant inside the gearbox. Poor lubrication in any gearing system is a major cause of a drop in its efficiency, which is often displayed in the form of heat or noise. This study describes a technology that can reduce noise by making splash lubricant inside the gearbox fall down along the wall like a curtain and measures its performance through comparison. Measurement of noise was made under no-load condition and load condition. For the former, measurement was made while the servo motor was used for driving to minimize noise from the equipment. For the load test, the noise from the equipment was unavoidable because an electrical dynamometer had to be used to control the load, but a comparison was made against the measured noise to determine where there had been any impact. If any impact was identified, a correction would be applied for the noise measured.

원자력/화력발전소의 터빈 스팀 제어장치는 스팀을 공급 또는 차단하는 단동 유압실린더, 대형 스프링 및 포핏 밸브로 구성된다. 발전소의 고압 및 저압 터빈은 단동 유압실린더에 의해 열리고 큰 스프링에 의해 폐쇄되는 포핏 유형의 특수 밸브에 의해 제어된다. 포핏 밸브의 신속한 폐쇄는 발전소의 비상 정지를 고려하여 정기적으로 수행되며, 단동 유압실린더의 끝에 유압 쿠션이 설치되어 큰 관성으로 인한 충격을 제거한다. 본 연구에서는 원자력/화력발전소의 증기 공급 밸브를 개방하는 단동 유압실린더에 대해 시스템 관성 및 스프링 력을 분석하고, 유압 쿠션 최적화를 위해 M&S 분석 및 시제품을 제작하여 해석 결과 및 실험 결과를 비교 분석하였다.