Papers by Author: Hyoung Eui Kim

Abstract: In this study, we proposed a process of an accelerated life testing method of 5-speed manual transmissions used in vehicles, which loads are consisted of multiple alternating loads. The entire process of an 5-speed manual transmission’s accelerated life testing method where no failures are allowed, is a process that requires an abundance of assumptions, and other factors that are estimates such as the shape parameter, beta(
) and the fatigue damage exponent (x). And the process is consisted of 7-step process. From the 1-setp, which is the deriving the service(use) torque and speed(rpm) profile of the transmission, to the 7-step, we could determine the accelerated life time, the accelerated torque and the accelerated speed(rpm), which are the equivalent cumulative fatigue damage. Also, we have performed accelerated life test on 5-speed manual transmission by using the following 7-step process.

Abstract: This paper proposes a new accelerated life test method of hydraulic pump used in vehicles, which have multiple alternating loads. For determination of life time of hydraulic pump for given field conditions with respect to duty cycle, the equivalent load and speed of this unit has to be determined. Equivalent load and speed can be calculated from the given duty cycle using the predominant theory for cumulative fatigue damage. Finally, we can perform accelerated life test on hydraulic pump by determination of test pressure and speed from calculated equivalent cumulative damage per working cycle and weighted average speed.

Abstract: A hydraulic breaker for construction machinery generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and so on. So the measurement of the impact energy of a hydraulic breaker is very important thing to prove its capability to manufacturers and customers. In this study, the test system for measuring the impact energy of a hydraulic breaker was designed and constructed. The test system was consisted with hydraulic cylinders for mounting a breaker, impact absorbing base and frames, pressure and flow sensors, high speed and accurate data acquisition system
 diesel engine driven hydraulic power unit. The test process of the developed system was carried by measuring guide for tool energy rating for hydraulic breakers which was developed by the CIMA (Construction Industry Manufacturers Association) USA. The developed test system can be applied to measure the impact energy for various kinds of hydraulic breakers.

Abstract: The paper discusses the problem of reliability calculation for mechanical units under load. Because the rated reliability of the unit as a system with many independent elements can tend to zero, the methods of reliability calculation of the units as real objects with the common factors (loads, operation conditions) are proposed. The choice of the life test modes and test time depends essentially on unit-related information like their operation conditions. The paper describes one of approaches, passing to this problem. Within its framework, the accumulations of damages are made at several typical points of the loaded system.

Abstract: There are several types of life test method for hose assemblies. The two major tests used for hose assemblies are impulse test and burst test. And magnification adjustment of impulse pressure, heating of testing oil and repetitive motions of bending and straightening of testing hose are also performed for accelerating the life. According to the manufacture process of hose and swaging process of fitting, there is a difference in the life of hose assemblies from minimum 7 times to maximum 40 times during the life test in the same functioning condition. Like this, the life test of hose which has a wide scope of life distribution gives a problem that observation should take a long time to find out the existence of the bursting from the beginning of the test to the completion of bursting of hose assemblies. Therefore, this research proposes a process of concentrating on the defective section of hose assemblies and maximizing the life acceleration by giving ‘Knockdown stress’ to hose assemblies just until before the hose assemblies get out of order.