Bo-Sik Kang

Study on the Measurement Method of Leakage Flow-rate for Pneumatic Driving Apparatus

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there was no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measured by the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing steel wool into it. Therefore, wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic apparatus. The effectiveness of the proposed method is proved by experimental results

Development of the Accelerated Life Test Method & Life Test Equipment for the Counterweight of the Construction Machinery

A large-sized exciter that vibrates a two-ton component is required to simulate the field operating conditions of a counterweight of an excavator. However, it is difficult for a small-medium sized company to obtain a large exciter for the life test of a counterweight which is an equivalent counterbalancing weight that balances a load. Therefore, in this study, we developed life test equipment for evaluating the reliability of construction machinery weighing about two tons. It simulates the field operating conditions using rotational vibrators consisting of electric motors. A failure analysis of the counterweight was also performed for the major components. Field data acquired from various sites were applied to the life test design of the counterweight. Finally, a zero-failure qualification test based on the accelerated life test was designed, and there was no failure during the test, which guarantees a life of 10,000 hours.

Life and Performance Degradation Characteristics for Small-Sized Plug-In Type Pneumatic Manifold Valves

Pneumatic valves are widely used parts that have the ability to control the air supplied to automation systems. However, if failure occurs in a pneumatic valve, it may affect the entire system and could lead to huge losses, depending on the characteristics of the system at the time of failure. Because of this significant risk and the level of consumer demand for reliability, there has been much study on ensuring the reliability of products by predicting valve lifetime distributions and degradation characteristics. In this paper, in order to determine the main factors useful for predicting the lifetime of a pneumatic valve, the scale parameter and life time value of the widely used plug-in-type pneumatic manifold valves were measured using complete observational data on the valve lifetimes. And also the property of life distribution has been distribution-suitabilityreviewed by correlation coefficients, the degradation characteristics of valve has been presented by the result of analysis through dynamic response time test and leakage test.

A Study of the Assurance Life Prediction Method for Latch Spring of Vehicle Door Using the Modification of Shape Parameter

This study was performed to develop the assurance life prediction method using modification of shape parameter for the latch spring of vehicle door. The shape parameter β is a main parameter with scale parameter, number of sample, confidence level, in determining the predicted assurance life and testing time. The proposed the modification of shape parameter is an approach to verify the life prediction procedures based on the life testing data and to improve the reliability assessment on the statistical distribution. The latch spring generally represent fatigue and fracture characteristics as a failure mode. Firstly, life distribution of latch spring was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (B5 ) 300,000 cycles and 95% confidence level for 60 test samples with value of shape parameter 2.07 from reference data. Secondly, after the life test, the value of shape parameter 2.26 can be obtained by using MINITAB. Finally, the assurance life of latch spring could be predicted by the relation of mean life and the scale parameter which is achieved also from the analysis of sample failure data.Copyright