Hyoung-Eui Kim

Practical Selection Criteria for Determination of Confidence Level in Substantiation Test

The purpose of reliability substantiation test is to verify the compatibility of reliability requirements for products or components. Historical data or engineering judgment on life distribution, reliability target value, sample size, confidence level, acceptance rule and etc. are essentially required to design and perform the substantiation test. In this paper, we would like to propose a determination method and its procedure for the confidence level by applying criteria of sample cost, test money, economical damage effect and safety

Barkhausen noise in ferromagnetic metallic glass Fe40Ni38Mo4B18

The influence of heat treatment on conventional magnetic properties and Barkhausen noise were studied in ferromagnetic amorphous Fe40Ni38Mo4B18 during a half magnetization cycle for both amorphous and crystallized states. The coercivity, Hc, was low in the amorphous specimens and maximum as the crystallization starts, and decreased with further annealing. The differential permeability near to the Hc, μc, was high in the amorphous specimens and minimum at the onset of crystallization, then increased with annealing. The single peak behavior of the Barkhausen noise (BN) envelope was a common feature in both amorphous and crystallized specimens, and the variation of peak height with heat treatment was similar to that of μc. The magnetic anisotropy energy constant, Ku, was lowest when the crystallite started to nucleate in the amorphous specimen, and increased as the crystallite size grows. The difference between ribbon and transverse directions of BN characteristics such as BN energy, peak height of BN envelo...

The retarding field model of Barkhausen noise and permeability in conventional and highly grain-oriented 3% Si-Fe polycrystals

Abstract The Barkhausen noise envelope, the permeability and the hysteresis curve in highly grain-oriented HiB-8, and in annealed and cold-worked conventional 3% Si-Fe were measured simultaneously in order to investigate the microstructural dependence of domain wall dynamics. The square and round hysteresis loops in the annealed and cold-worked specimen, respectively, are explained by the retarding field curve Hr(x). The Barkhausen signal and the permeability are represented by the sum of the fluctuating ΔHI,i and the instantaneous averaged net field 〈HI,i〉. The two peaks of the enve lope observed in the annealed conventional 3%Si-Fe and HiB-8 at the knees of B-H loop and the single peak in the cold-worked specimen at Hc are explained in terms of the distribution functions of the processes of domain nucleation f[ΔHI,i(nucl)], annihilation f[ΔHI,i(annih)] and wall displacement f[ΔHI,i(disp)]. T he frequency spectrum of the Barkhausen pulses was measured to investigate the nature of clustering and overlapping.

System Design and Performance Test of Hydraulic Intensifier

. 얻을 수 있었다. Abstract: Components such as pressure vessel, hydraulic hose assembly, accumulator, hydraulic cylinder, hydraulic valve, pipe, etc., are tested under the impulse-pressure conditions prescribed in ISO and SAE standards. The impulse pressure test machine needs to have a high pressure, a precise control system and a long life. It should satisfy the requirements for fabrication of the impulse tester to generate ultra high pressure in the hydraulic system. In the impulse tester, a servo-valve control system is adopted; although the control application is convenient, it is expensive owing to the cost of developing the system. The type of the control system determines the pressure wave, which affects the components that are tested. In this study, the manufacturing process and the intensifier system design related to the flow, pressure, and the increasing rate of pressure are investigated. The results indicate the ultra high pressure waves in the system.

Evaluation of Residual Stress and Texture in Ferromagnetic Crystalline Material by Barkhausen Noise Measurements

Abstract The Barkhausen noise (BN), induction rate, dB/dt, and hysteresis loop of 50% cold rolled polycrystal-line permalloy, annealed and tensile strained mild steel have been measured simultaneously. The peak of the BN amplitude distribution of the permalloy shifted toward lower amplitude and the total number of Barkhausen pulses decreased as the specimen cut angle respect to the rolling direction increased due to the increased number of impassable defects caused by the reduction in the driving force of domain wall. The two peaks in the rectified BN envelope of annealed mild steel specimen at the knee regions of hysteresis curve was accounted for the acceleration and deceleration of domain wall movement due to nucleation and annihilation of new reverse domain. As the residual strain increased from 6.7%, the BN envelope changed to the single peak at the coercive field due to the increased interactions with dislocations during irreversible wall displacement. The hysteresis loss and the BN energy in the co...

Life Prediction for High Pressure Hose of Power Steering System by Impulse Pressure Test

The hydraulic hose can be divided with the low pressure, the medium pressure, and the high pressure hose according to the applied pressure. The power steering system in a passenger car can be divided with the high pressure and the low pressure hose. This study deals with the life prediction for high pressure hose to be given impulse pressure which was generated in turning the car. To adjust with external and internal condition, impulse pressure and oil temperature need to be controlled with impulse test system. The result, which is only controlled with the pressure and oil temperature, adapted Calibrated Accelerated Life Test(CALT) method to predict the life of the high pressure hose and analyzed the swagging part by finite element method during the impulse test.

Lifetime Estimation of an Axle Drive Shaft by Calibrated Accelerated Life Test Method

In this paper, a method to predict the fatigue life of an axle drive shaft by the calibrated accelerated life test (CALT) method is proposed. The CALT method is very effective for predicting lifetimes, significantly reducing test time, and quantifying reliability. The fatigue test is performed by considering two high stress and one low stress levels, and the lifetime at the normal stress level is predicted by extrapolation. In addition, in this study, the major reliability parameters such as the lifetime, accelerated power index, shape parameter, and scale parameter are determined by conducting various experiments. The lifetime prediction of the axle drive shaft is verified by comparing the experimental results with load spectrum data. The results confirm that the CALT method is effective for lifetime prediction and requires a short test time.

The tracking control of uni-axial servo-hydraulic shaking table system using time delay control

In this paper, research results for improvement of tracking performance of servo-hydraulic shaking table are presented. Servo-hydraulic shaking table system is totally nonlinear due to the nonlinear flow property in a cylinder by actuation of servo valve. And it is demanded for the shaking table system to track arbitrary trajectories up to high frequency even at the extreme situations such as substantial external loads and large disturbances. For this purpose, time delay control (TDC), a robust control technique for highly nonlinear system, is applied to this system. TDC does not require any linearized model and any real time computation of nonlinear model. It is shown through numerical simulations that tracking performance of servo-hydraulic shaking table system is improved up to 30 Hz in real time by applying TDC

Study of the Accelerated Life Test Method for Power Train Components Under Cyclic Loads Using Weibull-IPL (Inverse Power Law) Model

This study was performed to develop the accelerated life test method using Weibull-IPL (Inverse Power Law) model for power train components that are running on cyclic loads. Weibull-IPL model is concerned with determining the assurance life with confidence level and the accelerated life test time. From the relation of weibull distribution factors and confidence limit, the testing times on the no or some number of failure acceptance criteria are determined. The power train components under cyclic loads generally represent wear and fatigue characteristics as a failure mode. IPL based on the cumulative damage theory is applied effectively the mechanical components to reduce the testing time and to achieve the accelerating test conditions. The proposed Weibull-IPL model is an approach to improve the reliability assessment on the statistical distribution and wear out failure mechanism concepts. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% confidence level for one test sample. According to IPL, because test time can be shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration factor was 11.7. This Weibull-IPL model can be used to develop accelerated test method of gear reducer, hydraulic hose, bearing and etc.Copyright

A Study of the Variation in Intensifier Performance Characteristics Varying with Pressure and Temperature

An ultra high- pressure system generally consists of a hydraulic power unit, an oil supply unit, an electrical power supply device, and an electrical control device. The hydraulic power unit supplies the hydraulic power to the intensifier to create generate ultra high pressure. The intensifier amplifies increases the pressure using the oil supplied from by the hydraulic power unit. The electrical supply devices and control devices maintain are provided for the electric motors, valves, and sensors. In this study, instead of a flow-control device, a pressure-control type device was mounted on a manifold block in the hydraulic power unit instead of the flow-control type. A servo valve was fitted in the intensifier, and the performance characteristics of the intensifier varied according to the variations of in the pressure cycle and with the temperature of the operating oil in the hydraulic power unit.