Papers by Keyword: Accelerated Life Test (ALT)

Abstract: This paper proposed a new life test method of pneumatic cylinders used in pneumatic system, whose loads consist of working pressure, piston velocity, and working temperature. It is expected to reduce accelerated life test time greatly in case of accelerated life test with creating combined accelerated model of these three factors. We can determine the maximum accelerated factor by calculating the combined accelerated factor of working pressure, piston velocity and working temperature for various cases.

Abstract: The safety factor of hydraulic piston pumps and motors shows a tendency to decrease due to high pressurization, high speed and low weight/volume realization to enhance the output density. Therefore, more effective test models are necessary to predict the exact life. The sensitive parameters in the endurance life test are speed, pressure and temperature, and failure production increases in proportion to the operating time. In this research, the authors propose a combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by simultaneously applying high speed, high pressure and high temperature in accordance with the variation in speed, pressure and temperature in order to reduce the life test time.

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: Life testing is an important technique to assess the reliability and lifetime of components with long life and high reliability. To some expensive products, it is difficult to supply a large of samples and long test time to carry out the life testing, so this paper investigates the accelerated model and presents statistical method based on hybrid Weibull distribution under variable synthetic stresses. Based on the cumulative exposure theory, the failure probability can be cumulated with transform rate that can convert the fault proportion at certain stress into another stress. Using the genetic algorithm, the parameters of accelerated model can be estimated according to the accelerated stress profile. Then the lifetime at normal stress can be calculated with accelerated life model under normal stress profile. Application of hydraulic pump indicates that this method can reduce test time and test samples greatly.

Abstract: The hinge, which is used in various folders of electronic communication devices, damages easily due to the repeated impact-like stress that occurs when the folder is opened. The hinge damage not only affects the lifetime of devices, but it may cause to lose the reputation of the brand name of the company. In this paper, the total process for the life evaluation and failure analysis of this part is proposed. For this, the mechanism of the hinge motion was analyzed first to calculate the force acting on the hinge. Also an automatic durability test system was developed to repeatedly open and shut the folder. Then the change in deformation around the hinge was monitored using an Electronic Speckle Pattern Interferometer (ESPI) method, as the repetition number increased for the opening of the folder. ESPI results showed that the deformation was concentrated at the hinge and it increased according to the increase of repetition number of folder opening. Finally, we evaluated the life of the hinge through an accelerated life test (ALT). ALT results showed that the life of hinge was dependent on the force acting on the hinge