• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.19 no.2
• /
• pp.117-129
• /
• 2023

Hydrogen embrittlement of a pipe is an important factor in hydrogen transport. To characterize hydrogen embrittlement, tensile and fracture toughness tests should be conducted. However, in the case of hydrogen-embrittled materials, it is difficult to perform tests in hydrogen environment, particularly at low temperatures. It would be useful to develop a methodology to predict the fracture toughness of hydrogen-embrittled materials at low temperatures using more efficient tests. In this study, the fracture toughness of API X52 steels in hydrogen at low temperatures is predicted from numerical simulation using coupled finite element (FE) damage analyses with FE diffusion analysis, calibrated by analyzing small punch test data.

• Journal of the Korea Society for Simulation
• /
• v.18 no.3
• /
• pp.1-11
• /
• 2009

This paper illustrates a case study of PLC logic simulation in a car manufacturing system. It was developed to simulate and verify PLC control program for automobile panel AS/RS. Because car models become varied, the complexity of supply problem is increasing in the car manufacturing system. To cope with this problem, companies use the AS (automated storage) and RS (retrieval system) but it has logical complexity. Industrial automated process uses PLC code to control the AS/RS, however control information and control codes (PLC code) are difficult to understand. This paper suggests a PLC simulation environment, using 3D models and PLC code with realistic data. Data used in this simulation is based on realistic 3D model and I/O model, using actual size and PLC signals, respectively. The environment is similar to a real factory; users can verify and test the PLC code using this simulation before the implementation of AS/RS. Proposed simulation environment can be used for test run of AS/RS to reduce implementation time and cost.

• Journal of Power Electronics
• /
• v.18 no.4
• /
• pp.1111-1126
• /
• 2018

In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.

• Wind and Structures
• /
• v.28 no.5
• /
• pp.271-284
• /
• 2019

This paper describes the application of a novel virtual prototyping methodology to wind turbine blade design. Numeric modelling data and experimental data about turbine blade geometry and structural/dynamical behaviour are combined to obtain an affordable digital twin model useful in reducing the undesirable uncertainties during the entire turbine lifecycle. Moreover, this model can be used to track and predict blade structural changes, due for example to structural damage, and to assess its remaining life. A new interactive and recursive process is proposed. It includes CAD geometry generation and finite element analyses, combined with experimental data gathered from the structural testing of a new generation wind turbine blade. The goal of the research is to show how the unique features of a complex wind turbine blade are considered in the virtual model updating process, fully exploiting the computational capabilities available to the designer in modern engineering. A composite Sandia National Laboratories Blade System Design Study (BSDS) turbine blade is used to exemplify the proposed process. Static, modal and fatigue experimental testing are conducted at Clarkson University Blade Test Facility. A digital model was created and updated to conform to all the information available from experimental testing. When an updated virtual digital model is available the performance of the blade during operation can be assessed with higher confidence.

• Journal of Mechanical Science and Technology
• /
• v.20 no.12
• /
• pp.2159-2167
• /
• 2006

In order to find out a physical quantity which controls the fatigue life of a structure and to predict the fatigue life of tires, a finite element simulation methodology to use the cracking energy density (CED) and the virtual crack closure technique (VCCT) was proposed and applied to three different tires of a similar size. CED was calculated to predict the location of a crack initiation, and VCCT was used to obtain the strain energy release rate (SERR) at the tip of an initiated crack. Finite element simulations showed that SERR oscillated in the circumferential direction with its minimum occurring just before the contact zone and its maximum occurring just after the center of the contact zone, and SERR was affected significantly by the frictional force acting on the crack surface. In addition, a durability test was conducted to measure the fatigue life of the three tires. The comparison of SERR values with the test data revealed that the fatigue life increased as the amplitude of SERR decreased or as the R-ratio of SERR increased.

• Journal of Welding and Joining
• /
• v.33 no.3
• /
• pp.40-46
• /
• 2015

Welding is one of the most fundamental and necessary work in the industry that demand sophistication of skilled workers. This study is to introduce welding simulator as a training tool, to verify its effectiveness and to measure satisfaction of the trainees. A group of freshman students at a Korea Polytechnics College in their twenties with less experience of welding participated in the study. They were divided into two groups and took a traditional training course (comparison group) and a training course with welding simulator applied reality/haptic technology (experimental group) for same hours respectively. To evaluate training effect, a national certificate test and a survey based on Phillips' ROI (Return on Investment) methodology were conducted by the students and the college respectively. And satisfaction survey among the students based on Kirkpatrick's Four-Level Evaluation Model was also carried out. The results showed that all students in the experimental group passed the national certificate test and the ROI of the experimental group for five years were 110% higher than the comparison group. Furthermore, 25% more students in the experimental group replied "very satisfied" about the overall training course and 75% more students in the same group found that the simulation was very similar to the real welding.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.2
• /
• pp.185-194
• /
• 2016

It is essential for generating the synthetic image to test and evaluate a guided missile system in the hardware-in-the-loop simulation. In order to make the evaluation results to be more reliable, the extent of fidelity and rendering performance of the synthetic image cannot be left ignored. There are numerous challenges to simulate the LWIR sensor signature of sea surface depending on the incident angle, especially in the maritime environment. In this paper, we investigate the key factors in determining the apparent temperature of sea surface and propose the approximate formula consisting of optical characteristics of sea surface and sky radiance. We find that the greater the incident angle increases, the larger the reflectivity of sea surface, and the greater the water vapor concentration in atmosphere increases, the larger the amount of sky radiance. On the basis of this information, we generate the virtual maritime environment in LWIR region using the SE-WORKBENCH, physically based rendering software. The margin of error is under seven percentage points.

• The KIPS Transactions:PartA
• /
• v.14A no.4
• /
• pp.227-234
• /
• 2007

In the virtual prototyping environment, we can simulate details of a target model using many components and libraries provided in advance on a computer. The real prototyping environment provides the test simulation environment as a real product, but we can't do a detailed simulation of a real product in the virtual prototyping environment, and we can't do various simulations in the real prototyping environment. So, we made a integrated prototyping environment for linkage of the two types of prototyping environments. Also, in this paper, we developed the integrated prototyping environment based on objects. By this kind of embedded system development environment, we can have the advantages as reuse, flexibility, scalability, and more convenient of product making.

• Proceedings of KOSOMES biannual meeting
• /
• 2003.11a
• /
• pp.141-148
• /
• 2003

Yaw-checking and course-keeping ability in IMO's ship manoeuvrability standards is reviewed from the viewpoint cf sole navigation Three kinds of virtual series-ships, which have different course instability, are taken as test models. The numerical simulation on Z-test is carried out in order to examine the correlation between known manoeuvrability in spiral characteristics and various kinds of overshoot angle. Then simulator experiments are executed with series-ships in a curoed, narrow waterway by six operators(five active pilots and one ex-captain) in order to examine the correlation between known manoeuvrability and degree of manoeuvring difficulty. IMO criteria for yaw-checking and course-keeping ability are discussed and revised criteria are proposed.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.2
• /
• pp.37-43
• /
• 2005

A haptic steering system which reflects steering reaction torque has been developed for a fixed base vehicle simulator. The haptic steering system consists of a steering effort sensor, MR-clutch, AC servo motor and controller. In order to generate realistic steering torque feel to driver and at the same time to meet real-time simulation requirement, 3D torque map is constructed by experimental data and torque generation algorithm using the torque map has been also developed. 3D torque map is constructed using curve fitting and interpolation of the measured values of the steering angle, velocity and steering torque from actual slalom test on the proving ground. In order to carry out performance test of the developed haptic steering system, a fixed based vehicle simulator is constructed by integrating real time vehicle dynamics module, VR-video/audio module, and the haptic steering system. Steering torque and steering angle curves have been obtained from virtual testing in the vehicle simulator and performance of the haptic steering system has been evaluated.