• Smart Structures and Systems
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• v.6 no.9
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• pp.1041-1056
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• 2010

This paper investigates the possibility of a strategy for an automatic full recover of a structural component undergoing loading-unloading (fatigue) cycles: full recover means here that no replacement is required at the end of the mission. The goal is to obtain a material capable of self healing earlier before the damage becomes irreversible. Attention is focused on metallic materials, and in particular on shape memory alloys, for which the recovering policy just relies on thermal treatments. The results of several fatigue tests are first reported to acquire a deep understanding of the physical process. Then, for cycles of constant amplitude, the self-healing objective is achieved by mounting, on the structural component of interest, a suitable microcontroller. Its input, from suitable sensors, covers the current stress and strain in the alloy. The microcontroller elaborates from the input the value of a decisional parameter and activates the thermal process when a threshold is overcome.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.382-387
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• 2003

In this study, to achieve the optimal conditions for mechanical hyper-fine pattern fabrication process, deformation behaviors of the materials during indentation were studied with numerical method by ABAQUS S/W. Brittle materials (Si, Pyrex glass 7740) were used as specimens, and forming conditions to reduce the elastic recovery and pile-up were proposed. The indenter was modeled a rigid surface. Minimum mesh sizes of specimens are 1-10nm. Comparisons between the experimental data and numerical result demonstrated that the finite element approach is capable of reproducing the loading-unloading behavior of a nanoindentation test.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2001.11a
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• pp.118-123
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• 2001

The objectives of this research are to verify the structural stability and estimate the resisting performance of Stressed-Arch system during the construction process. Full scale models are taken to obtain the objective shape by the Dynamic Relaxation Method. As a result, it measured more strain than yielding strain at the extreme fiber of top chord member on the crown, but it is shown that members have the sufficiently compressive resisting performance as well as a considerable strain recovery capacity under unloading. Therefore, it is confirmed that Stressed-Arch system apparently have sufficient range of the structural capacity, but it is required that the elasto-plastic behavior of this system must be verified more detailed by numerical analysis and experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.64-73
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• 2005

This paper is concerned with the simulation-based parameter determination for the tool design in the stamping process of the complicated auto-body member. The CAE procedure of the stamping process is proposed so that troubles such as wrinkle, springback and excess metal be eliminated with changing parameters such as the blank size, the restraining force of the draw-bead and the embossing shape in the die face. The selected indicators of failure during forming are wrinkling. the amount of spring after unloading of the tool, the amount of excess metal developed .The proposed analysis scheme is applied to the tool and process parameter design for the front side member of a RV car. The simulation results show that the scheme can produce sound product from the viewpoint of thickness distribution, the contact condition between tools and the blank, the shape accuracy and so on.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.51-58
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• 2015

In this study, we developed an automated non-contact thickness measurement machine that continuously and precisely measures the thickness and warp of a PCB product using a laser sensor. The system contains a measurement part to measure the thickness in real time automatically according to the set conditions with an alignment supply unit and unloading unit to separate OK and NG products. The measurement machine was utilized to evaluate the performance at each step to minimize measurement error. At the zero setting for the initial setup, the standard deviation of the 216 samples was determined to be $5.52{\mu}m$. A measurement error of 0.5mm and 1.0mm as a standard sample in the measurement accuracy assessment was found to be 2.48% and 2.28%, respectively. In the factory acceptance test, the standard deviation of 1.461mm PCB was measured as $28.99{\mu}m$, with a $C_{pk}$ of 1.2. The automatic thickness measurement machine developed in this study can contribute to productivity and quality improvement in the mass production process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.94-97
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• 1999

The study has been performed for the relation between die and product in closed die upsetting by the experiment. the strain of die has been given by the simple experiment using the strain gauge located at the outer surface of die and the deformation history of die and product has been given by the experiment and Lame's formula. the product with accurate dimension and shape can be obtained by analysing elastic deformation of die during upsetting process. The deformation of die during metal forming process has been given by the experiment and lame's formula. The product with accurate dimension and shape can be obtained by analysing elastic deformation of die during upsetting process. The deformation of die during metal forming process has been usually predicted by the experience of industrial engineers of finite element analysis. But it is difficult to predict the dimension of product at unloading and ejected states. The study has given useful result for the deformation history of die and product through the experiment and Lame's formula at closed die upsetting and can be applied in the die design for product with accurate dimension.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.3
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• pp.349-356
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• 2022

Nuclear power plant decommissioning generates significant concrete waste, which is slightly contaminated, and expected to be classified as clearance concrete waste. Clearance concrete waste is generally crushed into rubble at the site or a satellite treatment facility for practical disposal purposes. During the process, workers are exposed to radiation from the nuclides in concrete waste. The treatment processes consist of concrete cutting/crushing, transportation, and loading/unloading. Workers' radiation exposure during the process was systematically studied. A shielding package comprising a cylindrical and hexahedron structure was considered to reduce workers' radiation exposure, and improved the treatment process's efficiency. The shielding package's effect on workers' radiation exposure during the cutting and crushing process was also studied. The calculated annual radiation exposure of concrete treatment workers was below 1 mSv, which is the annual radiation exposure limit for members of the public. It was also found that workers involved in cutting and crushing were exposed the most.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1913-1924
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• 2024

This paper presents the design and operation of an autonomous robot for pyroprocess automation, which requires unique approaches beyond those used in industrial applications to achieve the desired performance. Maintaining an extremely dry atmosphere is crucial to handle various materials, including chloride, and an autonomous system ensures this dry environment. The drying room dehumidifier was carefully selected and designed to generate dry air, and different types of dry air conditioning performance were evaluated, including assessing worker accessibility inside the mock-up to determine the system's feasibility. Containers used for process materials were modified to fit the gripper system of the gantry robot for automation. The loading and unloading of process materials in each equipment were automatically performed to connect the process equipment with the robotic system. The gantry robot primarily operated through macro motion to approach waypoints containing process materials, eliminating the need for precise approach motion. The robot's tapered jaw design allowed it to grasp the target object even with imperfect positioning. Robot motions were programmed using a robot simulator for initial positioning and motion planning, and real accuracy was tested in a mock-up facility using the OPC platform.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1055-1058
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• 2005

In the ACPF(Advanced spent nuclear fuel Conditioning Process Facility), the spent fuel pellets which are highly radioactive materials are separated with its clad and are fed into the next conditioning process. For this, at the other facility called PIEF(Post Irradiation Examination Facility) a spent fuel rod, 3.5 m long, is cut by 25 cm long which is suitable length fur the decladding process. These rod-cuts are packed into the capsule and are moved to the ACPF. Once the capsule is unloaded in the ACPF, the rod-cut is taken out one-by-one from the capsule and installed on the decladding device. In these processes, the crushed spent fuel pellet can be scattered inside the facilities and thus it contaminate the hot cell. In this paper, we developed the specially designed capsule which prevents the pellets scattering and remarkably reduces the leading and unloading time of the rod-cuts.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.238-247
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• 2023

The present work represents a technical guideline for decommissioning a disused teletherapy machine model Theratron-780 and contains category one ⁶⁰Co radioactive source. The first section predicts the dose rate from the source in case of normal and radiological emergency situations via FLUKA-MC simulation code. Moreover, the dose assessment for the occupational during the whole process is calculated and compared to the measured values. A suggested cordoned area for safety and security in a radiological emergency is simulated. The second section lists the whole process's technical procedures, including (preview, dismantle, securing, transport and storage) of the disused teletherapy machine. Results show that the maximum obtained accumulated dose for occupational were found to be 24.5 ± 4.9 μSv in the dismantle and securing process in addition to 3.5 ± 1.8 μSv during loading on the transport vehicle and unloading at the storage facility. It was found that the measured accumulated dose for workers is in good agreement with the estimated one by uncertainty not exceeding 5% in normal operating conditions.