A study on the stress and strain during welding of plate-to-pipe joint

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthals equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe

A study on the stress and strain due to welding of web-pipe joint structure

학위논문(석사) - 한국과학기술원 : 생산공학과, 1986.2, [ iv, 53 p. ]한국과학기술원 : 생산공학과

더미패널을 이용한 인공위성 시스템 통합 절차 개선

학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2024.2,[v, 89 p. :]This thesis proposes a new methodology for the innovative improvement of satellite system integration procedures. To overcome the limitations of traditional sequential procedures, a novel integration process utilizing dummy panels has been developed. This innovative approach, grounded in practical project experience, has been successfully applied in significant real-world projects, including the Geo-Kompsat 2 (GK2) and the Korea Pathfinder Lunar Orbiter (KPLO) development projects. This practical success demonstrates the potential for revolutionizing conventional methodologies in the field of satellite system integration, marking an important milestone for future advancements in this area. The dummy-panel process represents a significant departure from the traditional Flight Model (FM-panel) process, showcasing a new direction in satellite system integration and testing. The study’s centerpiece is a comprehensive analysis of the dummy-panel process, employing Design Structure Matrix (DSM) based modeling and simulation techniques. In developing the simulation model, extensive research was conducted into various project facets. This research included detailed evaluations of task dependencies, duration and cost estimates, the likelihood of rework, and the repercussions of such changes. Inputs for these simulations were derived from actual project data, ensuring both accuracy and relevance. Subsequent discrete event simulations, powered by a custom-developed algorithm, meticulously replicated the project execution process. This algorithm accurately simulates a range of scenarios, including sequential, parallel, and overlapping tasks, along with both feedback and feedforward rework processes, thus offering a holistic view of project dynamics. The results of the simulations and sensitivity analyses in this study act as practical case studies, yielding critical insights into the performance of each process, encompassing total duration and cost distributions. These analyses are pivotal in gauging schedule and cost risks and in understanding how variations in process architecture affect the project. Insights from these case studies are key in optimizing project schedules and formulating effective risk management strategies. They underscore the criticality of comprehending task interdependencies and their substantial impact on project outcomes. Moreover, these analyses highlight the crucial balance between cost and project duration, stressing the need for identifying and implementing optimal execution strategies. This research shows that despite the dummy-panel process typically requiring a somewhat higher cost, it can be a more preferred method in environments with low risk tolerance, due to its more predictable outcomes and effective risk management capabilities. By combining practical insights gained from important projects with the analytical depth of DSM-based simulation methods, a powerful framework for improving the satellite development process is provided. Future studies should aim to encompass a broader range of processes and investigate the dynamic nature of task dependencies that may change during the course of a project.한국과학기술원 :항공우주공학과