• Title/Summary/Keyword: Piping vibration

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Determination of Peening Area for Finite Element Residual Stress Analysis of Ultrasonic Nanocrystal Surface Modification under Multiple Impact Conditions (초음파나노표면개질 다중충격 조건에서의 잔류응력 예측을 위한 유한요소 피닝해석 영역 결정)

  • Tae-Hyeon Seok;Seung-Hyun Park;Nam-Su Huh
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.17 no.2
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    • pp.145-156
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    • 2021
  • Ultrasonic Nanocrystal Surface Modification (UNSM) is a peening technology that generates elastic-plastic deformation on the material surface to which a static load of a air compressor and a dynamic load of ultrasonic vibration energy are applied by striking the material surface with a strike pin. In the UNSM-treated material, the structure of the surface layer is modified into a nano-crystal structure and compressive residual stress occurs. When UNSM is applied to welds in a reactor coolant system where PWSCC can occur, it has the effect of relieving tensile residual stress in the weld and thus suppressing crack initiation and propagation. In order to quantitatively evaluate the compressive residual stress generated by UNSM, many finite element studies have been conducted. In existing studies, single-path UNSM or UNSM in a limited area has been simulated due to excessive computing time and analysis convergence problems. However, it is difficult to accurately calculate the compressive residual stress generated by the actual UNSM under these limited conditions. Therefore, in this study, a minimum finite element peening analysis area that can reliably calculate the compressive residual stress is proposed. To confirm the validity of the proposed analysis area, the compressive residual stress obtained from the experiment are compared with finite element analysis results.

Seismic response analysis of buried oil and gas pipelines-soil coupled system under longitudinal multi-point excitation

  • Jianbo Dai;Zewen Zhao;Jing Ma;Zhaocheng Wang;Xiangxiang Ma
    • Earthquakes and Structures
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    • v.26 no.3
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    • pp.239-249
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    • 2024
  • A new layered shear continuum model box was developed to address the dynamic response issues of buried oil and gas pipelines under multi-point excitation. Vibration table tests were conducted to investigate the seismic response of buried pipelines and the surrounding soil under longitudinal multi-point excitation. A nonlinear model of the pipeline-soil interaction was established using ABAQUS finite element software for simulation and analysis. The seismic response characteristics of the pipeline and soil under longitudinal multi-point excitation were clarified through vibration table tests and simulation. The results showed good consistency between the simulation and tests. The acceleration of the soil and pipeline exhibited amplification effects at loading levels of 0.1 g and 0.2 g, which significantly reduced at loading levels of 0.4 g and 0.62 g. The peak acceleration increased with increasing loading levels, and the peak frequency was in the low-frequency range of 0 Hz to 10 Hz. The amplitude in the frequency range of 10 Hz to 50 Hz showed a significant decreasing trend. The displacement peak curve of the soil increased with the loading level, and the nonlinearity of the soil resulted in a slower growth rate of displacement. The strain curve of the pipeline exhibited a parabolic shape, with the strain in the middle of the pipeline about 3 to 3.5 times larger than that on both sides. This study provides an effective theoretical basis and test basis for improving the seismic resistance of buried oil and gas pipelines.

A Study on the Plastic deformation Absorption Characteristics of Aluminum-Polyethylene Composite Structure Sprinkler Pipe (알루미늄 합성수지 복합 구조 스프링클러 파이프의 변위 흡수 특성 연구)

  • Kim, Jun-Gon;Kim, Kwang-Beom;Noh, Sung-Yeo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.1
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    • pp.426-433
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    • 2019
  • After an earthquake, fire and gas explosions are more likely to cause more casualties in cities with many apartment buildings and large complex buildings. In order to prevent this, seismic design is necessary for the fire protection sprinkler system. However, most systems currently use stainless-steel pipes, although synthetic resin pipes are used in some special places. These materials are susceptible to vibration and earthquakes. This study evaluated the displacement absorption flexibility of polyethylene (PE) and aluminum (Al) multi-layered composite pipes to increase the seismic performance in a vibration environment and during earthquakes. The seismic performance was compared with that of a stainless-steel and PE pipes. The seismic characteristics can be measured by measuring the amount and extent of vibration transmitted by the sprinkler pipe. This method can be used to judge the seismic characteristics to attenuate the vibration during an earthquake. The seismic characteristics of the pipe were verified by comparing the logarithmic attenuation rate to the initial response displacement of the vibration generated by the transverse vibration measurement method.

A Study on the Performance Evaluation of Heat Treatment Furnace Design for Copper Tube Bending (동관 벤딩을 위한 열처리로 설계 및 성능평가에 관한 연구)

  • Park, Dae-kwang;Kim, Jae-yeol;Gao, Jia-Chen
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.1
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    • pp.136-144
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    • 2016
  • The air-conditioning industry is closely related to types of lifestyles, climate, and products. With the improvement of national income, the pursuit of pleasant living and working environments, and South Korea's four seasons and distinct climatic conditions, demand for air conditioning has increased. In addition, the industry is becoming increasingly precise and cooperative, and the increase in the domestic production of sophisticated air conditioning and continued growth of future industrial cooperation are expected to rapidly rise. Accordingly, the study of air piping systems can improve the productivity and quality of products and cost savings and can achieve vibration reduction. Additionally, using a heat treatment furnace for copper tube annealing treatment reduces the risk of using an oxy-acetylene torch.

Dynamic Analysis and Design of Uncertain Systems Against Random Excitation Using probabilistic Method

  • Moon, Byung-Young;Kang, Beom-Soo;Park, Jung-Hyen
    • Journal of Mechanical Science and Technology
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    • v.16 no.10
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    • pp.1229-1238
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    • 2002
  • In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.

Structural Integrity of a Fuel Assembly for the Secondary Side Pipe Breaks (2차측 배관파단에 대한 핵연료 집합체의 구조 건전성)

  • Jhung, M. J.
    • Journal of KSNVE
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    • v.6 no.6
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    • pp.827-834
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    • 1996
  • The effect of pipe breaks in the secondary side is investigated as a part of the fuel assembly qualification program. Using the detailed dynamic analysis of a reactor core, peak responses for the motions induced from pipe breaks are obtained for a detailed core model. The secondary side pipe breaks such as main steam line and economizer feedwater line braksare considered because leak-before-break methodology has provided a technical basis for the elimination of double ended guillotine breaks of all high energy piping systems with a diameter of 10 inches or over in the primary side from the design basis. The dynamic responses such as fuel assembly shear force, bending moment, axial force and displacement, and spacer grid impact loads are carefully investigated. Also, the stress analysis is performed and the effect of the secondary side pipe breaks on the fuel assembly structural integrity under the faulted condition is addressed.

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Cavitation optimization of single-orifice plate using CFD method and neighborhood cultivation genetic algorithm

  • Zhang, Yu;Lai, Jiang;He, Chao;Yang, Shihao
    • Nuclear Engineering and Technology
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    • v.54 no.5
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    • pp.1835-1844
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    • 2022
  • Single-orifice plate is wildly utilized in the piping system of the nuclear power plant to throttle and depressurize the fluid of the pipeline. The cavitation induced by the single-orifice plate may cause some serious vibration of the pipeline. This study aims to find the optimal designs of the single-orifice plates that may have weak cavitation possibilities. For this purpose, a new single-orifice plate with a convergent-flat-divergent hole was modeled, a multi-objective optimization method was proposed to optimize the shape of a single-orifice plate, while computational fluid dynamics method was adopted to obtain the fluid physical quantities. The reciprocal cavitation number and the developmental integral were treated as cavitation indexes (e.g., objectives for the optimization algorithm). Two non-dominant designs ultimately achieved illustrated obvious reduction in the cavitation indexes at a Reynolds number Re = 1 ×105 defined based on fluid velocity. Besides, the sensitivity analysis and temperature effects were also performed. The results indicated that the convergent angle of the single-orifice plate dominants the cavitation behavior globally. The optimal designs of single-orifice plates result in lower downstream jet areas and lower upstream pressure. For a constant Reynolds number, the higher temperature of liquid water, the easier it is to undergo cavitation. Whereas there is a diametric phenomenon for a constant fluid velocity. Moreover, the regression models were carried out to establish the mathematical relation between temperature and cavitation indexes.

A Study on Flow Characteristic due to the Periodic Velocity Fluctuation of Upstream at Single Tube (단일 원관에서 전방류의 주기적인 속도 변동에 따른 유동 특성에 관한 연구)

  • Ha, Ji-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.613-618
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    • 2019
  • The flow-induced vibration in a heat exchanger may cause the damage to piping. Therefore, it is necessary to establish the flow induced vibration characteristics for the structural stability of a heat exchanger. The purpose of this study was to compare the generation, development, and separation characteristics of a vortex around a circular tube with respect to time when the flow velocity of the inlet was fluctuating constantly and periodically. The time characteristics of lift and drag and the PSD characteristics were also investigated. In the case of a constant inlet flow velocity, the well-known Kalman vorticity distribution was shown. The vortex generation, growth, and separation were also observed alternately at the upper and lower sides of the tube. In the case of periodic inlet flow velocity, the vortex occurred simultaneously in the upper and lower sides of the tube. In the case of constant inlet flow velocity, the magnitude of the lift PSD was 500 times larger than that of drag. The frequency was 31.15 Hz and that of drag was doubled at 62.3 Hz. In case of a periodic inlet flow velocity, the PSD of the drag was approximately 500 times larger than that of lift. The frequency was 15.57 Hz, which was the same as the inlet-flow velocity frequency. In addition, the frequency of lift was 31.15 Hz, which was the same Karman vortex frequency.

Performance Analysis of Friction Damper Considering the Change of the Vertical Force (수직력의 변화를 고려한 마찰댐퍼의 거동 분석)

  • Cho, Sung Gook;Park, Woong Ki;Yi, Seong-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.1
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    • pp.59-66
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    • 2017
  • In this paper, to protect the piping in nuclear power plants and various plant facilities, we have developed a damper using the friction method and carried out a study to analyze the performance. Friction typed damper means a device for attenuating vibration by generating a frictional force to the bearing and the shaft by applying a compressive force to the MER-Spring. In order to analyze the performance of the damper, the properties of MER-Spring and friction materials were analyzed, a study on the effects of friction was carried out, and the behavior of this equation was established. And, to determine whether deformation of the material and to examine the reliability of the behavior equation established, prototypes was produced and, through a performance test and finite element analysis of a damper made of specimens, they were analyzed. As a result, it is noted that the reliability of the material was confirmed, the coefficient of friction have to be adjusted according to the velocity, cyclic loading test and finite element analysis results show exhibits excellent results. In addition, a review of the dynamic loads in the future shall be performed for the usage in more broad fields.

Structural Integrity Evaluation of Large Main Steam Piping by Water Hammering (수격 현상에 근거한 대형 주증기관의 구조건전성 평가)

  • Jo, Jong-Hyun;Lee, Young-Shin;Kim, Yeon-Whan;Jin, Hai Lan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.9
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    • pp.1103-1108
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    • 2012
  • A main steam pipe system is a branch pipe that connects a boiler with a turbine. Water hammering analysis is very important for limiting the damage caused to pipe systems by operation conditions. Water hammering created by an unsteady flow in pipeline systems can cause excessive change in pressure, vibration, and noise. The main steam pipe structure should be designed to safely maintain the pressure pulsation and several vibrations under operation environments. This study evaluated the structural integrity of a main steam pipe during suspended and normal operation by using the ASME fatigue life methodology and finite element analysis. In the analysis, water hammering was used for transient analysis. The calculated alternating stress and fatigue stress were compared with the applicable limits of ASME fatigue life. All the evaluation results satisfied the requirements of the ASME fatigue life.