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RISS 인기검색어
- 검색키워드
- 저자 : Huan-Sheng (검색결과 39 건)
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Effects of defect size on failure of butt fusion welded MDPE pipe under tension
Huan Sheng Lai,길성희,윤기봉 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5
Since medium density polyethylene (MDPE) pipes are increasingly used in the gas industry, welding defects are becoming a safetyconcern. In this study, butt fusion welded MDPE pipe joints with spherical and planar defects of various sizes were studied by experimentaltensile tests and finite element analysis. These defects were considered for simulating lack of bonding during the welding. Thetensile test results showed that pipe strength was not reduced by defects that were up to 15% of the pipe’s thickness in size. On the otherhand, when the size of the defect was increased to 30% and 45% of the thickness, the failure strain decreased considerably. Finite elementanalysis verified that the effects of steel defects inserted intentionally before welding are comparable to those of air defects, whichare close to actual weld defect conditions. Hence, the experimental results obtained in this study can represent the actual situation. It isargued that a single welding defect with a maximum size smaller than 15% of the pipe’s thickness can be accepted without compromisingthe structural integrity of the pipe during short term of usage not considering long term creep or slow crack growth.
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Effect of defects on the burst failure of butt fusion welded polyethylene pipes
Huan Sheng Lai,Nwe Ni Tun,Seong Hee Kil,윤기봉 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.5
With the increasing demand of Medium density polyethylene (MDPE) pipes for gas transmission, the safety concern related with welding defects is becoming a serious matter. In this paper, experimental burst tests and finite element analyses were employed to study butt fusion welded MDPE pipe joints with spherical and planar defects of various sizes. These defects were used to simulate lack of bonding during the welding. Test results showed that in all pipe test cases, the failure location originated from pipe substrates, even though the defect size was increased to 45% of the pipe’s wall thickness. The burst pressure could be estimated by the expression employed in the ASME BPVC, and in the burst pressure, the hoop stress was 20.28 MPa. Simulation results showed that the failure position was not only affected by the defect size, but also by the welding bead. It can be argued that a single welding defect whose maximum size is smaller than 15% of the thickness can be used without failure during short-term usage, even when there is no welding bead in the welded joint.
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Blade number effect for a ducted wind turbine
Sheng-Huan Wang,Shih-Hsiung Chen 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.10
Ducted wind turbine with multiple blades installed was believed to have a good wind power energy conversion effect. However, little information was available on how to design a good ducted wind turbine. In this paper the effects of blade number on a ducted wind turbine performance is studied. Numerical studies using CFD method to simulate the wind turbine performance were adopted. The duct is a converging-diverging nozzle with the turbine blades located at the throat. A rated output of a 1-kW turbine is adopted as the baseline design. It was found that the blade geometry, stagger angle, and number of blades have different duct blockage effects, and do affect the turbine performance (specifically the power coefficient and torque coefficient, etc.). The fewer number of blades has higher through flow speed, while the larger number of blades provides larger torque. The best power coefficient lies in between the two extremes. The appropriate number of blades is important to match the generator performance curve for optimal overall performance and efficiency.
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A Study on Proper Location of Welding Defect in Three Point Bend Testing with MDPE Pipe
Lai, Huan Sheng,Yoon, Kee Bong,Kil, Seong Hee The Korean Society for Energy 2015 에너지공학 Vol.24 No.1
Welding defects affect the performance of welded pipe joints. In this study, a three point bend test of welded steel and medium density polyethylene (MDPE) pipe joints with defects of various defect locations and defect materials was studied using the finite element method. The defect was assumed to be located at 12 o'clock, 3 o'clock or 6 o'clock direction. The results showed that pipes failed more easily on the compression side due to stress or local buckling. The air defect was more dangerous than the steel defect if the defect was located in the compression side; otherwise, the defect material effect on the integrity of pipes was ignorable. It is argued that the integrity of pipes with defects in the compression side is weaker than that in other regions, and the defect should be located in the compression side or the 12 o'clock position in the three point bend test to maximize the effect of defect existence on the pipe structural integrity.
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Lai, Huan Sheng,Yoon, Kee Bong Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.153 No.-
<P><B>Abstract</B></P> <P>Functionally graded materials (FGMs) are increasingly being used in high-temperature structural components. The time-dependent <I>C</I>-integral, <I>C</I>(<I>t</I>), is a significant parameter in characterizing the crack tip stress field from the small-scale to the extensive steady-state creep stages. In this paper, the creep crack behavior of FGMs with a crack parallel to the material property gradients was studied by using the finite element method. It was proven that <I>C</I>(<I>t</I>) remained valid for FGMs. An engineering method was proposed to estimate <I>C</I>(<I>t</I>) in the small scale and transition creep stages and estimate the crack tip stress field. Finite element results verified that the method could estimate <I>C</I>(<I>t</I>) in the small scale and transition creep stages and estimate the crack tip stress field. For cases with creep properties that increased in the crack growth direction, the effect of constraint on the estimated crack tip stress field had to be considered. The constraint parameter of <I>Q</I> was significantly affected by the creep property gradients. The method was independent of the gradient variation law of material properties.</P>
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Huan-Yong Ji,Yong-Sheng Jin,Jing Li,Hui Tian,Shang-Zheng Feng 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.11
As market competition continuously intensifies, how to cope with existing and potential market challenges in complex, dynamic environments is a major problem haunting Chinese e-commerce enterprises in their strategic planning. In order to solve this problem, the theory of organizational ambidexterity is applied in this paper to the strategic practices of Chinese e-commerce enterprises, and starting from the view of corporate leadership, the mediated role of top management’s behavioral integration (referred to as TMBI in the following content) in the relationship between transformational leadership behavior and organizational ambidexterity is discussed. In addition, against the practical background that Chinese e-commerce enterprises are facing highly competitive environments, further clarification is made herein by using environmental dynamics as the moderator variable for the mediated link. Through empirical tests on 198 samples of Chinese e-commerce enterprises, we find that: 1) transformational leadership has a positive influence on organizational ambidexterity, and TMBI plays a full mediated role in that influencing process; 2) environmental dynamics moderates the relationship between transformational leadership and TMBI, but don’t have a moderated effect on the relationship between TMBI and organizational ambidexterity. According to the research conclusion in this paper, the mechanism of transformational leadership influencing organizational ambidexterity can be better explained when two important factors, TMBI and environmental dynamics, are taken into consideration. The research in this paper provides not only important revelations for the development of organizational ambidexterity research as well as the application of relevant research achievements, but also supports for Chinese e-commerce enterprises’ effective strategic practices in theory.
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Huan-Yong Ji,Jing Li,Chong-Feng Lan,Dan-Feng, Wang,Yong-Sheng Jin 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.5
Open Innovation gains a wide spread attention in technology management research in recent years. Because existing research about the relationship between outbound open innovation and innovation performance is limited and context factors are ignored in existing research and based on Chesbrough’s open innovation model and theory of enterprise competence, this study introduces enterprise competence and knowledge spillovers into the field of outbound open innovation, explores their moderated roles between open innovation and innovation performance. We use high-tech firms as research sample to test the hypothesis that we proposed and find that: (1) outbound open innovation has a positive effect on innovation performance; (2) both enterprise competence and knowledge spillovers moderate the relationship between outbound open innovation and innovation performance. These conclusions have important implications for the development and application of open innovation theory.
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Sheng-Cheng Yeh,Yih-Shyh Chiou,Huan Chang,Wang-Hsin Hsu,Shiau-Huang Liu,Fuan Tsai 한국통신학회 2016 Journal of communications and networks Vol.18 No.5
Providing a customer with tailored location-based ser-vices (LBSs) is a fundamental problem. For location-estimationtechniques with radio-based measurements, LBS applications arewidely available for mobile devices (MDs), such as smartphones,enabling users to run multi-task applications. LBS information notonly enables obtaining the current location of an MD but also pro-vides real-time push-pull communication service. For indoor envi-ronments, localization technologies based on radio frequency (RF)pattern-matching approaches are accurate and commonly used. However, to survey radio information for pattern-matching ap-proaches, a considerable amount of time and work is spent in in-door environments. Consequently, in order to reduce the system-deployment cost and computing complexity, this article proposesan indoor positioning approach, which involves using Asus Xtionto facilitate capturing RF signals during an offline site survey. Thedepth information obtained using Asus Xtion is utilized to estimatethe locations and predict the received signal strength (RF informa-tion) at uncertain locations. The proposed approach effectively re-duces not only the time and work costs but also the computing com-plexity involved in determining the orientation and RF during theonline positioning phase by estimating the user’s location by usinga smartphone. The experimental results demonstrated that morethan 78% of time was saved, and the number of samples acquiredusing the proposed method during the offline phase was twice asmuch as that acquired using the conventional method. For the on-line phase, the location estimates have error distances of less than2.67 m. Therefore, the proposed approach is beneficial for use invarious LBS applications.
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