Mean moment effect on circular thin-walled tubes under cyclic bending

Kao-Hua Chang,Wen-Fung Pan,Kuo-Long Lee 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.5

In this paper, experimental and theoretical investigations of the effect of the mean moment on the response and collapse of circular thin-walled tubes subjected to cyclic bending are discussed. To highlight the influence of the mean moment effect, three different moment ratios r (minimum moment/ maximum moment) of −1, −0.5 and 0, respectively, were experimentally investigated. It has been found that the moment-curvature loop gradually shrinks with the number of cycles, and becomes stable after a few cycles for symmetric cyclic bending (r = −1). However, the moment-curvature loop exhibits ratcheting and increases with the number of cycles for unsymmetric cyclic bending (r = −0.5 or 0). In addition, although the three groups of tested specimens had three different moment ratios, when plotted in a log-log scale, three parallel straight lines describe the relationship between the controlled moment range and the number of cycles necessary to produce buckling. Finally, the endochronic theory combined with the principle of virtual work was used to simulate the relationship among the moment, curvature and ovalization of thin-walled tubes under cyclic bending. An empirical formulation was proposed for simulating the relationship between the moment range and the number of cycles necessary to produce buckling for thin-walled tubes subjected to cyclic bending with different moment ratios. The results of the experimental investigation and the simulation are in good agreement with each other.

Viscoplastic response and collapse of 316L stainless steel tubes under cyclic bending

Kao-Hua Chang,Shane-Rong Sheu,Chien-Min Hsu,Wen-Fung Pan 국제구조공학회 2005 Steel and Composite Structures, An International J Vol.5 No.5

This paper presents the experimental and theoretical results of the viscoplastic response and collapse of 316L stainless steel tubes subjected to cyclic bending. The tube bending machine and curvatureovalization measurement apparatus, which was designed by Pan et al. (1998), were used for conducting the cyclic curvature-controlled experiment. Three different curvature-rates were controlled to highlight the characteristic of viscoplastic response and collapse. Next, the endochronic theory and the principle of virtual work were used to simulate the viscoplastic response of 316L stainless steel tubes under cyclic bending. In addition, a proposed theoretical formulation (Lee and Pan 2001) was used to simulate the relationship between the controlled cyclic curvature and the number of cycles to produce buckling under cyclic bending at different curvature-rates (viscoplastic collapse). It has been shown that the theoretical simulations of the response and collapse correlate well with the experimental data.

Mean moment effect on sharp-notched circular tubes under cyclic bending

Kao-Hua Chang,Kuo-Long Lee 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.9

This study discusses an experimental investigation of the effect of the mean moment on the response and collapse of sharp-notched circular tubes subjected to cyclic bending. To highlight the influence of the mean moment effect, five different moment ratios r (minimum moment / maximum moment) were experimentally investigated. We found that the moment-curvature loop gradually shrinks, and stabilizes after a few cycles for r = -1. However, the moment-curvature loop exhibits ratcheting and increases with the number of cycles for r ≠ -1. In addition, the ovalization-curvature curve shows unsymmetrical, ratcheting and increasing manner with the number of cycles for any r. Finally, the empirical formulation proposed by Chang et al. [1] was modified to simulate the relationship between the controlled moment range and the number of cycles necessary to produce buckling. The results of the experimental investigation and the simulation were in good agreement with each other.

Buckling failure of 310 stainless steel tubes with different diameter-to-thickness ratios under cyclic bending

Kao-Hua Chang,Kuo-Long Lee,Wen-Fung Pan 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.3

In this paper, experimental and theoretical investigations on the response and collapse of 310 stainless steel tubes with different diameter-to-thickness ratios subjected to cyclic bending are discussed. The tube-bending device and curvature-ovalization measurement apparatus were used to conduct the experiment. The endochronic theory combined with the principle of virtual work and finite element software, ANSYS, were used to simulate the moment-curvature and ovalization-curvature relationships. It is shown that although the two methods lead to good simulation of the moment-curvature relationship, the endochronic theory combined with the principle of virtual work has the better simulation of the ovalization-curvature response when compared with experimental data and the simulation by ANSYS. In addition, the theoretical formulations proposed by Kyriakides and Shaw (1987) and Lee et al. (2001) were used to simulate the controlled curvature뻨umber of cycles to produce buckling relationship. It is shown that the theoretical formulations effectively simulate the experimental data.

원조여 (元朝與) 고려적 (高麗的) 해상교통

진고화 ( Kao Hua Chen ) 진단학회 1991 진단학보 Vol.- No.71-72

Mean moment effect on circular thin-walled tubes under cyclic bending

Chang, Kao-Hua,Pan, Wen-Fung,Lee, Kuo-Long Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.5

In this paper, experimental and theoretical investigations of the effect of the mean moment on the response and collapse of circular thin-walled tubes subjected to cyclic bending are discussed. To highlight the influence of the mean moment effect, three different moment ratios r (minimum moment/ maximum moment) of -1, -0.5 and 0, respectively, were experimentally investigated. It has been found that the moment-curvature loop gradually shrinks with the number of cycles, and becomes stable after a few cycles for symmetric cyclic bending (r = -1). However, the moment-curvature loop exhibits ratcheting and increases with the number of cycles for unsymmetric cyclic bending (r = -0.5 or 0). In addition, although the three groups of tested specimens had three different moment ratios, when plotted in a log-log scale, three parallel straight lines describe the relationship between the controlled moment range and the number of cycles necessary to produce buckling. Finally, the endochronic theory combined with the principle of virtual work was used to simulate the relationship among the moment, curvature and ovalization of thin-walled tubes under cyclic bending. An empirical formulation was proposed for simulating the relationship between the moment range and the number of cycles necessary to produce buckling for thin-walled tubes subjected to cyclic bending with different moment ratios. The results of the experimental investigation and the simulation are in good agreement with each other.

Acute hepatitis C virus infection: clinical update and remaining challenges

Chen-Hua Liu,Jia-Horng Kao 대한간학회 2023 Clinical and Molecular Hepatology(대한간학회지) Vol.29 No.3

Acute hepatitis C virus (HCV) infection is a global health concern with substantial geographical variation in the incidence rate. People who have received unsafe medical procedures, used injection drugs, and lived with human immunodeficiency virus are reported to be most susceptible to acute HCV infection. The diagnosis of acute HCV infection is particularly challenging in immunocompromised, reinfected, and superinfected patients due to difficulty in detecting anti-HCV antibody seroconversion and HCV ribonucleic acid from a previously negative antibody response. With an excellent treatment effect on chronic HCV infection, recently, clinical trials investigating the benefit of direct-acting antivirals (DAAs) treatment for acute HCV infection have been conducted. Based on the results of cost-effectiveness analysis, DAAs should be initiated early in acute HCV infection prior to spontaneous viral clearance. Compared to the standard 8–12 week-course of DAAs for chronic HCV infection, DAAs treatment duration may be shortened to 6–8 weeks in acute HCV infection without compromising the efficacy. Standard DAA regimens provide comparable efficacy in treating HCV-reinfected patients and DAA-naïve ones. For cases contracting acute HCV infection from HCV-viremic liver transplant, a 12-week course of pangenotypic DAAs is suggested. While for cases contracting acute HCV infection from HCV-viremic non-liver solid organ transplants, a short course of prophylactic or pre-emptive DAAs is suggested. Currently, prophylactic HCV vaccines are unavailable. In addition to treatment scale-up for acute HCV infection, practice of universal precaution, harm reduction, safe sex, and vigilant surveillance after viral clearance remain critical in reducing HCV transmission.

Intelligent Management System: Deep Convolutional Neural Networks for Automatic Attribute Recognition in IP Surveillance Networks

Chien-Chi Kao,Yung-Chang Lai,Jung Pei,Chih-Wei Chang,Fei-Hua Kuo,Jin-Yuan Shun 한국통신학회 2020 한국통신학회 APNOMS Vol.2020 No.09

In recent years, IP surveillance networks are expected to enable various practical applications, such as finding suspects, monitoring pedestrians, and securing societies (e.g., securing a city, a company and a data center). With these applications, IP surveillance network is regarded as one of the potential technologies toward developing smart cities. To support the concept of IP surveillance networks, automatic attribute recognition systems have emerged as a promising intelligent management system. To automatically recognize attributes of pedestrians (e.g., gender and clothing), we apply deep convolutional neural networks (CNNs), and the main contributions of this paper are threefold: (1) we proposed a practical system architecture for intelligent management of surveillance networks; (2) we implemented different deep CNNs, and an ensemble-learning method that leverages these multiple deep-learning models; (3) we evaluated the models using the real data of IP surveillance networks.

Fabrication of GaInP/GaAs on poly-Si triple-junction solar cells by mechanical stacking technology

Yu-Cheng KAO,Ching-Ho TIEN,Sha-Hui SHI,Ray-Hua HORNG 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Failure life estimation of sharp-notched circular tubes with different notch depths under cyclic bending

Kuo-Long Lee,Kao-Hua Chang,Wen-Fung Pan 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.3

In this paper, the response and failure of sharp-notched 6061-T6 aluminum alloy circular tubes with five different notch depths of 0.4, 0.8, 1.2, 1.6 and 2.0 mm subjected to cyclic bending were experimentally and theoretically investigated. The experimental moment-curvature relationship exhibits an almost steady loop from the beginning of the first cycle. And, the notch depth has almost no influence on its relationship. However, the ovalization-curvature relationship exhibits a symmetrical, increasing, and ratcheting behavior as the number of cycles increases. In addition, a higher notch depth of a tube leads to a more severe unsymmetrical trend of the ovalization-curvature relationship. Focusing on the aforementioned relationships, the finite element software ANSYS was used to continue the related theoretical simulation. Furthermore, the five groups of tubes tested have different notch depths, from which five unparallel straight lines can be observed from the relationship between the controlled curvature and the number of cycles required to produce failure in the log-log scale. Finally, a failure model was proposed to simulate the aforementioned relationship. Through comparison with the experimental data, the proposed model can properly simulate the experimental data.