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Stereo-digital image correlation in the behavior investigation of CFRP-steel composite members
Xiao-Yuan He,Yun-Tong Dai,Hai-Tao Wang,Tian-Yuan Ge,Gang Wu,Jian-Xiao Wan,Shuang-Yin Cao,Fu-Jun Yang 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.6
The application of carbon fiber reinforced polymer (CFRP) in steel structures primarily includes two categories, i.e., the bond-critical application and the contact-critical application. Debonding failure and buckling failure are the main failure modes for these two applications. Conventional electrometric techniques may not provide precise results because of the limitations associated with single-point contact measurements. A nondestructive full-field measurement technique is a valuable alternative to conventional methods. In this study, the digital image correlation (DIC) technique was adopted to investigate the bond behavior and buckling behavior of CFRP-steel composite members. The CFRP-to-steel bonded joint and the CFRPstrengthened square hollow section (SHS) steel column were tested to verify the suitability of the DIC technique. The stereo- DIC technique was utilized to measure continuous deformation. The bond-slip relationship of the CFRP-to-steel interface was derived using the DIC data. Additionally, a multi-camera DIC system consisting of four stereo-DIC subsystems was proposed and applied to the compressive test of CFRP-strengthened SHS steel column. The precise buckling location and CFRP delamination of the CFRP-strengthened SHS steel column were identified. The experimental results confirm that the stereo-DIC technique can provide effective measurements for investigating the behaviors of CFRP-steel composite members.
Study on mechanical behaviors of loose mortise-tenon joint with neighbouring gap
Jun-xiao He,Juan Wang,Qing-shan Yang,Miao Han,Yang Deng 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.4
The neighbouring gaps at the mortise-tenon joint in traditional timber structure, which leads to the complexity of the joint, are considered to impair the mechanical performance of the joint. In this paper, numerical simulation of loose joint was conducted to examine the deformation states, stress distributions, and bearing capacities, which was verified by full-scale test. On the basis of the experimental and numerical results, a simplified mechanics model with gaps has been proposed to present the bending capacity of the loose joint. Besides, the gap effects and parameter studies on the influences of tenon height, friction coefficient, elastic modulus and axial load were also investigated. As a result, the estimated relationship between moment and rotation angle of loose joint showed the agreement with the numerical results, demonstrating validity of the proposed model; The bending bearing capacity and rotational stiffness of loose joint had a certain drop with the increasing of gaps; and the tenon height may be the most important factor affecting the mechanical behaviors of the joint when it is subjected to repeated load; Research results can provide important references on the condition assessments of the existing mortise-tenon joint.
He, Xiao-Yu,Zhao, Tie-Wei,Li, Hong-Nan,Zhang, Jun Techno-Press 2016 Structural monitoring and maintenance Vol.3 No.2
Based on the change of traditional viscoelastic damper structure, a brand-new damper is designed to control simultaneously the translational vibration and the rotational vibration for platforms. Experimental study has been carried out on the mechanical properties of viscoelastic material and on its multi-dimensional seismic response control effect of viscoelastic damper. Three types of viscoelastic dampers with different shapes of viscoelastic material are designed to test the influence of excited frequency, strain amplitude and ambient temperature on the mechanical property parameters such as circular dissipation per unit, equivalent stiffness, loss factor and storage shear modulus. Then, shaking table tests are done on a group of single-storey platform systems containing one symmetric platform and three asymmetric platforms with different eccentric forms. Experimental results show that the simulation precision of the restoring force model is rather good for the shear deformation of viscoelastic damper and is also satisfied for the torsion deformation and combined deformations of viscoelastic damper. The shaking table tests have verified that the new-type viscoelastic damper is capable of mitigating the multi-dimensional seismic response of offshore platform.
Jun-yi Sun,Yang Rong,Xiao-ting He,Xiao-wei Gao,Zhou-lian Zheng 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.5
In this paper, the problem of axisymmetric deformation of the circular membrane fixed at its perimeter under the action of uniformly-distributed loads was resolved by exactly using power series method, and the solution of the problem was presented. An investigation into the so-called Hencky transformation was carried out, based on the solution presented here. The results obtained here indicate that the well-known Hencky solution is, without doubt, correct, but in the published papers the statement about its derivation is incorrect, and the so-called Hencky transformation is invalid and hence may not be extended to use as a general mathematical method.
review on the research of mechanical problems with different moduli in tension and compression
Jun-yi Sun,Hai-qiao Zhu,Shi-hong Qin,Da-lin Yang,Xiao-ting He 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.9
Most materials exhibit different tensile and compressive strains given the same stress applied in tension or compression. These materials are known as bimodular materials. An important model of bimodular materials is the criterion of positive-negative signs of principal stress proposed by Ambartsumyan. This model is mainly applicable to isotropic materials and deals with the principal stress state in a point. However, due to the inherent complexity of the constitutive relation, FEM based on iterative strategy and analytical methods based on a simplified mechanical model are required. In this paper, we review the basic assumptions of this model and its development, several innovative computational methods, and some important engineering applications. We also discuss the sequent key problems in this field.
Jun-Feng He,Jie Yan,Jiang-Shan Li,Jian-Hua Liu,Chao Wang,Xiao-Rong Chang,Ya-Ting Qu 사단법인약침학회 2013 Journal of Acupuncture & Meridian Studies Vol.6 No.2
The nucleus of the solitary tract (nucleus tractus solitarii; NTS) is a primary center for both visceral afferents and somatic afferents. Previous experiments have demonstrated that the NTS is closely connected to the stomach and acupoints in the Yangming Stomach Meridian of Foot (ST Meridian). In this study, extracellular recording and immunochemistry methods were used to analyze the discharge of neurons and c-Fos protein expression in the NTS following acupuncture at different acupoints and a nonacupoint. A total of 104 discharging neurons were detected in the NTS of 52 rats, of which 86 provided complete data. After acupuncture at Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint, the neuron response rate in the NTS was 65.12%, 51.16%, 46.51%, 34.88% and 31.40% respectively. For neuron response rate, there was a significant difference among Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint (p < 0.01 or p < 0.05). In the other 48 rats, the number of c-Fos immunoreactive neurons in the NTS by electroacupuncture (EA) at Sibai (ST 2) group was significantly higher than that EA at other acupoints and the nonacupoint (p < 0.05 or p < 0.01). EA at both Zusanli (ST 36) and Neiting (ST 44) increased c-Fos immunoreactive neurons significantly over EA at Quanliao (SI 18) and the nonacupoint (p < 0.05 or p < 0.01), while there was no difference between EA at Quanliao (SI 18) and the nonacupoint group (p > 0.05). The experiments demonstrated that the afferent convergence in NTS are different by body surface points stimulus, which suggests that the NTS might be a primary center in the central nervous system receiving acupoints stimulus from the ST Meridian.
Jun-yi Sun,Jian-li Hu,Zhou-lian Zheng,Xiao-ting He,Huan-huan Geng 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12
In this paper, based on the exact analytical solution of axisymmetric deformation of the circular membrane fixed at its edge under the action of uniformly-distributed loads, we propose a new method to be able to simultaneously determine Poisson's ratio and Young's modulus of elasticity for thin films. We also present a set of exact formulas used for simultaneously determining Poisson's ratio and Young's modulus of elasticity for free-standing thin films or coating thin films without residual stresses or pre-tension. This method has the advantages of simplicity and reliability, and it doesn’t involve the substrate effect.
SEDs and Beaming Effect for Fermi Blazars
Jun-Hui Fan,Jiang-He Yang,Yi Liu,Yu-Hai Yuan,Cao Lin,Hu-Bing Xiao 한국우주과학회 2016 Journal of Astronomy and Space Sciences Vol.33 No.2
In this work, based on our previous calculations of spectral energy distributions for a sample of Fermi blazars (Fan et al. 2015a), we calculated the radio loudness and performed correlation analyses. Our analysis results show that radio loudness is closely anti-correlated with synchrotron peak frequency and positively correlated with gamma-ray luminosity, suggesting that the gamma-ray emissions are strongly beamed.