Inhomogeneous bonding state modeling for vibration analysis of explosive clad pipe

Jianbin Cao,Zhousuo Zhang,Yanfei Guo,Teng Gong 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.3

Early detection of damage bonding state such as insufficient bonding strength and interface partial contact defect for the explosive clad pipe is crucial in order to avoid sudden failure and even catastrophic accidents. A generalized and efficient model of the explosive clad pipe can reveal the relationship between bonding state and vibration characteristics, and provide foundations and priory knowledge for bonding state detection by signal processing technique. In this paper, the slender explosive clad pipe is regarded as two parallel elastic beams continuously joined by an elastic layer, and the elastic layer is capable to describe the non-uniform bonding state. By taking the characteristic beam modal functions as the admissible functions, the Rayleigh-Ritz method is employed to derive the dynamic model which enables one to consider inhomogeneous system and any boundary conditions. Then, the proposed model is validated by both numerical results and experiment. Parametric studies are carried out to investigate the effects of bonding strength and the length of partial contact defect on the natural frequency and forced response of the explosive clad pipe. A potential method for identifying the bonding quality of the explosive clad pipe is also discussed in this paper.

Finite element analysis and mathematical characterization of contact pressure distribution in bolted joints

Jianbin Cao,Zhousuo Zhang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Quantitative characterization of contact pressure distribution in bolted joints directly influences the calculation accuracy of connection stiffness. In this paper, a three-dimensional finite element model of the bolted joints is established using the software ANSYS, and pretension force and contact between the joint components are accommodated in the model. Then, parametric studies are carried out to investigate the effects of the material properties, preloads, bolt sizes, grip lengths and hole clearances on the contact pressure distribution. According to the finite element analysis results, a polynomial equation system is derived for mathematical representation of contact pressure distribution in bolted joints. Furthermore, the conical envelope angle used in the mathematical characterization is identified for the bolted joints with different bolt sizes and grip lengths. Finally, an experimental platform is constructed for the measurement of contact pressure distribution, and then the applicability of mathematical characterization is validated by comparison with a series of experiment results.

Non uniform virtual material modeling on contact interface of assembly structure with bolted joints

Jianbin Cao,Zhousuo Zhang,Wenzhan Yang,Yanfei Guo 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.5

Accurate modeling of contact interface in bolted joints is crucial in predicting the dynamic behavior for bolted assemblies under external load. This paper presents a contact pressure distribution based non-uniform virtual material method to describe the joint interface of assembly structure, which is connected by sparsely distributed multi-bolts. Firstly, the contact pressure distribution of bolted joints is obtained by the nonlinear static analysis in the finite element software ANSYS. The contact surface around bolt hole is divided into several sub-layers, and contact pressure in each sub-layer is thought to be evenly. Then, considering multi-asperity contact at the micro perspective, the relationship between contact pressure and interfacial virtual material parameters for each sub-layer is established by using the fractal contact theory. Finally, an experimental platform for the dynamic characteristics testing of a beam lap structure with double-bolted joint is constructed to validate the efficiency of proposed method. It is found that the theoretical results are in good agreement with experimental results by impact response in both time- and frequency-domain, and the relative errors of the first four natural frequencies are less than 1%. Furthermore, the presented model is used to examine the effect of rough contact surface on dynamic characteristics of bolted joint.

Free vibration analysis of circular cylindrical shell on elastic foundation using the Rayleigh-Ritz method

Jinsong Yang,Jianbin Cao,Jingsong Xie,Haixiao Zhao 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.1

A general approach is presented for the free vibration analysis of circular cylindrical shell resting on elastic foundation and subjected to classical boundary conditions of any type. The Winkler/Pasternak model is utilized to simulate the elastic foundation imposed on the cylindrical shell, and then it is easily to derive the potential energy of the elastic foundation. Based on the Flügge shell theory, explicit expressions for the mass and stiffness matrices are obtained. By taking the characteristic beam modal functions as the admissible functions, the Rayleigh-Ritz method is employed to derive the frequency equations of circular cylindrical shell with all the classical boundary conditions and resting on elastic foundation. Once the frequency equation has been determined, the frequencies can be calculated numerically. The excellent accuracy and validity of the present approach are demonstrated by numerical examples and comparisons with the results available in the literature. Finally, some further numerical results are given to illustrate the comprehensive effect of geometric properties and foundation coefficients on the frequencies of circular cylindrical shell in contact with elastic foundation.

Enhanced dielectric and nonohmic properties of SrTiO3-modified CaCu3Ti4O12 ceramics

Zhao Jiangpeng,Sun Li,Cao Ensi,Hao Wentao,Zhang Yongjia,Chen Jianbin,Ju Lin 한국물리학회 2022 Current Applied Physics Vol.36 No.-

Dielectric and nonohmic properties of CaCu3Ti4O12 (CCTO) ceramics can be modified by addition of SrTiO3 (STO) in different molar proportions which were fabricated by a modified sol-gel method. XRD results indicated that all modified ceramics showed mixed phase consisting of both CCTO and STO. SEM images and grain size distribution probability also presented the change of microstructure with the addition of STO. The dielectric loss of the CCTO/0.4STO ceramics sintered at 1000 ◦C can be lower than 0.02 in a wide frequency (1 kHz–10 kHz), especially at 1 kHz, the dielectric loss of this sample is as low as 0.012. Furthermore, excellent nonlinear I–V electrical characteristic (high breakdown voltage to 54.15 kV/cm for CCTO/0.4STO sintered at 1000 ◦C) was observed as well. All the results indicated that the addition of STO does improve the dielectric properties and nonohmic characteristics of CCTO ceramics dramatically.

Early bolt looseness state identification via generalized variational mode decomposition and similarity index

Yanfei Guo,ZhouSuo Zhang,Wenzhan Yang,Jianbin Cao,Teng Gong 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3

A novel method for early looseness state identification of bolted joint beams is proposed in this paper based on generalized variational mode decomposition (GVMD) and a similarity index. In the proposed method vibration signals are decomposed by GVMD, which has the property of the multiscale and fixed-frequency decomposition. To effectively extract the desired modes, the frequency band allocation is designed through flexibly defining scale parameters and prior center frequencies according to the characteristics of the signal itself and real needs. A new similarity index is formed based on the centroid frequency ratio of sensitive vibration modes to reliably identify early looseness state. The effectiveness of the proposed method is verified by impulse experiments of bolted joint transverse beam and bolted joint vertical beam. The results indicate that compared with other methods, the proposed method can effectively identify the early looseness state of the bolted joint beams, and has a good repeatability.

Sparsity maximization nonlinear blind deconvolution and its application in identification of satellite microvibration sources

Teng Gong,ZhouSuo Zhang,Xin Luo,Jianbin Cao,Yanfei Guo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

In this study, sparsity maximization nonlinear blind deconvolution (NBD) is proposed to identify the vibration sources of satellite systems from mixed vibration signals. The proposed algorithm decomposes NBD into two independent stages, namely, nonlinear compensation and blind deconvolution. Since nonlinear distortion weakens the sparsity of the observed signals, sparsity maximization is introduced to the nonlinear compensation stage. In the blind deconvolution stage, the blind deconvolution algorithm with reference is used to separate the source signals. The proposed algorithm can improve the accuracy of source signal extraction from nonlinear mixed signals of complex mechanical systems. The effectiveness of the proposed method is verified through simulations. An experimental system of aluminum cabin structure is built based on the satellite’s cabin structure. Results show that the proposed algorithm can successfully realize the identification of source signals.

CXCL-13 Regulates Resistance to 5-Fluorouracil in Colorectal Cancer

Guolin Zhang,Xin Luo,Wei Zhang,Engeng Chen,Jianbin Xu,Fei Wang,Gaoyang Cao,Zhenyu Ju,Dongai Jin,Xuefeng Huang,Wei Zhou,Zhangfa Song 대한암학회 2020 Cancer Research and Treatment Vol.52 No.2

Purpose 5-Fluorouracil (5-Fu) is used as a conventional chemotherapy drug in chemotherapy for patients with advanced colorectal cancer, but many patients still suffer from treatment failure due to 5-Fu resistance. Emerging observations revealed the important role of chemokine (C-X-C motif) ligand 13 (CXCL-13) in tumor microenvironment and its relationship with prognosis in patients with colorectal cancer. This study is designed to reveal the important role of CXCL-13 in causing colorectal cancer resistance to 5-Fu. Materials and Methods CXCL-13 levels of patient's serum or cell culture supernatants were measured separately by enzyme-linked immunosorbent assay. In cell assays, cell viability is detected by Cell Counting Kit-8. Therefore, the recombinant human CXCL-13 was used to simulate its high expression in cells while its antibody and siRNA were used to reduce CXCL-13 expression in cells. Results In this study, we demonstrated that CXCL-13 is associated with 5-Fu resistance by culture medium exchange experiments and cytokine arrays of colorectal cancer resistant and nonresistant cells. Clinical studies showed that CXCL-13 is highly expressed in the serum of 5-Fu–resistant patients. High levels of serum CXCL-13 also predict a worse clinical outcome. The addition of recombinant CXCL-13 cytokine resulted in 5-Fu resistance, while its antibody overcame 5-Fu resistance, and knockdown of CXCL-13 expression by siRNA also reduced 5-Fu resistance, which can be saved by added recombination CXCL-13. Conclusion These results not only identify a CXCL-13 mediated 5-Fu resistance mechanism but also provide a novel target for 5-Fu–resistant colorectal cancer in prevention and treatment strategies.