Bending and free vibration analysis of laminated piezoelectric composite plates

Pengchong Zhang,Chengzhi Qi,Hongyuan Fang,Xu Sun 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.6

This paper provides a semi-analytical approach to investigate the variations of 3D displacement components, electric potential, stresses, electric displacements and transverse vibration frequencies in laminated piezoelectric composite plates based on the scaled boundary finite element method (SBFEM) and the precise integration algorithm (PIA). The proposed approach can analyze the static and dynamic responses of multilayered piezoelectric plates with any number of laminae, various geometrical shapes, boundary conditions, thickness-to-length ratios and stacking sequences. Only a longitudinal surface of the plate is discretized into 2D elements, which helps to improve the computational efficiency. Comparing with plate theories and other numerical methods, only three displacement components and the electric potential are set as the basic unknown variables and can be represented analytically through the transverse direction. The whole derivation is built upon the three dimensional key equations of elasticity for the piezoelectric materials and no assumptions on the plate kinematics have been taken. By virtue of the equilibrium equations, the constitutive relations and the introduced set of scaled boundary coordinates, three-dimensional governing partial differential equations are converted into the second order ordinary differential matrix equation. Furthermore, aided by the introduced internal nodal force, a first order ordinary differential equation is obtained with its general solution in the form of a matrix exponent. To further improve the accuracy of the matrix exponent in the SBFEM, the PIA is employed to make sure any desired accuracy of the mechanical and electric variables. By virtue of the kinetic energy technique, the global mass matrix of the composite plates constituted by piezoelectric laminae is constructed for the first time based on the SBFEM. Finally, comparisons with the exact solutions and available results are made to confirm the accuracy and effectiveness of the developed methodology. What’s more, the effect of boundary conditions, thickness-to-length ratios and stacking sequences of laminae on the distributions of natural frequencies, mechanical and electric fields in laminated piezoelectric composite plates is evaluated.

A Study on the Creeping Failure related to Crack Inclination of Brittle Rocks

Xiaozhao Li,Chengzhi Qi,Zhushan Shao 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1

A new micro-macro modelling approach is presented for predicting the creeping failure behaviors in brittle rocks. Effect of crack inclination angle is especially considered in this approach. This method is formulated by the combination of an improved stress intensity factor, a time- dependent cracking law, and a correlation of crack extension and axial strain. This improved stress intensity factor is derived by drawing crack inclination effect into Ashby and Sammis’ wing crack model. This correlation of crack extension and axial strain is established by coupling the expressions of micro-damage with macro-damage. The analytical stress- strain relation and creep equation considering crack inclination effect are derived. Furthermore, crack inclination φ, crack size a, crack friction coefficient μ, and parameter β are predicted by using the experimental data of crack initiation stress related to confining pressure, which provides a novel method in applying the proposed micro-macro model to natural rock. Influences of confining pressure on creep behaviors subjected to step axial loading and quasi-static behaviors are analyzed. The creep and quasi-static failure properties related to crack inclination are also discussed. Rationality of this proposed micro-macro approach is validated by comparing with experimental results.

Radian of the vault influencing the seismic performances of straight wall arch underground structures

Chao Ma,Dechun Lu,Chengzhi Qi,Xiuli Du 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.5

Great efforts have been conducted to investigate the seismic performances of the arch and rectangular underground structures, however, the differences between seismic responses of these two types of underground structures, especially the vault radian influencing the seismic responses of arch structures are not clarified. This paper presents a detailed numerical investigation on the seismic responses of arch underground structures with different vault radians, and aims to illustrate the rule that vault radian affects the seismic responses of underground structures. Five arch underground structures are built for nonlinear soil-structure interaction analysis. The internal forces of the structural components of the underground structures only under gravity are discussed detailedly, and an optimum vault radian for perfect load-carrying functionality of arch underground structures is suggested. Then the structures are analyzed under seven scaled ground motions, amounting to a total of 35 dynamic calculations. The numerical results show that the vault radian can have beneficial effects on the seismic response of the arch structure, compared to the rectangular underground structures, causing the central columns to suffer smaller axial force and horizontal deformation. The conclusions provide some directive suggestions for the seismic design of the arch underground structures.

LncRNA SNHG12/miR-494-3p/CBX3 axis in diffuse large B-cell lymphoma

Si Cheng,Zhang Wanyong,Han Qi,Zhu Bisheng,Zhan Chengzhi 대한독성 유전단백체 학회 2023 Molecular & cellular toxicology Vol.19 No.1

Background Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoid malignancy in adults. Current studies have implicated that long non-coding RNAs (lncRNAs) regulate the development of DLBCL; nevertheless, the control method is dim. Here, we reconnoitered the characters of lncRNA small nucleolar RNA host gene 12 (lncRNA SNHG12) in DLBCL. Objective The pathological morphology of tumor tissues and normal tissues was perceived by hematoxylin–eosin (HE) staining. The levels of SNHG12, microRNA-494-3p (miR-494-3p), and chromobox 3 (CBX3) were detected by quantitative real-time PCR and western blot. Whereafter, MTT assay and EdU assay were enforced to validate cell proliferation. Flow cytometry assay was implemented to assess the cell cycle and cell apoptosis, respectively. Additionally, the interface between miR-494-3p with SNHG12 or CBX3 was identified by dual-luciferase reporter assay. Results SNHG12 and CBX3 were enhanced, but miR-494-3p was diminished in DLBCL. Knockdown of SNHG12 repressed cell proliferation and cell cycle, although heightened cell apoptosis in DLBCL cells. SNHG12 sponged miR-494-3p to adjust the CBX3. Additionally, miR-494-3p restrained DLBCL cells development by targeting CBX3. Conclusion SNHG12 contributed to DLBCL development by regulating miR-494-3p/CBX3. The outcomes demonstrated that SNHG12 provided a potential train of thought for DLBCL theory of targeted therapy.

A Meso-Macro Method of Evaluating Water Content Effect on Direct Tensile Fracture in Brittle Rocks

Xiaozhao Li,Xing Che,Haifeng Li,Chengzhi Qi 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

Tensile stress is one of the primary forms of loading triggering the fracture in brittle rocks. Water content strongly affects the fracture process induced by meso-crack extension under the direct tensile loading of brittle rocks. Due to limitation of current equipments, the experiment of direct tensile fracture considering water content effect of brittle rocks is hardly implemented. Furthermore, the meso-macro model simultaneously considering the influence of water content and tensile loading on fracture behaviours of brittle rocks is also rarely studied. This paper proposes a meso-macro mechanical model to evaluate the water content effect on the fracture process under direct tensile loading of brittle rocks. This model is developed by combining the suggested model of meso-crack extension under direct tensile loading, the correlation of macroscopic strain and meso-crack extension, and considering the effect of water content on fracture toughness KIC and initial damage D0. This meso-macro model is linking the development process of meso-crack initiation, extension and coalescence to macroscopic fracture. The axial stress-strain curves during progressive tensile fracture under different water contents were studied, and the rationality of the suggested theoretical model was validated by the test results. The influences of water content on the relation between wing crack length and axial stress, the relation between wing crack length and stress intensity factor KI, crack initiation stress, peak stress, and elastic modulus were analyzed. The influences of the model parameter  and the initial crack angle  on the peak stress and crack initiation stress under the different water contents are also discussed.